Ichthyosaurus, a Jurassic Reptile similar to a modern Dolphin
The Ichthyosaur is a Reptile. Yes, even if it resembles a Cetacean, or an Ichthyosaur Fish, it is a Reptile that does not lay eggs, but gives birth to live puppies, like a Mammal. Unfortunately, this wonderful animal that populated the seas of the lower Jurassic over 230 million years ago, before the Dinosaurs dominated the mainland, like them, became extinct without leaving any descendants.
Up to 6 meters long, the Ichthyosaur swam sinuous and fast, with that sleek and tapered body, completely transformed from that of its ancestors, primitive lizards that had adapted to living in water by changing their legs into fins and assuming a hydrodynamic shape, typical of many marine animals.
Ichthyosaurus communis is one of the best known of its genus, and its fossils are relatively frequent in the oldest rocks of the Jurassic in England and Germany. Some fossils have retained the imprint of the skin, which demonstrates how the ichthyosaur was equipped with a fleshy fin on the back and a crescent fin at the end of the tail, supported by the last caudal vertebrae which articulated by bending downwards in an L-shape. More similar then - by evolutionary convergence - to Pisces, rather than to Whales and Dolphins, whose tail fin instead develops horizontally, forcing them to a different swimming gait.
The ear bones of the Ichthyosaur were very robust, and probably conducted the vibrations of the water to the inner ear. However, the main sense the Ichthyosaur relied on during the hunt was to be sight. In fact, this predator had huge, very sensitive round eyes, protected by bones that formed an all-around annular structure. Other Ichthyosaurs, such as Ophthalmosaurus, possessed even larger eyes.
It was not their diet that caused the ichthyosaurs to go extinct
Perhaps the Marine Reptiles did not go extinct because they no longer had prey. It was thought that the extinction of the great marine reptiles was due to the disappearance of their prey, or large molluscs called Belemnites. But the discovery, in the stomach of an Australian Ichthyosaur fossil, of the remains of a small turtle and a bird suggest that the hypothesis was not entirely correct.
Dr. Benjamin Kear of the South Australian Museum in Adelaide, who found the fossil, thinks that not everything we know about the ichthyosaur diet is correct. His theory is that these Marine Reptiles were opportunistic predators, feeding on what they found, not just Mollusks or Fish. A newborn turtle and a (possibly dead) bird found in the sea are always excellent prey.
Their diet was certainly more extensive than previously thought and we have various evidence. Coproliths (fossil excrements) of Ichthyosaurs containing fish scales and numerous hooks of tentacles of Cephalopods (Belemnites) demonstrate the varied diet of these animals.
The disappearance of the Belemnites may therefore not have been the cause of their extinction, but rather the competition with other species. At the end of the period in which the last Ichthyosaurs lived, in fact, the first modern Bone Fishes began to appear in the sea. We then think of the large Plesiosaurs (other predatory marine reptiles). Perhaps these new species were much more efficient. To these we add the strong competitive pressure given by the gigantic and numerous Mosasaurs. All this together pushed the ichthyosaurs to extinction.
The last abundant meal of the Ichthyosaur
Amazing new snapshots from the past never cease to amaze us. In southwestern China, some paleontologists have found, inside the remains of a slightly larger Ichthyosaur, the fossil of a Talactosaurus. This is another extinct Triassic Reptile (250-200 million years ago approximately) similar to the Notosauri. The Ichthyosaurus had therefore preyed on the Talactosaurus.
The discovery is incredible. The Talactosaurus fossil, with its four meters in length, is one of the longest ever found inside a prehistoric marine reptile. The Talactosaurus was also present in Italy with two known fossils Askeptosaurus italicus and Endennasaurus acutirostris. The finding, described in detail in the scientific journal Science, is proof that the Triassic marine reptiles were super predators.
What do an Ichthyosaur and a Crocodile have in common?
