THE FIRST PALEOZOIC RECORD OF A POSSIBLE TRUE CRAB

The Paleozoic fossil record of decapod crustaceans is one of 'ghost lineages'—lineages that appear as crown clade taxa in the middle Paleozoic without an apparent ancestral lineage, reappearing in late Paleozoic to Mesozoic strata after a temporal gap of tens of millions of years. The eubrachyurans—advanced 'true crabs'—are known from rocks as old as Early Cretaceous from the Americas. Based on this, it was hypothesized that early eubrachyurans, now global in distribution, dispersed from the Americas during the Cretaceous. Recognized here is a eubrachyuran-like form from Permian-aged rocks of the Sosio Valley, Italy, possibly extending the geologic range of Eubrachyura by more than 100 million years. Based on this, it is putatively hypothesized that eubrachyuran-like decapods evolved in the European Paleotethys and dispersed to the Americas as the Tethys Ocean basin opened and eventually connected with the spreading Atlantic Ocean during the Late Jurassic. As such, it appears that the fossil record of eubrachyuran-like forms, like that of astacid lobsters and stenopodid shrimps, is one characterized by the early appearance of a crown clade taxon followed by a reappearance and radiation after a vast gap in the fossil record.