ammonites
Xenosteges umbonatus Cooper and Grant 1975 (lamp shell)

Strophomenata - Productida - Aulostegidae

Full reference: G. A. Cooper and R. E. Grant. 1975. Permian Brachiopods of West Texas, III. Smithsonian Contributions to Paleobiology 19:795-1921

Belongs to Xenosteges according to G. A. Cooper and R. E. Grant 1975

Sister taxa: Xenosteges adherens, Xenosteges anomalus, Xenosteges magnus, Xenosteges minusculus, Xenosteges quadratus, Xenosteges trivialis

Type specimen: USNM 149217d, a shell (Articulated shell)

Ecology: stationary low-level epifaunal suspension feeder

Average measurements (in mm): shell 8.45 x 7.79