Late Ordovician – Early Carboniferous
Craniops is an extinct genus of stationary epifaunal suspension feeders
Identification in Hand Sample:
- Shell is biconvex, and the outline is elongated and oval
- Umbones posterior to center
- Pedicle valve more convex than brachial valve
- Both pedical and brachial valves display muscle platforms, but brachial valve has a median depression that is deeper
Map point data provided by iDigBio.
Treatise on Invertebrate Paleontology, Part H (2) (2000):
- Shell subequally biconvex, elongate oval, lamellose; both valves with growth holoperipheral, umbones posterior to center; visceral areas of both valves with limbus; attached apically by cementation.
- Shell biconvex; outline oval, apices eccentric along long axis of valves. Surface ornamented by as many as eight growth varices eccentric apices. Pedicle valve more convex than brachial valve, internal pedicle valve has a muscle platform composed of two prominent calluses with a low depression between them , united anteriorly . Brachial valve has muscle platform but median depression is deeper, extends anteriorly so that platform may be bilobate. Rowell, in (Moore 1965 p H273) indicates that Craniops shows a scar of attachment on pedicle valve
- Shells small, patelliform, equivalve, equiconvex, inarticulate, unattached. Outline oval or subelliptical; apex subcentral, excentric or marginal, sometimes terminal and produced. Surface marked by strong, concentric, often lamellose lines of growth, which are crowded on the posterior, and distant on the anterior portions of the valves; these are sometimes crossed by faint interrupted radiating lines. In the interior, the surfaces of contact make a broad smooth, flat, or slightly convex border, somewhat broader than in front than behind. The muscular and visceral area occupies a sharply defined and very limited space in the apical portion of each valve. In both valves it is of essentially the same size and subtriangular in otuline, the apex of the triangle pointing forward and usually surrounded by a conspicuous callosity. The ventral (?) valve bears two well defined central adductors occupying the same relative position in the Crania; these impressions are usually simple, but appear to be sometimes complicated by association with ill-defined scars of the anterior muscles. The posterior adductors or divaricators are situated at the basal angles of the muscular triangle, and are distant from the posterior margin. The linear parietal scars are very strong, the posterior being more or less distinctly lobate, the anterior generally straight or rounding about the central adductors. In the opposite dorsal (?) valve the scars have essentially the same arrangement; the anterior adductors, however, are separated by elongate median scars (anteriors) which traverse the elevated callosity surrounding the anterior margin of the area. The posterior scars are often more widely divergent than in the other valve. Shell-substance calcareous and impunctate.