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Baby mosasauroid from Morocco + rare earth elements in Triassic marine reptile bones



From: Ben Creisler
bcreisler@gmail.com


A new paper:



Alexandra Houssaye & Nathalie Bardet (2013)
A baby mosasauroid (Reptilia, Squamata) from the Turonian of Morocco –
Tethysaurus ‘junior’ discovered?
Cretaceous Research 46:   208–215
doi: http://dx.doi.org/10.1016/j.cretres.2013.09.010
http://www.sciencedirect.com/science/article/pii/S0195667113001419


New Middle Turonian mosasauroid remains were discovered in the same
large-sized nodule that yielded a specimen referred to Tethysaurus
nopcsai Bardet et al., 2003, from the Goulmima region (southern
Morocco). They comprise isolated, fragmentary cranial elements (skull
and mandible) and some vertebrae. Their very small size suggests a
juvenile condition, an observation supported also by anatomical
(spongious nature of numerous bone parts), micro-anatomical (loose
inner spongiosa) and histological (numerous remains of calcified
cartilage deep into the centrum; radial vascular canals) data. These
bones belonged to a basal mosasauroid that cannot be distinguished
from Tethysaurus nopcsai to which taxon we tentatively assign the
material.



==

Another paper about marine reptiles that may be of interest:



Monika Kowal-Linka, Klaus Peter Jochum & Dawid Surmik (2013)
LA-ICP-MS analysis of rare earth elements in marine reptile bones from
the Middle Triassic bonebed (Upper Silesia, S Poland): Impact of
long-lasting diagenesis, and factors controlling the uptake.
Chemical Geology (advance online publication)
doi: http://dx.doi.org/10.1016/j.chemgeo.2013.10.038
http://www.sciencedirect.com/science/article/pii/S0009254113004944

The rare earth elements (REE) contained in fossil bones are widely
used for provenance and palaeoenvironmental studies. Earlier works
suggested that the REE uptake is limited to early diagenesis, but more
recent research provided evidence of long-term open-system diffusion
in fossil bones. We analysed thin-walled reptile bones, all collected
from the same Middle Triassic (~ 245 Ma) marine bonebed, comprising
vertebrate remains of likely different ages, to check the influence of
the long-term diagenesis on the concentrations of REE, in terms of
impact of pore water; the upper parts of the bones are contained in a
low-permeability crinoidal limestone, whereas their lower parts have
been affected by diagenetic fluids for a long time. We measured REE
and other trace element contents in 29 bones using LA-ICP-MS (totally
660 spots in 45 depth profiles). Neither the absolute concentrations
of the REE and the REE intra-bone PAAS-normalized patterns, nor the
inter-element ratios and the La, Ce and Eu anomalies appear useful to
distinguish between the likely older and younger bones in the bonebed.
The MREEN enrichment combined with the flat intra-bone distributions
of the REE lead to conclusion that REE fractionation and substitution
for Ca were the most important processes responsible for the selective
uptake. The low-permeability host rock and diagenetic fluids had a
significant impact on the trace element uptake and their intra-bone
distribution patterns. The lower parts of the bones that likely had a
long-lasting contact with the diagenetic fluids reveal a relative
enrichment in the REE and their easier diffusion into the bone
centres. The ability of fossil bones to incorporate trace elements
over a long time-span strongly limits the usage of particularly the
older samples for provenance and palaeoenvironmental reconstructions.
Additionally, the presented new analyses fill the gap between the
available databases of trace element concentrations in fossil bones
with regard to Middle Triassic samples.