An extinct species of lungfish discovered in Zimbabwe could mark the beginnings of a sea change in our understanding of the animals.
Close examination of Ferganoceratodus edwardsi suggests that many lungfish are more closely related than first thought, offering new insights into their evolution.
One man’s work to reveal the ancient species of southern Africa has been recognized in the name of a new species.
The fossil lungfish Ferganoceratodus edwardsi has been named in honor of Steve Edwards, a safari guide and amateur fossil hunter in northern Zimbabwe. With Steve having played an important role in the discovery of a phytosaur, a new dinosaur and now a fish, the team of paleontologists thought it was only right to highlight his contribution.
Professor Paul Barrett, a co-author of the research from the Natural History Museum, says, “Steve is an important force for paleontology, having discovered several Late Triassic sites in southern Africa.”
“This is a time in history when the rise of the dinosaurs was starting, and bony fish were diversifying. By sharing his discoveries, Steve is helping us to better understand this important moment in evolution.”
The team hope to return to the region with Edwards in the coming years, confident that there are many more fossils, and new species, left to find. The findings of their research were published in the Journal of Vertebrate Paleontology.
What are lungfish?
Lungfish are an unusual group of freshwater fish which have long drawn the attention of scientists. They are the closest living relatives to all animals with four limbs, helping to reveal how the ancestors of all amphibians, reptiles, birds and mammals might have lived.
The lungfish also have a range of abilities that set them apart from many other fish, including swim bladders that function as lungs. This allows the handful of living species, spread across Africa, South America and Australia, to breathe air as adults.
Perhaps the most fascinating thing about the lungfish, however, is that they’ve survived for around 420 million years. The earliest species are still recognizably lungfish-like and look similar to their living relatives.
This long evolutionary history gives them one of the strongest claims to the title of “living fossil.”
“Lungfish have a fairly paradoxical fossil record,” Barrett says. “Generally, we expect there to be fewer fossils as we go back in time, but it’s the other way around for lungfish.”
“Most of the preserved specimens come at the start of their evolution, when we find many different lungfish species with well-preserved skeletons. However, in the Mesozoic Era between 252 and 66 million years ago, we only find teeth and the occasional skull.”
“This is unexpected, as lungfish are thought to still be pretty common at the time, so there should be plenty of opportunities for fossilization. In fact, the fossil record gets even more sparse towards the modern day, to the extent we’re not certain how living lungfish evolved.”
Finding more Late Triassic lungfish is an important part of resolving these issues. Not only do their remains fill a gap in the fossil record, but they might also reveal how behaviors like dormancy and burrowing first evolved.
A visit to The Dentist
The site identified by Edwards is known as “The Dentist” thanks to the numerous fossilized teeth found there. Among these were fossilized tooth plates, which living lungfish use to crush shellfish, crustaceans, and a variety of other animals as part of their carnivorous diet.
These tooth plates are heavily mineralized, meaning they’re much more likely to fossilize than the cartilaginous lungfish skeleton. This means paleontologists often only have the teeth plates to identify different species.
They do this by examining the size and shape of the tooth plates, paying particular attention to the ridges. Small differences can be used to separate species, while larger differences like the number of ridges can be used to split more distant parts of the lungfish family tree.
While the team found that the teeth from The Dentist site were similar to a Madagascan species, they were confident enough in the other differences to name Ferganoceratodus edwardsi. Wider comparisons, however, suggested that large parts of lungfish taxonomy may need to be re-organized.
“By comparing the tooth plates from a variety of genera, we found that they’re often very similar,” Barrett says. “While we’re confident that the fossils indicate many different species of lungfish, we think that they all belong to the same group of close relatives, known as a genus.”
“It suggests that after first appearing in the Early Triassic in the southernmost supercontinent, Gondwana, Ferganoceratodus species spread throughout Africa and South America later in the Triassic. Their fossil record then becomes more sporadic in the rest of the Mesozoic, although they seem to have spread all over the world, with the last fossils found in the Late Cretaceous.”
Finding out exactly what happened to these lungfish will require finding more fossils from the Late Triassic, amid continuing excavations at The Dentist and other fossil-rich sites nearby.
“We’re planning to return to the site in the coming years, and hope that lungfish remains will be among the fossils we dig up,” Barrett adds. “We also hope to find more of the phytosaur we’ve previously described, as well as more dinosaurs.”
“More fossils will allow us to better compare this area of Zimbabwe to similar fossil sites in southern Africa, and put them into a wider context that lets us better understand what was happening in the Late Triassic.”
More information: Tom J. Challands et al, A new lungfish from the Upper Triassic of the Mid-Zambezi Basin, Zimbabwe, Journal of Vertebrate Paleontology (2024). DOI: 10.1080/02724634.2024.2365391
Journal information: Journal of Vertebrate Paleontology
Provided by Natural History Museum