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Journal of Paleontology 91(3):512–547 Type.—Mobula auriculata Rafinesque, 1810 (Cappetta, 2012).
Mobula thurstoni (Lloyd, 1908) Figure 11.1–11.15
Holotype.—Originally described as Dicerobatis thurstoni by Lloyd (1908).
Occurrence.—STRI 290109 and YPA105.
Description.—In occlusal view, teeth have a roughly elliptical outline with a “blistered” ornamentation. The lingual edge is irregular and cuspidate, whereas the labial edge is convex or sinuous. The number of cusps on the lingual edge increases in more elongate specimens (Adnet et al., 2012) and the enamel extends well onto the root on the lingual face. The labial visor is rounded and may be incised with furrows. The root may have two or more lobes, depending on the position of the tooth and the age of the individual (Adnet et al., 2012); the root is narrow relative to the crown. The crown slopes inward basally, creating an angular contact with the divergent root lobes. In UF 281256 (Fig. 11.11–11.13), the root is divided into two lobes by a shallow medial groove (e.g., holaulacorhize stage); in labial view, the right lobe is larger, indicating a left lateral position. Teeth range from CH = 0.47–0.63mm, CW = 0.98–1.40mm, and CL = 1.37–2.04mm.
Materials.—Sixteen isolated teeth; lateral: UF 281256, UF 281291–93, UF 281295, UF 281481; indeterminate position: UF 281283–85, UF 281288, UF 281294, and UF 281482.
Remarks.—Adnet et al. (2012) noted reduced sexual dimorphism in Mobula thurstoni, with the only major difference being that males are more deeply scored by furrows on the labial face. Pimiento et al. (2013a) identified two female teeth as Mobula thurstoni from theGatun Formation. The specimen ofM. thurstoni imaged in Pimiento et al. (2013a) has four cusps on the lingual edge, irregular folding on the labial edge, and a relatively smooth occlusal surface (CW = 0.6mm and CL = 1.1mm), which bears a strong resemblance to the female teeth of Mobula tarapacana described byAdnet et al. (2012). The additional cusps on the Gatun specimen can be explained by the fact that the number of cusps increases as teeth become more elongate (Notarbartolo Di Sciara, 1987; Adnet et al., 2012). Adnet et al. (2012) provisionally placed M. thurstoni into a group of Mobulids characterized by having comb-like teeth, along with M. munkiana and M. hypostoma,but distinguished M. thurstoni from the latter two by having an
ornamented crown and shorter cusps. However, this distinction is tenuous (Adnet et al., 2012) and may not hold true in the fossil record. This species likely has a circumtropical distribution, but is known from scattered reports throughout the Pacific and Atlantic (Notarbartolo Di Sciara, 1987; Compagno, 1997). Extant indivi- duals occur in oceanic and coastal waters, but most frequently are encountered in coastal environments from 0–100m (Notarbartolo Di Sciara, 1988; McEachran and Notarbartolo Di Sciara, 1995; Clark et al., 2006a).
Mobula cf. M. tarapacana (Philippi, 1892) Figure 11.16–11.25
Holotype.—Originally described as Cephaloptera? tarapacana from Chile by Philippi (1893, p. 8, pl. 3, fig. 2).
Occurrence.—STRI 290109 and UF YPA105.
Description.—Sexual dimorphism is a marked character in Mobula tarapacana (Adnet et al., 2012). Male teeth are elongate in occlusal view with deeply scored furrows and a subhexagonal outline. The labial edge is convex and slightly irregular. The lingual edge is sharp and cuspidate. The crown apex is much broader than the base of the crown. The root is polaulocorhizid with numerous labiolingually compressed lobes (Fig. 11.16– 11.20). Female teeth have a relatively smooth occlusal surface with a subhexagonal outline. The crown is high relative to the root, with a slender profile. Adnet et al. (2012) observed crown heights two to three times greater than the root height in extant individuals. The labial edge is deeply grooved and the lingual edge is irreglularly cuspidate. The root is polaulocorhizid, root lobes are rounded and irregularly divided.
Materials.—Ten isolated teeth; male: UF 281270–71, UF 281276, UF 281485, UF 281497; female: UF 281289, UF 281483–84; indeterminate: UF 281487.
Remarks.—Mobula tarapacana has not previously been reported from the fossil record of Panama. Mobula cf. M. tarapacana specimens from the Chucunaque Formation have a significant dental sexual dimorphism, primarily reflectedbythe stronger ornamentation ofmale
teeth.Adnet et al. (2012) also observed this feature in extant individuals, however the deep labiolingual furrows exhibited in the fossil specimens seem more irregular. It is possible that this morphotype represents an extinct species. Cappetta (1970) noted similarities with the extant species, Mobula tarapacana, in his original description of Mobula loupianensis and
Figure 11. Batoid III: Images of Mobula teeth from the Chucunaque Formation. (1–15) Mobula thurstoni (Lloyd, 1908): (1–5) UF 281291, lateral tooth in occlusal, lingual, labial, basal, and profile view, respectively; (6–10) UF 281292, anterolateral tooth in occlusal, lingual, labial, basal, and lateral view, respectively; (11–13) UF 281256, SEM image of a left lateral tooth in occlusal, lingual, and labial view, respectively; (14, 15) UF 281283, SEM image of a lateral tooth in occlusal and lateral view, respectively; (16–25) Mobula cf. M. tarapacana (Phillippi, 1893): (16–20) UF 281270, lateral male tooth in occlusal, lingual, labial, basal, and lateral view, respectively; (21–25) UF 281289, lateral female tooth in occlusal, lingual, labial, basal, and lateral view, respectively; (26–50) Mobula sp.: (26–31) Type I: (26, 27) UF 281279, SEM image of a lateral tooth in occlusal and lateral view, respectively; (28–30) UF 281280, SEM image of an anterior tooth in occlusal, lingual, and labial view, respectively; (31) UF 281287, SEM image of a indeterminate tooth position in occlusal view; (32–45) Type II: (32, 33) UF 281243, SEM image of an anterior tooth in occlusal and lateral view, respectively; (34, 35) UF 281241, SEM image of an anterior tooth in occlusal and lateral view, respectively; (36–38) UF 281251, SEM image of an aneterior male tooth in occlusal, lingual, and lateral view, respectively; (39, 40) UF 281253, SEM image of a lateral male tooth in occlusal and lateral view, respectively; (41–45) UF 281490, lateral tooth in occlusal, lingual, labial, basal, and lateral view, respectively; (46–50) Type III: (46–48) UF 281255, SEM image of a female? lateral tooth in occlusal, lingual, and apico-labial view, respectively (49, 50) UF 281299, SEM image of a female? tooth in occlusal and lingual view, respectively (scale bars = 1 mm).
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