4 Character reconstructions
This page provides definitions for each of the characters in our matrix, and justifies codings in particular taxa where relevant. Further citations for codings that are not discussed in the text can be viewed by browsing the morphological dataset on MorphoBank (project 3262).
Alongside its definition, each character has been mapped onto a tree. Any of the optimal trees can be selected by modifying the tree number listed above each diagram. Each tip is labelled according to its coding in the matrix. These states have been used to reconstruct the condition of each internal node, using the parsimony method of Brazeau et al. (2019) as implemented in the R package Inapp (Guillerme, Brazeau, & Smith, 2018).
We emphasize that different trees give different reconstructions. The character mappings are not intended to definitively establish how each character evolved, but to help the reader quickly establish how each character has been coded, and to visualize at a glance how each character fits onto a given tree. Click here to hide the character reconstructions below.
4.1 Brephic shell
[1] Embryonic shell
Character 1: Brephic shell: Embryonic shell
The embryonic shell or protegulum is secreted by the embryo immediately before hatching. Corresponds to character 12 in Vinther, Parry, Briggs, & Van Roy (2017).
This shell field is initially disc-like, subsequently expanding to fuse ventrally and produce the cylindrical protoconch. The prototroch is clearly delineated fro the telotroch in post-metamorphic juveniles (Wanninger & Carlson, 2001).
Tonicella: On hatching, the polyplacophoran larva lacks a shell field.
Shell fields develop during the trochophore larva stage. The larva of the chiton Mopalia has two distinct shell fields: that anterior to the prototroch will develop into the first shell plate; the one posterior to the prototroch becomes the subsequent plates (Wanninger & Haszprunar, 2002a).
This disc-shaped posterior plate, whose position corresponds to the conchiferan shell field, bears a polygonal ornament and is subdivided by a series of grooves that prefigure the adult shell plates (Wanninger & Haszprunar, 2002a).[2] Morphology
Character 2: Brephic shell: Morphology
The brephic shell is the shell possessed by the young organism (see Ushatinskaya & Korovnikov (2016) and Popov, Bassett, Holmer, Skovsted, & Zuykov (2010) for discussion of terminology).
Micrina resembles linguliforms (Holmer, Skovsted, Larsson, Brock, & Zhang (2011)): in both, the brephic mitral shell has one pair of setal sacs enclosed by lateral lobes, whereas the brephic ventral shell has two lateral setal tubes.
Paterimitra and Salanygolina have “identical” ventral brephic shells (Holmer et al. (2011)), resembling the shape of a ship’s propeller.
Haplophrentis is coded following typical hyoliths, which have a spherical brephic shell; Pedunculotheca’s, in contrast, is seemingly cap-shaped.
[3] Embryonic shell extended in larvae
Character 3: Brephic shell: Embryonic shell extended in larvae
Many taxa add to their embryonic shell (the protegulum possessed by the embryo upon hatching) during the larval phase of their life cycle. The shell that exists at metamorphosis, marked by a halo or nick point, is variously termed the “first formed shell”, “metamorphic shell” or “larval shell” (Bassett & Popov 2017).
[4] Surface ornament
Character 4: Brephic shell: Surface ornament
Pitting of the larval shell characterises acrotretids and their relatives. Pustules occur on Paterinidae. See Character 3 in Williams et al. (2000), tables 5–6.
[5] Larval attachment structure
Character 5: Brephic shell: Larval attachment structure
Embryonic shells of Micrina and certain linguliforms exhibit a transversely folded posterior extension that speaks of the original presence of a pedicle in the embryo.
This is independent of the presence of an adult pedicle, which may arise after metamorphosis.
[6] Setulose
Character 6: Brephic shell: Setulose
The protegulum of Micrina is penetrated with canals that were originally associated with setae, a character that it has in common with linguliforms (Holmer et al. 2011).
[7] Setal sacs
Character 7: Brephic shell: Setal sacs
Setal sacs are recognizable as raised lumps on the juvenile shell (see Bassett & Popov, 2017).
Micrina and linguliforms have setal sacs on their mitral/dorsal embryonic shell, whereas these are absent in Paterimitra (Holmer et al., 2011).
[8] Number
Character 8: Brephic shell: Setal sacs: Number
Two pairs on e.g. Coolina; one on e.g. Micrina.
4.2 Larval setae: Paired bundles [9]
Character 9: Larval setae: Paired bundles
Annelid chaetae are equivalent to the bundled setae expressed in certain brachiopod larvae. See character 12 in Vinther, Van Roy, & Briggs (2008).
4.3 Adult setae [10]
Character 10: Adult setae
Lüter (2000) demonstrates that the setae of larval and adult brachiopods exhibit fundamental structural differences and are conceivably not homologous structures. Larval setae are thus described separately.
Although preservation of setae in fossil brachiopods is exceptional, their presence can be inferred from shelly material (see Holmer et al. (2006)).
The girdle elements of aculiferan molluscs include chitinous material that is secreted by microvilli; following Vinther et al. (2017), these are coded as potential homologues of setae.
shells of which are also cemented).” – Williams et al. 2007.
Orthrozanclus: The sclerites of Orthrozanclus are interpreted as being homologous to those of Halkieria.
Orthrozanclus occurs in preservational regimes that preserve sclerites in annelids and Wiwaxia, so additional seta-like sclerites – whose presence cannot be evaluated in Halkieria – are taken to be genuinely absent.Polysacos vickersianum: The spinose sclerites of multiplacophorans are generally considered to represent modified shell plates rather than girdle elements (Vendrasco et al., 2004, @ConwayMorris2006).
Vinther (2009) argues that the spines of Polysacos are homologous with polyplacophoran girdle elements.
However, aesthete canals form by the inclusion of the secretory mantle within the growing valve (Baxter, Jones, & Sturrock, 1987), which points to a fundamentally non-seta-like growth mechanism; rather than secretion by basal microvilli, multiplacophoran spines evidently grow by basal accretion without periodic replacement.
As such, the existence of girdle elements homologous to setae is not demonstrated by available fossil material.Siphogonuchites multa: The nature of the spicules that constitute the Siphogonuchites shell is uncertain. We treat them here as homologous to chiton girdle elements, following Conway Morris & Chapman (1996), Bengtson (1992) and Vinther et al. (2017).
An equivalence to halkieriid sclerites is not apparent: sclerites must have been added to the edge of the Siphogonuchitid shell during growth, requiring an increase in the number of sclerite ‘rows’; and they do not follow a quincuncial arrangement in a straightforward manner.
The internal ornament of parallel lines (Bengtson, 1992; Conway Morris & Chapman, 1996) recalls the longitudinal chambers within microvillar-secreted setae, but occur on the inner surface of phosphatized chambers, so probably have a different origin.Tonicella: The girdle elements of certain polyplacophorans are chitinous and secreted by microvilli (Fischer, Maile, & Renner, 1980; Leise, 1988; Leise & Cloney, 1982); it is therefore likely that they are homologous with the setae of other lophotrochozoans.
They are not homologous with the shell; they exhibit a distinct mode of secretion and have a different organic scaffold (Treves, Traub, Weiner, & Addadi, 2003, @Ehrlich2010).[11] Secretion
Character 11: Adult setae: Secretion
The majority of lophotrochozoan sclerites bear a characteristic striated texture that denotes their secretion by basal microvilli (Butterfield, 1990). The seta-like hooks of sipunculans lack this texture, suggesting that they may not be homologous with other setae.
[12] Microvillar diameter
Character 12: Adult setae: Secretion: Microvillar diameter
The diameter of secretory microvilli may vary across the diameter of a seta (Smith, 2014).
[13] Microvillar canal aspect
Character 13: Adult setae: Secretion: Microvillar canal aspect
Lüter (2000) distinguishes between the polygonal outline of microvillar canals in adult brachiopod setae and the oval outline of larval setae.
[14] Organic constituent
Character 14: Adult setae: Composition: Organic constituent
The majority of lophotrochozoan sclerites are chitinous, occasionally hosting secondary biominerals.
[15] Enamel
Character 15: Adult setae: Composition: Enamel
Certain setae are encapsulated in a 20 nm wide electron dense layer, termed “enamel” by Gustus & Cloney (1973). Enamel may be absent in larval setae (Lüter, 2003); this character refers to the condition in adult setae.
[16] Mineralized core
Character 16: Adult setae: Composition: Mineralized core
Per character 4 in Vinther et al. (2017), the sclerites and spicules of many aculiferans have a calcareous core.
[17] Distribution
Character 17: Adult setae: Distribution
Setae penetrate the valves of many brachiopods. In certain taxa, they are apparent only at the margins of the valves, in association with the commissure, being reduced or lost over the surface of the shell.
The ‘fascicles’ of Vinther et al. (2017) are a specific case of the ‘bundles’ described here.
[18] Present on anteriormost segment
Character 18: Adult setae: Distribution: Present on anteriormost segment
This character attempts to reflect character 115 in Parry, Edgecombe, Eibye-Jacobsen, & Vinther (2016), as modified by Nanglu & Caron (2018). This character seeks to capture the fact that both Canadia and Phragmochaeta are interpreted as bearing chaetal bundles on their anterior segments (Parry, Vinther, & Edgecombe, 2015). Wiwaxia does too.
I treat the character as transformational, coding it as inapplicable where trunk chaetae or parapodia are absent, as it is not possible to independently verify the ancestral state of this character.
[19] Internal constitution
Character 19: Adult setae: Internal constitution
Sipunculan “setae” are basally invaginated, suggesting that they may not be homologous with annelid chaetae. Certain aculiferans also exhibit basally hollow sclerites (Vinther et al., 2017, character 6).
[20] Distinct shaft
Character 20: Adult setae: Distinct shaft
The setae of certain taxa (e.g. Wiwaxia, Mopalia) have a differentiated shaft that inserts into the body wall.
[21] Hooks
Character 21: Adult setae: Hooks
Hooked chaetae arise through the reorientation of the chaetoblast during secretion (Hausen, 2005). Rouse & Fauchald (1997) and Parry et al. (2016) distinguish falcate (sickle-shaped) hooks (characters 121 and 98 respectively), dentate hooks (characters 122 and 92) and uncini (characters 123 and 94) as fundamentally different types of chaetae. A dentate hook, however, can be seen as a falcate hook with additional adrostral teeth or processes (Tilic, Bartolomaeus, & Rouse, 2016). We therefore code simply for the presence of apical curvature in any chaetae, with a view that a gain of a ‘hook’ represents an evolutionary novelty that might then be expressed in various locations and complemented by the addition of subsidiary dentition (i.e. adrostral hooks).
[22] Capitium
Character 22: Adult setae: Capitium
Character 81 in Capa et al. (2011). The capitium is a region on the convex surface of the rostrum (if present) that contains containing multiple teeth, each secreted by an individual microvillus (Bartolomaeus, 2002; Hausen, 2005; Holthe, 1986), and in a consistent orientation with the margin of the chaeta.
[23] Projecting knobs
Character 23: Adult setae: Projecting knobs
Terebratulids and discinids instead exhibit knob-like individual spines. These are distinct from the rings of spines that fringe lingulid setae.
Note that the “embryonic” setae of Discinids correspond to the “larval setae” of other brachiopods, and the “larval setae” of juvenile discinids correspond to adult setae (Lüter, 2003).
[24] Circling coronae
Character 24: Adult setae: Circling coronae
Lingulid setae bear crown-like rings of fine spines delimiting vertical sections, recalling the nodes of Equisetum stems. These arise by the addition of an additional circlet of microvilli (see Lüter, 2000, fig. 1e).
4.4 Body organization
[25] Serial repetition
Character 25: Body organization: Serial repetition
Serial repetition in adult, whether expressed in valves, soft tissues or exoskeletal elements. See character 13 in Rouse (1999); 19 in Vinther et al. (2008); 38 in Haszprunar (1996); 40–41 in Sutton & Sigwart (2012); Wanninger (2009).
