Spathochlamys vaginula (Dall, 1898)
DALL, W. H. 1898. Contributions to the Tertiary fauna
of Florida. Silex Beds of Tampa and the Pliocene Beds of the Caloosahatchie
River. Part IV. I. Prionodesmacea: Nucula to Julia. 2. Teleodesmacea: Teredo to
Ervilia. Transactions of the Wagner Free Institute of Science of Philadelphia,
3 (4): viii, 571-947 p., pls. 23-35 (pls. 36 and 37 in part 5, 1890). [p. 715]
1898 Pecten (Chlamys) ornatus var. vaginulus Dall, 1898
Pecten vaginulus Dall; C. J. Maury, 1917, Santo Domingo Type Sections and Fossils, plate 34, figure 7.
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«Oligocene of the Bowden beds, Jamaica; Henderson and Simpson.
Seven small valves of a species closely resembling P. ornatus were obtained at Bowden; the form and sculpture are practically the same, but the ribs (twenty-one to twenty-five) are single, subequal, and not fasciculated, and are separated by simple narrower interspaces not radially threaded. The young of ornatus, as far as observed, seem to always have one or more interstitial riblets. I therefore propose for the present form the varietal name of vaginulus, which may be raised to specific rank if the difference is confirmed by the characters of adult specimens.» WILLIAM HEALEY DALL, 1898
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«Remarks.— Spathochlamys benedicti, the extant counterpart and probable descendant of S. vaginula in the western Atlantic region, lives in tropical to temperate waters at midshelf depths commonly from 40-90 m, less commonly as shallow as 2 m and as deep as 800 m (Waller, 1973, 1993). Waller (1993: 232) noted, "The deep byssal notch, prominent active ctenolium, adhering byssal threads on mature dried shells, and data taken at the time of collection all indicate that S. benedicti is probably byssally attached throughout life. Individuals attach to a great variety of substrates, including coral debris, sponges, and algal mats (Waller, 1973 and unpub. data)." The occurrences of S. vaginula in the northern Dominican Republic indicate a similar preference for deep water, evidenced by apparent restriction of the species to the Gurabo Formation where it is commonly associated with other deep-water species, particularly the pectinids Argopecten thetidis and Gurabopecten uniplicatus n. gen., n. sp. as well as the cementing bivalve, Dimya sp. (Table 5).
Comparisons.— Spathochlamys vaginula is the only member of its genus thus far found in the Neogene of the Dominican Republic. As stated by Waller (1993: 238), the species "differs from both of the extant species, S. benedicti [western Atlantic region] and S. vestalis (Reeve, 1853) [eastern Pacific], primarily in having less scaly rib crests on the central part of the disk at least in early ontogeny and in having less trigonal ribs at an early growth stage." Compared to Interchlamys (n. gen.) interlineata, S. vaginula has radial ribs that begin earlier in ontogeny after a pitted rather than smooth zone on the left umbonal area, fi ner medial costae, and more pointed, concave- up scales. Evolution.— Waller (1993) discussed the evolution of Spathochlamys and provided a phylogeny showing the origins of extant species relative to the closure of seaway connections between the Atlantic and Pacific. It was hypothesized that the genus originated in the Miocene from the earlier Miocene genus Dimarzipecten Ward, 1992, on the eastern side of the Americas, spreading to the eastern Pacific in the Late Miocene. In an analysis of shallow-water Pectinidae in the Galápagos Islands, Waller (2007: 244) provided further data relevant to the evolution of Spathochlamys, particularly in the eastern Pacifi c region. In the present study, no evolutionary trends were observed within S. vaginula in the Dominican Republic material. Occurrence.— In the northern Dominican Republic, Spathochlamys vaginula is known only from the upper Cercado Formation and the Gurabo Formation, uppermost Miocene and Lower Pliocene. Distribution.— Outside of the Dominican Republic, S. vaginula has been reported from the Middle Pliocene Bowden Formation of Jamaica (type locality) and the Middle and Upper Pliocene Jackson Bluff and Tamiami formations of Florida (Waller, 1993: 241).» 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. 37]
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Spathochlamys vaginula (Dall, 1898); T. R. Waller, 2011, Neogene Paleontology of the Northern Dominican Republic, plate 3, figures 10-14.
