INVESTIGADORES
POL Diego
congresos y reuniones científicas
Título:
Enamel microstructure of theropod theeth: a characterization of specimens from the Cretaceous of Patagonia
Autor/es:
GIANECHINI, F.; POL, D.
Lugar:
San Juan
Reunión:
Congreso; IV Congreso Latinoamericano de Paleontología de Vertebrados; 2011
Resumen:
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The enamel is the
mineralized tissue that covers the amniote teeth, whose microstructure is
constituted by microcrystals of apatite arranged in a particular order (Sander,
1999; Stokosa, 2005). In mammals, these microcrystals are organized in such a way that they form prism-like structures (Sander,
1999). The mammalian enamel can be easily observed under polarized light.
Conversely, the enamel of reptiles (including
dinosaurs) is not prismatic, and therefore only can be observed through
scanning electron microscope (SEM) (Sander, 1999, 2000; Hwang, 2005; Stokosa,
2005). Observations on theropod enamel were principally performed on Laurasian
taxa (e.g., Allosaurus, Tyrannosaurus, Velociraptor, Troodon,
Sander, 1999; Stokosa, 2005) and only in a few Gondwanan taxa (e.g., Carcharodontosaurus, Spinosaurus, Buffetaut et al., 1986). Recent research has revealed
that, despite the convergence observed in the microstructure of theropod
enamel, many monophyletic groups have a characteristic type of enamel and,
therefore, the enamel microstructure can be phylogenetically informative, at
least at the family level (Hwang, 2005). A characterization of isolated teeth
from the Cerro Barcino Formation (Aptian-Albian?) of Chubut Province, that have
morphological similarities with abelisaurid, carcharodontosaurid, and dromaeosaurid
teeth, is here presented, complementing previous studies on Gondwanan taxa.
Additionally, studies on the enamel microstructure of Tyrannotitan chubutensis Novas, De Valais, Vickers-Rich and Rich,
2005 is also presented here. Isolated teeth that morphologically resemble
either abelisaurid or carcharodontosaurid teeth, the microcrystals are arranged
in columns in the basal half of the enamel and in a parallel arrangement along
the outer half, with incremental lines, as is observed in the enamel microstructure
of the tyrannosaurid and carcharodontosaurid teeth. Isolated teeth
morphologically similar to dromaeosaurid teeth have their enamel mainly
constituted by parallel crystals, some also showing incremental lines,
resembling the microstructure of troodontids and dromaeosaurids. The enamel of Tyrannotitan is columnar, as in Carcharodontosaurus, but conversely to
the latter, incremental lines predominates in the basal half. Thus, studies
based on enamel microstructure are important not only for complement studies of
theropod teeth, but also for identifying the phylogenetic affinities of
isolated theropod teeth found in Cretaceous units of Gondwana.
