Acrylics, photography & digital rendering, 2011.
This work is the coverart of Earth and Environmental Science Transactions of the Royal Society of Edinburgh Volume 102, Issue 2 which contains my monograph describing the blue fishes in the foreground.
ca.380,000,000 years ago, Late Devonian (Frasnian), Eastern Gondwana
A vast tropical reef stretches into the horizon beneath the shallow sunlit seas off the great southern continent. The primary reef builders are clusters of stromatolites in the shallows, giving way in deeper waters to immense dome-like colonies of calcareous sponges. Fish abound as do coiled ammonoids, straight-shelled nautiloids, worm-like conodont animals, voracious sea-scorpions and legions of shrimp-like crustaceans. Countless species, predator and prey, weave and dash through the crystal clear waters in a riot of form and colour.
Beyond the reef front, the seabed abruptly plunges into a nearly lifeless abyss. Without polar ice caps to drive deep ocean currents, the deep sea is an anoxic wasteland. Carcasses of reef-dwellers that descend into the blackness are not scavenged. Secretions of anaerobic bacteria combined with the surrounding lime-saturated water soon encase the body within a stony coffin of calcium carbonate. These creatures are destined for immortality.
July 2005, Museum Victoria Gogo Expedition, Mt Pierre Station, Western Australia
It was my first trip to the Gogo Formation. On the ground were endless fields of orange limestone nodules of which we set about splitting them with hammers to reveal the contents within. 9 times out of 10... nothing. But every now and then we would find a life from ages past revealed to us.
I was searching in a narrow valley called Bugle Gap. I picked a random nodule and swung my rusty estwing. There before me was a perfect actinopterygian in lateral view. I was struck by it’s convex dorsal contours and would from then on refer to it as the “hunchback”. For the first time in 380 million years, the light of day glinted against the squamous flanks of this little fish.
2006, Melbourne Museum, Victoria.
I was puzzled. I had assumed that the hunchback was an example of Mimia toombsi , a common species of Gogo actinopterygian described by Brian Gardiner and his student Alan Bartram at the Imperial College, London back in 1977. Before the discovery of the Gogo fishes, Paleozoic actinopterygians were preserved either as flattened bodies or isolated bits and pieces. Gogo actinopterygians like Mimia were perfectly preserved in 3 dimensions on the inside and out, revealing previously unknown details of the braincase and gill arches.
After some excellent preparation work by David Pickering, I could see that my hunchback’s cheeks and jaws looked about right for toombsi, but the scales were too small and the skull roofing bones had different proportions. Additionally, the name Mimia was invalid as a fish genus – it had already been taken by a Mexican butterfly.
June 2011, Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, China
After years of revisions, doodling and mindless procrastination, I finally sent my final corrected monograph in which, with the blessing of Brian Gardiner, I renamed his genus Mimipiscis (“Fish of the Mimi dreamtime beings”). I designated my hunchback as the holotype of the second species, Mimipiscis bartrami, after the presumably late Alan Bartram who vanished in Morocco in the 1970s.
The little fish had a story to tell regarding life in the ancient seas and the early evolution of a major living vertebrate clade. We know that the Gogo reef was an early center of ray-finned diversification, with at least 5 species present (most other Devonian faunas have only 1 or 2 actinopterygian species). We also know that M. bartrami was likely part of an endemic radiation of Gondwanan marine ray-fins, the Mimiidae (along with M.toombsi and Gogosardina coatesi.
Fossil taxa do not “belong” to anyone. But, deep down I will always consider Mimipiscis bartrami to be *my* fish.
This scene represents life in the Great Devonian Barrier Reef of eastern Gondwana, as based on fossil data from the Gogo Formation of Western Australia. Taxa depicted are:
Mimipiscis bartrami = basal actinopterygian. Small blue fishies up about 13 cm in length.
Compagopiscis croucheri = arthrodire placoderm. Black-spotted pale fish. This foot-long predator is one of the most commonly found fossil taxa in the Gogo. Arthrodires were the most diverse group of fishes on the reef (about two dozen species).
Eastmanosteus calliaspis = big arthrodire placoderm. At over 2 metres in length, the biggest and meanest mother on the reef.
Robinsondipterus longi = dipnoan (lungfish). About 75 cm long. Lungfishes (note that probably none of the Gogo lungfishes actually had lungs) were the wrasses and parrotfishes of the Devonian reef, crushing or scraping off their food with distinctive palatal toothplates. About 12 species are known from the Gogo.
Hibbarddellid conodont animals = googly-eyed worm things. The tooth-like remains of many species of conodont critters are commonly found as microfossils in Gogo sediments. They were a favoured prey item for early actinopterygians like Mimipiscis. One bartrami specimen has the remains of two conodont animals (representing two separate species) inside it's tummy.
Schugocaris wami = the most common remains of large animals found in the Gogo are of phyllocarid crustaceans, weird shrimp-things that look like a taco shell with a prawn-tail sticking out the end of it.
REFERENCE: Choo, Brian (2011), Revision of the actinopterygian genus Mimipiscis (=Mimia) from the Upper Devonian Gogo Formation of Western Australia and the interrelationships of the early Actinopterygii. ]Earth and Environmental Science Transactions of the Royal Society of Edinburgh Volume 102, Issue 2. pp 77-104.