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Paleontology senior section.

* Beatty, B. L. Division of Vertebrate Paleontology, University of Kansas Natural History Museum. Testing The Use Of The Extant Phylogenetic Bracket For Making Paleobiological Inferences. The inference of various paleobiological characteristics of fossil animals has long been the realm of discussion sections following descriptive texts of osteology. While living animals allow us to observe soft anatomy and behavior, the interpretation of the same in fossil taxa has been left to qualitative arguments of justification. The most parsimonious inference of such unknowable characteristics has been suggested to be those that are shared by the Extant Phylogenetic Bracket (EPB). This holds that given a crown group including the fossil taxon in question, we should assume that it shares characteristics that are shared between its fellows in the crown group and that of the sister taxon to the crown group. To test the reliability of this method of inference I propose to use the EPB method to make a prediction of a character state for an extant, known taxon. After making this prediction we can compare it with the known character state of the same extant taxon and, compiling such data for the entire clade, assign a character predictability index (CPI) for the character being inferred. With this CPI we can compare the relative security with which we can make inferences about certain behaviors and anatomical features. To avoid circular reasoning, these comparisons could be performed using a molecular phylogenetic tree. Once a CPI is well established for modern knowable taxa we can then move on to making paleobiological inferences based upon the EPB with a measure of our confidence in the results concerning each type of character.

* Burnham, D.A. Department of Geology, The University of Kansas. Comparison Of The Tarsus And Pes In The Dromaeosaurs Bambiraptor And Microraptor. Controversies surrounding evolution of flight are usually framed around the hands and arms (wings) rather than the structure of the foot. The anatomy and functional morphology of deinonychosaur tarsus and pes has been overlooked and is herein examined in light of recent discoveries. The study included a cursorial form, Bambiraptor (North America), and a newly reported arboreal form, Microraptor (Asia). Lifestyles of these animals should be reflected in the morphology of their feet since locomotion is fundamentally different between ground and tree-dwelling forms. It was found that the arboreal and cursorial morphotypes do have contrasting foot morphology, although both possess the retractable sickle claw, a synapomorphy of the Dromaeosauridae. The arctometatarsalian foot of Microraptor was proportionally smaller with deeply recurved claws on each digit, the hallux was reversed, and long, vaned feathers attached to the tarsus. These feathers alone would seem to encumber a cursorial lifestlye. It is more likely that it was arboreal, using the sickle claw for climbing with the reversed hallux and recurved unguals for perching. The foot of Bambiraptor had a normal tarsus that functioned well as a killing claw to disembowel prey. The hallux was not reversed and was positioned more proximally than Microraptor. The flattened pes unguals, combined with other features, implies it was cursorial. The resulting insight on foot morphology and function indicates the tree-dwelling forms acquired the specialized claw apparatus for climbing much earlier than the cursorial members of this group who subsequently modified the claw as a weapon. This would seem to support that an arboreal phase took place during the evolution of flight in birdlike dinosaurs.

* Gobetz, K.E., and J.L. Green, Natural History Museum and Biodiversity Research Center, University of Kansas, and Florida Museum of Natural History, University of Florida. Comparison Of Kansas And Florida Mastodon Diets Using Phytoliths In Calculus. Pilot studies to extract opal phytoliths from calculus on the molars of mammoth Mammuthus columbi and mastodon Mammut americanum from Kansas suggest that phytoliths may reveal major dietary constituents. Calculus of late Pleistocene Kansas M. americanum contained a mixture of pooid (cool, moist) grasses and deciduous tree leaves, suggesting that mastodons in Kansas may have been mixed-feeders rather than exclusive browsers. These results vary from the traditional view of mastodons as forest-dwelling browsers. They may reflect a preservation bias due to high amounts of silica in grasses compared to dicotyledonous plants. Alternatively, Kansas mastodons may have been mixed-feeders as a result of habitat. M. americanum phytoliths from Aucilla River (Pleistocene: late Rancholabrean) in Florida are compared with Kansas mastodon phytoliths to determine possible regional differences in diet. Previous mastodon dietary studies from Aucilla River using isotopes, microwear, and gastrointestinal contents have shown mastodons to be primarily browsers. Comparative studies of Kansas and Florida mastodons may help to resolve these questions and refine the use of phytoliths as dietary indicators.

* Gobetz, K.E., and L.D. Martin. Natural History Museum and Biodiversity Research Center and Department of Ecology and Evolutionary Biology, University of Kansas. Social Behavior In Extinct Beavers. Recently the discovery of an Oligocene beaver den in France documented the antiquity of social behavior characteristic of the modern semi-aquatic beaver, Castor. At about the same time (Oligocene), a group of North American beavers with short tails and flattened incisors (Palaeocastorinae) radiated into upland terrestrial fossorial niches. These beavers developed social structures more similar to those of fossorial squirrels than to other beavers. The species Palaeocastor fossor constructed deep (up to 3 m) burrows that were organized into large colonies of several hundred. These were probably similar to modern prairie dog colonies. A second, larger species, P. magnus, inhabited smaller aggregations of burrows that were spatially separated from the colonies of P. fossor. The smallest-sized beaver, Pseudopalaeocastor barbouri, excavated burrows of about 1 m depth. These are found in small groups of less than 10, and may occur within the P. fossor colonies. The difference in depth between burrows of the separate genera indicate a niche difference between these two beavers that enabled them to live in close proximity to one another.

Mark Dudley

Central Missouri State University
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Title Annotation:Collegiate & Senior Divisions
Author:Dudley, Mark
Publication:Transactions of the Missouri Academy of Science
Geographic Code:1U4MO
Date:Jan 1, 2004
Words:977
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