Os padrões de covariância genética entre caracteres, expressos pela matriz de covariância aditiva G, desempenham um papel importante na evolução de morfologias complexas, visto que esta matriz influencia a direção e magnitude da resposta à seleção em uma população. Assumindo-se a estabilidade da matriz G ao longo do tempo, pode-se testar explicitamente hipóteses acerca da influência de processos evolutivos sobre a diversificação. Espera-se que esta matriz influencie os padrões expressos por sua equivalente fenotípica P, devido a contingências funcionais e ontogenéticas na relação entre genótipo e fenótipo, que levam à estruturação de modularidade nesta relação, de modo a otimizar a evolvabilidade. No presente trabalho, investiguei a estrutura da covariância genética no crânio e mandíbula de uma população do roedor sigmodontíneo Calomys expulsus, com o objetivo de estimar a similaridade entre covariâncias fenotípicas e genéticas; também avaliei a influência de padrões de modularidade sobre ambos os níveis de organização da variação morfológica. As matrizes P e G que obtive para o crânio e para a mandíbula se mostraram bastante similares no que diz respeito à sua estrutura de covariação e se relacionam parcialmente às hipótese de modularidade estabelecidas. Os resultados que obtive aqui são bastante similares àqueles obtidos para os mamíferos como um todo, portanto suportando a hipótese de estabilidade no padrão de covariâncias genéticas e fenotípicas na evolução do grupo. / Patterns of genetic covariance between characters (represented by the additive covariance matrix G) play an important role in the evolution of morphological complexes, since they influence the direction and norm of the response to selection in a population. Therefore, the assumption that G-matrices are stable through evolutionary timescales allows evolutionary biologists to infer the influence of evolutionary processes that operate over biological diversification. These matrices are also expected to influence the patterns expressed in their phenotypic counterparts (P-matrix), because of the imposition of multiple developmental and functional contingencies over the genotype/phenotype map, that leads to its modular organization in order to increase evolvability. Here, I have investigated patterns of genetic covariance structure in the skull and mandible of a population of the vesper mouse Calomys expulsus in order to estimate the level of similarity between additive and phenotypic covariances; I have also evaluated the influence of expected patterns of modularity over both levels of morphological variation. For either skull and mandible, I have obtained P- and G-matrices that are strongly similar in their structure; these matrices also support the modularity hypotheses for developmental and functional constrains, akin to the overall results obtained for mammals, thus supporting the hypothesis of stability in genetic and phenotypic covariance structure in mammalian evolution.

PhD (Zoology) / Department of Zoology / The order Rodentia is the most speciose group of mammals with muroids being the most diverse superfamily. Since they are represented in arboreal, semiaquatic, subterranean and terrestrial niches, rodents may exhibit morphological traits reflecting their adaptations to such diverse environments. This thesis focuses on the morphology of the endocranium, auditory bulla and cochlea in three tribes (Otomyini, Taterillini and Gerbillini) representing 10 species of African rodents, concentrating on their variability, function and adaptability, using micro-CT imaging and 3D shape comparative methods. Additionally, variations in cranial size were also studied in respective of global warming and climatic variables. Morphological changes/variations are a result of environmental change, therefore each chapter in this study details the effect of environmental change (in space and time) on different morphological traits i.e. general cranial size (chapter 2), cochlea and auditory bulla (chapter 3) and endocranial size and shape (chapter 4). With chapter 2 dealing specifically with climate change in its strict sense and the remaining two chapters looking at different environmental gradients. Chapter 2 tests the applicability of the “third universal response to warming” (i.e. declining body size) and the Resource Rule in two murid subfamilies, Murinae and Gerbillinae. The study shows that the third response is not as universal as only one species conformed to this response. Further, food availability (Resource Rule) was shown to be the more important factor correlated with body size variations in rodent species than Bergmann’s Rule. Chapter 3 looks at the auditory bulla and cochlea, the morphological traits that play a role in hearing capabilities of rodents. I found, with some exceptions, that bulla and cochlea modifications between species could be explained by environment, phylogeny and/or allometry. In addition, I concluded that true desert adapted laminate-toothed rats and gerbils use both bulla and associated cochlea hypertrophy. Chapter 4 shows larger brain size in Taterillini and two species of Otomyini, with life histories and environment being the most probably factors responsible for xiv this. Using a novel method of diffeomorphism (deformation models), there was more variation in endocranial morphology between the gerbils and laminate-toothed rats than within them with olfactory bulb, paraflocculi, and posterior ventral cortex showing the most variability. Overall, this thesis shows that variations in the morphological traits studied are strongly influenced by the environment and function. / NRF

Presented in the session "Cultural Meanings of Head Treatments in Mesoamerican and Andean Societies.” Over the past 10 years researchers in Mesoamerica have increasingly come to agree that cranial modification was a normal part of growing up in Maya society. One component of cranial modification appears to have been ritually sealing one or more of these animating essences in infants’ heads. Bodies in Mesoamerica were both permeable and partible and contained multiple animating essences associated with various aspects of personhood, animacy, and illness. Thus, one current question is identifying precisely what was being sealed in cranial modification. In this paper I review animating essences among the Maya to discuss which appear to have been the most likely candidates for sealing through cranial modification. The two most relevant essences are baah and ik’. Baah is a conflation of personhood and the head, could be interacted with by other individuals after corporeal death, and appropriated by enemies. Ik’ is breath soul and could exit the body from various orifices. Although baah is explicitly associated with the head among the Maya, here I argue that ik’ is at least as likely as baah to have been targeted for sealing through cranial modification.

