Alligator sinensis and Alligator mississippiensis are put under the Alligator family and Alligator genus as two different species and have been thought that they are closely related in taxonomy. The results of our DNA-DNA hybridization experiments showed that A. sinensis is a relatively young species originated in Asia,whereas A. mississippiensis is the older.It seems that the alligator and crocodilian could evolve from each other.The evolutionary rate of the crocodilian is slower than those of birds and higher vertebrates.The phylogeny of four crocodilians have been obtained and the hypothesis that the ancestor of Crocodylus porosus is a transitional form between A.mississippiensis and A.sinensis is proposed.
