Lyropecten Conrad, 1862
CONRAD, T. A. 1862a. Descriptions of new Genera, Subgenera and Species of Tertiary and Recent Shells. Proceedings of the Academy of Natural Sciences of Philadelphia, 14: 284-291. [p. 291]
«LYROPECTEN, Conrad.
Inequivalve, radiately costate; hinge with a triangular pit as in Pecten and diverging prominent teeth on each side the ligament cavity.
Lyropectin (Pallium) estrellanus, C, Pacific R. R. Reports, 1855, vi. pl. 3, f. 15. This genus is peculiar to the Miocene of the Pacific slope, and appears in three large species, the second of which has been figured and described as Pallium estrellanum, in Pacific Railroad Reports, vol. vii. 191, but is very distinct from that species. I propose to name it Volaeformis.» TIMOTHY ABBOT CONRAD, 1862
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Pecten (Lyropecten) estrellanus Conrad; R. Arnold, 1906, The Tertiary and Quaternary pectens of California, plate 19.
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Lyropecten estrellanus
(Conrad, 1856); J. T. Smith, 1991, Cenozoic Giant Pectinids from California and the Tertiary Caribbean Province, plate 22, figures 1, 4, 7. |
«Lyropecten (Conrad, 1862)
Type species.— Pallium estrellanus Conrad, 1856 (subsequent designation, Dall, 1898).
Conrad (1867) reintroduced his new genus Lyropecten and listed one species, L. crassicardo, not recalling that in 1862 he had already described the genus and listed two species, P. estrellanus and P. crassicardo. Diagnosis.— Valves circular in outline, equally convex in profile; moderately flat to gibbous, some species tending to have rounded or angular ledges. Radiating ribs ornamented by radial costae in most taxa (but not the type species); interspaces with one or more radial riblets crossed by concentric lirae or growth lines. Auricles subequal, costate, and lirate, hinge line less than half shell length. Byssal notch moderately deep, ctenolium present in juveniles, preserved in some adults. Three pairs of hinge teeth in right valves, two pairs in left valves. Some species with regularly spaced ribs, others with prominent key ribs arranged in patterns characteristic of different phylogenetic lineages within the genus. Some of the species with key ribs also have nodes.
Similar to Nodipecten in valve outline and profile, hinge characters, ctenolium, and fine sculpture; unlike Nodipecten in having nearly equal auricles, a shallow byssal notch, and regularly spaced ribs rather than left valve ribs and right valve interspaces of alternating widths. Most species lack nodes, but in the group including L. crassicardo and L. magnificus, hollow nodes evolved over time from elongate thickenings along key ribs. Nodipecten nodes are commonly larger and bulbous. Lyropecten differs in growth form and proportions from "Macrochlamis," which is represented in California by taxa having large auricles, hinge lines greater than half the shell length, a shallow byssal notch, and no tendency to develop ledges, key ribs or nodes. Vertipecten has many characters that distinguish it from Lyropecten: a convex left valve and flat right valve, the number and character of imbricated ribs, shagreen microsculpture, deep byssal notch, and a smooth hinge area lacking crura.» SMITH, J. T. 1991. Cenozoic Giant Pectinids from California and the Tertiary Caribbean Province: Lyropecten, "Macrochlamis", Vertipecten, and Nodipecten species. United States Geological Survey Professional Paper, 1391: v + 1-155, figs. 1-18, pls. 1-38.
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