Lepidocyclus

Classification
Phylum: Brachiopoda
Class: Rhynchonellata
Order: Rhynchonellida
Family: Rhynchotrematidae
Genus: Lepidocyclus Wang, 1949
Cincinnatian Species: Lepidocyclus perlamellosum

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Type species: Lepidocyclus laddi Wang, 1949 (Jin & Zhan, 2001)
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Geologic Range
Late Ordovician

Common Paleoecology
Lepidocyclus is an extinct genus of stationary, epifaunal suspension feeders

Identification in Hand Sample:

Medium sized with strongly biconvex shape
Subtriangular
Rounded hinge line
Well defined ridges run from beaks
Dorsal fold and ventral sulcus
Very small, circular pedicle foramen
Concentric, closely spaced growth lines
Ornamentation has a distinct ‘zig-zag’ shape

Geographic Occurrences

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Swisher (2009):

Shell medium to large in size, variable length to width ratio, strong biconvexity. Well-developed costae and growth lamellae. Pedicle umbo and beak suberect to incurved. Delthyrium closed by medially conjunct deltidial plates, dental plates reduced. Septalium reduced, septialial plates moderately developed. Hinge plates thick, well developed. Cardinal process thin, septiform, with crura radulifer.

Treatise on Invertebrate Paleontology, Part H, Vol. 4 (2002):

Medium to large with elongate subcircular to subtriangular outline and strongly biconvex profile. Beak erect to incurved; deltidial plates conjunct to disjunct. Fold and sulcus strong, from umbones; anterior commissure uniplicate; tongue trapezoid, tapering dorsally, dentate. Costae strong, angular to subangular, simple, from beaks, with lamellose growth lines. Dental plates reduced or fused to valve walls; ventral muscle field deeply impressed. Dorsal median septum extending to valve mid-length; septalium small; cardinal process thin, septiform; hinge plates thick; crural bases horizontal; crura rodlike proximally, becoming laterally flattened distally, ventrolaterally curved.

Fossils of Ohio (1996):

A small to large rhynchonellid brachiopod. Its profile ranges from moderately biconvex, especially when small, to strongly biconvex when large. The outline ranges from subtriangular to subcircular. The hinge line is rounded. Coarse ribs radiate from the beaks across both valves. The ribs do not branch. A distinct fold is present in the brachial valve, and a corresponding sulcus in the pedicle valve. The pedicle opening is small and rounded. In large specimens the pedicle umbo may be incurved and obscure the pedicle opening. The intersection of numerous, closely spaced, concentric growth lines with the coarse, radiating ribs results in a highly distinctive ornament. Lepidocyclus has been recorded from the Arnheim to the Drakes Formations

Amsden (1983):

The deltidial plates are complete, creating a relatively long pedicle tunnel. In at least one species, L. cooperi the posterior shell wall thickens to further restrict the pedicle opening, perhaps completely closing it with some gerontic individuals.

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L. perlamellosum