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Research 57 (2016) 199e207

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Cretaceous Research

journal homepage: www.elsevier.com/locate/CretRes

A ceratopsian from the of eastern , and implications for dinosaur biogeography

Nicholas R. Longrich

Department of Biology and Biochemistry and Milner Centre for Evolution, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom article info abstract

Article history: Tyrannosaurs and hadrosaurs from the Late Cretaceous of eastern North America (Appalachia) are Received 5 May 2015 distinct from those found in western North America (), suggesting that eastern North America Received in revised form was isolated during the Late Cretaceous. However, the Late Cretaceous fauna of Appalachia remains 12 July 2015 poorly known. Here, a partial maxilla from the Tar Heel Formation (Black Creek Group) of Accepted in revised form 11 August 2015 North Carolina is shown to represent the first ceratopsian from the Late Cretaceous of eastern North Available online 12 September 2015 America. The specimen has short alveolar slots, a ventrally projected toothrow, a long dentigerous process overlapped by the ectopterygoid, and a toothrow that curves laterally, a combination of char- Keywords: Dinosauria acters unique to the Leptoceratopsidae. The maxilla has a uniquely long, slender and downcurved pos- Neoceratopsia terior dentigerous process, suggesting a specialized feeding strategy. The presence of a highly specialized Leptoceratopsia ceratopsian in eastern North America supports the hypothesis that Appalachia underwent an extended Appalachia period of isolation during the Late Cretaceous, leading the evolution of a distinct dinosaur fauna Black Creek group dominated by basal tyrannosauroids, basal hadrosaurs, ornithimimosaurs, nodosaurs, and leptocer- atopsids. Appalachian vertebrate communities are most similar to those of Laramidia. However some taxa-including leptoceratopsids-are also shared with western , raising the possibility of a Late Cretaceous dispersal route connecting Appalachia and Europe. © 2015 Published by Elsevier Ltd.

1. Introduction duckbills, ceratopsids (Xu, Wang, Zhao, & Li, 2010b), leptocer- atopsids (Ryan, Evans, Currie, Brown, & Brinkman, 2012), pachy- During the Late Cretaceous, a shallow inland sea, the Western cephalosaurids (Longrich, Sankey, & Tanke, 2010) and Interior Seaway, extended from the to the Arctic ankylosaurids (Sullivan, 1999) show the same. These patterns show Ocean, splitting North America in two. The resulting land masses- that a high-latitude land corridor joined North America and in Laramidia in the west, and Appalachia in the east-each developed the Late Cretaceous (Russell, 1993), with extensive dispersal be- distinct dinosaurian faunas (Fig. 1). tween the two continents. In the , the appearance of Late Cretaceous from Laramidia (Weishampel et al., titanosaurs (D'Emic, Wilson, & Thompson, 2010) and large alethi- 2004) show close affinities with the dinosaurs of Asia and to a nophidian (Longrich, Bhullar, & Gauthier, 2012) in Laramidia lesser degree, . Among theropods, North America's and saurolophines (Prieto-Marquez, 2010) and multituberculate tyrannosaurids (Brusatte, Benson, & Norell, 2011), alvarezsaurs (Kielan-Jaworowska, Cifelli, & Luo, 2004) in South (Longrich & Currie, 2009a), caenagnathids (Longrich, Barnes, Clark, America indicates dispersal between Laramidia and South America, & Millar, 2013), microraptorines (Longrich & Currie, 2009b) and either via a land bridge or across a narrow ocean channel or ornithomimids (Xu et al., 2011) all have relatives in Asia. Among archipelago. ornithischians, saurolophine (Godefroit, Bolotsky, & Lauters, 2012) The Late Cretaceous dinosaurs of Appalachia are highly distinct and hadrosaurine (Prieto-Marquez, Chiappe, & Joshi, 2012) from those seen in Laramidia, however. While Laramidia is domi- nated by Tyrannosauridae (Weishampel et al., 2004), Appalachia is dominated by basal tyrannosauroids such as and & Abbreviations: AMNH, American Museum of Natural History, New York; NMC, Appalachisaurus (Brusatte et al., 2011; Carr, Williamson, Britt, National Museum of , Ottawa; YPM-PU, Yale Peabody Museum, Princeton Stadtman, 2011). Similarly, while Laramidia is dominated by lam- University Collections. beosaurine and saurolophine hadrosaurs (Weishampel et al., 2004), E-mail address: [email protected]. http://dx.doi.org/10.1016/j.cretres.2015.08.004 0195-6671/© 2015 Published by Elsevier Ltd. 200 N.R. Longrich / Cretaceous Research 57 (2016) 199e207

