A grant has been awarded to Dr. Anthony Barnosky and Mr. Robert Feranec at the University of California at Berkeley to study whether the evolution of specialized features in ancient mammals, so-called key adaptations, causes ecological specialization or generalization. The morphological specialization to be studied is evolution of high-crowned teeth in hoofed mammals, which has been regarded as a key adaptation that led to specialized feeding on newly evolved grasslands. This study analyzes morphology relative to diet and habitat occupation in the horse, camel, and cow families. The main method used to determine diet is analysis of stable carbon isotope values found in tooth enamel. This proxy for diet indicates whether mammals focused feeding on grasses or on trees and shrubs. Habitat occupation is resolved by determining the number and location of fossil sites in which the animals occurred. The goal of this study is to analyze the diet and habitat occupation of hoofed mammals at three time periods, older than 7 million years ago, between 10,000-30,000 years ago, and modern hoofed mammals. This research spans almost 20 million years of mammal evolution, and incorporates morphology, diet, and habitat use in the analysis. This proposed study will test preliminary results that suggest evolution of high-crowned teeth allows mammals to become more generalized, which differs from current hypotheses.
The study is important because it sheds light on the ecology of more than 20 genera of mammals through nearly 20 million years of hoofed-mammal evolution. It also provides the knowledge of whether modern hoofed mammals occur in particular ecosystems because they are specialized for narrowly defined niches, or if they currently occupy the ecosystem because of reasons like preference, competition, or even chance. The study also contributes new teaching tools and research applications for the uses of isotopes to mammal paleontology.
