534
Journal of Paleontology 91(3):512–547 Type.—Dasyatis ujo Rafinesque, 1810 (Cappetta, 2012).
Dasyatis sp. Figure 9.7–9.11
Occurrence.—STRI 290109, STRI 290113, STRI 290116, and YPA105.
Figure 9. Batoid I: Rhynchobatus, Urobatis, and Dasyatis SEM images from the Chucunaque Formation. (1–3) Rhynchobatus sp., UF 281314, indeterminate position in apico-lingual, baso-labial, and occlusal view, respectively; (4–6) Urobatis sp., UF 281316, indeterminate female tooth in lingual, baso-labial, and occlusal view, respectively; (7–11) Dasyatis sp.:(7–9) UF 281233, indeterminate female tooth in apico-lingual, baso-labial, and occlusal view, respectively; (10, 11) UF 281237, indeterminate male tooth in apico-lingual and labial view, respectively.
The lingual face is smooth and overhangs the root. There is a shallow depression at the crown-root contact that forms a distinct ridge. The root is divided by a medial groove that forms two prominent root lobes with flat bases; in lingual view the right lobe is significantly larger, indicating a lateral position. The flat, lozenge-shaped crown is a diagnostic feature of a female (Cappetta, 2012; Pimiento et al., 2013a). The imaged specimen (Fig. 9.4–9.6) has a CL = 0.63mm and a CW = 1.05mm.
Materials.—Two isolated teeth; female lateral position: UF 281315–16.
Remarks.—Urobatis sp. recognized in the Gatun Formation (Pimiento et al., 2013a) is similar to that of the Chucunaque Formation described above, however the specimen from the Gatun Formation has a smooth transverse depression on the lingual half of the crown. It is possible that they reflect two different species, or that they represent positional differences. Specimens from the Gatun Formation and the Chucunaque Formation share similarities with the extant Urobatis halleri (previously referred to as Urolophus halleri; Cappetta, 1987, 2012), which today is found in the eastern Pacific from northern California to Panama (McEachran, 1995). Urobatis halleri is a demersal species known to occur in depths of 0–91m (Michael, 1993), but most frequently occurs at depths of 0–21m (Love et al., 2005).
Family Dasyatidae Jordan, 1888 Genus Dasyatis Rafinesque, 1810
Description.—In apical view, female teeth have an elliptical outline with a reticulate surface and a transverse keel; the surface becomes smooth toward the lingual face and forms a completely smooth lingual uvula; the labial face overhangs well over the root forming a prominent ridge. Thick root divided into two lobes by a deep, transverse groove; there is a large foramen nested within the transverse groove; the base of the root lobes is flat with a semicircular to triangular outline. The male teeth have a higher crown with a triangular outline and a prominent cusp that is smooth and lingually oriented; the occlusal surface is fluted, forming distal and mesial crests; there is also a weak medial, labio-lingual ridge and irregular folds on the convex labial edge. The root is bipartite with rounded lobes that are divided by a deep nutrient groove. Female and male teeth differ in that the female teeth have reticulate surface with a transverse crest, no prominent cusp, and broader root lobes. Also, the occlusal surface of female teeth is somewhat rounded and convex, whereas the male teeth have amore triangular appearance (Purdy et al., 2001).The female tooth (Fig. 9.7–9.9) has a CH = 1.30mm, CW = 2.34mm, and CL =
1.56mm.Themale specimen imaged (Fig. 9.10, 9.11) has a CH = 1.38mm, CW = 2.33mm, and CL = 1.63mm.
Materials.—Nineteen isolated teeth; three male: UF 281228, UF 281237; 14 female: UF 281229, UF 281231–36, UF 281238; two indeterminate: UF 281230.
Remarks.—Dasyatis sp. has not been identified in Panama, from either the Gatun Formation or the overlying Chagres Formation. The closest related species known from the Gatun Formation is Taeniura aff. T. grabata (Pimiento et al., 2013a), which is in the family Dasyatidae (now recognized as Taeniurops aff. T. grabata by Cappetta, 2012). Purdy et al. (2001) recognized three species of Dasyatis from the Lee CreekMine:D. say,D. centroura,
andD.cf. americana,however D. centroura is only known from dermal denticles and
D.cf. americana is only known from a single tooth. Dasyatis say specimens from the Pungo River Formation and the Yorktown Formation range from CH = 2.6–3.8mm and CW = 2.8–3.9mm, which is larger than the specimens identified herein. Cappetta (1987) reported that teeth of this genus can be up to 6mm wide, nearly three times as large as the teeth from the Chucunaque Formation and twice as large as the teeth described fromLeeCreek. Extant species of this genus have a demersal habit and are common in subtropical to tropical waters (Compagno, 1984).
Family Myliobatidae Bonaparte, 1838 Genus Aetobatus Blainville, 1816
Type.—Raja narinari Euphrasen, 1790 (Cappetta, 2012).
Aetobatus sp. Figure 10.1–10.3
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