From Oligochiton, we transfer onto Oligorhynchia. The Oligorhynchiidae are a household of very small brachiopods recognized from the Center and Late Ordovician. They had been among the many earliest representatives of the Rhynchonellida, a significant group of brachiopods that survives to the current day. Rhynchonellidan shells are normally characterised by a robust beak related in life with a well-developed pedicel. In oligorhynchiids, this beak is suberect and the shell as an entire is an elongate subtriangular form. The valves of the shell are folded into coarse plicae (ridges). No less than in the direction of the bottom of the shells, the key folds are in what is named an inverted association, with a ridge within the dorsal valve matched by a valley within the ventral valve (Schmidt & McLaren 1965). Different structural options defining the group embrace small plates projecting into the pedicel opening, distinct vertical dental plates and divided hinge plates within the valve articulation, and the standard absence of a median septum or cardinal course of contained in the shell (Savage 1996).
The oligorhynchiids first arose within the east of what was then the continent of Laurentia (comparable to fashionable North America). They subsequently unfold throughout the Iapetus Ocean to the continents of Baltica and Kazakhstan (Jin 1996). The top of the Ordovician noticed their alternative by different rhynchonellid households. Nonetheless, their genetic lineage would proceed for a while but as they’ve been recognized as ancestors of later households: the Trigonirhynchiidae and Camarotoechiidae (Jin 1989). The temporary oligorhynchiid spark would blossom into later rhynchonellid success.
Jin, J. 1989. Late Ordovician–Early Silurian rhynchonellid brachiopods from Anticosti Island, Quebec. Biostratigraphie du Paléozoïque 10: 1–127, 130 pls.
Jin, J. 1996. Ordovician (Llanvirn–Ashgill) rhynchonellid brachiopod biogeography. In: Copper, P., & J. Jin (eds) Brachiopods pp. 123–132. CRC Press.
Savage, N. M. 1996. Classification of Paleozoic rhynchonellid brachiopods. In: P. Copper, & J. Jin (eds) Brachiopods pp. 249–260. CRC Press.