Spondylus gumanomocon Brown & Pilsbry, 1913
BROWN, A. P. & H. A. PILSBRY. 1913. Fauna of the Gatun Formation, Isthmus of Panama. Part 2. Proceedings of the Academy of Natural Sciences of Philadelphia, 64: 509-519, pls. 22-26, text-figs. 1-5. [p. 514]
1913 Spondylus gumanomocon Brown & Pilsbry, 1913
1927 Spondylus carmenensis F. Hodson in Hodson et al.,1927
1927 Spondylus carmenensis F. Hodson in Hodson et al.,1927
Spondylus gumanomocon Brown & Pils. Paratype and type; H. A. Pilsbry, 1922, Revision of W. M. Gabb's Tertiary Mollusca of Santo Domingo, plate 43, figures, 4, 5.
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«Spondylus gumanomocon n. sp. A species resembling S. varians Sowb. (S. delessertii Chenu). The upper valve is Pectiniform, orbicular, of moderate thickness, with low radial ribs, the principal ones irregularly spinose, spines short; cardinal area small and short, as in S. americanus. Lower valve very ponderous, with a long, level (not receding) cardinal area, and a very long, straight (or sometimes laterally curved) beak, the cavity of which is deeply excavated in young shells, nearly solidly filled in old ones. Sculpture like the upper valve, except that it is more or less extensively foliated towards the beak.
Length (alt.) of a lower valve 175 mm.; breadth 108 mm.; weight 32½ oz. Santo Domingan Oligocene. This is the form identified by Gabb as Spondylus americanus.» AMOS PEASLEE BROWN & HENRY AUGUSTUS PILSBRY, 1913
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«Remarks.— The specific name S. gumanomocon was given by Brown and Pilsbry (1913) to material in the Gabb Collection, which Gabb had identified as S. americanus Lamarck, 1819. The exact locality of Gabb's five specimens remains unknown. Although we have specimens from the Rio Gurabo and the Rio Mao, the majority of our shells were collected in the Samba Hills just south of Guayubin (Iocs. TU 1221. 1245), an area that Gabb almost certainly collected. In the narrative of his travels in Santo Domingo he says, concerning the Samba Hills, near Guayubin: "They are barely fifty feet high immediately adjoining the Guayubin River, though twice that a mile or two east, and they almost disappear very soon after crossing the river. The horizontal beds continue to their southern base undisturbed, and where the road first reaches rising ground it climbs a few feet up the face of a sort of bluff, the exposed edges of a nearly horizontal sandstone, full of Oysters and Spondylus" (Gabb. 1873, p. 155).
This description fits our localities TU 1221 and 1245 (4.5 and 5 km south of the bridge at Guayubin, respectively) perfectly, for here the only shelled fossils are "Ostrea" haitensis Sowerby, 1850, and Spondylus gumanomocon (other mollusks are represented by molds). Although we are reasonably sure this is the area that Gabb's material came from, there is one difference between his material and ours: all of his shells are single valves, gray in color, and most of ours are paired valves, yellowish in color. So Gabb probably collected near our localities but not at them. For this reason, we have not restricted the type locality to one of our locality numbers. Although the majority of specimens of S. gumanomocon come from the Mao Adentro Limestone Member of the Mao Formation, the species is not confined to those beds. Maury (1917, p. 355) cited the species as occurring at "Zone D. Rio Gurabo at Los Quemados" (= locs. TU 1215, NMB 15842-15858; see Saunders, lung, and Biju-Duval, 1986. text-figs. 4, 5) and both we and the Naturhistorisches Museum team collected the species at this locality. This is not unexpected as the locality is a coral reef in the Gurabo Formation. The Naturhistorisches Museum team also collected a single valve at Canada de Zamba. in the Rio Cana drainage (loc. NMB 16818: see Saunders, Jung, and Biju-Duval, 1986. text-fig. 15) in the coralline facies of the Gurabo Formation. Furthermore, they collected one specimen from the Cercado Formation, just above the mouth of Arroyo Bellaco (loc. NMB 16853; see Saunders, Jung, and Biju-Duval, 1986. text-fig. 15) near the coral reef in that tributary, and a second specimen from the Cercado Formation just below the contact with the Gurabo Formation on the Rio Cana (Ioc. NMB 16842; see Saunders, Jung, and Biju-Duval, 1986, text-fig. 15). The species S. carmenensis Hodson in Hodson, Hodson, and Harris, 1927 [p. 41, pI. 25, figs. 1-3], described from the "Oligocene" ofthe Buchivacoa District, State of Falcon, Venezuela, but probably coming from the Miocene La Puerta Group⁴, agrees in shape and ornamentation with S. gumanomocon, and was synonymized by Palmer (1938, p. 155). We see no reason to disagree.» ⁴ The type locality was given subsequently by Hodson and Hodson (1931, p. 5) as southeast of Dabajuro. and expanded by Palmer(1938, p. 154). to "about 10 miles east and 4 miles south of Dabajura [sic]". The type locality for the La Puerta Formation (now Group) is the La Puerta syncline, southeast of Dabajuro. The Lexico Esrraligrafico de Venezuela (1970, p. 672) indicates only the La Puerta Group in the Buchivacoa District. It is the lateral equivalent of the Socorro, Urumaco and Codore formations, just to the east, and the exact stratigraphic level is uncertain.
VOKES, H. E. & E. H. VOKES. 1992. Neogene paleontology in the northern Dominican Republic. 12. The genus Spondylus (Bivalvia:Spondylidae). Bulletins of American Paleontology, 102: 5-13, pls. 1-3. [p. 12]
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Spondylus gumanomocon Brown and Pilsbry; H. E. Vokes & E. H. Vokes, 1992, Neogene paleontology in the northern Dominican Republic. 12. The genus Spondylus, plate 3, figures 1-4.
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