Hadrosaurus foulkii Leidy, 1858

Prieto-Márquez, Albert, 2011, Revised diagnoses of Hadrosaurus foulkii Leidy, 1858 (the type genus and species of Hadrosauridae Cope, 1869) and Claosaurus agilis Marsh, 1872 (Dinosauria: Ornithopoda) from the Late Cretaceous of North America, Zootaxa 2765 (1), pp. 61-68 : 65-67

Hadrosaurus foulkii Leidy, 1858

Fig. 3

Holotype. Single partial specimen consisting of fragmentary maxillary and dental elements, and various axial and appendicular bones, including: ANSP 9201 , various isolated maxillary and dentary teeth; ANSP 9202 , dental battery fragments; ANSP 9203 , a left rostroventral maxillary fragment; ANSP 9204 , a lateral portion of the ectopterygoid shelf of a fragmentary left maxilla; and ANSP 10005 , a partial postcranium consisting of three partial cranial dorsal vertebrae, three proximal caudal centra, nine proximal to middle caudal centrum, including an almost complete middle caudal vertebra, and numerous vertebral fragments, a partial right coracoid, left humerus, left radius, left ulna, left ilium, right ischium, right partial pubis, and a partial left hind limb represented by a femur, tibia, nearly complete fibula, metatarsals II and IV, and pedal phalanx III–1.

Type locality and horizon. The holotype and only known materials of Hadrosaurus foulkii were collected in Haddonfield , New Jersey, eastern United States of America, from Campanian (Upper Cretaceous) strata corresponding to the Woodbury Formation ( Prieto-Márquez et al. 2006) .

Diagnosis. Basal hadrosaurid dinosaur characterized by the unique combination of the following plesiomorphic humeral and derived iliac characters within the context of Hadrosauroidea as defined by Prieto-Márquez (2010): very short pectoral crest, being only slightly over 40 per cent of the total length of the humerus; deltopectoral crest expanding smoothly from the humeral shaft, so that its laterodistal corner displays a wide and arcuate profile; ventral apex of supraacetabular crest located above the posteroventral corner of lateral ridge on posterior tuberosity of ischial peduncle of ilium; anteroposteriorly shortened supraacetabular crest, its breadth being half the length of central iliac plate.

Remarks. Being only 42 per cent of the total length of the humerus, the proximodistal length of the deltopectoral crest in Hadrosaurus foulkii is the shortest among adult (or at least relatively large) hadrosauroid humeri (Prieto- Márquez unpublished data), and comparable to that in non-hadrosauroid iguanodontians such as Mantellisaurus atherfieldensis (e.g., NHMUK 11521; Fig. 3 ). Within the context of hadrosauroids (according to the phylogeny by Prieto-Márquez 2010), this short deltopectoral crest, with its wide arcuate laterodistal corner, is plesiomorphic ( Table 1). In contrast, the limited anteroposterior width of the supraacetabular crest in H. foulkii is a derived condition within that context. Notably, the ventral apex of this crest lies above the posteroventral end of the ischial peduncle. To my knowledge, aside from H. foulkii , this condition is only present in the basal hadrosauroid Tanius sinensis (e.g., PMU R242).

Nomenclatural note. Clade names and phylogenetic definitions used in this study follow Sereno (2005) and the revision of hadrosaurid interrelationships by Prieto-Márquez (2010). Accordingly, Iguanodontia consists of the most inclusive clade containing Parasaurolophus walkeri but not Hypsilophodon foxii and Thescelosaurus neglectus . Within iguanodontians, Hadrosauroidea consists of Hadrosaurus foulkii and all taxa more closely related to it than to Iguanodon bernissartensis , including Hadrosaurinae (represented solely by Hadrosaurus ) and Saurolophidae . Likewise, Hadrosauridae is the clade stemming from the most recent common ancestor of H. foulkii and P. walkeri . Saurolophidae is defined as the last common ancestor of Saurolophus osborni , Lambeosaurus lambei , and all its descendants, which include the two major hadrosaurid clades: Saurolophinae and Lambeosaurinae.

I followed Horner et al. (2004) in using the term “supraacetabular” to designate the crest-like process that extends lateroventrally from the dorsal margin of the central plate of the ilium. The term is anatomically accurate, since the structure is located above (i.e., “supra”) to the acetabulum. Likewise, I used “crest” rather than “process” to refer to this structure because the former more accurately describes the morphology of this structure.

Figures

FIGURE 3. Distribution, in a phylogenetic context, of the relative length and profile of the laterodistal corner of the deltopectoral crest of the humerus, and the anteroposterior width of the supraacetabular crest and position of its apex relative to the ischial peduncle of the ilium in Hadrosaurus foulkii and selected major groups of iguanodontian dinosaurs. The cladogram has been simplified from the strict reduced consensus tree presented by Prieto-Márquez (2010). From left to right, specimens used as clade or taxon representatives are as follows. Non-hadrosauroid Iguanodontia: skull of Iguanodon bernissartensis (IRSNB 1731), and right humerus (NHMUK R6616; reversed) and left ilium (NHMUK 11521) of Mantellisaurus atherfieldensis. Nonhadrosaurid Hadrosauroidea: skull of Equijubus normani (IVPP V12534), and right humerus (AMNH 30728; reversed) and right ilium (AMNH 30735; reversed) of Gilmoreosaurus mongoliensis. Hadrosaurus foulkii: line drawing of the historical skull model sculpted by Waterhouse Hawkins, and left humerus and left ilium of ANSP 10005. Saurolophinae: skull of Edmontosaurus annectens (SM R4036) and left humerus of Gryposaurus latidens (AMNH 5465). Lambeosaurinae: skull of Parasaurolophus walkeri (ROM 768) and left humerus of P. cyrtocristatus (FMNH P27393). The right ilium (reversed) representing both saurolophines and lambeosaurines (i.e., Saurolophidae) is that of Brachylophosaurus canadensis (MOR 794). Skulls and ilia are shown in left lateral view; humeri are displayed in anteromedial view.