Compsognathus and Juravenator taphonomy

[Ben Creisler <bcreisler@gmail.com>]

From: Ben Creisler
bcreisler@gmail.com


A new online paper:


Achim G. Reisdorf and Michael Wuttke (2012)
Re-evaluating Moodie’s Opisthotonic-Posture Hypothesis in Fossil
Vertebrates Part I: Reptiles—the taphonomy of the bipedal dinosaurs
Compsognathus longipes and Juravenator starki from the Solnhofen
Archipelago (Jurassic, Germany).
Palaeobiodiversity and Palaeoenvironments (advance online publication)
DOI: 10.1007/s12549-011-0068-y
http://www.springerlink.com/content/311101262274k114/


More or less complete and articulated skeletons of fossil
air-breathing vertebrates with a long neck and tail often exhibit a
body posture in which the head and neck are recurved over the back of
the animal. Additionally, the tail is typically drawn over the body,
while the limbs have a rigid appearance. In palaeontological
literature, this “opisthotonic posture” of such fossils still requires
a causal interpretation in an etiological context. According to this
hypothesis, there is a presumption of a cerebral disorder generating
perimortem muscle spasms that are preserved by rapid burial or other
sequestration of a skeleton in the fossil record. We re-evaluate this
“opisthotonic posture hypothesis” by analysing the non-avian theropods
Compsognathus longipes and Juravenator starki from the famous South
Franconian plattenkalks of the Upper Jurassic Solnhofen Archipelago.
Decay experiments with the extant domestic fowl Gallus gallus L. and
analysis of the theropods’ constructional morphological constraints
reveal that the opisthotonic posture is not a peri- but a postmortem
phenomenon. By analysing the timeline of decomposition, it is possible
to recognise different stages of decay, depending on the varying decay
resistance of soft tissues. Adipocere formation must have blocked
further decay until embedding was completed by minimal sedimentation.
Analyses of the palaeoenvironment of the basins of the Solnhofen
Archipelago show that the conditions of deposition of individual
basins cannot be considered to be similar, even inside the same time
frame. Therefore, a generalised approach of looking at the
depositional setting must be excluded. Assumptions by Faux and Padian
(2007) that the accepted palaeoenvironmental reconstruction of the
Solnhofen Fossillagerstätte has to be questioned in the light of the
opisthotonic posture hypothesis enforce the need for a review of
palaeoecological factors of the Franconian Plattenkalks from a
taphonomic perspective.