Article: The effaced styginid trilobite Thomastus from the Silurian of Victoria, Australia
Thomastus is a blind effaced styginid trilobite that occurs in strata of Wenlock age in Victoria, Australia. The genus is most closely related to Bumastella and Illaenoides, with which it shares characters such as a highly convex cephalon, the absence of the omphalus and the anterolateral internal pit, a weakly forwardly converging facial suture, a transverse furrow in front of the articulating flange on the posterior fixigenal margin, and a pygidium with a deep holcos. Of the four species previously assigned to Thomastus, T. collusor and T. vicarius are considered to be synonyms of the type species T. thomastus. One new species, T. aops, is described.