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[dinosaur] Orthosuchus (crocodylomorph) from Lower Jurassic of Southern Africa + fossil-bearing localities in Elliot Formation




Ben Creisler
bcreisler@gmail.com


New papers:

K. N. Dollman, P. A. Viglietti & J. N. Choiniere (2017)
A new specimen of Orthosuchus stormbergi (Nash 1968) and a review of the distribution of Southern African Lower Jurassic crocodylomorphs.
Historical Biology (advance online publication)
doi: http://dx.doi.org/10.1080/08912963.2017.1387110
http://www.tandfonline.com/doi/full/10.1080/08912963.2017.1387110


Orthosuchus stormbergi (Nash 1968) is a rare member of the Lower Jurassic crocodylomorph fauna of Southern Africa. Here we report on a new specimen, consisting of a nearly complete dentary bone, and a previously collected specimen that can confidently be referred to this taxon. The dentary presents several features of utility for generic-level identification of Southern African crocodylomorphs, and furthermore the anatomy of this specimen allows for a modest revision of the generic diagnosis. Furthermore, it provides an opportunity to reassess differences in dentary morphology between basal South African crocodylomorphs with the intention of refining taxonomic identification. Finally, we review the stratigraphic provenance of all of Southern Africa’s known crocodylomorph taxa, and show that most are confined to the uppermost Elliot Formation. Protosuchus, Litargosuchus, Notochampsa, and Orthosuchus have first appearance data in uppermost Elliot Formation. Only Notochampsa has a confirmed last appearance datum in the Lower Clarens Formation. These findings have implications with regards to the true position of the Triassic-Jurassic Boundary, and paleoenvironmental pressures acting on the Crocodylomorpha over the boundary of the Upper Elliot and Lower Clarens Formations.

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Simon Wills, Jonah N. Choiniere & Paul M. Barrett (2017)
Predictive modelling of fossil-bearing locality distributions in the Elliot Formation (Upper Triassic–Lower Jurassic), South Africa, using a combined multivariate and spatial statistical analyses of present-day environmental data.
Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication)
doi: https://doi.org/10.1016/j.palaeo.2017.10.009
http://www.sciencedirect.com/science/article/pii/S0031018217307216

Highlights

Predictive model for fossil bearing localities is established.
Model significantly reduces the potential prospecting area.
Can be deployed at any scale
Sensitive to spatial data resolution and absence data

Abstract

Traditional methods of palaeontogical fieldwork often involve costly and inefficient searching for suitable fossil-bearing sites. The advent of digital spatial data offers an opportunity to improve fieldwork search efficiency. In this paper, we develop a model that identifies potential fossil localities at the reconnaissance stage of prospecting using a criterion of present-day environmental suitability for fossil discovery. This model employs techniques from analytical biology, Geographical Information Systems (GIS), and remote sensing. The model is designed to be flexible with no limit on the number of variables and can use a variety of data types (both continuous and categorical) by means of a principle coordinate analysis (PCO). We tested the model on outcrops of the Elliot Formation (Upper Triassic–Lower Jurassic) in the Free State, South Africa. Our model correctly predicted 95% of the known occurrences and reduced the potential prospective area from approximately 2300 km2 of mapped total outcrop to 597 km2 of prospectable outcrop. Initial field testing in 2015 identified two new sites based on model output.


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