Waterloo Farm: a three part reconstruction of the fauna and flora from three different sub-environments with in a Late Devonian estuary, painted by Maggie Newman
Overview
Waterloo Farm is an important fossil site having preserved remains of a diverse Late Devonian estuarine ecosystem (1). Part of the uniqueness of this locality lies in its geographic position at approximately 70° south, placing it likely within the Antarctic Circle. That diverse coastal fauna and flora thrived this far south was unknown before the discovery of Waterloo Farm, and indicates mild and cool coastal temperatures during the Famennian. Amongst the unexpected fauna were early tetrapods, previously believed to have been exclusively tropical at this time (2). Research and excavation at this locality is ongoing, and fossil finds are continually emerging.
History
The site is located to the south of Makhanda (formerly Grahamstown) in the Eastern Cape of South Africa. It was discovered in 1985 when a new highway bypass was cut through the quartzitic hills to the south of the town, as part of the government’s response to civil rights protests against Apartheid. In the mid 1980’s, angry protesters could block the national highway running through the town, where it went through the black township. As a result the government decided then to divert the road around the town, which resulted in the serendipitous exposure of the fossil-bearing black shales.
Early research led by Norton Hiller gave a Late Devonian age to the fossils, and proposed a brackish water lagoonal environment for the fossil shales (3). Rob Gess was hired to excavate at the site. Soon Hiller and Gess published reports on charophytes (nonmarine algae); seaweeds and progymnosperm trees (in collaboration with Dr Heidi Anderson), as well as a shark and placoderm fishes (in collaboration with Drs John Long and Eric Anderson). After Norton Hiller left Rhodes University (in 1994) funding for the project dried up and Gess and Hiller published a preliminary catalogue of what had been found.
Due to instability of the Waterloo Farm road-cutting, caused by the geological dip of the rocks, the bypass was cut back and stabilized twice. Both in 1999 and in 2008, with the assistance of the South African National Roads Agency (SANRAL), Rob Gess and a team of workers were on site to save fossiliferous shale from demolition, by hand-mining it in blocks. 80 tonnes of black shale are now preserved in sheds in his garden, where he continues to excavate the deposit.
Fossil Preservation
Most of the fossils at Waterloo Farm are preserved in black shale. The rock is well laminated and oily to the touch, having originated as sticky, anoxic black mud under periodically stagnant estuarine bottom waters. The fossils are preserved as mineralized compressions sandwiched on bedding planes of shale. Preserved in white mineral against the dark shale background, the fossils resemble photographic negatives. It is a rare phenomenon in the geological record that soft tissues are preserved, but fossils from Waterloo Farm often preserve soft body parts.
Biota
The Waterloo Farm fauna includes an array of extinct fossil fishes (including lampreys, placoderms, acanthodians, sharks, ray-finned fish and lobe-finned fish), all belonging to species not known elsewhere (1). Eurypterid arthropods and molluscs are common invertebrates preserved on the muddy bottom. The flora was dominated by zosterophylls, primitive 'ferns' (Flabelliopteris), seed plants, herbaceous lycopods (eg. Colpodexylon), tree lycopods (Leptophloeum and Kowieria) and Progymnosperm Archaeopteris forests. These, together with a number of other species comprise a remarkably diverse Late Devonian flora.
Some fish appear to have inhabited the estuary throughout their lives, as we can infer from fossils preserving a range of life sizes from juveniles to adults. These were mostly placoderms (‘platy-skins’), such as the bottom dwelling Bothriolepis africana, and Africanaspis doryssa, which had a large spike on its back. The placoderm Groenlandaspis riniensis was the most commonly preserved fish inhabiting the estuary. As in modern estuaries, some marine fish entered the river mouth to spawn, or gave birth to live young within the estuary. Juvenile coelacanths (Serenichthus kowiensis) lived (and sometimes died) within the estuary, but the adults would have returned to the ocean. Sharks also entered the estuary periodically to bear young and to hunt, and left evidence of their spines, teeth, skin and cartilage. Many-toed tetrapods (Umzantsia and Tutusius) would have made use of muscled forelegs to manoeuver about the shallows (where baby fishes would have hidden in the charophyte meadows) and may have been able to make brief excursions onto land. The top predator was Hyneria, a more than 3 metre long lobe-finned fish. Whereas, a 1.5 m long eurypterid (Cyrtoctenus wittebergensis) was a bottom dwelling, mudraking arthropod.
Climate
During the Famennian, the warm Devonian climate was changing with the eventual onset of glaciation at the poles. This was synchronous with a significant drop in atmospheric CO2, which may have been indirectly caused by novel Devonian forests (2). Tree fossils at Waterloo Farm, (eg. Archaeopteris and Leptophloeum) are consistent with a greenhouse climate in which Late Devonian forest ecosystems extended closer to the poles than today.
Waterloo Farm is an important fossil site having preserved remains of a diverse Late Devonian estuarine ecosystem (1). Part of the uniqueness of this locality lies in its geographic position at approximately 70° south, placing it likely within the Antarctic Circle. That diverse coastal fauna and flora thrived this far south was unknown before the discovery of Waterloo Farm, and indicates mild and cool coastal temperatures during the Famennian. Amongst the unexpected fauna were early tetrapods, previously believed to have been exclusively tropical at this time (2). Research and excavation at this locality is ongoing, and fossil finds are continually emerging.
