新发现的长吻型离龙(双孔亚纲:离龙目)幼年个体——袖珍蒙山龙,兼论新离龙类的个体发育
A juvenile skull of the longirostrine choristodere(Diapsida:Choristodera),Mengshanosaurus minimus gen.et sp.nov.,with comments on neochoristodere ontogeny
摘要
Abstract
Choristoderes were an important clade of semi-aquatic predators that occupied Laurasian freshwater ecosystems from the Middle Jurassic to the Miocene.During the Early Cretaceous,the neochoristodere lineage evolved large size and long snouts,converging on the body plan of modern crocodilians.Here,we describe a new longirostrine choristodere,Mengshanosaurus minimus gen.et sp.nov.from the Lower Cretaceous Mengyin Formation of Shandong Province,China.The holotype is the smallest reported neochoristodere individual,with a skull length of only 35 mm.The poorly ossified braincase,along with retention of a fontanel at the frontal-parietal suture,indicates this individual was a juvenile.Phylogenetic analyses recovered Mengshanosaurus as a neochoristodere,a placement supported by the presence of a single narial opening,fusion of the nasals,and expansion of the temporal fenestrae.In the Neochoristodera,Mengshanosaurus is sister to a clade consisting of Ikechosaurus,Tchoiria,Simoedosaurus,and Champsosaurus.It differs from other neochoristoderes in having the lacrimal foramen between the prefrontal and lacrimal,in addition to having large vomerine teeth(exceeding one-third the width of corresponding maxillary teeth).The closely arranged marginal teeth and large vomerine teeth suggest juvenile choristoderes may have fed on invertebrates and insects,similar to juveniles of modern crocodilians.However,the observation that very young neochoristoderes had similar skull proportions and marginal tooth shapes to adults,along with features suggesting a more fully aquatic ecology,suggest that neochoristoderes exhibited less pronounced ontogenetic niche shifts than modern crocodilians.关键词
山东新泰/早白垩世/蒙阴组/新离龙类Key words
Xintai,Shandong/Early Cretaceous/Mengyin Formation/Neochoristodera分类
生物科学引用本文复制引用
袁梦,李大庆,Daniel T.KSEPKA,易鸿宇..新发现的长吻型离龙(双孔亚纲:离龙目)幼年个体——袖珍蒙山龙,兼论新离龙类的个体发育[J].古脊椎动物学报,2021,59(3):213-228,16.基金项目
中国科学院战略性先导科技专项(编号:XDA19050102,XDB18030504,XDB26000000)、中国科学院"率先行动"项目、国家自然科学基金青年科学基金(批准号:41702020)和国家自然科学基金基础科学中心项目(批准号:41688103)资助.The CT scanning was performed at Shanghai Yinghua NDT Equipment Trade Co.,Ltd.We thank Inner Mongolia Museum of Natural History for access to the Ikechosaurus sunailinae specimen under their curation.We thank Mark Norell and the Paleontology Department at the American Museum of Natural History for providing specimen access and CT data of Tchoiria klauseni.The CT data of Champsosaurus lindoei(CMN 8920)were accessed on MorphoSource(https://www.morphosource.org/media/000085093).We further thank Thomas Dudgeon for sharing the CT data of CMN 8920 and Canadian Museum of Nature,Ottawa for collecting.GUO Rui(IVPP)completed the neochoristodere skull reconstruction and life reconstruction of the new species.The project is funded by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA19050102,XDB18030504,XDB26000000),the Chinese Academy of Sciences Pioneer grants,the National Natural Science Foundation of China(Grant No.41702020 and 41688103). （编号:XDA19050102,XDB18030504,XDB26000000）
