Geoscience Reference
In-Depth Information
comparisons with other known dinosaur skeletons, and we were ready
to write a scientific paper to announce our discovery. The article not
only named the new abelisaur but also described several important
anatomical features that had previously been unknown in abelisaurs.
Aucasaurus
is the most complete abelisaur skeleton ever collected and
provides new insights into the evolution of this peculiar lineage of
horned carnivores. Our paper was submitted to the primary scientific
journal that publishes information about new research in vertebrate
paleontology.
Beyond describing and naming the new dinosaur, we were still
faced with one other mystery concerning this individual. How had it
died? Once again, some clues were preserved in the rocks that
entombed the specimen.
The rock that had produced the skeleton was unusual because no
other layers at the site were quite like it. The skeleton was found in
finely banded, purplish gray mudstone, and upon closer inspection,
Lowell discovered that these laminations also contained small fossils
of shelly invertebrates. Finely banded layers of mudstone are often
deposited on the bottom of shallow lakes, ones that could easily
have formed on the floodplain after storms. Similar layers can be
observed forming on the bottom of many lakes today. We could once
again use a geologic process that we see operating today to interpret
how the banded mudstone formed 80 million years ago at Auca
Mahuevo. Clearly, the carcass had been buried at the bottom of a shal-
low lake on the floodplain. Either the predator had died in the lake or
its carcass had floated out into the lake before sinking to the bottom
and being buried. Because part of its skull was broken apart, perhaps
it had gotten in a fight and been killed when another dinosaur bit or
struck its head. But at this point, we simply cannot be certain about
the cause of death. Only further study of the bones might help
answer that mystery.
