A new family of Triassic lobsters (Decapoda : Astacidea) from British Columbia and its phylogenetic context

Chimaerastacus pacifluvialis, new genus and species, is established on the basis of fossils from the Middle Triassic Liard Formation of northeastern British Columbia. It has well-defined cervical, postcervical, and branchiocardiac grooves; three longitudinal ridges on the cephalic region; and true chelae on the first through third pereiopods. The morphological features of the carapace are a combination of traits used to define both the erymids and the glypheids. A cladistic analysis of 31 decapod genera defines the Astacidea as a monophyletic group, supports the inclusion of the Glypheoidea within the infraorder Astacidea, illustrates the relationships of the Glypheoidea with other astacid groups, and suggests erection of a new family, the Chimaerastacidae, for our new genus and species of decapod. Specimens of C. pacifluvialis are preserved in a sandy bioclastic floatstone that was deposited near the Peace River Embayment in the Middle Triassic. The host lithology suggests that the decapods inhabited a transitional environment between low relief biostromes and the shoreface. This environment provided a unique set of conditions that allowed exceptional preservation of the decapod material.