532
Journal of Paleontology 91(3):512–547
Holotype.—Originally described as Zygaena mokarran by Ruppell (1837, p. 64, pl. 18, fig. 1). According to Klausewitz (1960), a 2515mm stuffed male from Massaua, Red Sea, SMB 3590, serves as a lectotype in Naturmuseums Senckenberg (Compagno, 1984).
Occurrence.—STRI 290109 and STRI 300032.
Description.—Moderately large teeth with a broad, serrated crown; straight or convex mesial edge and straight distal edge with a distal inclination that forms a deep notch; and a prominent distal heel that is rounded and serrated. The root is robust with a deep nutrient groove that penetrates a horizontal basal margin. Sphyrna mokarran from the Chucunaque Formation ranges from CH = 6.6–9.8mm and CW = 9.3–14.7mm.
Materials.—Four isolated teeth; upper: UF 275043, UF 275066, and UF 281184.
Remarks.—Sphyrna mokarran is easily distinguished fromother species of Sphyrna by its larger size and regular serrations. Pimiento et al. (2013a) noted the paucity of documented occurrences of Sphyrna mokarran in the fossil record, mention- ing that in the Neotropics it has only been reported from the Miocene of Cuba without any description of the specimens (MacPhee et al., 2003). Teeth from the Chucunaque Formation are comparable in size to those found in the Gatun Formation (CH = 7.6–9.4mm and CW = 9.6–16.4mm; Pimiento et al., 2013a). Extant individuals reach a maximum TL = 6.1m and have a circumtropical distribution, occurring close inshore and well offshore (Compagno, 1984). Sphyrna mokarran most commonly populates bottomand reef associated waters in a depth range of 1–80m (Compagno, 1984; Compagno et al., 2005).
Sphyrna zygaena (Linnaeus, 1758) Figure 7.19–7.26
Holotype.—Originally described as Squalus zygaena by Linnaeus (1758, p. 234); however,Compagno (1984) does not acknowledge a holotype.
Syntype.—Naturhistoriska Riksmuseet, Department of Vertebrate Zoology, Ichthyology Section, Stockholm, Sweden, NRM 88, 215mm specimen.
Occurrence.—STRI 290109, STRI 300032, STRI 430011, STRI 430012, and YPA105.
Description.—Moderately broad, labio-lingually flattened crown; convex to sigmoidal mesial edge and straight to concave distal edge. There is a distal inclination forming an acute notch with a rounded distal heel. The cutting edges and heel may or may not bear weak serrations. The root is thick with a transverse groove that penetrates a horizontal basal margin. Anterior teeth are more erect and lack the acute distal notch. Sphyrna zygaena from the Chucunaque Formation range from CH = 2.6–8.1mm and CW = 4.8–9.6mm.
Materials.—Ninety-six isolated teeth; indeterminate position: UF 275044, UF 275058, UF 275073, UF 275142, UF 281175, and UF 281371–73.
Remarks.—Sphyrna zygaena tend to have thicker, broader crowns and a more sigmoid mesial edge than Sphyrna lewini; however, the differences between the two species are sparse, especially in smaller individuals of S.
zygaena.Compagno (1988) noted that there is weak ontogenetic heterodonty in the genus Sphyrna. In juveniles and young adults of the extant S. zygaena, teeth have smooth cutting edges, but larger individuals become weakly serrate (Gilbert, 1967). Gillette (1984) originally identified S. zygaena from the Gatun Formation, however Pimiento et al. (2013a) reassigned these teeth to S. lewini (CH = 2.7–5.4mm and CW = 5.2–11.0mm) and Sphyrna sp. (CH = 3.1–8.9mm and CW = 7.4–10.6mm). Purdy et al. (2001) reported teeth from the Pungo River Formation occurring in a size range of CH = 8.0–11.0mm, which corresponds with the larger teeth identified as S. zygaena from the Chucunaque Formation. Teeth fromall three formations are much smaller than the upper limit of 20mm reported by Cappetta (1987). Extant Sphyrna zygaena inhabit all temperate and tropical seas, andmost commonly occur in coastal waters over continental shelves from depths of 0–200m (Compagno et al., 1989); however, it has been proposed that the distribution of S. zygaena in tropical environments is incompletely known due to probable confusion with S. lewini (Casper et al., 2005).
Order Carcharhiniformes incertae sedis Figure 8.1–8.11
Occurrence.—STRI 290139, STRI 290145, and YPA105.
Description.—Scyliorhiniod-type (Tessman, 1966) vertebral centra with smooth dorsoventral edges and two sets of paired foramina; the caudal and cranial faces are concave with a circular to oval-shaped outline and distinct annuli, except in the smallest specimen (UF 281399). In lateral view, the centra have a cylindrical, disk-like to hourglass shape. Posterior vertebrae are more compressed than anterior positions (Kent, 1994). The shape of the dorsal and ventral foramina, the presence or absence of septa, and the distribution of vertebral pores are diagnostic characteristics for identifying different genera (Kent, 1994; Purdy et al., 2001). These centra can confidently be assigned to the order Carcharhiniformes because they lack the septate dorsoventral walls diagnostic for Lamniformes; however, they lack features that would allot for more specific identification. These centra range from a dorsoventral diameter of 1.27–33.56mm and a wall length of 0.87–14.38mm.
Materials.—Four isolated vertebrae; indeterminate position: UF 281195–96 and UF 281399–400.
Remarks.—Post-cranial elements are rare for chondrichthyan taxa. Typically the only non-dental remains recovered are vertebral centra because they are more densely calcified than the rest of the cartilaginous skeleton (Kent, 1994). However, the morphologic variability in vertebral centra is more conservative than that of teeth, making it difficult to identify isolated
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