Sankt-Peterburgskie Vedomosti: The knowledge of the Russian scientist proven useful in constructing the salamander "pedigree"
The ancient stem-salamander Marmorerpeton wakei became the subject of a special issue of the scientific journal Proceedings of the National Academy of Sciences. Among the authors, who are entirely British scientists affiliated with: University College London; the University of Oxford; the Oxford University Museum of Natural History, and National Museums Scotland, is the Russian palaeontologist Pavel Skutchas, Professor in the Department of Vertebrate Biology at St Petersburg University. Interestingly, Professor Skutchas has never even touched the found salamander fossil.
Master Survivor
On the Scottish Isle of Skye, you can meet palaeontologists wandering along the shore. At low tide, they collect fossils of ancient animals embedded in rocks. These finds come from local sediments aged 166 million years. Thus, the scientists found a three-dimensionally preserved skeleton of the oldest known salamander. The search, however, took almost half a century. In 1971, one fragment was discovered, in 2016 — another, three years later — one more.
‘I especially enjoy not having to talk about dinosaurs,’ admitted Pavel Skutchas. He often delivers popular science lectures. Of course, the public is eager for stories about ‘terrible lizards’. Although prehistoric salamanders that were contemporaries of the dinosaurs are really fantastic creatures. These amphibians are often confused with lizards, which are reptiles. The two appear very similar at first glance, but they are not difficult to distinguish. ‘Take a lizard in one hand and a salamander in the other. One has dry skin, the other — moist,’ Professor Skutchas explained. Lizards are well adapted to handling the heat and drought, whereas amphibians cannot tolerate the heat and they need moisture to survive.
Salamanders are very different in size: they range from about 3 to 180 cm in length.
Most lizards and salamanders reproduce by laying eggs. However, lizard offspring are born with limbs and they go out onto land. Salamanders, on the other hand, are born in the water with gills and throughout their larval stage they remain in the water.
Finally, lizards can re-grow severed tails, but their regenerative ability is not on par with that of salamanders. Salamanders can re-grow not only a tail but all sorts of tissue, organs and whole limbs if they need to. They can regenerate the lens of the eye and even the brain.
The key to understanding this unique regenerative ability may be related to salamander genomic gigantism. A human germ cell, for instance, has about 3.5 pg of DNA (a picogram (pg) is a trillionth (10−12) of a gram), while some salamanders have a huge genome — up to 120 pg.
We have a special interest in understanding the genome of tailed amphibians. Once we understand how their regenerative mechanisms work, we will try to apply this knowledge to our own needs.
Incorporating a species Marmorerpeton wakei into the phylogenetic tree has changed the idea of how all salamanders are related and what the early stages of their evolution are.
Prior to the discovery of Marmorerpeton wakei (aquatic, about 60 cm in length), the oldest salamander fossil was the complete skeleton of Karaurus sharovi from the Late Jurassic period, i.e. 150–157 million years ago. The fossil was found in the 1970s in Kazakhstan and is kept at the Moscow Palaeontological Institute of the Russian Academy of Sciences. Previously, many studies of ancient salamanders relied heavily on the Karaurus sharovi skeleton. It is sometimes called an "icon of palaeontology" or the "Archaeopteryx" of salamanders. The thing is, studies on Archaeopteryx formed the basis for the avian evolutionary history. Similarly, the "salamander" experts need to turn to the specimen found in Kazakhstan.
The fact of the matter is, Marmorerpeton wakei significantly changed the understanding of the evolutionary history of salamanders. Previously, it was thought that many of the Jurassic tailed amphibians were the earliest known representatives of modern salamander groups.
‘This theory was refuted as we showed that they were much more primitive, archaic salamanders,’ said Pavel Skutchas.
The first representative of modern salamander groups must have appeared as early as at the very end of the Jurassic period. Its remains are yet to be found.
