Amphicynodon teilhardi ( Matthew and Granger, 1924 )

WANG, XIAOMING, McKENNA, MALCOLM C. & DASHZEVEG, DEMBERELYIN, 2005, Amphicticeps and Amphicynodon (Arctoidea, Carnivora) from Hsanda Gol Formation, Central Mongolia and Phylogeny of Basal Arctoids with Comments on Zoogeography, American Museum Novitates 3483, pp. 1-58 : 28-39

Amphicynodon teilhardi ( Matthew and Granger, 1924)

Figures 10–14 ; Tables 2, 6, 7

Cynodon (Pachycynodon) teilhardi Matthew and Granger, 1924: 9 , fig. 6D.

Amphicynodon teilhardi (Matthew and Granger) : Mellett, 1968: 11; Lange­Badré and Dashzeveg, 1989: 139; Cirot and Bonis, 1992: 119, fig. 13; Dashzeveg, 1996: 3.

Cynodictis mongoliensis Janovskaja, 1970: 73 , figs. 2–6.

Amphicynodon mongoliensis (Janovskaja) : Cirot and Bonis, 1992: 119.

HOLOTYPE: AMNH 19007 , left ramal fragment with m1–2 and m3 alveolus.

TYPE LOCALITY: Loh, in Tsagan Nor Basin, eastern Valley of Lakes, Obor­Khangay Province, in north­central Mongolian People’s Republic. In Tatal Member (‘‘lower red beds’’) of Hsanda Gol Formation, early Oligocene.

REFERRED SPECIMENS: AMNH 19014 , right ramal fragment with p1–3, field no. 73 ; AMNH 19129 , left ramal fragment with m1, from 10 mi west of Loh , ‘‘ Grand Canyon’ ’; AMNH 21628 , left maxillary fragment with P2–4, field no. 532 ; AMNH 21673 , left ramal fragments with p2, m1–3, and alveoli of c–p1, field no. 531, ‘‘ Grand Canyon’ ’; AMNH 84198 , isolated left m1, field no. 531, ‘‘ Grand Canyon’ ’; AMNH 84212 , left ramal fragment with m2–3 and m1 alveolus, field no. 532 ; MAE SG.8162, left ramus with p2–m1 (broken); MAE SG.9198–201, basicranium and maxillary fragments with left P2 and P4–M2 ( AMNH cast 129861), and right M1–2, from loc. MAE M­174, 2 mi southwest of the Loh, on east side of a ridge, 458169140N, 1018469020E, found not far above a brown sandstone layer, a local equivalent of the basalt lava ( MAE M­174 is still within the Ulaan Khongil fauna that contains most specimens of Amphicticeps shackelfordi in Shand Member) ; MAE SG.9193, right maxillary fragment with P4–M2, from locality MAE 95 ­M­50, the Main Camp Locality , Tatal Gol, in Tatal Member ; MAE SG.95.7488, left ramal fragment with broken p4 and m1; PST 17 /34, anterior half of skull with complete right upper incisors, broken left and right canines, and complete left and right P2– M2, from Tatal Gol (Ulaan Khongil) ; PIN 475–3016 , holotype of Cynodictis mongoliensis ( Janovskaja, 1970: figs. 2–3), partial skull with complete left and right upper teeth and left ramus with p2–m3, from Tatal Gol (fig. 14) ; PIN 475–1388 , partial palate with P3–M2 ( Janovskaja, 1970: fig. 4) ; ZPAL MgM III/96, right ramal fragment with p3– m2 and m3 alveolus, Tatal Gol (Lange­Badré and Dashzeveg, 1989: 139); and ZPAL MgM III/97, left ramal fragment with p3–m1, Tatal Gol .

DISTRIBUTION: Early Oligocene of northcentral Mongolian People’s Republic. Dashzeveg (1996: fig. 1) reported that Amphicynodon teilhardi occurs in both the lower Tatal Member and upper Shand Member of the Hsanda Gol Formation. An undescribed record was reported in the early Oligocene Khatan­Khayrkhan locality of Altai Province of Mongolia by Russell and Zhai (1987: 324).

