Sookias Roland B, Böhmer Christine, Clack Jennifer A
School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom; GeoBio-Center, Ludwig-Maximilians-Universität München, München, Germany.
GeoBio-Center, Ludwig-Maximilians-Universität München, München, Germany; Dept. für Geo- und Umweltwissenschaften, Ludwig-Maximilians-Universität München, München, Germany; Bayerische Staatssammlung für Paläontologie und Geologie München, München, Germany.
PLoS One. 2014 Oct 7;9(10):e109717. doi: 10.1371/journal.pone.0109717. eCollection 2014.
The lower jaw of an unidentified Pennsylvanian (Late Carboniferous) tetrapod from Nova Scotia--the "Parrsboro jaw"--is redescribed in the light of recent tetrapod discoveries and work on evolution of tetrapod mandibular morphology and placed for the first time in a numerical cladistics analysis. All phylogenetic analyses place the jaw in a crownward polytomy of baphetids, temnospondyls, and embolomeres. Several features resemble baphetids and temnospondyls including dermal ornamentation, absence of coronoid teeth, and presence of coronoid shagreen. Dentary dentition is most similar to Baphetes. An adsymphysial toothplate may not preclude temnospondyl affinity. An apparent large exomeckelian fenestra, with the dorsal foraminal margins formed by an unossified element, echoes the morphology of the stem tetrapod Sigournea and is unusually primitive given the other features of the jaw. The jaw may thus provide an example of an intermediate stage in Meckelian element evolution.
根据近期的四足动物发现以及有关四足动物下颌形态演化的研究，对来自新斯科舍省的一块未鉴定的宾夕法尼亚纪（石炭纪晚期）四足动物的下颌骨——“帕尔斯伯勒下颌骨”——进行了重新描述，并首次将其纳入数值分支系统学分析。所有系统发育分析都将这块下颌骨置于巴菲蒂类、离片锥类和迷齿类的冠部多歧分类中。它的几个特征与巴菲蒂类和离片锥类相似，包括皮肤纹饰、无冠状齿以及有冠状鲨革。齿骨齿列与巴菲蒂斯最为相似。联合齿板的存在并不排除其与离片锥类的亲缘关系。一个明显较大的外梅克尔孔，其背侧孔缘由一个未骨化的元素形成，这与基干四足动物西格诺尼亚的形态相似，并且鉴于下颌骨的其他特征，这是异常原始的。因此，这块下颌骨可能提供了一个梅克尔元素演化中间阶段的例子。
