Dewaele Leonard, Amson Eli, Lambert Olivier, Louwye Stephen
Department of Geology, Ghent University, Ghent, Belgium.
O.D. Earth and History of Life, Royal Belgian Institute of Natural Sciences, Brussels, Belgium.
PeerJ. 2017 May 16;5:e3316. doi: 10.7717/peerj.3316. eCollection 2017.
Discovered on the southern margin of the North Sea Basin, "" represents one of the best-known extinct species of Phocidae. However, little attention has been given to the species ever since its original 19th century description. Newly discovered material, including the most complete specimen of fossil Phocidae from the North Sea Basin, prompted the redescription of the species. Also, the type material of "" is lost.
"" is redescribed. Its phylogenetic position among Phocinae is assessed through phylogenetic analysis. Dinoflagellate cyst biostratigraphy is used to determine and reassess the geological age of the species. Myological descriptions of extant taxa are used to infer muscle attachments, and basic comparative anatomy of the gross morphology and biomechanics are applied to reconstruct locomotion.
Detailed redescription of "" indicates relatively little affinities with the genus , but rather asks for the establishment of a new genus: gen. nov. Hence, "" is recombined into . This reassignment is confirmed by the phylogenetic analysis, grouping the genus and other extinct phocine taxa as stem phocines. Biostratigraphy and lithostratigraphy expand the known stratigraphic range of from the late Langhian to the late Serravallian. The osteological anatomy of indicates a relatively strong development of muscles used for fore flipper propulsion and increased flexibility for the hind flipper.
The extended stratigraphic range of into the middle Miocene confirms relatively early diversification of Phocinae in the North Atlantic. Morphological features on the fore- and hindlimb of the species point toward an increased use of the fore flipper and greater flexibility of the hind flipper as compared to extant Phocinae, clearly indicating less derived locomotor strategies in this Miocene phocine species. Estimations of the overall body size indicate that is much smaller than , the smallest extant genus of Phocinae (and Phocidae), and than most extinct phocines.
在北海盆地南缘发现的“”代表了海豹科最著名的已灭绝物种之一。然而，自19世纪首次描述该物种以来，很少有人关注它。新发现的材料，包括北海盆地最完整的海豹科化石标本，促使人们对该物种进行重新描述。此外，“”的模式标本已丢失。
对“”进行重新描述。通过系统发育分析评估其在海豹亚科中的系统发育位置。利用甲藻孢囊生物地层学来确定和重新评估该物种的地质年代。使用现存分类群的肌学描述来推断肌肉附着情况，并应用大体形态和生物力学的基本比较解剖学来重建运动方式。
对“”的详细重新描述表明它与属的亲缘关系相对较小，而是需要建立一个新属：新属。因此，“”被重新组合到。这一重新分类通过系统发育分析得到证实，该分析将属和其他已灭绝的海豹亚科分类群归为海豹亚科的基部类群。生物地层学和岩石地层学将已知的地层范围从兰盖阶晚期扩展到塞拉瓦尔阶晚期。的骨骼解剖表明用于前鳍推进的肌肉发育相对较强，后鳍的灵活性增加。
的地层范围扩展到中新世中期，证实了海豹亚科在北大西洋相对较早的分化。与现存海豹亚科相比，该物种前肢和后肢的形态特征表明前鳍的使用增加，后鳍的灵活性更大，这清楚地表明这个中新世海豹亚科物种的运动策略衍生程度较低。对总体体型的估计表明，比现存最小的海豹亚科属（以及海豹科）和大多数已灭绝的海豹都要小得多。