EMENDED DIAGNOSIS: As the only known species from Asia, Amphicynodon teilhardi differs from all European species of the genus, except A. velaunus , in its shortened m2, along with a correspondingly reduced M2, in contrast to a primitively long m2 and large M 2 in most European species. A. teilhardi primitively retains a distinct posterior accessory cusp on p4, which is lost or extremely reduced in the European A. gracilis , A. speciosus , and A. velaunus . A. teilhardi further differs from European A. typicus , A. gracilis , and A. crassirostris in its relatively low hypoconid of m1 with wrinkled enamel, in contrast to a trenchant talonid in the latter three species.

DESCRIPTION: PST 17 /34 offers the best cranial morphology among all materials. Although it is missing the posterior one­third of the skull, the remaining skull of PST 17 / 34 is nearly perfectly preserved and offers fine details of bony and dental structures. Another cranial fragment, MAE SG.9198– 201, is less complete on the anterior part (consisting of a heavily crushed partial rostrum plus left orbital region) but preserved a partial left basicranium. In addition, we are in possession of a cast of a partial skull and mandible from the collection of the Russian Paleontological Institute, PIN 475–3016 (holotype of Cynodictis mongoliensis ). In combination, much of the skull, except the posterodorsal portion, is known .

Skull (figs. 10, 11): The overall proportion of the skull is less specialized than that of Amphicticeps . The rostrum is not shortened and broadened and the temporal region is not elongated, as in the latter. The premaxillaries form a thin blade on either side of the nasal opening. The entire premaxillary is preserved. The posterior process of the premaxillary does not touch the anterior process of the frontal, and ends near the posterior tip of the canine root at the level of P1. Both nasals are broken anteriorly, and their posterior tips end at roughly the same level as the maxillaryfrontal suture. The frontal process inserts between the nasal and maxillary and ends anteriorly at the level of the P2 main cusp. The frontal is slightly domed, in contrast to a flat forehead in Amphicticeps . The postorbital process is small and does not have the distinct protrusion seen in Amphicticeps . The orbit is relatively large and is of approximately the same size as that of Amphicticeps , which has a much larger skull. The distance between the postorbital process and postorbital constriction is 7 mm on PST 17/34 and 9 mm on MAE SG.9198–201, significantly shorter than the 12 mm of Amphicticeps , and thus has a far shorter temporal region than the latter. Furthermore, the postorbital constriction is not so narrow as in Amphicticeps . The temporal crests are very indistinct, and they converge more slowly toward the sagittal crest than in Amphicticeps . In PST 17/ 34, the temporal crests do not fully converge at the posterior edge of the broken skull, and the sagittal crest, if present, is not preserved.

In lateral view, the orbital region is best preserved on the right side of PST 17/34 (fig. 11). It is complemented by the partially preserved left orbital region of MAE SG.9198–201. The orbital mosaic is quite similar to that of Amphicticeps in several respects: a short infraorbital canal, presence of a shallow fossa in front of the antorbital rim (less developed in PST 17/34), a small, nearly rounded lacrimal bone with a lacrimal foramen near its anterior aspect, anterior process of jugal in contact with the lacrimal, and other topographic relationships among individual bony elements. Perhaps of phylogenetic significance is the shorter postorbital area between the postorbital process and postorbital constriction.

In ventral view, the incisive foramen (palatine fissure) is short and located at the level of the anterior aspect of the upper canine. A tiny foramen is present along the midline suture at the junction of the premaxillary and maxillary (foramen palatine medialis of Story, 1951), as is commonly seen in arctoids. The maxillary–palatine suture is mostly fused and difficult to recognize. The palatine foramen is somewhat behind the level of the P4 protocone. The posterior border of the palatine bone is anterior to the posterior border of the M2 and is distinctly indented by a semicircular notch on either side of the midline suture.

The width of the rostrum across P1s (measured on the lingual edge of the alveolus) measured 9.4 mm in PST 17/34. That for the laterally crushed rostrum on MAE SG.9198–201 measured 11 mm (restored from distorted left and right halves). These compare with 15.2 mm for the same measurement in Amphicticeps shackelfordi —the rostrum of Amphicynodon teilhardi is on average 49% narrower than the former. Given a size difference of 22% for the average length of P4 between these two species, the width of the rostrum in A. teilhardi is also relatively narrower than that of the type species. See additional cranial measurements (table 2) for PST 17/34.

Basicranium (fig. 12): The fragmentary materials of MAE SG.9198–201 offer the only information about the basicranium of Amphicynodon teilhardi . Although heavily crushed dorsoventrally, the left side of the basicranium of MAE SG.9198–201 preserves several key anatomical features absent in Amphicticeps . The overall basicranial morphology of Amphicynodon teilhardi is somewhat similar to that of Amphicticeps . The most obvious similarities are the presence of a shallow suprameatal fossa and a laterally expanded squamosal blade for the dorsal roof of the external auditory meatus. Much of the posterior half of the mastoid process is lost. However, the process is less laterally protruded than in Amphicticeps , judged from a more vertically oriented lateral wall of the braincase that forms a 908 angle with the horizontal squamosal shelf, in contrast to Amphicticeps , in which far more inclined lateral braincase walls (in posterior view) almost continue into the mastoid process. The suprameatal fossa is slightly less well developed than in Amphicticeps . In particular, its lateral half is not so deeply excavated into the squamosal as in Amphicticeps , and it does not have so clear­cut a lateral rim as in the latter.

The basisphenoid area is fragmented, and the ventral floor of the alisphenoid canal is broken off. However, enough is preserved in the area surrounding the foramen rotundum to indicate the presence of a canal, that is, the presence of a deep groove on the alisphenoid that probably forms its posterior opening. A small foramen opens into the medial wall of the canal at the level of its posterior opening.

The postglenoid process is large, forming a long ventral hook for articulation with the condyle of the mandible. At the posterior base of the postglenoid process, behind the postglenoid foramen, there is a triangular piece of ectotympanic still firmly attached to the basicranium. Part of the anterior ectotympanic ring for attachment of the tympanic membrane is also preserved. The ectotympanic does not extend laterally far beyond the postglenoid foramen, indicating no or a very short bony external auditory meatus. On the medial side, along the suture between promontorium and basioccipital, several broken pieces of the entotympanic are still preserved and cover the internal carotid canal. The ventral flooring of the canal, presumably formed by the caudal entotympanic, forms a gentle curve in a typical primitive arctoid fashion, leading toward the middle lacerate foramen. The presence of this medially positioned carotid canal further confirms our conclusion that there is no promontorial artery in Amphicynodon and Amphicticeps , despite of the sulci on ventral surface of the promontorium in the holotype of Amphicticeps shackelfordi (see description under that species). No sulcus is visible on the promontorium of A. teilhardi .

The promontorial part of the petrosal has been pushed dorsally toward the brain cavity, and its ventral surface is unnaturally rotated into a vertical orientation. The ventral promontorial surface has thus become laterally facing and is partially hidden beneath the lateral edge of the basioccipital. The postmortem crushing of the promontorium into the brain cavity, however, is apparently beneficial for the preservation of a nearly complete malleus and incus, which occupy the space originally occupied by the promontorium.

The malleus lies on its medial side with the lateral surface (for attachment of the tympanic membrane) of the manubrium facing ventrally. The malleus has a rather slender construction but is of large size—the head to manubrium tip (broken) measures 5.8 mm. The lateral process is inconspicuous. The muscular process (for insertion of m. tensor tympani) is broken near its base and its main body sticks out between the anterior process and the manubrium instead of its original position, pointing away from the plane of tympanic membrane. This slightly dislocated muscular process is very large and has a broad distal end, which contrasts with the much reduced condition in living ursids ( Segall, 1943). The neck is slender and forms a smooth curve between the head and the manubrium. The head is not enlarged as in pinnipeds ( Wyss, 1987). The sharp­tipped anterior process completes the anterior rim of a circular lamina. Much of the incus is buried beneath the head of the malleus. Only the processus brevis is fully exposed.

Upper teeth (figs. 13A–C, 14): Most of the upper dentition is now known. Upper incisors in PST 17/34 are all broken and the crown morphology is no longer preserved. The roots indicate progressively enlarged incisors from I1 to I3, with the I3 almost twice as large as the I1. All incisor roots are mediolaterally compressed. The left and right I3s in PIN 475–3016 are preserved and are slightly precumbent in lateral view, as is also the case in PST 17/34. The upper canines on both sides are also broken in PST 17/34, preserving only the roots. The canine roots are oval in cross section. The canines in PIN 475–3016 are present. The canine crowns are smooth surfaced and their tips curve backward slightly.

The cheek teeth are evenly spaced with short alveoli between all premolars in PST 17/34 but slightly more tightly spaced in PIN 475–3016, in contrast with crowded premolars of Amphicticeps due to its shortened rostrum. P1 is only seen in PIN 475–3016, and is single rooted. It has a simple main cusp and an indistinct cingulum anteriorly and posteriorly. The P2s are single cusped and are more slender than that of Amphicticeps . A rather tall and erect main cusp has a posterior ridge and an anterolingual ridge. The anterior and posterior cingula are slightly more distinct than in the P1s, but there is no cingular cusp on either end. The cingulum is continuous on the lingual side and discontinuous on the labial side. The main distinction between P3 and P2, besides a larger size and more prominent cingulum in the P3, is a slight swelling on the posterolingual cingulum of the tooth, but there is no extra root beneath this swelling. The morphology of P4 is similar in overall construction to that of Amphicticeps , except for a much smaller protocone. A distinct cingulum surrounds the entire tooth. The anterior cingulum is particularly well developed, as is the parastyle. However, the parastyle is not cusplike but more like a wide cingulum. As in Amphicticeps , the anterior border of the P4 protocone is slightly ahead of the parastyle. The protocone apex is clearly continuous with the lingual cingulum. The cuspidate protocone has an indistinct ridge on the labial side of the cusp. The paracone has a distinct anterior ridge reaching up to the parastyle, and a less distinct anterolingual ridge that reaches to the base of the protocone. A deep carnassial notch separates the paracone from the metastylar blade.

The overall construction of M1 is less hypercarnivorous than that of Amphicticeps . The M1 parastyle is substantially reduced as compared to those of Amphicticeps , even for the least developed M1 parastyle in A. makhchinus . A vague notch separates the parastyle and paracone. The labial cingulum is slightly swollen around the paracone in PIN 475– 3016 and around the right M1 of PST 17/ 34, similar to the swellings in Amphicticeps shackelfordi . The labial cingulum near the metacone is not so reduced as in Amphicticeps ; this is especially so in MAE SG.9193. Together, the smaller parastyle and less reduced labial cingulum along the metacone give M1 a more quadrate look. The labial borders of P4 and M1 form an angle of 1278, 188 larger than in Amphicticeps shackelfordi . The differences in size and height between paracone and metacone are also relatively smaller than in Amphicticeps . There is a well­developed preprotocrista and postprotocrista. There is no protoconule, except a slight swelling in PST 17/34, which is absent in the Russian specimens. The postprotocrista is essentially posteriorly oriented, particularly so in PST 17/34, leaving a broad valley between the postprotocrista and metacone. A metaconule is only vaguely suggested by a low and indistinct swelling at the posterior end of the postprotocrista and by a slight notch toward the posterior end of the postprotocrista. The internal cingulum (hypocone) surrounds the entire protocone, although its anterior segment is narrower. This anterior extension in front of the protocone, less well developed in MAE SG.9193, has a narrow spur near the base of the preprotocrista.

