Caribachlamys sentis (Reeve, 1853)
REEVE, L. A. 1852-1853. Monograph of the genus Pecten. In, Conchologia Iconica, or Illustrations of the Shells of Molluscous Animals , vol. 8. London, 1855. 35 pls. Unpaginated. [sp. 125, pl. 29, fig. 125]
1853 Pecten sentis Reeve, 1853
L. A. Reeve, 1852-1853, plate 29.
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«PECTEN SENTIS. Pect. testa subtrigono - ovata, altiore quam longa, aequivalvi, subaequilaterali, profuse tennui-lirata, liris alternatim majoribus, dense aculealo-squamatis, intense miniata, maculis perpaucis albis ad latera; auriculis valde inaequalibus, anticis amplis, sub-flexexuosis, posticis vix nullis.
THE BRAMBLE PECTEN. Shell somewhat triangularly ovate, higher than long, equivalve, nearly equilateral, profusely finely ridged, ridges alternately larger, densely prickly-scaled, deep vermilion, with a very few whitish spots at the sides; ears very unequal, the anterior large and flesuous, the posterior almost none. Hab.— ? A delicate finely prickly-scaled species, of a deep vermilion colour, with the ears very unequal.» LOVELL AUGUSTUS REEVE, 1853
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«Comparison.— Caribachlamys sentis closely resembles C. ornata in ribbing density and pattern. The ribs differ, however, in cross-sectional shape, at least in early ontogeny. In C. sentis the rib shape is high and rounded, with the rib crests not flattened, whereas in C. ornata the ribs at least in early growth have an I-beam cross-section, with the crests flattened and non-scaly and the rib sides strongly undercut. Specimens from the northern Bahamas identified herein as C. sentis are very close to being transitional between the two species in rib shape in early ontogeny. Unworn shells of C. ornata have dense antimarginal striae present on the flattened rib crests, whereas in C. sentis such rib-crest striae are not so strongly developed. Caribachlamys sentis tends to have more uniform coloration than does C. ornata and generally does not develop the strongly contrasting color pattern that is common in most C.ornata, where dark maroon spots or bars form on a stark white background. Caribachlamys sentis and C. ornata also tend to differ in living habits. Where the two occur in the same area, C. sentis is generally found at more protected sites on reefs, whereas C. ornata lives in the more turbulent areas of the reef front.
Caribachlamys sentis also closely resembles Crassadoma multistriata (eastern and central Atlantic and southwestern Indian Ocean) in ribbing pattern, color, and color pattern. In C. multistriata, however, the prodissoconch is of the normal plesiomorphic type, with a PI1 stage that is relatively large compared to PI (Fig. 5a); in C. sentis the prodissoconch is almost entirely composed of the PI stage, the PII stage being only a narrow fringe or absent (Figs. 7a, d). C. sentis also differs from C. multistriata in having a somewhat less inflated shell and in generally lacking a distinct groove along the center of the outer surface of its byssal fasciole. Aside from the difference in prodissoconch morphology, young individuals of the two species can be distinguished on the basis of microsculpture. In C. sentis the spaces between commarginal lirae of the early commarginal stage are occupied by well-developed antimarginal striae; in C. multistriata, antimarginal striae between commarginals are either very poorly developed or absent. Living habits.— Byssally attached beneath coral heads and between rocks and coral rubble on reef crests in shallow backreef areas, on near-shore rock jetties, and in deeper fore-reef rubble zones; depth range from just below low tide level to about 30 m. Deeper offshore specimens are dead shells only, known to occur as deep as 52 m. Diaz et al. (1991), reporting on the molluscan fauna of the Santa Marta area of Colombia, found Caribachlamys sentis living in three types of habitats: (1) at a depth of 22 to 27 m at base of the reef front on a bottom of "conglomerates of coral rubble partly bound together by sponges; dead coral heads and scattered debris patches may also be present." (2) at a depth of about 8 to 15m, with the bottom described as "upper reef-slope with large coral heads forming caves and an intricate system of cryptic microhabitats. Species of sea fans, sea whips, and sea plumes are also common." (3) at depths less than 10 m, with the bottom described as "rocky boulders and pebble partly covered by filamentous algae, crusting zoanthids, and fire corals. This zone is present in calm environments in shallow water." Geographic range.— From Jupiter Inlet, southeastern Florida, southward through the Florida Keys; uncommon in northern, western, and southern Gulf of Mexico [records from Flower Garden Reef, Texas, and off Tamaulipas, Mexico (USNM 764714)]; western Caribbean (Nicaragua, Panamá, Colombia); western Atlantic off Brazil as far south as the state of Santa Catarina (29ºS). The presence of the species in southern Brazil is based on Rios (1985: 222); I have not examined these specimens. Stratigraphic range.— Lower? Pliocene to present.» |
Caribachlamys sentis (Reeve, 1853); T. R. Waller, 1993, The evolution of Chlamys, figures 6m-p (above), 7a, d, g, j (below).
