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Aristonectine elasmosaurid from Angola + mosasaur paleotemperature environment + Uruguay archosauromorph



Ben Creisler
bcreisler@gmail.com


A number of recent papers:



R. Araújo, M.J. Polcyn, J. Lindgren, L.L. Jacobs, A.S. Schulp, O.
Mateus, A. Olímpio Gonçalves and M.-L. Morais (2015)
New aristonectine elasmosaurid plesiosaur specimens from the Early
Maastrichtian of Angola and comments on paedomorphism in plesiosaurs.
Netherlands Journal of Geosciences  (advance online publication)
DOI: http://dx.doi.org/10.1017/njg.2014.43
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9557869&fulltextType=RA&fileId=S0016774614000432


New elasmosaurid plesiosaur specimens are described from the Early
Maastrichtian of Angola. Phylogenetic analyses reconstruct the Angolan
taxon as an aristonectine elasmosaurid and the sister taxon of an
unnamed form of similar age from New Zealand. Comparisons also
indicate a close relationship with an unnamed form previously
described from Patagonia. All of these specimens exhibit an ostensibly
osteologically immature external morphology, but histological analysis
of the Angolan material suggests an adult with paedomorphic traits. By
extension, the similarity of the Angolan, New Zealand and Patagonian
material indicates that these specimens represent a widespread
paedomorphic yet unnamed taxon.


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C. Strganac, L.L. Jacobs, M.J. Polcyn, K.M. Ferguson, O. Mateus, A.
Olímpio Gonçalves, M.-L. Morais and T. da Silva Tavares (2015)
Stable oxygen isotope chemostratigraphy and paleotemperature regime of
mosasaurs at Bentiaba, Angola.
Netherlands Journal of Geosciences  (advance online publication)
DOI: http://dx.doi.org/10.1017/njg.2015.1
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9557532&fulltextType=RA&fileId=S0016774615000013


Stable oxygen isotope values of inoceramid marine bivalve shells
recovered from Bentiaba, Angola, are utilised as a proxy for
paleotemperatures during the Late Cretaceous development of the
African margin of the South Atlantic Ocean. The δ18O values derived
from inoceramids show a long-term increase from –3.2‰ in the Late
Turonian to values between –0.8 and –1.8‰ in the Late Campanian.
Assuming a constant oceanic δ18O value, an ∼2‰ increase may reflect
cooling of the shallow marine environment at Bentiaba by approximately
10°. Bentiaba values are offset by about +1‰ from published records
for bathyal Inoceramus at Walvis Ridge. This offset in δ18O values
suggests a temperature difference of ∼5° between coastal and deeper
water offshore Angola. Cooler temperatures implied by the δ18O curve
at Bentiaba coincide with the stratigraphic distribution of diverse
marine amniotes, including mosasaurs, at Bentiaba.


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Also, now officially published:


Martín D. Ezcurra, Pablo Velozo, Melitta Meneghel & Graciela Piñeiro (2015)
Early archosauromorph remains from the Permo-Triassic Buena Vista
Formation of north-eastern Uruguay.
PeerJ 3:e776
doi:http://dx.doi.org/10.7717/peerj.776
http://dx.doi.org/10.7717/peerj.776


The Permo-Triassic archosauromorph record is crucial to understand the
impact of the Permo-Triassic mass extinction on the early evolution of
the group and its subsequent dominance in Mesozoic terrestrial
ecosystems. However, the Permo-Triassic archosauromorph record is
still very poor in most continents and hampers the identification of
global macroevolutionary patterns. Here we describe cranial and
postcranial bones from the Permo-Triassic Buena Vista Formation of
northeastern Uruguay that contribute to increase the meagre early
archosauromorph record from South America. A basioccipital fused to
both partial exoccipitals and three cervical vertebrae are assigned to
Archosauromorpha based on apomorphies or a unique combination of
characters. The archosauromorph remains of the Buena Vista Formation
probably represent a multi-taxonomic assemblage composed of
non-archosauriform archosauromorphs and a 'proterosuchid-grade'
animal. This assemblage does not contribute in the discussion of a
Late Permian or Early Triassic age for the Buena Vista Formation, but
reinforces the broad palaeobiogeographic distribution of
'proterosuchid grade' diapsids in Permo-Triassic beds worldwide.