Ckaraosippur camachoi Santelli & del Río, 2019
SANTELLI, M. B. & C. J. DEL RÍO. 2019. New Neogene taxa of the tribe Chlamydini Teppner, 1922 (Pectinidae, Bivalvia) of southern South America. Journal of Paleontology, 93 (6): 1088-1104, figs. 1-7. [p. 1100, figs. 6.12-6.15, 7.2-7.5]
2019 Ckaraosippur camachoi Santelli & del Río, 2019
M. B. Santelli & C. J. del Río, 2019, figures 6, 7.
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«Type specimens.—Holotype, CPBA 8604a, a left valve, from Puesto Salado (Chubut Province, Camarones Formation). Paratypes, CPBA 8604b–d, two left valves and a fragment of one left valve, from the same locality as the type.
Diagnosis.— Left valve ornamented with 38–44 ribs bearing few and very low scales on lateral and ventral margins of the disc.
Occurrence.— Earliest middle Miocene from Puesto Salado (Chubut Province, Camarones Formation), Argentina.
Description.— Shell of medium size, attaining up to 70 mm in height, subcircular, higher than long, slightly opisthocline, posteriorly elongate. Hinge dorsal margin straight, 54–60% of total disc length, antero-dorsal margin concave and posterodorsal straight. Umbonal angle 88–95°. Resilifer deep, triangular-isosceles, posteriorly inclined and with a high ligamentary area. Auricles large, moderately asymmetrical, with free margins inclined anteriorly and concave, with shallow byssal sinus. Left anterior auricle sculptured with 21–24 radial ribs, left posterior auricle with 13–14 ribs. Left disc sculptured with 32 primary ribs, increasing by intercalation at 3–6 mm from umbo, attaining a maxim number of 38–44 ribs in late ontogeny. Ribs are rounded and wide, separated by narrower interspaces and bearing scarce and low scales, directed ventrally, near anterior, posterior margin, and ventral valve margins, whereas ribs on central and umbo area of disc are smooth. Scales present on ribs auricles. Interspaces sculptured with a central secondary rib and two tertiary ribs. Antimarginal microsculpture on entire disc surface from initial radial stage; commarginal lirae limited to initial radial stage; shagreen microscultpure developed as a band between 2 mm and 26 mm height on interspaces. Left auricles sculptured with antimarginal and shagreen microsculptures; thick commarginal corrugations on anterior auricle up to 2 mm height from beaks and posterior with shagreen on proximal sector.
Etymology.— This species is dedicated to Dr. Horacio Camacho, who collected the studied material and devoted his life to the study of the Patagonian Cenozoic molluscan faunas.
Dimensions (in mm).—Holotype CPBA 8604a L = 55.6 H = 60.1, CPBA 8604b L = 68.0 H = 59.4, CPBA 8604c L = 57.5 H = 64.3.
Remarks.— The studied material was collected by H.H. Camacho and J.A. Fernández at Puesto Salado (Cañadón del Salado; Camarones Formation) in strata placed in the NVG Molluscan Assemblage (earliest middle Miocene) (del Río, 2004b).
Naming a new pectinid species only based on a right or a left valve is not usually adequate because each valve has its diagnostic characters, but the distinctive ribbing pattern of our left valves permits C. camachoi n. gen. n. sp. to be distinguish from the remaining Cenozoic Chlamydini of Patagonia. Ckaraosippur camachoi n. gen. n. sp. is placed in Ckaraosippur n. gen. because it has no plicate valves (Fig. 6.15), subcircular and opisthocline shells with a straight postero-dorsal margin and auricles sculptured with numerous fine ribs. Moreover, the ribs are covered with few, widely spaced scales and they are separated by narrower interspaces. Ckaraosippur camachoi n. gen. n. sp. is distinguished from C. calderensis n. comb. in having smaller size, with more symmetrical auricles, disc ornamented with more numerous primary ribs, but sculptured with fewer ribs in late ontogeny, ribs bearing scales restricted to the margins of discs and shagreen microsculpture limited to the umbonal area (Fig. 7.3–7.5, Table 3).» MARÍA BELÉN SANTELLI & CLAUDIA JULIA DEL RÍO, 2019
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