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South Africa’s Unique Fossil Fish Faunas
By Dr. M. Eric Anderson
JLB Smith Institute of Ichthyology, Grahamstown, South Africa
The Devonian Period, starting about 410 million years ago and lasting 55 million years, is often called the Age of Fishes. Although most of the major groups of Devonian fishes are extinct, the beginnings of today's bony and cartilaginous fishes can be traced to about this time. Recent research and field work at Devonian fossil sites in South Africa by a team of scientists headquartered at the JLB Smith Institute has revealed this area to have had fish faunas hitherto unknown to science. Comparisons of the South African material with that from other areas has confirmed both our southerly position in the ancient continent of Gondwana and a worldwide trend in faunas shifting from characteristic local endemism to more widespread distributions throughout the Period.
Reconstructions of the earth's landmasses during the Devonian show the large, southern continent Gondwana, now comprising South America, Africa, Arabia, India, Australasia and Antarctica, to have its southern African (really southwestern) component at very high latitudes, mostly around 70-75 degrees south. The climate was cool but there was no polar ice cap. The continent Laurasia, now North America, Greenland and northwestern Europe, was tropical and was slowly moving toward Gondwana. Because of the distance and differences in climate both of these areas harboured their own characteristic (endemic) fish faunas, and Gondwana itself had a high proportion of eastern and western endemics at the beginning of the Devonian.
 The earliest South African Devonian fish fossils date from about 390 million years ago. The chondrichthyan (boney fish) skull shown here from the Western Cape was a major find: it is the oldest cranium (head) of its kind known in the world and is similar, if not identical, to specimens dated about 8 million years later found in Bolivia called
Pucapampella rodrigae. Computed tomography (CT) images studied by American Museum collaborator Dr. John Maisey have revealed the anatomy of the South African specimen. As a result, it and the Bolivian species are placed on the chondrichthyan family tree as a separate group, and primitive to, the other higher-order groups, the elasmobranchs (sharks, skates and rays) and chimaeras.
The cool-water South American/African fish and shelly marine invertebrate faunas of the time represent the Malvinokaffric biogeographic province. Almost all of eastern Gondwana, now Australia and Antarctica, was tropical and those faunas shared a closer connection with Laurasia across northern Gondwana (India, Arabia, southern Europe) than with cooler western Gondwana.
 The climate warmed in western Gondwana as the Devonian progressed and the cool-water faunas were slowly replaced by species of two distributional types — an east-west type and those with worldwide (cosmopolitan) distributions. Several sharks such as
Antarctilamna, represented by this tooth from the Western Cape, have been found all over the fragments of old
Gondwana.
Still, southern Africa never became truly tropical during the Devonian and, even with faunal exchanges occurring, the area became a refuge for relict species, or holdovers from earlier times.
 These include a few armoured fishes (placoderms) and a unique, whole-bodied "shark" found at Grahamstown. Pictured here, we named the latter
Plesioselachus macracanthus (primitive shark with a big spine) and it, like the Pucapampella material, is placed below the sharks, rays and chimaeras.
We have analyzed and published on all the known South African Devonian fish material, but what about the future? This looks bright indeed with new funding from South Africa's National Research Foundation to support field trips through 2005. Of particular interest are areas in the Western Cape's Prince Albert District and in the Cederberg Mountains about 200 km north of Cape Town. We are hoping to find more of the chondrichthyans there, but who knows what other oddities, previously unknown, await our hammers? News on our future discoveries will be reported to Science in Africa.
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