Character descriptions from Asher, Novacek, and Geisler 2003 J. Mamm. Evolution 10: 131-194.  These descriptions are not intended to contain complete data on distribution of a given character, which are available in print and in a NONA-formatted file at ftp.amnh.org/pub/people/asher.  

Middle ear
1  Stapes obturator foramen (Gaudin et al., 1996):  Cetaceans show a foramen much smaller in size than the surface area covered by the stapes bone, such that multiple foramina of that size could perforate the stapes bone (state 1).  Most other taxa (e.g., Sorex) have a single, large obturator foramen, giving the stapes a ring-shape (state 0).

2  Petrosal-squamosal joint (Fischer and Tassy, 1993):  Trichechus shows a peculiar "barrel-shaped" tegmen tympani, resembling a ball-socket articulation of the anterodorsal petrosal into a broad concavity on the interior of the braincase (state 1).  Fischer and Tassy (1993: 225) point out that this morphology occurs also in fetal elephants; although we note that it does not occur in adults.  In other taxa (e.g., Tenrec), the tegmen tympani is flat (state 0).  

3  Squamosal contact ventral to EAM (Domning et al., 1986: char. 15):  In elephants, the external auditory meatus (EAM) is surrounded by the squamosal, with postglenoid and postympanic portions coming into contact ventral to the ear tube (state 1).  In most other taxa, these squamosal elements have no ventral contact (e.g., Erinaceus, state 0).

4  Presence of fenestra rotundum (Novacek, 1989: char. 73; Fischer and Tassy, 1993):  In adults of most taxa, the round window of the petrosal, or fenestra rotundum, is a discreet aperture within which the foramen for the perilymphatic duct is visible (e.g., Tenrec, state 0).  In contrast, that of adult elephants and sea cows is greatly expanded so as to lose its appearance as an actual apterture; instead, the foramen for the perilymphatic duct is broadly visible on the ventrum of the pars cochlearis (state 1).

5  Fenestra rotundum (Novacek, 1989: char. 42):  In most bats the round window of the petrosal faces posteriorly or posteromedially (state 1); other taxa have a posterolaterally oriented round window (e.g., Tenrec, state 0).  

6  Jugular foramen size (Wible et al., 2001: char. 149):  In most placental mammals, the fenestra cochleae is smaller than the jugular foramen (e.g., Erinaceus, state 1).  In contrast, some Mesozoic therians (e.g., Zalambdalestes) have a jugular foramen and fenestra cochleae of similar size (state 0).  

7  Crista interfenestralis (Wible et al., 2001: char 133; Novacek et al. 1997):  Taxa such as Erinaceus possess an osseous connection between the caudal tympanic process and pars cochlearis of the petrosal, between the fenestrae cochleae and vestibuli (state 1).  In other taxa, the space inbetween the round and oval windows is flat (e.g., Canis, state 0). 

8  Width of basal cochlear turn (Simmons and Geisler, 1998: char. 26):  Microbats show an enlarged inner ear, with the basal turn of the cochlea comprising more than 1/5th of basicranial width (state 1).  Other taxa have a relatively small cochlea that is less than 1/5th basicranial width (e.g., Tenrec, state 0).

9  Anterior promontory:  The cochlea of caviomorph rodents is tightly coiled, with its distal-most turns forming an anteroventrally projecting process on the pars cochlearis (state 1).  Other taxa (e.g., Erinaceus) show a ventrally smooth pars cochlearis (state 0).

10  Petrosal canals (Novacek, 1989: char. 81):  Proximal branches of the internal carotid artery may be enclosed in bony tubes within the petrosal as it enters the middle ear (e.g., Tupaia, state 1).  In other taxa (e.g., Tenrec) the petrosal lacks vascular tubes (state 0).

11  Transpromontorial sulcus (Wible et al., 2001: char. 146):  Many taxa show a groove on the ventrum of the pars cochlearis of the petrosal medial and anterior to fenestra vestibulae (e.g., Tenrec, state 0).  In certain taxa this groove is absent (e.g., Canis, state 1).  When present, this groove is in most cases associated with a transpromontorial internal carotid artery.  However, some taxa with a reduced internal carotid artery (e.g., Lemur) nevertheless show a transpromontorial sulcus associated with other soft-tissue structures, such as the internal carotid nerve.  To ensure parity with fossil taxa for which soft-tissue anatomy is uncertain, we code presence/absence of this sulcus based on osteology alone, regardless of soft tissue associations among living taxa. 

12  Stapedial sulcus (Wible et al., 2001: char. 147):  Many taxa show a groove on the ventrum of the pars cochlearis of the petrosal, just medial to fenestra vestibulae, in which the stapedial artery courses (e.g., Tenrec, state 0).  In certain taxa this groove is absent (e.g., Canis, state 1).  In all known extant taxa this groove is associated with the proximal stapedial artery; we therefore assume this structure in fossil taxa indicates the course of this artery.

13  Piriform fenestra (MacPhee et al., 1988: char. 9; Asher, 1999: char. 2):  This fenestra is present when the petrosal, alisphenoid, squamosal, and/or ectotympanic fail to ossify anterior to the promontory in the roof of the middle ear in a fully grown individual (e.g., Sorex, state 1).  Adults of many taxa have a solid tympanic roof anterior to the middle ear promontory (e.g., Erinaceus, state 0).

14  Petrosal pachyostosis (Geisler and Luo, 1998):  Cetaceans and sirenians have petrosals composed of highly dense, heavy, and thick endochondral bone (state 1).  Other taxa have petrosals that are lighter and less durable (state 0).

15  Pneumatized tegmen tympani (Cifelli, 1982; Novacek, 1989: char. 59):  This character state applies when the petrosal contribution to the roof of the middle ear chamber is thickened by the presense of numerous air cells (as in humans; state 1).  Most taxa have a thin, laminar petrosal in the auditory roof (e.g., Erinaceus, state 0).

16  Pneumatized mastoid:  As for the tegmen tympani, the posteroventral exposure of the petrosal on the basicranium (i.e., the mastoid) may be thickened and filled with air cells (e.g., Macaca, state 1).  More often the mastoid region of the petrosal is laminar (e.g., Tenrec, state 0).
 
17  Ventral process of tegmen tympani (Wible and Novacek, 1988):  Some bats show a ventrally projecting process of the petrosal, forming part of the tympanic roof's anterolateral wall (state 1).  In other taxa (e.g., Orycteropus) the tegmen tympani is ventrally flat (state 0). 

18  Epitympanic sinus (MacPhee, 1994: char. 14):  Certain taxa show an enlarged epitympanic space that may house hypertrophied middle ear ossicles (e.g., Amblysomus; state 1), although this is not necessarily the case, as discussed by MacPhee (1994) and van der Klaauw (1931).  Most taxa show instead a recess that doesn't greatly increase the volume of the tympanic cavity, and is either continuous with, or only slightly recessed from, other parts of the middle ear (e.g., Lemur; state 0).

19  Basisphenoid bulla (Novacek, 1986: char. 49, MacPhee et al., 1988: char. 3, Asher, 1999: char. 1):  The anterior wall of the auditory bulla in hedgehogs is composed of a posteroventrally expansive flange of the basisphenoid (state 1).  Most other taxa (e.g., Sorex) show no basisphenoid flange at the anterior margin of the middle ear (state 0).  

20  Alisphenoid bulla (Novacek, 1989: char. 10):  Didelphis shows a pronounced flange of alisphenoid which forms the anterior wall of the auditory bulla (state 1).  This flange corresponds in structure and relationships to the entoglenoid process of other mammals, although the latter does not necessarily comprise a major component of the auditory bulla.  In most taxa (e.g., Sorex) the alisphenoid does not contribute to the anterior wall of the bulla (state 0).  

21  Basioccipital bulla (Thewissen, 1994: char. 14; Geisler and Luo, 1998: char. 21):  Tursiops and Megaptera show a large flange of the basioccipital that is medial to the auditory bulla (state 1).  In other taxa (e.g., Lama) the basioccipital is flat, without epitympanic wings (state 0).

22  Caudal tympanic process of the petrosal:  (Novacek, 1986: char. 55; MacPhee et al., 1988: char. 2):  This outgrowth from the posterior part of the petrosal may be absent or cover only the fenestra cochleae ventrally (e.g., Tenrec, state 0), or it may be larger and shield the fenestra cochleae and the entrance of the internal carotid artery as it enters the middle ear, contributing to the wall of the ossified auditory bulla (e.g., Tarsius; state 1).  Our coding differs slightly from that of other authors.  MacPhee (1994) coded Hyopsodus, Manis, Phenacodus, Plesiorycteropus, and Procavia as "present" for this character, accurately recognizing that all show some sort of process at the posteroventral margin of the petrosal, adjacent to the fenestra cochleae.  However, all of these taxa are coded here as state "0" (which, as pointed out previously, has no necessary implication regarding polarity) based on the fact that, although present, it does not comprise a major component of the ossified auditory bulla.  For the same reason, we also code Ukhaatherium as "0" even though Novacek et al. (1997) discussed this structure as "pronounced."

