Perez et al.—Miocene sharks and rays from Lago Bayano, Panama
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represent growth during cold seasons and dark bands represent growth during warm seasons (Calliet et al., 1985, 1986, 2006; Calliet and Goldman, 2004).
Subdivision Batoidea Compagno, 1973 Order Rajiformes Berg, 1940
Family Rhynchobatidae Garman, 1913 Genus Rhynchobatus Müller and Henle, 1837
Type.—Rhinobatus laevis Bloch and Schneider, 1801 (Cappetta, 2012).
Rhynchobatus sp. Figure 9.1–9.3
Occurrence.—STRI 290116.
Description.—In apical view, the crown is convex with a transverse crest dividing the lingual and labial faces. On the labial face, the crown is downward sloping with awell-defined uvula and secondary keel; there are foramina on the mesial and distal edges of the root. The lingual face is smooth with a high root that forms a distinct ridge at the crown-root contact; there is a prominent medial groove, with a foramen, that divides the root and lateral lobes on both the mesial and distal edges, giving the root a trilobate form (Pimiento et al., 2013a). The dimensions of this specimen are a CW = 4.17mm, a CL = 2.48mm, and a CH = 3.64mm.
Materials.—One isolated tooth; indeterminate position: UF 281314.
Figure 8. Non-dental elements from the Chucunaque Formation. (1–11) Carcharhiniform centra: (1–4) UF 281195, posterior, anterior, ventral, and dorsal view, respectively (scale bar = 1cm); (5–7) UF 281196, anterior, posterior, and dorsal view, respectively (scale bar = 1cm); (8, 9) UF 281400: (8) indeterminate anterior-posterior face (scale bar = 200μm); (9) indeterminate dorsal-ventral face (scale bar = 100μm); (10, 11) UF 281399, indeterminate anterior-posterior face and indeterminate dorsal-ventral face, respectively (scale bar = 100μm). (12–14) Myliobatiformes incertae sedis: (12, 13) UF 281317, caudal spine in lateral and dorsal view, respectively (scale bar = 1mm); (14)UF 281499, caudal spine in dorsal view (scale bar = 1mm); (15, 16) Batomorphii incertae sedis, UF 281401, dermal denticle in apical and lateral view, respectively (scale bar = 1mm). Photo credit: S. Moran.
specimens to genus or species. Purdy et al. (2001) identified vertebrae of Hemipristis serra, Galeocerdo cf. G. cuvier,and Carcharhinus spp. based on dispersal of nutrient pores and the shape of dorsal and ventral foramen. Vertebrae from the Chucunaque Formation lack characteristics to warrant identifi- cation beyond Carcharhiniformes, in part because of their preservation, but mostly due to their inherent non-descript nature. Chondrichthyan vertebral centra have been recovered from the Eocene Tonosi Formation (Vasquez and Pimiento, 2014) and the early Miocene Culebra Formation (Pimiento et al., 2013b) of Panama. The four centra described here are the first chon- drichthyan vertebral elements described from the lateMiocene of Panama. Despite their lack of taxonomic information, vertebral centra can provide a lot of information about the individual from which they originated and the environment in which they resided. Vertebral centra have coupled growth bands, in which light bands
Remarks.—The dimensions of this tooth are much larger than those reported from the Gatun Formation (length = 0.9mm, width = 0.9mm; Pimiento et al., 2013a); however Compagno (1987) reported a CWof up to 5mmfor
Rhynchobatus.Aguilera and Rodrigues de Aguilera (2001) documented this genus from the Miocene of Venezuela. There are six extant species of Rhynchobatus that occur in the tropical and subtropical Indo- Pacific and a single species in the eastern Atlantic, R. luebberti (Compagno and Marshall, 2006). Rhynchobatus luebberti is a benthic species often occurring in the intertidal zone, from 0–70m depth, but most commonly found in less than 35m depth (Compagno and Marshall, 2006). Rhynchobatus djiddensis is a reef-associated species that occurs inshore and in shallow estu- aries, generally between 2 and 50m depth (Sommer et al., 1996).
Order Myliobatiformes Compagno, 1973
Family Urotrygonidae McEachran et al., 1996 Genus Urobatis Garman, 1913
Type.—Raja (Leiobatus) sloani Garman, 1913 (Cappetta, 2012).
Urobatis sp. Figure 9.4–9.6
Occurrence.—YPA105.
Description.—In apical view, the crown has an elliptical to nearly hexagonal outline with a reticulate ornamentation, a transverse depression, and a significant lingual protuberance.
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