The Mio-Pliocene is an important time-period in the evolution of our lineage. Biomolecular studies suggest that the last common ancestor of humans and chimpanzees (our closest living relatives) existed during this period. Mio-Pliocene hominid fossils are however extremely rare, with all known specimens hitherto having been found in East Africa. While the Langebaanweg deposits have thus far not produced any hominids and are generally poor in all types of primates, they remain an important source of information on the African Mio-Pliocene environment and fauna
Despite its importance, surprisingly little primary research has taken place at Langebaanweg. The majority of fossils retrieved from the site were done so under uncontrolled circumstances during mining operations. While those fossils that could be identified prior to their destruction were saved, many other important specimens were undoubtedly lost. We know very little about the depositional environment and taphonomic histories of the vast majority of the material in our collections. Not only fossil material had been lost due to the largely uncontrolled nature of previous excavations. Much needed environmental indicators such as pollen and phytoliths could not be collected in situ, while precise data on sediments and other geological aspects of the site are rare. There is thus clearly a dire need for more controlled excavations to take place at Langebaanweg.
Although the most recent excavations have been performed under controlled conditions (see Figure 1 below), they are limited in certain aspects. Firstly, a relatively small area has thus far been excavated. While these excavations do begin to shed light on the depositional environment and taphonomic history of the excavated area, the fossiliferous deposits are much more extensive.
The nature of deposits also varies significantly across the site. Additional excavations further away from previously excavated areas are required in order to build a more precise picture of depositional environment and taphonomic history.
Secondly, 3-dimensional data is not available for previous excavations as they have been performed without the aid of a total station. This type of data would help immensely with the reconstruction of site formation. Thirdly, excavations have not been performed with the aim of sampling for possible pollens and phytoliths. Precise data about the sedimentological context of soil samples are required to interpret these ecological indicators. In addition to addressing these three shortcomings in previous controlled excavations, new excavations would add valuable specimens to the existing excavated faunal sample. With controlled excavations, the chances of finding rare specimens such as the bear skull, Agriotherium africanum (Figure 2), in a greater state of completeness are greatly increased.
We plan to continue excavations at this site during the 2nd and 3rd excavation seasons. Depending on its richness and potential to achieve our research goals, we may elect to continue excavating only in this area, or to expand our excavations to other promising sites within the general vicinity.
As a priority for the first season of excavations, we cleaned up Brett Hendey’s last excavation (performed in 1976) and excavated certain witness sections left by him (image 3A). Today, this site is situated right next to the excavation currently open to the public (image 3B). Hendey excavated in meter squares, leaving witness sections (of 1 meter square) between excavated sections which we would like to target for excavation after the clean-up. As this was where Hendey found the near complete skeleton of the bear, Agriotherium africanum, it has the potential to yield more remains, particularly post-cranial remains, of this valuable specimen. Once the area has been opened, mapped and sediment samples taken, the fossils will be left in situ and the site will be incorporated into the public tour. Fossils will be removed from this excavation site if they are of important scientific value.
The first excavation season consisted of 2½ weeks in the field during June/July 2008. Three experienced excavators participated, namely Deano Stynder (Iziko SA Museum), Lloyd Rossouw (Bloemfontein National Museum), and Pippa Haarhoff (West Coast Fossil Park). We had three volunteers sorting material under the supervision of Albrecht Manegold (Forschung Institute, Germany).
Excavations focussed on an area in the LQSM sediments which lay between Hendeys MPPM witness sections, and an area of one-and-a-half square meters was excavated (The geology of Langebaanweg). Large bones and ungulate remains were rare, and most of the fossils recovered consisted of microfaunal remains (e.g. rodents, insectivores, reptiles).
Four bovid horn-cores were retrieved however. The few large bones that were found showed evidence of carnivore gnawing. The remains of hyena (?) coprolites were also found associated with the large bones. During the course of the excavation, Lloyd Rossouw took soil samples for phytolith analysis and this report has been published in the South African Journal of Science (2009, Volume 105). A field school, which will be held in conjunction with Arizona State University, USA, is planned for the 2010 field season.