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«Types.— Dall (1898: 715-716) mentioned having "seven small valves" of his new variety from the Bowden Beds of Jamaica but provided no illustration, no measurements, and no type designation. This type series was subsequently referred to by Schuchert et al. (1905: 490) as "cotypes" andwas catalogued as USNM(P) 135786. The entry for this number in the catalogue, however, mentions only six valves. The discrepancy is apparently due to the recognition, after Dall's 1898 publication, that one of the seven valves does not.belong to the same species. (In fact it is an Argopecten, not a Spathochlamys.) Woodring (1925, pl. 8, figs. 1, 2) provided the first illustrations of members of the type series, a right valve and a non-matching left valve, but continued to refer to these as cotypes. The right valve illustrated by Woodring (1925, pl. 8, fig. 1) is herein selected as the lectotype and refigured (Figs. 11c-f). The type locality is USGS 2580 (see following section on materials examined)
Diagnosis.— Spathochlamys with length of anterior outer ligament commonly greater than twice length of posterior outer ligament, especially where shell height exceeds 20 mm; early ribs commonly rounded rather than trigonal in cross section, with scales variably developed or absent; ribflank costae not appearing until late in ontogeny, generally at shell heights exceeding 12 mm; medial costae variably developed, commonly weak in early ontogeny of left valve; ontogenetic persistence of commarginal lirae in rib interspaces variable, commonly persisting throughout ontogeny, with height of lirae greater than that of medial costae in early ontogeny; posterior margins of posterior auricles slightly concave to nearly straight, forming oblique angle with dorsal margin. Morphological variation.— In addition to the six valves of the type series from the Bowden Shell Beds of Jamaica, there are about 30 additional valves and fragments from the type locality (USGS 2580) in the USNM collections. The range of variation of these specimens seems to encompass the morphology of specimens from the Gurabo Formation of the Dominican Republic. In general these Bowden and Gurabo specimens have robust simple ribs that tend to be rounded in cross section in early ontogeny, becoming trigonal later. Rib-flank costae are present only on the largest specimens and commonly do not begin to form in ontogeny until a shell height of about 15 mm is reached. The Bowden and Gurabo specimens share rib counts within the range of 21 to 25. Trigonal ribs are common among the specimens from the Dominican Republic but rare among the specimens from Bowden, Jamaica. The Bowden specimens in general have more prominent commarginal lirae in rib, interspaces and medial costae that begin later in ontogeny than in the Dominican Republic. Specimens of Spathochlamys from the Tamiami Formation in a pit near Sarasota, Florida (see below), also appear to be within the range of variation of S. vaginula. The Tamiami specimens (Figs. 11k-o) differ from those of the Bowden Shell Beds of Jamaica and the Gurabo Formation of the Dominican Republic mainly in being of much greater size, with shell heights ranging from 18 to 34 mm (mean = 27 mm) compared to the maximum shell height of 17 mm for the other samples. Like the Bowden specimens, however, those from the Tamiami Formation have ontogenetically persistent commarginal lirae in rib interspaces, robust rounded major ribs, and late-appearing medial costae. A single right valve 22 mm in height [USNM(P) 474666, Fig. 11p] was collected by the author from near the base of the Jackson Bluff Formation of Florida (see following discussion of stratigraphy). It resembles the specimens from the Bowden, Gurabo, and Tamiami Formations in having poorly developed scales on the crests of ribs in the center of its disk and in lacking clearly delimited rib-flank costae. The Jackson Bluff specimen differs, however, in having fewer ribs (only 18 at the valve margin compared to 21 to 25 in the other samples). Furthermore, the ribs of the Jackson Bluff specimen are distinctly trigonal in cross-section, and a few of the central ribs bifurcate. The latter feature has been observed to occur in extant species in response to injury or simply as extremes of variation in otherwise simple-ribbed populations.» WALLER, T. R. 1993. The evolution of Chlamys (Mollusca: Bivalvia: Pectinidae) in the tropical western Atlantic and eastern Pacific. American Malacological Bulletin, 10 (2): 195-249, figs. 1-14. [p. 238]
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Spathochlamys vaginula (Dall, 1898); T. R. Waller, 1993, The evolution of Chlamys, figures 11c-p.
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«The following suplements the original description of this species:
ShelI small, thin, subequivalve, suborbicular, height slightly exceeding width, equilateral, excepting auricles, moderately inflated; right valve usually Iess inflated than left; both valves sculptured with 21 to 25 slender, square to subrounded ribs, separated by narrower interspaces; near the ventral margin of adult shells a fine radial thread lies in the interspaces; in the interspaces and occasionally overriding the ribs are fine, inconspicuous concentric lamellae; submargins without radial sculpture, or sculptured with fine radials, forming a continuous serie with those on the disk; hinge long, auricles very unequal, especially on right valve; byssal notch deep and sharply sinuated; both auricles sculptured with irregular radial ribs and concentric lamellae, sculpture on the anterior auricle coarser and more imbricate.
A right valve: length 11.8 mm.; height 12 mm.; diameter 1.9 mm.; length of hinge 7.5 mm. A left valve: length 12 mm.; height 13 mm.; diameter 2.1 mm.; length of hinge 7.2 mm. The outline of the shell is variable, as some are more orbicular than others. On some valves the anterior submargin is narrower than the posterior, and has no radial sculpture. The posterior submargin may or may not have radial sculpture. Immature right valves are fIat and have unusually long anterior auricles.
This species is smaller and has wider umbos than the living West Indian species C. ornatus (Lamarck). The thread in the interspaces is smaller than in the living species and is introduced at a later stage. Maury has recorded C. vaginulus Dall from Miocene beds in the Samba Hills, Dominican Republic. A broken valve. apparently C. vaginulus, was collected by the U. S. Geological Survey expedition from the Gurabo formation on Rio Yaque del Norte near Santiago (station 8726). The concentric lamellae on the Dominican shell are more crowded and less conspicuous on the ribs. Other localities.— Gurabo formation (middle Miocene), Dominican Republic. Type material.— 7 cotypee ( U. S. Nat. Mus. No. 135786).» WOODRING, W. P. 1925. Miocene mollusks from Bowden, Jamaica. Pelecypods and scaphopods. Carnegie Institution of Washington Publication 366: 222 p., pls. 1-28. [p. 66]
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Chlamys (Chlamys) vaginulus (Dall), W. P. Woodring, 1925, Miocene mollusks from
Bowden, Jamaica, plate 8, figures 1, 2.
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«Our shell has been examined by Dr. Dall and pronounced identical with the type of P. vaginulus, an unfigured species described from Bowden. Our specimen has twenty- three ribs with a distinct radial thread in every interspace; ears very unequal.
Length of right valve 15, altitude 16, semi-diameter 3 mm. This species is smaller than Gabb's P. interlineatus and has more numerous ribs. Locality.— (Exp'd'16) Samba Hills at an approximate altitude of 540 feet.» MAURY, C. J. 1917. Santo Domingo Type Sections and Fossils. Part 1: Mollusca. Bulletins of American Paleontology, 5 (29): 166-415, pls. 1-39. [p. 350]
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Pecten vaginulus Dall; C. J. Maury, 1917, Santo Domingo Type Sections and Fossils, plate 34, figure 7.
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