A new basal Carnivoramorphan (Mammalia) from the ‘Bridger B’ (Black’s Fork member, Bridger Formation, Bridgerian Nalma, middle Eocene) of Wyoming, USA
2010; Wiley; Volume: 53; Issue: 4 Linguagem: Inglês
10.1111/j.1475-4983.2010.00963.x
ISSN1475-4983
AutoresMichelle Spaulding, John J. Flynn, Richard K. Stucky,
Tópico(s)Paleontology and Evolutionary Biology
ResumoPalaeontologyVolume 53, Issue 4 p. 815-832 Free Access A new basal Carnivoramorphan (Mammalia) from the 'Bridger B' (Black's Fork member, Bridger Formation, Bridgerian Nalma, middle Eocene) of Wyoming, USA MICHELLE SPAULDING, MICHELLE SPAULDING Lamont–Doherty Earth Observatory, Columbia University, 61 Rt. 9W Palisades, NY 10964, USA; e-mail mspaulding@amnh.org Division of Paleontology and Richard Gilder Graduate School, American Museum of Natural History, Central Park West at 79th St. New York, NY 10024, USA; e-mail jflynn@amnh.orgSearch for more papers by this authorJOHN J. FLYNN, JOHN J. FLYNN Division of Paleontology and Richard Gilder Graduate School, American Museum of Natural History, Central Park West at 79th St. New York, NY 10024, USA; e-mail jflynn@amnh.orgSearch for more papers by this authorRICHARD K. STUCKY, RICHARD K. STUCKY Department of Earth Sciences, Denver Museum of Nature & Science, 2001 Colorado Boulevard, Denver, CO 80205, USA; e-mail richard.stucky@dmns.orgSearch for more papers by this author MICHELLE SPAULDING, MICHELLE SPAULDING Lamont–Doherty Earth Observatory, Columbia University, 61 Rt. 9W Palisades, NY 10964, USA; e-mail mspaulding@amnh.org Division of Paleontology and Richard Gilder Graduate School, American Museum of Natural History, Central Park West at 79th St. New York, NY 10024, USA; e-mail jflynn@amnh.orgSearch for more papers by this authorJOHN J. FLYNN, JOHN J. FLYNN Division of Paleontology and Richard Gilder Graduate School, American Museum of Natural History, Central Park West at 79th St. New York, NY 10024, USA; e-mail jflynn@amnh.orgSearch for more papers by this authorRICHARD K. STUCKY, RICHARD K. STUCKY Department of Earth Sciences, Denver Museum of Nature & Science, 2001 Colorado Boulevard, Denver, CO 80205, USA; e-mail richard.stucky@dmns.orgSearch for more papers by this author First published: 19 July 2010 https://doi.org/10.1111/j.1475-4983.2010.00963.xCitations: 12AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Abstract: A new genus and species of basal non-Viverravidae Carnivoramorpha, Dawsonicyon isami, is named and described. This new taxon is based upon DMNH 19585, an almost complete skeleton, which was collected from the Black's Fork Member (informal 'Bridger B' subunit) of the Bridger Formation in southwestern Wyoming, USA. The specimen is incorporated into an existing craniodental data matrix, and the associated phylogenetic analyses support the identification of this species as a new basal carnivoramorphan. This new taxon is dentally compared to all known genera of non-viverravid basal carnivoramorphans, as well as with all known species of the problematic genus Miacis. Postcrania are compared in detail with other described specimens of non-viverravid basal carnivoramorphans and more generally with known postcrania of viverravids. Preliminary functional interpretations of a scansorial locomotor mode are offered for this new taxon. Its implications for the diversity of middle Eocene basal carnivoramorphans is briefly discussed, including expansion of the already high diversity in the Black's Fork Member of the Bridger Formation (at least 11 species in 8 genera). The oldest carnivoramorphans to date have been found in the early Paleocene (Flynn 1998). These earliest representatives have been placed either in the first diverging monophyletic clade of the Carnivoramorpha (the Viverravidae) (Flynn 1998), or as incertae sedis near the base of the Carnivoramorpha (Fox and Youzwyshyn 1994). It is in the latest Paleocene that the first assuredly non-Viverravidae carnivoramorphans appear, and during the Eocene their diversity increases. It is not until the middle Eocene that specimens recognized as belonging to crown-clade Carnivora first appeared (Wesley-Hunt and Flynn 2005). The paraphyletic