Desmatophoca

Extinct genus of carnivores

Desmatophoca is an extinct genus of early pinniped that lived during the Miocene, and is named from the Greek "phoca", meaning seal. A taxon of the family Desmatophocidae, it shares some morphological similarities with modern true seals. Two species are recognized: Desmatophoca oregonensis and Desmatophoca brachycephala''''. Little information exists regarding Desmatophoca, due to the small number of fossil samples obtained and identified. Unlike modern pinnipeds, Desmatophoca did not survive into the Holocene. Because of this, it is likely they had a stronger bite force than any seal alive today, making them formidable hunters of their time. Through comparisons with extant pinnipeds, Desmatophoca were determined to be either grip and tear feeders (biting prey and shaking it into smaller portions to consume) or pierce feeders (biting prey and using slight suction to draw it fully into the mouth). The thickness of the mandible is especially important, as it provides both high bite force and increased surface area for muscular attachment between the jaws, which allows for stronger mastication. The extremely thick mandibles also serve as a diagnostic characteristic of this genus. The two genera both have large preoccipital processes, similar cranium shapes, and short rostrums. All members of Phocoidea, including Desmatophoca, share large orbits, bulbous cheektooth crowns, and expanded contact between the squamosal and the jugal. The genus Desmatophoca consists of two known species: D. oregonensis (named for Oregon, the state it was discovered in) and D. brachycephala.

The first Desmatophoca discovered was D. oregonensis, by Professor Thomas Condon in 1906, a year before his death. It was found in the middle Miocene layer of the Astoria Formation in Newport, Oregon. It was described and classified based solely off of a skull and partial jaw, and at the time, it helped shed light on the relationship between modern pinnipeds and other terrestrial carnivores. The use of D. oregonensis helped solidify the theory that modern seals evolved from terrestrial carnivores, and not the other way around. By comparing morphologies of D. oregonensis with extant terrestrial carnivores, it was determined that Desmatophoca shares a most recent common ancestor with bears and mustelids. This fossil sample also helped throw out the theory that seals share their most recent common ancestor with dogs and other canines, which was a popular thought at the time. The second species of Desmatophoca, D. brachycephala was discovered in 1987 by Barnes, in the late Miocene layer of the Astoria Formation that jetted into southwest Washington state.

Because fossil Desmatophoca have only appeared from the same site, the Astoria Foundation in the Pacific Northwest, there is a bias in the data that has been collected. Additionally, few fossil Desmatophoca have been found and successfully categorized, meaning there is still much to be discovered about this species. In fact, of 388 instances of fossil pinniped species being identified successfully, only 5% of these samples belong to Desmatophocidae, comprising 11 species.