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Re: Australian dinosaur "stampede": identity of large track-maker



Dann: If you read the abstract alone it may seem like an ad hominem,
but Thulborn does focus on the method, not the men, in the paper (and
in the abstract, mostly), so I think his critique is sound.

David: It's strong wording, but if you replace "fabricated" with
"extrapolated" it doesn't capture what Thulborn is getting at - that
the heels of the footprints were reconstructed, seemingly without
basis, to act as crucial data points in a multivariate analysis.

Regarding this version (2013) of Thulborn's paper, the most notable
discrepancy between it and the previous Cretaceous Research version
(2011) is the omission of the closing paragraph:

"Finally, it is pertinent to mention that Romilio and Salisbury may
have a special interest in overturning the existing interpretation of
Lark Quarry. They did not disclose that one of them (AR) is
undertaking a reappraisal of the Lark Quarry dinosaur tracks as a PhD
research project supervised by the second author (SWS). If the
findings of that research were merely to corroborate the existing
interpretation of Lark Quarry, they might seem to lack the originality
required to justify the award of a degree. In other words, it might
seem imperative that these authors should find and repair substantial
faults in the existing interpretation or, better still, that they
should overturn it completely and introduce an entirely new
interpretation."

I actually think this is a fair contention, though not an argument in
itself against the conclusions made by Romilio and Salisbury. For this
PhD project to have been instigated and undertaken, the authors would
essentially have had to take up the position that the stampede
interpretation presented by Thulborn and Wade (1984) was partially or
totally incorrect or incomplete.

I have many more problems with Romilio and Salisbury's (2011, 2013)
interpretations of the Lark Quarry track site than I do with Thulborn
and Wade's (1979, 1984). Regarding Romilio and Salisbury (2013)
specifically:

1) The synonymisation of Wintonopus and Skartopus was made on the
basis that “some” deeper footprints of Wintonopus appear to have
Skartopus-like footprints within them and vice versa. Romilio and
Salisbury's Figure 11, which is the only figure cited as showing
Wintonopus footprints within Skartopus footprints is far from
convincing - the middle toe is incredibly long compared to the
holotype (Figure 9). No scale bars are included in the supplementary
figures, meaning that meaningful comparisons are not really possible.
With respect to the opposite situation, i.e. Skartopus tracks within
Wintonopus tracks, maybe some of the (smaller) Skartopus trackmakers
happened to step within the footprints of the (larger) Wintonopus
trackmakers because a lot of animals were running, all at the same
time, maybe in a stampede? It cannot be denied, for example, that some
Skartopus tracks overprint the Tyrannosauropus tracks (Thulborn &
Wade, 1984: Pl.17)...

2) The idea of having four differently sized track generators making
tracks at times of four different (and convenient) water levels seems
to be a contortion act to fit the data to a preconceived notion, i.e.
that the majority of the footprints (excluding the two larger
ornithopod sets and the large theropod/ornithopod set) were not made
at the same time; i.e. that the interpretation of Thulborn and Wade is
incorrect. Just how rapidly was the water level changing, and what
sedimentological evidence is there of such rapid and repeated changes?
If the water level was changing so much, and the environment was a
high-energy one, why are the footprints so coherent? They look more
like footprints made in fresh, ready-to-set cement than footprints
made in subaqueous conditions.

3) Why would so many of the tracks be so deep if they are swimming
traces? The depth of the footprints seems to suggest that the majority
of these animals were not being supported by very much (if any) water
at all. And the depth of the tracks is probably only able to be
under-estimated (due to incomplete removal of sediment) rather than
over-estimated, so the majority are probably deeper than they appear.

4) The method for determining that a series of footprints were made by
a single individual is not clear. There are a _lot_ of footprints at
this site - I have seen it, and it would take a lot of work to discern
the precise number of trackmakers, let alone the footprints which
comprise individual series.

5) Finally, the idea of a ”mixed herd” of ornithopods and theropods is
not an issue for three reasons:
a) If the Skartopus trackmakers were theropods, this does not
necessarily imply that they were carnivorous
b) If the Skartopus trackmakers were carnivorous theropods, they were
clearly (on average) smaller animals than the Wintonopus trackmakers
and probably would not have been a threat;
c) If the Skartopus trackmakers were carnivorous theropods, and were a
threat to the Wintonopus trackmakers, and if the Tyrannosauropus
trackmaker was a hungry theropod, then all small trackmakers were
panicking and would have had escape rather than food as their
immediate objective.

The last paragraph of Romilio and Salisbury's discussion (page 116),
where the authors claim that they may be viewed as “iconoclasts” by
some scientists and members of the public for presenting a different
interpretation of this site is spot on (and will now seem prescient
based on the "official" publication dates of Romilio and Salisbury
(January 8, 2013) and Thulborn (January 29, 2013). However, it is spot
on for the wrong reasons. They probably will be viewed as such, not
because of their conclusions per se, but because of the way in which
their interpretations were presented, and the methods which were
employed to arrive at their conclusions. In general, if the aim is to
overturn a scientifically well-supported, parsimonious interpretation,
it must be done properly. Thulborn has called Romilio and Salisbury
out on their methodology, and I think he is justified in doing so.
Undermine the method and you undermine the interpretation.

Presently, I am of the opinion that Thulborn and Wade's interpretation
is still better-supported by the data, supported by more rigorous
science, and more parsimonious than the interpretation made by Romilio
and Salisbury. It has distressed me greatly to see various media
sources and blogs accepting Romilio and Salisbury's papers'
conclusions essentially uncritically and without contacting any other
palaeontologists for their two cents or referring explicitly to
Thulborn and Wade's papers.

If I am in error in any of my statements / questions / whatever,
please let me know. I would like our version of the events that led to
the formation of Lark Quarry to be as close to the actual events as
possible.

Cheers,

Steve

On Wed, Jan 30, 2013 at 3:23 PM, David Marjanovic
<david.marjanovic@gmx.at> wrote:
>
> > Those iconoclastic claims are examined here and are shown
> > to be groundless: they are based partly on misconceptions and partly
> > on fabricated data that have been assessed uncritically using
> > quantitative measures of questionable significance.
>
> Fabricated data?
>
> What the vertical gene transfer?




--
Dr. Stephen Poropat

Postdoctoral Research Fellow
Uppsala University
Villavägen 16
SE-752 36 Uppsala
Sweden

Research Associate
Australian Age of Dinosaurs
PO Box 408
Winton 4735
Australia