Belongs within: Orthoidea.
The Ordovician simple life
Published 1 December 2025
Among the characteristic brachiopods of the Ordovician period are the Hesperorthinae, an example of which is shown in the photo above. Members of this group were widespread in what is now North America and Eurasia, becoming extinct in the Early Devonian. They were characterised by more or less strongly costate shells with a straight hinge. The ventral (pedicle) valve was much deeper than the dorsal (branchial) valve, with the latter sometimes completely flat. Here is the same individual as above in lateral view (dorsal valve downwards):
In life, the deep pedicle valve would have supported the animal in soft sediment, holding the shell opening above the surface so that the brachiopod could filter food particles from the surrounding water. Not a very exciting life, perhaps, but certainly a successful one: living brachiopods still live in exactly the same way.
Systematics of Hesperorthinae
HesperorthinaeWW65
|--Barbarorthis Öpik 1934WW65
| `--*B. foraminifera Öpik 1934WH00
|--Lordorthis Ross 1959WW65
| `--*L. variabilis Ross 1959WW65
|--Schizonema Foerste 1909 [=Schizoramma Foerste 1912]WH00
| `--*S. fissistrata (Foerste 1909) [=Hebertella (*Schizonema) fissistriata, *Schizoramma fissistriata]WH00
|--Hesperorthis Schuchert & Cooper 1931WW65
| |--*H. tricenaria (Conrad 1843) [=Orthis tricenaria]WW65
| `--H. australisWW65
`--Boreadorthis Öpik 1934WW65
|--*B. crassa Öpik 1934WW65
`--B. reculaWW65
|--B. r. reculaWW65
`--B. r. aequivalvataWW65
*Type species of generic name indicated
References
[WH00] Williams, A., & D. A. T. Harper. 2000. Orthida. In: Kaesler, R. L. (ed.) Treatise on Invertebrate Paleontology pt H. Brachiopoda, Revised vol. 3. Linguliformea, Craniiformea, and Rhynchonelliformea (part) pp. 714–782. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas: Lawrence (Kansas).
[WW65] Williams, A., & A. D. Wright. 1965. Orthida. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt H. Brachiopoda vol. 1 pp. H299–H359. The Geological Society of America, Inc.: Boulder (Colorado), and The University of Kansas Press: Lawrence (Kansas).