This week's beast is a special dinosaur that helps us understand more about the appearance and lifestyle of its family. Check out Irritator challengeri!
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| Irritator life reconstruction in watercolor by Christopher DiPiazza. |
Irritator was a meat-eating dinosaur that lived in what is now Brazil during the early Cretaceous period, between 113 and 110 million years ago. From snout to tail it would have measured between 20 and 26 feet (6 and 8 meters) and was a meat-eater when alive. The genus name, Irritator, is certainly an unusual name for a dinosaur, and is in reference to the fact that the skull, which was originally found by a fossil dealer who attached fake bones to the end of it in an attempt to make it look cooler. When paleontologists actually got hold of the specimen they found it extremely irritating to undo all the damage to the specimen the dealer had done, so much so, they literally named it that. The species name is after the fictional character, Professor George Edward Challenger, from the novel by famous author, Sir Arthur Conan Doyle, The Lost World. (which takes place in Brazil and features dinosaurs)
Irritator was a theropod that belonged to the spinosaurid family, which also includes other dinosaurs, like Baryonyx and the gigantic and extremely popular Spinosaurus, itself. Most spinosaurs were relatively large theropods, Spinosaurus being arguably the largest theropod ever in some ways, but Irritator, at only 26 feet at the high end was a relatively smaller exception to this trend. Like all spinosaurs, Irritator possessed a long, narrow snout, lined with pointed cone-shaped teeth. Its nostrils were midway up the snout, instead of at the tip like those of most dinosaurs. It also possessed a thin bony crest in the midline of the top of its skull. Sadly only the skull of Irritator was ever oficially found. There are other spinosaur bones known from the same time and relative area as Irritator, but because there are no overlapping parts between these bones and the Irritator skull, it is impossible to positively say they are all from the same kind of dinosaur. That being said, if it was anything like other members of its family, it would have possessed strong arms with three curved claws on each hand, with the first finger of each hand possessing the largest claw. Irritator may have also possessed proportionally shorter legs, a sail of some sort on the back comprised of extended neural spines, and a flattened tail. These are all traits seen in Spinosaurus, which is thought to be closely related to Irritator even within the spinosaurid family.
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| Left and right sideviews of Irritator's skull. |
Irritator lived in an environment that would have been tropical in climate and abundant with large lagoons. It had a long snout lined with pointed teeth, plus possessed an extra bony palate on the roof of its mouth which would have helped the skull withstand pressure from twisting, an adaptation helpful if it was grabbing large struggling prey. A study published in 2023 suggested that Irritator's lower jaws would have actually been somewhat flexible and were able to slightly bow outwards to the sides, expanding he gape of the mouth. It also pointed out that Irritator's eyes were positioned facing forward, giving it particularly good binocular vision. All these traits suggest Irritator was adapted to hunting fish, and it probably was, however we also know that Irrirator ate pterosaurs at least some of the time. This is thanks to an Irrirator tooth found embedded into the spine of a pterosaur spine. We don't know if Irritator was actively hunting the flying reptiles or scavenging them, however.
When the skull of Irritator was first found by German and English scientists in the early 1990s, it was in the hands of a fossil dealer. The scientists bought the skull from the dealer and brought it back to Germany where it resides to this day. Current law in Brazil states that fossils found there must stay there unless given explicit permission by the government. Many believe, including many paleontologists, that Irritaor's skull should be returned to and housed in a museum in Brazil.
References
Cisneros, Juan C.; Ghilardi, Aline M.; Raja, Nussaïbah B.; Stewens, Paul P. (November 15, 2021). "The moral and legal imperative to return illegally exported fossils". Nature Ecology & Evolution. 6 (1): 1–3.
Machado, E.B.; Kellner, A.W.A. (2005). "Notas Sobre Spinosauridae (Theropoda, Dinosauria)". Anuário do Instituto de Geociências (in Portuguese). 28 (1): 158–173.
Machado, E.B.; Kellner, A.W.A.; Campos, D.A. (2005). "Preliminary information on a dinosaur (Theropoda, Spinosauridae) pelvis from the Cretaceous Santana Formation (Romualdo Member) Brazil". Congresso Latino-Americano de Paleontologia de Vertebrados. 2 (Boletim de resumos): 161–162.
Martill, D.M.; Cruickshank, A.R.I.; Frey, E.; Small, P.G.; Clarke, M. (1996). "A new crested maniraptoran dinosaur from the Santana Formation (Lower Cretaceous) of Brazil" (PDF). Journal of the Geological Society. 153 (1): 5–8.
Schade, Marco; Rauhut, Oliver; Foth, Christian; Moleman, Olof; Evers, Serjoscha (2023). "A reappraisal of the cranial and mandibular osteology of the spinosaurid Irritator challengeri (Dinosauria: Theropoda)". Palaeontologia Electronica. 26 (2). a17.
