Board Thread:Fossil Fuels/@comment-50.81.142.215-20141213090435/@comment-3213993-20150312060532

Two homeobox genes, Hoxd12 and Hoxd13, control the pattern of digits. Expansion of polyalanine tracts (I don't know what this means, but I do know that poly means multiple and alanine is an amino acid) [http://mbe.oxfordjournals.org/content/26/3/613.full have been implicated in flipper development in whales and dolphins. ] Theoretically, if the Hox sequences of crocodilians and monitor lizards are similar to those of mammals, the same mutations could cause monitor lizards and crocodilians to develop flippers.

But we need to find genes for other adaptions as well, such as salinity tolerance and other requirements for an aquatic lifestyle.