M2 has the same distinct shape as in Amphicticeps , reaching the same stage of reduction and acquiring the same peculiar cusp pattern as in the latter, although this tooth tends to vary more than does M1. A large paracone is located at the labial border of the tooth, whereas the metacone is reduced to a faint cusp at the posterior border (that in PST 17/34 is more distinct). The protocone is relatively large and is in the middle of the tooth, followed lingually by a broad cingular shelf. The main feature to be distinct from that of Amphicticeps is its less lingually shifted position. Instead of being flush with the lingual border of the M1 as in Amphicticeps shackelfordi , the lingual border of M 2 in Amphicynodon is slightly lateral to the M1 lingual border.

Lower teeth (figs. 13D–F, 14): Lower jaws figured by Janovskaja (1970: figs. 3, 5, 6) substantially improved the knowledge of Amphicynodon teilhardi over the original topotype series. The following descriptions of the ramus are based on figures published by Janovskaja. Her dental illustrations, however, lack sufficient details for useful comparisons, and have exaggerated the length of the m2 (see table 7 and comparison below), a critically important feature of this species. Our dental descriptions are mainly based on a cast of the PIN 475–3016, as well as more fragmentary materials from the AMNH.

The horizontal ramus is relatively slender compared to that of Amphicticeps . The ascending ramus has a rather erect anterior border. The angular process is slender and pointed. No lower incisor is preserved. The lower canine hooks backward slightly. The lower premolars are relatively more slender than those of Amphicticeps . The p1 is not preserved. The p2 has a simple main cusp and a very vague cingulum. The p3 begins to have a tiny posterior accessory cusp and a slightly more distinct cingulum. The p4 posterior accessory cusp is further enlarged, and its cingulum surrounds the entire tooth. The anterior cingulum has a hint of developing into an anterior cingular cusp, and the posterior cingulum is also slightly elevated.

The m1 trigonid is tall crowned. The metaconid is approximately the same height as the paraconid. The metaconid is on the lingual side of the protoconid, not trailing behind the protoconid as seen in most ursids. A cingulum is present on the entire labial margin of m1 but is only vaguely present on the lingual side of the paraconid. The m1 talonid is low, especially the hypoconid. The hypoconid is largely crestlike and is oriented at a slight angle from the anteroposterior axis of the tooth. Anteriorly, the hypoconid crest ends at the base of the protoconid just below its apex. The entoconid consists of a low ridge, rather like a cingulum. Together with the hypoconid, the entoconid encloses a broad basin on the talonid. The talonid cusps are decorated with fine wrinkles. The m2 is small and distinctly short; its length and width are nearly identical. No paraconid is visible. A protoconid and metaconid are of equal height and positioned on the borders of the tooth, such that a central valley essentially runs through the length of the tooth. A small cristid connects between the protoconid and metaconid in the holotype but is absent in PIN 475–3016. On the talonid, the hypoconid is far better developed than the entoconid, which is absent in the holotype. A small m3 is present in all specimens that preserve this part of the jaw. It is formed by a small, rounded, peglike structure with a surrounding cingulum but without a distinct cusp pattern.

COMPARISONS: The topotype series of Amphicynodon teilhardi consists of a few jaw fragments and lower teeth without upper teeth. Based on such meager materials, Matthew and Granger (1924: 8) were initially ambivalent in their assignment of this species to Cynodon ( Amphicynodon of current usage): ‘‘This species can be referred only provisionally until better specimens are available. It appears to fall within Pachycynodon rather than the typical Cynodon , by Teilhard’s key to the Phosphorite genera,’’ in reference to Teilhard de Chardin’s (1915) monographic revision on Quercy carnivorans that dealt with these genera. The first major breakthrough in the state of knowledge of this species came by a crushed but associated skull and lower jaw (PIN 475–3016; fig. 14) along with a few more specimens collected by the 1946–1949 Expeditions of the Soviet Academy of Sciences. The Russian collection was described as a new species, Cynodictis mongoliensis , by Janovskaja (1970). While describing three additional jaw fragments collected by the Polish–Mongolian Paleontological Expeditions in the 1960s, Lange­Badré and Dashzeveg (1989: 141), however, argued that ‘‘there are no significant morphological or biometrical differences between C. mongoliensis and A. teilhardi and those that exist represent no more than intraspecific variation.’’ More recently, Cirot and Bonis (1992), in their phylogenetic analysis of the species of Amphicynodon , chose to leave Amphicynodon mongoliensis as a valid species, and in their cladogram, placed it next to A. teilhardi as the sister­species forming an Asiatic clade.

