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No description available.

No description available.

No description available.

No description available.

New specimens of the problematic group Sphenothallus have been recovered from the early Cambrian Shuijingtuo and Niutitang Formations in South China. The two sites from the Shuijingtuo Formation were collected from Yanjiahe and Changyang in Hubei and the equivalent Niutitang Formation from Siduping in Hunan. The ability to unite fossils in this genus is due to the pair of longitudinal thickenings which allow for species level analysis of morphology within this easily recognized genus. The morphology needed to differentiate species is subtle and may be influenced by abiotic factors. Differences between the three sampled sites representing different weathering states and paleo-environments allow us to investigate variations in preserved morphology related to abiotic factors (e.g., taphospecies and ecophenotypes). Despite differences in weathering and interpreted paleo-environments, no significant differences in preserved morphology are observed. Without abiotic biases, a logarithmic ontogenetic pattern of the organism indicates a set size of the adult as well as a set width of the longitudinal thickening throughout the organism's lifespan. The ability to incorporate multiple specimens from sites with differing diagenetic histories allows for greater sample sets to be created for investigating morphology, especially with early Cambrian organisms which rely on subtle character differences to identify species. / Master of Science

Several recent morphological studies have addressed the interrelationships of Osteoglossomorpha, a group that sometimes is considered the sister group of all other living teleostean fishes. Many characters used in these studies were found to be poorly defined, to be coded incorrectly or illogically, or to display more variation than was described. The goal of this study is to address these concerns and contribute generally to knowledge of the morphology and systematic relationships of osteoglossomorphs. Analysis of 72 characters scored for 20 genera resulted in 2 most parsimonious cladograms. The only difference in the topologies of these cladograms is in the position of †Lycoptera (recovered as either the sister group of all other osteoglossomorphs sampled or of †Eohiodon + Hiodon). †Ostariostoma is recovered as the sister group of all non-hiodontiform osteoglossomorphs. Mormyrids are sister group of notopterids + osteoglossids (including Pantodon). Mormyrids and notopterids usually are considered more closely related to each other than to any other group; characters not included here support this relationship and future consideration of these characters must be made. † Palaeonotopterus is interpreted as sister-group of all mormyrids sampled; however, only 22% of characters could be scored for it and its resemblance to notopterids are undeniable. General problems of character definition are discussed in my review of characters used in previous analyses.

Eastern newts (Notophthalmus viridescens) are a ubiquitous member of eastern North America’s caudate fauna. Unlike the typical amphibian, their life cycle is split into three phases instead of two, commonly called a triphasic life cycle. The larvae of N. viridescens are fully aquatic, eventually metamorphosing to become terrestrial juveniles called efts. Upon sexual maturity, the eft will metamorphose into a semi-aquatic adult whose external morphology resembles other aquatic salamander species. The eastern newt has predominantly been described by its external traits, namely color changes and lateral tail compression, rather than the musculoskeletal system and anatomy. Since these salamanders occupy different ecological niches (aquatic vs. terrestrial) throughout their lives and likely experience different forces acting on their skeletons, they provide a unique opportunity to study internal changes across ontogeny and ecology. We hypothesize that differences in buoyancy, torsion, and locomotion are expected to result in morphological shape changes across the life stages of the eastern newt’s skeleton. Using image data generated on a SkyScan 1273 micro-computed tomography (µCT) scanner (Bruker), 3D shape analyses will quantify shape differences between individual bones and test the hypothesis. Three-dimensional digital models of each bone of interest will be rendered from the scans in Dragonfly (Object Research Systems). Each 3D model is loaded into SlicerMorph (3DSlicer), where 3D geometric morphometrics is conducted for each bone to test for potential shape differences between each life stage. Our results support a shape difference between eft and adult in particular bones and conserved shape across ontogeny in other bones. Differences in shape are associated with a difference in functional demand across ecological niches.

