Research

“Comparative Anatomy of Mammalian Skulls” and
“Knee Osteoarthritis in a Baboon Model”

My research in comparative anatomy focuses on internal structures of mammalian skulls, particularly the nasal cavity, braincase, and inner ear. I use X-ray computed tomography (CT) to non-destructively visual these structures in fossil and extant mammal skulls with the purpose of describing skeletal anatomy related to sensory structures, and to utilize these data to reconstruct phylogenetic relationships among mammals. I’ve worked on a variety of mammalian groups including monotremes, marsupials, primates, chiropterans (bats), sirenians (manatees), proboscideans (elephants), and a number of completely extinct taxa such as notoungulates, an enigmatic group from South America. I work with colleagues from The University of Texas at Austin and the American Museum of Natural History (New York), among other institutions, and I have ongoing projects involving St. Mary’s University students.

MacriniFig1

The above image shows a digital 3-D reconstruction of the semitransparent skull of Hadrocodium wui, a tiny early Jurassic age mammal that weighed just two grams. The cranial endocast, indicating the braincase cavity, is shown in red. The imagery was generated from CT images of the skull and formed the basis of Rowe et al. (2011). Scale: the skull is 13 mm long.

My other research program examines knee osteoarthritis (OA), a debilitating joint disease in humans, using baboons (Papio hamadryas ssp.) from the Texas Biomedical Research Institute (TBRI) colony in San Antonio. These baboons, like humans, naturally develop OA. This research is conducted in collaboration with Dr. Lorena M. Havill (TBRI, Department of Genetics) among others, and is aimed at uncovering the etiology of early stage OA and understanding the genetic and other factors contributing to disease risk. Ongoing projects involving St. Mary’s students include gross anatomical studies of OA in the articular cartilage of the knee joint, and analyses of histological and radiographic evidence of OA in baboons.

Current research students:

Christina Karmann, senior Biology major and Biaggini Research Program scholar
Eddie Morales, senior Environmental Science major
Brandon Ruiz, sophomore Biology major and San Antonio Livestock Exposition Scholar Program scholar

Recent publications:

Rowe, T., T. E. Macrini, and Z.-X. Luo. 2011. Fossil evidence on origin of the mammalian brain. Science 332:955-957.

Macrini, T. E. 2012. Comparative morphology of the internal nasal skeleton of adult marsupials based on X-ray computed tomography. Bulletin of the American Museum of Natural History 365:1-91.

Beatty, B. L., T. Vitkovski, O. Lambert, and T. E. Macrini. 2012. Osteological associations with unique tooth development in manatees (Trichechidae, Sirenia): a detailed look at modern Trichechus and a review of the fossil record. Anatomical Record 295:1504-1512.

Giannini, N. P., T. E. Macrini, J. R. Wible, T. Rowe, and N. B. Simmons. 2012. The internal nasal skeleton of the bat Pteropus lylei K. Andersen, 1908 (Chiroptera: Pteropodidae). Annals of Carnegie Museum 81:1-17.

Macrini, T. E., H. B. Coan, S. M. Levine, T. LermaC. D. SaksD. J. Araujo, T. L. Bredbenner, R. D. Coutts, D. P. Nicolella, and L. M. Havill. 2013. Reproductive status and sex show strong effects on knee OA in a baboon model. Osteoarthritis and Cartilage 21:839-848.