Karoo Palaeontology

Introduction

The Karoo rock outcrops have long been regarded as the largest and richest collecting grounds for fossils of a long extinct group of vertebrates known as therapsids or “mammal-like reptiles”. As the name suggests, members of the therapsid group show the step by-step evolutionary transition from reptiles into mammals. The layer upon layer of sedimentary rocks that make up the Karoo Supergroup are an almost continuous 120 million year-long record of climate change in western Gondwana from 300 to 180 million years ago. The rocks and fossils of the Karoo thus offer a unique opportunity to researchers, to find out how terrestrial ecosystems respond to climate changes over time scales measured in millions of years. Fossils of the Karoo Supergroup include plants (both macrofossils and pollen and spores), rare insects and fish, common and diverse tetrapods (mostly therapsids, temnospondyl amphibians, parareptiles, archosauromorphs and dinosaurs), and many types of trace fossils such as coprolites, burrows and trackways. Many of these specimens are held in the Karoo Palaeontology Collections at the Iziko South African Museum.

The Karoo is a vast semi-desert region that covers much of inland South Africa, and is considered a national treasure for its abundance of desert-adapted plant and animal life, as well as its world famous fossils. The Karoo rock outcrops have long been regarded as the largest and richest collecting grounds for fossils of a long extinct group of vertebrates known as therapsids or “mammal-like reptiles”. As the name suggests, members of the therapsid group show the step by-step evolutionary transition from reptiles into mammals. The layer upon layer of sedimentary rocks that make up the Karoo Supergroup are an almost continuous 120 million year-long record of climate change in western Gondwana from 300 to 180 million years ago. The rocks and fossils of the Karoo thus offer a unique opportunity to researchers, to find out how terrestrial ecosystems respond to climate changes over time scales measured in millions of years. Fossils of the Karoo Supergroup include plants (both macrofossils and pollen and spores), rare insects and fish, common and diverse tetrapods (mostly therapsids, temnospondyl amphibians, parareptiles, archosauromorphs and dinosaurs), and many types of trace fossils such as coprolites, burrows and trackways. Many of these specimens are held in the Karoo Palaeontology Collections at the Iziko South African Museum.

Late Devonian and Permo-Carbonifereous Fossil Collection

This collection covers the geologic period from around 380 to 300million years ago from Mid-Late Devonian to the end of the Carboniferous and includes leaves and stems of primitive lycopods and numerous specimens of palaeoniscid and acanthodian fishes as well as a rare shark from the rock strata (layers) known as the Bokkeveld and Witteberg Groups.

Permian to early Jurassic Fossil Collection

The Early-Permian to Early Jurassic time interval is considered the most important in tetrapod evolution as it was a time period when life on land was able to radiate throughout the supercontinent of Pangaea . During this interval, three mass extinctions severely affected the animals and plants living in western Gondwana. Karoo rocks and fossils provide researchers with vital clues as to what caused these catastrophic events This Iziko collection includes about 10 000 vertebrates – mainly synapsid reptiles – from this period, collected from the main Karoo Basin over the past 150 years.

The Karoo Palaeontology collection houses over 400 type specimens which are the first specimens of a particular species to have been described by scientists. Some of the more spectacular specimens include complete skeletons of large herbivorous tetrapods such as Paraeiasaurus, Rhachiocephalus, Endothiodon, Lystrosaurus, Odontocyclops, large carnivores such as Gorgonops and Pristerognathus and some exquisite multiple skeletons of the smaller herbivorous Diictodon and insectivorous Thrinaxodon, Youngina, Prolacerta and Euparkeria some of which were preserved in underground burrows. The collection also contains most complete skeletons yet found of Endothiodon bathystoma and Galesaurus planiceps and numerous Karoo-aged temnospondyl amphibian skeletons including several type specimens.

Cretaceous Crater Lake Fossils

Karoo Palaeontology houses an important collection of vertebrate fossils of Late Cretaceous (70 Mya) and Early Eocene (55Mya) ages that were discovered by diamond prospectors in the Bushmanland area of the Northern Cape. The collection contains over 250 complete skeletons of an extinct type of aquatic frog named Vulcanobatrachus mandelai , an extinct type of gar-fish known as Stompooria rogersmithi , and many small pond-living invertebrates such as ostracods, bivalves (mussels), and gastropods (water snails). Also included in this collection are the fragmentary remains of a large ornithopod dinosaur.

Trace Fossil Collection

Trace fossils provide indirect evidence of past life, and are important when used along with the body fossils, or when the body fossils aren’t preserved. The traces are preserved in rock and include footprint impressions, resting traces, burrow casts, coprolites (fossilized faeces) eggs, nests, root moulds and worm trails. The Karoo collection holds some 300 slabs displaying arthropod trackways from the Lower Ecca varved shales (Early Permian). There are also actual specimens and large fibreglass casts of several therapsid and amphibian trackways from the Beaufort (Mid-Permian to Mid Triassic) and dinosaur and amphibian trackways from the Stormberg Group (Late Triassic-Early Jurassic) strata.