Fig. 1. Distribution of Leptoceratopsidae and possible dispersal routes: (1), Udanoceratops and Zhuchengceratops (Eastern Asia) (Kurzanov, 1992; Xu, Wang, Zhao, Sullivan, & Chen, 2010a), (2), Leptoceratops, , Gryphoceratops, Unescoceratops and cf. Prenoceratops () (Brown, 1914; Makovicky, 2010; Miyashita, Currie, & Chinnery-Allgeier, 2010; Ryan et al., 2012); (3) Montanoceratops, Prenoceratops, Cerasinops, and Leptoceratops (Brown, 1942; Chinnery & Horner, 2007; Ott, 2007)(Miyashita et al., 2010) (Montana); (4) Black Creek ceratopsian (this paper); (5) Kristianstaad ceratopsian (Sweden) (Lindgren et al., 2007); (6) Craspedodon lonzeensis (Belgium) (Godefroit & Lambert, 2007). in Appalachia hadrosaurine-grade hadrosaurs such as Hadrosaurus Seeley 1888. and Lophorhoton (Prieto-Marquez et al., 2012) dominate. These Marsh 1890. patterns suggest that Appalachia saw an extended period of isola- Leptoceratopsidae Nopsca 1923 tion beginning in the Late Cretaceous, becoming an island conti- Leptoceratopsidae sp. nent with an endemic fauna, similar to Australia in the Cenozoic. Unfortunately, our knowledge of Appalachian dinosaurs re- 2.1. Material mains limited (Schwimmer, 1997; Weishampel et al., 2004), with only tyrannosauroids (Brusatte et al., 2011), hadrosaurids (Prieto- YPM-PU (Yale Peabody Museum, Princeton University collec- & Marquez, Weishampel, Horner, 2006), ornithomimosaurs tion) 24964, posterior end of a left maxilla (Fig. 2). (Russell, 1972) and nodosaurs (Langston, 1960) known from the . The discovery of new dinosaurs from eastern North America is therefore of great interest to understanding the 2.2. Locality and horizon Appalachian fauna and its origins. Recently, an unusual dinosaur specimen from the Campanian Clifton Farm, Giddensville, Sampson County, North Carolina Black Creek Group of North Carolina (Fig. 1) was identified in Yale (Fig. 2). The same locality has produced a theropod tooth, probably University's Peabody Museum collections. The specimen consists of from a tyrannosauroid (YPM PU 23197), and teeth and of the the posterior end of a left maxilla. Although originally identified giant crocodilian rugosus (YPM-PU 23429). Although and catalogued as a hadrosaur, the specimen shows apomorphies of the collection is very limited, marine vertebrates such as mosa- the Ceratopsia and specifically the Leptoceratopsidae. This spec- saurs, bothremydid and sharks, which are abundant in the imen is the first ceratopsian known from the Late Cretaceous period nearby Phoebus Landing locality (Miller, 1967) were not collected of eastern North America. from the locality, suggesting a freshwater or estuarine depositional environment. Provenance data for the specimen identify it as from the “Black 2. Systematic Creek Formation”. The Black Creek Formation has since been raised to the level of group, containing three formations (Fig. 3); from Dinosauria Owen 1842. bottom to top, these are the Tar Heel, Bladen, and Donoho Creek N.R. Longrich / Cretaceous Research 57 (2016) 199e207 201

