The vertebral column is intact and articulated from the anterior dorsal region to very near the tip of the tail. A short distance at either end of the center, viewed laterally, is the surface. They are relatively long in the anterior dorsal region (see Fig. 3) with a capitular facet on the arch side.
Posteriorly, the transverse processes become shorter and the position of the facet changes from the side of the arch to the front. This second sacral has the smallest center of the five and is subcircular in diameter. All are given off from the side of the centers immediately below the level of the neuro-central suture (fig. 6).
With the disappearance of the transverse processes, the length of the centers increases rapidly and they remain. It is of the same size as the distal parts of the humerus belonging to the type, and on the whole. The distal end was opposed by ulnar and intermedimn elements of the carpus, as well shown in the articulated limb (Fig. 11).
The greatest length of the left ulna is 154 mm., the width of the proximal end 42 mm., and the width of the distal end 32 mm.
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There is a well-developed lesser trochanter on the anterior external corner of the proximal end, which is separated from the upper part of the shaft by a deep vertical fissure. As with the humerus, the shaft of the femur is twisted, due to the change of the aspects of its surfaces. It starts above but extends below the midline of the shaft, as in Camptosaurus.
The proximal end is divided into two condyles that project posteriorly and are separated by an intercondylar groove. A well-developed prenemial crest projects from the upper part of the shaft in front of the internal condyle. The flattened surfaces on the underside of the bone were in contact with the distal ends of the fibula.
It has a flattened shaft, above which it becomes subcindrical, below with a flattened posterior surface that abuts the opposite surface of the tibia (Fig. 14). Canis.—There are four functional digits and one (heel) in the canine of Thescelosaurus. A previous description of this animal stated: "There are four toes in the hind foot, metatarsal I is reduced."
It is an advance in the specialization of the tarsus above either ear. The proximal ends of the three middle metatarsals are in the closest position, their axes are closely related to each other for more than haK their lengths. The proximal and distal ends of metatarsals II, III and IV are robust, with deep pits for the attachment of the lateral ligaments.
The first is about half a third as long, and the fifth less than one fourth the length of the same element. It articulates rather loosely with metatarsal II and lies in a shallow depression on the inner proximal side of this metatarsal, as shown in Figures 14 and 15.
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The pelvic arch is sufficiently diagnostic of the genus to immediately distinguish Thescelosaurus from all other known dinosaurs. Both ilia are present, but only the right one is available for examination and part of its posterior end is missing, as shown in Figure 17. On the inside behind the acetabulum is a relatively thin but wide bone plate. Fig. 17) is perpendicular to the main part of the ihum and extends inwards, hinged by sutures along the inner edge with the ribs of the two posterior sacral vertebrae.
The type specimen lacks the distal extremities of the postpubis, but an impression of these bones in the matrix shows their exact length and also gives a good idea of their size and rounded shape, as shown in Fig. 17. The anterior articulating with the pubis and the heavier one meeting the sessile petiole. ihum is shown in Fig. 17. The upper concave border between these two processes forms the greater part of the lower border.
The inner borders of the lower third of the ischia were in contact, as shown in the cardiac pelvis and also of the ischium of the American Museum speci-. The tubercular branch is reduced to amer tubercle located on the upper border where the long main branch joins the shaft of the rib (Fig. 18). Preservation of epidermis. - External to the ribs and behind the blade of the scapula on the left side, a small dark area was found, which is believed to represent a portion of the charred epidermis of the animal.
When the skeleton was discovered, the skull, neck and parts of the pectoral arch had eroded away, but it seems most likely that all the bisected parts were present when the animal was. The right hind leg, when found, was disarticulated at the hip and extended beyond the sacrum perpendicular to the longer axis of the skeleton. It was thought expedient to articulate this leg correctly, and this has been done, as shown in Plate 79, the original angulation of limb and foot preserved undisturbed.
A few missing parts, such as the ends of the ribs, limbs, and pelvic bones, and parts of a few vertebrae, have been restored, and following the usual procedure, these restored parts are painted with a bright color so that they can be easily distinguished from the fossil parts. The position of the skeleton is that of an animal that died of natural causes, as the skeleton was not dismembered by prey. The expanded ribs indicate rapid filling of the thoracic cavity after death, and this rapid covering of the entire skeleton would undoubtedly have contributed to the excellent preservation of the specimen.
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613 Under the above definition were included the genera Nanosaurus, Under the above definition were included the genera Nanosaurus, Laosaurus and Dryosaurus from America and Hypsilophodon from the Wealden of the Isle of Wight. Apparently it is abrasive that the premaxillaries are described as having no teeth, because they were certainly present in the premaxillaries. 1) Niobrara County, Wyoming; (2) Deer Ears Buttes, South Dakota; (3) HellCreek, in Montana. Whether Thescelosaurus will be found to have teeth in pre-maxiUariesis has yet to be determined.
The presence in Thescelosaurus of single-headed posterior thoracic ribs and four phalanges on digit III of the forefoot are structural features sufficient to separate it from all known dinosaurian genera, with the exception of Hypsiloj^Jiodon, and I will therefore assign. For obvious reasons, the genera Nanosaurus, Laosaurus and Dryosaurus should be removed to the family Laosauridae. The genus Tliescelosaurus can be distinguished from Hypsilophodon by the greater length of the femur over the tibia and by the position of the fourth trochanter below the middle of the femur, while Hypsilophodonthistrochanter is entirely on the proximal half of that bone.
615 Currently, the fossil remains of Thescelosaurus are known. These are the Niobrara County area in Wyoming, Deer Ears Buttes in South Dakota^.
RESTORATIONS OF THESCELOSAURUS
EXPLANATION OF PLATES
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