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Triassic burrows in Ischigualasto Basin, Argentina

From: Ben Creisler

Another new paper in PLoS ONE that might interest some:

Carina E. Colombi, Eliana Fernández, Brian S. Currie, Oscar A.
Alcober, Ricardo Martínez & Gustavo Correa (2012)
Large-Diameter Burrows of the Triassic Ischigualasto Basin, NW
Argentina: Paleoecological and Paleoenvironmental Implications.
PLoS ONE 7(12): e50662.

Large-diameter ichnofossils comprising three morphotypes have been
identified in the Upper Triassic Ischigualasto and Los Colorados
formations of northwestern Argentina. These burrows add to the global
record of the early appearance of fossorial behavior during early
Mesozoic time. Morphotypes 1 and 2 are characterized by a network of
tunnels and shafts that can be assigned to tetrapod burrows given
similarities with previously described forms. However, differences in
diameter, overall morphology, and stratigraphic occurrence allow their
independent classification. Morphotype 3 forms a complex network of
straight branches that intersect at oblique angles. Their calcareous
composition and surface morphology indicate these structures have a
composite biogenic origin likely developed due to combined
plant/animal interactions. The association of Morphotypes 1 and 2 with
fluvial overbank lithologies deposited under an extremely seasonal
arid climate confirms interpretations that the early appearance of
burrowing behavior was employed by vertebrates in response to both
temperature and moisture-stress associated with seasonally or
perpetually dry Pangean paleoclimates. Comparisons of burrow
morphology and biomechanical attributes of the abundant
paleovertebrate fauna preserved in both formations permit
interpretations regarding the possible burrow architects for
Morphotypes 1 and 2. In the case of the Morphotype 1, the burrow
constructor could be one of the small carnivorous cynodonts,
Ecteninion or Probelesodon. Assigning an architect for Morphotype 2 is
more problematic due to mismatches between the observed burrow
morphology and the size of the known Los Colorados vertebrates.