Dryptosaurus aquilunguis Cope, 1866

Brusatte, Stephen L., Benson, Roger B. J. & Norell, Mark A., 2011, The Anatomy of Dryptosaurus aquilunguis (Dinosauria: Theropoda) and a Review of Its Tyrannosauroid Affinities, American Museum Novitates 2011 (3717), pp. 1-56 : 5-6

Dryptosaurus aquilunguis Cope, 1866

HOLOTYPE: ANSP 9995 . Fragmentary skeleton found associated and belonging to a single individual, including a fragment of the right maxilla, a fragment of the right dentary, a fragment of the right surangular, lateral teeth, 11 middle-distal caudal vertebrae, left and right humeri, three manual phalanges from the left hand (I-1, II-2, and an ungual), shafts of the left and right pubes, a fragment of the right ischium, left femur, left tibia, left fibula, left astragalus, midshaft fragment of metatarsal III. The neurocentral sutures are closed in all caudal vertebrae, suggesting that the holotype individual was mature or nearing maturity.

ADDITIONAL MATERIAL: AMNH FARB 2438 . Left metatarsal IV, likely from the same individual as the holotype (see Carpenter et al., 1997) .

CAST MATERIAL: Well-preserved , historic casts of most of the holotype, including AMNH FARB 2438 , are present in the collections of the Natural History Museum in London (NHM OR50100). In some cases the casts show detail that is no longer preserved on the original specimens .

TYPE LOCALITY: West Jersey Marl Company Pit, near Barnsboro, Gloucester County, New Jersey. The Dryptosaurus holotype was discovered in 1866 in a unit comprised of marl and sandstone, which was defined nearly a century later as the New Egypt Formation, regarded as Maastrichtian in age ( Olsson, 1960). The New Egypt Formation is a marine unit, comprised of claystone, sandstone, and marls, with frequent glauconitic and sideritic nodules ( Olsson, 1963). It is up to 10.5 m thick in its type area, along Crosswicks Creek, but thins to the south, such that it is considerably thinner at the Dryptosaurus holotype locality ( Landman et al., 2004). The New Egypt Formation conformably overlies the Navesink Formation, from which potential Dryptosaurus referred material has been reported, and is considered to be a deeper-water equivalent of the Tinton and Red Bank formations ( Olsson, 1987). See Gallagher (1993) and Landman et al. (2004) for a more detailed description of the stratigraphy of Late Cretaceous units in New Jersey.

DIAGNOSIS: A tyrannosauroid theropod possessing the following autapomorphies: combination of a reduced humerus (humerus: femur ratio = 0.375) and a large hand (phalanx I-1: femur ratio = 0.200) (see text for numerical comparisons to other tyrannosauroids); strong mediolateral expansion of the ischial tubercle, which is approximately 1.7 times as wide as the shaft immediately distally; an ovoid fossa on the medial surface of the femoral shaft immediately proximal to the medial condyle, demarcated anteriorly by the mesiodistal crest and medially by a novel crest; proximomedially trending ridge on the anterior surface of the fibula immediately proximal to the iliofibularis tubercle; lip on lateral surface of lateral condyle of astragalus prominent and overlapping the proximal surface of the calcaneum; metatarsal IV with a flat shaft proximally, resulting in a semiovoid cross section that is much wider mediolaterally than long anteroposteriorly.

NOMENCLATURAL NOTE: In this paper we employ the clade names Tyrannosauroidea and Tyrannosauridae following the definitions of Sereno et al. (2005). Tyrannosauroidea is the most inclusive clade that contains Tyrannosaurus rex but not other coelurosaurs ( Ornithomimus edmontonicus, Troodon formosus, Velociraptor mongoliensis). Tyrannosauridae is a less inclusive clade, defined as the least inclusive clade containing Tyrannosaurus rex and Gorgosaurus libratus . Therefore, Tyrannosauroidea is a larger group that includes Tyrannosauridae , as well as an array of taxa on the stem toward Tyrannosauridae , including Guanlong , Proceratosaurus , Sinotyrannus , Dilong , Eotyrannus , Stokesosaurus , Xiongguanlong , Raptorex , Bistahieversor , Appalachiosaurus , Dryptosaurus (following the phylogeny of Brusatte et al., 2009, 2010). Tyrannosauridae , on the other hand, is a less inclusive group of derived tyrannosauroids that includes Albertosaurus , Alioramus , Daspletosaurus , Gorgosaurus , Tarbosaurus , and Tyrannosaurus .

One further matter deserves comment. Dryptosaurus is included with Tyrannosauroidea, and is also the type genus for a family-level taxon, Dryptosauridae ( Marsh, 1890) . Dryptosauridae , in fact, was named 15 years prior to Osborn’s (1905) establishment of Tyrannosauridae , and therefore has priority at all family levels by the International Code of Zoological Nomenclature Principle of Coordination, which deems all family group taxa (superfamilies, families, subfamilies, etc.) to be established upon the first use of any family group name. Thus, it may be expected that Tyrannosauroidea should be renamed using Dryptosaurus as an eponym. However, Article 35.5 of the Code allows for names in prevailing usage at higher rank, such as Tyrannosauroidea, to be retained in cases such as these, because a superfamily name based on Dryptosaurus has never (to our knowledge) been used in the literature, whereas Tyrannosauroidea is commonly used and has been for many years. A similar nomenclatural situation was recently confronted by Kammerer and Angielczyk (2009), who also invoked Article 35.5 to retain a commonly used superfamily name despite an older name being available under the Principle of Coordination.