Literature Review: Mammalian Anatomy

by Carl Strang

Today’s focus is two studies from the past year that brought out interesting aspects of mammalian anatomy and physiology.

Myhrvold CL, Stone HA, Bou-Zeid E (2012) What Is the Use of Elephant Hair? PLoS ONE 7(10): e47018. doi:10.1371/journal.pone.0047018

They studied the physics of heat transfer as influenced by the sparse hairs on elephant skin. They found that such widely scattered hairs facilitate convective heat loss, helping such large animals to dump excess body heat. This may explain the evolution of such body coverings in past hot climates among large-bodied animals. We might expect similar, widely scattered simple feathers on sauropod dinosaurs and T. rex.

Elephants’ scattered hairs have an important function. Elephant eyes are different from ours in important ways explained in the following reference.

Elephants’ scattered hairs have an important function. Elephant eyes are different from ours in important ways explained in the following reference.

M. I. Hall, J. M. Kamilar, E. C. Kirk. Eye shape and the nocturnal bottleneck of mammals. Proceedings of the Royal Society B: Biological Sciences, 2012; DOI: 10.1098/rspb.2012.2258

As described in ScienceDaily. They did a comparative study of mammalian eye structure, and found that except for humans, monkeys and apes, mammals retain eyes with structures suitable for nocturnal life (and similar to those of nocturnal birds and lizards). Mammals all evolved this structure during Mesozoic times, 250-65 million years ago, when day-active reptilian predators restricted them to a nocturnal lifestyle. When the basal primates later evolved in the Cenozoic Era, they adapted to a diurnal life, and their eye structure converged on those of day-active birds and lizards, giving them much higher visual acuity. The descendants of those primates, including humans, continue to share that structure.

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