Dear MARMAM subscribers,
My co-authors and I are pleased to announce the publication listed below in the current issue of Journal of Mammalian Evolution: *Enamel Microstructure in Eocene Cetaceans from Antarctica (Archaeoceti and Mysticeti)* Carolina Loch, Monica R. Buono, Daniela C. Kalthoff, Thomas Mörs, Marta S. Fernández doi: /10.1007/s10914-018-09456-3 *Abstract* Modern baleen whales have no adult teeth, whereas dolphins and porpoises have a homodont and polydont dentition, with simplified enamel microstructure. However, archaic cetaceans (archaeocetes and early mysticetes and odontocetes) had a complex and ornamented dentition, with complex enamel microstructure as terrestrial mammals. This study describes the morphology of teeth and enamel microstructure in two fossil cetaceans from Antarctica: a basilosaurid archaeocete from the La Meseta Formation (middle Eocene); and Llanocetus sp. from the Submeseta Formation (late Eocene), one of the oldest mysticetes known. The two teeth analyzed were lower premolars, with transversely compressed triangular crowns composed of a main cusp and accessory denticles. The enamel microstructure of the basilosaurid and Llanocetus sp. is prismatic with Hunter-Schreger bands (HSB) and an outer zone of radial enamel. In the basilosaurid, the enamel is relatively thin and measures 150-180 µm, whereas in Llanocetus sp. it is considerably thicker, measuring 830-890 µm in the cusp area and 350-380 µm near the crown base. This is one of the thickest enamel layers among cetaceans, extinct and living. Structures resembling enamel tufts and lamellae were observed in both fossils at the enamel-dentine junction (EDJ) and extending along the thickness of the enamel layer, respectively. The presence of HSB and biomechanical reinforcing structures such as tufts and lamellae suggest prominent occlusal loads during feeding, consistent with raptorial feeding habits. Despite the simplification or complete absence of teeth in modern cetaceans, their ancestors had complex posterior teeth typical of most mammals, with a moderately thick enamel layer with prominent HSB. Full text is available at: https://link.springer.com/article/10.1007/s10914-018-09456-3 Or alternatively, a *pdf* can be requested at: carolina.l...@otago.ac.nz Best regards, _______________________________________ Carolina Loch Silva, PhD Lecturer in Oral Biology Department of Oral Sciences Sir John Walsh Research Institute Faculty of Dentistry, University of Otago Dunedin 9054, New Zealand Phone: +(64) 03 479-9255 http://www.otago.ac.nz/sjwri/people/profile/index.html?id=2033
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