Fig. 2. Map showing outcrops of Upper Cretaceous Black Creek Group and Peedee Formation strata, and the locality of the Black Creek ceratopsian. The specimen comes from the Clifton Farm locality, south of Giddensville, Sampson County, N 35.13, W 78.22. The lower Campanian Tar Heel Formation outcrops in this area. Map after Owens and Sohl (Owens & Sohl, 1989); stratigraphic column after Harris and Self-Trail (Harris & Self-Trail, 2006). Note that the position of the specimen in the Tar Heel is currently unconstrained. formations. Maps of outcrop (Owens & Sohl, 1989) put the Clifton depending on the model used (Harris & Self-Trail, 2006). Farm locality in the Tar Heel Formation. The Tar Heel was deposited A nearby assemblage from the Tar Heel, Phoebus Landing on the during the early Campanian (Harris & Self-Trail, 2006; Mitra & Cape Fear River, has produced hadrosaurids, a possible ornitho- Mickle, 2007); previous dates, based on strontium isotopes, suggest mimosaur, and a diverse fauna of freshwater and marine verte- an age of 82.3e73.4 Ma or 74.5e82.6 Ma for the formation, brates (Miller, 1967). Recent work on Phoebus Landing suggests

Fig. 3. Black Creek ceratopsian, YPM-PU 24964, left maxilla. A, medial, B, ventral, C, lateral, D, dorsal view. Abbreviations: ag, alveolar groove; dp, dentigerous process. 202 N.R. Longrich / Cretaceous Research 57 (2016) 199e207 that the dinosaurs date to 77.1e78.5 Ma (Self-Trail, Christopher, this skull shape is characteristic of basal Neoceratopsia (You & Prowell, & Weems, 2004), the middle of the Campanian. Dodson, 2004). The process is rugose laterally, but there is a smooth dorsal facet 2.3. Description where the pterygoid would have dorsally overlapped the maxilla; pterygoid overlap of the maxilla is characteristic of neoceratopsians The preserved portion of the maxilla (Fig. 2) measures 43 mm (You & Dodson, 2004). long; the anterior end is broken away leaving only the posterior Teeth would have implanted into alveolar slots, separated by dentigerous process; the posterior end of this process is also broken interalveolar ridges (Fig. 4), as in Neoceratopsia (You & Dodson, off. Comparisons with other ceratopsians suggest that the complete 2004) and convergently in Hadrosauridae (Horner et al., 2004). maxilla may have measured ~120e160 mm. The alveolar slots are too short to accommodate more than one There is no trace of a jugal contact on the lateral surface of the replacement tooth, however, ruling out affinities with either maxilla (Fig. 3C); the jugal must have articulated well above the or Hadrosauridae, in which the alveolar grooves toothrow. In primitive ceratopsians such as (Xu, Forster, accommodate a series of replacement teeth (Dodson et al., 2004; Clark, & Mo, 2006) and (Osborn, 1923) the jugal ar- Horner et al., 2004) below the functional tooth. The shape of the ticulates more or less lateral to the toothrow. By contrast, the jugal tooth sockets is very similar to those of Leptoceratops (Fig. 4), and as articulates more dorsally in primitive neoceratopsians such as in Leptoceratops the interalveolar ridges are poorly developed Liaoceratops (Makovicky & Norell, 2006) and especially in more anteriorly, and become increasingly well-developed posteriorly advanced neoceratopsians such as Yamaceratops (Makovicky & such that they tightly embrace the tooth roots. The shape of the Norell, 2006), Protoceratopsidae (Brown & Schlaikjer, 1940; socket suggests that the tooth roots were probably ante- Maryanska & Osmolska, 1975), Leptoceratopsidae (Chinnery, roposteriorly compressed, as in Leptoceratopsidae and Eucer- 2004; Chinnery & Horner, 2007), and Euceratopsia (Dodson, atopsia (see Fig. 5). Forster, & Sampson, 2004; Wolfe et al., 2010). The toothrow was also strongly inset relative to the jugal; as can 3. Discussion be seen in ventral view, the lateral surface of the maxilla is sloped inward. This feature is also seen in Leptoceratopsidae (Fig. 3) and 3.1. Affinities other ceratopsians such as Liaoceratops (Makovicky & Norell, 2006), Yamaceratops (Makovicky & Norell, 2006) and Protoceratopsidae Although fragmentary, the morphology of YPM-PU 24964 is (Brown & Schlaikjer, 1940; Maryanska & Osmolska, 1975) but is consistent with referral to Neoceratopsia and specifically to Lep- only very weakly developed in