23  Rostral tympanic process of petrosal (MacPhee et al., 1988: char. 1; Asher, 1999: char. 4):  A ventromedial flange of petrosal may be present, extending up to the ventral apex of the promontory, contributing to the entrance foramen for the internal carotid in the posterior bulla, and/or articulating with the basisphenoid (e.g., Elephantulus, state 1).  Alternatively, the petrosal may exhibit a medial process that either does not extend to the apex of the promontory or is absent altogether (e.g., Tenrec, state 0).

24  Ectotympanic exposure (Ross et al., 1998: char. 196; Asher, 1999: char. 8):  In most taxa (e.g., Erinaceus) the ectotympanic is broadly visible laterally and ventrally (state 0).  In lemurid primates, Tupaia, and Leptictis it is occluded by other middle ear elements, such as the entotympic or petrosal (state 1).

25  Ectotympanic shape (Wyss and Flynn, 1993: char. 18; Asher, 1999: char. 8):  The ectotympanic may be thin and ringlike (e.g., Sorex, state 1), or expanded mediolaterally, possibly forming much of the bulla and/or an elongate tube leading to the external auditory meatus (e.g, Tarsius, state 1).  In some bats and Zalambdalestes, the ectotympanic does not comprise part of an ossified auditory bulla, but is expanded from the thin and ringlike state.  We therefore code these taxa as state "1."

26  Ectotympanic involucrum (Thewissen, 1994: char. 15; Luo, 1998):  In taxa that possess a mediolaterally expanded ectotympanic bulla, its medial edge is usually thin and continuous with other laminar bones of the auditory bulla (e.g., Macaca; state 0).  Cetaceans, on the other hand, have a thick, pachyostotic medial edge of the ectotympanic that curves dorsally, forming an involucrum (state 1).

27  Accessory external auditory meatus:  Caviomorph rodents show a ventrally projecting extension to their external auditory meatus within the substance of the ectotympanic bone (state 1).  Other taxa show only a single, roughly oval opening to the EAM (e.g., Canis, state 0).  

28  Tympanic annulus (Luo and Gingerich, 1999: character 38):  Unlike other mammals, cetaceans lack a tympanic membrane attached to the ectotympanic bone (state 1).  More commonly (e.g., Canis) this membrane is present and inputs sound to the ossicular chain (state 0).

29  Entotympanic (Novacek, 1977; MacPhee, 1979; Novacek, 1986: char. 47; MacPhee et al., 1988: char. 7):  Many taxa examined here (e.g., Tupaia) show an ossified auditory bulla composed of one or more "entotympanic" ossifications, which are independent of the ectotympanic, petrosal, basi- and alisphenoid bones (state 1).  Alternatively, the entotympanic is small or absent and does not contribute to an ossified auditory bulla (e.g., Macaca, state 0).  Bats and Amblysomus have entotympanic ossifications (Simmons, 1995; MacPhee and Novacek, 1993); however, in neither case does the entotympanic comprise a major part of the auditory bulla in these taxa, and therefore is coded in this study as state "0."

Basicranium
30  Mastoid exposure (Novacek, 1989: char. 60; Asher, 1999: char. 17):  The posterolateral aspect of the mammalian skull is typically defined by an exposed mastoid portion of the petrosal, comprising part of the braincase located between the squamosal and occipital (e.g., Erinaceus, state 0).  Hyraxes are one of a few groups in which the mastoid is not exposed on the external braincase wall (state 1).  In sea cows, the mastoid is occluded inferiorly, but may appear dorsally between the occipital and squamosal (Novacek and Wyss, 1986: fig. 6).  We follow Novacek and Wyss (1986) in coding sea cows as having an inferiorly occluded mastoid. 

31  Dorsal mastoid exposure:  The dorsal part of the petrosal, housing part of the inner ear, may be best exposed on the posterior aspect of the skull, posterior to the nuchal crest (e.g., Didelphis, state 0), or it may be located anterior to nuchal muscle scars and appear broadest when viewed laterally (e.g., Microgale, state 1)

32  Foramen ovale (Novacek, 1989: char. 34; Gaudin et al., 1996):  Tenrec shows a foramen ovale completely enclosed within the alisphenoid (state 0), whereas in other taxa this opening comprises a notch within the alisphenoid, with a posterior border composed of middle ear elements (e.g., Cavia, state 1).  As discussed by Gaudin et al. (1996), we code several taxa as polymorphic for this character (e.g., Didelphis).

33  Alisphenoid canal (Wyss and Flynn, 1993: char. 12; Asher, 1999: char. 10):  Many taxa (e.g., Rattus) show a foramen immediately anterior to foramen ovale that leads into the cavum epiptericum (state 0; see Cartmill and MacPhee, 1980: fig. 2). This foramen typically contains the inferior stapedial ramus, or "maxillary artery" as a branch of the external carotid, en route to its supply of the jaw and face.  Some taxa (e.g., Didelphis) lack this vascular aperture anterior to foramen ovale (state 1).

34  Anterior opening of alisphenoid canal (Asher, 1999: char. 10):  When present, the alisphenoid canal may have an anterior opening lateral to the sphenorbital fissure, as in Cavia (state 0); or it may be "elongate" and anteriorly continuous with the exit foramen(ina) of the ophthalmic and/or maxillary trigeminal divisions (e.g., Tenrec, state 1; see Butler, 1988: 119). 

35  Maxilla-squamosal articulation:  Cavia possesses a posteriorly extensive maxilla that articulates with the squamosal inferior to the sphenorbital fissure (state 1).  In other taxa the posterior maxilla does not articulate with the squamosal (e.g., Rattus, state 0).  

36  Ectopterygoid (Novacek, 1986: char. 36; Thewissen and Domning, 1992: char. 23; Asher, 1999: char. 14):  Most taxa possess a single pair of laminae made up primarily of the sphenoid and palatine bones that laterally border the nasal choana (e.g., Canis, state 0).  Other taxa possess prominent ectopterygoid processes of the alisphenoid that form a pair of laminae on each side of the choana, and create a scaphoid fossa of varying size for attachment of pterygoid musculature (e.g., Homo, state 1)

37  Basisphenoid pit (Frost et al., 1991: char. 30):  At the dorsal and posterior margin of the nasopharynx, medial and slightly anterior to the middle ear, a marked concavity (when viewed ventrally) may occur in the basisphenoid (e.g., Tenrec, state 1).  Alternatively, most taxa examined here possess a flat basisphenoid continuous with the basioccipital (e.g, Didelphis, state 0).

38  Posterior lacerate foramen (Novacek, 1986: char. 67; Thewissen and Domning, 1992: char. 31):  Some bats possess an anteroposteriorly elongate fenestra along the medial margin of the promontory, resulting from reduced medial contact of the petrosal with the basisphenoid and basioccipital, that serves as a common exit point for cranial nerves 9, 10, 11, and the jugular vein, and may coalesce with the hypoglossal foramen (state 1).  In other taxa (e.g., Erinaceus) the petrosal articulates medially with the basisphenoid and/or basioccipital (state 0).

39  Condyloid foramina (Novacek, 1986: char. 53):  Didelphis, Macropus, and occasional placental taxa show multiple perforations in their basioccipital, corresponding to hypoglossal foramina (state 2).  This contrasts to the more common state of a single hypoglossal foramen piercing each occipital condyle (e.g., Erinaceus; state 1).  In a few taxa (e.g., extant cetaceans; see Luo and Gingerich, 1999: 41) no foramina are present in the vincinity of the occipital condyles (state 0).

40  Ventral exposure of basisphenoid (Barnes, 1990):  Adult Tursiops and Megaptera specimens show a posteriorly elongate vomer that occludes all or most of the basisphenoid ventrally (state 1).  In other mammals the vomer lies far anterior to the ventral exposure of the basisphenoid (state 0).  In Tamandua the pterygoids form a posteriorly elongate secondary palate that ventrally covers the basisphenoid (state 2).

Braincase
41  Mastoid exposure in braincase:  Cetaceans are remarkable in lacking intra-braincase exposure of the petromastoid (state 1); instead, the petrosal is separated from the braincase by extensions of the parietal and basioccipital.  All other mammals examined here have fairly broad exposure of the petrosal within the middle and/or posterior cranial fossae (state 0).

42  Subarcuate fossa (Novacek, 1989: char. 43):  Certain taxa lack a bony fossa within the part of the petrosal housing the superior semicircular canal into which the paraflocculus of the cerebellum protrudes (e.g., Homo, state 1).  In most other taxa the superior semicircular canal defines a depression visible from the interior of the skull (e.g., Erinaceus; state 0).

43  Dorsum of the subarcuate fossa (Novacek, 1989: char. 43):  The superior semicircular canal is freestanding within the braincase in some bats, with the the dorsal apex of the superior semicircular canal partially or wholly unconnected to the lateral wall of the braincase (state 1).  In other taxa the superior margin of the subarcuate fossa is flush with the cranial sidewall (state 0). 

44  Tentorium cerebelli (Wyss and Flynn, 1993; Shoshani and McKenna, 1998: char. 261):  Felis has a hyper-ossified division between the posterior (housing the cerebellum) and middle cranial fossae, consisting of bony laminae extending dorsal to the intracranially exposed petrosals (state 1).  Other taxa (including Canis) lack ossified laminae extending dorsal to the petrosals, dividing the space within the braincase (state 0).

