Wrinkle Face

Scientists have found new evidence to help piece together the history of plate tectonics. A dinosaur called “First Wrinkle Face” has been found in Africa. Previously, remains were only known in South America and India.

This newly-discovered First Wrinkle Face (the translation of its Latin name Rugops Primus) is about 95 million years old. According to the theory of plate tectonics, this means that the continents of Africa and South America must have joined together until around then. Previously, scientists thought that separation had begun at an earlier date, based upon existing fossil remains for species such as Mesosaurus and Lystrosaurus.

The theory of plate tectonics only gained widespread acceptance after the 1960s, when the weight of evidence used to support it started to become very substantial. The work of palaeontologists – scientists who study dinosaur fossil remains – is a cornerstone of this body of work. However, plate tectonics is an imperfect science that is continually being refined. This latest discovery does not fit with the previous paradigm, and appears to require that changes be made to previously accepted dates for the breaking apart of Africa and South America.

This important new discovery of First Wrinkle Face was found in the Sahara desert by Paul Sereno from Chicago University and his report is included in the latest copy of the journal Proceedings of the Royal Society of London, Biological Sciences. Mr Sereno is an accomplished dinosaur hunter who also recently discovered an eight-tonne, 12-metre long “supercroc” (The Guardian, 02 June 2004).

When did South American and Africa really split apart?

Originally, all of the earth’s land masses are thought to have been joined together in a single supercontinent named Pangaea. This later split into Gondwana (southern continents) and Laurasia (northern continents), anywhere between 200 and 135 million years ago. The date of the subsequent division of Africa and South America occurred some time later, but the exact date has remained a subject of much debate. Before this discovery, Wrinkle Face and other similar dinosaurs known as abelisaurids had been found only in South America and India. This led some experts to suggest that Africa had fully split from the rest of Gondwana by as early as 120 million years ago.

However, this latest Wrinkle Face from Africa is only 95 million years old. We can therefore deduce that separation may actually have occurred much later than previously thought, probably no later than 100 million years ago. The situation is quite complicated, though. Land bridges could have persisted long after the main bodies of the continents diverged. For this reason, debate is likely to continue about the exact date of separation for a little while longer!

How does plate tectonic theory work?

Plate tectonics is a scientific concept de­veloped in the 1960s to explain the pattern of the Earth's land masses and the mechanisms by which they have changed position over time (its origins lie with Wegener’s theory of Continental Drift from 1912). Seven major crustal plates and twelve smaller plates have been recognised, each of which extends down into the earth’s upper mantle. These plates are thought to be moved by large scale thermal convection currents in the asthenosphere, generated by residual primary heat and radioactive decay in the earth’s core. Plates are composed of continental or oceanic crust or a combination of both (sial and sima, respectively). They are bounded by plate margins, which may be subdivided into three types:

1. constructive, where new ocean floor is accumulated on either side of a mid-oceanic ridge
2. destructive, where ocean floor is lost by engulfment along a subduction zone
3. conservative margin, where plates move past each other laterally without adding or destroying ocean floor. Such margins are marked by transform or trans­current faults.

It has been claimed that many of the Earth's major landforms can be explained by plate tectonics, especially mobile belts, island arcs and ocean trenches. Global patterns of earthquakes and volcanoes can also be explained through the hypo­thesis of sea-floor spreading, in which magma rises at the mid-oceanic ridges to form new crust which is moved laterally towards the plate margin, as if on a con­veyor belt, where it is destroyed by sub­duction, or causes the ocean to increase in width (e.g. the Atlantic or the Red Sea). When the plate movements lead to the rate of construction being exceeded by that of destruction the ocean will begin to close (e.g. the Mediterranean).

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