Caitlin E. Syme & Steven W. Salisbury (2018)
Taphonomy of Isisfordia duncani specimens from the Lower Cretaceous (upper Albian) portion of the Winton Formation, Isisford, central-west Queensland.
Royal Society Open Science 2018 5: 171651
DOI: 10.1098/rsos.171651.Â
Taphonomic analysis of fossil material can benefit from including the results of actualistic decay experiments. This is crucial in determining the autochthony or allochthony of fossils of juvenile and adult Isisfordia duncani, a basal eusuchian from the Lower Cretaceous (upper Albian) distal-fluvial-deltaic lower Winton Formation near Isisford. The taphonomic characteristics of the I. duncani fossils were documented using a combination of traditional taphonomic analysis alongside already published actualistic decay data from juvenile Crocodylus porosus carcasses. We found that the I. duncani holotype, paratypes and referred specimens show little signs of weathering and no signs of abrasion. Disarticulated skeletal elements are often found in close proximity to the rest of the otherwise articulated skeleton. The isolated and disarticulated skeletal elements identified, commonly cranial, maxillary and mandibular elements, are typical of lag deposits. The holotype QM F36211 and paratype QM F34642 were classified as autochthonous, and the remaining I. duncani paratypes and referred specimens are parautochthonous. We propose that I. duncani inhabited upper and lower delta plains near the Eromanga Sea in life. Their carcasses were buried in sediment-laden floodwaters in delta plain overbank and distributary channel deposits. Future studies should refer to I. duncani as a brackish water tolerant species.
News:
Cretaceous croc had steamy past
Isisfordia lived and died in brackish-water deltas.
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Gabriel S. Ferreira, Mario Bronzati, Max C. Langer & Juliana Sterli (2018)
Phylogeny, biogeography and diversification patterns of side-necked turtles (Testudines: Pleurodira).
Royal Society Open Science 2018 5: 171773Â
DOI: 10.1098/rsos.171773.Â
Pleurodires or side-necked turtles are today restricted to freshwater environments of South America, AfricaâMadagascar and Australia, but in the past they were distributed much more broadly, being found also on Eurasia, India and North America, and marine environments. Two hypotheses were proposed to explain this distribution; in the first, vicariance would have shaped the current geographical distribution and, in the second, extinctions constrained a previously widespread distribution. Here, we aim to reconstruct pleurodiran biogeographic history and diversification patterns based on a new phylogenetic hypothesis recovered from the analysis of the largest morphological dataset yet compiled for the lineage, testing which biogeographical process prevailed during its evolutionary history. The resulting topology generally agrees with previous hypotheses of the group and shows that most diversification shifts were related to the exploration of new niches, e.g. littoral or marine radiations. In addition, as other turtles, pleurodires do not seem to have been much affected by either the CretaceousâPalaeogene or the EoceneâOligocene mass extinctions. The biogeographic analyses highlight the predominance of both anagenetic and cladogenetic dispersal events and support the importance of transoceanic dispersals as a more common driver of area changes than previously thought, agreeing with previous studies with other non-turtle lineages.
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