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«Discussion.— The only fossil Caribachlamys sentis found thus far is a single right valve (USNM(P) 474635) collected by the late S. E. Hoerle from the north side of the Caloosahatchee River, 3.4 krn (2.1 miles) west of Ortona Locks, Glades County, Florida. Unfortunately the precise stratigraphic position of this specimen is unknown, because the stratigraphic section at this site likely includes the Caloosahatchee, Bermont, and Ft. Thompson Formations. All that can be said is that it is likely that the specimen is Pleistocene in age.
I have not yet observed unequivocal pre-pleistocene fossils of Caribachlamys sentis, and my estimate of a Pliocene origin is based upon two indirect lines of evidence. First, the oldest fossil member of the tribe Crassadomini in the western Atlantic thus far identified is possibly the specimen figured by Woodring (1925, pl. 7, fig. 10) as "Chlamys (Chlamys) sp." from the Bowden Formation (Bowden shell beds) at Bowden, Jamaica. This specimen, USNM(P) 352779, is an abraded juvenile right valve only 4.4 mm in height. Its pattern of rib introduction, by ribflank intercalation, is remarkably like that at a similar growth stage of C. sentis (cf. USNM 764710). The microsculpture of the specimen does not appear to be preserved except for traces of antimarginal striae on the anterior and posterior edges of the disk and disk flanks and some obscure traces of commarginal lirae. The prodissoconch of the specimen is not preserved, but the impression of it remains on the underlying shell material. This impression has a length of 163 μm, exactly the length that one would expect for the prodissoconch of a Caribachlamys. The prodissoconchs in species of Crassadoma are, so far as known, of a larger size (about 200 μm). On this basis the specimen is placed tentatively in Caribachlamys, and it may well be an early representative of C. sentis. The Bowden beds are now considered to be early Pliocene in age (see below, under Spathochlamys vaginula). Secondly, the next oldest fossil Caribachlamys thus far discovered occur in the "Pinecrest beds" and Caloosahatchee Formation of Florida of late Pliocene and early Pleistocene age (see below). These specimens, however, are identified with either Caribachlamys paucirama, new species, or C. mildredae, both of which have morphological features that are more derived than are the corresponding features of C. sentis (see preceding discussion of the genus Caribachlamys and Fig. 8). This suggests that C. sentis itself must have been present before the time of deposition of these beds. Woodring (1982: 590) identified "Chlamys sentis (Reeve)?" from the Emperador Member of the La Boca Formation, Lower Miocene, of Panamá, but neither his illustrated specimen (USNM(P) 647216) nor the other two specimens to which he referred are members of this species. Rather they appear to belong to the genus Dimarzipecten Ward, 1992, which is discussed below under Spathochlamys, new genus. Recently Garrafielo and Távora (1989) included Chlamys sentis in a list of species from the Pirabas Formation, early Miocene, Brazil. This identification is doubtful, however, because they include Chlamys japericensis Ferreira, 1960, originally described from the Pirabas Formation, as a junior synonym of C. sentis. A specimen of C. japericensis sent to the USNM by Dr. Ferreira has shagreen microsculpture and is not a Caribachlamys.» WALLER, T. R. 1993. The evolution of Chlamys (Mollusca: Bivalvia: Pectinidae) in the tropical western Atlantic and eastern Pacific. American Malacological Bulletin, 10 (2): 195-249 [p. 219-221]
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Chlamys (Chlamys) sp; W. P. Woodring, 1925, Miocene mollusks from Bowden, Jamaica, plate 7 figure 10.
Chlamys sentis (Reeve)?; W. P. Woodring, 1982, Geology and paleontology of Canal Zone and adjoining parts of Panama, plate 100, figure 9.
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