assemblage of taxa that fall between the Viverravidae and crown Carnivora in the past has been grouped together as the Miacidae. We advocate abandonment of this term, even in informal usage, as it creates a false and seriously misleading connotation of phylogenetic relationships and morphological similarity among basal carnivoramorphans (for an in-depth history of study, see discussions inFlynn and Galiano 1982; Flynn and Wesley-Hunt 2005; Wesley-Hunt and Flynn 2005). In this paper, we use the terms Carnivora to include only the crown clade, and Carnivoramorpha to refer to the crown clade plus all taxa that are hypothesized to be more closely related to Carnivora than to creodonts (following the terminology of Wyss and Flynn 1993; Flynn and Wesley-Hunt 2005). Prior to this paper, there were 14 commonly accepted genera of basal non-Viverravidae carnivoramorphans. Members of the stem lineage have been found in deposits in North America, Western Europe, and Asia (Flynn and Wesley-Hunt 2005). The majority of genera are found in North America; only four are exclusive to Europe (McKenna and Bell 1997). The only genus found solely in Asia is Xinyuictis, recently resurrected as a valid genus by Heinrich et al. (2008) contra Gingerich (1983), who subsumed Xinyuictis within Miacis. There are substantial taxonomic issues surrounding Miacis, and it almost assuredly represents a paraphyletic, if not polyphyletic, assemblage of non-Viverravidae basal carnivoramorphans. In this paper, we name and describe a new taxon of basal carnivoramorphan. This new taxon is based upon an almost complete skull and skeleton, collected by the Denver Museum of Nature and Science: DMNH 19585. This fossil was found in the Black's Fork Member ('Bridger B') of the Bridger Formation, within the middle Eocene Bridgerian North American Land Mammal 'Age' (NALMA), placing it at 49 to 46.7 Ma (Prothero 1998). This new specimen expands our knowledge of basal carnivoramorphans in general, and increases the known carnivoramorphan diversity in mid-Bridgerian age rocks of southwestern Wyoming. We thoroughly describe this specimen, offer a diagnosis of the new taxon, and incorporate it into the currently most comprehensive available matrix for analysing basal carnivoramorphan relationships (Wesley-Hunt and Flynn 2005; Spaulding and Flynn 2009). Methods All descriptions of the new taxon are from direct examination of the type specimen: DMNH 19585. Comparisons to other taxa were made, if possible, by direct examination of type specimens or casts of type specimens housed in the American Museum of Natural History Fossil Mammal collection. In rare instances, such as the European genera Paroodectes, Paramiacis, and Messelogale, if original material was unavailable, comparisons were made with published descriptions, photographs and illustrations. Body mass was reconstructed as 1.34 kg, using the equation from Legendre and Roth (1988) based upon regressions of m1 area. (Equation used: ). The phylogenetic position of DMNH 19585 was assessed by coding the morphology of the type specimen for incorporation into the matrix of Wesley-Hunt and Flynn (2005). Three additional basal carnivoramorphan taxa, Quercygale (e.g. Wesley-Hunt and Werdelin 2005), Viverravus acutus of Polly et al. (2006) and 'Miacis'uintensis, are incorporated into this analysis, based upon coding in Spaulding and Flynn (2009). The final matrix was comprised of 44 taxa coded for 99 characters. The possible non-independence of characters 43 (M1 size metastyle compared to parastyle) and 44 (M1 size parastyle compared to metastyle) of the original Wesley-Hunt and Flynn (2005) matrix was dealt with: #43 was eliminated as it does not vary within carnivoramorphans and its inclusion or elimination does not affect the results of the analysis. Table 1 presents the character codings of DMNH 19585. Table 1. Coding of Dawnsonicyon isami, DMNH 19585, for inclusion in cranio-dental matrix of Wesley-Hunt and Flynn (2005). DMNH 19585 ?011???0?? 00???????? ????0????? ?????????? 1011001102100121101? ?????0???? ???????000 01000110?? 00?0????? The matrix was analysed in PAUP* version 4.0b (Swofford 2000). We selected the heuristic search option with TBR branch swapping and ran the analysis for 1000 replicates. Bootstrap values were also generated with PAUP* version 4.0b, with 1000 separate bootstrap replicates comprised of 10 trials each. Decay index scores were found using TreeRot (Sorenson 1999). Abbreviations. AMNH, American Museum of Natural History, New York; DMNH, Denver Museum of Natural History, Denver; LP4, anterior-posterior length of fourth upper premolar, likewise for Lp3, Lp4, LM1, Lm1, and Lm2; MM1, distance from anterior labial border of paracone to posterior lingual border of protocone; MP4, maximum distance between the anterior border of the protocone and posterior border of metastylar blade; NALMA, North American Land Mammal 'Age'; Tm1, trigonid length of lower first molar; Twm1, talonid width of lower first molar; WP4, maximum width of 4th upper pre-molar, similar definitions for Wp3, Wp4, WM1, Wm1, and Wm2; WPM1, length of parastyle of first upper molar. Dental terminology for premolar cusps follows Flynn and Galiano (1982). Systematic paleontology CARNIVORAMORPHA Wyss and Flynn, 1993Genus DAWSONICYON gen. nov. Type species. Dawsonicyon isami sp. nov. Derivation of name. Named after Mary Dawson, in honour of her exceptional contributions to the study of fossil mammals, particularly fossil carnivoramorphans. Diagnosis. An early-diverging carnivoramorphan (presence of carnassial shear restricted to P4/m1 in adults) possessing the following plesiomorphic conditions: an unfused scaphoid and lunate, the presence of m3, the lack of expanded braincase with an anteriorly located fronto-parietal suture and the presence of the third trochanter of the femur. Differential diagnosis. Differs from crown clade Carnivora in lacking synapomorphies of that clade. Differs from all Viverravidae in: an M1 paracone that is much smaller than the protocone; retaining M3/m3; P4 parastyle cusp is not well developed and defined; and m2 talonid not elongate and lacking an enlarged hypoconulid. Differs from all other early-diverging (non-Carnivora) carnivoramorphans, in the following unique apomorphies of this new taxon: a p4 lingual basin that is deep and defined, with a clear raised rim on its lingual margin; on the M1 a large stylar shelf that diminishes in size substantially posteriorly, until it is hardly noticeable and small parastyle development; presence of well-developed medially positioned hypocone on M1 and M2 among early carnivoramorphan taxa traditionally placed in the paraphyletic 'Miacidae' (many of which also retain the primitive condition of M3/m3, as in this new taxon): Differs from all 'Miacis' (also paraphyletic as traditionally configured) species in its unique combination of the following features: clear diastemata surrounding all premolars except P4; lack of strongly developed parastyle on M1; presence of broad parastylar shelf on M1; absence of strong metastyle on M1 and M2; presence of well-developed, relatively medially positioned hypocone on M1 and M2; well-developed metaconule on M1; strongly developed p4 lingual basin; paraconid and metaconid confluent at their bases on m2; relatively unelongated m2 talonid; and cristid obliqua joins with the protoconid on m3. See 'Discussion' for detailed explication of diagnostic distinctions from individual species currently assigned to 'Miacis'. Differs from Messelogale (tentative distinctions, as Messelogale is predominantly known from deciduous teeth) in: basined lower molars; presence of M3/m3; and diastemata between all premolars. Differs from Miocyon in: the lack of a relatively short and deep mandible; premolars not extremely small when compared to molars; p2 not single rooted; p3 and p4 roughly equal in size; M1 parastyle not large; M2 not elongated anteroposteriorly relative to other taxa; M3 less highly reduced: cusps besides the protocone are identifiable; much smaller than all known specimens of Miocyon. Differs from Oodectes in: accessory cusps on lower premolars; relatively lower crowned premolars with respect to molar trigonid heights; m2–m3 much smaller; P4 parastyle smaller; P4 metastyle wing long; lack of large projecting metastyle or parastyle on