45  Sinus canal (Novacek, 1986: char. 38):  Many taxa (e.g., Tenrec) possess an anteroposteriorly running canal that traverses the interior of the braincase dorsal to the petrosal, which houses the superior ramus of the stapedial artery (state 1).  Mammals such as Trichechus lack a sinus canal (state 0).

46  Dorsum sellae (Novacek, 1986: char. 37):  In humans, the posterior margin of the hypophyseal fossa is well defined posteriorly by the posterior clinoid processes (state 1).  The dorsum sellae in other mammals is largely continuous with the clivus (i.e., dorsum of the basisphenoid and basioccipital) and lacks prominent posterior clinoid processes (e.g., Pteropus; state 0).  

47  Crista galli (Novacek, 1986: char. 5): Some mammals possess a plate of bone projecting dorsally along the midline of the cribriform plate (e.g., Procavia, state 0).  Insectivorans lack this process, having instead a flat or depressed region along the midline of the cribriform plate (e.g., Erinaceus, state 1).

Orbitotemporal region
48  Foramen rotundum (MacPhee, 1994: char. 7):  Most taxa (e.g., Erinaceus) show a single opening, the sphenorbital fissure, that serves as the exit point for the ophthalmic and maxillary divisions of the trigeminal nerve (state 0).  Carnivorans, primates, and certain other taxa show a subdivided sphenorbital fissure containing a distinct foramen rotundum for exit of the maxillary trigeminal division (state 1).

49  Alisphenoid spine:  Artibeus shows an elongate, anteriorly directed process on the bridge of bone separating the exit foramina for the ophthalmic and maxillary divisions of the trigeminal (state 1).  In other taxa that have a distinct foramen rotundum (e.g., Felis), the bridge of bone separating it from the orbital fissure is anteriorly flat (state 0).

50  Optic foramen (MacPhee, 1994: char. 1; Novacek, 1989: char. 25; Asher, 1999: char. 18):  Most taxa (e.g., Felis) possess a distinct foramen and/or canal for passage of the optic nerve from the braincase to the orbit (state 1).  Several taxa (e.g., Didelphis) lack a distinct canal through which the optic nerve passes (state 0).  

51  Optic foramen size (MacPhee, 1994: char. 1; Asher, 1999: char. 18):  Among taxa that possess an optic foramen, its caliber may be similar in size to foramen ovale and (when present) rotundum (e.g., Homo; state 0); or it may be reduced and a fraction of the size of trigeminal exit foramina (e.g., Tenrec; state 1).

52  Suboptic foramen (Butler, 1956: 473):  In Elephantulus, an opening is evident ventral to the optic foramina, passing transversely through the sphenoid, ventral to the sella turcica, that connects the sphenorbital fissures on each side of the skull (state 1).  In most other taxa this communication between the opposite orbitotemporal regions is not apparent anterior to the lateral margin of the sphenorbital fissure (e.g., Erinaceus, state 0).  It is possible, through the interorbital fenestra (see below) created by large optic foramina and/or closely situated orbits of certain taxa (e.g., Sylvilagus), to view the opposite orbitotemporal region; however, this is not correlated with possession of an anteriorly placed suboptic foramen that connects both orbitotemporal fossae.

53  Interorbital fenestra: Lagomorphs and certain other taxa possess large and closely situated optic foramina that coalesce into a single opening that connects the orbits on each side of the skull, forming a fenestra between the two (state 1).  In most other taxa (e.g., Erinaceus) the two optic foramina are widely separated (state 0).

54  Ethmoid foramen (Thewissen and Domning, 1992: char. 20).  Following McDowell (1958: figs. 10, 35, 36), MacPhee (1994: figs. 6, 8), Wible and Rougier (2000), and Asher (1999, 2001), we regard this structure as a foramen in the frontal bone connecting an intracranial sinus of the anterior braincase with the orbit and typically serving as a conduit for venous drainage and ethmoidal arteries and nerves.  Thewissen (1989) rightly pointed out that some confusion exists in regards to "ethmoid" vs. "frontal diploic" foramina, and that the human foramen cecum is not homologous with either structure.  As illustrated for several taxa (e.g., Solenodon) by MacPhee (1994: fig. 6), "ethmoid" and "frontal diploic" foramina are occasionally situated adjacent to one another, but may be distinguished in certain taxa (e.g., Tamandua; see MacPhee 1994: fig. 6) that show frontal diploic foramina dorsally in the orbit and ethmoid foramina ventrally.  We use the name "ethmoid foramen" for such ventrally occurring foramina in the frontal connecting the frontal sinus and orbit.  
; Possibly due to this unclear distinction between "frontal diploic" and "ethmoid" foramina, Thewissen and Domining (1992) coded an ethmoid foramen as absent in hyracoids.  However, we have identified in Procavia an apterture in the frontal fitting the above description (see also MacPhee, 1994: fig. 6).  Similarly, we believe that the "frontal diploic" foramen illustrated by Thewissen (1990: fig. 53) in Phenacodus qualifies as a primary homology with the ethmoid foramen of other taxa; and we have coded it accordingly (i.e., as "present," state 0).  Some (but not all) taxa with reduced olfaction (e.g., Trichechus) show a frontal sinus without ventrolateral egress to the orbit via the frontal bone, and are coded here as lacking an ethmoid foramen (state 1).

55  Tuber maxillaris (Novacek, 1989: char. 77; Fischer and Tassy, 1993: char. 67):  The posterodorsal margin of the maxilla may present a bulbous, dorsally convex ridge in the floor of the orbit containing roots of the posterior cheek teeth (e.g., Sus, state 1).  In most taxa the floor of the orbit is flat (e.g., Didelphis, state 0).  

56  Glenoid position (Novacek, 1989: char. 51):  The jaw joint is situated lateral to and in the same transverse plane as the pars cochlearis of the petrosal in most taxa (e.g., Canis, state 0).  In some cases, the mandibular glenoid fossa is located superior to the petrosal (e.g., Amblysomus, state 1) and external auditory meatus.  

57  Glenoid shape (Novacek, 1986: char. 40):  Rodents, lagomorphs and certain other mammals have a glenoid fossa for the mandible that is elongate in an anteroposterior plane, permitting considerable A-P movement of the jaw during mastication (state 1).  Most other mammals (e.g., Felis) show glenoid fossae that are wider in a mediolateral plane (state 0).

58  Postglenoid foramen (Novacek et al., 1997):  Ukhaatherium and Zalambdalestes possess a glenoid articular surface for the dentary that is interrupted at its posterior margin by the postglenoid foramen (state 1).  In most other taxa the glenoid articular surface is smooth and imperforate (e.g., Canis, state 0).  

59  Postglenoid process:  Canis shows an enlarged, ventrally projecting process of the squamosal that posteriorly buttresses the mandibular condyle of the dentary (state 1).  Several taxa (e.g., Echinops) lack this process (state 0); and several rodents (e.g., Hydrochaeris) show a ventrally projecting process of the squamosal that is anteroposteriorly oriented and articulates medial to the mandibular condyle (state 2).

60  Ento-postglenoid processes (Novacek et al., 1997):  Ukhaatherium and Zalambdalestes possess a continuous ridge of alisphenoid and squamosal that connects the entoglenoid and postglenoid processes (state 1).  In most other taxa (e.g., Didelphis) these two processes are separate (state 0).  

61  Entoglenoid process (Novacek, 1986: char. 39, MacPhee et al., 1988: char. 6; Asher, 1999: char. 22; McDowell, 1958: 143-144, 170):  At the posteromedial margin of the glenoid fossa for the mandible, adjacent to foramen ovale, medial to the postglenoid foramen and anterior to the petrosal, a ventrally projecting process comprised of the alisphenoid and/or squamosal may be present that posteriorly supports the mandibular condyle when occluded in the glenoid fossa.  This is the entoglenoid process (e.g., Tenrec, state 1).  In most taxa, the entoglenoid process does not support the mandibular condyle posteriorly (e.g., Didelphis; state 0).  Ukhaatherium resembles Leptictis and certain erinaceomorph insectivorans in showing both entoglenoid and postglenoid processes (Novacek et al., 1997).  However, the postglenoid process in these taxa provides posterior support for the occluded mandibular condyle, not the entoglenoid process.  Hence, we code all three taxa as state "0" for this character.

62  Zygomatic arch (Asher, 1999: char. 26): Many insectivorans have an incomplete zygomatic arch lateral to the mandibular coronoid process (e.g., Tenrec, state 1). Most other mammals have a robust zygomatic process (e.g., Canis, state 0). In Megaptera, the maxilla does not participate in the zygomatic arch; rather, the frontal comprises the anterior component of the arch (state 2).

63  Jugal in glenoid (Novacek, 1989: char. 61; Novacek and Wyss, 1986: 279):  Several taxa show a posteriorly extensive jugal component in the zygomatic arch that posteriorly contacts the articular surface of the glenoid fossa (e.g., Procavia, state 0).  In contrast, primates, bats, and certain other taxa show a jugal that is much more restricted posteriorly, terminating well anterior to the glenoid fossa (e.g., Homo, state 1). 

