来自意大利/瑞士蒙特圣乔治中三叠世贝萨诺组的（爬行纲：鱼龙目）的颅后解剖结构，及其对重建三叠纪鱼龙游泳方式的意义。

Postcranial anatomy of (Reptilia: Ichthyosauria) from the Middle Triassic Besano Formation of Monte San Giorgio (Italy/Switzerland), with implications for reconstructing the swimming styles of Triassic ichthyosaurs.

作者信息

Bindellini Gabriele, Wolniewicz Andrzej S, Miedema Feiko, Dal Sasso Cristiano, Scheyer Torsten M

机构信息

Dipartimento di Scienze della Terra "Ardito Desio", Università degli Studi di Milano, Milan, Italy.

Dipartimento di Scienze della Terra, Sapienza Università di Roma, Rome, Italy.

出版信息

Swiss J Palaeontol. 2024;143(1):32. doi: 10.1186/s13358-024-00330-9. Epub 2024 Sep 10.

UNLABELLED

Dal Sasso & Pinna, 1996 was originally described on the basis of a single complete fossil specimen excavated near Besano (Italy). However, a recent taxonomic revision and re-examination of the cranial osteology allowed for the assignment of five additional specimens to the taxon. Here, we analyse, describe and discuss the postcranial anatomy of in detail. The size of the specimens examined herein ranged from slightly more than one meter to eight meters. Overall, several diagnostic character states for this taxon are proposed, demonstrating a mosaic of plesiomorphic and derived features. This is best exemplified by the limbs, which show very rounded elements in the forelimbs, and pedal phalanges with retained rudimentary shafts. We suggest that the widely spaced phalanges in the forefins of were embedded in a fibrocartilage-rich connective tissue, like in modern cetaceans. We also review the similarities of with and allowing us to conclude that is not a junior synonym of either of the two taxa. Lastly, to test the swimming capabilities of , we expanded on a previously published study focussing on reconstructing the swimming styles of ichthyosaurs. was found to possess a peculiar locomotory mode, somewhat intermediate between anguilliform swimmers, such as and , and some shastasaur-grade (e.g., ) and early-diverging euichthyosaurian (e.g., ) ichthyosaurs. Based on our results, we furthermore suggest that mixosaurids acquired their characteristic body profile (dorsal fin and forefins that are distinctly enlarged compared to the hindfins) independently and convergently to the one that later appeared in Parvipelvia. Moreover, the different swimming styles inferred for Mixosauridae and strengthen the earlier hypothesis of niche partitioning among these three distinct ichthyosaur taxa from the Besano Formation.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1186/s13358-024-00330-9.

未标注

达尔·萨索和皮纳在1996年最初是根据在贝萨诺（意大利）附近挖掘出的一个完整化石标本进行描述的。然而，最近的分类修订和对头骨骨学的重新检查使得另外五个标本也被归入该分类单元。在此，我们详细分析、描述并讨论了[该物种名称未给出]的颅后解剖结构。本文所研究标本的大小从略超过一米到八米不等。总体而言，我们提出了该分类单元的几个诊断特征状态，显示出原始特征和衍生特征的镶嵌组合。这在四肢上体现得最为明显，前肢的骨骼非常圆润，而趾骨保留了基本的骨干。我们认为，[该物种名称未给出]前鳍中趾骨间距较大，像现代鲸类一样，嵌入富含纤维软骨的结缔组织中。我们还回顾了[该物种名称未给出]与[其他两个物种名称未给出]的相似性，从而得出结论：[该物种名称未给出]不是这两个分类单元中任何一个的次异名。最后，为了测试[该物种名称未给出]的游泳能力，我们在之前一项专注于重建鱼龙游泳方式的已发表研究基础上进行了拓展。结果发现，[该物种名称未给出]具有一种独特的运动模式，在某种程度上介于鳗形游泳者（如[其他物种名称未给出]）和一些沙斯塔龙级（如[其他物种名称未给出]）以及早期分化的真鱼龙类（如[其他物种名称未给出]）鱼龙之间。基于我们的研究结果，我们进一步认为，混鱼龙科获得了其独特的身体形态（背鳍和前鳍相比后鳍明显增大），这是独立且趋同于后来在小鳍鱼龙类中出现的形态。此外，为混鱼龙科和[其他物种名称未给出]推断出的不同游泳方式，强化了关于贝萨诺组这三个不同鱼龙分类单元之间生态位划分的早期假说。