[MARMAM] New paper on enamel microstructure of fossil mysticetes and archaeocetes

Carolina Loch Silva lochcarolina at gmail.com
Sun Jan 20 15:06:07 PST 2019


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.loch at 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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