Dinosaur tracks from Burro Canyon Formation, Utah + Late Triassic tetrapods from Poland + more

[Ben Creisler <bcreisler@gmail.com>]

Ben Creisler
bcreisler@gmail.com


A number of recent papers:

Open access:


Jesper Milàn, Luis M. Chiappe, David B. Loope, James I. Kirkland &
Martin G. Lockley (2015)
First report on dinosaur tracks from the Burro Canyon Formation, San
Juan County, Utah, USA – evidence of a diverse, hitherto unknown Lower
Cretaceous dinosaur fauna.
Annales Societatis Geologorum Poloniae 85: 515–525
doi: http://dx.doi.org/10.14241/asgp.2015.034
http://www.asgp.pl/85_3_515_525
http://www.asgp.pl/sites/default/files/volumes/85_3_515_525.pdf

The newly discovered White Mesa tracksite in the Burro Canyon
Formation represents a snapshot of a diverse, Lower Cretaceous
dinosaur fauna from south-eastern Utah. The tracks were found at a
construction site where the sandstone had been bulldozed and broken
up. All tracks were found as deep, well-preserved natural casts on the
underside of the sandstone slabs. Individual theropod tracks are 19–57
cm in length; one peculiar track shows evidence of a possible
pathological swelling in the middle of digit III and an apparently
didactyl track is tentatively assigned to a dromaeosaurid. Individual
sauropod tracks are found with pes lengths of 36–72 cm, and
interestingly, three distinct shapes of manus tracks, ranging from
wide banana shaped to rounded and hoof-like. Ornithopods are
represented with individual tracks 18–37 cm in length; a sin gle track
can possibly be attributed to the thyreophoran ichnogenus Deltapodus.
Zir con U-Pb dating places the track-bearing layer in the Barremian,
contemporary to the lower Yellow Cat Member of the Cedar Mountain
Formation, which has a similar faunal composition based on both tracks
and body fossils. This new track-fauna demonstrates the existence of a
diverse dinosaurian assemblage in the lower part of the Burro Canyon
Formation, which hitherto is not known to yield skeletalre mains.

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Open access:

Aase Roland Jacobsen, Henrik Lauridsen, Bente Fiirgaard, Lene Warner
Thorup Boel & Kasper Hansen (2015)
Healed or non-healed? Computed tomography (CT) visualisation of
morphology of bite trace ichnotaxa on a dinosaur bone.
Annales Societatis Geologorum Poloniae 85: 457–464
doi: http://dx.doi.org/10.14241/asgp.2015.022
http://www.asgp.pl/85_3_457_464
http://www.asgp.pl/sites/default/files/volumes/85_3_457_464.pdf


Bite traces on fossilised bones can provide important information on
predator-prey relations and interactions in ancient environments. In
2009, two new ichnotaxa, Linichnus serratus and Knethichnus
parallelum, were introduced to develop the application of bite traces
as an ichnological tool. Ichnotaxa defined by theropod bite traces can
provide useful information for understanding feeding behaviour.
However, objective interpretation of possible bite traces can be
difficult using traditional visual inspection. In this study, the bite
traces on a fossilised dinosaur bone were comprehensively examined by
correlating traditional naked-eye inspection with computed to mography
(CT) imaging, used to visualise the internal morphology of the bite
traces and in particular, to clarify the appearance of one possibly
healed bite trace. A forensic pathologist visually examined the bone
with the aid of stereomicroscopy and a radiologist analysed the CT
scans. Sixteen different scanner settings were used to optimise the CT
parameters and avoid signal at tenuation, in the form of hypointense
artefacts in the central trabeculated part of the bone fragment. The
use of CT scanning provided information on internal morphology from
the vicinity of the bite trace, including hyperdense zones, not
identified using visual inspection alone. By applying the extended CT
scale, the dense and radiopaque cortical bone layer could be clearly
identified and applied as a pathomorphological marker to correctly
distinguish non-healed from healed wounds. In conclusion, the authors
demonstrate that external visual examination of trace fossils by
ichnologists in combination with interior examination using CT imaging
can be applied to characterise ichnotaxa defined by bite traces and
potentially provide clues on ancient feeding behaviour.