[26] Annulae
Character 26: Body organization: Annulae
The trunk of Sipunculus and many annelid worms bear annulations.
[27] Subdivided head
Character 27: Body organization: Subdivided head
The annelid head comprises a differentiated prostomium and peristomium. See character 119 in Parry & Caron (2019).
[28] Pedal groove
Character 28: Body organization: Pedal groove
Certain aculiferans have secondarily lost a foot, but retain a pedal groove.
[29] Foot
Character 29: Body organization: Pedal groove: Foot
See characters 8 in Haszprunar (1996); 4 in Vinther et al. (2008); 137 in Rouse (1999); 21 in Buckland-Nicks (2008); 37 in Sutton & Sigwart (2012); 1, 3 and 4 in Haszprunar & Wanninger (2008).
It is assumed that the adult foot is homologous with (and thus contingent on) the larval foot.
[30] Coelom
Character 30: Body organization: Coelom
[31] Number
Character 31: Body organization: Coelomoducts: Number
Character 27 in Haszprunar (2000). Coelomoducts are excretory organs derived from the coelom, also in some cases serving as genital ducts (gonoducts); they replace (and may resemble) nephridia (Goodrich, 1945).
[32] Gills
Character 32: Body organization: Gills
Gills (or ctenidia) surround the molluscan foot.
Characters 1.59–60, 2.09, 4.49 in von Salvini-Plawen & Steiner (1996); 10–11 in Haszprunar (2000); 45 in Sutton & Sigwart (2012).
[33] Ctenidia
Character 33: Body organization: Gills: Ctenidia
4.5 Pedicle
[35] Presence
Character 35: Pedicle: Presence
The brachiopod pedicle is a fleshy protuberance that emerges from the posterior part of the body wall – as denoted in fossil taxa by its occurrence between the dorsal and ventral valves.
It is important to distinguish the pedicle from the “pedicle sheath”, a tubular extension of the umbo that grows by accretion from an isolated portion of the ventral mantle. For discussion see Holmer et al. (2018) and Bassett & Popov (2017).
the soft seafloor, like most other Chengjiang brachiopods.” …
“The putative pedicle illustrated by Chen et al. (2007: Figs 4, 6, 7) in fact is the mold of a three-dimensionally preserved visceral cavity” – Zhang et al. 2009.
[36] Constitution
Character 36: Pedicle: Constitution
The pedicle of certain chengjiang rhynchonelliforms comprises “densely stacked, three dimensionally preserved, tabular discs” (Holmer, Popov, et al. (2018)).
This contrasts with the uniform (‘massive’) pedicles of living taxa.
[37] Biomineralization
Character 37: Pedicle: Biomineralization
[38] Bulb
Character 38: Pedicle: Bulb
A bulb is an expanded region of the distal pedicle, often embedded into the sediment to improve anchorage.
[39] Distal rootlets
Character 39: Pedicle: Distal rootlets
Observed in Pedunculotheca and Bethia (Sutton, Briggs, Siveter, & Siveter, 2005).
[40] Tapering
Character 40: Pedicle: Tapering
Holmer et al. (2018) remark that the tapering aspect of the Nisusia pedicle recalls that of certain Chengjiang taxa (Alisina, Longtancunella) whilst distinguishing it from many other taxa (Eichwaldia, Bethia) in which the pedicle is a constant thickness.
[41] Coelomic region
Character 41: Pedicle: Coelomic region
Certain brachiopods, such as Acanthotretella, exhibit a coelomic cavity within the pedicle or pedicle sheath.
Treated as transformational as it is not clear that either state is necessarily ancestral.
[42] Surface ornament
Character 42: Pedicle: Surface ornament
Annulations are regular rings that surround the pedicle, and are distinguished from wrinkles, which are irregular in magnitude and spacing, and may branch or fail to entirely encircle the pedicle.
[43] Nerve impression
Character 43: Pedicle: Nerve impression
In certain taxa the impression of the pedicle nerve is evident in the shell. See character 28 in Williams et al. (1998b) appendix 1. Care must be taken not to code an impression as absent when the preservational quality is insufficient to safely infer a genuine absence. Treated as neomorphic as the presence of an innervation is considered a derived state.
4.6 Mantle cavity
[44] Presence
Character 44: Mantle cavity: Presence
Character 8 in Haszprunar (2000).
[46] Open face
Character 46: Mantle cavity: Open face
The mantle cavity (pallial cavity) has an open face in polyplacophorans, but forms a blind sac in taxa such as gastropods. See Simone (2009).
[47] Sac opening
Character 47: Mantle cavity: Sac opening
Caudofoveate and solenogaster aplacophorans can be distinguished based on the direction that their mantle cavity opens (Sutton et al., 2012).
4.7 Mantle canals
[49] Presence
Character 49: Mantle canals: Presence
Whether impressed on a shell or expressed solely in soft tissue.
[50] Morphology
Character 50: Mantle canals: Morphology
The morphology of dorsal and ventral canals is identical in all included taxa, so is assumed not to be independent – hence the use of a single character (contra Williams et al., 2000).
For a description of terms see Williams, James, et al. (1997b);Williams et al. (2000).
Pinnate = “rapidly branch into a number of subequal, radially disposed canals”
Bifurcate = “vascula lateralia in both valves divide immediately after leaving the body cavity”
Baculate = “extend forward without any major dichotomy or bifurcation” (Williams, James, et al., 1997b, p. 418)
Saccate = “pouchlike sinuses lying wholly posterior to the arcuate vascula media” (ibid., p412).
[51] vascula lateralia
Character 51: Mantle canals: vascula lateralia
We treat the vascula lateralia as equivalent to the vascula genitalia of articulated brachiopods, allowing phylogenetic analysis to test their proposed homology.
Williams, James, et al. (1997b) write: “The mantle canal system of most of the organophosphate-shelled species consists of a single pair of main trunks in the ventral mantle (vascula lateralia) and two pairs in the dorsal mantle, one pair (vascula lateralia) occupying a similar position to the single pair in the ventral mantle and a second pair projecting from the body cavity near the midline of the valve. This latter pair may be termed the vascula media, but whether they are strictly homologous with the vascula media of articulated brachiopods is a matter of opinion. It is also impossible to assert that the vascula lateralia are the homologues of the vascula myaria or genitalia of articulated species, although they are likely to be so as they arise in a comparable position.”
“In inarticulated brachiopods, two main mantle canals (vascula lateralia) emerge from the main body cavity through muscular valves and bifurcate distally to produce an increasingly dense array of blindly ending branches near the periphery of the mantle (fig. 71.1–71.2).”
[52] vascula media
Character 52: Mantle canals: vascula media
Williams, James, et al. (1997b) note that in addition to the vascula lateralia, “Discinisca has two additional mantle canals emanating from the body cavity into the dorsal mantle (vascula media).”
These structures are only evident in the dorsal valve for the included taxa, so only a single character is necessary.
But in contrast, Williams et al. 2007, p. 2875, identify the dorsal valve’s canals as a vascula media in living cranidds (though both are lateralia in Ordoviian craniides). This character is therefore coded as ambiguous.
[53] vascula terminalia
Character 53: Mantle canals: vascula terminalia
Presumed to be connected with setal follicles in life Williams et al. (1998b). See Williams et al. (2000) for discussion.
4.8 Perioral apparatus
[54] Presence
Character 54: Perioral apparatus: Presence
The lophophore is a ring of tentacles that surrounds the mouth. (???) suggests that true lophophores must also encompass the anus, which excludes the tentacular apparatus of entoprocts from the definition; as homology between the tentacular apparatuses of entoprocts and other lophophorates has often been assumed, we prefer to take a more inclusive stance and code the structures as potentially homologous.
Tentacles also surround the mouth in certain sipunculans. On the basis of their position and innervation, the perioral tentacles of sipunculans (character 171 in Parry et al. (2016) and 1 in Schulze, Cutler, & Giribet (2007)) are treated as potential homologs of palps in annelids. Palps exhibit a broad diversity of morphologies, but can be identified based on their innervation (???; Orrhage & Müller, 2005) (following Parry et al., 2016). They typically originate as paired projections of the prostomium.
Although it is unlikely that palps and sipunculan tentacles correspond to the lophophore, homology is not inconceivable. We therefore capture the presence of a tentacular apparatus in this very broad character, with arguments against homology reflected in separate transformation series.
[55] Origin
Character 55: Perioral apparatus: Origin
The tentacles of annelids and sipunculans originate from a dorsal pair of buds on the prostomium (Adrianov, Malakhov, & Maiorova, 2006), whereas the brachiopod lophophore arises from the second pair of coelomic sacs (Nielsen, 1991).
Novocrania: “At metamorphosis [….] the second pair of coelomic sacs develop small attachment areas at the edge of the dorsal valve and become the lophophore coelom” (Nielsen, 1991)
“The larval lobes are retained during the first steps of metamorphosis and aresubsequently remodeled to form the lophophore and other adult organs” – Altenburger, Wanninger, & Holmer (2013).
[56] Forms closed loop
Character 56: Perioral apparatus: Forms closed loop
Whereas the lophophore of crown-group brachiopods typically forms a closed loop, those of Haplophrentis and Heliomedusa diverge laterally Moysiuk et al. (2017).
[57] Musculature
Character 57: Perioral apparatus: Musculature
[58] Coiling direction
Character 58: Perioral apparatus: Coiling direction
The lophophore arms of Heliomedusa and Haplophrentis arch posteriad, rather than anteriad as in lingulids. See Zhang et al. (2009);Moysiuk et al. (2017).
[59] Adjustor muscle
Character 59: Perioral apparatus: Adjustor muscle
Following character 55 in Carlson (1995). Not possible to code in most fossil taxa.
[60] Innervation
Character 60: Perioral apparatus: Innervation
Annelid tentacles are innervated by palp nerves (Orrhage & Müller, 2005); lophophores ancestrally contained a pair of nerve rings (???).
[61] Tentaculate
Character 61: Perioral apparatus: Tentaculate
The palps of serpulid worms, and the tentaculate crown of sipunculans, bear secondary tentacles whose appearance corresponds to the tentaculate lophophore of brachiopods. In contrast, the palps of Canadia and the captacula of scaphopods lack secondary tentacles. Coded as transformational as the presence of tentacles is not self-evidently the derived condition.
[62] Disposition
Character 62: Perioral apparatus: Tentacles: Disposition
Tentacles may occur along one or both sides of the axis of the lophophore arm (Carlson, 1995).
[63] Rows per side in trocholophe stage
Character 63: Perioral apparatus: Tentacles: Rows per side in trocholophe stage
After Carlson (1995), character 37. Lophophore tentacles are commonly arranged into an ablabial and adlabial row, with ablabial tentacles sometimes added later in development.
[64] Rows per side in post-trocholophe stage
Character 64: Perioral apparatus: Tentacles: Rows per side in post-trocholophe stage
After Carlson (1995), character 37. Lophophore tentacles are commonly arranged into an ablabial and adlabial row, with ablabial tentacles sometimes added later in development (and thus interpreted as a neomorphic addition).
[65] Median tentacle in early development
Character 65: Perioral apparatus: Tentacles: Median tentacle in early development
Following character 28 in Carlson (1995). Certain taxa exhibit a median tentacle early in development that is lost during ontogeny.
[66] Site of addition
Character 66: Perioral apparatus: Tentacles: Site of addition
Following (???).
[67] Inner nerve ring
Character 67: Perioral apparatus: Tentacles: Inner nerve ring
Juvenile lophophorates exhibit two nerve rings in the tentacles; one of these rings is often reduced or lost at adulthood (???).
