Locomotion and Behavior of the Ancient Whale Georgiacetus

Primary Faculty Mentor’s Name

Dr. Kathlyn Smith

Proposal Track

Student

Session Format

Poster

Abstract

Georgiacetus vogtlensis is one of the most primitive archaeocetes (ancient whales) from North America. Discovered in the northern Atlantic Coastal Plain of Georgia in 1983, it has been interpreted as semi-aquatic, but shows important adaptions toward fully aquatic behavior, including the lack of articulation between the pelvis and sacral vertebrae. Among all protocetids, Georgiacetus is most closely related to the clade Pelagiceti, which includes the common ancestor of all fully aquatic archaeocetes and their descendants, including modern whales. The goal of this study is to elucidate aspects of Georgiacetus locomotion and behavior that are closely related to both semi-aquatic and aquatic lifestyles by comparing the skeletal morphology of the lumbar region of Georgiacetus to modern mammals of a known lifestyle. Unlike previous studies using muscle scarring, this investigation into those changes in skeletal morphology that occurred during the land-to-sea transition of whale evolution was achieved via multivariate analyses of 17 measurements of lumbar vertebrae from more than 30 modern and extinct mammals. Lumbar vertebrae were used because they likely underwent the most drastic changes during the early stages of whale evolution, as dorsomobile archaecetes evolved relatively quickly from dorsostable artiodactyls. To investigate the relative mobility of its lumbar vertebrae, Georgiacetus was included in a Principal Components Analysis (PCA) of lumbar vertebrae from modern and extinct aquatic, semi-aquatic, and terrestrial species. Four PCAs were conducted, one for each of the best preserved lumbar for Georgiacetus. Based upon its close relationship with Pelagiceti, we anticipated that mobility in the lumbar region would be more like that of fully aquatic animals than that of any presumed semi-aquatic animals in the PCA. The results, however, revealed that the lumbar region of Georgiacetus, while similar to those of a semi-aquatic lifestyle, was more dorsostable than other archaeocetes used in the study. Future work will include, a Discriminant Function Analysis to classify Georgiacetus into a semiaquatic or fully aquatic group based upon modern mammals of a known lifestyle, as well as the addition of more aquatic species in the PCA. We hypothesize that Georgiacetus will be classified as semi-aquatic using this method, but that the lumbar vertebrae will show adaptations toward a more fully aquatic behavior.

Keywords

Georgiacetus, Lumbar vertebrae, Principle Components Analysis, Dorsomobile, Dorsostable

Award Consideration

1

Location

Concourse/Atrium

Presentation Year

2014

Start Date

11-15-2014 2:55 PM

End Date

11-15-2014 4:10 PM

Publication Type and Release Option

Presentation (Open Access)

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Nov 15th, 2:55 PM Nov 15th, 4:10 PM

Locomotion and Behavior of the Ancient Whale Georgiacetus

Concourse/Atrium

Georgiacetus vogtlensis is one of the most primitive archaeocetes (ancient whales) from North America. Discovered in the northern Atlantic Coastal Plain of Georgia in 1983, it has been interpreted as semi-aquatic, but shows important adaptions toward fully aquatic behavior, including the lack of articulation between the pelvis and sacral vertebrae. Among all protocetids, Georgiacetus is most closely related to the clade Pelagiceti, which includes the common ancestor of all fully aquatic archaeocetes and their descendants, including modern whales. The goal of this study is to elucidate aspects of Georgiacetus locomotion and behavior that are closely related to both semi-aquatic and aquatic lifestyles by comparing the skeletal morphology of the lumbar region of Georgiacetus to modern mammals of a known lifestyle. Unlike previous studies using muscle scarring, this investigation into those changes in skeletal morphology that occurred during the land-to-sea transition of whale evolution was achieved via multivariate analyses of 17 measurements of lumbar vertebrae from more than 30 modern and extinct mammals. Lumbar vertebrae were used because they likely underwent the most drastic changes during the early stages of whale evolution, as dorsomobile archaecetes evolved relatively quickly from dorsostable artiodactyls. To investigate the relative mobility of its lumbar vertebrae, Georgiacetus was included in a Principal Components Analysis (PCA) of lumbar vertebrae from modern and extinct aquatic, semi-aquatic, and terrestrial species. Four PCAs were conducted, one for each of the best preserved lumbar for Georgiacetus. Based upon its close relationship with Pelagiceti, we anticipated that mobility in the lumbar region would be more like that of fully aquatic animals than that of any presumed semi-aquatic animals in the PCA. The results, however, revealed that the lumbar region of Georgiacetus, while similar to those of a semi-aquatic lifestyle, was more dorsostable than other archaeocetes used in the study. Future work will include, a Discriminant Function Analysis to classify Georgiacetus into a semiaquatic or fully aquatic group based upon modern mammals of a known lifestyle, as well as the addition of more aquatic species in the PCA. We hypothesize that Georgiacetus will be classified as semi-aquatic using this method, but that the lumbar vertebrae will show adaptations toward a more fully aquatic behavior.