Unique Short-Faced Miocene Seal Discovered in Grytsiv (Ukraine)

Abstract

Numerous Miocene terrestrial mammal fossils have been discovered at the Grytsiv locality of Ukraine, but this is the first record of a fossil marine mammal at this site. Morphological analysis of the rostral portion of this middle-late Miocene (12.3–11.8 Ma) partial skull suggests that it belongs to the subfamily Phocinae. The small size and cranial morphology of this partial skull is compared with recent and fossil representatives of the extant subfamily Phocinae and the extinct subfamily Devinophocinae. Extinct and modern representatives of the extant subfamilies Cystophorinae and Monachinae were not incorporated in this study due to their extremely large size in comparison to this new find. This newly described skull belonged to a small-sized seal (likely similar in size to the modern sea otter based on the width of the rostrum) with an extremely short rostrum and several other diagnostic characters that differ from all other fossil and extant phocines. Due to the lack of preservation and fragility of fossil seal skulls, less than 20 have been described so far. This new skull is yet another example of an ancestral seal, supporting the suggestion that modern seals have become larger over their evolutionary history. Overall, any cranial information on fossil true seals is extremely important since it allows resolving contentious phylogenetic relationships between extinct and extant representatives of this group.