[68] Outer nerve ring
Character 68: Perioral apparatus: Tentacles: Outer nerve ring
Juvenile lophophorates exhibit two nerve rings in the tentacles; one of these rings is often reduced or lost at adulthood (???).
[69] Vascular system
Character 69: Perioral apparatus: Tentacles: Vascular system
A blood vessel supplies the tentacles in brachiopods, phoronids and annelids, but not entoprocts or ectoprocts (Nielsen, 1998). Coded as transformational as the ancestral condition is uncertain.
[70] Filter system
Character 70: Perioral apparatus: Tentacles: Filter system
The cilia on the tentacles of adult lophophores invoke currents that are ‘upstream’ or ‘downstream’ (Nielsen, 1998).
The cilia on Sabellid tentacles arise independently from the larval ciliary bands, unlike those of entoprocts, suggesting an independent origin (Nielsen, 1998).
4.9 Radula [71]
Character 71: Radula
Character 25 in Vinther et al. (2017). Any apparatus comprising multiple denticulate rows arranged serially in the sagittal plane is treated as potentially homologous with the molluscan radula.
[72] Extent
Character 72: Radula: Extent
Character 26 in Vinther et al. (2017). The radulae of Wiwaxia and Odontogriphus are conspicuously similar in their configuration.
[73] Subradular membrane
Character 73: Radula: Subradular membrane
Character 38 in Haszprunar (2000). A radular membrane is “a distinct layer below the radular teeth”, present in all molluscs except solenogastres.
[74] Alary processes
Character 74: Radula: Alary processes
A robust structure (alary process/hyaline shield) attached to the radula, with thickened margins, increasingly labile towards the rear, and constructed from the same material (chitin) as the radular teeth (M. R. Smith, 2012b).
Also referred to as a ‘hyaline shield’.
[75] Bolster vesicles
Character 75: Radula: Bolster vesicles
Hollow fluid-filled radula-supporting structures found in Polyplacophora and Monoplacophora (Katsuno & Sasaki, 2008).
[76] Subradular organ
Character 76: Radula: Subradular organ
Character 3g in Waller (1998); Character 58 in Haszprunar (2000).
[77] Heterodonty
Character 77: Radula: Teeth: Heterodonty
Character 29 in Vinther et al. (2017). Heterodonty is sometimes used to denote that different teeth have a different number of cusps, but a is used here in a broader sense to incorporate any differences in tooth morphology. Inapplicable if multiple lateral teeth are not present.
[78] Bending plane
Character 78: Radula: Teeth: Bending plane
Character 60 in Ponder & Lindberg (1997); 2.20 in von Salvini-Plawen & Steiner (1996).
[79] More teeth per row in larger individuals
Character 79: Radula: Teeth: More teeth per row in larger individuals
[80] Lateral tooth base
Character 80: Radula: Teeth: Lateral tooth base
Presence of a distinct base in lateral teeth; see character 9 in Reynolds & Okusu (1999) and 15 in Steiner (1998).
[81] Lateral tooth head
Character 81: Radula: Teeth: Lateral tooth head
In polyplacophorans, the head of the lateral tooth is elaborate or clearly differentiated from the shaft (Steiner, 1999, character 8).
[82] Apatite
Character 82: Radula: Teeth: Apatite
Polyplacophoran teeth are reinforced with apatite (Haszprunar, 2000, character 69).
[83] Magnetite
Character 83: Radula: Teeth: Magnetite
The tips of polyplacophoran teeth contain magnetite (Waller, 1998, character 4e).
4.10 Digestive tract
[84] Prominent pharynx
Character 84: Digestive tract: Prominent pharynx
The buccal organ describes the structures that arise from the larval mouth region. This may include the foregut, which if eversible is termed a proboscis, and whose muscular regions are termed the pharynx (Tzetlin & Purschke, 2005).
Hyoliths exhibit a prominent protrusible muscular pharynx at the base of the lophophore (Moysiuk et al., 2017). This is considered as potentially equivalent to the anterior projection of the visceral cavity in Heliomedusa, and, by extension, in Lingulosacculus and Lingulotreta.
[85] Eversible
Character 85: Digestive tract: Buccal organ: Eversible
Character 133 in Parry & Caron (2019).
[86] Papillae
Character 86: Digestive tract: Buccal organ: Papillae
Character 134 in Parry & Caron (2019).
[87] Salivary glands
Character 87: Digestive tract: Salivary glands
Character 2.27 in von Salvini-Plawen & Steiner (1996).
[88] Oesophageal folds
Character 88: Digestive tract: Oesophageal folds
Following character 86 in Giribet & Wheeler (2002).
[89] Oral sphincter
Character 89: Digestive tract: Oral sphincter
Character 133 in Grobe (2007).
[91] Paired pharyngeal diverticulae
Character 91: Digestive tract: Paired pharyngeal diverticulae
[92] Locomotory cilia
Character 92: Digestive tract: Foregut: Locomotory cilia
Character 66 in Haszprunar (2000).
[93] Subdivisions
Character 93: Digestive tract: Midgut: Subdivisions
The molluscan midgut is functionally subdivided into a sorting area (stomach), digestion area (midgut sac or gland), and transport tube (intestine). Characters 42 in Haszprunar (2000), 1.38 in von Salvini-Plawen & Steiner (1996).
4.11 Digestive tract: Anus
[95] Presence
Character 95: Digestive tract: Anus: Presence
The digestive tract may either constitute a blind sac, or a through gut with anus. The loss of an anus is known to be derived within spiralia, so this character is treated as neomorphic.
[96] Location
Character 96: Digestive tract: Anus: Location
“The relative position of the mouth and anus in the larvae of brachiopods and phoronids is similar: posterior anus and anterior mouth” – Williams et al. (2007), p. 2884. See also character 6 in Haszprunar & Wanninger (2008).
p. 2884.
[97] Migration: Within ring of tentacles
Character 97: Digestive tract: Anus: Migration: Within ring of tentacles
A migrated anus may be located laterally or within the lophophore ring (as in entoprocts).
[98] Migration: Position
Character 98: Digestive tract: Anus: Migration: Position
If the anus is not within the ring of tentacles, in which direction is it oriented?
p. 2884.
4.12 Sclerites
[99] Present in adult (excluding setae)
Character 99: Sclerites: Present in adult (excluding setae)
Plate-like (wider than tall) skeletal elements, whether mineralized or non-mineralized. Corresponds to character 8 in Vinther et al. (2017).
The definition deliberately excludes setae (which are taller than wide).
[100] Periodically shed and replaced
Character 100: Sclerites: Periodically shed and replaced
Certain taxa periodically slough and replace some of their individual sclerites during growth. Others continue to add to sclerites by marginal accretion throughout life.
[101] Prominent major valves
Character 101: Sclerites: Prominent major valves
Equivalent to “Sclerites: Bivalved” in Sun et al. (2018), rephrased to reflect the variation in the number of conceivably homologous ‘major’ shell plates in Aculifera.
A differentiated ventral or posterior valve may be present in addition to a prominent anterior/dorsal valve, corresponding to the ‘head valve’ of chitons or the dorsal valve of brachiopods.
[102] Reduced
Character 102: Sclerites: Accessory sclerites: Reduced
Taxa in the bivalved condition may retain sclerites as small additional elements, such as the L-elements of Paterimitra (Skovsted, Betts, Topper, & Brock, 2015). Hyolithid helens are coded as potentially homologous to these elements (following Moysiuk et al., 2017).
This character is treated as neomorphic, with accessory sclerites ancestrally present, recognizing the likely origin of brachiozoans (and Lophotrochozoans more generally) from a scleritomous organism.
The girdle elements are homologous with annelid chaetae / brachiopod setae (Leise & Cloney, 1982), rather than sclerites.
[103] Arrangement
Character 103: Sclerites: Accessory sclerites: Arrangement
Following Zhao et al. (2017), and reflecting character 5 in Vinther et al. (2017).
[104] Symmetry
Character 104: Sclerites: Accessory sclerites: Symmetry
Following Zhao et al. (2017).
[105] Side slope shape
Character 105: Sclerites: Prominent major valves: Side slope shape
Following character 12 in Cherns (2004).
[106] Additional major valves
Character 106: Sclerites: Prominent major valves: Additional major valves
To reflect the single valve present in Orthrozanclus and the conceivable homology between the tail valve of Halkieria and the ventral valve of brachiopods.
[107] Additional valves: Nature
Character 107: Sclerites: Prominent major valves: Additional valves: Nature
The ventral valve of brachiopods is unlikely to be equivalent to the tail valve of Halkieria or chitons.
[108] Serially repeated
Character 108: Sclerites: Posterior valves: Serially repeated
[109] Number
Character 109: Sclerites: Posterior valves: Number
Vinther et al. (2017) (character 19) report five intermediate shell fields in Kulindroplax, Acaenoplax, multiplacophorans, and the larvae of Chaetoderma.
[110] Apophyses
Character 110: Sclerites: Posterior valves: Apophyses
Character 31 in Vinther et al. (2017). Sutural laminae or apophyses are teeth that articulate adjacent shell plates in many polyplacophorans.
[111] Jugal ridges
Character 111: Sclerites: Posterior valves: Jugal ridges
A jugal ridge is a medial longitudinal ridge. Following character 13 in Cherns (2004).
[112] Insertion plates
Character 112: Sclerites: Posterior valves: Insertion plates
Character 32 in Vinther et al. (2017).
“In the majority of recent chitons the articulamentum may form extensions beyond the margin of the tegmentum. These extensions, called insertion plates, occur on the lateral margins of intermediate valves, on the anterior margin of the head valve and posteriorly on the tail valve” (Schwabe, 2010).
[113] Insertion plates: Slit
Character 113: Sclerites: Posterior valves: Insertion plates: Slit
Character 33 in Vinther et al. (2017).
“The distal edge of the insertion plates may be slitted or solid in different taxa. The bridges between the slits (or incisions) are called teeth and may either be smooth at their outside, roughened, or even strongly pectinate.” (Schwabe, 2010).
[114] Insertion plates: Slit: Nature
Character 114: Sclerites: Posterior valves: Insertion plates: Slit: Nature
Character 34 in Vinther et al. (2017).
[115] Insertion plates: Pectinate
Character 115: Sclerites: Posterior valves: Insertion plates: Pectinate
Character 35 in Vinther et al. (2017).
[116] Differentiated intermediate shell fields
Character 116: Sclerites: Posterior valves: Differentiated intermediate shell fields
Following character 17 in Vinther et al. (2017), itself derived from character 7 in Sigwart & Sutton (2007). A satisfactory definition for this character is not available; it is here taken to mean “intermediate shell fields are differentiated from one another”, rather than “differentiated from the head/tail valves” or “spatially non-overlapping”.
[117] Laterally divided shell fields
Character 117: Sclerites: Posterior valves: Laterally divided shell fields
Per character 18 in Vinther et al. (2017), the intermediate shell fields of multiplacophorans comprise multiple plates.
[118] Hinge line shape
Character 118: Sclerites: Bivalved: Hinge line shape
[119] Enclosing filtration chamber
Character 119: Sclerites: Bivalved: Enclosing filtration chamber
In crown-group brachiopods, the two primary shells close to form an enclosed filtration chamber. Further down the stem, taxa such as Micrina do not.
[120] Commissure: Exact correspondence of valve margins
Character 120: Sclerites: Bivalved: Commissure: Exact correspondence of valve margins
Orthothecid hyoliths can retract their operculum into their conical shell, in contrast to most other taxa, where the valves align exactly when they are closed, save perhaps for a pedicle notch or, in the case of hyolithids, depressions that allow the helens to protrude. Precise correspondence of valve margins is considered to represent a derived feature, so this character is treated as neomorphic (contra Sun et al., 2018).
