分类： 地球科学 >> 地质学 提交时间： 2018-01-25 合作期刊: 《古脊椎动物学报》
摘要： Deperetellidae are a group of common, endemic Asian Middle Eocene tapiroids. Although five genera within the family have been named, most of them were represented by fragmentary maxillae and mandibles except for some skeletal material of Deperetella. Based exclusively on dental characters, different authors have proposed affinities of deperetellids with, for instance, helaletid Colodon, lophialetids, or rhodopagids. Here we described the partial postcranial skeleton of Teleolophus medius? recently discovered at Wulanhuxiu (=Ulan Shireh) of the Erlian Basin, China, and compared the postcranial skeletons of Teleolophus with those of Lophialetes, Deperetella, Heptodon, Helaletes, and Colodon. The postcranial skeleton of Teleolophus shares many similarities with that of Deperetella especially in having elongated and slender limbs, a relatively long, narrow lunar with a slightly concave medial border of the radial facet, a magnum with an anteriorly situated hump and a deeply excavated Mc IV facet, Mc II not elevated above Mc III, a slightly asymmetric trochlea of the femur, a fibula highly reduced or even fused with a tibia, Mt III contacting the cuboid, Mt II in contact with ectocuneiform only on the posterior end, and the manus and pes with functional tridactyls. These similarities support the close relationship between Teleolophus and Deperetella. We interpreted some similarities of postcrania between Teleolophus and Lophialetes as a result of parallel evolution, due to their cursorial adaptations. Colodon is more similar to Heptodon than to Teleolophus in the postcranial features, suggesting a close relationship between Colodon and Heptodon. Whether or not Helaletidae and Deperetellidae are closely related await further investigation. Both morphological characters and ternary diagram indicate that Teleolophus adapted to fast running, as its contemporary Lophialetes.
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： The incisor enamel microstructure of Mina hui Li et al., 2016 from the upper Wanghudun Formation, Middle Paleogene of Qianshan, Anhui is described following the hierarchical system ranging from crystallites to Schmelzmuster. The enamel sample was taken from the upper incisor of the holotype. The enamel consists of a very thin prismless external layer, a relatively thick outer layer (PE) with radial enamel and an inner layer (PI) with multilayered Hunter-Schreger bands (HSB). The thickness of HSB is irregular and the inclination has a small angle; no transition zones between the HSB; prism cross sections are irregularly round; interprismatic matrix is very thick with crystallites in the PE running parallel to the prism long axes. These characters resemble pauciserial HSB in rodents. Ribbon-like prism seams and convergent crystallite discontinuities are consistent in different portions of the enamel, which are interpreted as a primitive feature for Glires, or even placental mammals. Compared with known enamel structure of basal Glires, the enamel of Mina stands for the earliest known evidence of double-layered enamel of the group. It indicates that the early evolution of Glires and placental mammals is complex and adds more details to the enamel microstructure of the earliest Glires.
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.
分类： 地球科学 >> 地质学 提交时间： 2017-09-28 合作期刊: 《古脊椎动物学报》
MAO Fang-Yuan
LI Chuan-Kui
MENG Jin
LI Qian
BAI Bin
WANG Yuan-Qing
ZHANG Zhao-Qun
ZHAO Ling-Xia
WANG Ban-Yue
摘要： Tooth enamel is composed of elongated, hexagonal crystallites of hydroxyapatite. Some crystallites are arranged into various regual structures and futher formed a composite structure in a hierarchical manner. The hierarchical system can provide a basis for analysis different levels of structural complexity from varitaiton of particular crystallite strucutes to variation of structural types throughout a individual’s dentition. The size, orientation, distribution and the packing patterns of crystallites are gene-comtrolled and have limited range of intraspecific variability. Thus, these microstructures provide considerable and reliable morphological characters that help understanding of external dental morphology in context of both phylogeny and function in vertebrates. Because teeth are highly resistant to weathering, mainly owing to their enamel covering, so that they were commonly preserved as fossils. This organic system, particularly their microstructures, has attracted more and more attention from vertebrate paleontologists and other morphologists. However, as already recognized by many previous studies, some terminologies of the enamel microstructures have been complex and used inconsistently. Although considerable effort has been made to study enamel microstructures in China during the last few decades, a standard terminology of enamel microstructures in Chinese has not be formally brought into line with that in English literatures. Here we intend to introduce and systematize the relevant terminology used in the study of enamel microstructures and translate them into Chinese, in hoping that this systematic effort will enhance researches of enamel microstructures in China. 脊椎动物牙齿釉质显微结构具丰富的形态学特征，承载着系统发育和生物力学等方面的信息。本文在前人的研究基础上，试图系统地介绍牙釉质显微结构的基本内容，提出牙釉质研究中相关术语的中文译名建议，并对一些重要术语做了简要解释，供相关研究者参考，以期促进牙釉质显微结构研究的进一步发展。
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