Oryctodromeus burrow and Brazil pterosaurs in Palaios

[bh480@scn.org]

From: Ben Creisler
bh480@scn.org

Abstracts for the March 2011 issue of Palaios are online 
at
http://paleo.ku.edu/palaios/26/3/mar11.html

Two may interest DML members:

D. Cary Woodruff and David J. Varricchio (2011)
Experimental modeling of a possible Oryctodromeus 
cubicularis (Dinosauria) burrow. 
PALAIOS 26:140?151 (2011)
DOI: 10.2110/palo.2010.p10-001r 


The hypsilophodont Oryctodromeus cubicularis from the 
Cretaceous Blackleaf Formation of Montana represents the 
first dinosaur interpreted to be from a burrow fill. The 
skeletal remains occurred within an incompletely 
preserved chamber at the end of an S-shaped tunnel. 
Unlike many fossil vertebrates associated with burrows, 
the Oryctodromeus remains were disarticulated and 
elevated within the graded fill. To test whether this 
skeletal arrangement reflected in situ burial from within 
or transport into the burrow, we constructed a half-scale 
burrow model using PVC pipes and conducted a series of 
sediment infilling experiments with appropriately scaled, 
disarticulated rabbit skeletons. Experimental trials 
varied incoming flow velocities, sediment supply, dry or 
water-filled chamber conditions, and initial placement 
and weight of skeletal elements. Twelve of the 13 trials 
resulted in complete rearrangement of the skeletons, six 
trials left bones elevated above the base of the chamber 
floor, and six resulted in graded fills. Only the trial 
using saturated bones preserved the skeleton largely 
undisturbed on the chamber floor. A trial using bones 
mixed with the sediment prior to deposition resulted in 
numerous broken elements but did not produce a 
distinctive bone distribution. Several trials produced 
bone distributions and sediment fills similar to the 
original Oryctodromeus burrow assemblage. The experiment 
as designed failed to falsify the hypothesis that the 
Oryctodromeus bones were in the chamber prior to burial. 
Experimental results include bone and sediment 
configurations similar to those known from the vertebrate 
fossil record and the former may prove useful in the 
recognition of burrow assemblages lacking a distinctive 
fill. 
 

Bruno C. Vila Nova, Antonio A. F. Saraiva, Joao K. R. 
Moreira, and Juliana M. Sayao (2011)
Controlled excavations in the Romualdo Formation 
Lagerstätte (Araripe Basin, Brazil) and pterosaur 
diversity: Remarks based on new findings. 
PALAIOS 26: 173?179  (2011)
Research Note 
DOI: 10.2110/palo.2010.p10-072r 
 

Because of its fossil abundance and exceptional 
preservation, the Romualdo Formation of the Santana Group 
has become a famous lithostratigraphic unit of the 
Araripe Basin. In the past decades, much research has 
been conducted on the vertebrates of this unit, 
especially fish and pterosaurs, based mainly on museum 
collections. Despite the importance of these fossil 
finds, no stratigraphic information is known about them, 
because until recently, locals have collected most of the 
fossils. Here we present the results of the third 
controlled excavation of these layers. The data from all 
fossils collected confirm a faunal succession of fish 
biota. In the upper and most fossiliferous layer, the 
faunal composition shows a pattern of fish distribution 
never observed before, indicating that previous 
categories (abundance versus diversity) do not include 
the total diversity of fish populations. Pterosaur 
remains were recorded for the first time in the field, 
contradicting the general idea that these volant reptiles 
are common in the Romualdo strata. The specimen was 
attributed to the clade Anhangueridae because the 
proportional length of the first wing phalanx is less 
than twice the length of the wing metacarpal. The 
controlled excavation showed that the pterosaur 
assemblages from this formation probably occur in 
clusters. The known abundance of pterosaurs in the 
Romualdo Formation has been biased by just a few sites of 
fossil extraction, and these reptiles do not appear to 
have been as widespread or abundant as previously 
thought.