[121] Commissure: Sulcate
Character 121: Sclerites: Bivalved: Commissure: Sulcate
The anterior commissure can be rectimarginate (i.e. straight), uniplicate (i.e. median sulcus in ventral valve), or sulcate (with median sulcus in dorsal valve).
Inapplicable where valves do not enclose a filtration chamber.
[122] Commissure: Circular
Character 122: Sclerites: Bivalved: Commissure: Circular
Shape of the commissure in plan view, ignoring any deflection arising due to articulation at the hinge (e.g. delthyrium/notothyrium). This character seeks to discriminate the essentially conical ‘conchs’ of orthothecid hyoliths from the polygonal ‘conchs’ of hyolithids. Triangular and oblong outlines are not distinguished, as this is not entirely independent of the strophic/astrophic nature of the hinge.
Inapplicable where valves do not enclose a filtration chamber.
[123] Commissure: Lateral margins
Character 123: Sclerites: Bivalved: Commissure: Lateral margins
If lateral margins are linear, are the subparallel (i.e. commissure profile oblong, with long hinge) or diverging (i.e. commissure profile triangular, with short hinge)?
[124] Apophyses
Character 124: Sclerites: Bivalved: Apophyses
Micrina, like many brachiopods, bears tooth-like structures or processes that articulate the two primary valves. Caution must be applied before taxa are coded as “absent”, as teeth can be subtle and may be overlooked.
[125] Apophyses: Morphology
Character 125: Sclerites: Bivalved: Apophyses: Morphology
Deltidiodont teeth are simple hinge teeth developed by the distal accretion of secondary shell; Cyrtomatodont teeth are knoblike or hook-shaped hinge teeth developed by differential secretion and resorption of the secondary shell (fig. 322 in Williams, James, et al., 1997b).
Kutorginata (here represented by Kutorgina and Nisusia) don’t have teeth (apophyses) or dental sockets, but their shells are articulated by “two triangular plates formed by dorsal interarea, bearing oblique ridges on the inner sides” (Williams et al., 2000, p. 211); this simple hinge mechanism is different from other rhynchonelliforms [Williams et al. (2000), p.208; table 13 character 30], and is described as a “pseudodont articulation” (Holmer, Popov, et al., 2018).
[126] Apophyses: Dental plates
Character 126: Sclerites: Bivalved: Apophyses: Dental plates
Williams, James, et al. (1997b) (p362) write: “Teeth […] are commonly supported by a pair of variably disposed plates also built up exclusively of secondary shell and known as dental plates (Fig. 323.1, 323.3).”
Dewing (2001) elaborates: “Dental plates are near-vertical, narrow sheets of shell tissue between the anteromedian edge of the teeth and floor of the ventral valve. They are a composite structure, resulting from the growth of teeth over the ridge that bounds the ventral-valve muscle field.”
Williams et al. (2000) (p.201) write: “The denticles lack supporting structures in all Obolellida, but in Naukatida they are supported by an arcuate plate below the
interarea, the anterise (Fig. 119.3a)”.
The anterise is conceivably homologous with the dental plates, thus the presence of either is coded “present” for this character.
[127] Sockets
Character 127: Sclerites: Bivalved: Sockets
Simplified from Bassett, Popov, & Holmer (2001) character 16.
This character is independent of apophyses, as several taxa bear sockets without corresponding teeth; the function of these sockets is unknown.
See figs 323ff in Williams, James, et al. (1997b).
[128] Socket ridges
Character 128: Sclerites: Bivalved: Socket ridges
After Bassett et al. (2001), character 17. May be difficult to distinguish from a brachiophore (see Fig 323 in Williams, James, et al., 1997b), so the two structures are not distinguished here.
[129] Muscle scars: Ventral
Character 129: Sclerites: Bivalved: Muscle scars: Ventral
After character 6 in Bassett et al. (2001).
[130] Muscle scars: Ventral: Position
Character 130: Sclerites: Bivalved: Muscle scars: Ventral: Position
Muscles can attach to the ventral valve posterolaterally to, as well as between, the vascula lateralia (Popov, 1992).
[131] Muscle scars: Adjustor
Character 131: Sclerites: Bivalved: Muscle scars: Adjustor
After character 7 in Bassett et al. (2001).
This character is contingent on the presence of a pedicle. Extreme caution must be used in inferring an absent state, as adjustor scars can be extremely difficult to distinguish from the adductor scars.
[132] Muscle scars: Dorsal adductors
Character 132: Sclerites: Bivalved: Muscle scars: Dorsal adductors
After character 8 in Bassett et al. (2001), character 35 in Williams, Carlson, Brunton, Holmer, & Popov (1996), and character 54 in Williams et al. (2000) (p. 160)
In the dorsal valve, the anterior and posterior adductor scars of articulated brachiopods form a single (quadripartite) muscle field (Williams et al. 2000, p. 201)
In contrast, the anterior and posterior scars of e.g. trimerellids have prominently separate attachment points, with anterior and posterior muscle fields clearly distinct, and coded as “dispersed”.
In e.g. kutorginates, adductor muscles are separated into left and right fields; the same is the case in lingulids, where there are more separate muscle groups and the left and right fields conspire to produce a radial arrangement; both of these configurations are scored as “radially arranged”.
[133] Muscle scars: Adductors: Position
Character 133: Sclerites: Bivalved: Muscle scars: Adductors: Position
Position of adductor muscles relative to commissural plane.
After character 11 in Bassett et al. (2001).
[134] Muscle scars: Dermal muscles
Character 134: Sclerites: Bivalved: Muscle scars: Dermal muscles
Based on character 11 in Zhang et al. (2014).
Well developed dermal muscles present in the body wall of recent lingulates, which are absent in all calcareous-shelled brachiopods. These muscles are responsible for the hydraulic shell-opening mechanism, and possibly present in all organophosphatic-shelled brachiopods, with the possible exception of the paterinates (Williams et al., 2000, p. 32).
[135] Muscle scars: Unpaired median (levator ani)
Character 135: Sclerites: Bivalved: Muscle scars: Unpaired median (levator ani)
The levator ani is a diminutive unpaired medial muscle found in certain calcitic brachiopods [Williams et al. (2000); see fig. 89, character 34 in table 13].
[136] Muscle scars: Dorsal diductor
Character 136: Sclerites: Bivalved: Muscle scars: Dorsal diductor
After character 9 in Bassett et al. (2001).
[137] Muscle scars: Dorsal diductor: Position
Character 137: Sclerites: Bivalved: Muscle scars: Dorsal diductor: Position
After character 10 in Bassett et al. (2001).
[138] Coiling direction
Character 138: Sclerites: Dorsal valve: Coiling direction
A mollusc shell is termed endogastric if the shell coils towards the posterior, and exogastric if the coiling direction is to the anterior.
4.13 Sclerites: Dorsal valve
[139] Growth direction
Character 139: Sclerites: Dorsal valve: Growth direction
See Fig. 284 in Williams, James, et al. (1997b). Corresponds to character 15 in Sutton et al. (2012); and cf. character 3 in Wagner (1997).
The growth direction dictates the attitude of the cardinal area relative to the hinge, which does not therefore represent an independent character.
Crudely put, if, viewed from a dorsal position, the umbo falls within the outer margin of the shell, growth is holoperipheral; if it falls outside the margin, it is mixoperipheral; if it falls exactly on the margin, it is hemiperipheral.
For the purposes of this analysis, we must treat polyplacophoran and brachiopod valves as potentially homologous.
In brachiopods, the dorsal valve bears the lophophore, which arises from the anterior lobe of the larva (Altenburger et al., 2013) – indicating that the dorsal shell field is associated with the anterior lobe.
In polyplacophorans, the head valve arises from a shell field on the anterior (pre-prototroch) lobe of the larva (Wanninger & Haszprunar, 2002a), which we therefore treat as homologous with the brachiopod dorsal valve.
In support of this hypothesis, we note that the posterior (but not anterior) valves of chitons bear apophyses (Connors et al., 2012; Schwabe, 2010), which are most prominent in the ventral (but not dorsal) valves of brachiopods (Williams et al 1997, fig. 322), and which occur in the morph A shell of Oikozetetes, which is interpreted as the posterior valve of a halkieriid (Paterson et al., 2009).
As the single posterior shell field of polyplacophorans subdivides to give rise to the six intermediate valves plus the tail valve (Wanninger & Haszprunar, 2002a), we prefer to consider the intermediate valves as representing “subdivisions” of a single valve rather than additional valves added to the body plan.
Heliomedusa orienta: “holoperipheral growth in dorsal valve” – Williams et al. 2007.
Zhang et al. (2009) conclude that Chen et al. (2007) misidentify the dorsal valve as the ventral valve.[140] Aspect
Character 140: Sclerites: Dorsal valve: Aspect
Character 16 in Sutton et al. (2012). Length:width ratio of the primary valve. Coded ambiguous in marginal cases: for example, a length:width ratio of 1.02:1 might be coded ambiguous(elongate, equant).
[141] Anterior projection
Character 141: Sclerites: Dorsal valve: Anterior projection
Character 10 in Wagner (1997). The dorsal valves of bivalves, scaphopods and rostroconchs are characterized by an anterior projection.
[142] Anterior projection: Angle
Character 142: Sclerites: Dorsal valve: Anterior projection: Angle
After character 11 in Wagner (1997). An acute projection characterizes scaphopods and Conocardioid rostroconchs, whereas bivalves exhibit a blunt projection.
[143] Posterior projection
Character 143: Sclerites: Dorsal valve: Posterior projection
Character 23 in Wagner (1997). An adapical projection with an angle of over sixty degrees is borne by the posterior of the valve in included Diasoma.
[144] Rostrum
Character 144: Sclerites: Dorsal valve: Rostrum
Simplified from character 62 in Wagner (1997). The ‘rostrum’ of Pojeta & Runnegar (1976) is an extension of the posterior portion of the shell.
[145] Ligament
Character 145: Sclerites: Dorsal valve: Ligament
The bivalve ligament is a weakly calcified region of the shell that connects two calcified regions.
[146] Posterior surface: Differentiated
Character 146: Sclerites: Dorsal valve: Posterior surface: Differentiated
In shells that grow by mixoperipheral growth, the triangular area subtended between each apex and the posterior ends of the lateral margins is termed the cardinal area. In shells with holoperipheral growth, a flattened surface on the posterior margin of the valve is termed a pseudointerarea (paraphrasing Williams, James, et al., 1997b).
In order for this character to be independent of a shell’s growth direction, we do not distinguish between a “cardinal area”, “interarea” or “pseudointerarea”.
[147] Differentiated posterior surface: Morphology
Character 147: Sclerites: Dorsal valve: Differentiated posterior surface: Morphology
It is possible for a cardinal area or pseudointerarea to be distinct from the anterior part of the shell, yet to remain curved in lateral profile.
Taking an undifferentiated posterior margin as primitive, the primitive condition is curved – flattening of the posterior margin represents an additional modification that can only occur once the posterior margin is differentiated.
[148] Posterior surface: Medial groove
Character 148: Sclerites: Dorsal valve: Posterior surface: Medial groove
Following character 29 in Williams et al. (2000), table 9 (which relates to pseudointerarea).
[149] Posterior surface: Notothyrium
Character 149: Sclerites: Dorsal valve: Posterior surface: Notothyrium
A notothyrium is an opening in an interarea that accommodates the pedicle, and may be filled with plates.
[150] Posterior surface: Notothyrium: Shape
Character 150: Sclerites: Dorsal valve: Posterior surface: Notothyrium: Shape
A notothyrium is an opening in an interarea that accommodates the pedicle, and may be filled with plates.
A simplification of character 5 in Bassett et al. (2001).
