Nature Asia
An Egyptian team documents a new species of fossilized catfish.
Among the invaluable fossil remains of some the earliest sea creatures at the natural reserve of the Whale Valley in Egypt’s Western Desert, an Egyptian team has uncovered an unknown marine species: a 37 million-
year-old catfish.
The paleontologists unearthed a near complete fossil of the ancient fish at the UNESCO World Heritage Site otherwise known as Wadi El Hitan and, after analysis, published their study in PLOS ONE1 this month.
Comparing the seawater specimen to other catfish from the Paleogene era, they proved it belongs to a new genus and species, naming it Qarmoutus hitanensis. Fragments of catfish fossils previously found in Egypt, in the Birket Qarun Formation, were freshwater species.
“The preservation of this catfish is spectacular and is the most complete one to be reported from Egypt since 1928,” says Sanaa El-Sayed, lead researcher of the team. With predicted body length up to two meters, its size is rare in catfish fossil records.
The paper lists the parts found, among which are an incomplete neurocranium, the upper and back part of a skull, the catfish’s two opercles which protected its gills, its Weberian apparatus (which connects the swim bladder to the auditory system), as well as a disassociated series of vertebrae. Many of its anatomical characteristics are well preserved.
“Such well-preserved specimens are not easy to find,” says Philip Gingerich, a vertebrate paleontologist at the University of Michigan, and the finder of the fossils of the 37 million-year-old powerful whale Basilosaurus Isis, also at Wadi El Hitan.
The study provides insights into the evolution of the aquatic group, say the scientists.
A theory raised in 2010 about the origin of the marine species family Ariidae, to which the newly discovered catfish belongs, estimated its genesis to be around 40 million years ago. The study confirms the theory and also confirmed that the origin of the fish’s galeichthyinae ariid subfamily is Africa. Only a few catfish crania, found previously, belonged to the same family.
“The new genus Qarmoutus provided additional catfish diversity, filling what was previously a gap in their history for the time and place,” Gingerich says. The researchers want to analyse the evolutionary history of the species and its biological relatives—what paleontologists refer to as phylogenetic relationships. They plan to add more fossils to the family tree.
“We think that adding more fossils into this tree will help to better understand its origin,” El-Sayed says.
Despite decades of intensive paleontological sampling from the 200-square-kilometre reserve, few studies have dealt with the valley’s fish fauna. Qarmoutus hitanensis is the first osteichthyan, or bony fish, found in the area that preserved whales. The Qarmoutus could have been food for archaic whale predators, such as the famous Basilosaurus Isis and Dorudon atrox, Gingerich says.
“Most of the vertebrate paleontologists who worked there were not interested in osteichthyan fishes,” says ElSayed. “The number of ichthyologists, researchers who are studying fossil fishes, around the world is small compared to for example the mammal scientists. This is due to the complexity of the group, huge variation among fishes and the long time span [they occupied], from 500 million years to the present.”