Ckaraosippur 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. 1098]
«Ckaraosippur new genus
Type species.— Pecten calderensis Möricke, 1896, Bahía Inglesa Formation (Atacama Region), “Lo Abarca Beds” (Valparaíso Region, Navidad Formation) and “Isla Mocha Beds” (Biobío Region), Chile.
Other included species.— Ckaraosippur camachoi n. gen. n. sp., Camarones Formation (Chubut Province, Argentina).
Diagnosis.— Shell subcircular, opisthocline, postero-dorsal margin straight, sculptured with primary, secondary, and tertiary ribs covered with widely spaced scales and separated by very narrow interspaces; left auricles bearing numerous fine ribs.
Occurrence.— Earliest middle Miocene–Pliocene from Chile and Patagonia, Argentina.
Etymology.— “Stone with ribs” (ckarao = rib, sip’pur = stone) in Kunza, the native Atacamenian dead language, in reference to their shells sculptured with ribs.
Remarks.— Ckaraosippur n. gen. is characterized by the presence of subcircular and opisthocline shells with a shallow byssal sinus, umbonal angle between 89° and 97°, a very elongated hinge margin, extended 57–59% of total disc length, left auricles bearing numerous very fine ribs (Fig. 7.2), disc sculptured with numerous single ribs, separated by interspaces ornamented with one to three primary and secondary ribs (Fig. 6). Ribs on disc lateral sides and towards the ventral margin are covered with low and widely spaced scales. Shagreen microsculpture is present at least in the umbonal area of the left valve.
Ckaraosippur n gen. differs from Dietotenhosen n. gen. in having smaller valves that are higher than long, no plicate shells, a narrower umbonal angle, postero-dorsal margin of the disc straight, and left auricles covered with numerous thinner ribs. Also, in Ckaraosippur n. gen. the interspaces are narrower and entirely sculptured with ribs fromearly growth stage, while in Dietotenhosen n. gen., the interspaces are wider and not completely covered with ribs, having spaces between ribs. Ckaraosippur n. gen. resembles Chlamys s.s. in not having plicate valves, being instead ornamented with ribs (Fig. 6.15). However, there are some consistent morphological differences to distinguish the two taxa. Discs of Ckaraosippur n. gen. are opisthocline with a straight postero-dorsal margin, left anterior auricle develops a shallower byssal sinus, and it is ornamented with numerous thinner ribs. Also, in Ckaraosippur n. gen., fewer primary ribs on right valve are bifurcated in early ontogeny, whereas in Chlamys s.s., the discs are acline or prosocline with a concave postero-dorsal margin, left anterior auricle develops a deep byssal sinus, and is covered with fewer and coarser ribs. Finally, in Chlamys s.s., ribs on right valves are always bifurcated and bifurcations occur in different growth stages, even in late ontogeny (Table 1). Ckaraosippur n. gen. has medium-sized shells sculptured with ribs, which distinguish it from any other southern South American Chlamydini having plicate shells, such as those species included in the genera Reticulochamys, Jorgechlamys, Zygoclamys, Moirechlamys, Chockenia, and Dietotenhosen n. gen. (see Table 1). Also, Ckaraosippur n. gen. differs from the Miocene Pixiechlamys in having shells without growth ledges (external and commarginal disruption of shell margin convexity, affecting the entire thickness of the shell; Carter et al., 2012) and sculptured with ribs that bear few low scales, and auricles with a shallow byssal sinus and larger posterior ones.»
MARÍA BELÉN SANTELLI & CLAUDIA JULIA DEL RÍO, 2019
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Ckaraosippur calderensis (Möricke, 1896) n. comb., figures 6.1-6.11; Ckaraosippur camachoi n. gen. n. sp., figures 12-15.
Ckaraosippur calderensis (Möricke, 1896) n. comb., figure 7.1; Ckaraosippur camachoi n. gen. n. sp., figures 7.2-7.5.
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