The Baxter-Brown Fossil Plant Collection

This collection of over 1,300 plant fossils is made up of Mid Triassic material from the Molteno Formation of rocks in the Karoo Basin. It includes several type specimens. The collection is named after an amateur palaeontologist, Mr Alfred Brown, who was the postmaster of Aliwal North in the early 19th century and spent many hours collecting fossils from the surrounding koppies.

Research

Dr Roger Smith holds an A-rating from the National Research Foundation – awarded in 2014 – marking him as a world leader in his discipline. His work is largely field-based, and has taken him to Eritrea, Niger, Lesotho, Namibia, Madagascar, Antarctica, Zambia and Tanzania, expeditions mostly funded by the American National Science Foundation and the National Geographical Society. These projects allowed him to extend the research he’s conducted in the Karoo to the Rift Valley system, the 6,000km trench that runs from northern Jordan Rift Valley in Asia to Mozambique. He also works on numerous projects in the South African Karoo under the general title of ‘Palaeoecology of Gondwana’, where he uses the rocks and fossils to reconstruct the ancient landscapes at different time slices through the Permian and Triassic, and has made a detailed study of the changes that took place in the Karoo Basin before, during, and immediately after the End-Permian mass extinction. He also attempts to explain the recovery of the terrestrial ecosystem from the few survivors and the effect this had on the evolution of mammals. The results of this project, which is still ongoing, will probably be regarded as his main research contribution. Perhaps a more lasting legacy may be the more than 5000 Karoo vertebrate fossils that he has found logged, excavated and accessioned into South African national collections (Council for Geosciences in Pretoria and Iziko South African Museum in Cape Town). Among these are several new therapsid taxa (eg Progalesaurus lootsbergensis, Paraburnetia sneeubergensis, Lophorhinus willodenensis) and many complete skeletons of taxa previously known only from skulls (such as Galesaurus, Odontocyclops, Lystrosaurus curvatus, Lystrosaurus mccaigi, Endothiodon bathystoma, Eunotosaurus and Youngina) that have provided students with projects and are currently on display in museums throughout the country.

Other projects led by Dr Smith include the study of therapsid coprolites, looking at the hair-like structures and fragmentation patterns of bones in these ancient faeces. Dr Smith has accumulated a large study collection of Karoo-aged tetrapod coprolites from many parts of Gondwana. Currently he is studying some unique skeletal aggregations that he has recovered from the Fraserburg area which show evidence for shelter-sharing as well as evidence of preserved skin.

Keywords

Acanthodian: A small spiny-finned, jawed fossil fish.
Arthropod: An invertebrate animal with an exoskeleton (external skeleton), a segmented body, and jointed appendages (limbs), which makes up over 80% of described living animal species. It includes scorpions and spiders.
Burnetiid: or Burnetiidae, a family of therapsids that lived in Pangaea during the Permian Period fossils of which have been found in East Africa, South Africa and Russia.
Coprolites: A piece of fossilised dung.
Cynodont: A carnivorous, mammal-like fossil reptile with well-developed, specialised teeth.
Ichnofossils: Or trace fossils, the evidence of animals’ activities preserved in rock.
Early Jurassic: A geologic period of around 199 to 175 million years ago.
Early Triassic: The first of three epochs of the Triassic Period, and dates from 252-247 million years ago.
Ecca: A group of rock formations, of Early Permian age, in the Karoo Supergroup, consisting mainly of shales and sandstones.
Macrofossils: Fossils large enough to be visible to the naked eye.
Mass Extinction Event: The extinction of a large number of species,both on land and in the oceans, within a relatively short period of geological time; caused by a catastrophic global event or widespread environmental change.
Palaeoecology: the ecology – the relations of organisms to one another and their physical environment – of fossil plans and animals.
Palaeoniscidae: A group of fish who possessed a bony skeleton and operculum (gill cover).
Permian: A geologic period from around 298 to 252 million years ago.
Supercontinent: Large land masses that broke up to form today’s continents.
Synapsid: A fossil reptile that shows increasing mammalian characteristics and includes the ancestors of mammals.
Temnospondyl: A group of small to giant tetrapods – four-limbed vertebrates – that evolved over some 210 million years.
Terrestrial: Terrestrial, ie relating to the Earth, and in this case refers animals who live primarily or mostly on land.
Tetrapods: The first four-limbed vertebrates and their descendants, including the extinct and living amphibians, reptiles, birds, and mammals.
Therapsids, members of the r Therapsida, a group of animals that includes mammals and their ancestors; many of the characters associated exclusively with today’s mammals originated within early therapsids.
Thrinaxodon: A mammalian-like reptile of the cynodont group from which mammals eventually evolved. It has been proposed that it survived the post extinction dry climate burrowing underground. .
Trackways: A series of fossil footprints.
Varved shales: Thin layers of shale (a type of fine-grained rock) deposited from melted ice in a lake.
Western Gondwana: The part of the supercontinent today represented by Africa, Arabia, South America and West Antarctica.