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Open access

Spencer G. Lucas (2015)
Age and correlation of Late Triassic tetrapods from southern Poland.
Annales Societatis Geologorum Poloniae (advance online  publication)
doi: http://dx.doi.org/10.14241/asgp.2015.024
http://www.asgp.pl/sites/default/files/in_press_85_3_Lucas.pdf


Age assignments of Triassic tetrapod fossils can be achieved by direct
reference to a scheme of Triassic land-vertebrate faunachrons (LVFs)
that correlates Triassic tetrapod fossil assemblages to each other
based solely on the tetrapod fossils. Correlation of Triassic tetrapod
assemblages to the standard global chronostratigraphic scale (SGCS,
the “marine timescale”) is a separate cross correlation between the
vert brate biochronology and marine biochronology that usually relies
on other data (e.g., palynostratigraphy, magnetostratigraphy,
radioisotopic ages) to be completed. Late Triassic tetrapod fossils in
southern Poland are found at two stratigraphic positions, the
Krasiejów and Lisowice levels. The tetrapod assemblage of the
Krasiejów level is as signed to the early Adamanian LVF based
primarily on the stratigraphic overlap of the phytosaur Parasuchus
with the Adamanian index aetosaur Stagonolepis. The amphibians
Cyclotosaurus and Gerrothorax, a Proterochersis-like turtle and the
aetosaur Paratypothorax from the Lisowice level indicate it is as
signable to the Revueltian LVF. Cross correlations to the SGCS are
less definitive, but sug est that the Krasiejów level is late Carnian
and the Lisowice level is early/middle Norian. However, this
correlation of the Krasiejów level is confounded by dis agree ments
over correlation of the marine Carnian–Norian bound ary to nonmarine
strata .   In deed, the possibility that the Krasiejów tetrapods fill
a gap in the early Norian record of tetra pods merits consideration.
Such difficulties emphasize the value of correlating tetrapod
assemblages to each other using a land-vertebrate
biostratigraphy/biochronology, in tead of immedi tely attempting the
more problematic correlation to the SGCS .



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Ludwig Luthardt, Ronny Rößler & Joerg W. Schneider (2015)
Palaeoclimatic and site-specific conditions in the early Permian
fossil forest of Chemnitz – Sedimentological, geochemical and
palaeobotanical evidence.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
doi:10.1016/j.palaeo.2015.10.015
http://www.sciencedirect.com/science/article/pii/S0031018215005775

Highlights

Chemnitz fossil forest represents a wet spot in a semi-arid to
semi-humid climate
Different lines of evidence from the palaeosol indicate strong seasonality
Geochemical data provides MAP of 800-1,100 mm/a, but a low amount of weathering
Palaeosol witnessed different root adaptations of the hygrophilous
plant community
Multi-aged woody arboreal plants show different kinds of tree rings

Abstract

As significant indicators of deep-time palaeoclimate a number of new
palaeontological, pedological and geochemical characteristics are
provided for the Chemnitz Fossil Lagerstätte to depict more precisely
its environmental conditions. For the first time, several lines of
evidence indicate that this fossil forest, instantaneously preserved
by volcanic deposits, once received an annual precipitation of around
800–1,100 mm, but grew on a nearly unweathered palaeosol. Although the
composition of this rich and diverse T0 assemblage suggests a
hygrophilous, dense and multi-aged vegetation dominated by
conservative lineages, the habitat was affected by environmental
disturbances and pronounced seasonality. Repeated changes in local
moisture availability are suggested by geochemical proxies, the
co-occurrence to intergrowth of calcic and ferric glaebules in the
palaeosol and developmental traits of perennial vegetational elements.
Specific substrate adaptation is reflected by different root systems
and cyclic growth interruptions recorded in the stems, branches and
roots of long-lived woody plants. Many differentially adapted
terrestrial animals complete the more comprehensive reconstruction of
a late Sakmarian ecosystem and its climatic and preservational
controls. Albeit spatially confined, this diverse in-situ record may
contribute to understand wetland-dryland dynamics of sub-tropical
Northern Hemisphere Pangaea.