64  Anterior jugal (Court, 1995: char. 15):  In Didelphis, the anterior margin of the jugal bone is coincident with the anterior orbit, and articulates with the lacrimal (state 0).  In rodents, on the other hand, the anterior jugal is restricted to the zygomatic arch, and does not reach the anterior margin of the orbit (state 1).

65  Zygomatic process of squamosal (Novacek, 1989: char. 67; Novacek and Wyss, 1986: 281):  Typically among mammals, the squamosal contribution to the zygomatic arch is a narrow splinter, tapering to a point as it extends anteriorly (e.g., Erinaceus, state 1).  Some marsupials, sea cows, elephants, and ungulates show instead a squamosal contribution to the zygoma that is dorsoventrally expansive anterior to the posterior root of the zygoma (state 0).

66  Postorbital bar (Ross et al., 1998: char. 206):  Several taxa show extensions of the frontal and/or jugal bones that converge posterior to the orbit, defining an eye socket surrounded by bone (e.g., Lemur, state 1).  In other taxa the orbit is posteriorly open and osteologically continuous with the temporal fossa (e.g., Didelphis, state 0).  

67  Postorbital septum (Ross et al., 1998: char. 206):  Anthropoid primates are osteologically remarkable in possessing an ossified septum, posterior to the orbit, in which the alisphenoid and jugal bones articulate.  The frontal bone may also contribute to the septum (state 1; see Ross, 1995).  Other taxa (e.g., Felis) lack approximation of the jugal and alisphenoid and the consequent osseous barrier between the temporal and orbital fossae (state 0).  We note that previous researchers have disputed the homology of the tarsier and anthropoid postorbital septum (e.g., Simons and Rasmussen, 1989), and in one phylogenetic study have even coded tarsiers as lacking a septum (Beard and MacPhee, 1994) based on differences in the relative contribution of various elements to the septum.  We recognize that Tarsius has a smaller jugal (or "zygomatic") component to its septum than anthropoids; but it is still sufficiently expanded so as to articulate with the alisphenoid bone (Cartmill, 1980), as it does in anthropoids, and in contrast to all other mammals observed in this study.  Hence, we code tarsiers as state "1" for this character.

68  Interorbital distance:  Most primates possess orbits that are extremely convergent, with the nasals and frontal forming an interorbital septum that is much narrower than the transverse breadth of each orbit (state 1).  In contrast, other mammals have separated orbits, such that the space inbetween is similar in transverse length as that of each individual orbit (e.g., Procavia; state 0).

69  Relative size of the lacrimal facial process:  The anterior extent of the lacrimal bone is usually confined to the orbital margin (e.g., Felis; state 0), with a facial process smaller than the orbital process.  In contrast, certain taxa (e.g., Tragelaphus) show a very elongate facial process of the lacrimal that contributes extensively to the rostrum and is larger than the orbital process of the lacrimal (state 1).  This coding differs slightly from that used by Novacek (1986: char. 22), who coded the presence of a facial lacrimal process independently of its size in relation to the orbital lacrimal process.  

70  Lacrimal tubercle (Novacek, 1986: char. 24):  Procavia is notable in possessing a freestanding flange of the lacrimal that projects posteriorly into the orbit (state 1).  In other taxa the anterior orbital margin is flat (e.g., Canis; state 0).  

71  Lacrimal foramen:  Sutures outlining an independent ossification at the anterior orbital margin containing the proximal aperture of the nasolacrimal duct (i.e., lacrimal foramen) are visible in most mammals (e.g., Didelphis; state 0).  In certain groups (e.g., Trichechus) the lacrimal foramen is not present in the vincinity of the anterior orbit (state 1).

72  Lacrimal foramen opening (Novacek, 1986: char. 23):  In taxa that possess a lacrimal foramen, it may open up along the posterior margin of the bridge of bone that forms the infraorbital canal posteriorly into the orbit, and be hidden from lateral view (e.g., Didelphis, state 0).  Alternatively, it may open in a lateral direction and be clearly visible in lateral view (e.g., Tenrec, state 1).

73  Frontal in orbit (Novacek, 1989: char. 26):  In the medial orbital wall, the palatine and frontal bones are often separated by exposed parts of the ethmoid, sphenoid, and/or maxilla (e.g., Homo, state 0).  Felis and Lemur (Cartmill, 1978) are two of several taxa in which the frontal and palatine meet in the medial orbital wall (state 1).

74  Jugal in orbit (Fleagle, 1999):  New world monkeys show an expanded jugal contributing to the orbital wall that extends posteriorly to articulate with the parietal (state 1).  In other taxa (e.g., Homo) the jugal is restricted anteriorly, with such bones as the sphenoid and/or palatine separating the jugal and parietal (state 0).

75  Maxilla in orbit (Novacek, 1986: char. 14; Asher, 1999: char. 25):  Many insectivoran-grade taxa have been noted to possess an expanded maxillary contribution to the medial orbital mosaic, extending posteriorly past the maxillary toothrow and superiorly to a level even with the upper margin of the infraorbital canal, and contributing to the separation of the palatine from more dorsal components of the orbital mosaic such as the frontal and lacrimal (state 1; see Butler, 1988; MacPhee and Novacek, 1993; Giere, 2002).  Other taxa (e.g., Felis) show an orbital mosaic without a major contribution from the maxilla, consisting instead of the palatine, lacrimal, frontal, and/or ethmoid bones, with contact between the palatine and more dorsal orbital bones (state 0).

Rostrum:
76  Premaxillary-frontal contact (Novacek, 1989: char. 47):  Rodents and lagomorphs are remarkable among mammals in possessing a posteriorly extensive premaxilla that articulates with the frontal (state 1).  In most other taxa (e.g., Homo), the premaxilla is relatively smaller and articulates only with the maxilla and/or nasals (state 0).

77  Anterior nasals:  The anterior third of the nasal bones of perissodactyls projects freely into space without sutures to the maxilla or premaxilla (state 1).  Other animals (e.g., Procavia) show nasal bones sutured to the maxilla and/or premaxilla throughout most of their length (state 0).

78  Posterior nasals (Novacek, 1986: char. 2):  In this region two conditions are generally seen among mammals: nasals that are transversly wider posteriorly than anteriorly (e.g., Procavia, state 1), or that become narrower from anterior to posterior (e.g., Erinaceus; state 0).  In many cases state "1" corresponds with a nasal-lacrimal articulation, but this is not always so.

79  Metopic suture (Ross et al., 1998: char. 213):  The frontal of adult anthropoids is fused at the midline and shows no suture dividing it bilaterally (state 1).  Adults of other taxa (e.g., Rattus) show a prominent midline suture dividing the frontal into two halves (state 0).

80  Maxillary fenestration (Meng and Wyss, 2001: char. 66):  Some rodents and lagomorphs show a large fenestra within or adjacent to the maxilla near the medial wall of the infraorbital canal (state 1).  Sylvilagus (and other leporids) shows a remarkable series of trabeculae in this area (state 2).  Most other taxa (e.g., Macropus) have solid maxillae medial to the infraorbital canal (state 0).

81  Infraorbital canal length (Asher, 1999: char. 29):  The length of the canal through which branches of the maxillary division of the trigeminal nerve reach the anterior face varies greatly among mammals.  In Equus, the canal is many times longer than the width of the infraorbital canal's anterior aperture (state 0); in Felis, the canal is similar in length as the anterior aperture width (state 1).  Many rodents have unusually large anterior openings of the infraorbital canal, modified for passage of masticatory muscles; nevertheless, all rodents examined in this study possess short canals, no greater in length as that observed in Felis.

82  Infraorbital canal anterior aperture:  As just noted, several rodents (e.g., Cavia) show an anteriorly expanded infraorbital foramen, similar in breadth to the external nares (state 1).  This aperture in other taxa is much smaller than the external nares, resembling instead other foramina associated with the trigeminal, such as foramen ovale (e.g., Didelphis, state 0).

83  Orbit position (Tassy, 1981):  Sea cows and elephants possess an anteriorly displaced orbit, situated anterodorsal to the cheek teeth (state 1).  In most other taxa (e.g., Canis) the orbits are dorsal to the posterior alveolar part of the maxilla (state 0).  In cetaceans, the orbits are located well posterior to the alveolar part of the maxilla (state 2).  

84  External nares:  Several taxa depart from the condition displayed among most mammals (e.g., Canis) in which the external nares are situated at the anterior extreme of the rostrum (state 0).  In sea cows, the external nares are located dorsal to the cheek teeth (state 1); and in cetaceans, the external nares are located posterior to entire alveolar region of the maxilla (state 2).

Palate
85  Postpalatine spine (Novacek, 1986: char. 18):  The posterior margin of the palate may be smooth, without any tubercle at its midpoint (e.g., Didelphis, state 0), or it may possess a large process extending caudally or caudo-dorsally at its midpoint (e.g., Erinaceus, state 1).

86  Posterior hard palate (Novacek, 1986: char. 17):  Considerable variability exists in the posterior terminus of the hard palate.  In Sylvilagus it is located anterior to the posterior cheek teeth (state 2); in Canis it is roughly even with the posterior cheek teeth (state 1); and in Didelphis it is located posterior to the rear-most cheek teeth (state 0).

