Reticulochlamys borjasensis Del Rio, 2004
DEL RÍO, C. J. 2004. Revision of the large neogene pectinids (Mollusca: Bivalvia) of Eastern Santa Cruz and Chubut Provinces (Patagonia: Argentina). Journal of Paleontology, 78 (4): 690-699, figs. 1-6. [p. 693, figs. 4.5, 4.6]
2004 Reticulochlamys borjasensis Del Río, 2004
C. J. del Río, 2004, figure 4.
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«Diagnosis.— Shell slightly prosocline, longer than high, very weakly inflated, and strongly inequivalve, with concave left valve and weakly convex right one. Auricles small, with free margin of posterior auricles inclined posteriorly. Shagreen microsculpture poorly developed as patches on both valves; antimarginal ridgelets well developed on both valves.
Description.— Shell large, attaining height of 160 mm, prosocline, longer than high; right valve weakly convex, left valve concave. Umbonal angle 105 degrees. Auricles small, subequal; hinge length 32–40 percent of total shell length; free margins of posterior auricles inclined posteriorly, and free margin of left anterior auricle inclined towards anterior; shallow byssal notch retained in adults. Shell with five rounded plicae that weaken ventrally, three central ones higher than lateral ones; secondary scaly riblets cover both plicae and interspaces. Shagreen microsculpture only detected on auricles, and as patches on both valves, more commonly on right than on left valves. Antimarginal ridgelets well developed on both valves. Etymology.— From Punta Borjas, a fossiliferous locality where this species is very abundant. Type.— Holotype, an articulated shell MACN—pi 4641 from Punta Borjas (basal horizons of the Chenque Formation, Early Miocene); length: 134 mm; height: 125, 8 mm. Other material examined.— Seven right valves, six left valves, and one articulated specimen, CPBA 8514, CPBA 8580, CPBA16.901, CPBA 16.904, MACN—pi 4642, MACN—pi 4643–4647. Occurrence.— This species is only recorded from the basal fossiliferous horizons of the Chenque Formation exposed at Astra, and from Punta Borjas north to Caleta Cordova. It is abundantly represented by articulated specimens and commonly associated with Jorgechlamys centralis, J. juliana, ‘‘Chione’’ patagonia Philippi, 1887, and Peonza torquata Olivera et al., 1994. Discussion.— Reticulochlamys borjasensis differs from R. proximus in having smaller, more weakly inflated shells that are longer than high, concave left valves, shorter auricles with a slightly deeper byssal notch retained in adults, lower plicae, antimarginal microsculpture well developed on both valves, especially strong on right ones, and poorly developed shagreen microsculpture on left valves.» CLAUDIA JULIA DEL RÍO, 2004
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