hadrosaurs. toceratopsidae. A series of characters support this assignment. The posterior dentigerous process is elongate, with room for at least five teeth. By comparison, primitive neoceratopsians such as  Transverse expansion of the skull posteriorly (Ceratopsia). Liaoceratops (Xu, Makovicky, Wang, Norell, & You, 2002) and  Strong lateral projection of the jugal relative to the toothrow Auroraceratops (You, Morschhauser, Dodson, & Li, 2012)havea (Ceratopsia) dentigerous process bearing one or two teeth; the dentigerous  Extensive overlap of the dentigerous process by the ectopter- process of protoceratopsids bears up to three teeth (Brown & ygoid (Neoceratopsia). Schlaikjer, 1940)(Maryanska & Osmolska, 1975); Leptoceratops  Strong ventral projection of the toothrow below the jugal- has five (Fig. 3), Zuniceratops has five or six (Wolfe et al., 2010), and maxilla contact (Yamaceratops, Protoceratopsidae, Leptocer- Ceratopsidae have even more (Hatcher, Marsh, & Lull, 1907). atopsidae, and Euceratopsia). Elongation of the posterior dentigerous process occurs con-  Posterior dentigerous process elongate, with 3 or more teeth vergently in hadrosaurids (Horner, Weishampel, & Forster, 2004). (Protoceratopsidae, Leptoceratopsidae, and Euceratopsia). Although the increased number of tooth positions is shared by  Posterior dentigerous process with 5 or more teeth (Leptocer- the Black Creek ceratopsian and leptoceratopsids, the shape of the atopsidae, Euceratopsia). dentigerous process is very different. In other leptoceratopsids, the  Laterally deflected posterior dentigerous process dentigerous process is very deep, e.g. the height of the process is (Leptoceratopsidae). 130% of its length in Prenoceratops (Chinnery, 2004) versus 70% or less in the Black Creek form; in this respect the maxilla is more Some of these characters occur convergently in hadrosauroids similar to Euceratopsia (Wolfe et al., 2010). In lateral view, the and hadrosaurs. Hadrosaurs such as Hadrosaurus (Prieto-Marquez dentigerous process has a distinctly downturned end; the very end et al., 2006) have both an elongate dentigerous process and an of the dentigerous process is downturned by 25 relative to its extensive dorsal overlap of the maxilla by the ectopterygoid, and anterior end. This distinctive downturn is absent in other lep- alveolar slots. However, the jaw differs from hadrosaurs in many toceratopsids such as Prenoceratops (Chinnery, 2004) and Cerasi- respects. First, in hadrosaurs (Prieto-Marquez et al., 2006) and nops (Chinnery & Horner, 2007), where the ventral margin of the hadrosauroids (Prieto-Marquez, 2011) there is a prominent contact dentigerous process is straight in lateral view. for the jugal on the lateral surface of the maxilla, the jugal process, The posterior dentigerous process is bowed outward, such that just anterior to the dentigerous process. The Black Creek jaw lacks the toothrow is strongly curved in ventral view. This curvature is a any evidence for a jugal attachment, meaning that the jugal must derived feature seen in other Leptoceratopsidae such as Lep- have attached well above the toothrow, as in leptoceratopsids, toceratops and Prenoceratops, but it is not developed to the same protoceratopsids, and euceratopsians; furthermore the toothrow is degree as in the Black Creek ceratopsian (Fig. 3). In Leptoceratops strongly inset relative to the body of the maxilla, such that the jugal (Fig. 3)orPrenoceratops (Chinnery, 2004), the posterior dentigerous attachment would have been well lateral to the toothrow; again process makes an angle of approximately 13 with the teeth lying this is a ceratopsian feature, not seen in hadrosaurs. just ahead of the process, whereas this angle is 25 in the Black Second, in hadrosaurs (Prieto-Marquez et al., 2006) and Creek ceratopsian. hadrosauroids (Prieto-Marquez, 2011) the jugal is supported by a In addition to being diagnostic of the leptoceratopsids, the prominent ectopterygoid ridge, a derived feature of hadrosauroids; outward curvature of the toothrows indicates a proportionally no such ridge is present in the Black Creek jaw. short, broad skull that would have been triangular in dorsal view; Third, in hadrosaurids the ventral margin of the maxilla is N.R. Longrich / Cretaceous Research 57 (2016) 199e207 203

