ParsonsAbstracts

Conference abstracts

2009 Society of Vertebrate Paleontology Annual Conference Abstract

Abstract Number: 37AN UNUSUAL NEW MAMMAL FROM THE LOWER CRETACEOUS CLOVERLY
FORMATION OF CENTRAL MONTANA

PARSONS, William, Buffalo Museum of Science, Buffalo, NY, USA;
PARSONS, Kristen,Buffalo Museum of Science, Buffalo, NY, USA

The remains of at least two individuals from a new mammalian taxon were discovered within the basal portion of Unit VII of the Cloverly Formation of Montana. Preliminary phylogenetic analysis indicates that it occupies a basal position among Mammaliaformes, but further work is needed to more precisely elucidate placement of this new taxon. The material represents a mammal that is approximately 20 to 30 percent larger than the extant Short-beaked Echidna (Tachyglossus aculeatus). Both cranial and postcranial material has been recovered. The skull is represented by much of the roof of the braincase, maxillae, an incomplete jugal, a portion of the basicranium, and complete mandible. The teeth exhibit polyphyodont replacement, with new teeth erupting behind the older teeth in both the dentary and maxilla. There is no canine, but there appears to be a large caniniform incisor. The molariform teeth have unusual crown configuration, with vertical enamel-covered walls surrounding deep basins. These walls comprise a number of both large and small cuspules. The postcranial material includes the ilia, several centra and isolated neural arches, partial humerus, proximal end of the radius, several manual elements, rib fragments, fragments of the femur, complete tibia, possible fibula, articulated calcaneum and astragalus (collected as a block), an isolated astragulus, and numerous pedal bones. The manual unguals are dorsoventrally flattened, and all the manus elements closely resemble those of the echidna, suggesting similar fossorial behavior. The manual elements are at least twice the size of the pedal elements. The transverse processes of the sacral vertebrae are not fused to the ilia, but contact them in a “ball and socket” articulation. A small block of possible gut contents containing two small teeth and bone fragments has also been recovered.

DIFFERENTIATING BETWEEN SAUROPELTA EDWARDSORUM (ORNITHISCHIA, THYREOPHORA) AND A NEW ANKYLOSAURID, BOTH FROM THE EARLY CRETACEOUS CLOVERLY FORMATION OF CENTRAL MONTANA

PARSONS, William, Buffalo Museum of Science, Buffalo, NY, USA;
PARSONS, Kristen,Buffalo Museum of Science, Buffalo, NY, USA

This current analysis of a newly discovered dinosaur has resulted in its recognition as the second ankylosaur, and the first member of Ankylosauridae, to be recovered from the Early Cretaceous Cloverly Formation of central Montana. The initial determination that it was in fact a new taxon resulted from a differential comparison between the cranial elements of this new taxon and the cranial elements of the nodosaurid Sauropelta edwardsorum, the only other ankylosaur from the Cloverly Formation. Here we present the detailed character comparisons that differentiate this new taxon from Sauropelta. Although only a few fragmentary cranial elements of Sauropelta have thus far been recovered, their comparison with the cranial material of this new taxon has revealed several distinctly contrasting
features. The differentiating characters in this new taxon include a frontoparietal dome, an expanded nuchal ridge that obscures the occipital region, a circular orbit, ventral curvature in the caudolaterally directed paroccipital processes, a caudoventrally directed foramen magnum, a comparison between the relative proportions of the basipterygoid processes and the basal tubera, and a number of features of the braincase. Another consequence of
this comparative study has been a more detailed examination of the cranial characters of Sauropelta. This has contributed some newly coded characters for Sauropelta, as well as some editing of the coding of previously known characters. Further analysis of all these features presents some clues as to the earlier stages within the evolutionary development of what would become the more extravagant cranial characters possessed by later members of Ankylosauridae. Some interpretative speculations regarding the function of the few key unambiguous synapomorphies that define the two major clades within Ankylosauria suggest possible differing behaviors that may have led to the development of these two clades.

2007 Society of Vertebrate Paleontology Annual Conference Abstract
 

GUT CONTENTS OF A LOWER CRETACEOUS DROMAEOSAURID DINOSAUR: NEW DATA ON THE FEEDING BEHAVIOR OF DEINONYCHUS ANTIRRHOPUS (SAURISCHIA, THEROPODA).

