Allodesmus. Computer illustration and photo-reconstruction of the extinct seal Allodesmus under water. Allodesmus is an extinct genus of pinniped from the Miocene and related to the genus Desmatophoca. It measured about 2.4 m long and weighed 360 kg. Allodesmus is quite distinct from the sea lion and unquestionable represents a more generalized type. Allodesmus is a specialized otariid pinniped that diverged from the main line of sea lion evolution.