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2023 FIELDWORK AT BOLT’S FARM CAVE SYSTEM

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2023 FIELDWORK AT BOLT’S FARM CAVE SYSTEM

By: Lazarus Kgasi, Junior Curator: DITSONG: National Museum of Natural History

 

The Bolt’s farm team, under the leadership of Dominique Gommery from, Centre National de Recherché Scientifique and Sorbonne University in France, has been meticulously excavating fossils from the Bolt’s Farm cave system in the Cradle of Humankind World Heritage site for the past few weeks.

The team of researchers from the University of Johannesburg’s Department of Zoology (UJ), Centre National de Recherché Scientifique /Sorbonne University and the DITSONG: National Museum of Natural History’s Palaeontology Section excavated fossils at Brad Pit fossil site, located in the Klinkert’s portion of the farm. Bolt’s Farm cave system is divided into three properties, namely Greensleeves, Klinkert’s and the Quarry portion. The excavation team holds two active permits issued by the South African Heritage Agency (SAHRA). The permits are for Greensleeves and Klinkert’s portions.

The focus of the April-June (2023) fieldwork was on the Brad Pit fossil site from the Klinkert’s portion. The team decided to continue the excavation where we left off in the October 2022 field season and we also wanted to continue mapping (photogrammetry) the site and continue to study the geology of the site as the site changes with every excavation or dig. The excavation was a success as many fossils were discovered during the dig and brought back to the Museum to be analysed and studied by the team. Conducting fieldwork is important as the Museum’s fossil collection expands and it also helps to understand the biodiversity as we know that the foundation of palaeontological collections is curation, ensuring the documentation, long-term preservation and accessibility for research.

A variety of other fossils as well as some of the most significant fossils in the world have been found in the Brad Pit fossil site. Non-hominid primates (Gommery et. al., 2023), birds (Pavia et. al., 2017), lizards (Vilakazi et. al., 2020), suids (Pickford et. al. 2019), rhinos, micro-mammals (Senut et. al., 2022), carnivores (in prep) and bovidae (in prep) have also been discovered at Brad Pit. Specimens excavated from decalcified breccia (soft sediment) are washed at the Museum, let to dry, and then analysed and catalogued. Those that are still embedded in breccia are taken to the chemical laboratory to be processed by an acetic acid formula (Kgasi et.al 2021).

 

The genus Geronticus belongs to the ibis subfamily. There are two different species, namely the southern bald ibis (Geronticus calvus) who is found in the southern parts of Africa and the waldrapp or northern bald ibis (Geronticus eremita) who is only found in the northern parts of the continent. Despite their geographical remoteness, both species have similarities. Both species have distinct breeding behaviours that are adapted to their specific habitats and build their nests on rock ledges. Due to their dry habitats, they both exhibit evolutionary adaptations in their foraging behaviours. It is thought that the split between these two species happened only recently between 335 000 and 1 million years ago.

The southern bald ibis belongs to the Threskiornithidae family of birds, which includes birds from warm temperate and tropical climates. The lack of feathers on their faces serves to distinguish the group. Ibises are classified taxonomically as members of the Threskiornithinae subfamily. Around 26 species of wading birds in this subfamily have long, thin, downward-curving beaks, and their sizes range from medium to large. Rarely do these species have a voice box, and when they do, the bird simply croaks or cackles angrily. Ibises are a very old group of animals. These birds first appear in fossil records during the Eocene period, 60 million years ago. This bird assists in painting a rough picture for us of how the Brad Pit site looked like millions of years ago.

Fossil birds are limited in the fossil collections, and this is due to many factors. One reason is that they have been rarely studied.

Dr N. Vilakazi and Ms Boitshepo Motsodisa sorting micro mammals during fieldwork at Brad Pit fossil site.

There are 350 species and 23 families of small lizards that are alive today, but very few fossil remains have been researched. This is likely a result of access issues with comparative osteological collections (anatomical analysis is nearly impossible because the comparative material is rarely fully processed) (per comm N. Vilakazi).

 

Dr Dominique Gommery wrapping a fragile newly excavated carnivore canine.

Brad Pit has also produced other fossils like Dinofelis and Megantereon sabre-tooth cats; the long-legged hyena, Chasmaporthetes; Parapapio, Papio and Cercopithecoides monkeys; a tiny, three-toed horse, Hipparion lybicum; a giant hyrax or ‘dassie’; and a huge chalicothere, a knuckle-walking animal related to a horse. In order to solve the puzzles, the team studies the bones for clues. To create sharp points out of bones, porcupines, for instance, leave distinctive chisel marks all around the edges. With reference to hyenas who crush bones so hard that they shatter through the middle, we as researchers seek for revealing evidence such as chips and flakes left behind by the impact of their teeth on a bone. Hyenas occasionally leave dental impressions on a bone. We do rely on these bones to inform us how they ended up in a cave, how they died, and in most cases, who killed who, as well as what kind of environment they were dining in as we rebuild the past through the eyes of the fossils.

 


Carnivore tooth Bovidae phange

The DITSONG: National Museum of Natural History’s Plio-Pleistocene Paleontology section also curates fossils from historical sites including Sterkfontein, Haasgat, Swartkrans, Ploverslake, Gondolin, and Kromdraai, to name a few, however, the Bolt’s Farm Collection is currently the only one that is growing in our section.

 

References
1. Austin, O; Singer, A; Zim, H (1961). Birds of the world: a survey of the twenty-seven orders and one hundred and fifty-five families. New York: Golden Press.

2. Siegfried (1971). “The status of the Bald Ibis of Southern Africa”. Biological Conservation. 3 (2): 88–91. doi:10.1016/0006-3207(71) 90004-8.
3. Pegoraro (2001). “Mitochondrial DNA sequence evidence for close relationship of Bald Ibis, Geronticus calvus, and Waldrapp Ibis, G. eremita”. Ostrich. 72 (3–4): 215–216. doi:10.2989/00306520109485324.
4. Mid-Pliocene bald ibis (Geronticus cf. calvus; Aves: Threskiornithidae) from the Cradle of Humankind, Gauteng, South Africa and its environmental and evolutionary implications
Marco Pavia, Gregory B. P. Davies, Dominique Gommery & Lazarus Kgasi, PalZ volume 91, pages 237–243 (2017).
5. Southern African Tetraconodontinae: Recent discoveries. M Pickford, D Gommery, L Kgasi, N Vilakazi, B Senut… – Communications of the geological Survey of Namibia, 2019.
6. Mylomygale (Macroscelidea, Macroscelididae) from the Pliocene of South Africa
B Senut, F Sénégas, D Gommery, N Vilakazi, L Kgasi… – Journal of African Earth Sciences, 2022.
7. First fossil Agama lizard discovered in the Cradle of Humankind (Bolt’s Farm Cave System, South Africa).
N Vilakazi, D Gommery, L Kgasi – Annals of the Ditsong National Museum of Natural History …, 2020.
8. First in situ middle Pliocene cercopithecoid fossils from the Palaeokarst System of Bolt’s Farm (South Africa)
D Gommery, L Kgasi, N Vilakazi, F Sénégas… – Geodiversitas, 2023.

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