Middle Ordovician – Late Ordovician
Carneyella is an extinct genus of stationary epifaunal suspension feeders
Identification in Hand Sample:
- Relatively long and curved ambulacra, usually numbering 5
- Distinguished by single series of ambulacral coverplates on either side of each ambulacra
- Theca subcircular, typically elevated, saclike, minutely pitted and commonly ornamented with ridges
- Anal pyramid of about 7 (or more) triangular pieces
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- Like Isorophus and Curvitriordo, Carneyella has relatively long and curved ambulacra, one of which is curved clockwise. Carneyella is distinguished by the presence of a single series of ambulacral coverplates on either side of each ambulacra, rather than two as in Isorophus, or three as in Curvitriordo.
- DISCUSSION: Interestingly, all specimens of Carneyella regardless of species show identical plating of the ambulacral cover plate system. Three greatly enlarged primary oral plates form the central portion of the peristomial cover and all specimens lack cover plates on the short ambulacra. All of the ambulacra have a simple biseries of cover plates covering the ambulacral tunnel, but unlike has been noted in other echinoderms that they cover plates, do not follow an insertion pattern consistent with Loven’s Law. Plating that follows Loven’s Law will have identical plating on the A C and E ambulacra. This results in a symmetrical arrangement of plating around the peristome as shown (Hotchkiss, 1998; Sumrall and Wray, 2007). For Carneyella, the opposite pattern is expressed. The A, B, and D ambulacra all begin with plates on the left side if viewed proximally to distally (Fig. 4). The C and E ambulacra have the first place on the right.
- This reversed plating pattern is unrelated to the right-left symmetry of the body openings and therefore does not represent reversed larval development as has been shown for aberrant individual edrioasteroids (Smith & Arbizu, 1987; Sumrall, 2001). Instead, it may simply reflect a developmental constraint in plate insertion as shown for glptocystitoid rhombiferans (Sumrall, 2008). In this example. Loven’s Law resulted from the point of insertion of oral plated early in development. This resulted in the left brachioles of the shared ambulacra being place in line with the brachioles of the B and D ambulacra. This was manifest at maturity as all ambulacra bearing the first brachiole facet on the left except for B and D which had the first two on the left. In Carneyella we see a similar constraint simply bearing the opposite result. The first cover plate on the right side of the C ambulacrum may be related to the enlargement of the first right cover plate and its association with the hydropore opening (Fig. 4). For the E ambulacrum it seems related to the anterior shift of the left LBP.
Fossils of Ohio (1996):
- Known from Middle and Upper Ordovician strata in N.A.
Treatise on Invertebrate Paleontology, Part U Echinodermata 3, Vol. 1 (1966):
- Theca subcircular, typically elevated, saclike, attached by broad basal part, but also forming depressed epizoic discs usually on brachiopods, diameter reaching 30mm. but usually 15 to 20 mm.; thecal plates more or less imbricating, differentiated into interambulacral fields and marginal zone; ambulacra normally 5, varying in length, curved, ambulacrum C solar, others contrasolar, some (as in figured species) with small additional cover plates along mid-line of ambulacra; surface of plates minutely pitted and commonly ornamented with ridges and conspicuous notes (spiniferous tubercles); anal pyramid of about 7 (or more) triangular pieces (4, 26).