M1. Differs from Quercygale in: presence of M3/m3; basined p4; basined lower molars; reduced M1 parastyle; and presence of hypocones. Differs from Palearctonyx in: nonquadrate upper molars; premolars not small when compared to the molars; molars not low crowned with bunodont cusps; P4 protocone located farther anteriorly; and P4 metastyle wing long. Differs from Paramiacis in: presence of hypocone; presence of basined p4; higher trigonid of m1; and paracone and metacone aligned with one another mesiodistally. Differs from Paroodectes in: strongly developed p4 lingual basin; low trigonids on m2 and m3; more highly reduced m3; and a larger P4 metastyle. Differs from Procynodictis in: lack of lingual inflection on lower premolars; lower molar talonids basined; M1 parastyle wing much smaller; paracone set back farther posteriorly on the tooth and larger than the metacone; cingulae not reduced, paraconule and metaconule cristae not reduced, and M3/3 not absent. Differs from Tapocyon in: lack of an elongated parastyle on M1; mandible not exceptionally robust and lacks a deep symphyseal region; M1 protocone not conical; M1 not highly compressed anteroposteriorly; p2 roughly equal in size to p3; m1 talonid relatively wider and possesses more than one posterior talonid cusp; and m1 paralophid not anteroposteriorly directed to the same degree (more transverse in Tapocyon); much smaller than all known specimens of Tapocyon. Differs from Uintacyon in: mandible neither short nor robust and lacks a deep symphyseal region; premolars slightly larger relative to the molars and possess accessory cusps; lower molars have basined talonids; upper molars have well-developed hypocones; parastyle is not well developed; and m3 not flat crowned. Differs from Vassacyon in: mandible neither short nor robust and lacks a deep symphyseal region; premolars slightly larger relative to the molars and possess accessory cusps; lower molars have basined talonids; m2 is reduced; and m3 not flat crowned. Differs from Vulpavus in: non-quadrate shape of upper molars, shearing retained on upper molars; lower molar trigonids not low, and talonid basins not equal to or broader than trigonids. Differs from Xinyuictis in: presence of hypocone on M1; retention of metaconule on M1; wider talonid basins on m1–m2; and a relatively smaller paraconid on m2. Differs from Zodiocyon in: presence of hypocone on M1; M1 with reduction of stylar shelf adjunct to the metacone; larger metaconule on M1; reduction of metastyle on M2; lower molars with basined talonids; and m1 trigonid is less open. (Comparisons based on images and descriptions only). Dawsonicyon isami sp. nov. TEXT-FIG. 1. - TEXT-FIG. 7. Figure TEXT-FIG. 1. Open in figure viewerPowerPoint A–B, Dawsonicyon isami gen. et. sp. nov. holotype DMNH 19585 stereo-pairs of dentition in occlusal view. Scale bar represents 2 cm. Figure TEXT-FIG. 2. Open in figure viewerPowerPoint A–E, Dawsonicyon isami gen. et. sp. nov. holotype DMNH 19585 dentition in side view. A, right view of cranium. B, left view of cranium. C, buccal view of left mandible. D, buccal view of left mandible. E. stereo-pair of lower dentition in occlusal view: restricted to p4-m3. Scale bar represents 2 cm. Figure TEXT-FIG. 3. Open in figure viewerPowerPoint Dawsonicyon isami gen. et. sp. nov. holotype DMNH 19585 petrosal. Line drawing shows hypothesized pattern of the internal carotid artery. Scale bar represents 5 mm. co, cochlea; fc, fenestra cochleae; fv, fenestra vestibuli; ica, internal carotid artery, pa, promontory artery; pro, promontorium; sa, stapedial artery. Figure TEXT-FIG. 4. Open in figure viewerPowerPoint Dawsonicyon isami gen. et. sp. nov. holotype DMNH 19585 full specimen. All identifiable material is laid out in roughly natural positions relative to neighbouring elements. Note that the association of metapodials and phalanxes with fore or hindlimb is uncertain. Scale bar represents 5 cm. Figure TEXT-FIG. 5. Open in figure viewerPowerPoint A–C, Dawsonicyon isami gen. et. sp. nov. holotype DMNH 19585 forelimb elements. A, anterior and lateral views of proximal left ulna. B, anterior and posterior views of left radius. C, anterior