87  Palatal notch:  Independent of the position of the posterior hard palate, the palate medial to the posterior molars and lateral to the ectopterygoid may be anteriorly excavated, such that the palate lateral to each ectopterygoid plate is concave posteriorly (e.g., Tadarida, state 1).  In other taxa the palate between the posterior molars and ectopterygoid is solid (e.g., Homo, state 0).  

88  Posteroventral maxilla (Asher, 1999: char. 15; McDowell, 1958: 184):  The maxilla posterior to the upper toothrow is not extensive in most taxa (e.g., Erinaceus, state 0).  Echinops, on the other hand, shows a process of the maxilla extending well posterior to the upper toothrow along the inferior margin of each ectopterygoid lamina (state 1).

89  Palatal exposure of the premaxilla (Novacek, 1989: char. 50):  Rodents and lagomorphs show an enlarged premaxillary component to the palate, approximating the size of the maxillary palatal component (state 1).  In other taxa (e.g., Procavia) the palatal exposure of the premaxilla is much smaller than that of the maxilla (state 0).

90  Incisive foramen presence (Thewissen, 1994: char. 32):  Cetaceans lack a well-defined foramen in the premaxilla that connects the nasal and oral cavities (state 1).  In other taxa, the premaxilla is perforated by one or more incisive foramina (e.g., Echinops; state 0).

91  Incisive foramina number (Simmons, 1995: char. 2; Thewissen and Domning, 1992: char. 18):  Foramina in the anterior palate transmitting the nasopalatine ducts are typically paired and exposed on the ventrum of each half of the premaxilla (e.g., Felis, state 0).  In several taxa (e.g., Homo), this apterture appears as a single opening on the ventrum of the palate (state 1).

92  Incisive foramina shape:  The incisive foramen/ina may be small and oval in shape (e.g., Homo; state 0) or elongate (e.g., Didelphis; state 1). 

93  Palatal fenestrae:  Several taxa show large apertures in the palate.  In Didelphis these are most conspicuous posteriorly, between the molar toothrows (state 1); in Sylvilagus they are situated anteriorly, adjacent to the incisive foramina (state 2).  Taxa such as Felis show a solid, unfenestrated palate (state 0).

Dentition
94  Dental reduction:  Adult specimens of Tamandua and Manis completely lack calcified teeth (state 1); and Megaptera possesses baleen in lieu of teeth (state 2).  Adults of other taxa show fully erupted teeth (e.g., Amblysomus; state 0), the diversity of which is partially represented in the following characters.  

95  Incisor enamel:  Rodents show an unusual condition in which the enamel of the anterior incisors is restricted to a band on the anterior margin of the tooth (state 1).  In other mammals enamel is distributed more evenly around both deciduous and adult teeth (e.g., Homo; state 0).  

96  Number of incisors (Asher, 1999: char. 38):  The number of teeth on each half of the premaxilla ranges from 5 (e.g., Didelphis, state 5) to 0 (e.g., Orycteropus, state 0), with intermediate states numbered accordingly.  

97  Post premaxillary diastema:  Several taxa (e.g., Rattus) show a large gap between the premaxillary dentition and cheekteeth, double in length as the entire molar toothrow (state 1).  This contrasts with the more evenly spaced dentition of most other mammals (e.g., Macaca, state 0).  Some taxa (e.g., Tragelaphus) have an edentulous premaxilla, but are coded as state 1 based on the large size of the gap between the posterior portion of the alveolar premaxilla and the anteriormost maxillary dentition.

98  Incisor growth (Novacek, 1989: char. 54):  In addition to rodents and lagomorphs, Procavia also posseses a continuously growing, hypsodont incisor (state 1).  Other mammals show incisors with determinate growth (e.g., Homo, state 0).

99  Tooth replacement (Novacek, 1989: char. 11):  Among marsupials, only the p4 has a deciduous precursor (state 1).  Placental mammals, in contrast, generally have deciduous precursors for all of their adult antemolar teeth that are shed at an early stage of life (state 1).  In a few mammals (e.g., Sorex), the deciduous dentition fails to calcify altogether (state 2).  In elephants, sea cows, and desmostylians (Vanderhoof, 1937), tooth replacement is a continuous process lasting throughout adult life (state 3).

100  Canine growth (Geisler, 2001: char. 87):  Hippos and pigs possess hypsodont, ever-growing canines (state 1).  Other mammals show canines with determinate growth (e.g., Homo, state 0).

101  Cheektooth enamel (Novacek, 1989: char. 29):  Dasypodids, bradypodids, Manis, and Orycteropus lack a layer enamel on their peg-like teeth (state 1).  Other dentate mammals possess teeth composed of an outer layer of enamel (e.g., Ateles, state 0).

102  Cheektooth orientation:  Cavia is remarkable in showing molar-premolar toothrows that converge anteriorly on the midline of the palate, giving the palatal teeth a V-shape when viewed occlusally (state 1).  In other taxa (e.g., Equus) the lingual cusps of molars on each side of the maxilla run parallel to one another (state 0).

103  Cheektooth growth:  In most taxa (e.g., Homo), molars and premolars show determinate growth, with distinct boundaries between the enamel and dentine at the alveolar boundary of the tooth (state 0).  Certain rodents, lagomorphs, and perissodactyls possess ever-growing, hypsodont molars with enamel extending proximal to the tooth's alveolar base (state 1).

104  Upper P3 presence:  Following dental formulae given by Starck (1995), the upper P3 may be present (state 0) or absent (state 1).

105  Upper P3 crown (Asher, 2000: char. 70):  Typically, the upper P3 is buccolingually narrow and lacks a prominent lingual cusp (e.g., Felis, state 0), or it may appear molariform with prominent lingual cusp(s) (e.g., Equus, state 1).

106  Upper P4 crown (Asher, 2000: char. 71):  Typically, the upper P4 is buccolingually narrow and lacks a prominent lingual cusp (e.g., Didelphis, state 0), or it may appear molariform with prominent lingual cusp(s) (e.g., Erinaceus, state 1).

107  Metacone (Asher, 1999: char. 41):  Most mammals possess a prominent metacone on the posterobuccal aspect of M1 and M2 (e.g., Lemur, state 0).  Other taxa have a reduced or absent metacone (e.g., Tenrec, state 1).

108  Protocone (Asher, 1999: char. 42):  In some taxa the mesiolingual cusp of the upper cheek teeth is restricted to the cingulum and less than half the size of the paracone (e.g., Tenrec, state 1).  In other mammals the protocone is similar in size to the paracone (e.g., Echinosorex, state 0).

109  Molar ectoloph (Radinsky, 1969):  Perissodactyls show a characteristic "pi" shaped series of crests on their upper cheek teeth, with the anteroposterior-running crest on the buccal margin of the molars connecting to two buccolingually-running crests, one located at the anterior margin of the tooth and the other posteriorly (state 1).  In other mammals, these crests are undeveloped and/or do not connect (e.g., Sus, state 0).  

110  Stylar shelf (Novacek, 1989: char. 20; Asher, 2000: char. 79):  When present, the upper cheek teeth may show an elongate stylar region with a distinct stylocone, meso-, and/or metastyles (e.g., Didelphis, state 1).  Alternatively, this region may be reduced, and little or no occlusal surface may be present buccal to the para- and/or metacones (e.g., Ateles, state 0).

111  Molar shearing (Wyss and Flynn, 1993: char. 31):  Carnivorans are unique among mammals in possessing a single pair of teeth specialized for shearing, the carnassial upper P4 and the lower m1 (state 1).  Shear among other mammals is distributed more evenly across tooth positions (e.g., Sorex, state 0).

Jaw and lower dentition
112  Mandible (MacPhee, 1994: char. 31):  Manis and Tamandua possess a vestigial, edentulous, threadlike mandible (state 1).  In other taxa (e.g., Erinaceus) the mandible is robust and capable of supporting considerable masticatory stress (state 0).

113  Mandibular condyle height (Novacek, 1986: char. 72):  Canis shows an inferiorly situated mandibular condyle, positioned roughly in the same transverse plane as the lower dentition and far inferior to the apex of the coronoid process (state 0).  Elephant shrews, in contrast, show a mandibular condyle located superiorly, well above a transverse plane contacting the lower teeth (state 1).

114  Coronoid shape (Meng and Wyss, 2001: char. 70):  In lagomorphs and certain other taxa, the coronoid process is reduced to a small bump anterior to the mandibular condyle (state 1).  In other taxa it comprises a large process with ample surface area for masticatory muscle attachments (e.g., Echinops, state 0).  We do not follow the coding of Novacek (1986: char. 71) who suggested that the mandibular condyle of lagomorphs was a modified coronoid process.  Rather, we follow Meng and Wyss (2001) in coding it as reduced.

115  Coronoid process height:  In most taxa the superior margin of the coronoid process is located above the mandibular condyle (e.g., Felis, state 0); in others (e.g., Cavia) it is inferior to the condyle (state 1).  Note that this character is not entirely correlated with coronoid reduction, as the well-developed coronoid process of certain taxa (e.g., Loxodonta) is situated anteroventral to their mandibular condyle, and the relatively small coronoid process of others (e.g., Cynocephalus) is situated anterodorsal to the condyle.  Because of this apparent independence, taxa with a reduced coronoid process (above) are not coded as "inapplicable" for this character.

