134
Journal of Paleontology 90(1):133–146
Figure 1. Location of the Careless Creek Quarry (CCQ) in Wheatland County, south-central Montana, USA.
the characters supporting such taxonomic identities warranted a revision of the CCQ hadrosaurid material. With the goal of addressing those shortcomings, the ske-
letal morphology of the hadrosaurid material from CCQ is described and figured for the first time, and its phylogenetic relationships are inferred via maximum parsimony analysis. We accompany this study with a number of comparative anatomical observations on ontogenetic variation of cranial and appendi- cular elements of the hadrosaurid skeleton using CCQ juvenile material. Based on the maximum number of specimens of the same side for the most abundant skeletal elements under consideration, a minimum of five individuals are represented in our study sample. This minimum number of five individuals comes from counting at least one juvenile, one large subadult or adult lambeosaurine (given by a single ischium), and at least three large subadult or adult saurolophines (given by three right pubes).
Materials
Repositories and institutional abbreviations.—AMNH, Amer- ican Museum of Natural History (FABR, Fossil Amphibians, Birds, and Reptiles collection), New York City, New York, USA; ANSP, Academy of Natural Sciences of Philadelphia, Philadelphia, USA; CMN, Canadian Museum of Nature, Ottawa, Ontario, Canada; MOR, Museum of the Rockies, Bozeman, Montana, USA; ROM, Royal Ontario Museum, Toronto, Ontario, Canada; TMP, Royal Tyrrell Museum of Paleontology, Drumheller, Alberta, Canada.
Systematic paleontology
Superorder Dinosauria Owen, 1842 Order Ornithischia Seeley, 1887 Suborder Ornithopoda Marsh, 1881 Family Hadrosauridae Cope, 1870 Hadrosaurid indeterminate Figures 2, 3
Referred material.—ANSP 15979, a juvenile specimen including cast of left humerus, left scapula, and left tibia; ANSP 15986, cast of partial juvenile right humerus; ANSP 16242, partial juvenile left dentary; ANSP 18325, partial fused basi- sphenoid, parasphenoid, and presphenoid; ANSP 17671, partial left dentary; ANSP 17689, partial pterygoid; ANSP 18326, fragmentary maxilla; ANSP 17690, fragmentary opisthotic- exoccipital; ANSP 18322, partial left surangular; ANSP 17728, sacrum; and ANSP 16957–16961, pedal phalanges (Table 1).
Skull elements.—One of the only two neurocranial fragments represented in the CCQ sample, ANSP 18325, preserves most of the parasphenoid and the rostroventral extent of the basisphenoid including the right pterygoid process (Fig. 2.1, 2.2). The thick cultriform process of the parasphenoid is slightly expanded both proximally and distally. Dorsally, it is fused to the presphenoid, forming a gently concave wall. Proximally, the parasphenoid is continuouswith the basisphenoid. The stout basipterygoid process projects caudolaterally and ventrally, forming a 150° angle (as measured in ventral view) with the long axis of the cultriform process of the parasphenoid. A ventromedian process was prob- ably present, judging fromthe erodedmedian prominence seen in between the bases of the pterygoid processes. The second hadrosaurid neurocranial remain consists of a
partial opisthotic-exoccipital complex (ANSP 17695; Fig. 2.3). The element preserves the proximal extent of the opitshotic- exoccipital complex. It corresponds to the lateral surface of the caudal region of the braincase, caudal to the prootic, dorsal to the basioccipital, and ventral to the parietal. The bone projects caudodorsally and displays a prominent longitudinal crista otosphenoidalis. Proximoventrally, below that ridge, the element is rostrocaudally expanded, containing the metotic foramen rostrally and the exit for branches of cranial nerve 12 caudally. The maxilla is solely represented by ANSP 18327, a
fragment of the lateral wall of this facial element (Fig. 2.4). The bone preserves most of the ectopterygoid ridge and part of the lateral and rostral-most extent of the ectopterygoid shelf, as well
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