and posterior views of left humerus. All scale bars represent 2 cm. Figure B and C share the same scale bar. an, anconeal process; cap, capitulum, ce, capitular eminence, cp; coronoid process, dpc; delto-pectoral crest; gt, greater tuberosity; lt, lesser tuberosity; me, medial epicondyle; rn, radial notch; sp, styloid process; tr, trochlea; ucl, site of ulnar collateral ligament. Figure TEXT-FIG. 6. Open in figure viewerPowerPoint A–C, Dawsonicyon isami gen. et. sp. nov. holotype DMNH 19585 proximal hindlimb elements. A, anterior and posterior view of right tibia. B, anterior and posterior view of left femur. C, lateral view of right innominate. Scale bar represents 2 cm and applies to all elements. cc, cnemial crest; cit, caudal iliac tubercle; gtr, greater trochanter; is, ischial spine; it, ischial tuberosity; ltr, lesser trochanter; pt, patellar trochlea; tt, third trochanter. Figure TEXT-FIG. 7. Open in figure viewerPowerPoint A–B, Dawsonicyon isami gen. et. sp. nov. holotype DMNH 19585 proximal ankle elements. A, right calcaneus in ventral and dorsal views. B, right astragalus in dorsal and ventral view. Scale bar represents 2 cm. af, astragalar foramen; ah, astragalar head; ef, ectal facet; fhl, facet for tendons; pcf, posterior calcaneal facet; pt, peroneal tubercle; sc, sustentaculum; sf, sustentacular facet; tr, astragalar trochlea. Derivation of name. After Isam L. Spaulding Jr., the senior author's paternal grandfather. Holotype. The holotype and only known specimen is DMNH 19585 ( TEXT-FIG. 1. - TEXT-FIG. 7. ), a partial skull, pair of mandibles, and partial postcranial skeleton, comprised of all seven cervical vertebrae, 8 thoracic vertebrae, 5 lumbar vertebrae, the sacrum, 13 caudal vertebrae, distal fragments of both scapulae, right and left humeri, right and left ulna and radius, right lunate, the pelvic girdle, right and left femur, right and left tibia, distal right fibula, right and left astragalius, right and left calcaneius, right cuboid and ectocuniform, and a number of metacarpal or tarsal bones and phalanges that are of uncertain attribution (Collected by RKS and crew, Sweetwater Co, Wyoming, USA). Type horizon. The type and only specimen is from the Black's Fork Member of the Bridger Formation – roughly in the middle of the Bridgerian NALMA, placing it within the middle Eocene, c. 49 to 46.7 Ma (Prothero 1998), in Br-2 (Gunnell et al. 2009). Occurrence and age. 'Bill's Smilodectes BLM locality' (DMNS loc. 885), located in T 16N R 110W, Sweetwater County, Wyoming. Fossils come from a slate green coloured mudstone in the Bridger Formation. The approximately 1-m-thick horizon lies about 4–5 m below Gazin's (1965) Sugar White Layer. The fossil bed is laterally persistent throughout the exposures in this township. The horizon consistently produces specimens of partial skeletons of Smilodectes gracilis, titanotheres, carnivoramorphans, rodents and other mammals. Other mammals from the locality include Smilodectes gracilis, Sciuravus nitidus, Palaeosyops sp., Helaletes sp., Hyrachyus sp., Omomys carteri, Orohippus sp., Hyopsodus sp., Thinocyon muselinus, and Sinopa sp. Diagnosis. As for the genus. Description Lower Dentition. The right mandible preserves c1-p2, a damaged m1, and m2. The left mandible contains i3-m3 ( TEXT-FIG. 1. , TEXT-FIG. 2. ). The i3 has one main central cusp flanked by two small cusps. The canines are large and robust at the base and thin dorsally as they curve posteriorly. All four premolars are separated from their adjacent teeth by diastemata. The premolar series increases in size from p1 to p4, with the p4 being much larger than p3 and p1 much smaller than p2. The anteriorly inclined p1 has a main cusp and one very small posterior accessory cusp. No accessory cusps occur on p2, but a small bump is present on the anterior occlusal surface and a small cingular cusp occurs on the posterior margin. The anterior part of the slightly larger p3 is missing; a small cingular cusp is present on its posterior portion. Both p2 and p3 have small 'basin-like' depressions on their posterior lingual surfaces, but these are not clearly developed. An anterior cingular cusp is present