The fossils of Graaff-Reinet

GRAAFF-REINET NEWS - About 250 million years ago, the tip of the African continent was on the South Pole. This resulted in an ice age.

Since continents are continuously but slowly on the move because of volcanic activity deep down at the bottom of the ocean, the African continent started moving away from the South Pole and so the ice age retreated.

High up in the mountains, where Cape Town is today, snow and ice started to melt and the melted ice and snow became fast-flowing rivers that mouthed out into a huge basin where Graaff-Reinet is today.

• There were huge forests with many trees during that period and that is why it is known as the Carboniferous or the period of trees. These trees produced a huge amount of oxygen which made the earth viable to sustain huge animal life like mammal-like reptiles.

Mammal-like reptiles

• The fossils date back to 230 million years and are known as mammal-like reptiles or Therapsids. They lived during the Permian period. They are not dinosaurs since dinosaurs lived roundabout 160 million years ago during the Jurassic Period. Mammal-like reptiles can be divided into carnivores (meat-eaters) and herbivores (plant-eaters.

Carnivores

• The gorgonopsian had very sharp incisors and large canines and were at their largest almost the size of horses. These animals ripped their prey into pieces which were then gulped down. Researchers believe that gorgonopsian had a gland situated in the centre of the brain which is also known as the third eye. Gorgonopsians usually hunted smaller Dicynodont (plant eaters).

Herbivores

• The most common herbivorous mammal-like reptile is Dicynodont which means two dog teeth. Some Dicynodonts were as large as hippos and others as small as dogs. Dicynodont fossil skulls are easily recognizable because of their hard tortoise-like beaks and tusks like those of an elephant. Apparently, only the males of the species had the tusks and it was used to fight for male domination in the herd or as part of a mating ritual.

They also had two openings in the skull which might be confused with eye sockets. The openings contained the bundles of muscle and ligaments used to make the jaw move up and down.

Some fossilized tracks of the Dicynodont family e.g. lystrosaurus, Aulacephalodon, Diictodon and small dicynodont can be found close to Graaff-Reinet at the Santa Sana game reserve.

Fish fossils

• Fish fossils are also present in the Beaufort Rock formation. Of course, they are not mammal-like reptiles but belong to the family Pisces. Atherstonia Scutata is commonly present in rocks of the Beaufort group. It is a freshwater fish and lived in the large inland lake which was here during prehistoric times.