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Morphology is the result of the interaction between ontogeny and the environment, and the relationship between these two forces, and its importance in evolution, is the subject of increasingly widespread research. I investigated the relationshipMoreMorphology is the result of the interaction between ontogeny and the environment, and the relationship between these two forces, and its importance in evolution, is the subject of increasingly widespread research. I investigated the relationship between environmental selection and morphology, especially with regard to auditory bulla morphology. I analyzed morphology and examined ontogeny across eighteen species of mongooses. I then mapped the ontogeny onto a phylogeny in order to distinguish ecological signals from phylogenetic ones. Next I examined the ecology of each species to determine if there was a correlation between ecology and bulla volume. I test the hypothesis that vegetationally open, and environments have causally influenced the evolution of relatively enlarged auditory bullae in herpestid Carnivorans.-The volume of the middle ear, or auditory bulla, is an important feature of the mammalian auditory system and is partially responsible for the range of frequencies that an organism can hear. Previous studies have shown that larger auditory bullae are more sensitive to low frequency sounds (2 kHz or less), and that species possessing these enlarged bullae are often found in open habitats. The greater sensitivity that an enlarged bulla provides is important for these species and studies of desert dwelling mammals indicate that these species have a selective advantage in these environments.-Herpestids are a group of small to medium sized carnivores and are members of the Carnivoran Glade Feliformia. They are relatively morphologically unspecialized, and inhabit a wide variety of environments, ranging from rainforest to desert.-The results indicate that species living in open habitats do, indeed, have relatively larger auditory bullae than those in closed habitats, and it is very niche specific. Sympatric species may have relatively different bulla volumes depending on whether they inhabit the open or closed areas of that habitat. An enlarged auditory bulla independently evolved five times in the herpestids. The ontogeny suggests that although an enlarged auditory bulla is a paedomorphic feature, the processes that resulted in the enlarged bulla differ amongst the species. These results all indicate that selection in open habitats is the driving force behind auditory bulla enlargement in herpestids.