Dinosaurs get all of the glory. However aetosaurs, a closely armored cousin of recent crocodiles, dominated the world earlier than dinosaurs did. These tanks of the Triassic got here in a wide range of sizes and styles earlier than going extinct round 200 million years in the past. Right this moment, their fossils are discovered on each continent besides Antarctica and Australia.
Scientists use the bony plates that make up aetosaur armor to establish completely different species and often do not have many fossil skeletons to work with. However a brand new research led by researchers at The College of Texas at Austin facilities on an aetosaur swimsuit of armor that has most of its main elements intact.
The swimsuit — referred to as a carapace — is about 70% full and covers every main area of the physique.
“We’ve parts from the again of the neck and shoulder area all the best way to the tip of the tail,” stated William Reyes, a doctoral pupil on the UT Jackson Faculty of Geosciences who led the analysis. “Normally, you discover very restricted materials.”
The analysis was printed in The Anatomical File.
Reyes and his collaborators used the armor to establish the specimen as a brand new aetosaur species — which they named Garzapelta muelleri. The title “Garza” acknowledges Garza County in northwest Texas, the place the aetosaur was discovered, and “Pelta” is Latin for protect, a nod to aetosaurs’ closely fortified physique. The species title “muelleri” honors the paleontologist who initially found it, Invoice Mueller.
Garzapelta lived about 215 million years in the past and resembled a contemporary American crocodile — however with rather more armor.
“Take a crocodile from modern-day, and switch it into an armadillo,” stated Reyes.
The bony plates that coated Garzapelta and different aetosaurs are referred to as osteoderms. They have been embedded instantly within the pores and skin and fashioned a swimsuit of armor by becoming collectively like a mosaic. Along with having a physique coated in bony plates, Garzapelta’s sides have been flanked by curved spikes that will have provided one other layer of safety from predators. Though crocodiles right this moment are carnivores, scientists assume that aetosaurs have been primarily omnivorous.
The spikes on Garzapelta are similar to these present in one other aetosaur species, however surprisingly, researchers discovered that the 2 species are solely distantly associated. The similarities, they found, are an instance of convergent evolution, the impartial evolution of comparable traits in numerous species. The event of flight in bugs, birds, mammals and now-extinct pterosaurs is a traditional instance of this phenomenon.
In line with Reyes, an array of distinctive options on Garzapelta’s plates clearly marked it as a brand new species. They vary from how the plates match collectively to distinctive bumps and ridges on the bones. Nonetheless, determining the place Garzapelta match into the bigger aetosaur household tree was extra of problem. Relying on which portion of the armor the researchers emphasised of their evaluation, Garzapelta would find yourself in very completely different locations. Armor that ran down its again resembled armor from one species, whereas its midsection spikes resembled armor from one other.
As soon as the researchers decided that the spikes developed independently, they have been capable of work out the place Garzapelta match finest amongst different aetosaur species. However, Reyes stated the analysis exhibits how convergent evolution can complicate issues.
“Convergence of the osteoderms throughout distantly associated aetosaurs has been famous earlier than, however the carapace of Garzapelta muelleri is one of the best instance of it and exhibits to what extent it will probably occur and the issues it causes in our phylogenetic analyses,” Reyes stated.
Garzapelta is a part of the Texas Tech College fossil collections. It spent many of the previous 30 years on a shelf earlier than Reyes encountered it throughout a go to. Invoice Parker, an aetosaur skilled and park paleontologist at Petrified Forest Nationwide Park who was not a part of the analysis, stated that college and museum collections are a important a part of making the sort of analysis doable.
“These specimens weren’t simply dug within the subject yesterday,” he stated. “They have been sitting within the museum for many years and it simply takes somebody like Will to return alongside and eventually determine to review them and make them come to life.”
Along with completely different species having completely different armor, it is doable that an animal’s age or intercourse might additionally have an effect on armor look. Reyes is presently exploring these questions by finding out aetosaur fossils within the Jackson Faculty’s assortment, most of which have been discovered through the Nineteen Forties as a part of excavations performed by the Works Progress Administration.
The analysis was funded by the Nationwide Science Basis and the Jackson Faculty.
The research co-authors are Jeffrey Martz, an affiliate professor on the College of Houston-Downtown, and Bryan Small, a analysis affiliate on the Museum of Texas Tech College.
