A fossilized bone from a dinosaur belonging to the Spinosaur family found in the Chapada do Araripe region in the state of Ceará, Brazil helped our team of researchers identify another piece of the puzzle that is this group’s evolution. The results were published this week in the journal Cretaceous Research. Spinosaurids are large predatory dinosaurs that lived during the Cretaceous period popular because they rival the famous Tyrannosaurus rex in size and due to their apparition in the third movie from the Jurassic Park franchise in which a giant sail-backed Spinosaurus defeats the protagonist dinosaur. The Spinosaurid group is very enigmatic, because the original Spinosaurus material was destroyed during a WWII bombing, so scientists spent a long time trying to understand what these carnivorous dinosaurs were like. An unsettling question about these predators has always been their lifestyle. Several aspects of these animals’ anatomy like the shape of the skull and teeth for example, suggest that despite being really large, – some species measuring more than 13m in length they were piscivores. It was known that there was an adaptation for piscivory. Very recently more materials were recovered until in 2014 a paper was published changing the way we see Spinosaurus aegyptacus which was an animal very adapted to being in the water, with a more quadrupedal posture and more aquatic. But not all spinosaurids were like that. Baryonyx, Suchomimus, they had apdatations to eating fish but were mostly bipedal so they weren’t exclusively semi-aquatic like Spinosaurus aegyptiacus But there was a relative of Spinosaurus that lived here in Brazil, a dinosaur sometimes called Irritator and another called Angaturama. It is not known if they’re the same animal because they were described from different parts of the skeleton. Angaturama from the tip of the snout, and Irritator from the rest of the skull and no other part of the body was formarly described. So despite having part of the tooth overlapping from one skull to the other, they belonged to different individuals. The piece that belonged to Angaturama limai was from a much bigger individual than Irritator’s skull. So we know that there were at least different specimens. But it’s not possible to tell wether they are the same species with the material currently available to science. We need to do more excavations, more research to get more material. But there are lots of fossils of these animals from Ceará still being described in the National Museum so there’s going to be a lot of news from our colleagues there so we can better understand the situation of brazilian spinosaurids. Ibrahim and colleagues described for the first time an adaptation in the spinosaurids’ skeleton that made it denser, and so useful for a semiaquatic lifestyle. The news that our work, published this week in the international journal Cretaceous Research, brings is that these bone adaptations to a semiaquatic lifestyle were already present in dinosaurs of this family inhabiting northeastern Brazil since the early Cretaceous. The study was led by our team and had the collaboration of other brazilian colleagues, along with scientists from Italy, Germany and Thailand. We found that the bones of these spinosaurids from Ceará were dense like those of penguins e other animals that spend part of their lives in the water like sea lions and alligators. This adaptation in the skeleton helps these species to dive in the same way the lead weightbelts of scuba divers help them remain underwater. The higher bone density, as mentioned, had already been seen in the North African species Spinosaurs aegyptiacus by Ibrahim and colleagues, but it was not known how this adaptation appeared. With the discovery of this tibia, or leg bone, of this spinosaurid from the Araripe region we could see these fossilized cells in a very dense tissue and that these animals, the closest relatives of the Moroccan Spinosaurus which was very well-adapted to living in the water, moreso than Baryonyx and Suchomimus, would also have this adaptation that made it easier for it to dive in shallow waters allowing it to catch fish from within the water instead of fishing from the shore like most other spinosaurids did. That is very interesting news because now we know that this novelty of a dinosaur being in the water while fishing was not something exclusive of the Saharan dinosaurs from the Middle Cretaceous and later. This adaptation appeared in Spinosaurus relatives from Brazil at least 10 million years earlier, in Ceará. Apart from Angaturama and Irritator, of which we have different parts of the skull, and this other material that is being described at the National Museum that belongs to a much smaller animal, probably a juvenile, this material that is now here in the laboratory in São Carlos belongs to the largest spinosaurid known from Ceará and the Araripe Basin. By comparing the approximate sizes of Angaturama, Irritator, and the material still being described at the National Museum we find that this new spinosaurid from the Araripe Basin could have been about 10 m (32.8 ft) long. According to the bone tissues we found, we determined that the individual was a subadult so it would still grow even larger, and was growing quickly when it died. An adult may have reach the size range of Spinosaurus, Suchomimus or Tyrannosaurus rex for example. The highlight of this paper is the denser bones that would make the animal’s skeleton heavier. The function of this was to make the skeleton into a sort of ballast that helps an organism to dive. The curious thing is that this adaptation evolved several times independently, in various animal groups and among dinosaurs specifically, the spinosaurids stand out because of this characteristic since they went contrary to the evolution of other dinosaurs that were, generally speaking, evolving to have lighter and lighter skeletons. An extreme of this trend is observed in birds, that have “hollow skeletons” as is popularly said. But the spinosaurids were going in the opposite direction so they evolved a way, which was the same biological solution found by several other groups like some mammals, crocodilians. They found a way to make their skeletons heavier to aid in occupying this semiaquatic niche. Apparently, along the evolution of this group, denser skeletons were selected for that would help in this semiaquatic lifestyle. The cool thing about the paper is that while other researchers had already observed that in the skeleton of Spinosaurus aegyptiacus this characteristic of dense bones, we now see that in brazilian spinosaurids that lived 10 million years before Spinosaurus. So this adaptation was already present in the group much earlier than previously thought. The next step is to investigate even older species to check if this adaptation is even more basal to the group that is, if it appeared earlier still. Now we change the scenery of Brazil’s Araripe basin. This big predator, that we already knew of, was present in this ecosystem and could interact much more with the aquatic environment. Because of this adaptation, it could literally be in the water, hunting. This renews our perspective of these animals from the past. And another thing that the paper brings forth is that we put together everything that was known about the fauna from the Araripe basin and create a hypothetical food web a food chain for this environment in which the spinosaurids would be the apex predators living in this transition between land and water. There are several other questions yet to be answered. For example, wether this evolution coincides with the formation of a great system of lakes between South America and Africa during the early opening of the Atlantic Ocean. So these dinosaurs were geographically positioned in this region where great lakes were being formed that were the precursors of what would become the Atlantic Ocean. We have yet to understand this relationship more clearly. Another important matter is to understand the evolution of gigantism in the spinosaurid group and wether it is also associated with this adaptation to a semiaquatic environment. We know of some living groups like the whales in which the gigantism is associated with an aquatic lifestyle Could it be that in spinosaurids in general gigantism is also associated with a semiquatic lifestyle? That’s another question that also needs to be answered, so the studies must go on. That’s why we need to invest more in paleontology. We need to invest more in excavations, in collections of the Araripe region and other regions of Brazil so we can better understand how this fantastic group evolved. Brazil offers a key time and place in the past for our understanding of the evolution of this group of predatory dinosaurs. The great importance of this study, despite the collaboration of international researchers, is that it was mostly done by brazilian researchers, with brazilian material. This shows the great importance of this kind of work involving brazilian researchers developing leading-edge research related to paleontology with great relevance to international science. We plan on continuing to working with these kinds of organisms and, in the future, producing more material related to the study of paleobiology, paleoecology and these dinosaurs’ evolution itself. You can help us make more videos like this one by making a donation through our channel. Join other supporters and help make our dream of disseminating science freely in our country come true.