116  Jaw angle:  Marsupials have a medially projecting process extending from the posteroinferior margin of the dentary (state 1).  In other mammals, the angle of the jaw is transversely narrow (e.g., Homo; state 0).

117  Fusion of mandibular symphysis (Ross et al., 1998: char. 221):  In adult anthropoid primates, each half of the dentary is fused anteriorly at the midline (state 1).  Most other mammals possess an unfused mandibular symphysis into adulthood (e.g., Tenrec; state 0).

118  Symphysis length:  Sea cows and desmostylians show an anteroposteriorly elongate mandibular symphysis, at least 1/3rd the length of the entire jaw (state 1).  Other mammals have a symphysis that is anteroposteriorly short, well under 1/3rd jaw length (e.g., Homo, state 0).  

119  Ventral lip of mandibular symphysis:  Elephants and sea cows possess an edentate anterior lower jaw with a tapered process extending anteroventrally from the midline (state 1).  Other mammals (e.g., Talpa) have a flat anterior dentary, with no part of the bone extending ventrally at the midline (state 0).

120  Presence of lower m3 (Asher, 2000: char. 89):  Adults of most taxa possess a permanent m3 (e.g., Erinaceus, state 0); in others the m3 is absent (e.g., Canis, state 1).  

121  Talonid basin (Asher, 1999: char. 44):  Lower molars of several taxa may have a talonid with a well defined basin surrounded by ridges comprised of, or continuous with, the entoconid, hypoconid, and/or hypoconulid (e.g., Macaca, state 0).  In other taxa the talonid basin is reduced or altogether absent (e.g., Amblysomus, state 1).


Vertebral column
122  Cervical vertebral centra (O'Leary and Geisler, 1999: char. 88):  Cetaceans and sea cows show antero-posteriorly compressed cervical centra relative to those in the thoracic and lumbar region (state 2).  In other mammals (e.g., Homo), cervical centra are within 50% of the length of thoracic and lumbar centra (state 1).  In Tragelaphus, cervical centra are more than twice the length of thoracic centra (state 0).

123  C2 odontoid presence:  The anterior margin of the axial centrum in cetaceans is relatively flat (state 1), possibly showing a broadly convex emargination, but definitively lacking the pointed, anteriorly projecting odontoid process, similar in length as the centrum itself, shown by other mammals (e.g., Pteropus, state 0).

124  C2 odontoid shape:  The dens or odontoid process of the axis in several ungulate taxa (e.g., Tragelaphus) has a broad origin, covering approximately the 180° of the centrum inferior to the spinal canal (state 1).  In other mammals (e.g., Sorex) the odontoid process is pointed and has a narrow origin from the C2 centrum (state 0).  Tursiops lacks an odontoid process on C2 (state 2).

125  C3-7 spinous processes (Simmons, 1995: char. 32):  Several mammalian groups show reduced cervical spines posterior to C2, in which the dorsum of the neural arch is flat (e.g., Chaetophractus, state 1).  Among other taxa (e.g., Tenrec) variably sized spinous processes project dorsally (state 0).

126  Sternal ventrum (Simmons and Geisler, 1998: char. 91):  A ventrally projecting keel emanates from the manubrium sterni in bats, the colugo, Condylura, Amblysomus, and a few other genera (state 1).  In most mammals (e.g., Didelphis) this region is ventrally flat. (state 0).

127  Sternal ribs:  Certain edentates (e.g., Bradypus) exhibit completely ossified sternal ribs (state 1).  In most other mammals (e.g., Homo) these sternal elements remain cartilaginous throughout life (state 0).  

128  Clavicle (Asher, 2000: char. 100):  Many mammals, particularly cursorial ones, do not possess an ossified clavicle (e.g., Equus, state 2).  In other mammals this membranous bone is elongate and connects the shoulder with the sternum (e.g., Tenrec; state 0); in talpids it is greatly shortened (state 1).

129  Dorsum of proximal ribs (Simmons, 1995: char. 37):  Bats, colugos, xenarthrans, and other mammals possess dorsoventrally flattened ribs slightly distal to their vertebral articulations on either side of the midline of the vertebral column (state 1).  In other groups (e.g., Canis) ribs are proximally oval or rounded (state 0).

130  Intervertebral articulations (MacPhee, 1994: char. 18):  Xenarthrans are so named based on the presence of synovial intervertebral articulations, besides zygopophyses and centra, between at least the caudal few lumbar vertebrae (state 1).  In other mammals synovial articulations between vertebrae are limited to zygopophyses and centra (e.g., Homo, state 0).

131  Thoracic spinous processes:  As is the case for the cervical vertebrae, certain taxa (e.g., Pteropus) lack spinous processes on fifth to ninth thoracic vertebrae, showing instead a dorsally flat neural arch (state 1).  Other mammals (e.g., Lama) show dorsally elongate neural arches extending from all thoracic vertebrae (state 0).

Forelimb
132  Scapular shape (Simmons, 1994: 24):  Bats possess an anteroposteriorly elongate scapular, such that its craniocaudal length is greater than its mediolateral breadth (state 1).  Other mammals (e.g., Didelphis) show the opposite condition with a scapula wider than long (state 0).

133  Scapular coracoid:  In primates, the coracoid process of the scapula is elongate and extends anteroventral to the humerus, situated in the glenoid fossa of the scapula (state 1).  Most other taxa show a coracoid that is limited to the anterodorsal margin of the glenoid fossa (e.g., Cavia, state 0).  In Orycteropus, the scapular coracoid is anteriorly elongate but does not curve ventral to the humeral head (state 2).

134  Radius-Humerus ratio (Wible and Novacek, 1988: table 3, char. 11):  Bats and colugos share an elongate forelimb, such that the length of the radius exceeds that of the humerus (e.g., Cynocephalus, state 1).  Other taxa possess forelimb elements of similar size (e.g., Homo, state 0).

135  Humeral head (MacPhee, 1994: char. 20):  Considerable variability occurs in the relative height of the proximal humeral tuberosities.  In Procavia, the humeral head is situated well below the greater tuberosity of the humerus (state 0); in Didelphis, it is even with the greater tuberosity (state 1); and in Homo the humeral head lies superior to the greater tuberosity (state 2).

136  Supinator ridge (Simmons, 1995: char. 10):  Most mammals (e.g., Rattus) possess a prominent crest on the lateral margin of the distal humerus that serves as an attachment site for forearm supinator muscles (state 0).  In contrast bats, carnivorans, many ungulates, and other taxa lose this ridge and possess a laterally flat distal humerus (e.g., Pteropus, state 1).  

137  Entepicondylar foramen (Thewissen and Domning, 1992: char. 41; Asher, 1999: char. 57):  The distal humerus of many taxa examined here is pierced on its medial epicondyle by the entepicondylar foramen (e.g., Tenrec, state 0).  Other animals show no foramen medially (e.g., Erinaceus, state 1).

138  Olecranon fenestra of humerus (Thewissen and Domning, 1992: char. 42; Asher, 1999: char. 59):  Distally, the humerus may be fenestrated within the olecranon fossa (e.g., Erinaceus, state 1); in most taxa the olecranon process of the ulna articulates in a well-ossified fossa of the humerus (e.g., Didelphis, state 0)

139  Medial epicondyle of humerus (Geisler and Luo, 1998: char. 64; Asher, 1999: char. 58):  Most taxa possess a medially projecting epicondyle that makes up at least 25% of the distal humeral margin medial to the trochlea (e.g., Rattus, state 1).  Others show a reduced or absent medial epicondyle (e.g., Canis, state 0).  When present, the medial epicondyle may be greatly enlarged, comparable in lateral extent as the entire length of the humeral shaft (e.g., Amblysomus, state 2).

140  Articular shape of distal humerus: The trochlea and capitulum of the distal humerus in most taxa (e.g., Homo) are transversly cylindrical and form a smooth curve (state 0).  In cetaceans, the humerus articulates with each forearm bone along flat articulating surfaces that join at a "V"-shaped angle (state 1).

141  Proximal radius:  In Homo the radius articulates proximally with the capitulum of the distal humerus, and is circular in shape (state 0).  In contrast, several ungulates (e.g., Lama) possess a proximal radius with a transversly expanded articular surface that articulates with the trochlea in addition to the capitulum; the articular surface of the proximal ulna is correspondingly restricted to the posterior aspect of the trochlea (state 1).  Loxodonta possesses a ovoid, narrow proximal radius located in a V-shaped notch in the proximal ulna.  The articular surface of the ulna extends both medial and lateral to the proximal radius (state 2).

142  Proximal ulna:  Proboscideans show a proximal ulnar articular surface that is divided into medial and lateral halves by a notch into which the proximal radius articulates (state 1).  In other taxa (e.g., Tenrec) the radial articular surface is lateral to that of the proximal ulna (state 0).

143  Ulnar olecranon (Novacek, 1989: char. 41; Simmons, 1995: char. 38):  The olecranon process of the proximal ulna in bats, colugos, and cetaceans is reduced and does not occlude in a well-defined olecranon fossa of the distal humerus (state 1).  The ulnar olecranon of other mammals (e.g., Tenrec) extends proximally beyond the articulation with the humerus and occludes in the olecranon fossa of the distal humerus (state 0).

