DiagnosisThe Astacidea includes the lobster, Homarus. The cephalothorax has a well developed rostrum and is usually sub-cylindrical. The pleon and associated pleura are well developed and the uropods preserve diaresis. Finally the chelae on the 1st pereiopods are very large.
OriginLike the Dendrobranchiata, this group's fossil record is thought to extend back to the Permo-Triassic boundary (250 million years ago)