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Dyrosaurid (Crocodylomorpha) bone histology and lifestyle



Ben Creisler
bcreisler@gmail.com

New in PLoS ONE:

Rafael César Lima Pedroso de Andrade & Juliana Manso Sayão (2014)
Paleohistology and Lifestyle Inferences of a Dyrosaurid (Archosauria:
Crocodylomorpha) from Paraíba Basin (Northeastern Brazil).
PLoS ONE 9(7): e102189.
doi:10.1371/journal.pone.0102189
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0102189


Among the few vertebrates that survived the mass extinction event
documented at the Cretaceous–Paleocene boundary are dyrosaurid
crocodylomorphs. Surprisingly, there is little information regarding
the bone histology of dyrosaurids, despite their relatively common
occurrence in the fossil record, and the potential to gain insight
about their biology and lifestyle. We provide the first description of
the long bone histology of the dyrosaurids. Specimens were collected
from the Maria Farinha Formation, in the Paraíba Basin of northeast
Brazil. Thin sections of a right femur and left tibia were made. In
the left tibia, the cortex consists of lamellar-zonal bone with five
lines of arrested growth (LAGs), spaced ~300 µm apart. The tibia
contains a small to medium-sized organized vascular network of both
simple vascular canals and primary osteons that decrease in density
periostially. The femur exhibits a similar histological pattern
overall but has double-LAGs, and an EFS layer (the latter is rare in
living crocodylians). Secondary osteons occur in the deep cortex near
and inside the spongiosa as a result of remodeling in both bones. This
tissue pattern is fairly common among slow-growing animals. These
specimens were a sub-adult and a senescent. Patterns in the
distribution of bone consistent with osteosclerosis suggest that these
animals probably had a fast-swimming ecology. Although these results
are consistent with the histology in anatomically convergent taxa, it
will be necessary to make additional sections from the mid-diaphysis
in order to assign their ecology.