A mysterious “runner” dinosaur, solely in regards to the measurement of a canine, scurried across the historic floodplains of what’s now Colorado round 150 million years in the past, a brand new examine finds.
The 2-legged herbivore, named Enigmacursor mollyborthwickae, was round 3 toes (1 meter) lengthy and 1.5 toes (0.5 m) tall. Nonetheless, regardless of its small stature, the invention of this dinosaur is having a huge impact on scientists’ understanding of a number of Jurassic species.
A personal fossil firm excavated E. mollyborthwickae in Colorado between 2021 and 2022. The skeleton was later put up on the market, marketed as Nanosaurus, which is one other sort of small dinosaur from the identical rock formation — referred to as the Morrison Formation. After the Pure Historical past Museum in London purchased the skeleton, researchers discovered that not solely is that this new specimen not Nanosaurus, however the scientific classification of Nanosaurus and several other different dinosaurs from the Morrison Formation are additionally unreliable.
The Morrison Formation is dwelling to many iconic dinosaur fossils, such because the plated Stegosaurus and the ferocious predator Allosaurus, which might have lived alongside E. mollyborthwickae throughout the Jurassic interval (201.3 million to 145 million years in the past). The brand new examine, printed Wednesday (June 25) within the journal Royal Society Open Science, highlights that researchers nonetheless have lots to be taught in regards to the formation’s smaller dinosaurs.
“Whereas the Morrison Formation has been well-known for a very long time, a lot of the focus has been on looking for the most important and most spectacular dinosaurs,” examine co-lead writer Susannah Maidment, a senior researcher on the Pure Historical past Museum, mentioned in an article printed by the museum. “Smaller dinosaurs are sometimes left behind, which means there are most likely many nonetheless within the floor.”
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The skeleton was excavated by an organization referred to as Dinosaurs of America, LLC and bought by the David Aaron artwork gallery in London, earlier than the Pure Historical past Museum bought the fossils in 2024, based on the examine. When the researchers obtained their arms on the alleged Nanosaurus, they started to look carefully on the group, together with different small-bodied Morrison Formation dinosaurs.
“Nanosaurus wasn’t named based mostly on many fossilised bones, however largely the preserved impressions of bones pressed into hardened sand which might be very troublesome to review,” examine co-lead writer Paul Barrett, a paleobiologist on the Pure Historical past Museum, mentioned within the museum’s article. “So, we turned to the opposite bones which were referred to the group over the previous century, however these weren’t notably well-preserved both.”
The fossil file for a number of small-bodied Morrison Formation dinosaurs is poor and incomplete, and it has undergone a number of scientific revisions, based on the examine. Barrett and Maidment reviewed Nanosaurus and comparable Morrison Formation species in a examine printed April 25 within the journal Bulletin of the Peabody Museum of Pure Historical past, concluding that by trendy requirements, none of them had distinct sufficient options or a novel mixture of traits to be legitimate.
For the brand new examine, the researchers pored over the so-called Nanosaurus specimen and scanned it so they might create digital 3D photos of its fossilized bones. They decided {that a} distinctive mixture of options, notably in its legs, made the animal distinct sufficient from different dinosaurs. Their evaluation discovered that its closest identified relative was Yandusaurus hongheensis, a Jurassic herbivore from China.
Barrett and Maidment created a brand new genus (group) for the specimen. The genus identify, Enigmacursor, combines the phrases “enigma” — a reference to the mysteries surrounding its scientific classification — and “cursor,” which implies “runner” in Latin. The dinosaur’s species identify, “mollyborthwickae,” honors museum donor Molly Borthwick, whose donation allowed the Pure Historical past Museum to buy the specimen, based on the examine. The museum did not disclose the price of the specimen.
“By learning its anatomy intimately, we have been in a position to make clear this species’ evolutionary relationships, its taxonomy and the variety of a beforehand poorly understood group of small dinosaurs,” Maidment mentioned in a assertion.
