title: Aquatic Habits of Cetacean Ancestors: Integrating Bone Microanatomy and Stable Isotopes.
abstract: The earliest cetaceans were interpreted as semi-aquatic based on the presence of thickened bones and stable oxygen isotopes in tooth enamel. However, the origin of aquatic behaviors in cetacean relatives (e.g., raoellids, anthracotheres) remains unclear. This study reconstructs the origins of aquatic behaviors based on long bone microanatomy and stable oxygen isotopes of tooth enamel in modern and extinct cetartiodactylans. Our findings are congruent with published accounts that microanatomy can be a reliable indicator of aquatic behaviors in taxa that are obligatorily aquatic, and also highlight that some "semi-aquatic" behaviors (fleeing into the water to escape predation) may have a stronger relationship to bone microanatomy than others (herbivory in near-shore aquatic settings). Bone microanatomy is best considered with other lines of information in the land-to-sea transition of cetaceans, such as stable isotopes. This study extends our understanding of the progression of skeletal phenotypes associated with habitat shifts in the relatives of cetaceans.
authors.affiliation: *Department of Anatomy and Neurobiology, Northeast Ohio Medical University, 4209 State Route 44, Rootstown, OH 44272-0095, USA lcooper@neomed.edu.
authors.forename: Lisa Noelle
authors.initials: LN
authors.lastname: Cooper
authors.affiliation: Department of Geology and Geophysics, University of Wyoming, 1000 E. University Ave, Laramie, WY 82071-3006, USA.
authors.forename: Mark T
authors.initials: MT
authors.lastname: Clementz
authors.affiliation: *Department of Anatomy and Neurobiology, Northeast Ohio Medical University, 4209 State Route 44, Rootstown, OH 44272-0095, USA.
authors.forename: Sharon
authors.initials: S
authors.lastname: Usip
authors.affiliation: Birbal Sahni Institute of Palaeobotany, 53, University Road, Lucknow, (UP) 226007, India.
authors.forename: Sunil
authors.initials: S
authors.lastname: Bajpai
authors.affiliation: Department of Anatomy, Howard University, College of Medicine, 520 W Street, NW, Washington, D.C. 20059, USA.
authors.forename: S Taseer
authors.initials: ST
authors.lastname: Hussain
authors.affiliation: *Department of Anatomy and Neurobiology, Northeast Ohio Medical University, 4209 State Route 44, Rootstown, OH 44272-0095, USA.
authors.forename: Tobin L
authors.initials: TL
authors.lastname: Hieronymus
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000033:anatomy & histology / Q000378:metabolism; D002591:Cetacea / Q000502:physiology*; D017753:Ecosystem; D007553:Isotope Labeling; D007554:Isotopes / Q000378:metabolism
chemical_list: D007554:Isotopes