A new early Carboniferous crustacean from the Forest of Dean, England

摘要

Crustacean remains collected from quarries in Mitcheldean and the Great Doward in the Forest of Dean were originally thought to represent a species of Tealliocaris. Comparisons made with other Carboniferous crustaceans suggest that this material belongs to a new genus and species of eumalacostracan crustacean. The erection of this new genus and species is supported by morphometric and cladistic analyses. The new crustacean, Schramocaris gilljonesorum gen. et sp. nov., appears to exhibit more similarities to Tealliocaris and the Scottish and northern English crustacean Pseudogalathea. There are, however, some significant differences in the shape of the carapace, and the ornamentation of the carapace and pleon. The broad, squat telson is more akin to that of Pseudogalathea, but the length of the pleon and the lack of elongated sharp posterolateral angles to the carapace are more like those of Tealliocaris. The apparent lack of a scaphocerite and the lack of an enlarged third pleomere are more suggestive of affinities with Pseudogalathea, principal coordinate analysis on 12 landmarks of the carapace indicate that this new crustacean is distinct from both Tealliocaris and Pseudogalathea. A cladistic comparison with other Devonian and Carboniferous crustaceans from around the world also suggests that it is distinct, but morphologically similar to a grouping that includes Chaocaris, Tylocaris, Fujianocaris, Pseudogalathea and Tealliocaris.