[MARMAM] New paper on the enamel ultrastructure in fossil cetaceans

Carolina Loch carolinaloch at yahoo.com.br
Thu Jan 29 13:42:36 PST 2015


Dear MARMAM subscribers, We are pleased to announce the publication of the following paper inPLOS One:  Loch C, Kieser JA, Fordyce RE (2015) Enamel Ultrastructure in Fossil Cetaceans(Cetacea: Archaeoceti and Odontoceti). PLoS ONE 10(1): e0116557. doi:10.1371/journal.pone.0116557  AbstractThe transition from terrestrial ancestry to a fully pelagic life profoundlyaltered the body systems of cetaceans, with extreme morphological changes inthe skull and feeding apparatus. The Oligocene Epoch was a crucial time in theevolution of cetaceans when the ancestors of modern whales and dolphins(Neoceti) underwent major diversification, but details of dental structure andevolution are poorly known for the archaeocete-neocete transition. We reportthe morphology of teeth and ultrastructure of enamel in archaeocetes, andfossil platanistoids and delphinoids, ranging from late Oligocene (WaitakiValley, New Zealand) to Pliocene (Caldera, Chile). Teeth were embedded in epoxyresin, sectioned in cross and longitudinal planes, polished, etched, and coatedwith gold palladium for scanning electron microscopy (SEM) observation. SEMimages showed that in archaeocetes, squalodontids and Prosqualodon (taxa withheterodont and nonpolydont/limited polydont teeth), the inner enamel wasorganized in Hunter-Schreger bands (HSB) with an outer layer of radial enamel.This is a common pattern in most large-bodied mammals and it is regarded as abiomechanical adaptation related to food processing and crack resistance.Fossil Otekaikea sp. and delphinoids, which were polydont and homodont, showeda simpler structure, with inner radial and outer prismless enamel. Radialenamel is regarded as more wear-resistant and has been retained in severalmammalian taxa in which opposing tooth surfaces slide over each other. Theseobservations suggest that the transition from a heterodont and nonpolydont/limitedpolydont dentition in archaeocetes and early odontocetes, to homodont andpolydont teeth in crownward odontocetes, was also linked to a markedsimplification in the enamel Schmelzmuster. These patterns probably reflectfunctional shifts in food processing from shear-and-mastication in archaeocetesand early odontocetes, to pierce-and-grasp occlusion in crownward odontocetes,with the implication of less demanding feeding biomechanics as seen in mostextant odontocetes.

Full text is available at:

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0116557

Or alternatively, a pdf can be requested at: carolina.loch at otago.ac.nz  Best regards, ________________________________________
Carolina Loch Silva, PhD
Research Assistant
Sir John Walsh Research Institute
Faculty of Dentistry, University of Otago
Dunedin 9054, New Zealand
Phone: +(64) 03 479-5667
&
Research Collaborator
Geology Department, University of Otago
and
Laboratório de Mamíferos Aquáticos UFSC
Florianópolis, SC - Brasil

http://www.otago.ac.nz/sjwri/people/craniofacial-biomechanics/otago054438.html
 
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