Table of Content

15 December 2017, Volume 55 Issue 4

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Morphological coevolution of the pygostyle and tail feathers in Early Cretaceous birds

WANG Wei, Jingmai K. O'CONNOR

2017, 55(4):  289-314. 

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The transformation from a long reptilian tail to a shortened tail ending in a pygostyle and accompanied by aerodynamic fanning rectrices is one of the most remarkable adaptations of early avian evolution. However, no fossils directly capture this transition, and information regarding the structural morphology and the early evolution of the pygostyle in Mesozoic birds and their integuments is relatively limited. Here we provide a review of the pygostyle morphology of Early Cretaceous birds with comparison to the structure in living birds. This study emphasizes the convergent evolution of distally co-ossified caudal vertebrae in non-avian maniraptorans and early birds. There further exist distinct differences in pygostyle morphology between Sapeornithiformes, Confuciusornithiformes, Enantiornithes, and Ornithuromorpha. The morphology of the pygostyle and rectrices in early ornithuromorphs appear similar to that of extant birds, whereas the pygostyle in more primitive birds does not appear morphologically capable of supporting the rectricial bulbs and musculature necessary to control an aerodynamic fan-shaped tail. The rectricial bulbs and rectricial fan appear to have coevolved with the plough-shaped pygostyle early in the evolution of the Ornithuromorpha. This study also shows that the confuciusornithiform pygostyle was more similar to that of enantiornithines than previously recognized, consistent with the presence of nearly identical ornamental tail feathers in both groups.

Platacanthomyid remains from the late Cenozoic deposits of East China

QIU Zhu-Ding, Jin Chang-Zhu 

2017, 55(4):  315-330. 

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 Remains of Platacanthomyidae from a late Cenozoic fissure in Fanchang, Anhui, and from the Miocene deposits of Sihong, Jiangsu, China are described. Three species and two genera, including two new species are recognized. They are Neocometes sinensis sp. nov. from Fanchang and Sihong, and N. magna sp. nov. and Typhlomys sp. from Fanchang. The Fanchang assemblage is a mixed sample with elements probably representing an interval spanning from the Early Miocene to the Pleistocene. Judging from fossil content and coloration in the sample, the two species of Neocometes are inferred to be Miocene in age, while the Typhlomys to be later. The joint occurrence of some typical Miocene elements in the assemblage seems to indicate that the Fanchang sample includes an association which can be closely correlated with the Early Miocene Sihong Fauna and the Shanwang Fauna of China, and with the Miocene faunas known from Thailand. Dental characters of Neocomets appear to suggest that the Asian species of the genus have undergone a rapid increase of size, heightening of dental crown, strengthening of ridges, and gradually development of ectoloph in the upper molars and endolophid in the lower molars, representing an evolutionary lineage different from that of Europe. 

Cranial and dental material of Gomphotherium wimani (Gomphotheriidae, Proboscidea) from the Middle Miocene of the Linxia Basin, northwestern China

YANG Xiang-Wen, LI Yu ,  WANG Shi-Qi 

2017, 55(4):  331-346. 

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Introduction to terminologies of tooth enamel microstructures and a proposal for their standard Chinese translations

MAO Fang-Yuan, LI Chuan-Kui, MENG Jin,  LI Qian, BAI Bin, WANG Yuan-Qing, ZHANG Zhao-Qun, ZHAO Ling-Xia, WANG Ban-Yue

2017, 55(4):  347-366. 

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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.  

New fossils of paraceratheres (Perissodactyla, Mammalia) from the Early Oligocene of the Lanzhou Basin, Gansu Province, China

LI Yong-Xiang, ZHANG Yun-Xiang, LI Ji, LI Zhi-Chao, XIE Kun

2017, 55(4):  367-381. 

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