Nodipecten veracruzensis Smith, 1991
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, 155 p., figs. 1-18, pls. 1-38. [p. 100, pl. 14, figs. 2-4, 6-7]
«Nodipecten veracruzensis n. sp.
Plate 14, figures 2, 3, 4, 6, 7 Holotype.— USNM 334986, a left valve measuring 6.9 cm high, 7 cm long.
Paratypes.— Universidad Nacional Autonoma de Mexico, a right valve of a late juvenile 4.6 cm high, 4.7 cm long; USNM 334985, a right valve 5.3 cm high, 5.6 cm long; UCMP 37398, 334985; also in the collections at CAS and LACMIP, all disarticulated valves. Type locality. Veracruz, Mexico, southeast of Coatzocoalcos. Along Mexican Highway 180,14 mi east of junction with side road into Coatzocoalcos. Third cut on north side of road, in very coarse quartz yellow-brown sandstone (TU 638, collectors, Harold and Emily Vokes). Agueguexite Formation, middle Pliocene, zone N 20 (Akers, 1974, 1979). Description.— Valves flat to slightly convex, nearly circular in outline; beaks do not project beyond hinge line. Anterior auricles twice as long as posterior auricles, both with five or more radials. Byssal notch shallow; hinge line slightly less than shell length. Umbonal angle 88-93°, varying with shell convexity. Right valves with 6-8 strongly paired ribs ornamented by fine radials and concentric growth lines. Some individuals with transverse laminae that obscure the radial macrosculpture. Concentric growth lines in juvenile interspaces give way to radial threads in adults. Left valves with six or seven very low, rounded-rectangular ribs of alternating widths described by the Nodipecten scheme N r Nc r N. Juveniles as much as 2 cm high commonly have incipient nodes on alternate ribs; most specimens have 0-2 generations of nodes. The largest individual measured 9.4 cm high, 10 cm long (USNM 334984, from loc. TU 1046). Variability.— The species is known from about 75 disarticulated individuals from two localities in Veracruz; they do not show significant morphologic variation. Most specimens are 5 cm high, inferred to be late juveniles or young adults. Juvenile rib profiles are higher than in adults. Ctenolia are not preserved in right valves over 5 cm high. Comparative morphology.— The taxon approaches N. veatchii and N. peedeensis in rib count, macrosculpture, and rib spacing, but differs in lower rib profiles, lack of ledges and nodes, and smaller size. The morphologic characters of N. veracruzensis are seen in some variants of the Holocene Florida Nodipecten, N. fragosus, which is rare off the Yucatan Peninsula (USNM 715050, TU R-84). One of these, USNM 715050, has similar paired ribs and transverse laminae in juvenile interspaces, but it is distinguished by rib count: N. veracruzensis has 6 ribs, N. fragosus has 6-8, the anterior- and posterior-most riblets being narrow. Anterior and posterior edges of N. veracruzensis have underdeveloped or incipient riblets, if any. Phylogenetic affinities.— Nodipecten veracruzensis is younger than the oldest Gulf of Mexico Nodipecten fragosus. Valve proportions, small number of ribs, and fine reticulate microsculpture ally it with the Tertiary Caribbean cognates N. veatchii from Baja California Sur, Mexico and N. peedeensis from the Carolinas. The central space on right valves has transverse laminae as in N. peedeensis and N. fragosus. Geographic distribution and stratigraphic occurrences.— Southern Mexican Coastal Plain, southeastern Veracruz (TU 638,1046), in a lower yellow facies and also in an upper grey facies at TU 638. It was unknown at the time other Agueguexite Formation mollusks were described by Perrilliat (1963), who regarded those assemblages as late middle Miocene in age. Geologic age.— Middle Pliocene; planktonic foraminiferal zone upper N 20 at TU 638 and TU 1046 (W.H. Akers, written commun., 1981).» JUDITH TERRY SMITH, 1991
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J. T. Smith, 1991, plate 14.
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