Caribachlamys Waller, 1993
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, figs. 1-14. [p. 217]
«Caribachlamys Waller, new genus
Etymology.— The name Caribachlamys combines a prefix signifying Caribbean with the genus name Chlamys.
Diagnosis.— Byssate, non-cemented Crassadomini with lecithotrophic-type prodissoconch (large PI stage, short or absent PII stage); strong antimarginal striae present between commarginal lirae in rib interspaces in early ontogeny.
Type species.— Pecten sentis Reeve, 1853.
Other species.— Pecten ornatus Lamarck, 1819; Caribachlamys paucirama Waller, new sp.; Pecten (Chlamys) imbricatus mildredae Bayer, 1941; Ostrea imbricata Gmelin, 1791.
Geographic range.— Caribbean Sea and adjacent waters of the warm-temperate to tropical western Atlantic from North Carolina to Brazil and Bermuda.
Stratigraphic range.— Upper Pliocene to Recent.
Discussion.-- The new genus Caribachlamys is based on the discovery that four extant species of the Caribbean and adjacent waters share a unique prodissoconch morphology (Figs. 7a-f) and a unique pattern of commarginal and antimarginal microsculpture in rib interspaces (Figs. 7g-l). The phylogenetic relationships of these extant species and one new extinct species are shown in Figure 8. Caribachlamys ornata (Node B, Fig. 8) resembles C. sentis very closely in ribbing pattern but differs in developing smooth-crested scaleless ribs that are I-beam shaped in cross-section. In the Bahamas the two species nearly intergrade in that specimens identified herein with C. ornata develop I-beam shaped ribs only in very early ontogeny and otherwise resemble C. sentis (see following section on C. ornata). C. paucirama, C. mildredae, and C. imbricata have ribs that have a plesiomorphic rounded cross-sectional shape (not I-beam shaped) like that in the likely stem species, C. sentis, meaning that it is unlikely that C. ornata can have given rise to any other species in the genus. C. paucirama, C. mildredae, and C. imbricata are united (Node C, Fig. 8) by decrease in prominence of the early commarginal iirae in rib interspaces and by the onset of substantial irregularity in the trends of these lirae. At Node D, C. paucirama develops an autapomorphy: rib introductions beyond a shell height of 20 mm are few in number or absent altogether, leading to a pattern of ribs of fairly uniform height and spacing at the distal margin. Caribachlamys mildredae and C. imbricata (Node E) share fasciculation of ribs, increase in scale spacing on major ribs, a tendency toward cusping of scales, and marked flattening of the left disk. Finally, C. imbricata (Node F) has evolved a unique ribbing pattern consisting of 9 or 10 major plicae with a tendency for secondary ribs to be eliminated. The scales on the ribs of this species commonly form closed knobs, the left disk is markedly flattened, and the maximum observed irregularity and inconsistency in direction of the early commarginals is reached.»
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Caribachlamys sentis; T. R. Waller, 1993, The evolution of Chlamys (Mollusca: Bivalvia: Pectinidae) in the tropical western Atlantic and eastern Pacific, figures 6m-6p.
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