[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
RE: Photoshopping Techniques and Tracing
I'd just like to say I agree with what Jaime has said here. Furthermore,
the photos of these compressed fossils can be downright misleading in
respect to morphology. I thought I had found a naris in Protarchaeopteryx,
for instance. It was in the right place for an oviraptorosaur, but personal
communication with Phil Senter revealed it to be something else entirely.
Personal examination is key.
From: "Jaime A. Headden" <email@example.com>
CC: David Peters <firstname.lastname@example.org>
Subject: Photoshopping Techniques and Tracing
Date: Mon, 30 Jan 2006 18:51:40 -0800 (PST)
Paul Sparks' comments and Tim's consideration of a method, as well as
conversations about the viability of reproducing the method David Peters
used to infer his reconstructions and findings, has needed some back up.
Marjanovic took some portions of Dave's reference material and found some
irregularities, as has Chris Bennett.
Furthermore, Silvio Renesto has reconstructed the skull of
and has not reproduced Dave's findings in this animal. Dave's
can be found here:
While that of Renesto can be found in Renesto and Dalla Vecchia:
Renesto, S. & F. M. Dalla Vecchia. 2005. The skull and lower jaw
of the holotype of *Megalancosaurus preonensis* (Diapsida,
Drepanosauridae) from the Upper Triassic of northern Italy.
_Rivista Italiana di Paleontologia e Stratigrafia_
To which Dave has responded about issues detracting from that
due to a differently interpreted dorsal braincase:
This shows two quite similar techniques arriving at very different
conclusions, such that Renesto recovers a narrow L-shaped frontal and no
antorbital fenestra, while Dave finds a broad trapezoidal frontal and a
distinct frontal. There are many problems with dealing with the dolomitic
Triassic fossils of Italy, in that some slabs (the holotype of
preonensis* is no exception, but educational in this regard) are split
unevenly, not perfectly, so portions of both sides of the bone inclusions
up on both slabs, and in this case, we have the posterior processes of the
premaxillae on both sides of the skull clearly paired, as are most other
in the skull, which has led to Dave inferring a space between them by
interpreting both of these processes as belonging to the same side of the
skull. This conclusion does not arise because of the methodology, but
of the interpretation of the material that is drawn from it, so one should
fault Photoshop for the effectiveness, merely a consideration of the
Photoshopping to develop some ability to determine what a flattened slab
might show can be used in various corners, for various purposes. Mickey
Mortimer here has used it to outline the skulls of various Liaoning birds,
a general aversion to over interpreting features in the bone, for the sake
finding general bone shape, which for his purposes is to determine general
measurements and qualities of the skull. Here is *Abberatiodontus*:
and a dinosaur, *Sinosauropteryx*:
Finally, I have also used Photoshop and to some high resolution to
the shapes and inclusions onto a "tracing" so as to evaluate it without the
distracting shapes around it on the slab.
In this illustration, I have collected images of some high (and some lo)
illustrations and photographs of the mainslab of the Berlin *Archaeopteryx*
order to consider the question of a preserved propatagium, the
of crack features, feather impressions, and tooling traces, which will all
obscure one another. As I hope to show, there probably IS a propatagium,
line of feathers across the shoulder to the mid-forearm on both sides, the
left-hand wing is covered in oblique tooling traces likely used to remove
surface limestone from the impression surface, and the impressions of both
flight feathers and coverts, some of which cross over the forearm and might
actually be secondaries that have been deflected from below the arm to up
over it. Such things happen with extant bird carcasses I have observed, and
this animal should be no different. Finally I should note that Darren
who's illustration I have "borrowed", has also seen these features, and
are illustrated to support this consideration.
Using this technique is valuable as it gives you a different way to look
the material; the problem arises from expecting too much from what you see,
using it for anything more than a presentation. All of the features I
I could see with the naked eye without the aid of Photoshop, and I used no
lighting or resolution or contrast changes to draw on these photos, and use
them only to illustrate what I saw without such "aids".
I have seen other fossils with odd associations of bones, and have
to tease out their shapes in order to better understand them, such as the
of *Scansoriopteryx heilmanni*, and have done a Mickey Mortimer-style
to make these observations cohesive. Nonetheless, he and I have seen the
slab and come to different conclusions about the material, and this
comes only from the a posteriori observation and interpretation, and not
what's actually on the slab or what can be seen (we both admit to seeing
same impressions, the same knobs and thingamajigs). The only answer is that
see the end conclusions differently, and this comes from experience and
interpretation of data, which tends to be very subjective. So I hardly
I'm right on this matter.
The only conclusions in these practices that I can conclude is that we
not be using the tracings as a fact-finder; they are an illustrative
only, and given access to the actual fossils, I would never use them to
anything. I did have access to a cast of *Longisquama* once, and the nature
the slab's irregular fracture plane shows me what a flat plate could never
done, and I offer this as a cautionary tale.
In this, looking at the actual slab, I cannot for the life of me see any
extensive digits coiled around the bottom of the slab. I have looked. When
had access to the cast, I put my face nearly touching it to peer for the
missing material Dave has seen, and I cannot for the life of me find them.
conclusion to date can only be that they are not there, and I have no other
reason to assume this except that they do not appear to be present in any
distinct form, nor can I figure why the arm and manus as preserved, which
others have illustrated, can possibly offer further material with
and vague impressions.
Jaime A. Headden
"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around