Overview
From elephants to rhinos to bison, enormous increases in body mass have repeatedly evolved within Mammalia over relatively short timescales, leading to a diversity of size and shape. In this project, we will assess size and shape changes in the skull, brain, cranial sinuses and jaw muscles of mammals over a range of body masses using 3D digital imaging, geometric morphometric, and biomechanical principals.
About this opportunity
As mammals grow to gigantic sizes, their brains lag behind and become proportionally smaller. This scaling relationship presents a space conundrum of wrapping larger jaw muscles around a relatively smaller braincase. Expanding air-filled cavities, cranial sinuses, provides a solution to increase the skull surface area while minimising bone mass, but their hidden anatomy makes them difficult to study. This project will investigate the role of cranial sinuses, their relative size, and their relationships to skull shape and soft tissue scaling, to better understand how they contribute to building giants.
To reach the adult morphology, the bones of the skull grow and adapt to the pressures of the expanding brain, eyes and muscles. This can result in competing demands between the size and shape of the brain and the masticatory muscles, as brain size remains relatively small in large mammals, but the jaw muscles become larger. The presence of extensive cranial sinuses in large mammals may be an adaptive response to the relative growth rates of these soft tissue demands. However, it is unknown whether they may optimize muscle function, redistribute skull mass, or both. Previous research on mammalian skull development and evolution has largely focused on brain size or jaw musculature in isolation, neglecting how cranial sinuses integrate into these systems. The difficulty of visualising internal anatomy of the skull has also limited our ability to explore the morphology and function of sinuses. With advanced computed tomography (CT) imaging, we can now see and measure the 3D volume and shape of internal cavities of the skull. Our goal is to integrate evolutionary morphology and biomechanics to test the hypothesis that cranial sinus expansion in large-bodied mammals plays a key role in trade-offs between functional constraints from the brain and feeding apparatus. Through this project, we will provide new insights into craniofacial scaling and macroevolutionary trends, offering a comprehensive understanding of how tissues of the skull interact to form the adult morphology.
During this PhD, the candidate will lead the investigation of the functional anatomy, centre of mass estimates, and the relationships between these and size of the endocranial sinuses. This will also feed back to skull and sinus morphology. This project provides set objectives, achievable challenges, and varied training for a PhD student.
The student will be based with the principal supervisor, Dr Alana Sharp (University of Liverpool), in the Evolutionary Morphology and Biomechanics (EMB) research group, a vibrant and diverse research group fostering opportunities for networking and development. Co-supervision will be provided by Dr Nathan Jeffery (University of Liverpool) and Dr Ryan Felice (University College London). In addition to the formal training provided by the supervisors, and a wide range of additional training resources are available through the University of Liverpool Doctoral College, the student will also have the support and training that is provided by their peers within the research group.