Articles | Volume 18, issue 1
Research article
27 Jan 2015
Research article |  | 27 Jan 2015

New specimen of Cacops woehri indicates differences in the ontogenetic trajectories among cacopine dissorophids

N. B. Fröbisch, A. Brar, and R. R. Reisz

Abstract. The Lower Permian Dolese locality has produced numerous exquisitely preserved tetrapod fossils representing members of a lower Permian upland fauna. Therein, at least nine taxa of the clade Dissorophoidea, ranging in size from the large predaceous trematopid Acheloma to the miniaturized amphibamid Doleserpeton, highlight the great taxic and ecological diversity of this anamniote clade. Here we describe a large specimen of the dissorophid Cacops woehri, which was previously only known from the juvenile or subadult holotype skull. Another member of the genus Cacops present at the Dolese locality, Cacops morrisi, is also represented by specimens spanning juvenile, subadult, and adult stages, allowing for a comparison of morphological changes taking place in the late phases of the ontogenetic trajectory of cacopine dissorophids. The new find shows that, in contrast to C. morrisi and C. aspidephorus, C. woehri only undergoes relatively subtle changes in skull morphology in late ontogeny and retains the overall more gracile morphology into adult stages. This includes retention of the rather shallow skull shape as well as a pattern of sculpturing consisting of elongate ridges and grooves and a large occipital flange. This suggests somewhat different functional demands in C. woehri than in other known species of Cacops, possibly associated with a different ecology paralleling the great taxic diversity of dissorophoids at the Dolese locality.

Short summary
Here we describe a large specimen of the Paleozoic dissorophid amphibian Cacops woehri from the Fort Sill locality in Oklahoma, which was previously only known from a partial juvenile skull. The new data show that, in contrast to the closely related species C. morrisi, C. woehri underwent only subtle changes in skull morphology in late ontogeny, which indicates different functional demands possibly associated with a different ecology.