Physiology, Comparative

This study focused on the temporalis configuration in Middle Pleistocene
hominins and how that configuration is correlated with various structures in the
craniofacial complex. Three hypotheses were tested using univariate comparisons,
regression, and scaling analyses. Results showed that Middle Pleistocene hominins
have small anterior temporalis muscles relative to the size oftheir faces, contrary to
expectation. This discrepancy may be explained by a decrease in the size of the
temporal fossa as a consequence of postorbital constriction concurrent with
encephalization. Additionally, this configuration may have implications for the
biomechanics of chewing, rendering the masticatory structures of Middle Pleistocene
hominins less efficient than in other hominins. Future studies in this area should
analyze the size of the temporal fossa in conjunction with rates of encephalization,
using cranial capacity as a measure of vault size. Such analyses, coupled with
comparisons of temporalis muscle size, will better explain the relationships suggested
here.

Specific dynamic action (SDA) describes a post-feeding increase in oxygen consumption where most energy derived from food is allocated to post-absorptive processes, including growth and maintenance. SDA and growth in hatchling sea turtles is of special interest because they experience drastic changes in diet, oxygen availability and habitat during the first several months of life. This study investigated SDA variation between species and among age groups. SDA was quantified in two species of sea turtle (Chelonia mydas, Caretta caretta) at 7, 30, 60, & 90 days post-hatching. Turtles were fed a known amount of food, and oxygen consumption was monitored using a metabolic chamber. SDA percentage of total energy did not increase with age (species pooled), although magnitude of SDA was higher in C. mydas when compared to C. caretta (ages pooled). These results imply that SDA does not increase proportionally with age, and that hatchling C. mydas use more absolute energy for SDA than C. caretta .