[151] Posterior surface: Notothyrium: Chilidial plates
Character 151: Sclerites: Dorsal valve: Posterior surface: Notothyrium: Chilidial plates
A notothyrium may be open or covered by a chilidium or two chilidial plates.
No included taxa exhibit more than one chilidial plate.
Transformational as it is not self-evident whether the ancestral taxon had an open or closed notothyrium.
[152] Notothyrial platform
Character 152: Sclerites: Dorsal valve: Notothyrial platform
After character 12 in Bassett et al. (2001).
The presence or absence of a notothyrial platform, which often serves as an attachment point for the diductors in a similar fashion to the cardinal processes, is independent of the presence of a notothyrium.
[153] Medial septum
Character 153: Sclerites: Dorsal valve: Medial septum
The dorsal valve of many taxa is exhibits a septum or process (or myophragm) along the medial line. See character 25 in Benedetto (2009).
Heliomedusa orienta: Reported on ‘ventral’ valve by Chen et al. (2007); we consider their ‘ventral’ valve to be the dorsal valve.
The structure is unambiguously figured (e.g. fig. 5.1 in Chen et al. 2007), contra its coding as absent in Williams et al. 2000 and its lack of mention in Williams et al. 2007 or Zhang et al. 2009.[154] Cardinal shield
Character 154: Sclerites: Dorsal valve: Cardinal shield
The hyolithid operculum is divided into a cardinal and conical shield (???), separated by furrows corresponding to the position of the helens. See Marek (1976) (fig. 2) or Martí Mus & Bergström (2005) (fig. 1) for schematic.
With no obvious sites for muscle attachment, the shields are unlikely to be homologous to the notothyrial platform.
[155] Cardinal processes
Character 155: Sclerites: Dorsal valve: Cardinal processes
After character 13 in Bassett et al. (2001). See Martí Mus & Bergström (2005) for an illustration.
Cardinal processes are unlikely to be homologous with the notothyrial platform, even if their function is similar.
[156] Cardinal teeth
Character 156: Sclerites: Dorsal valve: Cardinal teeth
Radially arranged teeth, separated by furrows, adorn the cardinal margin of the operculum of certain hyolithids (Marek, 1963). The absence of corresponding tooth sockets indicates that they do not serve to articulate the valves; Marek (1967) does not consider the teeth to be homologous with brachiopod cardinal teeth.
[157] Clavicles
Character 157: Sclerites: Dorsal valve: Clavicles
Prominent symmetrical ridges on the inner surface of the hyolith operculum.
[158] Clavicles: Type of clavicles
Character 158: Sclerites: Dorsal valve: Clavicles: Type of clavicles
Usually the operculum of hyoliths has one pair of clavicles, but in some taxa of hyolithida there are more than one pair of clavicles, which can be divided into six types (Marek, 1967). The included taxa either exhibit a single pair of monoclavicles, or three pairs of clavicles.
4.14 Sclerites: Ventral valve
[159] Growth direction
Character 159: Sclerites: Ventral valve: Growth direction
See Fig. 284 in Williams, James, et al. (1997b) for depiction of terms.
The growth direction dictates the attitude of the cardinal area relative to the hinge, which does not therefore represent an independent character.
Crudely put, if, viewed from a dorsal position, the umbo falls within the outer margin of the shell, growth is holoperipheral; if it falls outside the margin, it is mixoperipheral; if it falls exactly on the margin, it is hemiperipheral.
[160] Relative size
Character 160: Sclerites: Ventral valve: Relative size
In many brachiopods, the valves are closely similar in size; in others, the ventral valve is markedly larger than the dorsal, on account of being more convex. Marginal cases are treated as ambiguous for the relevant states.
[161] Ligula
Character 161: Sclerites: Ventral valve: Ligula
The aperture of many hyolithid hyoliths is characterised by a ligula, a tongue-like protruding shelf on the functionally ventral surface of conical shell (Martí Mus & Bergström, 2005). This can be recognized by an acute angle in the lateral profile of the commissure (see second figure on p. 91 of Marek, 1966). No brachiopods display an equivalent feature.
[162] Posterior surface: Differentiated
Character 162: Sclerites: Ventral valve: Posterior surface: Differentiated
In shells that grow by mixoperipheral growth, the triangular area subtended between each apex and the posterior ends of the lateral margins is termed the cardinal area. In shells with holoperipheral growth, a flattened surface on the posterior margin of the valve is termed a pseudointerarea (paraphrasing Williams, James, et al., 1997b).
In order for this character to be independent of a shell’s growth direction, we do not distinguish between a “cardinal area”, “interarea” or “pseudointerarea”.
[163] Posterior surface: Growth direction
Character 163: Sclerites: Ventral valve: Posterior surface: Growth direction
Balthasar (2008) notes an inward-growing posterior margin of the pseudointerarea as potentially linking Mummpikia with the linguliform brachiopods.
Coded as inapplicable in taxa without a differentiated posterior margin: the posterior margin can only grow inwards if it is differentiated from the anterior margin; else the entire shell would grow in on itself.
[164] Posterior surface: Planar
Character 164: Sclerites: Ventral valve: Posterior surface: Planar
It is possible for a cardinal area or pseudointerarea to be distinct from the anterior part of the shell, yet to remain curved in lateral profile.
Taking an undifferentiated posterior margin as primitive, the primitive condition is curved – flattening of the posterior margin represents an additional modification that can only occur once the posterior margin is differentiated.
A flat and triangular interarea links Mummpikia with the Obolellidae(Balthasar, 2008) – but all included taxa have triangular interareas, so this is not listed as a separate character.
[165] Posterior surface: Extent
Character 165: Sclerites: Ventral valve: Posterior surface: Extent
Distinguishes taxa whose ventral valve is essentially flat from those that are essentially conical.
[166] Posterior surface: Delthyrium
Character 166: Sclerites: Ventral valve: Posterior surface: Delthyrium
A delthyrium is an opening in an interarea or pseudointerarea that accommodates the pedicle, and may be filled with plates.
The homology of the pedicle in the pseudointerarea of obolellids and botsfordiids with the umbonal pedicle foramen of acrotretids was proposed by Popov (1992), and seemingly corroborated by observations of Ushatinskaya & Korovnikov (2016), who note that the propareas of the Botsfordia ventral valve sometimes merge to form an elongate teardrop-shaped pedicle foramen.
[167] Posterior surface: Delthyrium: Shape
Character 167: Sclerites: Ventral valve: Posterior surface: Delthyrium: Shape
A parallel-sided delthyrium links Mummpikia with the Obolellidae (Balthasar, 2008).
Following Popov (1992), the larval delthyrium of acrotretids and allied taxa is understood to be sealed in adults by outgrowths of the posterolateral margins of the shell. The resultant round or teardrop-shaped foramen corresponds the delthyrium.
[168] Posterior surface: Delthyrium: Shape: Aspect of rounded opening
Character 168: Sclerites: Ventral valve: Posterior surface: Delthyrium: Shape: Aspect of rounded opening
Chen, Huang, & Chuang (2007) propose that an oval to rhombic foramen characterises the discinids (and Heliomedusa, though the foramen in this taxon has since been reinterpreted by Zhang et al. (2009) as an impression of internal tissue).
[169] Posterior surface: Delthyrium: Cover
Character 169: Sclerites: Ventral valve: Posterior surface: Delthyrium: Cover
An open delthyrium links Mummpikia with the Obolellidae (Balthasar, 2008).
The delthyrial opening can be covered by one or more deltidial plates, or a pseudodeltitium.
Inapplicable in taxa with a round delthiruym (generated by overgrowth of the delthyrial opening by posterolateral parts of the shell, per Popov (1992)).
[170] Posterior surface: Delthyrium: Cover: Extent
Character 170: Sclerites: Ventral valve: Posterior surface: Delthyrium: Cover: Extent
[171] Posterior surface: Delthyrium: Cover: Identity
Character 171: Sclerites: Ventral valve: Posterior surface: Delthyrium: Cover: Identity
This character has the capacity for further resolution (one or more deltidial plates), but this is unlikely to affect the results of the present study.
The pseudodelthyrium is also referred to as a homeodeltidium.
The antemucronal area of Polyplacophora is treated as equivalent to the brachiopod delthyrium, but is not depositionally distinct to the rest of the shell, so is coded with a distinct character state.
[172] Posterior surface: Delthyrium: Pseudodeltidium: Shape
Character 172: Sclerites: Ventral valve: Posterior surface: Delthyrium: Pseudodeltidium: Shape
A ridge-like (i.e. convex) pseudodeltitium unites Salanygolina with Coolinia and other Chileata (Holmer, Pettersson Stolk, Skovsted, Balthasar, & Popov, 2009, p. 6).
[173] Posterior surface: Delthyrium: Pseudodeltidium: Hinge furrows
Character 173: Sclerites: Ventral valve: Posterior surface: Delthyrium: Pseudodeltidium: Hinge furrows
After character 18 in Bassett et al. (2001), “Hinge furrows on lateral sides of pseudodeltidium”.
[174] Umbonal perforation
Character 174: Sclerites: Ventral valve: Umbonal perforation
Certain taxa, particularly those with a colleplax, exhibit a perforation at the umbo of the ventral valve. This opening is sometimes associated with a pedicle sheath, which emerges from the umbo of the ventral valve without any indication of a relationship with the hinge.
In contrast, the pedicle of acrotretids and similar brachiopods is situated on the larval hinge line, but is later surrounded by the posterolateral regions of the growing shell to become separated from the hinge line, and encapsulated in a position close to (or with resorption of the brephic shell, at) the umbo (see Popov (1992), pp. 407–411 and fig. 3 for discussion). In some cases, an internal pedicle tube attests to this origin – potentially corresponding to the pedicle groove of lingulids. As such, the pedicle foramen of acrotretids and allies is not originally situated at the umbo; it is instead understood to represent a basally sealed delthyrium.
Dailyatia: The B and C sclerites of Dailyatia bear small umbonal perforations (Skovsted et al 2015), but these are not considered to be homologous with the ventral valve, so this character is coded as inapplicable – though the possibility that the perforations are equivalent is intriguing.
A1 sclerites typically have a pair of perforations, which are conceivably equivalent to the setal tubes of Micrina (Holmer et al. 2011). The A1 sclerite of D. bacata has a structure that is arguably similar to the ‘colleplax’ of Paterimitra. But the homology of any of these structures to the umbonal aperture of brachiopods is difficult to establish.illustrated by Chen et al. (2007: Figs. 4, 6, 7) in fact is the mold of a three-dimensionally preserved visceral cavity.” – Zhang et al. 2009.
[175] Umbonal perforation: Shape
All taxa are coded as ambiguous or inapplicable for this character.
Character 175: Sclerites: Ventral valve: Umbonal perforation: Shape
## Warning in MatrixData(states_matrix, states_matrix, state.labels =
## my_states[[i]]): State labels do not seem to match states. You need to
## label all states from 0 to the maximum observed.The perforation in Cupitheca seems to have a distinct origin, arising through decollation; as such, the shape simply reflects the outline of the shell. This reflects a distinct origin of the perforation and is therefore provided as a separate state.
[176] Colleplax, cicatrix or pedicle sheath
Character 176: Sclerites: Ventral valve: Colleplax, cicatrix or pedicle sheath
In certain taxa, the umbo of the ventral valve bears a colleplax, cicatrix or pedicle sheath; Bassett, Popov, & Egerquist (2008) consider these structures as homologous.
[177] Median septum
Character 177: Sclerites: Ventral valve: Median septum
Chen et al. (2007) observe a median septum in what they interpret as the ventral valve of Heliomedusa, and the ventral valve of Discinisca, which they propose points to a close relationship.
