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Journal of Paleontology 90(1):102–132
Systematic paleontology Sauropoda Marsh, 1878
Macronaria Wilson and Sereno, 1998
Titanosauriformes Salgado, Coria, and Calvo 1997 Family Brachiosauridae Riggs, 1903 Genus Sonorasaurus Ratkevitch, 1998 Sonorasaurus thompsoni Ratkevitch, 1998 Figures 9–16, 18–21, 24, 25
Figure 8. Carcharodontosaurinae indet., theropod dinosaur tooth (ASDM 330) from the mid-Cretaceous Turney Ranch Formation of Arizona, USA. Abbreviations: den = denticles.
its preserved base measures 2.9 cm mesiodistally by 1.2cm labiolingually. Denticles are visible and their density can be mea- sured on the apical part of the distal margin (density=2 denticles/ mm), about themid-height of the distalmargin (2.8 denticles/mm), and mid-height of the mesial margin (3.4 denticles/mm) (Fig. 8). Denticle densities in these regions in Acrocanthosaurus average 2.7, 2.9, and 2.7 denticles/mm, respectively (Smith et al., 2005), so only the mid-height of the distal margin is similar in this regard. The presence or absence of enamel wrinkles, which are present in Acrocanthosaurus (D’Emic et al., 2012; Hendrickx et al., 2015), cannot be assessed. The lateral profile of the tooth when viewed lingually or labially is weakly sigmoid in outline with a concave basal and convex apical portion, which was suggested to be diagnostic of Carcharodontosaurinae (Hendrickx et al., 2015). Based on this feature, the denticle density, and overall proportions, we refer this tooth to Carcharodontosaurinae.
Shellenberger Canyon material.—Schafroth (1968) reported the presence of dinosaur bones in the Shellenberger Canyon Formation of the Bisbee Group, but no further information was given. A sauropod fibula and sternal plate were reported from the Shellenberger Canyon Formation (McCord and Gillette, 2005), which is subjacent to the Turney Ranch Formation (Ratkevitch, 1998). The sternal plate is incomplete, so not much can be gleaned from its anatomy. The fibula is similar in robustness to that of Sonorasaurus, with a robustness index (average of anteroposterior dimension of proximal + midshaft + distal ends/length; Wilson and Upchurch, 2003) of 0.17 in the former versus approximately 0.16 in the latter (Table 2). Its lower-level affinities are uncertain. In sum, the presence of a basally branching titanosauriform
(Sonorasaurus), cf. Tenontosaurus, and a carcharodontosaurine theropod (similar to Acrocanthosaurus) suggests that the dinosaur fauna of the Turney Ranch Formation was similar to that of other middle Cretaceous North American faunas (see D’Emic and Foreman, 2012, and references therein). We cannot support nor refute the identification of nodosaurids nor Deinonychus in the fauna (McCord and Gillette, 2005), although those taxa would strengthen the apparent faunal similarity based on the limited data at hand.
Holotype.—Each fragment of the holotype received its own catalog number, so in several instances, multiple numbers sig- nify the same assembled element. All bones of the holotype fall under the numberASDM500, the remains of a single individual composed of 5 posterior dorsal vertebrae (ASDM 500-4, -12, -52, -104 [two conjoined vertebrae]), ten mid-posterior caudal vertebrae (ASDM 500-6, -7, -8, -9, -297/299, -10, -296, -300, -302, -11 [in relative order within the vertebral series]), several (ca. 30) fragments of dorsal ribs (ASDM 500), fragments of one or both scapular blades (ASDM 500-370, -36), a partial right humerus (ASDM 500-45, -323, -483, -479, -54), a right ulna (ASDM 500-58, -23, -24, -25), left and right radii (right:ASDM 500-1, left: ASDM 500-33, -49, 496), right metacarpals I (ASDM 500-316, -317, -495), II (ASDM 500-491, -493), III (ASDM 500-290, -298), and IV (ASDM 500-251, -490, -315), a fragmentary left ilium (ASDM 500-30, -371, -372, -373, -379), the pubic peduncle of the right ilium (ASDM 500-480, -586), a right tibia (ASDM 500-2), a right fibula (ASDM 500-3), right metatarsals I (ASDM 500-287), II (ASDM 500-284, -285), IV (ASDM 500-282), and V (ASDM 500-278), right phalanx I. 1 (ASDM 500-283), right phalanx ?II.1 (ASDM 500-288), right phalanx ?II.2 (ASDM 500-279), right phalanx ?III.1 or ?IV.1 (ASDM 500-286), two right fragmentary manual or pedal unguals (ASDM 500-509, -289), and many fragments. Aquarry map of the site is presented in Ratkevitch (1997b).
No available photographs confirm the exact placement of the bones depicted on this map, but it is certain that all bones of ASDM 500 came from a single quarry and many were found in contact with one another (R. Thompson, personal communica- tion, 2014). The humerus on the quarry map listed by Ratkevitch (1997) is likely the tibia, which is located adjacent to the fibula, whereas the bone labeled “femur” is the humerus. Like the tibia and fibula, one radius and ulna are depicted in near-articulation, and the other radius is depicted near the metacarpals. The metacarpals and phalanges are depicted near the tibia and fibula, some caudal vertebrae are depicted in articulation, and some rib shafts are depicted as parallel to one another. Thus, if this quarry map is accurate, then this individual was somewhat articulated upon burial. There are also several dozen unidentifi- able fragments from the site. Ratkevitch (1998) attributed chevrons, a pubis and ischium, cervical vertebrae, and gastro- liths to the holotype of Sonorasaurus, but these could not be recognized in the ASDM collections (aside from the polished stones labeled as gastroliths) and are excluded from the holotype here. Furthermore, there is no anatomical basis to confirm nor deny referral of a large dorsal rib (ASDM 807) to Sonorasaurus thompsoni made by Ratkevitch (1998). Although it was stated to come from “the same horizon” (Ratkevitch, 1998:72),
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