Interchlamys jacobiana (Cooke, 1919)
COOKE, C. W. 1919. Tertiary mollusks from the Leeward Islands and Cuba. In: T. W. Vaughan (ed.), Contributions to the Geology and Paleontology of the West Indies, 103-156 p., pls. 1-16. Carnegie Institution of Washington, Washington, DC. [p. 139, pl. 11, figs. 7a-b, 8]
1919 Pecten (Aequipecten) jacobianus Cooke, 1919
C. W. Cooke, 1919, plate 11.
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«The following is a description of this species:
Shell equivalve, slightly oblique, moderately convex, with about 16 low, broad, radiating medial ribs and several additional obsolete distal ribs; additional radial sculpture of raised threads, usually one on summit and one or more on each side of every rib and one or two in the interspaces, increasing in number by interpolation towards the periphery; concentric sculpture of low, wavy lamellae, crossing ribs, threads, and interspaces; Camptonectes striation present; posterior ears oblique, with faint radiating threads crossed by fine lamellae; anterior ears the larger, with coarser threads; byssal notch about one-half the length of the ear; ctenolium present; inner margin grooved in accordance with the external ribbing, but grooves do not extend over the medial portion of the disk. Alt., 29 mm.; lat., 27.5 mm.; diameter, 9 mm. Localities.— Santiago, Cuba, stations 3436, 3440 (type), 3443, 3447, Vaughan. Geologic horizon.— Oligocene. Type.— U. S. Nat. Mus. No. 167115.» CHARLES WYTHE COOKE, 1919
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«Description.— Shell not known to exceed 38 mm Ht, height exceeding length through most of ontogeny, becoming equal to length in largest specimens, equilateral and equiconvex with convexity of closed, articulated shell ca. 25-30% of Ht; disk gapes absent; disks with 18-19 radial ribs originating gradually in early ontogeny after smooth zone marked by widely spaced antimarginal striae; ribs in central sector low and trigonal, with central keel, bordered by rib flanks that slope at low angle to very narrow interspace; edges of rib flanks becoming slightly raised adjacent to interspace or giving rise to secondary radial costae so that two costae occupy interspace separated by narrow central intercostal space; rarely with single medial costa in some but not all rib interspaces; additional secondary costae on rib crests near margin of large individuals; lateral ribs very low to obsolete, these areas then dominated by secondary costae. Commarginal lamellae prominent, looping proximally over rib crests and distally over interspaces, absent over central keels of rib crests, not forming distinct spines. Disk flanks low and rounded, all but right anterior flank having scabrous radial costellae. Auricles small relative to size of disk, total hl ca. 60% of L, ahl longer than phl; right anterior auricle with 4 or 5 strong, scabrous costae and deep byssal notch with active ctenolium; other auricles with more numerous very fine costae, tending to become obsolete on posterior auricles; anterior margin of left anterior auricle sigmoidal, with shallow byssal sinus and overall trend of anterior margin forming acute angle with dorsal margin; posterior margins of posterior auricles outwardly slightly convex, forming obtuse angle with dorsal margin of ca. 110°. Right hinge dentition dominated by dorsal teeth, resilial teeth poorly developed; internal plicae with carinated edges near shell margin; muscle scars and extent of internal shell layers not accessible.