4.15 Sclerites: Ornament
[178] Concentric ornament
Character 178: Sclerites: Ornament: Concentric ornament
After character 11 in Williams et al. (1998b). Coded as transformational as it is possible that maintaining a smooth shell without occasional prominent ridges requires greater secretory control.
[179] Concentric ornament: Symmetry
Character 179: Sclerites: Ornament: Concentric ornament: Symmetry
After character 11 in Williams et al. (1998b).
[180] Radial ornament
Character 180: Sclerites: Ornament: Radial ornament
Ridges radiating from umbo, i.e. ribs.
[181] Shell-penetrating spines
Character 181: Sclerites: Ornament: Shell-penetrating spines
Mineralized or partly mineralized spines are observed in Heliomedusa and Acanthotretella.
4.16 Sclerites: Composition
[182] Mineralogy
Character 182: Sclerites: Composition: Mineralogy
[183] Carbonate nucleation site
Character 183: Sclerites: Composition: Carbonate nucleation site
Calcium carbonate nucleates either within or outside the epidermis.
[184] Cuticle or organic matrix
Character 184: Sclerites: Composition: Cuticle or organic matrix
Williams et al. (1996) identify glycoprotein-based organic scaffolds as distinct from those comprising glycosaminoglycans (GAGs), chitin and collagen. This character can only be scored for extant taxa.
[185] Incorporation of sedimentary particles
Character 185: Sclerites: Composition: Incorporation of sedimentary particles
Phoronids and Yuganotheca aggulutinate particles into their sclerites.
[186] Microstructure: Number of distinct layers
Character 186: Sclerites: Composition: Microstructure: Number of distinct layers
Hyolith conchs comprise two mineralized layers of fibrous bundles. Bundles are measure 5–15 μm across; their constituent fibres are each 0.1–1.0 μm wide. In the inner layer, the fibres are transverse; in the outer layer, the bundles are inclined towards the umbo, becoming longitudinal on the outermost margin.
Coded as non-additive as there is no clear necessity to add layers sequentially: for example, three layers could arise by the addition of a void within a single pre-existing layer.
Stratiform laminae, shell-penetrating canals and other features above the scale of crystal organization are not considered as contributing to the mineralogical microstructure and are coded separately.
Inapplicable in taxa with a non-mineralized shell.
“Spherulitic aragonitic prisms beneath the organic periostracum” (Runnegar, 1985).
[187] Microstructure: Format
Character 187: Sclerites: Composition: Microstructure: Format
Hyolith conchs comprise two mineralized layers of fibrous bundles. Bundles measure 5–15 μm across; their constituent fibres are each 0.1–1.0 μm wide. In the inner layer, the fibres are transverse; in the outer layer, the bundles are inclined towards the umbo, becoming longitudinal on the outermost margin.
Stratiform laminae, shell-penetrating canals and other features above the scale of crystal organization are not considered as contributing to the mineralogical microstructure and are coded separately.
The pervasive (not just superficial) polygonal structures in Paterimitra are distinct, and characterize Askepasma, Salanygolina, Eccentrotheca and Paterimitra (Larsson et al., 2014)
Williams et al. (2000) identify cross-bladed laminae as diagnostic of Strophomenata, with the exception of some older groups that contain fibres or laminar laths.
4.17 Sclerites: Structure
[188] Stratiform lamellae expressed at surface
Character 188: Sclerites: Structure: Stratiform lamellae expressed at surface
In tommotiids, the shell simply comprises a stack of stratiform lamellae, each corresponding to a circumferential rib at the shell surface. This is particularly apparent in Dailyatia (Skovsted et al., 2015) and Paterimitra (Larsson et al., 2014).
[189] Stratiform laminae separated
Character 189: Sclerites: Structure: Stratiform laminae separated
Laminae within, for example, Salanygolina are separated by voids that may originally have contained organic material (e.g. ???). In contrast, tommotiids and paterinids exhibit stratification without voids, perhaps representing periodic fluctuations in phosphate availability (Balthasar et al., 2009).
[190] Stratiform laminae with polygonal ornament
Character 190: Sclerites: Structure: Stratiform laminae with polygonal ornament
See character 37 in Williams et al. (1998b).
“A distinct primary layer […] is characterized by a polygonal ornament that is mineralized from the polygon walls inward, while the rest of the shell and/or sclerite is secreted by basal accretion” – (???). Distinguished from epithelial cell moulds in lingulids, which do not form an integral part of the shell structure (???).
Treated as transformational as ancestral condition is ambiguous.
[191] Canals
Character 191: Sclerites: Structure: Canals
A caniculate microstructure occurs in lingulids; canals are narrower (< 1 μm) than punctae, may branch, and do not fully penetrate the shell, terminating just within the boundaries of a microstructural layer. See Williams, James, et al. (1997b), p303ff, and Balthasar (2008), p273, for discussion.
Tubules described in hyoliths by Kouchinsky (2000) measure around 10 μm in diameter, making them an order of magnitude wider than lingulid canals.
This said, Balthasar (2008) considers the rod-like tubules within the columnar shell microstructure of Mickwitzia cf. occidens (1–3 μm wide, Skovsted & Holmer 2003), acrotretides (1 μm wide, see Holmer (1989), Zhang, Zhang, & Wang (2016)) and lingulellotretids (100 nm wide, Cusack, Williams, & Buckman (1999)) as equivalent to lingulid canals.
Micrina exhibits both punctae and canals (Harper, Popov, & Holmer (2017)), challenging Carlson’s contention (in Williams et al. (2007)) that the structures are potentially homologous as shell perforations.
Micrina: Acrotretid laminae bear characteristic columns (e.g. Zhang et al. 2016); a similar fabric has been reported, and assumed homologous, in Micrina (Butler et al. 2012).
A similar columnar shell microstructure also occurs in the closely related Mickwitzia (Balthasar 2008).[192] Punctae
Character 192: Sclerites: Structure: Punctae
Punctae are 10–20 μm wide canals created by multicellular extensions of the outer epithelium. They penetrate the full depth of the shell.
Balthasar (2008) writes:
“Vertical shell penetrating structures, such as punctae, pseudopunctae, extropunctae and canals, are common in many groups of brachiopods and are distinguished based on their geometry and size (Williams, James, et al., 1997b). Punctae are 10–20 μm wide and represent multicellular extensions of the outer epithelium (Owen & Williams, 1969). Pseudopunctae and extropunctae are similar in diameter but, instead of canals, are vertical stacks of conical deflections of individual shell layers (Williams & Brunton, 1993). None of these three types of vertical shell structure, all of which are confined to calcitic-shelled brachiopods, compares with the much smaller canals (< 1 μm in diameter) of M. nuda. The only type of vertical structure that fits the size and nature of the canals of the Mural obolellids are the canals of linguliform brachiopods, which range in width from 180 to 740 nm and are occupied by proteinaceous strands in extant taxa [Williams, Mackay, & Cusack (1992);Williams, Cusack, & Mackay (1994);Williams, James, et al. (1997b)). In contrast to obolellid canals, however, linguliform canals are not known to penetrate the entire shell but terminate in organic-rich layers (Williams 1997). Based on these considerations it would, therefore, be misleading to call obolellid shells punctate (they are as much”punctate" as acrotretids or other linguliforms); rather their shell structure should be called canaliculate (Williams, James, et al., 1997b)."
[193] Pseudopunctae
Character 193: Sclerites: Structure: Pseudopunctae
Pseudopunctae are not punctae, but deflections of shell laminae. They characterise Strophomenata in particular.
[194] External polygonal ornament
Character 194: Sclerites: Structure: External polygonal ornament
Regular polygonal compartments, around 10 μm in diameter, characterise Paterimitra. Walls between compartments have the cross-section of an anvil. An external polygonal structure (possible imprints of epithelial tissue) occurs in Dailyatia, but it is a surface pattern, which is different from the polygonal prisms in the body wall of other paterinid-like groups.
[195] Aesthete canals
Character 195: Sclerites: Structure: Aesthete canals
Following character 20 of Vinther et al. (2017).
[196] Aesthete canals: Orientation
Character 196: Sclerites: Structure: Aesthete canals: Orientation
Following Hoare (2009).
[197] Aesthete canals: Size variation
Character 197: Sclerites: Structure: Aesthete canals: Size variation
Following Vendrasco & Runnegar (2004).
[198] Aesthete canals: Megalaesthete bulbs
Character 198: Sclerites: Structure: Aesthete canals: Megalaesthete bulbs
Megalaesthetes are the large aesthete canals from which smaller chambers emerge. Character ‘lin’ in Vendrasco et al. (2008).
[199] Subapical tunnels
Character 199: Sclerites: Structure: Subapical tunnels
Character 23 in Vinther et al. (2017). Distinct from the umbonal perforation observed in some ventral valves on account of their subapical position. Also termed ‘lacunae’.
[200] Articulamentum
Character 200: Sclerites: Structure: Articulamentum
Character 30 in Vinther et al. (2017). The articulamentum is a secondary layer of shell present in polyplacophorans.
4.18 Gametes
[203] Ovary wall saccular
Character 203: Gametes: Ovary wall saccular
After character 31 in Haszprunar (1996).
[204] Testis wall saccular
Character 204: Gametes: Testis wall saccular
After character 31 in Haszprunar (1996).
[205] Asexual reproduction
Character 205: Gametes: Asexual reproduction
After character 30 in Haszprunar (1996).
[206] Sexes
Character 206: Gametes: Sexes
After characters 1.61 and 2.54 in von Salvini-Plawen & Steiner (1996).
4.19 Gametes: Egg
[208] Size
Character 208: Gametes: Egg: Size
Following Carlson (1995), character 7. This character is only possible to code in extant taxa. It is not considered independent of Carlson’s character 11, number of gametes released per spawning, as it is possible to produce more small eggs than large eggs – thus this latter character is not reproduced in the present study. The same goes for Carlson’s character 12, gamete dispersal mode; brooders will tend to brood large eggs.
[209] Protective membrane
Character 209: Gametes: Egg: Protective membrane
After character 4.69 in von Salvini-Plawen & Steiner (1996).
[210] Site of maturation
Character 210: Gametes: Egg: Site of maturation
After Carlson (1995), character 9. Only possible to code in extant taxa.
[211] Nucleus: Aspect
Character 211: Gametes: Spermatozoa: Nucleus: Aspect
After character 41 in Ponder & Lindberg (1997).
4.20 Gametes: Spermatozoa
[212] Nucleus: Shape
Character 212: Gametes: Spermatozoa: Nucleus: Shape
Most spermatozoa have nuclei with an invagination; see character 50 in Ponder & Lindberg (1997).
[213] Nucleus: Nuclear filament
Character 213: Gametes: Spermatozoa: Nucleus: Nuclear filament
A nuclear filament is an anterior extension of the nucleus that terminates at the acrosome, present in lepidopleurid chitons (Buckland-Nicks, 2008, character 6).
[214] Anterior nuclear fossa
Character 214: Gametes: Spermatozoa: Anterior nuclear fossa
After character 160 in Giribet & Wheeler (2002). A fossa (latin: ditch) is a dent or impression.
[215] Acrosome
Character 215: Gametes: Spermatozoa: Acrosome
Sometimes fully termed the Acrosome vesicle.
[216] Acrosome: Shape
Character 216: Gametes: Spermatozoa: Acrosome: Shape
[217] Acrosome: Differentiated internally
Character 217: Gametes: Spermatozoa: Acrosome: Differentiated internally
Hodgson & Reunov (1994) describe the Discinisca acrosome as having “an electron-lucent centre and an electron-dense outer region”, and state that this trait is characteristic of inarticulate brachiopods. The interstitial granule of certain polyplacophorans represents a separate mode of acrosome differentiation. The subacrosomal granule and subacrosomal basal plate are treated separately, and are not considered to represent internal differentiation.
