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The team named the dinosaur Bajadasaurus pronuspinax—an etymological chimera of Spanish, Greek, and Latin that means “lizard from Bajada with forward-bending spines.” It lived in the very dawn of the Cretaceous period, around 140 million years ago. And Gallina thinks that it likely used its outrageous spines to defend itself from predators.
Bajadasaurus is one of the sauropods—a group of large-bodied, long-necked dinosaurs that include such celebrity species as Brontosaurus, Diplodocus, and Brachiosaurus. More specifically, it’s one of the dicraeosaurs—a family of little-known sauropods distinguished by their neck spines.
The first of these, Dicraeosaurus, was discovered in Tanzania in 1914. Its spines were relatively short, but prominent enough to give the creature its name, which means “two-forked lizard.” For almost eight decades, it was the only known member of its group. Argentine scientists finally described a second species, Amargasaurus, in 1991. And more recently, for whatever reason, dicraeosaurs have been popping up all over the place. Three more were described in the 2000s. Lingwulong, from China, was revealed last July. Pilmatueia, also from Argentina, was announced to the world just last month. That’s seven species, and Bajadasaurus makes eight.
There are almost as many hypotheses about what dicraeosaur neck spines were for as there are dicraeosaur species. Some scientists suggested that they supported a camel-like hump, or that they held aloft a pair of sails, which served to regulate body temperature or signal to mates and rivals. Other researchers reckoned that the spines might have clattered together to make sounds, or supported air sacs connected to the dinosaur’s lungs.
Gallina isn’t discounting any of these ideas, but he argues that “the most logical explanation” is that each spine was its own separate horn, and together, they were used in defense. As dicraeosaurs bent down to graze, their spines would have flared out to provide cover for the vulnerable necks. The forward-pointing spines of Bajadasaurus might have been especially intimidating: They “would represent a disturbing fence for a loitering carnivore,” the team writes in a paper on the discovery.
Admittedly, that’s a lot to infer from just a single set of spines, on a single vertebra. Without the rest of the skeleton, the team can’t say for certain whether such spines really adorned the rest of Bajadasaurus’s neck. They’re basing their reasonable reconstruction on the closely related Amargasaurus—an animal that’s known from a full skeleton, and whose neck spines were just as long and dramatic as Bajadasaurus’s. They differ only in their direction, sloping backwards instead of forward.
Given the similarity between the two animals, Gallina thinks it’s unlikely that Bajadasaurus had only one set of spines, which just happened to be on the one neck bone the team found. It’s also unlikely that the other spines bent in different directions, because that would have stopped the beast from raising or dipping its neck. And it’s equally improbable that the spines Gallina found had become distorted in the fossilization process, because none of Bajadasaurus’s other bones were warped. “We think we’ve done an accurate restoration,” Gallina says.