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Background   Prophoca  and  Leptophoca  represent the oldest known genera of phocine seals, dating from the latest early to middle Miocene. Originally,  Prophoca rousseaui  and  Prophoca proxima  were described based on fragmentary remains from the Miocene of Belgium. However, several researchers contested the union of  Prophoca rousseaui  and  Prophoca proxima  into one genus, without providing evidence. The stratigraphic context of  Prophoca  remained poorly constrained due to the lack of precise data associated with the original specimens collected in the area of Antwerp (north of Belgium).    Methods   Prophoca  and  Leptophoca  are redescribed and their phylogenetic position among Phocidae is reassessed using PAUP. Dinoflagellate biostratigraphy has been carried out on sediment samples associated with specimens from  Prophoca  and  Leptophoca  to elucidate their approximate ages.    Results  Whereas the species  Prophoca rousseaui  is redescribed,  Prophoca proxima  is considered synonymous to  Leptophoca lenis , with the proposal of a new combination  Leptophoca proxima  ( Van Beneden, 1877 ). Sediment samples from specimens of both taxa have been dated to the late Langhian–early Serravallian (middle Miocene). Following a reinvestigation of  Leptophoca amphiatlantica , characters from the original diagnosis are questioned and the specimens of  Leptophoca amphiatlantica  are considered  Leptophoca  cf.  L. proxima . In a phylogenetic analysis,  Prophoca rousseaui  and  Leptophoca proxima  constitute early branching stem-phocines.    Discussion   Leptophoca proxima  from the North Sea Basin is younger than the oldest known find of  Leptophoca proxima  from North America, which does not contradict the hypothesis that Phocinae originated along the east coast of North America during the late early Miocene, followed by dispersal to Europe shortly after. Morphological features of the appendicular skeleton indicate that  Prophoca rousseaui  and  Leptophoca proxima  have archaic locomotory modes, retaining a more prominent use of the fore flipper for aquatic propulsion than extant Phocidae.

peerj

On<i>Prophoca</i>and<i>Leptophoca</i>(Pinnipedia, Phocidae) from the Miocene of the North Atlantic realm: redescription, phylogenetic affinities and paleobiogeographic implications

OnProphocaandLeptophoca(Pinnipedia, Phocidae) from the Miocene of the North Atlantic realm: redescription, phylogenetic affinities and paleobiogeographic implications