Dimorphism of Bivalved Arthropod Branchiocaris？ Yunnanensis from the Early Cambrian Chengjiang Biota, South China  

作　　者：WU Yu FU Dongjing ZHANG Xingliang Allison C. DALEY SHU Degan 

机构地区：[1]Early Life Institute and State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi 'an 710069, China [2]Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK [3]Oxford University Museum of Natural History, Parks Road, Oxford OX1 3PW, UK

出　　处：《Acta Geologica Sinica(English Edition)》2016年第3期818-826,共9页地质学报（英文版）

基　　金：financed by the Major Basic Research Project of the Ministry of Science and Technology of China (Grants 2013CB837100, 2013CB806400);the Natural Science Foundation of China (Grants 41202007, 41272019 and 40830208)

摘　　要：The bivalved arthropod Branchiocaris？ yunnanensis Hou, 1987 is redescribed on the basis of new fossil material from the early Cambrian Chengjiang biota, South China. In total, 81 specimens have been examined. The carapace comprises two identical valves, each valve are sub-circular in outline, ranging from 24 mm to 58 mm in length, and from 15 mm to 46 mm in height. The dorsal margin is straight and bears two short cardinal spines. The valve surface is either smooth or ornamented with polygonal reticular structures, which may result from different preservation conditions. Two morphotypes have been recognized based on the presence or absence of a subdorsal swelling of the valve, which is convex dorsolaterally and extends beyond the dorsal margin when it appears. Statistic and ontogenetic analyses show both morphotypes grow isometrically and have the same growth trajectory. Therefore, the two morphotypes are interpreted as dimorphism within the same species. Our results are helpful for investigating the taxonomy and ontogeny of arthropod fossils and suggest that dimorphism might be fairly common in these early arthropods.The bivalved arthropod Branchiocaris？ yunnanensis Hou, 1987 is redescribed on the basis of new fossil material from the early Cambrian Chengjiang biota, South China. In total, 81 specimens have been examined. The carapace comprises two identical valves, each valve are sub-circular in outline, ranging from 24 mm to 58 mm in length, and from 15 mm to 46 mm in height. The dorsal margin is straight and bears two short cardinal spines. The valve surface is either smooth or ornamented with polygonal reticular structures, which may result from different preservation conditions. Two morphotypes have been recognized based on the presence or absence of a subdorsal swelling of the valve, which is convex dorsolaterally and extends beyond the dorsal margin when it appears. Statistic and ontogenetic analyses show both morphotypes grow isometrically and have the same growth trajectory. Therefore, the two morphotypes are interpreted as dimorphism within the same species. Our results are helpful for investigating the taxonomy and ontogeny of arthropod fossils and suggest that dimorphism might be fairly common in these early arthropods.

关 键 词：ARTHROPODA Branchiocaris DIMORPHISM ONTOGENY Chengjiang biota 

分 类 号：Q915[天文地球—古生物学与地层学]