Why do crocodiles like to look at the surface of the water? It turns out that this is the reason

Crocodiles have a habit of looking at the surface of the water. This practice is often described as predatory hunting. Crocodiles, which are carnivorous animals, are considered dangerous if they are close to humans.

A study by a team of International Paleobiology experts succeeded in solving this puzzle. The researchers found that the ancestors of today’s crocodiles that lived in the sea did not evolve like whales and dolphins. This prevents crocodiles from diving to great depths.

History of the Thalattosuchian Ancestors of Modern Crocodiles

This research, published today in the Royal Society’s Open Science, explains that Thalattosuchians who lived during the time of the dinosaurs stopped exploring the deep ocean because of their large snout sinuses. .

At the same time, whales and dolphins (cetaceans) evolved from land mammals to full-water mammals in a period of about 10 million years. During this time, their bone-covered sinuses shrink and they develop sinuses and air sacs outside the skull.

This reduces weight gain during deeper dives, allowing them to reach depths of hundreds (dolphins) and thousands (whales) of meters without damaging their skulls.

Before that, Thalattosuchians that lived in the Jurassic and Cretaceous periods were divided into two groups. The first group, Teleosauridae, which was shaped like the modern gharial crocodile, probably lived in coastal and estuarine waters. Meanwhile, Metriorhynchidae has a slender body with fin-like limbs and a tail and is thought to be able to live in the sea.

Research on Crocodile Ancestors

Researchers from the University of Southampton, the University of Edinburgh and other institutions wanted to see if thalattosuchians had undergone similar sinus changes to whales and dolphins on their evolutionary journey from land to sea.

To find out the answer, the research team used computed tomography, a special type of scanning, to measure the sinuses of 11 thalattosuchian skulls, 14 skulls of modern crocodile species, and six other fossil species.

The results of the study showed that the integrity of the sinuses of the brain decreased as the Thalattosuchian changed to an aquatic life. This is similar to the changes that occur in bees and dolphins.

Researchers suggest that this decline occurred as a result of several factors, such as their vitality, diving ability and the way they eat. Not only that, the researchers also found that when Thalattosuchians became full of water, the sinuses on their snouts expanded more compared to their ancestors.

“The shrinkage of the brain sinuses in Thalattosuchia mirrors the shrinkage that occurs in cetaceans, reducing during the semi-aquatic phase and then reducing further as they become fully submerged,” explained Dr. Mark Young, the lead author of the research, from the University of Southampton.

“Both groups also developed extracranial sinuses. However, while the sinus system of cetaceans helps regulate pressure around the skull during deep diving, the extensive sinus snout system of metriorhynchids prevents this from diving. deep,” he said.
“This is because the air in the sinuses at a deeper depth becomes dense and causes discomfort, damage, or even collapse of the nose because it cannot withstand the pressure anymore or equivalent,” Young said.

Unlike other animals that have this problem, whales and dolphins have efficient kidneys so they can filter salt from seawater. Reptiles and seabirds rely on salt glands to remove salt from their systems.

Dr. Young and his colleagues believe that the larger and more complex snout sinuses of metriorhynchids may have helped to purify their salt glands, similar to how marine iguanas work.

“The main problem for animals with salt glands is ‘build-up’, where the salt dries out and blocks the salt drains. “Modern birds shake their heads to avoid this, while marine iguanas sneeze to expel the salt,” said Dr Young.

“We believe that the dilated sinuses in the metriorhynchidae help to eliminate excess salt. Birds, like the metriorhynchidae, have sinuses that come out of the nose and pass under the eyes and when their jaw muscles grow, it creates a strong sound-like effect in their eyes. For the meriorhynchidae, when the sinuses got this effect, it compressed the salt glands inside the skull and created a sneezing effect, similar to modern marine iguanas.”

This study shows how major evolutionary trends occur and are shaped by species anatomy, biology, and evolutionary history.
“It is very interesting to discover how ancient animals, such as thalattosuchia, changed life in the sea in their own unique way showing similarities and differences with modern cetaceans,” said Dr. Julia Schwab, one of the authors of the paper from the University of Manchester.

Dr Young concluded: “Thalattosuchia went extinct in the Early Cretaceous, so we will never know for sure whether, given more evolutionary time, they could have merged with modern cetaceans or whether the need to mechanically drain their salt glands was an insurmountable obstacle. . passed for further specialization of water.”

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