from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Plural form of phocine.
Sorry, no etymologies found.
The degree of genetic divergence found amongst living phocines suggests – based on molecular clock inferences (which are always controversial and problematic) – that Baikal seals and other phocines diverged around 4 million years ago, during the late Pliocene.
According to the former model, the ancestors of Baikal seals must have diverged from other phocines some time during the Miocene, and according to the latter model, Baikal seals evolved from a more northerly ancestor during the Pleistocene.
Diverse phocine seals – some apparently resembling the extant Pusa** seals – are known to have inhabited Paratethys during the Miocene (Paratethys was a brackish inland sea that covered much of south-east Europe and south-west Asia during the Miocene) and, according to the Paratethyan hypothesis, it is phocines from this region that managed to invade the Caspian Sea, later getting as far east as Lake Baikal.
The competing hypothesis posits that neither Baikal seals nor Ringed seals have descended from Paratethyan phocines that migrated south to north, but that all the pagopholic Pusa seals are of Arctic ancestry, and that seals got into Lake Baikal from the north.
Secondly, the Paratethyan hypothesis requires that the phocines ancestral to Baikal seals and Ringed seals were animals of enclosed basins, relatively low latitudes and warm temperatures, and this is problematic given that Baikal and Ringed seals are thermophobic and pagophilic, with thickly-furred pups kept in snow dens.
Furthermore, excepting the unusual inland populations, all phocines are oceanic, and not denizens of enclosed basins.