''Cooyoo'' ("fish" in the

Yirandhali language Yirandhali (Yirandali, Jirandali), also known as Pooroga, is an extinct Australian Aboriginal language of Hughenden in Central Queensland. Yirandhali is a Pama–Nyungan language. Dixon (2002) speculates that it may belong in the Maric bran ...

) is an extinct genus of ichthyodectid fish known from the

Lower Cretaceous Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Lower Wick is a small hamlet located in the county of Gloucestershire, England. It is situated about five miles south west of Dursley, eight ...

. It contains a single species, ''C. australis'', known from the

Albian The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± 0.9 M ...

-aged Toolebuc and Allaru Formations of

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. ''C. australis'' was originally named by

Arthur Smith Woodward Sir Arthur Smith Woodward, FRS (23 May 1864 – 2 September 1944) was an English palaeontologist, known as a world expert in fossil fish. He also described the Piltdown Man fossils, which were later determined to be fraudulent. He is not relate ...

as a species of ''Portheus'' (now a probable synonym of ''

Xiphactinus ''Xiphactinus'' (from Latin and Greek for " sword-ray") is an extinct genus of large (Shimada, Kenshu, and Michael J. Everhart. "Shark-bitten Xiphactinus audax (Teleostei: Ichthyodectiformes) from the Niobrara Chalk (Upper Cretaceous) of Kansas. ...

'') in 1894, which was later amended to ''Xiphactinus''. Some phylogenetic studies have recovered it as an indeterminate

ichthyodectiform Ichthyodectiformes is an extinct order of marine stem-teleost ray-finned fish. The order is named after the genus '' Ichthyodectes'', established by Edward Drinker Cope in 1870. Ichthyodectiforms are usually considered to be some of the closest ...

, but later ones have found it to either be a sister of '' Unamichthys'', or more recently a true ichthyodectid related to ''

Ichthyodectes ''Ichthyodectes'' is an extinct genus of ichthyodectid fish which lived during the Late Cretaceous. Fossils of the species included have been found from Canada to Texas. Description ''Ichthyodectes ctenodon'' was a ichthyodectid around in ...

''. ''Cooyoo'' was a dominant predator of the

Eromanga Sea Eromanga or Erromanga may refer to: * Eromanga, Queensland, Australia **Eromanga Refinery, a small oil refinery in the town * Eromanga Basin, Australia ** Eromanga Sea, a prehistoric epicontinental sea that once covered the Eromanga Basin * Erroman ...

. As with all other ichthyodectids, it was a predator of smaller fish, and had large conical teeth to easily catch them. In contrast, ''Cooyoo'' itself was a prey item for larger animals, as a skull has been found with potentially fatal bite marks, which are referable to a

polycotylid Polycotylidae is a family of plesiosaurs from the Cretaceous, a sister group to Leptocleididae. Polycotylids first appeared during the Albian stage of the Early Cretaceous, before becoming abundant and widespread during the early Late Cretaceous. ...

plesiosaur, an

ornithocheiroid Ornithocheiroidea (or ornithocheiroids) is a group of pterosaurs within the extinct suborder Pterodactyloidea. They were typically large pterosaurs that lived from the Early to Late Cretaceous periods (Valanginian to Maastrichtian stages), with fo ...

pterosaur, or most likely the

ichthyosaur Ichthyosaurs (Ancient Greek for "fish lizard" – and ) are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia ('fish flippers' – a designation introduced by Sir Richard Owen in 1842, altho ...

Platypterygius ''Platypterygius'' is a historically paraphyletic genus of platypterygiine ichthyosaur from the Cretaceous period. It was historically used as a wastebasket taxon, and most species within ''Platypterygius'' likely are undiagnostic at the genus or ...

''. ''Cooyoo'' was initially described from a complete specimen with length about , and other fossil remains have been found including near-complete skulls. In 2011, a long intact fossil, nicknamed "Wandah", was discovered in north-west

. According to Rob Levers, Kronosaurus Korner museum founder and chairman, it was possible to detect the fish in the stomach of that specimen. ''Cooyoo'' is the largest bony fish known from the Eromanga Sea.

References

Ichthyodectidae Prehistoric ray-finned fish genera Early Cretaceous bony fish Albian genera Cretaceous fish of Australia Fossil taxa described in 1987 {{paleo-rayfinned-fish-stub