Holotype and measurements.— Holotype, USNM 167115, 1 articulated DV, 28.5 mm Ht, 26.7 mm L (Cooke, 1919: pl. 11, figs 7a-b; Pl. 2, Figs 14-16). Type locality.— USGS 3440, northeastern portion of Santiago, Cuba; fossils on hillside (Cooke, 1919: 109), La Cruz Formation, Pliocene. Other material.— Dominican Republic: Gurabo Formation, late Miocene, locality NMB 17277, Río Yaque del Norte, southern end of Angostura Gorge, in "dense coral carpet of thinly branched poritids near top. Massive coral heads below (Siderastrea, Porites and large Coscinaraea up to 60 cm diameter) with large branching Montastrea. Most corals in living position." (Saunders et al., 1986: text-fig. 27): 2 DV, 3 RV, 2 LV. Cuba: La Cruz Formation, Pliocene: USNM 167116 (USGS 3436), southern side of Santiago, Cuba, along trocha [trail] in small escarpment separating Terrace I from Terrace 2 of coastal shelf, 20-ft level, 2 RV, 3 LV; USNM 167110 (USGS 3446), first deep cutting on railroad east of La Cruz, near Santiago, Oriente Province, 2 RV, 3 LV; USGS 3440 (type locality), 5 DV; USGS 3443, northeastern portion of Santiago, marls at foot of hill, 1 LV; USGS 3447, Trocha de Santiago de Cuba, Oriente Province, second exposure on northern side of trocha [trail] east from waterfront, stratum 3 (Cooke, 1919: 109), 1 DV, 1 LV. Puerto Rico: USGS 21911, Urbano Magueyes, Peñueles quadrangle, Puerto Rico meter grid coordinates 20900N, 131000E, Ponce Limestone, 1 RV, 2 LV, associated with Leopecten gatunensis and therefore assumed to be of Late Miocene age. Remarks.— The age of the occurrence of Interchlamys jacobiana in the Dominican Republic along the Río Yaque del Norte (NMB 17277) has not been precisely determined, although it is clearly stratigraphically lower than the occurrence of I. interlineata at the opposite (downstream) end of Angostura Gorge. The nearest age determination stratigraphically below NMB 17277 is at NMB 17316, said to be late Miocene on the basis of ostracodes determined by Bold (in Saunders et al., 1986: 30), but there is no dating information between this locality and the upper end of the gorge, which is thought to be near the Miocene-Pliocene boundary (Saunders et al., 1986: 30). It would appear, then, that NMB 17277 is late Miocene (Messinian) in age. In Cuba, Interchlamys jacobiana has the same type locality (USGS 3440) as I. cruciana, the latter regarded herein as a junior synonym of I. interlineata. The vague data for this locality (see above), however, leaves room for the possibility that in Cuba, as in the Dominican Republic, I. jacobiana could stratigraphically underlie I. interlineata. The occurrence in the Ponce Limestone of southern Puerto Rico is reported for the first time. Although many paleontologists have regarded the age of the Ponce to be Miocene, they have disagreed as to which part of the Miocene (Monroe, 1980: 82). Bold (1969) concluded that the formation is latest Miocene in age on the basis of ostracodes. Comparison.— Compared to Interchlamys interlineata, I. jacobiana has radial sculpture of lower relief, especially on the lateral sides of the disks adjacent to the disk flanks, and its rib interspaces commonly have a secondary costa on each side of a very narrow, central trough. Single medial costae are not consistently present, even on the same valve, and are commonly off set to one side. Distally pointing scales are well developed in I. interlineata but not in I. jacobiana. Evolution.— See remarks for the genus Interchlamys n. gen. Occurrence.— In the Dominican Republic, Interchlamys jacobiana is known only from near the basal part of the Mao Adentro Limestone Member of the Mao Formation, of probable latest Miocene age. Distribution.— Outside of the Dominican Republic, Interchlamys jacobiana is known from southeastern Cuba in the vicinity of Santiago and La Cruz, Oriente Province, La Cruz Formation, of probable Pliocene age (Bold, 1975: 131; see also Remarks above). The species has also been identified from the lower member of the Ponce Formation in southern Puerto Rico.» WALLER, T. R. 2011. Neogene Paleontology of the Northern Dominican Republic. 24. Propeamussiidae and Pectinidae (Mollusca: Bivalvia: Pectinoidea) of the Cibao Valley. Bulletins of American Paleontology, 381: 1-197, pls. 1-18. [p. 32-34]
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Interchlamys jacobiana (Cooke, 1919); T. R. Waller, 2011, Neogene Paleontology of the Northern Dominican Republic, plate 2, figures 14-17.
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