Although we are unable to examine the three jaw fragments in the ZPAL collection (Lange­Badré and Dashzeveg’s measurements for the holotype of A. teilhardi are apparently an underestimate), we have access to casts of two PIN specimens in the topotype series of C. mongoliensis . With the addition of even better materials from the MAE collections, we are in a position to evaluate morphological variations of at least 20 specimens (see table 7). Although the increased sample size naturally leads to a slight increase in variations, the coefficient of variation for most dental measurements generally falls between 5% and 8%, a range not uncommon for small carnivorans (e.g., Wang et al., 1999). The only exceptions are for the upper canines, which tend to be more dimorphic among arctoids, and the m2s, which have the least occlusal constraint because of their flat grinding surfaces. Cirot and Bonis (1992: 119 and fig. 16) noted the rather long m 2 in A. mongoliensis , apparently on the basis of Janovskaja’s (1970: fig. 3) illustration of the holotype, and assigned this presumed long m2 as an autapomorphy for the species. Our own examination of a plaster cast of PIN 475–3016 shows no elongation of the m2 (fig. 14). In fact, our own measurements on the cast indicate a shorter length than the width for the m2 (3.0 mm in length and 3.2 mm in width), in sharp contrast to an elongated m2 shown in Janovskaja’s figure. It seems clear that the m2 length in Janovskaja’s illustration was exaggerated (the lack of morphological details in her illustration of the m2 further undermines the reliability of her published line arts). In our examinations of the rest of the dentitions, we failed to detect any substantial difference, either in size or shape, between the Russian collection and the rest of the samples. We thus fully agree with Lange­Badré and Dashzeveg that Cynodictis mongoliensis is synonymous with Amphicynodon teilhardi . The combined materials from AMNH, PIN, ZPAL, and MAE allow more confident assignments of fragmentary specimens and, as a result, increased morphological cohesion of this species.

Lange­Badré and Dashzeveg (1989: 141) chose to compare the Mongolian form with three Quercy species of Amphicynodon : A. typicus , A. leptorhynchus , and A. gracilis . They concluded that A. teilhardi was closer to A. leptorhynchus or A. typicus than to A. gracilis . Characters that were cited to indicate such a relationship include the wrinkled enamel and a reduced m2 paraconid. A revision of the systematics and phylogeny of Amphicynodon by Cirot and Bonis (1992: 119 and fig. 16), on the other hand, recognized 10 valid species, 8 European and 2 Asian, and suggested a relationship almost opposite to that suggested by Lange­Badré and Dashzeveg. Cirot and Bonis placed A. teilhardi (along with A. mongoliensis ; see comments above) as the sister­taxon to the terminal clade formed by A. gracilis and A. cephalogalinus , whereas A. leptorhynchus and A. typicus are further down the tree in more basal positions. A critical synapomorphy cited in support of above relationship was a ‘‘trigonide de M/1 disjoint’’ shared by A. teilhardi , A. gracilis , and A. cephalogalinus (Cirot and Bonis, 1992: fig. 16, node 10). In their remarks on A. teilhardi (Cirot and Bonis, 1992: 119) , this character was explained as an open trigonid due to a reduction and a posterior position of the metaconid of m1 (‘‘un trigonide ouvert en raison de la réduction et de la position reculée du métaconide’’). Lange­Badré and Dashzeveg’s character, a reduced m2 paraconid, was pushed further down the tree by Cirot and Bonis and was shared by A. velaunus , A. leptorhynchus , A. teilhardi , A. gracilis , and A. cephalogalinus . While it is beyond our scope to reevaluate species relationships of Amphicynodon , we note that Cirot and Bonis’s character of a disjoint m1 trigonid is not readily apparent in their illustrations of three of the four species of Amphicynodon that are supposed to share it. On the other hand, their illustration of A. leptorhynchus (Cirot and Bonis, 1992: fig. 3), a species that was supposed to possess a primitive condition for this character, shows a more posteriorly displaced m1 metaconid than in any other species. Our own examination of some of Cirot and Bonis’ materials in the Université de Poitiers, which form the partial basis of their systematic revision, fails to substantiate the validity of this character. Such a character, if it does exist, must be quite subtle at this stage of its evolution. In our observations, the presence and absence of an m2 paraconid does seem to be a valid character that unites some species of Amphicynodon , including A. teilhardi .

