ammonites
Altiplecus trapezoidalis Cooper and Grant 1976 (lamp shell)

Rhynchonellata - Spiriferinida - Reticulariinidae

Full reference: G. A. Cooper and R. E. Grant. 1976. Permian Brachiopods of west Texas, V. Smithsonian Contributions to Paleobiology 24:2609-3159

Belongs to Altiplecus according to G. A. Cooper and R. E. Grant 1976

Sister taxa: Altiplecus argutus, Altiplecus cooperi, Altiplecus deltosus, Altiplecus extensus, Altiplecus glebosus, Altiplecus mongolica, Altiplecus periosus, Altiplecus zhejiangensis

Type specimen: USNM 153059e, a shell (Articulated shell)

Ecology: stationary low-level epifaunal suspension feeder

Average measurements (in mm): shell 14.3 x 21.2, valve 15.5 x 35.8