分类： 生物学 >> 动物学 提交时间： 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要： New fossils pertaining to the oldest known Asian plesiadapiform, the Gashatan carpolestid Subengius mengi, clarify aspects of the dental anatomy of this taxon. The dentition of S. mengi is substantially more primitive than previously recognized in retaining a lower dental formula of 2.1.3.3, a low-crowned p4 with three main cusps that are less fully connate than their counterparts in species of Elphidotarsius, P3 with a narrower and structurally simpler lingual margin, and in lacking widely splayed paraconid and metaconid on m1. The unique structure of P3 in S. mengi and a reassessment of P3 anatomy in Elphidotarsius sp., cf. E. florencae, suggest that certain cusp homologies on P3 in Carpolestidae have been misinterpreted in the past. Following a detailed character analysis, the phylogenetic relationships of carpolestids and their close relatives are reconstructed. The Bumbanian taxon Chronolestes simul is recovered as the most basal member of Carpolestidae. S. mengi and a second Bumbanian taxon, Carpocristes oriens, also appear to be relatively basal members of the carpolestid radiation, although none of these Asian carpolestid taxa seems to be specially related to each other. Dispersal of carpolestids between Asia and North America appears to have been restricted to earlier parts of the Paleocene, although carpolestids survived on both continents until sometime near the Paleocene–Eocene boundary.
分类： 生物学 >> 动物学 提交时间： 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要： Here we report a new genus and species, Mina hui gen. et sp. nov., of basal Glires from the Middle Paleocene of Qianshan, Anhui, China. The new taxon is characterized by combination of the following characters: medium-sized mimotonidan; upper dental formula 2.0.3.3; d I2 transversely narrow and having smooth labial surface without longitudinal groove; M1 the largest cheek tooth and other cheek teeth decreasing in size considerably away from M1 so that the external margin of the upper cheek tooth row is distinctly arched labially; lingual side of upper molars unilaterally hypsodont and bearing no hypostria; hypocone being slightly distolingual to protocone; presence of a mesostyle; upper incisor with double-layered enamel structure; posterior border of anterior root of zygoma situated lateral to M1–2 and infraorbital foramen positioned low. M. hui is one of the earliest known Glires, co-existing with Heomys and Mimotona in Qianshan geographically and Middle Paleocene (ca. 61 Ma) chronologically. We consider that the Mimotonida would include two families: the monotypic Mimotonidae that contains Mimotona and Mimolagidae that includes Mimolagus, Gomphos, Anatolimys, Mina and possibly Amar aleator. Among known mimotonidans, Mimotona probably represents a primitive “morphotype” as the ancestor of lagomorphs, whereas Mimolagidae includes a side branch diverged from the clade evolved toward lagomorphs. Future research may show that Mimolagidae is not a natural group, and may possibly submerge into Mimotonida, or involve more than one family-level clade. The occurrence of Heomys, Mimotona and Mina from Qianshan show that Glires had already diversified by the Middle Paleocene.
分类： 生物学 >> 动物学 提交时间： 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要： A unique canal (calcaneal canal) running diagonally through the calcaneus was commonly considered as characteristic for lagomorphs, both extant and fossil, but absent in rodents and other pertinent lagomorph relatives. However, our investigation of a calcaneus from the Middle Paleocene of Qianshan, Anhui Province and specimens previously grouped in Mimotonidae also shows presence of canals on calcaneus bones. To further explore the unique character, we scanned calcanei of Ordolagus, Mimolagus, Gomphos, Rhombomylus, and Oryctolagus using micro CT and investigated the calcanei of some other related taxa under microscope. Three-dimensional reconstructions of the calcanei based on CT data of these taxa confirmed the presence of apertures traversing the large medullary cavity. The diagonally oriented calcaneal canal is present not only in lagomorphs, but also in non-lagomorph duplicidentates, such as Mimotona, Gomophos, and simplicidentates, such as Rhombomylus, though smaller in size. Hence, the presence of calcaneal canal may be one of the synapomophic characters for Glires, not only for the order Lagomorpha. The shared calcaneus character confirms the close relationship between Simplicidentata and Duplicidentata.
点击量
点击量
下载量
评论
