Craniodental and postcranial morphology of <i>Indohyaenodon raoi</i> from the early eocene of india, and its implications for ecology, phylogeny, and biogeography of hyaenodontid mammals

ABSTRACTNew remains of the early Eocene hyaenodontid <i>Indohyaenodon raoi</i> are described from the Vastan Lignite Mine in Gujarat, western India, including the first known rostrum, upper dentition, and postcrania, substantially expanding our knowledge of the species and providing insights into its functional morphology and relationships. Craniodental morphology suggests that <i>I. raoi</i> had a broad diet, including non-vertebrate material as well as flesh of a diversity of prey species. Postcranial morphology is broadly similar to that of other early hyaenodontids and suggests a scansorial locomotor repertoire. Dental morphology indicates that <i>I. raoi</i> is closely related to other South Asian hyaenodontids, with shared features including strong cingula, narrow premolars, and a reduced P4 protocone. We present the most comprehensive phylogenetic analysis of Hyaenodontidae to date, which corroborates this relationship but finds South Asian hyaenodontids to be the stem of a group that includes most African hyaenodontids. This and other higher-level relationships within Hyaenodontidae are, however, weakly supported, and substantially different alternative hypotheses of relationships are not significantly less parsimonious, reflecting strong character conflict. Factors contributing to this conflict include the isolation of hyaenodontid faunas on different continents during much of the Eocene, canalization and simplification of carnivorous dentitions, and a lack of non-dental material for critical hyaenodontid groups. The new phylogeny is consistent with either an African or an Asian origin for the group.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at http://www.tandfonline.com/UJVP摘要 本文记述了采自印度西部古吉拉特邦Vastan褐煤矿的早始新世鬣齿兽科（Hyaenodontidae）*Indohyaenodon raoi*的新材料，包含该物种首个被发现的吻部、上牙列及颅后骨骼，大幅拓展了学界对该物种的认知，并为其功能形态学与系统发育关系的研究提供了新的见解。颅齿形态学特征表明，*I. raoi*的食性广泛，既包含无脊椎动物类群，也涵盖多种猎物的肌肉组织。其颅后骨骼形态与其他早始新世鬣齿兽科类群整体相似，表明该物种具备攀援型运动能力。牙齿形态学特征显示，*I. raoi*与其他南亚鬣齿兽科类群亲缘关系密切，二者共有的形态特征包括发达的齿带、窄小的前臼齿以及缩小的上第四前臼齿原尖。本文开展了迄今最为全面的鬣齿兽科系统发育分析，验证了上述亲缘关系，同时发现南亚鬣齿兽类构成包含绝大多数非洲鬣齿兽类群的演化支的基干类群。不过，该类群及鬣齿兽科内其他高阶元系统发育关系的支持度均较低，且大量差异显著的替代亲缘关系假说的简约性得分并无显著劣势，这反映出强烈的性状冲突。造成此类性状冲突的因素包括：始新世大部分时段内，鬣齿兽科类群在各大陆间的地理隔离；肉食性哺乳动物齿列的渠化演化与简化；以及关键鬣齿兽科类群缺乏非齿类形态材料。新的系统发育假说支持该类群既可能起源于非洲，也可能起源于亚洲。补充数据——本文的补充材料可通过http://www.tandfonline.com/UJVP 免费获取