144  Distal ulna (Simmons, 1995: char. 38; MacPhee, 1994: char. 21; Asher, 2000: char. 111):  The ulna of Elephantulus and Macroscelides tapers to a distal terminus about halfway down the shaft of the radius and has no contact with the carpus (state 0).  The more common condition among mammals is a distally robust ulna that participates in the synovial wrist joint (e.g., Macropus, state 1).

145  Forearm shaft:  The ulnar and radial diaphyses in certain ungulates (e.g., Lama) are fused to one another along their lengths, although some separation may be evident distally (state 1).  The shafts of these bones are separate in most other mammals (e.g., Tapirus).

146  Distal radius-ulna:  Even though the diapophyses of its radius and ulna are separate, the distal end of the forearm in Trichechus is fused (state 1).  In most other taxa (e.g., Macropus) the distal radius and ulna are unfused (state 0).

147  Metacarpal length:  Some ungulates show elongate metacarpal bones, at least 50% of the length of to the radius (e.g., Equus, state 1).  Most mammals have metacarpals that are much shorter than the radius, closer in length to proximal phalanges (e.g., Tenrec, state 0).

148  Carpal arrangement (Novacek, 1989: char. 62):  Hyraxes, elephants, and sea cows are notable for their lack of a lunate-unciform articulation, and the otherwise non-overlapping arrangement of the proximal and distal rows of carpal elements (Novacek and Wyss, 1986: 280).  In most mammals, the articulations between elements of each carpal row are offset and show an articulation between the lunate and unciform (e.g., Chaetophractus, state 0).

149  Scaphoid-lunate fusion (Wyss and Flynn, 1993: char. 55):  The distal radius typically shows a broad articular surface for separate scaphoid and lunate carpal bones (e.g., Didelphis, state 0).  In many other taxa (e.g., Canis) these elements are fused into a single carpal (state 1).

150  Third phalanx of second digit (Simmons, 1995: char. 15):  In microchiroterans this terminal phalanx fails to ossify (state 1); more commonly it is ossified (e.g., Didelphis; state 0).

151  Terminal phalanx shape (Thewissen and Domning, 1992: char. 44):  When present, the terminal digits of mammals are either mediolaterally compressed (e.g., Rattus; state 0) or dorsoventrally compressed (e.g., Equus; state 1).  

152  Manual phalageal number:  Cetaceans have many rows of phalanges with sesamoid-like, semi-ossified terminals (state 1).  More commonly, mammals possess only three well-ossified phalanges distal to the metacarpals on digits II-IV (e.g., Macropus, state 0).

Pelvic girdle
153  Sacral vertebrae (Thewissen and Domning, 1992: char. 45; Asher, 1999: char. 63):  Most taxa possess between two and four vertebrae in the sacrum (e.g., Tenrec, state 0).  A few taxa possess at least five well-ossified vertebrae in their sacra (e.g., Talpa, state 1).

154  Pubic symphysis (MacPhee, 1994: char. 22; Asher, 1999: char. 62):  Insectivorans have been characterized as having either narrow or no contact between each pubis at the symphysis (e.g., Tenrec, state 1).  Most other mammals have a craniocaudally broad pubic symphysis, similar in length to ischiopubic rami framing the obturator foramina of each os coxae (e.g., Tupaia, state 0).

155  Dorsal ilium:  Certain ungulates, Homo, and Bradypus possess a marked dorsal extension of the ilium against which the sacrum articulates (state 1).  Other mammals, in contrast, show a dorsoventrally narrow ilium, not much greater in width distally as proximally (e.g., Didelphis; state 0)

156  Ischial notch (MacPhee, 1994: char. 23; Novacek, 1989: char. 69):  Most mammals show no articulation between the ischium and sacrum and/or caudal vertebrae (e.g., Macaca, state 0).  Xenarthrans, in contrast, have a second pelvic "obturator foramen" defined posteriorly by fusion of these elements (state 1).  As noted by Rose and Emry (1993) and MacPhee (1994), Manis shows some approximation of the ischium and sacrum, but the two are not ossified, and this character is therefore coded here as state "0."

157  Sacral-ilium articulation (Geisler and Luo, 1998: char. 62; Geisler, 2001; char. 130):  Cetaceans and sea cows have a rudimentary or absent pelvis; as such, they lack a functional sacro-iliac articulation (state 1), widely present among other mammals (state 0).  

158  Anterior process of the pubis:  Certain bats show a marked, anteriorly directed process of the pubis, inferior to the acetabulum (state 1).  This region in other mammals is either flat or shows a ventrally projecting pectineal tubercle (e.g., Didelphis; state 0).

159  Epipubic bones (Novacek, 1989: char. 19):  Marsupials possess elongate, anteriorly projecting bones that proximally articulate with a point close to the pubic symphysis (state 0).  Other mammals (e.g., Tupaia) show no articular surface on the anterior aspect of the pubis (state 1).

160  Vertebrae distal to sacrum (Wyss and Flynn, 1993: char. 54):  Most mammals show a long string of caudal vertebrae extending posterior to the sacrum (e.g., Felis, state 0).  In several taxa (e.g., Bradypus), this series is curtailed (state 1) and does not exceed 10 vertebrae.

Hindlimb
161  Femoral fovea capitis (MacPhee, 1994: char. 27):  The fovea for the ligamentum teres in most mammals is located centrally on the femoral head, within the articular surface for the acetabulum (e.g., Tupaia; state 0).  MacPhee (1994) noted that Plesiorycteropus, Orycteropus, and several other taxa have a posteriorly situated fovea capitis that interrupts the margin of the articular surface on the femoral head (state 1).  Additionally, certain taxa (e.g., Manis) lack a distinct fovea capitis (state 2).

162  Femoral neck:  Bradypus lacks a femoral neck.  Instead, its femoral head projects dorsally from its femoral diapophysis (state 1).  In contrast, most other mammals show a medially directed femoral neck upon which the femoral head is situated, dorsomedial to the diapophysis (e.g., Homo, state 0).

163  Third femoral trochanter (O'Leary and Geisler, 1999: char. 101; Asher, 1999: char. 61):  Many taxa show an flange on the lateral aspect of the femur, inferior to the lesser trochanter, proximally situated relative to midshaft (e.g., Tenrec, state 0).  In Chaetophractus the third trochanter is situated near the midshaft of the femoral diapophysis (state 1); and in Pteropus it is greatly reduced (state 2).

164  Medial trochanteric ridge (Hermanson and MacFadden, 1996):  The distal femur of horses and rhinos shows an enlarged medial ridge of the patellar articular surface (state 1).  In contrast, the medial and lateral margins of the patellar articular surface in most other taxa (e.g., Didelphis) are homogenous in size (state 1).

165  Fusion of distal tibia and fibula (Webb and Taylor, 1980):  The distal tibia and fibula may be completely fused or synostosed at the ankle (e.g., Erinaceus, state 1).   Some taxa possess a distal tibia-fibula that approximate each other but show no fusion (e.g., Tenrec, state 0).

166  Ossification of the fibula (Simmons and Geisler, 1998: char. 170):  The fibula in several bats is weakly ossified and thread-like in appearance (e.g., Artibeus; state 1).  In contrast, most mammals (e.g., Echinops) possess a well-ossified and robust fibula (state 0) which is in some cases fused distally with the tibia (see below).

167  Fibular facet of calcaneus (Meng and Wyss, 2001: char. 79):  Certain taxa (e.g., Amblysomus) have a prominent articular surface on the calcaneus for the distal fibula (state 1); in others (e.g., Canis) the two ankle bones do not articulate (state 0).  In some cases (e.g., Tragelaphus) the fibula is degenerate, but retains a distal rudiment that articulates with a prominent facet on the calcaneus (Webb and Taylor, 1980).

168  Calcaneal (= peroneal) tubercle (Asher, 1999: char. 71):  In Erinaceus the distolateral margin of the calcaneus shows a blunt rugosity (state 0) for attachment of abductor digiti quinti and, following Gregory (1910: 250), a tarso-metatarsal ligament.  In Echinops this rugosity is elongate and similar in size to the sustentaculum tali, extending laterally and/or distally past the distal margin of the calcaneus (state 1).

169  Dorsum astragalus:  Most placental mammals have a well defined trochlea on the proximal astragalus for articulation with the distal tibia (e.g., Canis, state 1).  In contrast, Didelphis and graviportal animals such as Loxodonta show a dorsally smooth astragalus, without a centrally grooved articular surface for the distal tibia (state 0).

170  Sustentacular facet of astragalus (Novacek and Wyss, 1986: 277; Novacek, 1989: char. 36):  The articular surfaces for the calcaneus and navicular may be discrete and located apart from one another on the ventral and distal aspects of the astragalus (e.g., Macropus, state 0).  In contrast, many taxa show confluence of these surfaces, and possess an elongate, composite articular surface on the ventral and distal aspects of the astragalus for the sustentaculum tali of the calcaneus and proximal navicular, respectively (e.g., Lemur, state 1). 

171  Astragalar cotylar fossa (MacPhee, 1994: char. 28):  The medial aspect of the astragalus in Plesiorycteropus is strongly concave and bounded anteriorly by a fossa into which the medial malleolus of the tibia articulates (state 1).  Other taxa (e.g., Tamandua) show a relatively flat medial side of the astragalus (state 0).