Observations of nonhuman primate long bone microanatomy were undertaken with the explicit goal of recording intra- and interspecific variation in the percentage of osteonal bone. One-hundred and eight specimens with age, sex, body size, and positional behavior data representing 7 species (Galago senegalensis, Otolemur crassicaudatus, Macaca fascicularis, Macaca mulatta, Macaca arctoides, Erythrocebus patas, and Cercopithecus aethiops) were examined. Humeral and femoral shafts were examined histologically at the proximal, midshaft, and distal cross sections. Furthermore, the humeral and femoral midshaft sections were histologically examined at the anterior, posterior, medial, and lateral quadrants. Each cross section and quadrant were read specifically for percentages of osteonal bone. Data on cortical bone area and cortical thickness were also recorded for each section. Descriptive statistics, analysis of variance, and Model II regression (maximum likelihood estimation) were used to test for intra- and interspecific variation in osteonal bone for this population of primates. In general, several points concerning primate skeletal microanatomy have been revealed: (1) humeral and femoral microanatomy do not mirror each other in osteonal pattern, suggesting that different factors affect the bone microstructure of these limb bones, (2) primate species with different positional behavior express different distributions of osteonal bone and these differences reflect body size and mechanical usage, (3) after sexual maturation age does not affect intraspecific variations in the percentage of osteonal bone, (4) osteon area scales positively allometrically on body size (cortical area) suggesting that the rate of osteon area increases faster than the rate of increase in body size among primate species. Other conclusions have been drawn from this study, the most important point of which is that mechanical loading plays a large role in stimulating secondary osteon formation and that osteonal bone distribution reflects positional behavior and body size. This has profound implications for how future primate histological research can be conducted. Specific regions of nonhuman primate long bone appear to be particularly responsive to mechanical loading (i.e. the femoral midshaft posterior quadrant). These regions of bone therefore, may not be suited for aging techniques or for metabolic disorder analyses that are often applied in human research. The results of this study also have implications for the application of histological analysis to extinct primate specimens. Given the patterns of osteonal bone exhibited by extant primate species, it should be possible to determine positional behavior of extinct primate species from long bone microanatomy. This information will give primatologists one more important tool to be used in examining skeletal form as it relates to function in fossil primate species.

Studies on the evolution of the mammalian brain suggest that changes in subcortical structures include the division of the once continuous bed nucleus of the stria terminalis (BST) and medial amygdaloid nucleus (MA). Within each of these two areas is a group of vasopressin (AVP) cells, which together form the sexually dimorphic AVP system. Studies carried out for this thesis answered questions on the development and morphology of this system, with special reference to the evolutionary relationship between its two AVP cell groups. The first study tested whether, when placed in the same environment, developing AVP cells of the BST and MA can innervate similar targets. AVP cells in BST or MA fetal grafts showed similar fiber outgrowth into the lateral septum of adult AVP-deficient Brattleboro rats, which is inconsistent with the paucity of AVP projections from the MA to the lateral septum of non-deficient rats. This inconsistency suggests that developing AVP cells of the BST and MA can respond to similar environmental cues. The second study tested whether the AVP cells of the BST and MA have similar birthdates. Combining AVP and bromo-5-deoxy-2-uridine (BrdU) immunocytochemistry suggests that most AVP cells within the BST and MA are born around embryonic days (E) 12-E13, which is surprising, since this and previous studies suggest that most cells within the same divisions of the BST and MA are born around E14-16. No differences were found between birthdates of AVP cells in the BST and MA. However, there were differences between males and females. Females had proportionally more AVP cells colocalized with BrdU on E13. The third study tested whether projections of AVP cells in the BST and MA are similar. Anterograde tracing suggests that AVP cells of the BST and MA contribute in different proportions to the innervation of forebrain areas that contain sexually dimorphic AVP fibers. Retrograde tracing combined with AVP immunocytochemistry suggests that more AVP cells in the BST project to the lateral septum than AVP cells in the MA. These studies raise questions about the structural and functional development of the mammalian brain. Using the sexually dimorphic AVP system as an example for other systems, some of these questions are discussed in the final chapter.