on p4. The p4 also has a well-developed posterior accessory cusp that is separated from the main cusp by a clear notch. There is also a well-developed posterior cingular cusp. The p4 further differs from more anterior premolars by having a cingulum on the buccal margin of the tooth and a well-developed lingual 'talonid' basin bordered by the posterior accessory and cingular cusps as well as a lingual rim. This rim originates from the posterior cingular cusp and runs anteromedially to define the back and side walls of the basin. Because of this basin, the outline of the tooth widens noticeably towards the posterior end. All the premolars have narrow ridges running along their occlusal surfaces parallel to the long axes of the teeth. The ridges on the p4 are less well developed when compared with the anterior premolars. The m1 has a high trigonid with three distinct, well-developed cusps forming an acute angle ('closed' trigonid). The protoconid is the largest cusp, followed by the much smaller paraconid, and the metaconid is the smallest cusp. The paracristid orientation is difficult to determine because of the poor preservation of m1 in both jaws, but it seems to run roughly anteromedially–posterolaterally. The protocristid clearly runs slightly posteromedially. No cingulum is present on the lingual margin of the tooth, and although the buccal margin is heavily damaged, a very weak anterobuccal cingulum can be seen. The talonid is much lower and shorter than the trigonid, while their widths are roughly equal. The sub-vertical cristid obliqua runs from the posterior midpoint of the protocristid to the hypoconid, and has a very well-developed shear facet on its buccal surface. The talonid is simple in its morphology; it has a distinct basin rimmed by the cristid obliqua, hypoconid, hypoconulid, entoconid, and entocristid. The latter two cusps are not highly differentiated from each other and are much smaller than the hypoconid, but they nevertheless are recognizable as distinct cusps. The m2 is roughly half the length of m1, while their widths are similar. The trigonid of m2 is much lower than that of m1, and the protoconid is just barely the largest cusp. The trigonid is somewhat anteroposteriorly compressed, resulting in a 'closed' trigonid basin, where the similarly sized paraconid and metaconid are confluent with one another at their bases. There is a weak cingulum on the buccal border of the tooth, and the hypoconulid and entoconid are not easily differentiated. The talonid basin of m2 is broader and shallower than the corresponding structure on m1. The m3 is roughly half the size of m2 in overall area. This tooth is orientated diagonally relative to the rest of the tooth row because of postmortem deformation and rotation. The occlusal surface features on this tooth are low and rather indistinct; this condition is not because of wear of the tooth surface but rather is the original form of the reduced structure. The readily identifiable features of m3 are the protoconid, cristid obliqua, and a distinct entoconid on the rim of the talonid basin. Upper Dentition. Of the upper dentition, the right I2-C1 and P4-M3 are preserved, with damage to the P4 and M1. On the left side, I2-M2 are present ( TEXT-FIG. 1. , TEXT-FIG. 2. ). As in other basal carnivoramorphans, DMNH 19585 had three pairs of upper incisors, indicated by a combination of premaxilla alveoli and preserved teeth. Only the right I2 can be described in detail; it is curved on its buccal surface, with a straight lingual surface, resulting in a triangular shape in occlusal view. The canines are large and have a slight posterior curvature. The first three premolars have diastemata between them and adjacent teeth; those flanking P1 are the largest. The three anterior premolars are relatively small, increasing steadily in size from P1 to P3. All of the first three premolars have ridges on their occlusal surfaces; anteriorly these ridges run anteromedially to posterolaterally, while posteriorly they run parallel to the long axis of the tooth. P1 is single rooted and slightly procumbent, with a very small bump on its posterior border; its tip is broken. P2 