Fig. 4. A, NMC 8889, Leptoceratops gracilis; B1, divergent posterior dentigerous process of Leptoceratops; B2 posterior dentigerous process of Black Creek Ceratopsian YPM-PU 24964, showing the more highly divergent process versus Leptoceratops (dashed). straight in lateral view and weakly crenellated in ventral view due where prominent interdental ridges project down and in to wrap to reduction of the interdental ridges, a derived feature of the around the base of each tooth. group. By comparison, in the Black Creek jaw and leptoceratopsids Fourth, in hadrosaurids there are multiple replacement teeth, the maxilla is distinctly crenellated in lateral view and ventral view such that alveolar ridges form long, narrow slots for teeth (Horner

Fig. 5. A, AMNH 5205 Leptoceratops gracilis posterior dentigerous process (reversed for comparison) showing alveolar ridges and anteroposteriorly compressed tooth sockets. B, alveolar ridges of YPM-PU 24964. 204 N.R. Longrich / Cretaceous Research 57 (2016) 199e207 et al., 2004; Prieto-Marquez et al., 2006). Although small juveniles tyrannosaurs and hadrosaurs, the highly divergent morphology of have proportionately larger teeth and would have correspondingly the Black Creek ceratopsian supports the idea that eastern North wider, shorter alveolar slots, the teeth of comparably sized juvenile America was largely isolated from Laramidia throughout the hadrosauroids (Prieto-Marquez, 2011) are still more tightly packed Campanian and Maastrichtian. This idea is further supported by the than in the Black Creek jaw and would have narrower alveolar slots. fact that many of the groups that are shared by Laramidia and Asia Finally, no hadrosaur is known to show the strong lateral during the Campanian and Maastrichtian-including ceratopsids, deflection of the dentigerous process seen in leptoceratopsids. In pachycephalosaurs, thescelosaurs, lambeosaurs, saurolophines and summary, the jaw exhibits no derived features of Hadrosauridae ankylosaurids among the Ornithischia, and microraptorines, sau- that are not also seen in ceratopsians, and exhibits numerous rornitholestines, dromaeosaurines, caenagnathids, alvarezsaurids derived and primitive features that are seen in ceratopsians, but not and titanosaurs among the Saurischia (Weishampel et al., 2004)- hadrosaurs; the available evidence therefore rejects a hadrosaur are currently unknown from the fauna (Weishampel et al., 2004). identification. Furthermore, even taxa known from the mid- of Lar- The position of the Black Creek ceratopsian within the Leptocer- amidia, such as euceratopsians (Wolfe et al., 2010) and ther- atopsidae is unclear. It lacks the derived, proportionately short and izinosaurs (Kirkland & Wolfe, 2001) are unknown from Appalachia. deep maxilla that characterizes most leptoceratopsids. Assuming this Their absence would suggest that the physical isolation of Appa- is a plesiomorphy, then it may represent a relatively basal divergence. lachia and Laramidia had already occurred at this time. However, it is highly derived with respect to other leptoceratopsids in Sampling clearly remains an issue. Compared to the rich fauna terms of the shallow dentigerous process, the strong lateral curvature found in Laramidia, Appalachia's dinosaur fauna is known from a of the toothrow, and the strongly downturned dentigerous process; far more limited number of specimens, mostly from marine suggesting a high degree of specialization. depositional settings (Schwimmer, 1997). Yet while individual as- semblages are poorly sampled compared to Western North Amer- 3.2. Ecology and evolution ica, Late Cretaceous dinosaurs have been reported from localities in many Eastern states, including , Delaware, Maryland, The maxillae of the Black Creek ceratopsian are highly derived North and South Carolina, , Georgia, Alabama, Mis- relative to other Leptoceratopsidae in terms of the elongation of the sissippi, and Missouri (Fig. 6). Furthermore these strata range from posterior dentigerous process, the strong lateral deflection of the early to late Maastrichtian in age, spanning a period of dentigerous process, and the strong downturn of the process in approximately 20 million years (Schwimmer, 1997; Weishampel lateral view. These unusual specializations suggest adaptation for et al., 2004). an unusual diet and/or feeding strategy not seen in other lep- And while the associated