The South African Mesozoic: advances in our understanding of the evolution, palaeobiogeography, and palaeoecology of sauropodomorph dinosaurs
Date
2016
Authors
McPhee, Blair Wayne
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
The Palaeontological record of South Africa is remarkable in that it preserves the two major
temporal transitions of the Mesozoic: The Triassic–Jurassic boundary (the Elliot Formation) and
the earliest depositional stages of the Cretaceous (the Kirkwood Formation).
Work within the Elliot Formation has reiterated the importance of this horizon for our
understanding of the early evolution and subsequent radiation/diversification of basal
sauropodomorph dinosaurs. Moreover, inextricably contained within this radiation is the early
evolution of the columnar-limbed, long necked sauropods, the largest terrestrial animals to
have ever evolved. The Elliot Formation therefore imparts vital information on the genesis of
the group that would become the dominant dinosaurian herbivores throughout most of the
Mesozoic. However, several outstanding issues obscure a full understanding of this important
radiation. Of primary concern is the complicated taxonomy of the sauropodomorphs of the
Upper Triassic lower Elliot Formation and a lack of current consensus as to what precisely
constitutes a true sauropod. The latter issue is further complicated by a lack of well-preserved
sauropod material prior to the Toarcian. The discovery of new, associated material from both
the lower and upper Elliot Formation has direct relevance to both of these concerns.
Specifically, although the genus Eucnemesaurus is supported in the current analysis, the
bauplan diversity of lower Elliot Sauropodomorpha remains relatively conservative save for the
stocky pedal architecture of Blikanasaurus and the autapomorphically robust morphology of a
newly rediscovered ilium that is potentially referable to it. Within the upper Elliot Formation, a
recently discovered highly apomorphic bone-bed is diagnosed as a new species of sauropod
that, in addition to placing the earliest unequivocal sauropods within the basal rocks of the
Jurassic, suggests the underlying ecological factors driving the divergence of the derived
sauropodan bauplan.
In addition to new information provided by the Elliot Formation, two decades’ worth of
collecting from the Early Cretaceous Kirkwood Formation affords a long overdue insight into the
sauropod fauna occupying southern Gondwana at the outset of the Cretaceous. The surprising
diversity of forms recognized from the Kirkwood suggests that the taxonomic decline of
Sauropoda previously inferred for the earliest Cretaceous is a product of sampling bias
compounded by a generally poor fossil record. However, a lack of absolute dates for the
Kirkwood Formation means that the plethora of “Jurassic-type” specimens is potentially
explicable via their being contemporaneous with similar Late Jurassic faunas of eastern Africa
and North America.
Description
A dissertation submitted to the Faculty of Science, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Doctor of Philosophy.
Johannesburg, 2016.
Keywords
Citation
McPhee, Blair Wayne (2016) The South African Mesozoic: advances in our understanding of the evolution, palaeobiogeography, and palaeoecology of sauropodomorph dinosaurs, University of Witwatersrand, Johannesburg, <http://wiredspace.wits.ac.za/handle/10539/21644>