Catherine Sasman
14 November 2008
analysis
Windhoek — Namibia did have dinosaurs, and the last remaining testimony thereof, the footprints on Farm Otjihaenamaparero, are protected by law.
Secondary roads D2404 and D2414 off the Okahandja-Otjiwarongo main road lead to the signpost of farm Otjihaenamaparero.
This farm is world famous for the dinosaur footprints that occur in sandstones of more than 200 million year old Etjo Formations that accumulated under even drier conditions than is now experienced with winds blowing in from the Namib Desert.
The footprints - with a distance of about 75 to 85 centimeters apart - indicate that the animal that left it had hind legs of about one meter long.
These footprints believed to be 219 million years old are those of a dinosaur. It has three quite sharp toes at the end, and the whole print is about the same length as that of a human foot.
The area was declared a national monument, and has two crossing track-ways with more than 30 imprints with sizes of about 45 by 35 centimeters. The longer track-way can be followed for about 28 meters. There are also smaller, individual imprints.
From these, it is deduced that these are the hind feet of a bipedal animal. But no body fossils were found.
Footprints at the upper most strata at Etjo Mountain consist of sandstones that accumulated in a fairly arid environment.
But, said Helke Mocke, geologist with the Ministry of Mines and Energy, arguments from dinosaur experts are that these cannot be the footprints of 'real' or 'well known' dinosaurs.
The argument of these experts, she said, is that Namibia does not have the well-preserved Jurassic rock the remains of dinosaurs were found in.
These experts argued that environmental conditions in Southern Africa during the Jurassic and Cretaceous times were very hostile, with arid conditions prevailing and widespread volcanic eruptions.
This is nonsense, said Dr Gabi Schneider, a geologist and head of the Geological Survey Directorate at the ministry.
"Some of the remains at Waterberg were found in rock formations found in the main southern African Karoo that has one of the richest deposits of dinosaurs in the world," Schneider said.
Schneider has written the book, Passage through time - fossils in Namibia, published in 2004, with a chapter dealing exclusively with the dinosaurs found in Namibia.
The National Earth Science Museum at the ministry's head office in Windhoek is home to an impression of a dinosaur belonging to the Massospondylus species that lived about 200 million years old.
Mossospondylus means 'massive vertebra', and this animal is estimated to have been about three to five meters in length, and one meter tall.
It is also one of the most popular attractions to the museum.
The remains of dinosaurs found in Namibia, said Mocke, were only bone impressions.
The Massospondylus was found near the Waterberg Mountain, and was widespread and found in other areas like South Africa, Botswana and Arizona in North America.
Other types of dinosaurs found at Waterberg were Quemetrisauropus and Prototrisauropus, all of these being herbivores.
The footprints at Farm Othihanamaperero belonged to the Sytarsus (or small carnivore) dinosaurs, and a large Ceratosaurian dinosaur.
The name dinosaur, said Mocke, means 'terrible lizard'.
"The word was first coined by English anatomist, Sir Richard Owen, in 1842 for bones he found and described as belonging to lizards. Today, there is still no consensus on whether dinosaurs are cold blooded like lizards, or warm blooded like mammals. Scientists have provided several lines of evidence for both scenarios," Mocke said.
The age of dinosaurs is considered to have been between the Triassic, Jurassic and Cretaceous times.
Dinosaurs, descendents of small, bipedal thecodonts, first appeared in the late Triassic period (about 230 million years ago), which was about the same time as the first mammals.
There are 900 different species of dinosaurs identified worldwide.
During the late Triassic and early Jurassic period (about 200 million years ago), dinosaurs developed into quite large and often bipedal animals, adapting to their changed environments.
The Cretaceous period followed the Jurassic age.
Also in the Jurassic period, wrote Schneider, dinosaurs became more common and diverse.
By the end of the Triassic period, all major dinosaur groups were well established.
These were naturally divided into two groups: the ornithischians, or bird-hipped herbivores, and saurischians (lizard-hipped).
Scheider said dinosaurs dominated land communities for the next 140 million years; only after the dinosaurs died out did mammals become dominant.
She said due to the continuous climatic conditions, it can be assumed that the dinosaurs became extinct not long after the footprints were left behind.
About 180 million years ago, volcanic eruptions and lava changed the southern African landscape, which brought in the end of Gondwanaland, and the break-up of the earth, the formation of the Atlantic Ocean that split Africa and South America.
This Jurassic volcanism, said Schneider, explains why the more common and well known dinosaurs like the Tyrannosaurus and the Triceratops, that roamed in the northern hemisphere during the Jurassic and Cretaceous times, can indeed not be found in southern Africa.
However, she argued, the limited sedimentary deposits representing this time in Namibia and the environment in which they were deposited, may not have been favourable for the preservation of fossils.
More research, she said, is needed that could possibly reveal more information and hopefully more deposits in the Etjo Formation.
There are still questions asked about how dinosaurs died out.
There are several schools of thought, said Mocke.
One theory is that the dramatic changes with the break-up of Gondwanaland, bringing about even more dramatic changes in the environment, and hence in the living conditions of the dinosaurs, resulted in their extinction.
The most recognised theory is the one that holds that an asteroid of about 10 to 15 kilometers in diameter hit the earth and events following this resulted in the mass extinction of the dinosaurs.
Some of these post-impacts, she said, included a blockage of sunlight for an estimated three months as a result of dusty material being blasted into the air.
A short-term global warming resulted in a 30 degree Celsius rise in temperature due to the release of tremendous amounts of energy released upon impact.
The impact, she said, caused global wildfires everywhere due to these high temperatures, and acid rain produced by the rapid heating of the atmosphere resulted in the formation of nitric acid.
This lead to long-term global cooling due to dust, soot and sulfate aerosols released by the asteroid impact, and finally long-term global warming due to the death of most biological life and the subsequent decrease in the uptake of organic carbon.
The most likely scenario, said Schneider, is a combination of both theories.
Due to the earth's break up, temperatures became colder and tropical forests on which dinosaurs fed were replaced by more temperate forests.
"It seems that the asteroid impact delivered the final blow to an already shaken community," Schneider writes.
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