[218] Acrosome: Subacrosomal basal plate
Character 218: Gametes: Spermatozoa: Acrosome: Subacrosomal basal plate
Character 41 in Ponder & Lindberg (1997).
[219] Acrosome: Subacrosomal basal plate: Basal granule
Character 219: Gametes: Spermatozoa: Acrosome: Subacrosomal basal plate: Basal granule
In certain taxa, the subacrosomal basal plate develops a subacrosomal granule (Buckland-Nicks, 2008).
[220] Mid-piece
Character 220: Gametes: Spermatozoa: Mid-piece
Following Hodgson & Reunov (1994).
[221] Mid-piece: Mitochondrial location
Character 221: Gametes: Spermatozoa: Mid-piece: Mitochondrial location
Following character 3 in Buckland-Nicks (2008) and character 166 in Giribet & Wheeler (2002).
[222] Centrioles: Orientation
Character 222: Gametes: Spermatozoa: Centrioles: Orientation
Following Hodgson & Reunov (1994).
[223] Centrioles: Fusion
Character 223: Gametes: Spermatozoa: Centrioles: Fusion
Following character 9 in Buckland-Nicks (2008).
[224] Satellite fibre complex
Character 224: Gametes: Spermatozoa: Satellite fibre complex
Following M. R. Smith (2012a), after character 48 in Ponder & Lindberg (1997).
[225] Mitochondria: Shape
Character 225: Gametes: Spermatozoa: Mitochondria: Shape
After character 5 in Buckland-Nicks (2008); see also character 43 in Ponder & Lindberg (1997).
[226] Mitochondria: Cristae: Configuration
Character 226: Gametes: Spermatozoa: Mitochondria: Cristae: Configuration
After character 44 in Ponder & Lindberg (1997). Cristae are internal compartments formed by inner mitochondrial membranes.
[227] Mitochondria: Midpiece
Character 227: Gametes: Spermatozoa: Mitochondria: Midpiece
After M. R. Smith (2012a); see also character 43 in Ponder & Lindberg (1997); character 164 in Giribet & Wheeler (2002).
4.21 Embryo
[228] Micromere size
Character 228: Embryo: Micromere size
Following Hejnol (2010). Blastomeres may undergo significant size differentiation, generating macromeres and micromeres of prominently different sizes.
blastomeres” (Gruhl, 2010b).
[229] Equal
Character 229: Embryo: Cleavage: Equal
Following character 170 in Giribet & Wheeler (2002).
[230] Cross pattern
Character 230: Embryo: Cleavage: Cross pattern
The “molluscan cross” and “annelid cross” cannot be systematically discriminated from one another, so are treated as a single state.
See characters 127 & 128 in Rouse (1999); 1.49 in von Salvini-Plawen & Steiner (1996);
character 34 in Haszprunar (1996); 35 in Haszprunar (2000); 172 in Giribet & Wheeler (2002).
[231] Polar lobe formation
Character 231: Embryo: Cleavage: Polar lobe formation
Following character 171 in Giribet & Wheeler (2002).
[232] Spiral
Character 232: Embryo: Cleavage: Spiral
See characters 32–33 in Haszprunar (1996); character 1.48 in von Salvini-Plawen & Steiner (1996); character 29 in Glenner et al. (2004).
[233] Origin of mesoderm
Character 233: Embryo: Origin of mesoderm
After characters 32 in Grobe (2007) and 36–37 in Glenner et al. (2004), which follow Nielsen (1998). “Phoronids, brachiopods and pterobranchs are archimeric, i.e., the body comprises three regions, each with one or a pair of coeloms […] the mesoderm originates from the archenteron” (Nielsen, 1998).
4.22 Larva: Apical organ
[234] Muscles extending to the hyposphere
Character 234: Larva: Apical organ: Muscles extending to the hyposphere
Character 8 in Vinther et al. (2008).
[235] Serotonergic cells
Character 235: Larva: Apical organ: Serotonergic cells
Character 8 in Haszprunar & Wanninger (2008).
[236] Develops into adult brain
Character 236: Larva: Apical organ: Develops into adult brain
Character 79 in Glenner et al. (2004).
the adult nervous system” (Hay-Schmidt, 1992), but not necessarily as the brain.
[237] Brain persists into adulthood
Character 237: Larva: Brain persists into adulthood
After character 3 in Richter et al. (2010).
[238] Origin of body cavity
Character 238: Larva: Origin of body cavity
Character 1.43 in von Salvini-Plawen & Steiner (1996).
[239] Formation of coelomoducts
Character 239: Larva: Formation of coelomoducts
Character 26 in Haszprunar (2000).
[240] Retractor muscles
Character 240: Larva: Retractor muscles
A possible synapomorphy of Pleistomollusca (=bivalves + gastropods) (Kocot et al., 2011). See Wanninger & Haszprunar (2002b).
[241] Velum muscle ring
Character 241: Larva: Velum muscle ring
The prototroch/velum muscle ring has been considered a possible synapomorphy of Pleistomollusca (=bivalves + gastropods) (Kocot et al., 2011). See Wanninger & Haszprunar (2002b) for details.
[242] Enrolling muscle
Character 242: Larva: Enrolling muscle
After Scherholz et al. (2015). Note that a separate character records the occurrence of enrolling musculature in adults.
4.23 Muscles: Enrolling muscle [243]
Character 243: Muscles: Enrolling muscle
After Scherholz et al. (2015). Note that a separate character records the occurrence of enrolling musculature in larvae.
4.24 Larva: Rectus muscle [244]
Character 244: Larva: Rectus muscle
After Scherholz et al. (2015). Note that a separate character records the occurrence of enrolling musculature in adults.
4.25 Muscles: Rectus muscle [245]
Character 245: Muscles: Rectus muscle
After Scherholz et al. (2015). Note that a separate character records the occurrence of enrolling musculature in larvae.
4.26 Larva
[246] Ventrolateral muscle
Character 246: Larva: Ventrolateral muscle
After Scherholz et al. (2015).
[248] Dorsoventral muscles
Character 248: Larva: Dorsoventral muscles
After Scherholz et al. (2015).
4.27 Muscles: Dorsoventral muscles: Medioventral intercrossing [249]
Character 249: Muscles: Dorsoventral muscles: Medioventral intercrossing
“Diagnostic for mollusks and entoprocts alone is the medioventral intercrossing of parts of the dorso-ventral musculature” (Merkel et al., 2015).
4.28 Larva: Foot
[250] Foot
Character 250: Larva: Foot
Foot or neurotroch present in larval stage, whether or not it is also present in mature individuals. Following Wingstrand (1985).
[251] Pedal gland
Character 251: Larva: Foot: Pedal gland
A pedal gland is considered evidence for homology between the molluscan and entoproct foot (Haszprunar & Wanninger, 2008).
[252] Pedal gland: Retained to adulthood
Character 252: Larva: Foot: Pedal gland: Retained to adulthood
Characters 1.13, 1.40 & 2.08 in Scheltema (1993); 114 in Giribet & Wheeler (2002); 1.53 in von Salvini-Plawen & Steiner (1996); 9 in Haszprunar (1996).
[253] Paired
Character 253: Larva: Coelom: Paired
Character 2.02 in Scheltema (1993).
[254] Paried: Includes pericardium
Character 254: Larva: Coelom: Paried: Includes pericardium
Character 1.03 in Scheltema (1993).
[255] Feeding
Character 255: Larva: Feeding
Character 140 in Rouse (1999). See also character 2.66 in von Salvini-Plawen & Steiner (1996); 153 in Giribet & Wheeler (2002).
4.29 Larva: Cilia
[256] Metatroch
Character 256: Larva: Cilia: Metatroch
See characters 129 and 131 in Rouse (1999); 40 in Haszprunar (1996).
A prototroch is the defining character of a trochophore larva; a metatroch is a secondary ciliary ring (Rouse, 1999).
The metatroch is present in a subset of annelids; in Polygordius, it derives from the 3c and 3d micromeres, whereas in molluscs the secondary ciliary band derives frmo 2a, 2b and 2c (Meyer et al., 2010). As such, the structures may not be homologous between molluscs and annelids.
[257] Telotroch
Character 257: Larva: Cilia: Telotroch
A posterior ciliary band. Character 136 in Rouse (1999).
[258] Ciliated food groove
Character 258: Larva: Cilia: Ciliated food groove
Character 132 in Rouse (1999).
[259] Ciliary bands: Downstream
Character 259: Larva: Cilia: Ciliary bands: Downstream
Downstream-collecting ciliary bands of compound cilia on multiciliated cells. Character 31 in Glenner et al. (2004).
[260] Ciliary bands: Upstream
Character 260: Larva: Cilia: Ciliary bands: Upstream
Upstream-collecting ciliary bands with single cilia on monociliated cells. Character 32 in Glenner et al. (2004).
[261] Adoral ciliary band
Character 261: Larva: Cilia: Adoral ciliary band
Characters 1.50, 2.66 and 4.68 in von Salvini-Plawen & Steiner (1996); 2 in Vinther et al. (2008). See also characters 39 in Haszprunar (1996) and 153 in Giribet & Wheeler (2002).
[262] Nerve ring underlying ciliated larval swimming organ
Character 262: Larva: Cilia: Nerve ring underlying ciliated larval swimming organ
Following Wanninger (2009).
4.30 Ciliary ultrastructure
[263] Accessory centriole
Character 263: Ciliary ultrastructure: Accessory centriole
After Lundin, Schander, & Todt (2009).
[264] Aggregation of granules below basal plate
Character 264: Ciliary ultrastructure: Aggregation of granules below basal plate
After Lundin et al. (2009), table 1, which documents “ultrastructural characters of the ciliary apparatus on multiciliated epidermal cells” of adults.
Cilia of non-epidermal cells, such as sensory cilia, gut cilia, and the flagella of spermatozoa, may have derived morphologies that are less phylogenetically instructive (Tyler, 1979), and are not considered herein.
[265] Radiating tubular fibres
Character 265: Ciliary ultrastructure: Basal foot: Radiating tubular fibres
After Lundin et al. (2009). Fibres radiate from the distal end of the basal foot of the cilia in certain taxa.
[266] Basal plate
Character 266: Ciliary ultrastructure: Basal plate
After Lundin et al. (2009). Also termed “dense plate”.
[267] Brush border of microvilli
Character 267: Ciliary ultrastructure: Brush border of microvilli
After Lundin et al. (2009).
[268] Centriolar triplet derivative in basal body
Character 268: Ciliary ultrastructure: Centriolar triplet derivative in basal body
After Lundin et al. (2009).
[269] Ciliary necklace with connecting strands
Character 269: Ciliary ultrastructure: Ciliary necklace with connecting strands
After Lundin et al. (2009).
The ciliary necklace is defined by Gilula & Satir (1972) as “Well-defined rows or strands of membrane particles that encircle the ciliary shaft”. It occurs immediately below the basal plate, and comprises three beaded circles of on the circumference of the cilia membrane.
[270] Monociliate epidermal cells
Character 270: Ciliary ultrastructure: Monociliate epidermal cells
Character 4 in Parry & Caron (2019). Coded as present if compound cilia comprise multiple monociliate cells, even if monociliate cells do not occur individually.
[271] Presence
Character 271: Ciliary ultrastructure: Compound cilia: Presence
After Lundin et al. (2009). Compound cilia are motile structures composed of 10–100 regular cilia used in locomotion or feeding.
[272] Origin
Character 272: Ciliary ultrastructure: Compound cilia: Origin
Character 14 in Glenner et al. (2004). Compound cilia can be produced by the aggregation of cilia from multiple monociliate cells, or from a single cell bearing multiple cilia (Nielsen, 1987).
