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Pelagornis pseudoteeth structure and growth

From: Ben Creisler

Non-Mesozoic but of interest in PLoS ONE:

Antoine Louchart, Jean-Yves Sire, Cécile Mourer-Chauviré, Denis
Geraads, Laurent Viriot & Vivian de Buffrénil (2013)
Structure and Growth Pattern of Pseudoteeth in Pelagornis mauretanicus
(Aves, Odontopterygiformes, Pelagornithidae).
PLoS ONE 8(11): e80372.

The extinct Odontopterygiformes are the sole birds known to possess
strong and sharp bony pseudoteeth, the shape and location of which are
closely mimetic of real teeth. The structure of the pseudoteeth is
investigated here in a late Pliocene/early Pleistocene species,
Pelagornis mauretanicus, using X-ray microtomography and thin
sections. The results are interpreted with regard to the pseudotooth
mode of growth, and have implications concerning aspects of Pelagornis
ecology. The larger pseudoteeth are hollow and approximately
cone-shaped, and the smaller ones are rostro-caudally constricted. The
walls of pseudoteeth are composed of bone tissue of the fibro-lamellar
type, which is intensively remodeled by Haversian substitution. The
jaw bones display the same structure as the pseudoteeth, but their
vascular canals are oriented parallel to the long axis of the bones,
whereas they are perpendicular to this direction in the pseudoteeth.
There is no hiatus or evidence of a fusion between the pseudoteeth and
the jaw bones. Two possible models for pseudotooth growth are derived
from the histological data. The most plausible model is that
pseudotooth growth began after the completion of jaw bone growth, as a
simple local protraction of periosteal osteogenic activity.
Pseudotooth development thus occurred relatively late during ontogeny.
The highly vascularized structure and the relative abundance of
parallel-fibered bone tissue in the pseudoteeth suggest poor
mechanical capabilities. The pseudoteeth were most likely covered and
protected by the hardened, keratinized rhamphotheca in the adult
during life. The late development of the pseudoteeth would involve a
similarly late and/or partial hardening of the rhamphotheca, as
displayed by extant Anseriformes, Apterygiformes and some
Charadriiformes. This would add support to the hypothesis of a close
phylogenetic relationship between Odontopterygiformes and
Anseriformes. The late maturation of the Pelagornis feeding apparatus,
and hence the delayed capability for efficient prey catching, suggests
that Pelagornis was altricial.