remains are admittedly limited, iso- toceratopsids or other basal neoceratopsians. lated teeth and bones are typically diagnostic to family or subfamily Leptoceratopsids and other basal neoceratopsians have short, level; the existence of ceratopsids, ankylosaurs, or titanosaurs deep jaws that would be well-suited to shearing tough, fibrous could be confirmed by even a single tooth, bone, or . Further vegetation (Longrich, 2010), and Leptoceratopsidae in particular are collection and study could easily reveal previously unknown characterized by teeth with a unique combination of crushing and dinosaur lineages in Appalachia, but even so, over a century of shearing facets (Ostrom, 1966) and very short, deep, ‘nutcracker’ sampling from numerous localities, from New Jersey to Alabama, jaws (Brown, 1914; Chinnery, 2004; Chinnery & Horner, 2007; from the lower Santonian to the upper Maastrichtian, has consis- Kurzanov, 1992; Ryan et al., 2012) with the dentigerous process of tently painted a picture of a fauna dominated by hadrosaurines, the maxilla being correspondingly short and deep (Chinnery, 2004; tyrannosauroids, ornithomimosaurs, and nodosaursd one that is Chinnery & Horner, 2007). As the strength of a structure in bending low in diversity, even depauperate, relative to Laramidia. or shearing increases with depth (Gordon, 1978), this jaw structure Despite the absence of many characteristic Laramidian taxa, the suggests adaptation to produce high bite forces and process highly known vertebrate fauna of Appalachia is most similar to that of the resistant food items. Late Cretaceous of Laramidia. Taxa of fish (Grandstaff, Parris, The Black Creek ceratopsian departs markedly from this trend in Denton, & Gallagher, 1992), amphibians (Denton & O'Neill, 1998), having a relatively long, narrow dentigerous process, more like that reptiles (Denton & O'Neill, 1995; Grandstaff et al., 1992), and of a ceratopsid than a leptoceratopsid. Presumably, this feature mammals (Grandstaff et al., 1992) are all shared with Late Creta- represents an adaptation for processing less resistant food items. ceous faunas known from Western North America. Semiaquatic The odd down-and-out bend of the dentigerous process would reptiles such as the crocodilians Deinosuchus and and have altered the shape of the shearing blade formed by the teeth; it the Adocus (Grandstaff et al., 1992) may have been able to presumably represents a feeding specialization as well; although its swim across the , and small mammals, functional significance is less clear, it also suggests that the lizards and even frogs could conceivably have rafted. However, the had evolved a feeding strategy distinct from that of other fact that Laramidia and Appalachia share salt-intolerant aquatic leptoceratopsids. forms such as amiid fish and salamanders is strong evidence for an This divergent evolutionary path could result from the distinct ancient land connection between the two. Given this, most of the biota of the Appalachian province. Appalachia was part of a distinct Appalachian fauna can be interpreted as resulting from (i) dispersal palynofloral province, the Normapolles province (Srivastava, 1981) across the Western Interior seaway following isolation from Lar- and so the vegetation found there would have been distinct from amidia; (ii) a mid-Cretaceous land connection between Eastern and that seen in Laramidia. Perhaps more importantly, many of the Western North America, or (iii) a combination of these processes. herbivorous dinosaurs found in Laramidia were absent from How ceratopsians arrived in Appalachia (Fig. 1) remains unclear. Appalachia; the absence of competition may have allowed small Ceratopsian teeth are known from the Lower Cretaceous Arundel ceratopsians to exploit ecological niches and food items that would Formation of Maryland (Chinnery, Lipka, Kirkland, Parrish, & Brett- have been taken by other lineages of in Laramidia. Surman, 1998). However, the teeth are primitive compared to lep- toceratopsids; the teeth lack a strong offset of the primary ridge, 3.3. Appalachian biogeography whereas they are strongly offset in more derived forms such as leptoceratopsids, protoceratopsids, and euceratopsians; likewise Together with the basal phylogenetic position of the the central ridges extend only around halfway down the face of the N.R. Longrich / Cretaceous Research 57 (2016) 199e207 205