The present study entails descriptions of several well-preserved skulls from the pampathere species Holmesina floridanus, recovered from Pliocene localities in central Florida and housed in the collections of the Florida Museum of Natural History. Bone by bone descriptions have allowed detailed reconstructions of cranial morphology. Cranial foramina are described and illustrated in detail, and their contents inferred. The first ever description of an isolated pampathere petrosal is also included. Cranial osteology of Holmesina floridanus is compared to that of Pleistocene species of Holmesina from both North and South America (Holmesina septentrionalis, Holmesina occidentalis), as well as to the other well-known pampathere genera, to closely related taxa among glyptodonts (Propalaehoplophorus), and to extinct and extant armadillos (Proeutatus, Euphractus). This study identifies a suite of apomorphic cranial features that serve to diagnose a putative, progressive series of more inclusive monophyletic groups, including the species Holmesina floridanus, the genus Holmesina, pampatheres, pampatheres plus glyptodonts, and a clade formed by pampatheres, glyptodonts, and Proeutatus. The study highlights the need for further anatomical investigations of pampathere cranial anatomy, especially those using modern scanning technology, and for analyses of pampathere phylogenetic relationships.

No description available.

The study of human cranial morphology has a long and contentious history. This study is the first large scale analysis of ecoregion specific human cranial modularity and integration. It utilizes an analysis of morphometric craniofacial variation and ecoregion affinity to better understand the environmental contribution to biological shape. This study tested three hypotheses. First, that there was variation in craniofacial shape that was linked to an individual’s ecoregion. Second, that there were ecoregion specific patterns of cranial modularity. And third, that the patterns of cranial integration (or the level of covariation between any two modules) were also associated with an individual’s ecoregion, and that different environments would result in different patterns of modular dependence and independence. Three-dimensional scans of 298 human crania were collected from museums, representing four higher level ecoregions and 11 lower-level ecoregions. Each cranium was mapped and placed within two hierarchical ecoregions. By examining ecoregions, instead of individual climatic variables, this analysis gives a more complete picture of how the environment is influencing cranial variation. Modules, or relatively independent morphological regions of the crania, were identified and their level of integration was assessed for every ecoregion. Modular integration is an analysis of the relative strength of the covariation between any two modules, and previous research theorized that changes in integration reflected changes in modular independence during development (Bastir and Rosas, 2005; Hall, 2005; Raff, 1996). The variation in strength between modules, both intrapopulation and interpopulation, were assessed and various explanations were explored. This analysis found that each ecoregion exhibited significantly different craniofacial shape from one another. Patterns of integration were also variable by ecoregion, suggesting that the ecological shape variation observed was solidified early in development. This study also identified the presence of a nasal module in each ecoregion. Overall, the findings of this study demonstrate that human crania are variable by ecoregion and that environmental conditions have led to ecoregion specific patterns of cranial modular integration. / Anthropology

Little research has been done to validate the biomechanical principles of tibial tuberosity advancement (TTA) throughout stance. The present study evaluates the effects of TTA on kinematics of the cranial cruciate (CrCL) deficient stifle during early, middle, and late stance. Cadaveric pelvic limbs were evaluated for the effects of TTA on kinematics under a load equivalent to 30% bodyweight and under the following treatment conditions: intact CrCL, CrCL deficient, TTA-treated, and TTA treated + meniscal release. Electromagnetic tracking sensors were used to determine tibial subluxation and rotation relative to the femur. Transection of the CrCL resulted in significant cranial tibial subluxation during early, middle, and late stance and significant internal rotation during early and middle stance. TTA normalized tibial subluxation in early, middle, and late stance but was unsuccessful in normalizing axial rotation in middle stance. Meniscal release had no effect on cranial/caudal or rotational displacement when performed following TTA.

To date, numerous studies have examined the range of cranial thickness variation in modern humans. The purpose of this investigation is to present a new method that would be easier to replicate, and to examine sex and age variation in cranial thickness in a white sample. The method consists of excising four cranial segments from the frontal and parietal regions. The sample consists of 165 specimens collected at autopsy and 15 calvarial specimens. An increase in cranial thickness with age was observed. The results suggest that cranial thickness is not sexually dimorphic outside the onset of hyperostosis frontalis interna (HFI).

A thorough morphological description of Teleoceras material from the Gray Fossil Site, Gray, Tennessee is provided. This is the only record of a browsing Teleoceras and, as a late Hemphillian locality, represents one of the youngest populations. Linear measurements of post-cranial elements indicate proportional differences between Teleoceras from the Gray Fossil Site and those from other Hemphillian localities. These differences are more pronounced in the elements of the forelimb than in those of the hind limb. Statistical analyses of post-cranial elements from 3 Hemphillian species of Teleoceras suggest that these differences should not be used to separate species. However, the elements do typically sort well by fossil locality, which suggests that post-cranial morphology is plastic enough to become modified within a population. Furthermore, dental morphology comparisons with the holotypes of these species indicate that the GFS rhino represents a previously undescribed species.

Here, a morphological description of the extinct meline badger Arctomeles dimolodontus from the Gray Fossil Site (GFS), Tennessee is provided with comparison to extant Meles meles. Originally described solely on upper teeth of a single individual, the recovery of several crania and jaws provides a sample of at least five individuals, affording the largest known fossil sample in North America of the enigmatic Melinae. Examination of A. dimolodontus skull material reveals extreme intraspecific variation in previously identified diagnostic characters, highlighting the need for caution when identifying fossil taxa based on similarly fragmentary remains. Dental variation is likely a result of hypocarnivory, and dentition may have become more complex over time in response to diet. Based on cranial characters, A. dimolodontus appears to be sexually dimorphic, similarly to extant badgers. Arctomeles dimolodontus has a complex auditory region with large bullae compared to M. meles, suggesting relatively heightened auditory sensitivity.