’Jurassic Park’ in St. Petersburg
Jurassic Park, an acclaimed action film set on a fictional island inhabited by de-extinct dinosaurs, was released nearly thirty years ago. Yet, it still remains in the top 100 highest-grossing movies of all time, with over 2,000 competitors behind it. The motion picture owes its stunning success partly to the previously unseen special effects, but its plot is no less remarkable. Its focus is on a unique opportunity for human to meet animals that lived on our planet hundreds of millions of years ago.
To get an idea of how Earth looked like in the distant past, one does not have to go far - just look attentively at today's living creatures. Some ancient animals may resemble their progenitors; some organisms are no longer found. The others have survived without losing their original form.
Cyanobionts are among the first inhabitants of the planet to have populated marine waters and freshwaters, and therein they live to date. The bacterial-like ancestors of these micro-organisms lived 3.5 billion years ago and were capable of photosynthesis. Because of them, the amount of oxygen in the atmosphere soared, and life forms started evolving. Modern cyanobionts retained the ability to produce oxygen. They belong to the few living things that can convert atmospheric nitrogen into usable forms, essential for the rest of the organisms. It is impossible to know how now-extinct cyanobionts looked like. However, a metabolic by-product of theirs has been preserved till the present day. It is stromatolites, layered carbonate structures.
The outer appearance of the first large multicellular animals also remains a mystery, as those had no skeletal structures. Their bodies' shapes were so peculiar that some scientists believe they represented a separate kingdom level category, now non-existing, Vendobionta. These enigmatic organisms' soft parts are rarely preserved and hence hardly ever found in the rock. Each impression of soft tissues of 'vendobiont' fossils is therefore unique. Whether these creatures left any descendants is for now unclear.
Neither was it easy to find living relatives of trilobites, a group of extinct arthropods that existed in oceans for over 250 million years. They dominated the planet longer than the dinosaurs did before they finally disappeared. Their fossilised remains are nowadays found in great numbers in various parts of the world: the UK, China, Canada, the USA, Germany, Morocco, the Arctic Ocean's shores, even near St. Petersburg. Thanks to well-preserved fossils, scientists have managed to identify tens of thousands of species by now.
The closest living relatives of trilobites are, perhaps, horseshoe crabs. Their bodies are also protected by a hard carapace, yet their abdomen is soft. A particularly striking feature of horseshoe crabs is that their blood, called hemolymph, is blue. Such an unusual colour is due to the copper present in the liquid. Horseshoe crab blood is highly valued, for it clots when exposed to even a tiny amount of contamination. Hemolymph has recently found use in making a vaccine against coronavirus.
Sea lilies, marine animals, also known as crinoids, on the other hand, live both in shallow water and in the depths of any ocean. The surviving species of crinoid emerged approximately 250 million years ago. A predatory sea creature similar to a flower has a cup-like central body connected to a stem and a set of rays (arms). The arms are raised upwards to trap small crustaceans and pass them on to the mouth located on the upper-central side of the 'cup'.
As time had passed, numerous fish species evolved, with crossopterygians among them. They were the largest and the strongest predator to have inhabited prehistoric lakes. It was long thought Crossopterygii had been driven to extinction. Still, a population of theirs survived, and in 1939 it was discovered in the coastal waters of South Africa, near East London. A weird-shaped fish covered by thick scales was drawn out of the water by an old fishing trawler with the rest of the catch. The fish's fins resembled paws, whilst it had a three-lobed tail. It was, as it turned out, a living species of crossopterygians that appeared at the dawn of the planet. Over millions of years of existence, their body form and behaviour have not changed. Nowadays, there are virtually no other living organisms on Earth like them.
The discovery of coelacanths, constituting the only order of fish within Crossopterygii to have survived to date, became the most significant zoological discovery of the 20th century. Fishing them is strictly prohibited, and their populations are being monitored. Despite this, Latimeria are declining in numbers, which is attributed to illegal fishing by locals.
The first amphibians evolved from certain crossopterygians. Stegocephalians, reaching up to 5 m in length, lived in swamps, lakes and rivers. Modern toads look somewhat similar to those ancient giants.
Alongside amphibians, the first reptiles came along, with dinosaurs being undoubtedly the most well-known of all. They inhabited Earth's land surfaces, regardless of terrain, came in all sizes - ranging from as little as a modern chicken to as big as a multi-storey house. One animal that has survived to this day is the dinosaur-like Komodo dragon, endemic to Indonesia. Last year, the eponymous island of Komodo was even considered by the Indonesian government as a location for a 'Jurassic Park' - a place for tourists willing to see ancient animals. As the government saw it, tourists would be observing Komodo monitors in their natural habitat, an area they have been living in for about a million years.
Scientists have found out that the brains of these animals are similar in structure to the brains of dinosaurs and differ from those of all other living beings. As a result of their size, Komodo dragons can kill even such large animals like buffaloes and monkeys. Outwardly slow and sluggish, this species of monitor lizards can run fast, swim and dive, and even climb trees. Usually, the lizard catches its prey in a brief sprint and then bites it, followed by the victim's death within several days due to the toxicity of the animal's saliva.
Birds are the only dinosaurs' remaining descendants. Surprisingly, those morphological features, which are often considered avian, are, in fact, inherited from dinosaurs. These include plumage, lightweight skeleton, homeothermy and others. The similarities between the two animal species are supported by genetic studies. For instance, birds were found to also have genes responsible for forming a long tail or teeth. These genes are in a kind of dormant mode, but they can be reactivated. It means it is possible to get a bird with the characteristic appearance of a dinosaur.
Giant reptiles did not populate only lands but also seas. One example of marine reptiles would be extinct ichthyosaurs that looked similar to dolphins but were bigger - up to 15-16 metres in length. Another creature that lived in the sea depths is the mystriosaurus. It is a distant ancestor of now-existing crocodiles, which can be guessed if seeing how much alike their skull structures and habitus are. The marine predator had a long head with very sharp teeth, making it a successful fish hunter.
During the reign of dinosaurs, the most widespread marine aminals were ammonites, predatory cephalopods. They are related to now living octopuses, squid, cuttlefish and nautiloids. Nautiluses are the only extant cephalopods that have an external shell. Their shells may reach over 25 cm in diameter, whilst the giant ammonites of the past could grow up to 2.5 m.
The largest known land mammal is the indricothere. It is a giant-sized extinct rhinoceros. Although its exact size is unknown because of the incompleteness of the fossils, the giant's shoulder height could be about 5 metres, and its weight is estimated to have exceeded 15 tonnes.
Palaeontologists are working on reconstructing the appearance of the now-extinct organisms. They are the scientists who draw parallels between the animal species and decide how closely they are related. It may seem surprising, but until the mid-20th century, palaeontologists had not known how many fossil animals ever existed on our planet. For example, they mistakenly thought that 542 million years ago, no species lived on land. Then Ivan Yefremov, a Soviet palaeontologist, came along. He gained worldwide fame for merging geological and palaeontological data into a single science. He is the founder of taphonomy, the study of fossilisation patterns. Thanks to his work, it became possible to reconstruct animal communities of the past, identify their habitats and establish links between various species. Because of what Yefremov did for palaeontology, scientists no longer leave it up to chance but rely on topography data or examine rock samples. Thus they determine whether a particular location could be a source of dinosaur or ammonite remains or, perhaps, something entirely different.
Being a science fiction author, Yefremov described much of what he saw in his novels. He is the founding father of the Mining Museum's palaeontological collection in St. Petersburg.