Editing Baikal seal (section)

===Evolution===
The skull structure of the Baikal seal suggests it is closely related to the [[Caspian seal]]. In addition, the morphological structures in both species suggest they are descended from Arctic [[ringed seal]]s.<ref>{{cite journal|last1=Endo|first1=H.|last2=Sakata|first2=S.|last3=Arai|first3=T.|last4=Miyazaki|first4=N.|title=The Muscles of Mastication in the Caspian Seal (''Phoca caspica'')|journal= Anatomia, Histologia, Embryologia|date=April 2001|volume= 31|issue= 5|pages=262–265|doi=10.1046/j.1439-0264.2002.00372.x|pmid=12484416|s2cid=30684638}}</ref> In prehistory, they may have swum up rivers and streams, or there is the possibility that Lake Baikal was linked to the ocean at some point through a large body of water, such as the [[Paratethys Sea]], [[West Siberian Glacial Lake]] or [[West Siberian Plain]], formed in a previous [[ice age]]. The seals are estimated to have inhabited Lake Baikal for some two million years.<ref>{{cite journal |last1=Palo |first1=Jukka U. |last2=Väinölä |first2=Risto |title=The enigma of the landlocked Baikal and Caspian seals addressed through phylogeny of phocine mitochondrial sequences|journal=Biological Journal of the Linnean Society |date=2006 |volume=88 |issue=1 |pages=61–72 |doi=10.1111/j.1095-8312.2006.00607.x|doi-access=free}}</ref>