An extraordinary discovery by a Grahamstown scientist was announced today in a prestigious international scientific journal. Africa’s earliest known fossil coelacanth species, the fossil remains of which were discovered outside Grahamstown by palaeontologist Dr Rob Gess, has been described in the Zoological Journal of the Linnean Society.
An extraordinary discovery by a Grahamstown scientist was announced today in a prestigious international scientific journal. Africa’s earliest known fossil coelacanth species, the fossil remains of which were discovered outside Grahamstown by palaeontologist Dr Rob Gess, has been described in the Zoological Journal of the Linnean Society.
Gess conducted the research while a Phd student at the University of the Witwatersrand. Three-hundred and sixty-million years ago on the outskirts of what is now Grahamstown, a coastal estuarine lagoon was home to shoals of baby primitive coelacanths.
They would have sheltered in shallow water among waterweeds in a quiet lagoon surrounded by large archaeopteris trees and giant club mosses.
They shared the lagoon with other, larger types of lobe-finned fishes, acanthodians or spiny sharks, early true sharks and several species of armour-plated fishes.
The lagoon would have opened out into the Agulhas Sea, sandwiched between South America and Africa which at that time were part of a single continent called Gondwana.
The lagoon waters would have flowed through a narrow mouth between sandbars, much like the estuaries along the Eastern Cape coast today.
When the juvenile coelacanths died their bodies settled to the bottom of the lagoon and were soon entombed together with the remains of other ancient Devonian life in fine-grained, oxygen starved mud. Over the millennia, the mud petrified transforming into the black shale that today provides the only record in sub-Saharan Africa of an ecosystem from a period that was crucial to the evolution of modern terrestrial vertebrates and plants.
Local palaeontologist, Dr Rob Gess, first discovered Africa’s earliest known fossil coelacanth species between the layers of black shale rocks found on Waterloo Farm bordering on the N2 highway.
He went on to painstakingly excavated tons of shale salvaged during road works operations and discovered many more specimens, a few of which are preserved in exquisite detail.
The specimens were prepared under a microscope and have allowed the species to be reconstructed in minute detail. They proved to be a new genus and species, which Gess analysed whilst attached to the Evolutionary Studies Institute of Wits University.
The new fossil dubbed Serenichthys kowiensis, is Africa’s earliest known fossil coelacanth species. It is described this week in the prestigious Zoological Journal of the Linnean Society by Gess and Professor Michael Coates of the University of Chicago.
Gess has collected more than 30 whole-bodied specimens so far, and, remarkably, all of these more or less complete coelacanths are juveniles measuring between three-and-a-half to five centimetres long.
This suggests that Serenichthys was using a shallow, waterweed filled bay of the estuary as a nursery, as many fish do today.
The Waterloo Farm coelacanth nursery predates a much younger counterpart, known from the 300 million year old Mazon Creek beds of Illinois in the United States.
This glimpse into the early life history of ancient coelacanths raises further questions about the life history of the modern coelacanth, Latimeria – which is known to bear live young, but whether they, too, are clustered in nurseries is not yet known.
The new species provides important additional information on the early evolution of coelacanths.
According to an analysis conducted by Gess and Coates, it is the Devonian species that most closely resembles the line leading to modern coelacanths.
Coelacanths are believed to have arisen during the Devonian Period (roughly between 419 and 358 million years ago). However only five species of reconstructable Devonian coelacanths have previously been described in addition to a number of very fragmentary remains.
None of these came from Africa, but rather from North America, Europe, China and Australia.
Following the naming of its living relative (after an Eastern Cape river), the species name of the new fossil form, kowiensis, is after the Kowie River which rises among the hills where it was found. The genus name, Serenichthys, honours Serena Gess, who provided land for the storage of more than 70 tons of black shale rescued from roadworks for ongoing research – in which all the new material was found.
Ten things about Waterloo Farm black shale discoveries
1.The thirty baby Serenichthys kowiensis found by Dr Rob Gess lived more than 120 million years before the first dinosaurs.
2.The new fossil species was discovered a mere 100km from the mouth of the Chalumna River, where the first living coelacanth was caught in 1938.
3.Dr Gess is not sure what killed the shoals of coelacanths that he uncovered, but at that time the world was heading toward a major extinction event at the end of the Devonian period.
4.Modern species of coelacanth are adapted for deep water living, but ancient coelacanths inhabited much shallower coastal waters.
5.Adult Devonian coelacanths were only about 30cm long, but their modern relatives can grow to almost two metres.
6.When the bodies of the young Serenichthys coelacanths were covered in mud on what eventually became Waterloo Farm, just outside Grahamstown, the area was about 15 degrees from the South Pole.
7.Africa was part of the southern supercontinent Gondwana, made up of Africa, India, Australia, Antarctica and South America 360 million years ago.
8.Dr Gess found the juvenile coelacanths in the same rocks that he discovered a 360-million year old scorpion (Gondwanascorpio emzanziensis) – the oldest land living animal ever found in Africa or anywhere in Gondwana.
9.He has found many other important fossils in the Waterloo Farm shales including the world’s oldest fossil lamprey.
10.The black shales have to be protected from the rain otherwise they revert back into the mud that they once were.
A man and his rocks
Two days a week, Dr Rob Gess, sits on the bench of a dusty picnic table in front of one of the two sheds where he stores 70 tons of rocks.
The table is piled high with the shale rocks as he sets them, one at a time, on a cleared space where he can split the 360-million-year old layers from each other.
As a highly regarded palaeontologist who can claim articles published in Nature and other prestigious journals, Gess works with quaintly improvised tools to make his discoveries.
He taps the flat part of a worn hand chisel onto the back of a battered kitchen knife to wedge the blade between layers of black shale. Tap, tap… tap. It penetrates the rock and he gently prizes it apart and meticulously examines the newly revealed surface for signs of a fresh discovery.
Most of the layers display nothing new at all.
Some show trails where plant material might have dragged along the bottom of the Devonian lagoon and others reveal a piece of seaweed hidden from view for so long.
If it looks potentially interesting, he puts it on a separate pile on his table – if not, he throws it onto an elongated heap of chips along a row of cacti.
He says the acid in the rocks seems to nurture the cacti and he hopes that soon there will be enough of them to hide the unsightly sheds from view.
Gess says that maybe once a day he is lucky and exposes a fossil fish which he examines for a preliminary identification always hoping that perhaps it is something special. Sometimes it is unusual and worth taking a second look, but most of the time… it is pick up another rock… tap, tap tap.
Split.
It’s dusty work – after only a few minutes, his face is splotched with black shale dust as if he were working on a coal mine.
There is plenty of heavy lifting. After splitting one rock into its various layers and sorting out the slices into the hopefuls and the not-a-chances, he weaves his way through the heaps of boulders and brings back yet another large chunk of shale.
When he is not splitting rocks, Gess spends his time at the Albany Museum working on formal scientific descriptions of his discoveries. This process usually involves a lot of time staring into a binocular microscope.
When describing the Serenichthys coelacanths he spent a full week cleaning the rock matrix off just one of the best preserved specimens that allowed for minute examinations of the tiniest details.
The writing up process is exacting and time consuming. All related papers must be read and considered. The new piece of evidence must be fitted into the growing scientific understanding of the history of life. Its significance must be described in precise scientific terms. All links made to other scientific knowledge are carefully referenced.
Yet in spite of the intellectual and physical demands of his job, a day spent with Dr Rob Gess leaves one in no doubt that he wouldn’t have it any other way.
