University Museum of Zoology Cambridge, Downing Street, Cambridge, CB2 3EJ, UK.
School of Life and Environmental Sciences, University of Lincoln, Joseph Banks Laboratories, Green Lane, Lincoln, LN6 7DL, UK.
Commun Biol. 2022 Apr 14;5(1):283. doi: 10.1038/s42003-022-03199-x.
The taxonomically diverse terrestrial tetrapod fauna from the late Mississippian East Kirkton Limestone includes the earliest known members of stem Amphibia and stem Amniota. Here we name and describe a new East Kirkton tetrapod with an unusual hindlimb morphology reminiscent of that of several stem- and primitive crown amniotes. It displays a unique ilium with two slender and elongate processes and a 5-digit pes with a long, stout metatarsal IV and a greatly elongate digit IV. The new taxon broadens our knowledge of East Kirkton tetrapods, adding to the remarkable diversity of their hindlimb constructions, functional specializations, locomotory modes, and adaptations to a wide variety of substrates. An unweighted character parsimony analysis places the new taxon in a polytomy alongside some other Carboniferous groups. Conversely, weighted parsimony and Bayesian analyses retrieve it among the earliest diverging stem amniotes, either as the basalmost anthracosaur or within a clade that includes also Eldeceeon and Silvanerpeton, crownward of an array of chroniosaurs plus anthracosaurs.
来自晚密西西比期东柯克顿灰岩的分类多样的陆生四足动物群包括了最早被发现的原两栖类和原羊膜动物的成员。这里我们命名并描述了一种新的东柯克顿四足动物，它具有不寻常的后肢形态，让人联想到一些原蜥形类和原始的有鳞类。它具有一个独特的骼骨，带有两个细长的突起，以及一个具有长而粗壮的第四跖骨和极度伸长的第四趾的五趾蹠骨。这个新的分类单元拓宽了我们对东柯克顿四足动物的认识，增加了它们后肢结构、功能特化、运动模式以及对各种基质的适应的显著多样性。非加权字符简约分析将这个新的分类单元置于一个与其他一些石炭纪群体的并系群中。相反，加权简约和贝叶斯分析将其置于最早分化的原羊膜动物中，要么是最基础的坚蜥类，要么是包括 Eldeceeon 和 Silvanerpeton 的一个分支，位于一系列似鳄龙类加上坚蜥类的上方。
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