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Re: Australian Lark Quarry dinosaur stampede trigger scenario unlikely

Popular summary of new work:


From: Ben Creisler <bcreisler@gmail.com>
To: dinosaur@usc.edu 
Sent: Wednesday, 9 July 2014 12:17 AM
Subject: Australian Lark Quarry dinosaur stampede trigger scenario unlikely

Ben Creisler

A new paper:

Anthony Romilio & Steven W. Salisbury (2014)
Large dinosaurian tracks from the Upper Cretaceous
(Cenomanian–Turonian) portion of the Winton Formation, Lark Quarry,
central-western Queensland, Australia: 3D photogrammetric analysis
renders the ‘stampede trigger’ scenario unlikely.
Cretaceous Research 51: 186–207
DOI: 10.1016/j.cretres.2014.06.003

The largest Lark Quarry dinosaur tracks were examined using 3D protocols.
Many track specimens indicate only minor deterioration since excavation.
Most original outlines do not resemble actual track morphology.
Overprinted traces suggest long time lags between large and many small
Track succession allows for no interaction amid these different sized

The largest dinosaurian tracks at Lark Quarry, central-western
Queensland, Australia, were re-examined using revised analytical
protocols that incorporate three-dimensional (3D) structure.
Comparisons were made with archival photographs, replica specimens (c.
1977) and the in situ tracks (2013) to account for changes to the
track surface. Damage caused both during and after the excavation of
the tracks was evident, and in cases where the archival photographs
and 1970's replicas strongly differ from the in situ tracks, it is
apparent that restoration has modified the original track morphology.

Even after accounting for recent damage and alteration, several of the
track morphologies obtained from new 3D evaluation models differ
considerably from the track outlines that were published in the
original description of the site
ginal outlines seem to represent
simpler, stylized versions of the tracks. A number of the original
outlines are >20% larger than the in situ tracks, while others appear
to incorporate cracks as part of the margin of digit impressions.
Overall, the best-preserved tracks show blunt digit impressions,
reaffirming the idea that the trackmaker was a large ornithopod and
supporting a reassignment to cf. Iguanodontipus. The new analysis also
reveals the nature of the displacement rims associated with the
tracks, and the overprinting of these rims by other ichnites—initially
by tool marks (presumably caused by floating vegetation) and then by
other dinosaurian tracks (assignable to Wintonopus latomorum). In the
context of these observations, we see no evidence for an interaction
between the cf. Iguanodontipus trackmaker and the smaller-bodied W.
latomorum trackmakers, as neither can be inferred to have been present
at the tracksite at, or even close to the same time. Similarly, there
is no evidence to support the idea that the approach of the cf.
Iguanodontipus trackmaker in some way triggered the movement of the W.
latomorum trackmakers. Rather than a snap-shot of dinosaurian
‘stampede’, this study supports the idea that Lark Quarry most likely
represents a complex time-averaged assemblage of multiple dinosaurian
ichnites, preserved over an extended period of time (hours to days)
and bracketed by discrete phases of trackmaker activity and
fluctuations in water depth.