Journal of Paleontology, 92(6), 2018, p. 1115–1129 Copyright © 2018, The Paleontological Society. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. 0022-3360/15/0088-0906 doi: 10.1017/jpa.2018.42


The distinctive theropod assemblage of the Ellisdale site of New Jersey and its implications for North American dinosaur ecology and evolution during the Cretaceous


Chase D. Brownstein Stamford Museum and Nature Center, Stamford CT ⟨chasethedinosaur@gmail.com⟩


Abstract.—The Cretaceous landmass of Appalachia has preserved an understudied but nevertheless important record of dinosaurs that has recently come under some attention. In the past few years, the vertebrate faunas of several Appalachian sites have been described. One such locality, the Ellisdale site of the Cretaceous Marshalltown Forma- tion of New Jersey, has produced hundreds of remains assignable to dinosaurs, including those of hadrosauroids of several size classes, indeterminate ornithopods, indeterminate theropods, the teeth, cranial, and appendicular elements of dromaeosaurids, ornithomimosaurians, and tyrannosauroids, and an extensive microvertebrate assemblage. The theropod dinosaur record of the Ellisdale site is currently the most extensive and diverse known from the Campanian of Appalachia. Study of the Ellisdale theropod specimens suggests that at least four or more non-avian theropod taxa are represented at the site, including tyrannosauroids, ornithomimosaurs, several different morphotypes of dromaeo- saurids that are the first of that clade described from New Jersey, and indeterminate theropods. The specimens are important for increasing current knowledge about the theropod diversity of the Atlantic Coastal Plain (ACP) during the Campanian by representing the most speciose assemblage of the group during the time in the ACP as well as for shedding light on Appalachian dinosaur ecology and biogeography generally.


Introduction


The landmass of Appalachia was created when the Western Interior Seaway flooded the interior of North America and separated the eastern portion of the continent from the west midway through the Cretaceous (Roberts and Kirschbaum, 1995; Russell, 1995; Schwimmer, 1997, 2002; Sampson et al., 2010). The fossil record of dinosaurs from the portion of eastern North America that corresponds to Appalachia is poor (e.g., Weishampel and Young, 1996; Schwimmer, 1997; Weisham- pel, 2006), but the publication of several new taxa (e.g., Carr et al., 2005; Prieto-Márquez et al., 2016a, 2016b) and the first reports of some clades of dinosaur (e.g., ceratopsians) from this landmass (Longrich, 2016; Farke and Phillips, 2017) in the past several years have greatly increased our knowledge of the obscure fauna of the landmass. The discovery of several new sites in the eastern United


States has also illuminated the vertebrate faunas of Appalachia (e.g., Weishampel, 2006; Denton et al., 2011; Schwimmer et al., 2015). Study of these faunas has had broad implications for modeling the evolution of several clades of dinosaurs, generally suggesting that Appalachia harbored relict forms isolated from more derived relatives on other landmasses and continents by the Western Interior Seaway (e.g., Weishampel and Young, 1996; Schwimmer, 1997; Carr et al., 2005; Bru- satte et al., 2011; Denton et al., 2011; Schwimmer et al., 2015; Prieto-Márquez et al., 2016a, 2016b). Examples include the Stokes Quarry site of South Carolina, from which teeth and


other elements attributed to the tyrannosauroid Appalachio- saurus montgomeriensis Carr, Williamson, and Schwimmer, 2005, the dromaeosaurid Saurornitholestes langstoni (Sues, 1978), and one or two other dromaeosaurid morphotypes have been described (Schwimmer et al., 2015).Other important sites include Phoebus Landing in North Carolina, which has pre- served teeth and postcranial elements comparable to Drypto- saurus aquilunguis (Cope, 1866) and other tyrannosauroids, Lophorhothon, and Hadrosaurus, as well as the bones of ornithomimosaurs and the holotype of the gigantic hadro- sauroid Hypsibema crassicauda (Cope, 1869) (e.g., Miller, 1967; Baird and Horner, 1979; Weishampel and Young, 1996; Schwimmer, 2016), and the Hannahatchee site of Georgia, which has preserved teeth and postcranial remains assigned to Appalachiosaurus montgomeriensis, indeterminate ornitho- mimosaurs, and indeterminate hadrosaurids (e.g., Schwimmer et al., 1993). These sites have also been noted for their microvertebrate remains, including those of mammals, small squamates, and amphibians, making such localities extremely significant to research regarding faunal changes in North America during the Late Cretaceous (e.g., Grandstaff et al., 1992; Gallagher, 1993, 1997; Weishampel and Young, 1996; Denton et al., 2004, 2011). One of the most important Late Cretaceous fossil sites from


the eastern United States, an outcrop of the middle to late Campanian Marshalltown Formation (which is equivalent in age to the upper Tar Heel and Donoho Creek formations of the Carolinas; e.g., Miller et al., 2004; Harris and Self-Trail, 2006),


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