Fig. 6. Summary figure showing distribution of dinosaurs in Appalachia. 1, Missouri, Hadrosauridae; 2, Tennessee, Hadrosauridae; 3, Mississippi, Hadrosauridae, and Ornithimi- mosauria, 4, Alabama, Hadrosauridae, Ornithomimosauria, and ; 5, Georgia, Hadrosauridae, Tyrannosauroidea, and Ornithomimosauria; 6, South Carolina, Hadrosauridae, 7, North Carolina, Hadrosauridae, Tyrannosauroidea, and Lepticeratopsidae 8, Maryland, Hadrosauridae and Ornithomimosauria; 9, Delaware, Hadro- sauridae and Ornithomimosauria; Hadrosauridae and Ornithomimosauria, 10, New Jersey, Hadrosauridae, Tyrannosauroidea, Ornithomimosauria, Nodosauridae. Map after Schwimmer (Schwimmer, 1997) with data from Schwimmer (Schwimmer, 1997) and Weishampel et al. (Weishampel et al., 2004). The occurrences extend from the early Santonian to the late Maastrichtian, a period of around 20 million years.

crown or less, whereas the secondary ridges extend nearly to the Laramidia, Appalachia and Europe also share a number of taxa. cingulum in more derived forms. Given this, the Arundel ceratop- These include cimolomyid multituberculates (Grandstaff et al., sian does not appear to be closely related to the Black Creek form or 1992), nortedelphid marsupials (Martin, Case, Jagt, Schulp, & any other known Late Cretaceous ceratopsian. Mulder, 2005), and leptoceratopsids (Fig. 1), which are known Instead, the Black Creek ceratopsian is likely to represent a from the Late Cretaceous of Sweden (Lindgren et al., 2007). lineage that dispersed to Eastern North America. Conceivably, Furthermore, the neoceratopsian Craspedodon lonzeensis (Godefroit leptoceratopsids could have traversed a land bridge between & Lambert, 2007) appears to represent another European lep- western and eastern North America during the mid-Cretaceous, toceratopsid, as it shares an inset primary ridge with the lep- before Appalachia was fully isolated by the Western Interior toceratopsids, as well as an anteroposteriorly compressed, figure-8 Seaway. An alternative is that ceratopsians dispersed from Lar- shaped tooth root (seen also in the euceratopsian Turanoceratops amidia to Appalachia following the separation of the two via the (Sues & Averianov, 2009) but not in protoceratopsids or more Western Interior Seaway. Although it seems improbable that ani- primitive neoceratopsians). mals as large as ceratopsians could have colonized Appalachia via Thus, dispersal between Appalachia and Europe-with dinosaurs oceanic rafting, as large as iguanas are known to success- colonizing Europe from North America, or vice versa-is also fully cross oceanic barriers on floating vegetation (Censky, Hodge, & possible. If so, then a high-latitude land corridor connecting North Dudley, 1998) and juvenile ceratopsians would have been relatively America and Europe via Greenland, the Thulian route, may have small animals and could conceivably have rafted between the two been established towards the end of the Cretaceous. Leptocer- land masses. Furthermore, the dispersal of mammals from Africa to atopsids could conceivably have traveled via this route from Europe South America during the Cenozoic (Poux, Chevret, Huchon, De into Appalachia, rather than through Laramidia. New discoveries Jong, & Douzery, 2006) shows that trans-oceanic dispersal can from both eastern North America and western Europe will be and does occur in large terrestrial animals. needed to test these hypotheses and to better understand the Ap- Yet although the Appalachian fauna shows a strong affinity with palachian fauna and its origins. 206 N.R. Longrich / Cretaceous Research 57 (2016) 199e207

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