Jasinski Steven E
Department of Earth and Environmental Science, University of Pennsylvania, Philadelphia, PA, USA.
Section of Paleontology and Geology, State Museum of Pennsylvania, Harrisburg, PA, USA.
PeerJ. 2018 Feb 13;6:e4338. doi: 10.7717/peerj.4338. eCollection 2018.
(Testudines: Emydidae) represents one of the most well-known turtle genera today. The evolution of , while being heavily documented with fossil representatives, is not well understood. Numerous fossils from the late Hemphillian Gray Fossil Site (GFS) in northeastern Tennessee help to elucidate its evolution. The fossil at the GFS represent a new species. The new taxon, , is described, and currently represents the most thoroughly described fossil emydid species known. A phylogenetic analysis, including 31 species, focusing on the subfamily Deirochelyinae is performed that includes the new fossil species, along with numerous other modern and fossil deirochelyine species, representing the first phylogenetic analysis published that includes several fossil deirochelyines. The phylogenetic analysis, utilizing morphological evidence, provides monophyletic clades of all modern deirochelyines, including , , , , , and . A strict consensus tree finds the recently described fossil species to be part of a clade of + . Three fossil taxa, including one previously referred to () and two to ( and ) are found to form a clade with modern , with sister to the other members of the clade. is found to be part of a basal polytomy with in relation to other deirochelyine taxa. Two fossil taxa previously referred to ( and ) form a paraphyly with the modern and , and may be referable to distinct genera. Additionally, fossil taxa previously attributed to (, , , and ) and are found to form a clade separate from clades of northern and southern species, potentially suggesting a distinct lineage of with no modern survivors. Hypotheses of phylogenetic relationships mostly agree between the present study and previous ones, although the inclusion of fossil taxa provides further clues to the evolution of parts of the Deirochelyinae. The inclusion of more fossil taxa and characters may help resolve the placement of some taxa, and further elucidate the evolution of these New World turtles.
（龟鳖目：水龟科）是当今最著名的龟类属之一。虽然有大量化石代表记录了其进化过程，但人们对其进化的了解并不充分。来自田纳西州东北部晚亨菲利期格雷化石遗址（GFS）的大量化石有助于阐明其进化过程。GFS的化石代表了一个新物种。描述了新分类单元，目前它是已知描述最详尽的化石水龟科物种。进行了一项系统发育分析，包括31个物种，重点是滑龟亚科，其中包括新化石物种，以及许多其他现代和化石滑龟亚科物种，这是发表的第一项包括几个化石滑龟亚科物种的系统发育分析。利用形态学证据进行的系统发育分析提供了所有现代滑龟亚科的单系类群，包括、、、、、和。严格合意树发现最近描述的化石物种是 + 类群的一部分。发现三个化石分类单元，包括一个先前归为的（）和两个归为的（和）与现代形成一个类群，与该类群的其他成员是姐妹关系。相对于其他滑龟亚科分类单元，发现与处于基部多歧分类中。先前归为的两个化石分类单元（和）与现代和形成一个并系群，可能可归为不同的属。此外，先前归为的化石分类单元（、、、和）和被发现形成一个与南北物种类群分开的类群，这可能表明有一个独特的谱系，没有现代幸存者。尽管纳入化石分类单元为滑龟亚科部分的进化提供了进一步线索，但本研究与先前研究的系统发育关系假设大多一致。纳入更多化石分类单元和特征可能有助于解决一些分类单元的位置问题，并进一步阐明这些新大陆龟的进化。
