Saturday, February 7, 2009

' A cross between a cow, whale, shark, alligator and sea lion. '

I talked about how a phylogeny is a testable hypothesis of the evolution of a group, or clade. In the case of marine mammals such as whales the hypothesis is that they evolved from non-aquatic ancestors. Well a paper in PLoS One this week, with the catchy title: New Protocetid Whale from the Middle Eocene of Pakistan: Birth on Land, Precocial Development, and Sexual Dimorphism describes the discovery of a rare fossil of a ancient whale with a fetus still inside that reveals that its species, ancestors to modern whales, gave birth on land 47.5 million years ago.

The discovery, along with prior fossil finds, suggests the first whale ancestors were full-time land dwellers that might have been related to the early relatives of hoofed animals, such as sheep and cattle. It lived at the land-sea interface and often moved back and forth between the two environments in what is Pakistan today and looked like an improbable cross between a cow, whale, shark, alligator and sea lion.

No comments: