by Angela Matthias
A NEW BASAL HADROSAUR FROM THE LOWER CRETACEOUS
CEDAR MOUNTAIN FORMATION OF
David Gilpin and Tony DiCroce
A new hadrosaur from the Lower Cretaceous Yellow Cat Member of the Cedar Mountain Formation was discovered in May of 2001. This taxon is represented by a well-preserved left ilium, preacetabular process of the right ilium, right tibia, right metatarsal III, fused sacrum, ribs, and ossified tendons. The ilium overall resembles that of the iguanodontid Camptosaurus, but it has the lateral process (“antitrochanter”) that characterizes hadrosaurs. Plesiomorphic character of the elements suggests a recent departure from iguanodontids. We conclude therefore that this taxon represents a basal
hadrosaur.
A SAUROPOD FROM THE LOWER RUBY RANCH MEMBER OF THE CEDAR MOUNTAIN FORMATION OF
David Gilpin, Peggy LeMone and John Scandizzo
Sauropods from the Ruby Ranch Member of the Cedar Mountain Formation have only been known from the upper layers of this Member. In May of 1999 the remains of a sauropod from the lower portion of the Member was discovered. The bones of the animal were removed from the ground over a period of three visits to the site. Their identity was unknown at that time. Preparation, including assembly of surface scattered fragment s, however, has since revealed the specimen to be pelvic bones (two pubes and one ischium) of a sauropod Other bones consist of parts of long bones, ribs and other unidentifiable pieces. The ends of the pubes are missing, making it unlikely this dinosaur can be identified more specifically. The stratigraphic position of this animal, low in the Ruby Ranch and the other sauropod specimens high in the Member suggests that they were continuous members of the
A LARGE NODOSAURID ANKYLOSAUR FROM THE
CEDAR MOUNTAIN FORMATION OF
David Warren
Nodosaurs are well known from the Cretaceous of North America, with Sauropelta the best known Early Cretaceous form from the Cloverly Formation in
GASTROLITHS FROM THE LOWER CRETACEOUS SAUROPOD
CEDAROSAURUS WEISKOPFAE
A set of 115 clasts, ranging in size and mass from 0.04 cc to 270 cc and 0.1 gm to 715 gm, has been collected in association with a newly described brachiosaurid in the Cedar Mountain Formation, Cedarosaurus weiskopfi. The clasts were partially matrix-supported, and some were supported on-edge. There were a number of clast-to-clast and clast-to-bone contacts. The clast are most parsimoniously interpreted as gastroliths, making this the first set discovered in-situ in this formation. The gastrolith surfaces are mostly polished. Tight spatial distribution, partial matrix support, and some instances of on-edge orientation indicate that they were deposited while contained within carcass soft tissue. Low-energy depositional conditions and apparent initial containment within soft tissue indicate that the set is complete. Surface characteristics and distributions of shape, mass, volume, and composition have been determined. More than half of the clasts are less than 10 cc in volume. Drab colors indicate low selectivity by the sauropod for this characteristic. Most of the gastroliths are chert or quartzite, but some are sandstones and siltstones. High surface reflectance values of the majority of the gastroliths is consistent with the results of previous studies on other bona fide gastroliths.
Articulated Dermal Armor of the ankylosaur
Kathleen Brill
A large slab of articulated dermal armor of
The armor sheet was preserved with the external surface up. It was found in mudstone, which directly overlaid a hard concretion layer, approximately 20 to 30 cm thick, which encased the bones of
A poster describing the work thus far was presented at the 2004 Society of Vertebrate Paleonotology meeting in
CORTICATED PRESSURE EROSIONS, “PITTING”,
IN OSTEODERMAL ANKYLOSAUR ARMOR
The osteodermal armor of ankylosaurs often exhibits a pattern of depressions that are clearly not associated with taphonomic alteration. An investigation of this pathology was initiated using
A New Species of
from the Cedar Mountain Formation of
BILLY KINNEER
A mass graveyard of several disarticulated skeletons of a new species of the ankylosaur
To date over 3000 bones representing at least 20 individual animals have been collected and prepared from this monospecific ankylosaur bonebed. Over 75 skull fragments representing at least 9 individuals are available for study. Numerous fragments of scapula and armor, as well as other complete and fragmented post cranial bones, are available for comparison. The differences discovered in the examination of the features associated with the skull, scapula and amour strongly suggests that this is a new species of
The importance of this discovery further extends the support for ankylosaurs being present in
RECONSTRUCTION OF THE PELVIC AND HIND LIMB
MUSCULATURE IN THE ANKYLOSAUR
Tony DICROCE and Billy KINNEER
There have been many previous attempts to describe the ankylosaur pelvic musculature structure as a basis for explaining and understanding the evolution and development of its unusual ilium. All previous attempts have been incomplete; either important muscles were not fully considered or the skeletal elements were incomplete. None of the previous studies offered a convincing argument to explain the functionality of the ilium. Unlike most other attempts at reconstruction, this model shows the superficial and deep muscles in full-size three-dimension. A cast of an ankylosaur pelvic skeletal girdle was constructed from material recovered from an extensive burial of several individual animals, possibly a new species of
Additional studies with this model will be made to determine, what if any affect, dermal armor, locomotion, or diet had on the development of the anklyosaur pelvic structure. We anticipate this model will provide insight to the development and functionality of the ankylosaur ilium.
Evolutionary relationships of Early Cretaceous
Sauropod Faunas from the
Formation of
Virginia Tidwell
Although sauropod dinosaurs are well known from the Upper Jurassic Morrison Formation sediments found throughout the Western interior of the North America, until recently little was known about more recent, Cretaceous sauropods in the
The bones from these DMNS sauropod quarries in the CMF were brought to the museum for cleaning and repair. I have compared them with bones from the well known Late Jurassic sauropods Camarasaurus, Diplodocus and Brachiosaurus in order to determine to which group the new specimens are most closely related. Additional comparisons were made with another sauropod group known as titanosaurs, that, although poorly represented in North American sediments, are well known from other parts of the world. These comparisons required visiting museums housing major dinosaur collections in the
Partial skeletons from eight CMF localities have been identified to date. The results of these efforts so far suggest that one of these new CMF sauropods, Cedarosaurus weiskopfae (Tidwell et al 1999) resembles Brachiosaurus more than any other known sauropod, although differing in several important areas. Another new specimen, Venenosaurus dicrocei (Tidwell et al 2001), is a bit more like a titanosaur. One partial skeleton composed of several posterior cervical vertebrae from the Yellow Cat member of the CMF has tentatively been identified as a titanosaur due to the very low neural spines on all the elements, a titanosaur characteristic. Three partial skeletons from the Cedar Mountains Ruby Ranch member also appear to represent titanosaurs. The unexpected recovery of a sauropod forelimb from the base of the Dakota Formation suggests that titanosauriform sauropods were still present in the early Late Cretaceous, and represent the first verifiable sauropod specimen from the Dakota of Utah. Additional material from the Poison Strip and Yellow Cat member are still under study.
Worldwide significance of Early Cretaceous
Titanosauriform dinosaurs
Virginia Tidwell
In recent years new discoveries of titanosauriformes in North America, Europe and
The
Premilinary results suggest that the Long Walk specimen is more closely related to titanosaurs than to Brachiosaurus. This means that it is not the North American brachiosaur Cedarosaurus, nor Pelorosaurus, which is known from Wealden sediments in southern