PARSONS, William L., Research Associate, Department of Geology, Buffalo Museum of Science, Humboldt Parkway, Buffalo, NY, 14211
PARSONS, Kristen M., Research Associate, Department of Geology, Buffalo Museum of Science, Humboldt Parkway, Buffalo, NY 14211

   Two partial specimens of Deinonychus antirrhopus, from the Lower Cretaceous Cloverly Formation of central Montana, discovered within a mono-specific site, were found to be closely associated with preserved gut contents. The gut contents consisted of several small nodules composed of densely packed bone fragments. Many of the bone fragments that appear upon the surface of these nodules exhibit erosion of the outer periosteal layers and acid-etching, which are indications of the digestive process. The acid etching is similar to the result of the action of digestive acids and enzymes found within the gut contents of modern amniotes. Although no gastroliths are present at this site, the highly fragmented nature of some of the bones in this gut material may indicate digestive processing by a muscular gizzard. Color differences between gut content material and associated bone have been noted in the descriptions of other fossil gut contents. Almost all of this gut content material is a deep shade of orange and can be easily distinguished from the pinkish-green/grey coloration of the associated Deinonychus bone material. Although some of the larger bone fragments within these conglomerates were of the size that would be expected from the remains of a medium-sized dinosaur, many fragments are from much smaller individuals. An avian-like manual phalanx found among these conglomerates indicates the original source of at least some of the smaller bones. The morphology of this phalanx indicates a forelimb/wing from a taxon that is very likely to have been capable of sustaining some form of flight. Although the discovery of this forelimb element is notable, it is also significant in that it indicates that Deinonychus not only fed upon the carcasses of larger dinosaurs, but that its predatory behavior included the acquisition of much smaller prey. Deinonychus was an opportunistic feeder, probably capable of catching prey species that possessed some form of flight.

2006 Society of Vertebrate Paleontology Annual Conference Abstract

MORPHOLOGY AND SIZE OF AN ADULT SPECIMEN OF DEINONYCHUS ANTIRRHOPUS (SAURISCHIA, THEROPODA)

PARSONS, William L., Research Associate, Department of Geology, Buffalo Museum of Science, Humboldt Parkway, Buffalo, NY, 14211
PARSONS, Kristen M., Research Associate, Department of Geology, Buffalo Museum of  Science, Humboldt Parkway, Buffalo, NY 14211

Since the original description of Deinonychus there has been a certain amount of speculation relating to the various ages of all the known specimens of this taxon. This determination of the actual size and morphology of adult forms of Deinonychus provides new data that are essential to any further studies of the ontogenetic morphological differences within the known specimens of Deinonychus. Presented here is a newly discovered specimen, MOR 1182, that has been determined to be an adult, based on the presence of peripheral rest lines that were revealed in the thin section analysis of a fragment of the radius. These peripheral rest lines indicate determinate growth, which adds yet another avian character to the description of this taxon. Lines of arrested growth observed on a manual phalanx indicate the approximate age of this specimen. A comparison of the number of these LAGs with those observed on the sub-adult specimen MOR 1178 indicates the approximate age of initial maturity. Comparisons between the skeletal elements of MOR 1182, MCZ 4371 and AMNH 3015 reveal enough data to make some descriptive statements regarding the morphology of the adult forms of Deinonychus. Some of the proportional ratios between the elements of the forelimbs and hind limbs can be further defined. The range in size between the onset of sexual maturity and full physical maturity can be estimated. Also, portions of the tail structure of the specimen, MOR 1182, have been preserved. Analysis of these elements indicates that the adult caudal rods possessed a surprising degree of flexibility. This new fossil material raises questions about the nature of these caudal rods, the associated soft tissue and the manner in which they relate to the caudal vertebrae.  Morphological differences between some adult and sub-adult manus and pes elements may indicate differences in behavior between adults and sub-adults. Also, other associated faunal remains may indicate a greater variety of smaller prey species.

2005 Conference Presentation: Society of Vertebrate Paleontology Annual Conference

A COMPARISON OF SOME OF THE IMPORTANT POSTCRANIAL FEATURES FOUND WITHIN THE ONTOGENIES OF DEINONYCHUS ANTIRRHOPUS, (SAURISCHIA, THEROPODA) AND VELOCIRAPTOR MONGOLIENSIS (SAURISCHIA, THEROPODA)

PARSONS, William L., Research Associate at Museum of the Rockies; 1621 Olean Rd., South Wales, NY 14139 and PARSONS, Kristen M., Research Associate at the Museum of the Rockies; 1621 Olean Rd., South Wales, NY 14139

Expanding upon the preliminary analysis of the ontogenetic characters originally observed within the examination of the two sub-adult specimens of <i>Deinonychus antirrhopus, <i/> MOR 1178 and MCZ 8791, a study of the juvenile dromaeosaurid specimen <i>Velociraptor mongoliensis<i/> IGM 100/985 and a comparison of this specimen with more mature specimens of <i>V. mongoliensis<i/> have revealed some strong morphological similarities to that of the <i>D. antirrhopus<i/>sub-adults, as well as some unique differences. By using the length of the pes I-1 as an index for constructing comparative ratios within all available specimens, an analysis of the available forelimb elements, manus I-2, manus II-3 and a partial humerus of the juvenile specimen of <i>V. mongoliensis,<i/> indicates that sub-adult members of the genus Velociraptor possessed extremely elongate forelimbs that are similar in proportion to those observed on the two sub-adult specimens of <i>D. antirrhopus <i/>.  A landmark shape graphing procedure was used to define key diagnostic points within the available morphology of two partial humeri belonging to the <i> V. mongoliensis</> specimens IGM 100/982 and IGM 100/985.  This made accessible internal ratios that helped to strengthen the determination of the elongate nature of the juvenile forelimbs. The analysis of these adult and juvenile specimens has brought to light certain characters that may be diagnostic of the juvenile status of other individual specimens within these genera. Also, more detailed examinations of some skeletal elements have brought out differences such as those found on the laterally compressed unguals, the curvature of the third metacarpals and similarities such as the morphology of the semilunate carpals that help to define both the affinities and the phylogenetic distance between these two closely related genera. The application of this new information to the analysis of dromaeosaurid specimens of indeterminate age may help to clarify our understanding of the particular growth stages they occupy within their own ontogeny.

