Paleontologists still know comparatively little about fin-backed Spinosaurid dinosaurs. But while the newest addition to the family is impressive, Spinosaurus mirabilis isn’t making it easier for researchers. In a study published today in the journal Science, researchers at the University of Chicago describe S. mirabilis, a species that stalked present-day central Africa around 95 million years ago. At first glance, the dinosaur is instantly iconic. Its head crest is shaped like a curved sword called a scimitar, and measures 20 inches long. However, the dinosaur’s overall anatomy and Cretaceous stomping grounds showcase Spinosaurid’s unexpected and fascinating evolutionary culmination.
“This find was so sudden and amazing, it was really emotional for our team,” said study co-author Paul Serano.
S. mirabilis stands apart from its relatives due to where paleontologists discovered their specimen. Serano’s team uncovered the first fossil evidence in 2019 while excavating a remote region of the central Saharan desert in Niger. Previous Spinosaurid specimens have all been found in ancient coastal deposits near prehistoric shorelines, but the first S. mirabilis bones were located far inland—somewhere between 310 to 610 miles from the nearest marine habitats. Given the nearby presence of long-necked dinosaurs in river sediments, paleontologists now believe this Spinosaurus lived in a forested region crisscrossed by waterways. According to Serano, it would have been a fearsome sight no matter where it lived.
“I envision this dinosaur as a kind of ‘hell heron’ that had no problem wading on its sturdy legs into two meters of water, but probably spent most of its time stalking shallower traps for the many large fish of the day,” he said.
Based on the crest fossil’s inner vascular canals and exterior texture, the team theorizes that the cranial accessory was likely housed in keratin and brightly colored. They also contend S. mirabilis finally puts to rest the theory that Spinosaurus primarily lived and hunted in marine environments. Aside from the location of its discovery, S. mirabilis is the first dinosaur known to possess an interdigitating piscivorous (or “fish trap”) mouth. This anatomy features a lower jaw with teeth that protrude out between the upper set—a trait previously only seen in flying pterosaurs, marine ichthyosaurs, and semiaquatic crocodilian predators. This also makes S. mirabilis the only Spinosaurid with the distinct dental arrangement.
For as much as S. mirabilis contextualizes its wider dinosaur family, it raises many more questions about its life, habitat, and role in the Cretaceous era.
“I’ll forever cherish the moment in camp when we crowded around a laptop to look at the new species for the first time,” said Serano. “That’s when the significance of the discovery really registered.”
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