was broken into many fragments but has been fully restored. No accessory cusps are present, and there is a very small posterior cingular cusp; this basal cusp is buccal to the axial ridge and forms a very tiny buccal basin. P3 also lacks an anterior accessory cusp and one definitive posterior accessory cusp; however, a slight rise in the posterior edge of the main cusp could be considered an additional rudimentary accessory cusp. A weak cingulum is present around the entire margin of P3; it is most pronounced on the posterobuccal margin, creating a well-developed posterior cingular cusp that is separated from the main cusp by a clear notch, with a very small associated buccal basin. P4 has a very small protocone, projecting far anterolingually. The posterior edge of the protocone aligns with the middle of the paracone, and anteriorly the protocone barely extends past the front edge of the paracone. The paracone is angled posteriorly and lacks a well-developed parastyle wing or parastylar cusp; only a small cusp arising from the cingulum is present at its anterior margin. The metasylar blade is moderately elongate, buccally directed, possesses an irregular occlusal edge and is clearly separated from the paracone by a well-developed metastylar notch. The whole tooth is ringed by a cingulum, which is slightly better developed on the inner surface of the tooth than elsewhere. The M1 is a transversely elongated rectangle, a standard shape for basal carnivoramorphans, and it does not vary much in width anteroposteriorly or buccolingually. The protocone appears deflected anteriorly by the well-developed hypocone that is formed via a swelling of the cingulum. The hypocone and protocone are roughly the same size. Pre- and post-protocristae lead to the well-formed paraconule and metaconule, respectively. A notch in the cristae separates the paraconule from the protocone while no such feature exists to clearly separate the metaconule. The paraconule is slightly larger than the metaconule and they are well separated by a basin. The bases of the paracone and metacone also are well separated, with the paracone being much larger than the metacone. A large stylar shelf lies buccally to the paracone and metacone. This shelf broadens anteriorly to eventually reach the breadth of the paracone at its base. The metastyle is only very weakly developed, but there is a distinct metastylar cusp. The parastyle is developed to some degree, has a weakly developed stylar cusp and is slightly anteriorly directed. The entire crown is surrounded by a cingulum, which is very well developed on the lingual margin of the tooth, but becomes faint on the buccal side. Both the anterior and posterior cingulae diminish in size at a position about even with the bases of the metacone and paracone buccally. The outer border of the tooth forms a roughly straight line, but with the parastyle projecting slightly in occlusal view. M2 is c. 2/3 the size of M1 in overall area. The parastyle is much more pronounced than in M1, but only projects far in a buccal direction (it has no anterior deflection). A massive hypocone is created by a swelling of the inner cingulum, and is mostly separated from the much smaller protocone via a basin, but a small connecting ridge runs from the apices of the hypocone and protocone. The paracone and metacone are not well separated; the paracone is higher than the metacone. The metaconule is not a distinct cusp, although the paraconule is. There is a small basin on the stylar shelf portion of the parastylar wing. M3 is two-rooted and extremely small, being only about a quarter of the overall size of the M2. The tiny size of this tooth has resulted in the loss of most identifiable features relative to likely ancestral conditions; however, a small trigon basin, the pre-paracrista, and a clear division can still be identified between the protocone region and the paracone/metacone region (see Table 2 for dental measurements). Table 2. Standard dental measurements for DMNH 19585. LP4 7.03 Lp3 3.87 WP4 4.31 Wp3 1.91 MP4 7.07 Lp4 5.29 LM1 5.02 Wp4 2.52 WM1 7.19 Lm1 6.26 MM1 8.2 W
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