Phylum: Brachiopoda
Class: Rhynchonellata
Order: Orthida
Family: Plaesiomyidae
Genus: Retrorsirostra Schuchert & Cooper, 1931
Cincinnatian Species: Retrosirostra carleyi

Geologic Range
Late Ordovician (Ashgill)

Common Paleoecology
Retrorsirostra is an extinct genus of stationary epifaunal suspension feeders

Identification in Hand Sample:

  • Epipunctae large, usually about eight per rib
  • Subparallel dental plates
  • Nearly straight commissure
  • Coarse and densely spaced ribs

Geographic Occurrences

Published Description

Jin, Zhan, Copper, and Caldwell (2007) :

  • Within the plaesiomyids, the epipunctae in Retrorsirostra and Plaesiomys are similarly large, usually with fewer than eight per rib along a growth line. In comparison, the epipunctae of Dinorthis occidentalis are more numerous and more densely spaced, reaching over 20 per rib along a growth line.

Treatise on Invertebrate Paleontology, Part H, Vol. 3 (2000):

  • Similar to Plaesiomys but rectimarginate, coarsely costellate, and filate; procline ventral interarea long, planar, orthocline dorsal interarea short, curved; dental plates projecting subparallel, ventral muscle scar impressed on low callus with median ridge

R. carleyi