History
The site is located to the south of Makhanda (formerly Grahamstown) in the Eastern Cape of South Africa. It was discovered in 1985 when a new highway bypass was cut through the quartzitic hills to the south of the town, as part of the government’s response to civil rights protests against Apartheid. In the mid 1980’s, angry protesters could block the national highway running through the town, where it went through the black township. As a result the government decided then to divert the road around the town, which resulted in the serendipitous exposure of the fossil-bearing black shales.
Early research led by Norton Hiller gave a Late Devonian age to the fossils, and proposed a brackish water lagoonal environment for the fossil shales (3). Rob Gess was hired to excavate at the site. Soon Hiller and Gess published reports on charophytes (nonmarine algae); seaweeds and progymnosperm trees (in collaboration with Dr Heidi Anderson), as well as a shark and placoderm fishes (in collaboration with Drs John Long and Eric Anderson). After Norton Hiller left Rhodes University (in 1994) funding for the project dried up and Gess and Hiller published a preliminary catalogue of what had been found.
Due to instability of the Waterloo Farm road-cutting, caused by the geological dip of the rocks, the bypass was cut back and stabilized twice. Both in 1999 and in 2008, with the assistance of the South African National Roads Agency (SANRAL), Rob Gess and a team of workers were on site to save fossiliferous shale from demolition, by hand-mining it in blocks. 80 tonnes of black shale are now preserved in sheds in his garden, where he continues to excavate the deposit.
Fossil Preservation
Most of the fossils at Waterloo Farm are preserved in black shale. The rock is well laminated and oily to the touch, having originated as sticky, anoxic black mud under periodically stagnant estuarine bottom waters. The fossils are preserved as mineralized compressions sandwiched on bedding planes of shale. Preserved in white mineral against the dark shale background, the fossils resemble photographic negatives. It is a rare phenomenon in the geological record that soft tissues are preserved, but fossils from Waterloo Farm often preserve soft body parts.
Biota
The Waterloo Farm fauna includes an array of extinct fossil fishes (including lampreys, placoderms, acanthodians, sharks, ray-finned fish and lobe-finned fish), all belonging to species not known elsewhere (1). Eurypterid arthropods and molluscs are common invertebrates preserved on the muddy bottom. The flora was dominated by zosterophylls, primitive 'ferns' (Flabelliopteris), seed plants, herbaceous lycopods (eg. Colpodexylon), tree lycopods (Leptophloeum and Kowieria) and Progymnosperm Archaeopteris forests. These, together with a number of other species comprise a remarkably diverse Late Devonian flora.
Some fish appear to have inhabited the estuary throughout their lives, as we can infer from fossils preserving a range of life sizes from juveniles to adults. These were mostly placoderms (‘platy-skins’), such as the bottom dwelling Bothriolepis africana, and Africanaspis doryssa, which had a large spike on its back. The placoderm Groenlandaspis riniensis was the most commonly preserved fish inhabiting the estuary. As in modern estuaries, some marine fish entered the river mouth to spawn, or gave birth to live young within the estuary. Juvenile coelacanths (Serenichthus kowiensis) lived (and sometimes died) within the estuary, but the adults would have returned to the ocean. Sharks also entered the estuary periodically to bear young and to hunt, and left evidence of their spines, teeth, skin and cartilage. Many-toed tetrapods (Umzantsia and Tutusius) would have made use of muscled forelegs to manoeuver about the shallows (where baby fishes would have hidden in the charophyte meadows) and may have been able to make brief excursions onto land. The top predator was Hyneria, a more than 3 metre long lobe-finned fish. Whereas, a 1.5 m long eurypterid (Cyrtoctenus wittebergensis) was a bottom dwelling, mudraking arthropod.
Climate
During the Famennian, the warm Devonian climate was changing with the eventual onset of glaciation at the poles. This was synchronous with a significant drop in atmospheric CO2, which may have been indirectly caused by novel Devonian forests (2). Tree fossils at Waterloo Farm, (eg. Archaeopteris and Leptophloeum) are consistent with a greenhouse climate in which Late Devonian forest ecosystems extended closer to the poles than today.
References:
1) Gess, R. W., & Whitfield, A. K. (2020). Estuarine fish and tetrapod evolution: insights from a Late Devonian (Famennian) Gondwanan estuarine lake and a southern African Holocene equivalent. Biological Reviews, 95(4), 865-888.
2) Gess, R., & Ahlberg, P. E. (2018). A tetrapod fauna from within the Devonian Antarctic Circle. Science, 360(6393), 1120-1124.
3) Hiller, N. & Taylor, F. F. (1992). Late Devonian shoreline changes: an analysis of Witteberg Group stratigraphy in the Grahamstown area. South African journal of geology, 95(5), 203-214.
1) Gess, R. W., & Whitfield, A. K. (2020). Estuarine fish and tetrapod evolution: insights from a Late Devonian (Famennian) Gondwanan estuarine lake and a southern African Holocene equivalent. Biological Reviews, 95(4), 865-888.
2) Gess, R., & Ahlberg, P. E. (2018). A tetrapod fauna from within the Devonian Antarctic Circle. Science, 360(6393), 1120-1124.
3) Hiller, N. & Taylor, F. F. (1992). Late Devonian shoreline changes: an analysis of Witteberg Group stratigraphy in the Grahamstown area. South African journal of geology, 95(5), 203-214.
Palaeomagnetic reconstruction of Gondwana during the Late Devonian, adapted from Domeier and Torsvik (2014). The South Pole is indicated by a star. Radial lines indicate 60 and 30 degrees latitude. A yellow dot shows the position of the Waterloo Farm locality. Green shading indicates imagined coastal lowland forests.