Brownstein—On the theropods of the Ellisdale Site (Campanian) 92(6):1115–1129
limb shafts of theropod dinosaurs, identified as such due to their hollow interiors. NJSM13087 and NJSM16607 are very poorly preserved and not identifiable past large Theropoda indet. NJSM 13096, the likely partial metatarsal of a tyrannosauroid similar to Dryptosaurus, bears dozens of puncture marks, scrapes, and deformations fromthe teeth of the large crocodylian Deinosuchus (e.g., Schwimmer, 2002, 2010).
NJSM13087, NJSM13096, andNJSM16607 are all partial
Materials.—NJSM 16623 (Fig. 7.1–7.3), NJSM 15319 (Figure 7.4, 7.5), maxillary or dentary teeth. NJSM 13096 (Fig. 7.6), NJSM 16607, NJSM 13087, partial limb shafts.
Remarks.—NJSM 15319 and NJSM 16623 are referred to Theropoda based on their curvature and laterally compressed state. NJSM 13096, NJSM 16607, and NJSM 13087 are referred to Theropoda based on their hollow interiors.
Discussion
Taphonomic implications of the Ellisdale theropod specimens. —The theropod specimens described vary heavily in the state of their preservation. Several specimens, including the larger tooth in NJSM 14158, the teeth NJSM 14404, NJSM 13734, and NJSM 12346, and the limb elements NJSM 16651 and NJSM 14686, are fairly well preserved, with intact denticles and other small morphological features and lacking wear from erosion. The other specimens described show much more significant wearing, such as that observed on the pedal phalanx NJSM 14682 or the smaller tooth included in NJSM 14158. These two states of preservation among the Ellisdale specimens suggest that portions of the assemblage traveled from sites varying in proximity to the final area of deposition of the bones and teeth, a model consistent with that proposed by Denton and Tashjian (2012). Indeed, the possibility remains that the Ellisdale ther- opod specimens represent taxa from multiple different biomes that existed progressively inland from the coastline.
Comparison of the Ellisdale and western North American theropod tooth morphotypes.—An extensive catalogue of lit- erature has documented theropod tooth faunas from western North America, often in order to better account for dinosaur diversity and extinction during the Late Cretaceous (e.g., Currie et al., 1990; Baszio, 1997; Fiorillo and Gangloff, 2000; Sankey, 2001; Sankey et al., 2002, 2005; Weishampel et al., 2004; Fanti and Miyashita, 2009; Larson and Currie, 2013; Williamson and Brusatte, 2014). Recently, Larson and Currie (2013) quantita- tively established distinct morphotypes of small theropod teeth among the specimens known from the western interior. These morphotypes include saurornitholestine, dromaeosaurine, Par- onychodon, Zapsalis, cf. Pectinodon, cf. Troodon, Richar- doestesia gilmorei,and R. isosceles teeth (Larson and Currie, 2013). The latter five morphotypes are importantly distinguish- able from all smallish theropod teeth collected from the Ellisdale site. None of the Ellisdale teeth have the isosceles-triangle shape characteristic of Richardoestesia isosceles, the very large, api- cally oriented denticles characteristic of troodontid teeth, the prominent longitudinal ridges or blade-like mesial denticles characteristic of Zapsalis teeth, or the prominent enamelwrinkles
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found on teeth assigned to Paronychodon (e.g., Larson and Currie, 2013; Williamson and Brusatte, 2014). Thus, none of the Ellisdale specimens can be referred to troodontids or R. isosceles. However, some of the Ellisdale teeth are somewhat similar to the saurornitholestine, dromaeosaurine, and Richardoestesia mor- photypes described by Larson and Currie (2013). As such, more explicit identification of differences between those morphotypes and the Ellisdale specimens was warranted. The denticles of the Ellisdale theropod teeth assigned to
dromaeosauridmorphotypeA differ from those of saurornitholes- tine teeth from western North America (e.g., Larson and Currie, 2013; Williamson and Brusatte, 2014) in lacking interdenticular sulci that project onto the crown. Furthermore, the dromaeosaurid morphotypeAteeth ofEllisdale are significantly larger than any of the saurornitholestine, dromaeosaurine, or Richardoestesia gil- morei Currie, Rigby, and Sloan, 1990 teeth described by Larson and Currie (2013), their CHs are comparable to or larger than those of the teeth of the very large Maastrichtian dromaeosaurid Dakotaraptor steini (e.g., DePalma et al., 2015). However, the saurornitholestine teeth of western North America are similar to the Ellisdale dromaeosaurid morphotype A teeth in having apically projecting, peg-like distal denticles, a trait distinguishing both morphotypes from dromaeosaurine teeth (e.g., Sankey et al., 2002; Larson and Currie, 2013;Williamson and Brusatte, 2014). Furthermore, dromaeosaurid teeth from Ellisdale assigned to morphotype A lack the twisting mesial carina indicative of the teeth of Dromaeosaurus or closely related taxa (Currie et al., 1990; Currie, 1995; Sankey et al., 2002; Turner et al., 2012; Larson and Currie, 2013; Williamson and Brusatte, 2014). The Ellisdale dromaeosaurid morphotype A teeth are further distin- guished from R. gilmorei in having relatively large, visible denticles compared to the small, minute ones of that taxon (e.g., Larson and Currie, 2013;Williamson and Brusatte, 2014). The dromaeosaurid morphotype Bteeth of the Ellisdale site
are, like the teeth included in morphotype A, distinguishable from dromaeosaurine teeth in having stronger apically project- ing distal denticles (forming an ~60° angle with the carina) and from saurornitholestines in not having interdenticular sulci that extend onto the tooth crown to create a “peg-like” outline for each denticle (e.g., Larson and Currie, 2013; Williamson and Brusatte, 2014). Rather, the dromaeosaurid morphotype B teeth from Ellisdale possess wave-like, “hooked” distal denticles that are most similar to those of Paronychodon, although teeth assigned to the latter taxon are wider labiolingually at their bases and have prominent enamel wrinkles (e.g., Larson and Currie, 2013; Williamson and Brusatte, 2014). Indeed, the distal denticles of the dromaeosaurid teeth from Ellisdale included in morphotype Bare arguably more apically recurved than those of western saurornitholestine teeth and certainly more so than those of R. gilmorei (e.g., Larson and Currie, 2013). As noted previously in the literature, differences in tooth
morphology among tyrannosauroids are harder to quantify due to the morphological similarity of the teeth of different tyrannosauroid taxa (e.g., Samman et al., 2005; Williamson and Brusatte, 2014). However, several key differences distin- guish the Ellisdale tyrannosauroid teeth from those of western tyrannosaurids. The ziphodont condition in some western tyrannosauroid teeth has been discussed as an indicator of the juvenile nature of the individuals from which such teeth came
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