Spondylus suttkusi H. E. Vokes, 1990
VOKES, H. E. 1990. A New Species of Spondylus (Mollusca: Bivalvia) from the Eocene of Alabama. Tulane Studies in Geology and Paleontology, 23 (4): 127-129, figs. 1-3. [p. 127, text-figs. 1-3]
1990 Spondylus suttkusi H. E. Vokes, 1990
H. E. Vokes, 1990, figures 1-3.
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«Description: Shell of moderate size for the genus, slightly elongate-oval, with a small attachment area resulting in a regular outline Surface of lower (right) valve is marked by regularly spaced lamellar foliations and lacks any radial ornamentation. The upper (left) valve is relatively low, arched; initially with about 15 primary radial ribs, which bear small narrow nodose projections, and usually with f'our secondary ribs between each pair of primary radials. With growth the projections on the primary ribs become moderately broad spines the secondary ribs increase in strength and develop narrow needle-like ribs. In addition, narrow low tertiary radial ribs with sub-microscopic nodose projections appear. In the adult stage the primary and secondary ribs become almost equally strongly spinose, the tertiary ones develop relatively narrower projecting spines and three quaternary ribs are added in the interspaces, with the middle of the three tending to have smaller, relatively narrow spines, the marginal ones somewhat nodose and weak.
Holotype: USNM 450391. Type locality: TU 306, Gosport Sand; Little Stave Creek, about 4 miles north of Jackson, Clarke County, Alabama. Measurements of holotype: right (lower valve), height 65.2 mm, length 56.5 mm; left (upper valve), height 59.3 mm, length 56.5 mm; diameter of paired valves 29.6 mm. Discussion: The two valves of this specimen display strikingly the different types of surface ornamentation developed in response to the environment. The lower valve is marked by strong concentric laminae, indicating its position on a relatively soft sediment bottom, and the upper valve is ornamented by numerous short, sharp spines, indicating a habitat of moderately strong current-flow. If the two valves had been taken separately they would have probably been assigned to two different species.
As noted above the only specimens previously known from the Eocene beds of the Atlantic and Gulf Coastal Plain have not been named. The named species are from the younger Oligocene beds: Spondylus dumosus (Morton, 1834), from the Red Bluff Formation, Alabama and Mississippi; S. filiaris Dall, 1916, from the Mint Springs Formation, Mississippi, and the Flint River Formation, Georgia; and S. granulocostatus Dockery, 1982, Red Bluff Formatiom, Alabama. All three have been figured by Dockery (1982, pl. 14, figs. 1-9 [dumosus]; pl. 15, figs. 1-3, 6, 7 [filiaris]; and pl. 15, figs. 4, 5 [granulocostatus]) and it may be seen that S. dumosus differs from S. suttkusi in having fewer, and relatively stronger primany and secondary ribs, ornamented by narrower, more elongate spines. Spondylus filiaris has almost no spinose ornamentation and S. granulocostatus has six of the radial ribs with heavy upturned spines, and between these numerous nodulose secondary radials.» HAROLD ERNEST VOKES, 1990
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