Publication Date

2021

Document Type

Dissertation/Thesis

First Advisor

Samonds, Karen E.

Degree Name

M.S. (Master of Science)

Legacy Department

Department of Biological Sciences

Abstract

Madagascar has many species of extinct megafauna, including up to three species of extinct hippopotamus. Subfossil hippo specimens have been found at sites across Madagascar, yet the number of species and taxonomic relationships of the extinct Malagasy pygmy hippopotamus are poorly understood. This thesis will analyze cranial and postcranial bones to improve our understanding of the diversity and taxonomy of Malagasy subfossil hippos, focusing on adults from Ampasambazimba and Tsaramody and juveniles from Ampasambazimba and Anjohibe. Measurements of the tibia and femur of adult specimens, which are used as diagnostic features in other studies, may not be accurate diagnostic features, as analyses of tibiae and femora morphometric measurement data did not identify discrete clusters that could have been taxonomically distinct groups. These analyses showed only one group of hippopotamuses using data that was not log-transformed. In addition, analyses of the radioulna support one or two groups of hippos, depending on how much data are included in the analyses. Species were identified using the skull and mandibles, because they had identifiable diagnostic features; H. madagascariensis was present at Ampasambazimba and Anjohibe and H. lemerlei may have been present at Ampasambazimba. To examine growth patterns in Malagasy pygmy hippos, subadult cranial and postcranial bones were measured and examined for features that would indicate species and age at death. Using dental characteristics of extant common hippopotamuses to establish age, specimens were estimated to range in age from 3±0.5 years old to 7±1 years old. Interpreting data using growth rates from two living species (common hippos and African pygmy hippos) produced different results. If subfossil hippopotamuses reached sexual maturity at the same age as common hippos, most subfossil specimens were unlikely sexually mature (with the exception of one if it was male), while if they followed the growth patterns of African pygmy hippopotamuses, most would likely have been sexually mature. Stable isotope data from published papers as well as unpublished data were analyzed with Kruskal-Wallis and Mann-Whitney statistical tests to examine differences in the diets and environments of Malagasy pygmy hippopotamuses from different ecoregions and species. Based on carbon stable isotope values, most of the diet of hippopotamuses from the Central Highlands and Dry Deciduous Forest was comprised of C3 plants, while hippopotamuses from the Spiny Thicket ecoregion ate a combination of C3 and C4 plants. Two hippopotamuses from Ampasambazimba and one from Tsaramody had δ13C values greater than would be expected for animals with a solely C3 diet despite the fact that they lived on the Central Highlands. This suggests that some hippopotamus diets incorporated a greater proportion of C4 plants than others in the region. Greater δ15N values from hippopotamuses in the Succulent Woodland and Spiny Thicket relative to the Central Highlands likely reflect a more arid environment. Hippopotamus lemerlei had greater δ15N values than H. madagascariensis; however, sample sizes (particularly for H. lemerlei) were small, and all H. lemerlei specimens were from the Succulent Woodland ecoregion. Therefore, this difference in nitrogen stable isotope values could reflect a difference in environments rather than a difference between species.

Extent

171 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

Download

Share

COinS