As for the generic status of the Mongolian species, Lange­Badré and Dashzeveg (1989: 141) rejected the initial suspicion by Matthew and Granger (1924) that the Hsanda Gol form was closer to the European Pachycynodon than to Amphicynodon : ‘‘ C. teilhardi belongs unquestionably to the genus Amphicynodon . It differs from Pachycynodon in the situation of the metaconid on m1, in the open basin, in the wrinkled enamel, in the reduced paraconid and entoconid in m2 and in the ratios of the talonid and trigonid on m2.’’ Cirot and Bonis (1992) more explicitly placed A. teilhardi among the rest of the European species of the genus. In light of the entire dentition available in this study, A. teilhardi falls within the overall parameters of the genus. However, since Amphicynodon , as a basal ursoid, was long suspected to have given rise to other clades (e.g., Teilhard de Chardin, 1915), it is likely a paraphyletic genus in a strict cladistic sense—various species may ultimately be shown to be more closely related to other clades. Until a comprehensive, species­level phylogenetic analysis is done, current concepts of Amphicynodon remain largely gradational. See table 1 for more contrasts of morphological differences between Amphicticeps and Amphicynodon .

Figures

Fig. 10. Amphicynodon teilhardi, PST 17/34, referred specimen. A, dorsal, B, lateral, and C, ventral views of skull.

Fig. 11. Dorsolateral aspect of skull in Amphicynodon teilhardi (PST 17/34), showing anatomy of the orbital region. Abbreviations are the same as in figure 4, except for Nas, nasal and Prem, premaxillary.

Fig. 12. Ventrolateral view of the left side of the basicranium of Amphicynodon teilhardi, MAE SG.9198–201. Cross­hatched areas indicate unprepared matrix. ac, alisphenoid canal; bo, basioccipital; ce, caudal entotympanic; cica, canal for internal carotid artery; ec, ectotympanic; fo, foramen ovale; fv, fenestra vestibuli (fenestra ovalis); hm, head of malleus; in, incus; la, lamina; ma, manubrium; mup, muscular process; pgf, postglenoid foramen; pgp, postglenoid process; plf, posterior lacerate foramen; pr, promontorium; sf, suprameatal fossa.

Fig. 13. Teeth and lower jaw of Amphicynodon teilhardi. A, lateral view of upper teeth, PST 17/ 34; B, occlusal view of upper teeth, PIN 475–1388; C, occlusal view of upper teeth, PST 17/34, stereophotos; D, occlusal view of lower teeth, AMNH 19007, holotype, stereophotos; E, lingual, and F, labial views of lower jaw, AMNH 19007, holotype. All, except E and F, are photographs of a polyester cast. Scales 5 10 mm.

Fig. 14. Stereophotos of a cast of PIN 475–3016 (holotype of Cynodictis mongoliensis Janovskaja, 1970). A, occlusal view of upper teeth and B, occlusal view of lower teeth. Scales 5 10 mm.