Cranial and postcranial remains of a new species of Prochelidella (Testudines: Pleurodira: Chelidae) from ‘La Buitrera’ (Cenomanian of Patagonia, Argentina), with comments on the monophyly of this extinct chelid genus from southern Gondwana

The genus Prochelidella is the oldest known panchelid taxon. It is widely distributed in several Cretaceous basins throughout Patagonia, Argentina. It was previously known from three named species. A fourth species presented herein, Prochelidella buitreraensis sp. nov., preserves both cranial and postcranial material from the Candeleros Formation (La Buitrera Area) of Río Negro Province, Argentina. Features observed in the nuchal bone (i.e. wide, trapezoidal cervical vertebrae, shallow nuchal notch) allow us to assign this specimen to the genus Prochelidella. Several specific traits (i.e. a large open retropterygoideum foramen, and a strongly developed muscle attachment site on the basisphenoid) suggest that the form from the Candeleros Formation is a new species of the genus Prochelidella. A phylogenetic analysis that includes the three best-preserved species of Prochelidella recovers this taxon as monophyletic. The Cenomanian age of this new taxon allows us to compare the panchelid turtles from the Patagonian (Neuquen) and Australian (Surat) basins. http://zoobank.org/urn:lsid:zoobank.org:pub:E9D194C7-126D-46B6-BF75-BD1A51A74971原侧颈龟属（Prochelidella）是目前已知最古老的泛侧颈龟类（Pan-Chelidae）类群。该属广泛分布于阿根廷巴塔哥尼亚境内的多处白垩纪盆地，此前仅报道过3个已命名物种。本文记述的第4个新种为Prochelidella buitreraensis sp. nov.（布伊特雷拉原侧颈龟，新种），其化石产自阿根廷内格罗河省拉布伊特雷拉地区的坎德列罗斯组，同时保存有颅骨与颅后骨骼材料。通过颈板（nuchal bone）所呈现的特征（即宽大的梯形颈椎、浅宽的颈缺刻），可将该标本归入原侧颈龟属。此外，多项特异性状（即大型开放式后翼骨孔、基蝶骨上发育极强的肌肉附着位点）表明，坎德列罗斯组产出的该类群为原侧颈龟属的一新物种。包含原侧颈龟属3个保存最完好物种的系统发育分析结果显示，该属为单系群。该新种的森诺曼期（Cenomanian）地质年代，为对比巴塔哥尼亚（内乌肯）与澳大利亚（苏拉特）盆地的泛侧颈龟类化石提供了研究依据。http://zoobank.org/urn:lsid:zoobank.org:pub:E9D194C7-126D-46B6-BF75-BD1A51A74971