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Dinosaur tracks, limb mechanics, and digital reconstruction



From: Ben Creisler
bh480@scn.org

Some new papers and book chapters that may not have been mentioned yet:

Avanzini, M., Piñuela, L. & García-Ramos, J.C. (2011) 
Late Jurassic footprints reveal walking kinematics of theropod dinosaurs. 
Lethaia (advance online publication) 
DOI: 10.1111/j.1502-3931.2011.00276.x
http://onlinelibrary.wiley.com/doi/10.1111/j.1502-3931.2011.00276.x/abstract

This study describes a set of theropod footprints collected from the Late
Jurassic Lastres Formation (Asturias, N Spain). The footprints are natural
casts (tracks and undertracks) grouped into three morphotypes, which are
characterized by different size frequency, L/W relationship and
divarication angles: 'Grallatorid' morphotype, 'Kayentapus?Magnoavipes'
morphotype, 'Hispanosauropus' morphotype. The tracks were produced in firm,
stiff and soft sediments. The infills of deep tracks, which are typically
formed in soft mud, lack fine anatomical details, but they can reveal the
walk kinematics of the trackmaker through the morphology of internal track
fills and sinking traces. In all footprints, a horizontal outwardly
directed translation movement and rotation are recognizable. The amount and
geometry of digit penetration in the ground also show a pronounced
difference. It can be inferred from the described sample that different
theropoda-related ichnogenera share common kinematics.
==

John R. Hutchinson (2011)
On the inference of function from structure using biomechanical modelling
and simulation of extinct organisms.
Biology Letters (advance online publication)
doi: 10.1098/rsbl.2011.0399 
http://rsbl.royalsocietypublishing.org/content/early/2011/06/08/rsbl.2011.03
99.abstract

Biomechanical modelling and simulation techniques offer some hope for
unravelling the complex inter-relationships of structure and function
perhaps even for extinct organisms, but have their limitations owing to
this complexity and the many unknown parameters for fossil taxa. Validation
and sensitivity analysis are two indispensable approaches for quantifying
the accuracy and reliability of such models or simulations. But there are
other subtleties in biomechanical modelling that include investigator
judgements about the level of simplicity versus complexity in model design
or how uncertainty and subjectivity are dealt with. Furthermore,
investigator attitudes toward models encompass a broad spectrum between
extreme credulity and nihilism, influencing how modelling is conducted and
perceived. Fundamentally, more data and more testing of methodology are
required for the field to mature and build confidence in its inferences. 
[Tyrannosaurus hindlimb posture as example]

==
(mentioned on the DML back in Novemenber, but now officially published with
name Corpulentapus)
Rihui Li, Martin G. Lockley, Masaki Matsukawa, , Kebai Wang and Mingwei Liu
(2011)
An unusual theropod track assemblage from the Cretaceous of the Zhucheng
area, Shandong Province, China.
Cretaceous Research 32(4): 422-432
doi:10.1016/j.cretres.2010.10.006 
http://www.sciencedirect.com/science/article/pii/S0195667110000960

More than 125 footprints of theropods from the Cretaceous Longwangzhuang
Formation have been mapped in a preliminary study at a site in the Zhucheng
region of China. The tracks represent at least three morphotypes. The
largest morphotype is a large theropod (footprint length 30 cm) represented
by a single trackway and an isolated natural cast. At least 10 trackways
assigned to the new ichnospecies Corpulentapus lilasia represent a
medium-sized biped (footprint length 13 cm) with very short, wide, robust,
?tulip-shaped? tracks and long steps (5 × footprint length), and a short
central digit (III) indicating weak mesaxony. Corpulentapus trackways are
narrow and theropod-like even though track morphology is convergent with
the footprints of some ornithopods. The third morphotype, made by a
medium-sized grallatorid track maker (ichnogenus Paragrallator), is about
the same size (13 cm) as the robust morphotype, but far more elongate and
gracile, with an elongate central digit (III) indicating strong mesaxony.
This ichnotaxon requires detailed comparison with Grallator sensu stricto.
The contrast in morphology between the two common morphotypes is striking
and demonstrates that two distinct medium-sized taxa of presumed theropod
affinity frequented the same habitat in significant numbers.

==
>From the book Computational Paleontology:

Heinrich Mallison (2011)
Digitizing Methods for Paleontology: Applications, Benefits and
Limitations. 
in Computational Paleontology: 7-43
DOI: 10.1007/978-3-642-16271-8_2 
http://www.springerlink.com/content/m3w2p3l880033857/

Over the course of the last decades computers have evolved from a useful
tool for rapidly calculating large amounts of equations to an indispensable
part of everyday life. Today, cars will not run if a chip is faulty, and
communication not only by phone and email, but also by conventional mail
depends on computer codes. Computer generated or edited sounds and images
dominate advertising, and their influence on education and especially
entertainment is rapidly growing. 
[Ditigal images of Plateosaurus bones)]


Stefan Stoinski (2011)
>From a Skeleton to a 3D Dinosaur.
in Computational Paleontology: 147-164
DOI: 10.1007/978-3-642-16271-8_8 
http://www.springerlink.com/content/v2jx0712057lj422/
bigger preview at:
http://www.springerlink.com/content/978-3-642-16270-1/#section=864766&page=1
&locus=0


What dinosaurs really looked like is (and has always been) of great
interest to most people, ever since the first skeletons were found.
Reconstruction methods changed over time, and the better the understanding
of the anatomy of these animals is, the better are usually the
reconstructions. If the body mass it known, it is possible to derive many
physiological data, which in turn improve our understanding of the way of
life of these extinct animals. A simple method of estimating the weights of
dinosaurs is by reconstructing the body surface area, calculating the body
volume, and estimating the body mass for all body parts using specific
weights based on analogies to extant animals. The developmental path of a
reconstruction, from a mounted skeleton to a scientific realistic looking
digital dinosaur, will be detailed in this chapter. Initially, a mounted
skeleton is laser scanned to derive a non-scaled 3D point cloud. The second
step is to reconstruct the external shape of the living animal, and thus
the body surface area, using special software. This can be done by using
non-uniform rational B-splines (NURBS). Next, the modeled dinosaur should
be assessed for plausibility by physiologists, to check the fit of the
interior organs. When necessary the model must be adapted. This can be an
iterative process, and sometimes many changes must be realized to arrive at
an acceptable result. This method results in editable and decidedly more
accurate models of dinosaurs, which deliver significantly better data on
physiological parameters than classic methods. 
[Giraffatitan as example]



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