Appearances are deceiving. Usually scholars, to understand what the animals they analyze the fossils ate, study the shape of the jaws and the type of teeth (if you want to know more about Teeth and Fangs take a look here). the prehistoric super predators were endowed with large and sharp teeth, with which to bite and tear the flesh of the prey. Thus, in fact, it was the Ichthyosaur that used its long conical teeth to grab prey.
However, some current species, such as Crocodiles, behave differently. While hunting large prey, they do not tear them apart with sharp teeth. In fact, to tear the flesh they rely on the force of the bite and violent rotational movements of the entire body with which they tear the victim's bones and tissues. In all likelihood, the Ichthyosaurs behaved in the same way. Despite their rounded and (apparently) harmless teeth, it seems therefore that their meals were not only based on Fish, Molluscs and Turtles.
Although there are no certainties, the researchers believe that the ichthyosaurus killed its prey and therefore did not find it already dead. This is because, if the body of the Talactosaurus had already been decomposing before being eaten, the limbs would have been dismembered and disconnected even before the tail. These, on the other hand, remained partially attached to the body, with the tail several meters away. All this therefore suggests a last, bloody fight, in which the ichthyosaur would have had the upper hand, albeit for a short time. The gastric acids of the ichthyosaurus did not consume the body of the thalactosaurus. As Ryosuke Motani, one of the authors of the research, explains, the Ichthyosaurus must therefore have died shortly after its last meal.
Ichthyosaurs in the world
The Ichthyosaurus was the first of the Mesozoic marine reptiles to be discovered. It was Mary Anning in 1810 together with her brother who found the first beautiful skeleton on the cliffs of Lyme Regis, in the county of Dorset, England. We all remember the film Ammonite - above a wave of the sea in 2020 that made it famous to a wide audience. In the film, the always good Kate Winslet, the protagonist of Titanic, to understand us, played the paleontologist. The film is a bit controversial because it also tells of the protagonist's relationship with the geologist Charlotte Murchison who seems to have no historical confirmation. In our opinion, however, the film is also worthy of the atmosphere of the time it recreates.
Returning to our first Ichthyosaur Fossil, most scholars believed that these remains belonged to a Crocodile, because at first only the skull was found. Only later, when the entire skeleton came to light, was the animal studied in detail. Scholars thus attributed the name of Ichthyosaurus ("lizard - fish"), not without some paleontological disputes.
In the same period the Anning also discovered the Plesiosaur and the Pterosaur. From that moment on, many finds of Ichthyosaurs in various parts of the world ended up under the name of Ichthyosaurus, transforming this taxon into a real “waste basket”. Only after careful analysis carried out towards the end of the twentieth century, did scholars reduce the commonly accepted species belonging to the genus to three. The 3 species are: Ichthyosaurus communis (the type species), Ichthyosaurus breviceps and Ichthyosaurus conybeari.
Italy, kingdom of Ichthyosaurs!
One of the most extraordinary and best preserved ichthyosaurs came to light in Italy, in the province of Varese, in 1993. It is called Besanosaurus, and it is the largest and most complete marine reptile ever found in our country. However, Italy does not lack as many flagships: Mosasaurs, Tanistrofei and Pterosaurs, just to name a few, too little publicized to do it justice.
Not only Ciro the Italian Dinosaur
We all know by now the famous Dinosaur "Ciro", the small Celurosaurus classified as Scipionyx samniticus. But if the Dinosaurs are a novelty in Italy, writes Cristiano Dal Sasso in his wonderful book Dinosauri Italiani (Italian Dinosaurs), other Reptiles of their contemporaries who lived on our territory, have been known for decades. Some even for a couple of centuries, so much so that their discovery contributed to writing the first pages of the history of paleontology itself. Remaining only to the Ichthyosaurs, "their remains have been found in the Dolomites, in Carnia and in the Marche Apennines, but for their abundance and state of conservation, the best known are those of Besano, coming from those stratified rocks known since the nineteenth century with the name of oil shale“ . From which everything and more comes from. There would still be a lot to talk about on this issue and maybe we will do it in the next articles who knows.
