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Sauropod fauna of Lower Cretaceous Kirkwood Formation of South Africa



Ben Creisler
bcreisler@gmail.com


A new paper:


Blair W. McPhee, Philip D. Mannion, William J. de Klerk & Jonah N.
Choiniere (2016)[2015]
High diversity in the sauropod dinosaur fauna of the Lower Cretaceous
Kirkwood Formation of South Africa: Implications for the
Jurassic–Cretaceous transition.
Cretaceous Research 59: 228–248
doi:10.1016/j.cretres.2015.11.006
http://www.sciencedirect.com/science/article/pii/S0195667115301142

The Kirkwood Formation of South Africa has long been recognized as
having the potential to fill an important gap in the Mesozoic
terrestrial fossil record. As one of the few fossil-bearing deposits
from the lowermost Cretaceous, the Kirkwood Formation provides
critical information on terrestrial ecosystems at the local,
subcontinental (southern Gondwana), and global scale during this
poorly sampled time interval. However, until recently, the dinosaurian
fauna of the Kirkwood Formation, especially that pertaining to
Sauropoda, has remained essentially unknown. Here we present
comprehensive descriptions of several relatively well-preserved
sauropod vertebrae collected from exposures throughout the formation.
We identify at least four taxonomically distinct groups of sauropod,
comprising representatives of Diplodocidae, Dicraeosauridae,
Brachiosauridae, and a eusauropod that belongs to neither
Diplodocoidea nor Titanosauriformes. This represents the first
unequivocal evidence of these groups having survived into the earliest
Cretaceous of Africa. The taxonomic composition of the Kirkwood
Formation shows strong similarities to Upper Jurassic deposits, and
raises questions regarding the taxonomic decline across the
Jurassic/Cretaceous boundary that has been previously inferred for
Sauropoda. Investigation of the sauropod fossil record of the first
three geological stages of the Cretaceous suggests that reconstruction
of sauropod macroevolutionary patterns is complicated by a combination
of sampling bias, an uneven and poorly dated rock record, and
spatiotemporal disparity in the global disappearance of certain
sauropod groups. Nonetheless, the close ecological relationship
consistently observed between Brachiosauridae and Diplodocidae, as
well as their approximately synchronous decline, suggests some
equivalence in response to the changing faunal dynamics of the Early
Cretaceous.