How did the whimsical Spinosaurus live and hunt? The recently proposed theory of the nimble swimming fishhunter is now being challenged by two paleontologists. According to their report, the giant with its oar tail was adapted to the water, but its characteristics still do not match an aquatic chase. According to them, he is more flexible in using all available food sources on land and in the water of the bank area. It may also be wading in the shallow zones with its long snout on the bottom and rummaging for prey – similar to today’s storks, say the researchers.
Terrifying and gigantic: At 15 meters long and weighing around 20 tons, Spinosaurus aegyptiacus was probably the largest predatory dinosaur of all time. The bizarre Cretaceous dinosaur entered the paleontological stage in 1912. However, the first known fossil from Egypt was lost to modern research: the find stored in Munich was completely destroyed in a bomb attack in 1944. Subsequently, only a few partial finds shed light on the characteristics of this spectacular and strangely built dinosaur. That only changed in 2014: paleontologists presented a very well-preserved fossil of Spinosaurus from Morocco.
A fast swimming hunter?
According to the results of the investigation, the animal had characteristics that suggested at least a semi-aquatic way of life. But how and what exactly the Spinosaurus could have fed on remained unclear. At first it was not assumed that the animals were mainly swimming, but rather ran through shallow water. But in early 2020 an examination of the tail brought a breath of fresh air to the discussion. The characteristics indicated that it was an oar tail that could provide effective propulsion in the water. The scientists concluded from the results of this study that Spinosaurus was “a highly specialized aquatic predator that pursued and captured its prey by swimming in the water”.
But, as David Hone of Queen Mary University of London and Tom Holtz of the University of Maryland at College Park point out, a tail adapted for swimming does not prove that Spinosaurus was actually an aquatic chase. Because some of today’s animal species swim with the help of such a tail without using it for chases. The two paleontologists have now prepared a new report on the animal’s suspected behavior, taking the new data into account. They compared the characteristics of Spinosaurus with those of other species of dinosaurs and various animals that live and hunt on land or in water today. In doing so, they compiled a systematic list of aspects of the various parts of the body and characteristics of Spinosaurus that may or may not fit an aquatic hunter lifestyle.
Too cumbersome
As they report, it became clear that there are several features that do not seem to fit the concept of the aquatic chase robber. In contrast, however, no aspects contradict a generalist way of life – various indications even speak clearly in favor of such behavior, the scientists report. “We tried to use the evidence we had to best describe his way of life. And what we found did not match the attributes that one would expect in an aquatic chase like an otter, sea lion or plesiosaur, ”says Holtz.
One of the most important aspects is the assessment of swimming ability. The researchers draw a comparison: “With their oar tails, unlike land animals, crocodiles are excellently adapted to swimming, but they are not specialized in actively hunting for fish because of their speed,” says Hone. According to the evidence, Spinosaurus had weaker tail muscles than crocodiles in relation to its body size and, due to its massive body, it offered a lot of resistance in the water. An active hunt for fish therefore seems rather unlikely. “He would hardly have been fast or efficient enough for that. Our results are much more in line with the theory of wading in shallow water, even if it seems a little less exciting, ”says the scientist.
More like wading in shallow water
Accordingly, Spinosaurus was a rather flexible predator of the bank area, which snatched any available prey on land or in shallow water. As the researchers report, there is evidence that it may be rummaging for prey in shallow water, similar to herons or storks. Features of its cervical vertebrae suggest that the long muzzle is often directed downwards. The breathing openings were also as far back as in the beaks of the birds and not at the top as in the crocodiles. It is therefore possible that the spinosaurs were with their snouts on the bottom in the shallow water to find hidden prey.
“Spinosaurus was probably more adapted than any other large dinosaur for hunting in the water,” emphasizes Holtz. “But that’s a different claim than that he was a fast swimmer chasing aquatic prey.” To conclude, however, Hone says, “While our study gives a clearer picture of the ecology and behavior of Spinosaurus, it still exists many open questions and details to be resolved and we have to keep re-examining our imaginations as we gather more evidence and data about these unique dinosaurs. This won’t be the last word on the biology of these amazing animals, ”says Hone.
Source: Queen Mary University of London, Article: Palaeontologia Electronica, doi: 10.26879 / 1110