2004 Conference Presentation: Society of Vertebrate Paleontology Annual Conference

POSTCRANIAL ONTOGENY OF DEINONYCHUS ANTIRRHOPUS, (SAURISCHIA, THEROPODA)
PARSONS, William L., 1621 Olean Rd., South Wales, NY 14139 and PARSONS, Kristen M., 1621 Olean Rd., South Wales, NY 14139

In 1982, an incomplete skeleton of a small dromaeosaurid (MCZ 8791) was recovered from Unit VI of the Himes Member, Cloverly Formation at the Wolf Creek site, Pryor Mountain field, south-central Montana.  After factoring in the disparity between the limb proportions of adults and sub-adults of this species that was initially observed on MOR 1178, the comparison of the pes elements of MCZ 8791 with similar pes elements of the holotype (YPM 5205) confirms the identification of this specimen as Deinonychus antirrhopus.  The unfused neural arches, as far back as a posterior dorsal vertebra, indicate that this specimen was at a younger growth stage than MOR 1178.  Additional skeletal elements preserved with MCZ 8791 include multiple vertebrae, right and left coracoids, a right ulna, a left radius, a right manus II-2, a left fibula and a left tibia. Both sub-adult specimens possess a proximal caudal vertebra which, after examining their qualitative morphology and the ratios of multiple linear measurements, though dissimilar in size, are otherwise identical.  The axial length of the centrum of this vertebra was be used as an index to constructed comparative growth ratios.  Analysis of these ratios indicates that this MCZ juvenile possessed forelimbs that were even greater in relative length, than the forelimbs found on MOR 1178.  These juvenile limb to body proportions approach those possessed by some other smaller members of the Dromaeosauridae.  The limb morphology of both these sub-adult specimens confirms a pattern of exaggerated forelimb development at a very early stage of growth.  These new data, along with the newly confirmed lateral position of the glenoid fossa of the scapula, permits a more accurate reconstruction of the ontogenetic modifications in limb morphology of D. antirrhopus and may add some possibilities to the considerations regarding the movement of the forelimb.

DESCRIPTION OF A NEW IMMATURE SPECIMEN OF DEINONYCHUS ANTIRRHOPUS, (SAURISCHIA, THEROPODA)PARSONS, William L., and PARSONS, Kristen m., 1621 Olean Rd. South Wales, N.Y. 14139

This specimen, MOR 117, was excavated from the basal portion of Unit VII of the Cloverly Formation in a lower Cretaceous site within central Montana. By comparison of the elements of its pes, lt. pes IV-5, rt. pes I-1, lt. pes IV-4, lt. pes III-4, and lt. pes III-1, with similar skeletal elements as found on the holotype YPM 5205, the fossil remains of the small theropod, MOR 1178, have been identified as Dienonychus antirrhopus. Though in some cases fragmentary, other skeletal elements include a lt. coracoid, rt. scapula, mid-section of a humerus, mid-section and partial distal end of a femur, lt. semi-lunar carpal, lt. manus 1-2, proximal end of a rt. fibula, tarsal, proximal end of a rt. 2nd metatarsal, fragment of a coossified sacral neural arches with a remnant of the neural spine lamina, several partial vertebrae, (1 distal caudal, 2 mid-caudal, 1 proximal caudal, 1 mid-dorsal, cervico-dorsal, cervical (C6?), and axis) fragment of a possible sternal plate, dentary fragment, squamosal fragment, 1 partial tooth, ilium fragments, as well as some other as yet unidentified fragments. The unfused nature of the neural arch of a cervical vertebra (C6?) led to the determination that the growth stage of this specimen was that of a subadult. When compared to the more mature AMNH, YPM and MCZ specimens, there appears to be a considerable degree of variation in the relative size of the various skeletal elements of MOR 1178. In particular, the limb morphology of this specimen indicates a pattern of growth development that may differ from OMNH 50268, as well as from what has been observed in the juvenile growth stages of other more familiar theropods. Along with the derived character of the curvature of the manus II-3 ungual, the confirmation of this limb morphology may indicate some unique aspects to the possible juvenile behavior of this genus.