Fischer V, Benson R B J, Druckenmiller P S, Ketchum H F, Bardet N
Department of Geology, Université de Liège, 14 allée du 6 Août, Liège 4000, Belgium.
Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK.
R Soc Open Sci. 2018 Mar 28;5(3):172177. doi: 10.1098/rsos.172177. eCollection 2018 Mar.
Polycotylidae is a clade of plesiosaurians that appeared during the Early Cretaceous and became speciose and abundant early in the Late Cretaceous. However, this radiation is poorly understood. from the Middle Turonian of Morocco is an enigmatic taxon possessing an atypically long neck and, as originally reported, a series of unusual cranial features that cause unstable phylogenetic relationships for polycotylids. We reinterpret the holotype specimen of and clarify its cranial anatomy. possesses an extensive, foramina-bearing jugal, a premaxilla-parietal contact and carinated teeth. Phylogenetic analyses of a new cladistic dataset based on first-hand observation of most polycotylids recover and as successive lineages at the base of the earliest Late Cretaceous polycotyline radiation. A new dataset summarizing the Bauplan of polycotylids reveals that their radiation produced an early burst of disparity during the Cenomanian-Turonian interval, with marked plasticity in relative neck length, but this did not arise as an ecological release following the extinction of ichthyosaurs and pliosaurids. This disparity vanished during and after the Turonian, which is consistent with a model of 'early experimentation/late constraint'. Two polycotylid clades, Occultonectia clade nov. and Polycotylinae, survived up to the Maastrichtian, but with low diversity.
薄板龙科是蛇颈龙类的一个分支，出现在早白垩世，并在晚白垩世早期变得种类繁多且数量丰富。然而，这种辐射情况却鲜为人知。来自摩洛哥土伦阶中期的[该物种名称未给出]是一个神秘的分类单元，拥有异常长的颈部，并且如最初报道的那样，具有一系列不寻常的颅骨特征，这导致薄板龙科的系统发育关系不稳定。我们重新解释了[该物种名称未给出]的正模标本，并阐明了其颅骨解剖结构。[该物种名称未给出]具有一个广泛的、有孔的颧骨、前上颌骨 - 顶骨接触以及具嵴的牙齿。基于对大多数薄板龙科的第一手观察建立的一个新的分支数据集进行的系统发育分析，将[该物种名称未给出]和[该物种名称未给出]作为最早晚白垩世薄板龙类辐射基部的连续谱系。一个总结薄板龙科形态结构的新数据集表明，它们的辐射在森诺曼阶 - 土伦阶期间产生了早期的差异爆发，相对颈部长度具有显著的可塑性，但这并非鱼龙类和上龙类灭绝后的生态释放所致。这种差异在土伦阶期间及之后消失，这与“早期实验/晚期限制”模型一致。两个薄板龙科分支，新的隐匿颈龙类分支和薄板龙亚科，存活至马斯特里赫特阶，但多样性较低。