[273] Glycocalyx ultrastructure
Character 273: Ciliary ultrastructure: Glycocalyx ultrastructure
After Lundin et al. (2009).
[274] Branched
Character 274: Ciliary ultrastructure: Microvilli on epidermal surface: Branched
After Lundin et al. (2009).
[275] Length
Character 275: Ciliary ultrastructure: Vertical ciliary rootlet: Length
After Lundin et al. (2009). The vertical ciliary rootlet is also termed the posterior rootlet.
[276] Shape
Character 276: Ciliary ultrastructure: Vertical ciliary rootlet: Shape
After Lundin et al. (2009). The vertical ciliary rootlet is also termed the posterior rootlet.
[277] Presence
Character 277: Ciliary ultrastructure: Secondary ciliary rootlet: Presence
After Lundin et al. (2009). The secondary ciliary rootlet is also termed the anterior ciliary rootlet.
[278] Length
Character 278: Ciliary ultrastructure: Secondary ciliary rootlet: Length
After Lundin et al. (2009). The secondary ciliary rootlet is also termed the anterior ciliary rootlet.
[279] Shape
Character 279: Ciliary ultrastructure: Secondary ciliary rootlet: Shape
After Lundin et al. (2009). The secondary ciliary rootlet is also termed the anterior ciliary rootlet.
4.31 Nephridia
[280] Podocytes
Character 280: Nephridia: Podocytes
See characters 21 and 28 in Haszprunar (2000); 1.12 in Scheltema (1993).
[281] Rhogocytes
Character 281: Nephridia: Rhogocytes
Pore cells. Character 20 in Haszprunar (2000).
[282] Serve as excretory organs
Character 282: Nephridia: Serve as excretory organs
See character 4.46 in von Salvini-Plawen & Steiner (1996).
[283] Serially repeated
Character 283: Nephridia: Serially repeated
Character 5 in Parry & Caron (2019).
4.32 Cuticle
[286] Layers
Character 286: Cuticle: Layers
Character 1 in Haszprunar (1996).
[287] Composition
Character 287: Cuticle: Composition
Character 2 in Haszprunar & Wanninger (2008).
[288] Fibrous layer with thick fibrils
Character 288: Cuticle: Fibrous layer with thick fibrils
After Borisanova et al. (2015).
[289] Homogeneous layer
Character 289: Cuticle: Homogeneous layer
After Borisanova et al. (2015).
[290] Resilience
Character 290: Cuticle: Resilience
Character 1 in Haszprunar (2000).
[291] Microvilli
Character 291: Cuticle: Microvilli
After Borisanova et al. (2015).
4.33 Muscles
[292] Longitudinal muscle bands
Character 292: Muscles: Longitudinal muscle bands
Character 127 in Parry & Caron (2019).
[293] Circular muscles
Character 293: Muscles: Circular muscles
Character 128 in Parry & Caron (2019). Scherholz et al. (2015) suggest that the ring musculature that forms an element of aculiferan body wall musculature ancestrally formed a continuous muscle layer; it is thus treated as potentially homologous with the circular body wall musculature of annelids.
[294] Hydrostatic muscular system
Character 294: Muscles: Hydrostatic muscular system
Character 92 in Lindgren, Giribet, & Nishiguchi (2004), following Haszprunar (2000). “Gastropods and cephalopods share a ‘hydrostatic muscular system’ (Haszprunar, 1988: 405), wherein the extension of body parts occurs via muscle contraction rather than hemolymphatic pressure. Shimek & Steiner (1997) believe the same is true for the dentalid scaphopod foot”.
[295] Exposed visceral sac with transverse musculature
Character 295: Muscles: Exposed visceral sac with transverse musculature
Combines characters 20 and 21 in Simone (2009).
[296] Cephalic retractors
Character 296: Muscles: Cephalic retractors
After table 1 in Wanninger & Haszprunar (2002b). Adult cephalic retractors denote a differentiated, retractable head. A single pair are found in scaphopods, gastropods and cephalopods.
[297] Cytology
Character 297: Muscles: Cytology
Character 19 in Haszprunar (1996); see also character 13 in Haszprunar (2000).
[298] Histology
Character 298: Muscles: Histology
See character 18 in Haszprunar (1996).
4.34 Nervous system
[299] Orthogonal
Character 299: Nervous system: Orthogonal
Character 14 in Haszprunar (1996). Paired longitudinal nerve cords regularly interconnected by transversal commissures to form a rectangular pattern.
[300] Glial system
Character 300: Nervous system: Glial system
Character 16 in Haszprunar (1996). The Gliointerstitial system interconnects the nervous and muscle systems.
[301] Dorso-terminal sense organ
Character 301: Nervous system: Dorso-terminal sense organ
Corresponds to the molluscan osphradium, considered a conchiferan synapomorphy (???); see von Salvini-Plawen & Steiner (1996), character 30; Ponder & Lindberg (1997), character 100; Giribet & Wheeler (2002) character 143; Haszprunar (2000) character 56; Sasaki, Shigeno, & Tanabe (2010) character 49; Lindgren et al. (2004) character 101.
[302] Statocysts
Character 302: Nervous system: Statocysts
Character 1.33 in von Salvini-Plawen & Steiner (1996); 44 in Lindgren et al. (2004); 99 in Ponder & Lindberg (1997); 55 in Haszprunar (2000).
[303] Nuchal organs
Character 303: Nervous system: Nuchal organs
Character 147 in Parry et al. (2016), 158 in Parry & Caron (2019).
Nuchal organs are chemosensory organs present in almost all polychaetes, and absent in clitellates. They occur as a dorsal pair of ciliated areas on the posterior prostomium (Purschke, 2005). Purschke et al. (1997) points to a number of differences between the nuchal organs of sipunculans and polychaetes, whilst acknowledging the existence of some similarities; Purschke (1997) acknowledge that the case is not closed. We agree that homology between the nuchal organs of sipunculans and annelids is uncertain, but code the structures in a single transformation series to allow the analysis to test the hypothesis of homology.
[304] Buccal nerve ring
Character 304: Nervous system: Buccal nerve ring
Proposed as a synapomorphy of Mollusca + Ectoprocta by Haszprunar & Wanninger (2008) (character 7b), following Wanninger et al. (2007), but overlooking the presence of the structure in polychaetes. Also termed an oral, circumoral or oesophageal nerve ring (Voronezhskaya, Tsitrin, & Nezlin, 2003).
[305] Anterior nerve loop
Character 305: Nervous system: Anterior nerve loop
Character 7c in Haszprunar & Wanninger (2008), following Wanninger et al. (2007). An pre-oral anterior nerve loop is present in aculiferans, Loxosomella and certain annelids (Wanninger et al., 2007).
[306] Suprarectal commissure
Character 306: Nervous system: Suprarectal commissure
Also termed suprarectal loop; viewed as an aculiferan synapomorphy (Scheltema, 1993, character 21). See also von Salvini-Plawen & Steiner (1996) character 28; Waller (1998) character 2e.
[307] Ganglionated
Character 307: Nervous system: Suprarectal commissure: Ganglionated
“The tetraneural nervous system, including the cerebral commissure, lateral and ventral nerve cords, and suprarectal commissure, is more heavily ganglionated in both neomenioids and chaetoderms than in chitons.” (Scheltema, 1993).
[308] Formation of ganglia
Character 308: Nervous system: Formation of ganglia
Character 1.22 in von Salvini-Plawen & Steiner (1996).
of epithelium” – (???).
[309] Presence
Character 309: Nervous system: Cerebral ganglia: Presence
After character 13 in Haszprunar (1996).
[310] Fused
Character 310: Nervous system: Cerebral gangila: Fused
After character 13 in Haszprunar (1996).
[311] Transverse commissures
Character 311: Nervous system: Cerebral ganglia: Transverse commissures
Character 205 in Parry & Caron (2019), who write “a brain with four transverse commissures is present in numerous families of polychaetes and two commissures are present in Sipuncula”.
[312] Transverse commissures: Number
Character 312: Nervous system: Cerebral ganglia: Transverse commissures: Number
Following character 205 in Parry & Caron (2019), who write “a brain with four transverse commissures is present in numerous families of polychaetes and two commissures are present in Sipuncula”. (???) remark “it has been proposed that the ancestral state for […] annelids is four cerebral commissures [but] the ancestral state in the number [of] commissures in annelids is still unclear”. A single commissure characterizes Diasoma.
[313] Serially repeated ganglia
Character 313: Nervous system: Serially repeated ganglia
Character 212 in Parry & Caron (2019).
[314] Serially repeated segmental nerves
Character 314: Nervous system: Serially repeated segmental nerves
Character 213 in Parry & Caron (2019).
[315] Nerve cords
Character 315: Nervous system: Nerve cords
See character 7 in Haszprunar & Wanninger (2008), and discussion in Wanninger (2009).
[316] Medulla
Character 316: Nervous system: Nerve cords: Medulla
Medullary nerve cord are built by a core neuropil and covered by neuronal somata (Faller et al., 2012).
[317] Ventral longitudinal nerves
Character 317: Nervous system: Ventral longitudinal nerves
Character 80 in Glenner et al. (2004); see also character 6 in Vinther et al. (2008).
[318] Ventral cord location
Character 318: Nervous system: Ventral cord location
Character 222 in Parry & Caron (2019).
[319] Ventral cord commissures
Character 319: Nervous system: Ventral cord commissures
Character 223 in Parry & Caron (2019). Refers to commissures between the ventral cords.
4.35 MicroRNA
[320] Brachiopod candidate 1
Character 320: MicroRNA: Brachiopod candidate 1
BC1 in 35.
[321] mir-36
Character 321: MicroRNA: mir-36
[322] mir-76
Character 322: MicroRNA: mir-76
[323] mir-124
Character 323: MicroRNA: mir-124
[324] mir-190
Character 324: MicroRNA: mir-190
[325] mir-219
Character 325: MicroRNA: mir-219
[326] mir-242
Character 326: MicroRNA: mir-242
[327] mir-278
Character 327: MicroRNA: mir-278
[328] mir-1984
Character 328: MicroRNA: mir-1984
[329] mir-1985
Character 329: MicroRNA: mir-1985
[330] mir-1986
Character 330: MicroRNA: mir-1986
[331] mir-1987
Character 331: MicroRNA: mir-1987
[332] mir-1988
Character 332: MicroRNA: mir-1988
[333] mir-1989
Character 333: MicroRNA: mir-1989
[334] mir-1990
Character 334: MicroRNA: mir-1990
[335] mir-1991
Character 335: MicroRNA: mir-1991
[336] mir-1994
Character 336: MicroRNA: mir-1994
[337] mir-1995
Character 337: MicroRNA: mir-1995
[338] mir-1996
Character 338: MicroRNA: mir-1996
[339] mir-1997
Character 339: MicroRNA: mir-1997
[340] mir-1998
Character 340: MicroRNA: mir-1998
[341] mir-1999
Character 341: MicroRNA: mir-1999
[342] mir-2000
Character 342: MicroRNA: mir-2000
[343] mir-2001
Character 343: MicroRNA: mir-2001
[344] mir-2685
Character 344: MicroRNA: mir-2685
[345] mir-2686
Character 345: MicroRNA: mir-2686
[346] mir-2687
Character 346: MicroRNA: mir-2687
[347] mir-2688
Character 347: MicroRNA: mir-2688
[348] mir-2689
Character 348: MicroRNA: mir-2689
[349] mir-2690
Character 349: MicroRNA: mir-2690
[350] mir-2691
Character 350: MicroRNA: mir-2691
[351] mir-2693
Character 351: MicroRNA: mir-2693
[352] mir-2693
Character 352: MicroRNA: mir-2693
[353] mir-2722
Character 353: MicroRNA: mir-2722
[354] mir-5045
Character 354: MicroRNA: mir-5045
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