A Re-Description of 'Mycterosaurus' smithae, an Early Permian Eothyridid, and Its Impact on the Phylogeny of Pelycosaurian-Grade Synapsids.
A Re-Description of 'Mycterosaurus' smithae, an Early Permian Eothyridid, and Its Impact on the Phylogeny of Pelycosaurian-Grade Synapsids.
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DOI：
10.1371/journal.pone.0156810
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Fröbisch J
中科院分区：
文献类型：
--
作者：
Brocklehurst N;Reisz RR;Fernandez V;Fröbisch J
“Mycterosaurus”smithae，来自科罗拉多的Cisuralian（二叠纪早期），于1965年首次被描述为Mycterosaurus属的第二个物种。该属的模式种M. longiceps，经多分支系统分析表明属于基联会科Varanopidae，'M.'史密斯自其最初的描述以来，在很大程度上被忽视了。额外的准备工作和同步辐射扫描揭示了新的重要信息，支持将该物种分配到一个新属：Vaughnictis gen. nov. Vaughnictis缺乏Mycterosaurines和Varanopids的许多特征：它缺乏细长的股骨，舌唇压缩和强烈内弯的牙齿，以及这个家庭的眶后特征的侧凸。相反，它具有冠状齿，一个大的颞上，和一个大的松果体孔位于中间沿着长度的顶骨，功能支持其分配到Eothyrididae。此外，颅后骨与Eothyridid Oedaleops有许多共同特征。最近发表的一个扩展版本的系统发育分析pelycosaurian-grade synapsids的位置Vaughnictis作为姐妹分类群的Eothyris内的分支Eothyrididae。新增加的关于始甲科后颅的资料，以及最近描述的基底型原甲科的资料，证实了最近有争议的原甲龙类是最基底的联会动物的地位。由于简约性分析产生低支持度值，并且由于缺失数据而缺乏分辨率，因此使用贝叶斯和隐含权重方法进行了额外分析，这些方法产生了更好的分辨率和与更高支持度值的关系。虽然结果是相似的，但贝叶斯分析提出了莫斯科时代（石炭纪）的神秘突触棘齿动物的替代位置;简约分析发现它是蛇齿亚目，而贝叶斯和隐含权重分析发现它是楔形亚目的姐妹。
‘Mycterosaurus’ smithae, from the Cisuralian (early Permian) of Colorado, was first described in 1965 as a second species of the genus Mycterosaurus. While the type species of this genus, M. longiceps, has been shown by multiple cladistic analyses to belong to the basal synapsid family Varanopidae, ‘M.’ smithae has been largely ignored since its original description. Additional preparation and synchrotron scanning has revealed new significant information that supports the assignment of this species to a new genus: Vaughnictis gen. nov. Vaughnictis lacks many of the characteristics of mycterosaurines and varanopids in general: it lacks the slender femur, the linguo-labially compressed and strongly recurved teeth, and the lateral boss on the postorbital characteristic of this family. Instead, it possesses coronoid teeth, a large supratemporal, and a large pineal foramen positioned midway along the length of the parietal, features that support its assignment to Eothyrididae. Moreover, the postcranium shares many characters with the eothyridid Oedaleops. An expanded version of a recently published phylogenetic analysis of pelycosaurian-grade synapsids positions Vaughnictis as the sister taxon of Eothyris within the clade Eothyrididae. The addition of data on the postcranium of eothyridids and the inclusion of the recently-described basal caseid Eocasea confirms the recently-disputed position of caseasaurs as the most basal synapsids. As the parsimony analysis produced low support values and a lack of resolution due to missing data, additional analyses were undertaken using Bayesian and Implied Weights methods, which produced better resolution and relationships with higher support values. While the results are similar, alternative positions for the enigmatic Moscovian age (Carboniferous) synapsid Echinerpeton are suggested by Bayesian analysis; the parsimony analysis found it to be an ophiacodontid, while the Bayesian and Implied Weights analysis found it to be the sister to the Sphenacomorpha.