Crocodile tears means hypocrisy. They are not shed out of pity for prey but because it is a behavior to expel excess salt from the blood. A structure for expelling salt, like in crocodiles or seabirds, has been found in a dinosaur skull. In other words, dinosaurs also shed crocodile tears.
Researchers at OPHIS Paleontological Museum Reptile Center in Italy released on May 23 in the international journal Historical Biology that Spinosaurus, a dinosaur that lived 98 million years ago in what is now eastern Morocco, likely prevented excessive accumulation of salt in its blood thanks to salt glands located above the eyes.
Spinosaurus in Latin means backbone lizard. As the name suggests, the vertebrae extend vertically from the spine to form a sail-like shape. It appeared in the movie Jurassic Park III as a dinosaur that overwhelms Tyrannosaurus. Although Spinosaurus appeared 25 million years after Tyrannosaurus and the movie's showdown is fictional, its body length is 14 m, dwarfing Tyrannosaurus' 12 m.
◇Lived in brackish zones where seawater and river water meet
The Spinosaurus in Morocco is presumed to have lived in brackish zones where seawater and river water meet. An analysis of the skull using CT (computed tomography) images found a recessed area above the eyes. The researchers inferred that salt glands and blood vessels that filter salt from the blood were located there. Highly concentrated brine is expelled through the salt gland ducts into the nostrils.
Animals today also expel excess salt from the body in the same way. Birds and reptiles have salt glands in one of three places: the top of the skull, around the eyes, or the tongue. Penguins and gulls have them just above the eye sockets. Sharks and rays that live in the sea have salt glands in the rectum.
To test the salt gland hypothesis, the researchers compared skull fossils of several Spinosaurus species that, like the Moroccan dinosaur, lived during the Cretaceous period of the Mesozoic era (145 million to 66 million years ago). As expected, species that lived in high-salinity environments such as seawater or brackish water showed salt glands, while species that lived in low-salinity freshwater rivers lacked them. David Hone, a professor at Queen Mary University of London, said, "A really neat study and very interesting results," adding, "It is impressive that such data were drawn from a limited set of fossils."
The discovery appears likely to reignite academic debate over Spinosaurus. The scholarly community has long been split over this carnivorous dinosaur. One side says it was an aquatic hunter that swam by sculling its tail like an oar, while the other counters that if it dived, it could not handle its massive body and instead stood at the water's edge to snatch fish.
David Martill, a distinguished professor at the University of Portsmouth, said, "The discovery of salt glands supports the claim that Spinosaurus led an aquatic or semi-aquatic lifestyle," adding, "If it stayed in the water for long periods, salt glands would have helped." The Italian team, however, said a different explanation is also possible. Andrea Cau, the corresponding author of the paper, said, "Even if Spinosaurus hunted like a wading bird such as a heron, salt glands would have helped."
◇A species that lived 1,000 km from the coastline
Debate over Spinosaurus began a century ago. The first fossils of this dinosaur were unearthed in 1915. Scientists at the time, noting its crocodile-like jaws and teeth, inferred that it walked along the water's edge like a modern grizzly bear and caught fish. Then, in the 21st century, with the complete excavation of tail vertebrae in Morocco, its image shifted to that of a diving, aquatic dinosaur.
Spinosaurus also had vertically oriented bones in its tail like those on its back, forming a shape like a fish's fin. In 2020, a team led by Nizar Ibrahim at University of Detroit Mercy released in Nature that Spinosaurus hunted in water by moving like an eel using its long tail. In 2022, they released in Nature that Spinosaurus had high bone density like penguins, which made it advantageous for diving without floating.
There was no shortage of rebuttals. A team led by Paul Sereno at the University of Chicago argued in a 2024 paper released in the international journal PLoS ONE that large terrestrial animals such as elephants also had high bone density to support their immense body weight. He contended that Spinosaurus stood on two legs like a heron or stork to catch fish.
Sereno said research results released as a Science cover paper in February were a decisive blow to the aquatic dinosaur theory. The team excavated Spinosaurus mirabilis, which lived 95 million years ago, in Niger, Africa, during two expeditions in 2019 and 2022. Surprisingly, the fossils were found inland, 1,000 km from the coastline. Until then, bones and teeth of the Spinosauridae family were mostly found in coastal sedimentary layers, leading to the inference that they were fully aquatic dinosaurs.
When the University of Chicago team classified animals based on the relative lengths of the jaw, neck and hind limbs, mirabilis sat right next to large wading birds like herons. Sereno said, "Mirabilis would have had no trouble walking through 2 m-deep rivers on its sturdy legs," and claimed, "The large crest, which would have been 50 cm tall, likely served, like modern waterbirds, to show off from a distance with bright colors." Scientists' love for Spinosaurus looks set to continue.
References
Historical Biology(2026), DOI: https://doi.org/10.1080/08912963.2026.2669954
Science(2026), DOI: https://doi.org/10.1126/science.adx5486
PLoS ONE(2024), DOI: https://doi.org/10.1371/journal.pone.0298957
Nature(2022), DOI: https://doi.org/10.1038/s41586-022-04528-0
Nature(2020), DOI: https://doi.org/10.1038/s41586-020-2190-3