Aequipecten paranensis pennatus del Río, 1992
DEL RÍO, C. J. 1992. Middle Miocene bivalves of the Puerto Madryn Formation, Valdes Peninsule, Chubut Province, Argentina (Nuculidae-Pectinidae), Pt. I. Palaeontographica, Palaeontologie A, 225: 1-58 [p. 37, pl. 6, figs. 3-5, text figs. 15, 17: 2, 19: 2]
«Aequipecten paranensis pennatus n. subsp.
Plate 6, fig. 3-5; Text-figs. 15, 17: 2, 19: 2 Holotype: CPBA 14.654 from Salina Grande, Puerto Madryn Formation, Middle Miocene (DEL RIO collection).
Material: Holotype, twenty nine right valves and forty left valves from Salina Grande: CPBA 14.614-14.653, CPBA 14.655-14.665, CPBA 15.382-15.390; Punta None: CPBA 13.305-13.311, CPBA 13.786-13.787, CPBA 14.589-14.613 (PN5). All material from Puerto Madryn Formation, Middle Miocene (DEL RIO collection). Derivatio nominis: From the latin pennatus: winged. Diagnosis: This subspecies of Aequipeeten paranensis (D'ORBIGNY) is distinguished by larger and longer auricles, right valve more convex and higher plicae which are subrectangular in cross section and sculptured with three high and top-flattened secondary riblets, being the central one wider than the laterals. Description: Shell of medium size, thick, height about equal to length, equiconvex to lightly right-convex. Apical angle obtuse (100º - 120º), Hinge margin long and straight (L/AL x 100 = 60% - 75%). Right valve with anterior auricle sculptured with 8 to 9 wide radial riblets. Byssal notch moderately deep and wide with apex angular to rounded. Posterior auricle with 9 to 13 fine radial riblets; free margin straight without basal inflection and forming right angles at junctures with outer ligament. Resilial pit equilateral, triangular and broad. Two pairs of distinct cardinal crura. Surface of disks sculptured with 17 to 25, usually 16 to 21 high plicae, subrectangular in cross section, wider than interspaces and longitudinally striated by 3 high, flat-topped secondary ribs that start at 25 mm from the beaks being the central riblet wider than the ones situated on both sides. Left valve with anterior auricle sculptured with 16 to 22 very fine riblets and posterior with 13 to 20 riblets. Plicae of disks sharper in cross section than on the right valve and top of plicae with prominent secondary riblets than on the opposite valve. Measurements in mm:
Comments: Aequipecten paranensis pennatus n. subsp. is only found in the upper section of the Puerto Madryn Formation at Punta None and Salina Grande. On the other hand Aequipecten paranensis paranensis characterizes the basal and middle strata of this unit.
This new subspecies resembles Aequipecten paranensis s. str. (D'ORBIGNY) in outline of valves, number of plicae and slopping of free margin of posterior auricle (see comments of Aequipecten paranensis paranensis) but both taxa are distinguished because the former has higher subrectangular plicae, longer auricles, shells equiconvex to rightconvex and more inflated than Aequipecten paranensis pennatus (D'ORBIGNY).» CLAUDIA JULIA DEL RÍO, 1992 |
C. J. del Río, 1992, plate 6
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