The knowledge of the Russian scientist has proven useful in constructing the ancient salamander "pedigree". Professor Skutchas had previously examined the remains of tailed amphibians found in Central Asia and Siberia. This time, he had to study the fossil of the ancient amphibian found on the Isle of Skye on the monitor of his working computer at St Petersburg University. The international study became an example of researchers’ determination and ingenuity, indeed. Due to the pandemic restrictions, they had to master three dimensional visualisation techniques to analyse fossils.
Dinosaur gets a CT scan
One of the vexing issues of palaeontological analysis is that the fossil is often tightly embedded in the rock. Removing it from the rock may damage or even destroy it. There is also another issue. As the saying goes, ‘you cannot make an omelette without breaking eggs’, that is, you have to damage the shell to get access to its internal structure.
‘A hundred or even fifty years ago, scientists would cut fossil specimens with a circular saw to study their internal structures,’ explained Ivan Kuzmin, Candidate of Biology, Assistant Lecturer in the Department of Vertebrate Zoology at St Petersburg University.
They appear to have acquired new knowledge, but the specimen was destroyed and no longer available to the scientists.
Fortunately, modern research methods (such as computed tomography) enable scientists to analyse the specimen without damaging it. In this regard, a dinosaur or some kind of prehistoric crocodile is no different from a patient in a clinic. Quite literally, if the object of study does not fit into the university Micro-CT scanner, the scientists make an arrangement with a clinic to do a CT scan there.
Hundreds, tens of hundreds of pictures are made and loaded into a special programme, and then, a long and laborious process begins. Palaeontologists ironically call it "50 shades of grey" because it is difficult even for an expert to distinguish the remains from the rock. Bone by bone is painstakingly isolated on a monitor to make a three-dimensional copy of each. By the way, the rock can be virtually "cleaned", while the specimen is left undisturbed in a piece of stone.
3D-models can be rotated in 3D-space, "cut" into pieces, sent by e-mail to colleagues across the globe, assembled from fragments into a whole — like puzzle pieces.
It takes a month of work to take apart a virtual crocodile skull into virtual bones. By the way, even if the skeleton of an ancient creature is incomplete, it is still possible to establish many aspects of its locomotion and lifestyle, and you can learn about it "from the void".
Void is what remains of the brains of ancient animals — a cranial cavity within the empty skull.
Ivan Kuzmin is holding something that resembles a stone. This is a piece of the skull of ankylosaur Bissektipelta archibaldi, a Mesozoic armoured dinosaur with hulking forehead spikes and a massive club at the end of its tail. These creatures lived some 90 million years ago, for instance, on the territory of modern Uzbekistan.
2022 was the Year of Zoology at the University. 200 years ago, for the first time in Russia, a specialised department of zoology was established at St Petersburg Imperial University. That was the beginning of the university education in zoology in Russia.
Having studied the cranial cavity and 3D-models of the braincase of the ankylosaur, the scientists were able to get a fairly detailed representation of its brain structure. The brain of this four-metre beast — although a herbivore — was the size of a human thumb, about 26.5 grammes. The anatomy of the inner ear suggested it could hear frequencies from about 300 to 3,000 Hertz. These are quite low frequencies: the ankylosaur would have been able to hear a human speak, but not a mouse squeak. And judging by the fact that the cerebral hemispheres are smaller than the olfactory bulbs, ankylosaurs could sniff faster than they could think. Nevertheless, they existed on the planet for 100 million years.
‘Can you imagine: a large and heavily armoured animal. To turn around and look at something with its not very big eyes, it had to perform a lot of actions,’ Ivan Kuzmin noted. ‘It had an extremely developed sense of smell to get information from a distance. Indeed, smell can be detected before one can see a predator or food.’
‘For my colleagues and me, extinct and present-day animals are equal,’ stressed Professor Skutchas. ‘We treat dinosaurs as if they were alive now.’
‘Salamanders, even more so: they live in the pond of the Botanical Garden of St Petersburg University.’