Just Our Type: Smithsonian’s Dinosaur Skeleton Becomes the Scientific Standard for Prehistoric Predator

The Smithsonian’s National Museum of Natural History’s fossilized skeleton of the Jurassic dinosaur Allosaurus has officially been named the type specimen for the entire species. This distinction makes the specimen, which is displayed in the museum’s “David H. Koch Hall of Fossils— Deep Time,” the single physical example researchers will refer to when they describe new fossils of Allosaurus fragilis, one of the most iconic species of dinosaurs in the world.

The specimen’s new status was bestowed by members of the International Commission on Zoological Nomenclature (ICZN). According to paleontologist Matthew Carrano, the museum’s curator of dinosauria, the change was more than a decade in the making and represents a coveted scientific honor.

“In 2010, a petition was made to the ICZN to solve the problem that the very famous and scientifically important dinosaur A. fragilis was based on materials that couldn’t really be identified as anything more than a non-descript predatory dinosaur,” Carrano said. “This decision really emphasizes how important our specimen is—both historically and in the present—for dinosaur science.”

Stretching over 20 feet and sporting a mouthful of dagger-like teeth, Allosaurus terrorized other dinosaurs during the Late Jurassic Period some 150 million years ago. The prehistoric predator lived in western North America alongside other well-known species like the armored Stegosaurus and a number of supersized sauropod dinosaurs like Diplodocus.

The Dawn of American Paleontology

The name Allosaurus has been in the scientific lexicon for nearly 150 years. But it did not always belong to a well-known dinosaur. In 1877, Yale University paleontologist Othniel Charles Marsh was in the midst of a contentious scientific competition now known as the ‘Bone Wars’ with rival Edward Drinker Cope to discover and name new species of dinosaurs from the western United States. To keep pace with Cope, Marsh described a set of fragmentary fossils from the Jurassic-aged Morrison Formation in Colorado as a new species of predatory dinosaur. Because the animal’s vertebrae varied from other dinosaurs known at the time, Marsh came up with the name Allosaurus, which means ‘different lizard’ in Greek. He rounded out the creature’s scientific identity with the species name fragilis due to its delicate remains.

Marsh deposited this relatively meager specimen—which included a tooth, toe bone and a couple of vertebrae from the backbone—in the collection of the Peabody Museum of Natural History at Yale University (now the Yale Peabody Museum). Because Marsh used these fossils to formally describe A. fragilis, this sample became the species’ official type specimen.

Many prehistoric species enter the scientific record on the basis of scant remains. Complete specimens of dinosaurs are incredibly rare, so scientists are often forced to use fragmentary fossils. Even if paleontologists eventually find more complete specimens, the fossils that were initially described usually retain their type status on a scientific first-come, first-served basis.

But Allosaurus represents an intriguing case for a taxonomic do-over. Shortly after Marsh described the fragmentary type specimen, paleontologists unearthed more substantial Allosaurus fossils that provided a much fuller picture of the Jurassic carnivore. In 1884, one of Marsh’s collectors uncovered a nearly complete Allosaurus skeleton in a Colorado quarry. The specimen was shipped back to Marsh, but he was not able to conduct a detailed description of the fossil before he died in 1899.

Allosaurus Arrives at the Capital

After his death, a large portion of Marsh’s fossils were transferred to the Smithsonian’s United States National Museum (the precursor to the National Museum of Natural History). Museum paleontologist Charles Gilmore led the effort to unpack, prepare and catalog Marsh’s fossils and integrate them into the museum’s burgeoning National Fossil Collection. This trove of fossils included the nearly complete Allosaurus specimen from Colorado.

In 1920, Gilmore described this specimen, cataloged as USNM V 4734, in depth for the first time. The resulting paper cleared up the confusion that had surrounded the species for decades—Cope and Marsh had both mistakenly described other Allosaurus specimens as different, now-defunct dinosaur species. Gilmore’s work helped drive these erroneous scientific names into extinction and made the museum’s specimen an essential piece of the Allosaurus puzzle.

“Gilmore’s paper has remained an important reference for paleontologists and really established our specimen as a sort of ‘flagship’ individual for Allosaurus,” said Carrano, who is currently working on updating Gilmore’s century-old description of USNM V 4734. “As a result, our specimen has functioned as a sort of de facto type.”

Museum visitors are able to see the historic Allosaurus specimen displayed in the museum’s Deep Time fossil hall along with the type specimen of its fossil foe, Stegosaurus, and the sauropods Diplodocus and Camarasaurus. The exhibition’s Allosaurus mount, which contains the animal’s real fossilized bones, displays the dinosaur in a rarely seen position. Instead of chasing down prey, the Allosaurus’ skeleton is crouched down like a modern bird as it guards a clutch of fossilized eggs.

“USNM V 4734 has always been a prize of the Smithsonian’s dinosaur collection,” Carrano said. “Now it has a prominent position in the Deep Time hall, reflecting aspects of its biology that were unimagined in Marsh or Gilmore’s times.”

This summer, the museum is celebrating the fifth year anniversary of the “David H. Koch Hall of Fossils—Deep Time.” The world-class hall, which contains some 700 mounted fossil specimens including the Allosaurus type, explores the epic story of how Earth’s distant past is connected to the present and informs the future. As the anniversary approaches, the museum is also putting a remarkable, rainbow-hued ammonite fossil on display in the museum’s “Objects of Wonder” exhibition. The shimmering shell dates back 70 million years to the Late Cretaceous Period and is considered an organic gemstone thanks to its iridescent colors.

About the National Museum of Natural History

The National Museum of Natural History is connecting people everywhere with Earth’s unfolding story. It is one of the most visited natural history museums in the world. Opened in 1910, the museum is dedicated to maintaining and preserving the world’s most extensive collection of natural history specimens and human artifacts. The museum is open daily, except Dec. 25, from 10 a.m. to 5:30 p.m. Admission is free. For more information, visit the museum on its website, blog, Facebook, X (formerly Twitter) and Instagram.

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