Ornithotarsus immanis Cope, 1869

Prieto-Márquez, Albert, Weishampel, David B. & Horner, John R., 2006, The dinosaur Hadrosaurus foulkii, from the Campanian of the East Coast of North America, with a reevaluation of the genus, Acta Palaeontologica Polonica 51 (1), pp. 77-98 : 91

Ornithotarsus immanis Cope, 1869 .

Holotype: YPM 3221 , consisting of the articulated left distal tibia, astragalus, calcaneum, and distal fibula fragment.

Type locality and horizon: Although Colbert (1948) pointed out that the stratigraphic position of this taxon is unclear (questionably assigning it to the Campanian Woodbury Formation), both Cope (1869) and Lull and Wright (1942) stated that the bones were discovered in the shores of Raritan Bay (2.5 miles East of Keyport, Monmouth County, New Jersey), from clays belonging to the Lower Cretaceous. No further details were given as to where within the Lower Cretaceous the bones came from.

Comments.—We agree with Lull and Wright (1942) and Colbert (1948) concerning the lack of diagnostic features in YPM 322. However, we could not locate the proximal phalanx mentioned by Lull and Wright (1942) as assigned to the same taxon. As in all hadrosaurids, the astragalus has a triangular ascending process with a concave cranial surface close to the lateral joint with the calcaneum ( Fig. 6A 1, A 2). At its medial edge, the caudal side is as proximodistally tall as the ascending process of the astragalus and slopes lateroventrally until it contacts the calcaneum. The distal surface is saddle−shaped and the bone is twice as long mediolaterally as it is wide craniocaudally. In distal view, the astragalus of YPM 3221 is narrower craniocaudally at the medial side than in B. canadensis ( MOR 794). The co−ossified calcaneum is crescentic and compact, as in all hadrosaurids. The lateral face is flattened, the distal and caudal surfaces describe a 90−degree convexity, and the bone is proximodistally shorter at the medial articular edge. The proximal surface is convex and split in two parts by a sharp diagonal ridge. The distal fragment of the tibia is non−diagnostic beyond the level of Hadrosauridae , being triangular in both cranial and distal views, and compressed craniocaudally ( Fig. 7B ). The cranial region has a striated central recess for receiving the ascending process of the astragalus. Lateral to this recess the distal end of the tibia is further expanded distally relative to the medial side. Caudally, there are two flat surfaces; the more extensive one faces caudolaterally and the other caudomedially. As in all hadrosaurid fibulae, YPM 3221 is distally expanded, approximately twice as wide craniocaudally as it is wide mediolaterally ( Fig. 6A 4 ). The craniolateral distal end is thickened. The medial surface is flat. Lull and Wright (1942) discussed a metatarsal III ( ANSP 8596) from marine strata at Merchantville, New Jersey, which they consider comparable to YPM 3221 in size. The bone lacks the ventral half of the proximal region. The element is dorsoventrally compressed (in part due to taphonomic processes), subrectangular, and craniocaudally elongated. The proximal surface is dorsally convex and the distal surface is rectangular in distal profile. The medial ridge gives a smooth convexity to the medial profile of the bone in dorsal view.

Conclusion.— O. immanis is a nomen dubium due to the lack of distinguishing characters and it is referrable to Hadrosauridae indeterminate.

Figures

Fig. 7. Relationship between two ratios in the pubis of several hadrosaurid dinosaurs. P, total length of the pubis, from the acetabular edge to the cranial edge of the prepubic process; p, length of the proximal constriction of the prepubic process, from the iliac peduncle to the most proximal and highest point of the dorsal border of the pubic blade; w, minimum breadth of the proximal constriction of the prepubic process; and B, maximum breadth of the pubic blade between the end of “p” and the ventral end of a perpendicular line taken from the end of “p”. The star symbol represents Hadrosaurus minor (ANSP 15202). Letters within squares represent the following taxa: B = Brachylophosaurus canadensis; C = Corythosaurus casuarius; E = Edmontosaurus annectens; E’= E. regalis; H = Hypacrosaurus altispinus; H’= H. stebingeri; K = Kritosaurus latidens; M = Maiasaura peeblesorum; P = Prosaurolophus blackfeetensis; S = Saurolophus osborni.

Fig. 4. Hadrosaurus foulkii Leidy, 1858 (ANSP 10005), Haddonfield, New Jersey, U.S.A., Woodbury Formation, Campanian, Upper Cretaceous. A. Left femur in caudal view. B. Left tibia in cranial view. C. Left fibula in lateral view. D. Left metatarsal IV in dorsal (D1) and lateral (D2) views. E. Left metatarsal II in dorsal (E1) and medial (E2) views.