Subjects: Biology >> Zoology submitted time 2023-09-20 Cooperative journals: 《古脊椎动物学报》
Abstract： Trilophodon connexus Hopwood, 1935 has long been considered a typical species of Gomphotherium in China. However, due to the unknown state of the mandibular symphysis and tusks, there is no definite evidence to assign “T. connexus” to Gomphotherium. Here we describe and reevaluate a hemimandible from the Halamagai Formation, Ulungur region, northern Junggar Basin, which was previously identified as Gomphotherium cf. G. shensiensis. The mandibular symphysis is deeply troughed and lacks mandibular tusks; therefore, it undoubtedly belongs to the Choerolophodontidae. Further comparison revealed that the cheek tooth morphology is identical to that of the type specimen of Trilophodon connexus. The characteristic features include high bunodonty, elongation of the m3 with four lophids, an only weakly chevroned lophid 2, enlargement of the posterior pretrite central conule 2, unfused state of the pretrite mesoconelet 2 (if present) and anterior pretrite central conule 2, as well as the absence of ptychodonty, choerodonty, and cementodonty. Therefore, T. connexus Hopwood, 1935 is a choerolophodontid rather than a species of Gomphotherium. Based on the above features, we provisionally refer to it as “Choerolophodon” connexus. “Choerolophodon” connexus is characterized by the following features: weak or absent ptychodonty, choerodonty, and loph chevron (which were all strong in the typical species of Choerolophodon), as well as multiplication of the lophids in the m3, which were similar to that of the North American Gnathabelodon. Therefore, Gnathabelodon might represent a distinct lineage within the Choerolophodontidae, and may be derived from the East Asian “Choerolophodon” connexus.
Subjects: Biology >> Zoology submitted time 2022-04-16 Cooperative journals: 《古脊椎动物学报》
Abstract： Platybelodon is the predominant proboscidean of northern China’s Middle Miocene. However, the cranial and cheek tooth morphologies are not clearly diagnosed. In particular, the differential diagnoses between Platybelodon and Gomphotherium have not been comprehensively examined. Here we restudied the cranium previously identified as Gomphotherium shensiense. The upper tusks lack an enamel band, the rostrum is long and narrow, the facial part is rostrally positioned, and a large “prenasal slope” is present. These characters are distinct from those of any species of Gomphotherium, but fit well with some primitive species of Platybelodon, i.e., P. tongxinensis and P. danovi. The molars are also close to the type specimen of P. tongxinensis in the tetralophodont M3 with mesiodistally wide interlophs, curved outline, and a tendency of cementodonty. In this article, we synonymized Gomphotherium shensiense with P. tongxinensis. Moreover, we recognized a new species, Platybelodon tetralophus, from the P. grangeri material collected by the AMHN expedition in Tunggur region. Platybelodon tetralophus differs from P. grangeri and the other species in the tetralophodont M2 and m2, representing the most derived species within Platybelodon. It has only occurred in the uppermost horizon of the Tunggur Formation, i.e., the Tamuqin Fauna (Platybelodon Quarry and Wolf Camp Quarry of AMHN). This work is a comprehensive amending of the genus Platybelodon.
Subjects: Biology >> Zoology submitted time 2021-07-30 Cooperative journals: 《古脊椎动物学报》
Abstract： The mastodont-grade proboscideans represent an important stage in the evolution of the group, establishing the basic pattern of the evolution of the crown groups of proboscideans. The research on mastodons has a history of more than 400 years. The classification and nomenclature have been revised and changed many times, and the problems in their evolution were fully reflected in the history of mastodon nomenclature. In this paper, we undertook a bibliographical research into the nomenclature and etymology of various mastodont groups, reviewing 175 translated Chinese names of mastodont-grade proboscideans, including 12 taxon names higher than the genus level, 46 genera, and 117 species, covering almost all the species of the mastodont radiation. On this basis, we review the principal phylogenetic hypotheses of mastodont interrelationships, and highlight problems in the classification and nomenclature of mastodonts. The evolution of the skull and mandible of mastodons is continuous in all clades, reflecting the same parallel evolution trend; while, although the morphological characteristics of cheek teeth across all lineages are not obvious, they are relatively stable in each lineage. Choerolophodontidae is the most robust monophyletic group within the mastodonts, of which Synconolophus may be a distinct, valid genus. Miomastodon and Pliomastodon of Mammutidae may both be valid, but they are not necessarily the direct ancestor of Mammut americanum. The phylogenetic relationship between Platybelodon danovi, P. grangeri and Aphanobelodon zhaoi within the Amebelodontidae is questionable, depending on whether the lower incisor section of P. danovi is the dentine rod structure or not, while Konobelodon britti in America may be a synonym of Torynobelodon loomisi. The species assigned to Konobelodon in Asia is possibly not amebelodontids, but probably attributable to Paratetralophodon, instead; Serridentinus of Gomphotheriidae may be a valid taxon, representing a trend towards somewhat zygodonty in Gomphotheriidae that terminated with the Cuvieroniinae. The Cuvieroniinae may only include Cuvieronius and Rhynchotherium, while other brevirostrine gomphotheres in America, such as Stegomastodon may have been evolved from a lineage of amebelodonts. Notiomastodon may be related to Sinomastodon, which itself may have originated from Pliomastodon (?) zhupengensis in southern China. The name Mastodon intermedius Teilhard de Chardin & Trassaert, 1937 (now Sinomastoodon intermedius) has the senior primary homonym Mastodon intermedius Eichwald, 1831. We suggest that Sinomastodon intermedius should be replaced with its senior synonym– Sinomastodon sendaicus (Matsumoto, 1924).
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