Research Training Program

Shannon Schwaller
St. Cloud State University
St. Cloud, MN

Richard Thorington, Ph. D.
Supervising Scientist
Department of Vertebrate Zoology
Division of Mammals

"This program has given me essential skills to help me succeed in any graduate program."

A Morphometric Analysis of Hand Anatomy in Five Genera of New World Monkeys

Like humans, the hands of Central and South American, or New World, monkeys are very important for interacting with the world around them. New World monkeys exploit a large variety of habitats and many species have evolved specialized hand adaptations. This research focused on a statistical analysis of anatomy, or morphometric analysis, to describe these adaptations. This method allowed for a detailed study of five different genera of New World monkeys. Woolly monkeys (genus Lagothrix), Howler monkeys (Alouatta) and Spider monkeys (Ateles), share many anatomical similarities, such as elongated fingers and small thumbs, as a result of specialized hanging and swinging behavior. This group with specialized hand anatomy was compared with a second set of monkeys, the Capuchin monkey (Cebus) and the Squirrel monkey (Saimiri), which have very little specialization. Measurements taken on twenty-nine monkeys from the specialized group were compared to the measurements of thirty-seven monkeys from the non-specialized group in order to test the hypothesis that similar anatomical changes in hand anatomy, such as the elongation of the fingers, occurs in the same way in closely related monkeys. The results did not confirm the hypothesis. Although all the monkeys with specialized hand anatomy had elongated fingers for hanging and climbing, the Spider monkeys' finger bones were proportionately thinner and longer then the other specialized monkeys. Despite having long fingers like the Woolly monkey and Howler monkey, the Spider monkey had more reduced thumbs. Statistical analysis also showed that length of the fingers in Spider monkeys might develop in a very different way than in the other closely related species. This result proposes many questions concerning precise genetic control of hand development. In disproving the hypothesis, this research provided very important data concerning the evolutionary changes in the primate hand and may help future scientists better understand the genetic processes involved in primate hand evolution.

This research was supported by a grant from the National Science Foundation Research Experiences for Undergraduates program, Award Number DBI-9820303.

Letter of Gratitude