172  Astragalar posteromedial process (MacPhee, 1994: char. 29):  Orycteropus shows a prominent flange of bone at the medial and posterior margin of its astragalus (state 1).  This region in most other taxa is flat (e.g., Canis, state 0).

173  Astragalar navicular facet (Thewissen and Domning, 1992: char. 50; O'Leary and Geisler, 1999: char. 104):  In most taxa the distal astragalus is convex and articulates in a concave proximal navicular (e.g., Tenrec; state 0).  Perissodactyls show a "saddle"-shaped distal astragalus (state 1).  Artiodactyls possess a distal trochlea, similar in overall shape to the proximal tibial astragalar facet and responsible for the "double-pulley" appearance of the artiodactyl astragalus (state 2).  Manis shows a distal concavity  (state 3).

174  Calcaneal facet of astragalus (Geisler, 2001: char. 163):  In addition to their "double-pulley" astragalus, artiodactyls possess a large, laterally situated facet on the astragalus for the calcaneus (state 1).  In other taxa (e.g., Lemur) the calcaneal facet is restricted to the plantar aspect of the astragalus (state 0).

175 Astragalus-cuboid contact (Geisler, 2001: char. 159):  The distal astragalus in most taxa (e.g., Condylura) articulates primarily with the navicular (state 0).  In others the distal astragalus shows a distinct lateral facet for articulation with the proximal cuboid (e.g., Sus, state 1).  

176  Proximal cuboid (adapted from Geisler, 2001: char. 165):  Regardless of its articulation with the calcaneus and/or astragalus, the proximal cuboid is flat in most mammals (e.g., Homo; state 0).  In Macropus and artiodactyls it is "stepped" or divided into two articular facets by a sharp median ridge into which the more proximal tarsal elements articulate.

177  Projection from the ankle (Schutt and Simmons, 1998):  In most mammals the only bones participating in the proximal ankle are the tibia, fibula, astragalus, and/or calcaneus (e.g., Canis, state 0).  In microchiropterans, a medially projecting, ossified calcar is present that articulates proximally with the tuber of the calcaneus (state 1); in megachiropterans, the calcar consists of an unossified uropatagial spur that extends from the gastrocnemius muscle and has no articulation with the calcaneus (state 2).

178  The functionality of each pedal digit, from I-V, is used here as five independent characters.  Character state "0" indicates that the digit is weight-bearing; state "1" indicates that it is reduced.  This coding permits the important distinction between apparently "tridactyl" taxa as, say, Macropus and Hydrochaeris.  In the former, the foot is comprised of digits IV, V, and a syndactyl II and III; in the latter, digits II, III, and IV predominate.  A given digital ray is here interpreted as "reduced" when it is either much thinner in caliber than other digits (e.g., digit II of Macropus) or shortened such that the distal phalanx does not extent past the metatarsal of an adjacent digit (e.g., digit I of Erinaceus)
179  Digit II
180  Digit III
181  Digit IV
182  Digit V

183  Opposability of first metatarsal:  Primates (except Homo) and Didelphis are notable in possessing a grasping foot, in which the metatarsal of digit one can be adducted against the plantar surface of the foot and/or tips of other digits (state 1).  In other taxa (e.g., Tenrec) the metatarsal of digit one has relatively less mobility and is similar to other metatarsals in this respect (state 0).  

184  Metatarsal length:  Some ungulates show elongate metatarsal bones, at least 50% of the length of the tibia (e.g., Equus, state 1).  Most mammals have metatarsals that are much shorter than the tibia, closer in length to proximal phalanges (e.g., Tenrec, state 0).  The metatarsals of Macropus are elongate, but do not approach 50% of the length of its greatly elongated tibia (state 2).

185  Proximal phalanx of pedal digit I (Simmons, 1994: char. 21):  Simmons (1994: 34) figured the foot of two bats, illustrating that the proximal phalanx of digit I was elongate relative to those of the other digits (state 1).  In other mammals (e.g., Didelphis) this phalanx is similar or slightly shorter than the proximal phalanges of digits II-V (state 0).

Soft Tissue
186  Forelimb patagium (Wible and Novacek, 1988: table 3: char. 12; Szalay and Lucas, 1993).  Bats and colugos are unique among mammals observed in this study in possessing a patagium or flight membrane connecting digits of the manus (state 1).  In most other mammals (e.g., Homo) manual digit(s) extend distally from the metacarpus with no soft-tissue connections between adjacent structures (state 0).  

187  Cloaca (Shoshani and McKenna, 1998: char. 215).  The anal and urogenital tracts open into a common recess in tenrecs, Ochotona, and some marsupials (state 1).  In most placentals (e.g., Homo), the anal and urogenital tracts have separate perineal openings (state 0).

188  Trophoblast (Lillegraven, 1969, 1985).  One of the defining features of placental mammals is the presence of a trophoblast, a barrier surrounding an inner cell mass (and later developing embryo), which protects the embryo from immunological attack (state 1).  This function in non-placental mammals such as Macropus is carried out by a "shell membrane" throughout the first two-thirds of pregnancy (state 0).

189  Maternal-fetal nutrient exchange (Lillegraven, 1969).  As discussed by Lillegraven (1969: 104) and many embryologists before him (see reviews by Luckett, 1977, 1993, and Mossman, 1987), the taxonomic term "placental" as distinct from "marsupial" is slightly misleading, since pregnant female marsupials possess a placenta that is indispensable to a developing embryo.  In the choriovitelline placenta of Didelphis, the yolk sac is relatively large and the allantois does not have intimate contact with extra-embryonic tissue.  Maternal nutrients from uterine milk are acquired by vitelline blood supply to the yolk sac (state 0).  In contrast, the chorioallantoic placenta present in extant eutherians (e.g., Homo) shows a much greater association between maternal and fetal tissues, with exchange of maternal nutrients occuring through umbilical vessels (at first via the allantoic stalk and later the umbilical cord) that disperse throughout the trophoblast (state 1).  

190  Placental membrane (Mossman, 1987; Carter, 2001).  One area of variation in the eutherian placenta is the way in which maternal blood reaches the trophoblast of the interhemal membrane.  Contact between uterine epithelium and trophoblast is called epitheliochorial (e.g., Equus, state 0); contact between a maternal capillary endothelium and trophoblast is endotheliochorial (e.g., Felis, state 1); and direct contact between maternal blood and the trophoblast is called hemochorial (e.g., Procavia, state 2).  Marsupials are coded as inapplicable for this character, as the function served by the eutherian trophoblast is in marsupials carried out by the shell membrane, combined with an abbreviated intra-uterine period of development.

191  Yolk sac (Mossman, 1987; Carter, 2001).  The persistence of the yolk sac throughout gestation also varies across mammals.  As summarized by Carter (2001: table 1), it may be permanent (e.g., Erinaceus, state 0), temporary (e.g., Homo, state 1), or rudimentary throughout gestation (e.g., Orycteropus, state 2).  

192  Gestation time (Lillegraven, 1984; Millar, 1981).  A marsupial with the same body size as a placental mammal will have a markedly shorter period of embryonic intrauterine development (e.g., Macropus, state 0), not known to exceed 7 weeks.  Related to the integrated functionality of the placental reproductive system, living eutherians have relatively longer gestation times (e.g., nearly two years in Loxodonta; state 1).  

193  Ureter (Renfree, 1993).  The relations of the ureter and mullerian ducts differ in late ontogenetic stages of marsupial and placental mammals.  In the former, as it leads to the bladder the ureter passes medial to the mullerian and wolffian (or mesonephric) ducts (state 0); in the latter, the ureter passes lateral to the mullerian and wolffian ducts (state 1).

194  Hindgut (MacPhee and Novacek, 1993).  The word "Lipotyphla" derives from the simplified intestinal tract found in insectivoran-grade mammals.  Shrews, moles, hedhogs, tenrecs, golden moles, and Solenodon, in addition to certain other mammals (e.g., many bats), lack a cecum and do not have well- differentiated proximal and distal parts of the gut tube (state 1).  Most other mammals (e.g,. Sylvilagus) possess a cecum, plus large and small intestines with distinct anatomical and functional properties (state 0).

195  Testes (Werdelin and Nilsonne, 1999):  Adult male elephant shrews possess testes located deep in the abdomen, adjacent to the kidneys (state 0, also known as "testicondy").  Other mammals possess testes that are descended far from the kidneys, but ascrotal and still located within the abdomen (e.g., Orycteropus, state 1), or descended and contained outside the abdomen within a scrotal sac (e.g., Equus, state 2).  Fischer (1998) has noted interesting anatomical differences in the "testicondy" of hyracoids vs. that of other paenungulates.  

196  Eustacian sac (Fischer, 1986; Fischer and Tassy, 1993).  Hyraxes, horses, and tapirs possess a large diverticulum of the proximal, pharyngeal part of the eustacian tube that, fully developed, displaces the internal carotid artery away from the medial aspect of the auditory bulla (state 1).  In other mammals, the pharynx is not markedly expanded laterally or inferiorly (e.g., Homo, state 0).

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