10 Swift Facts About Eoraptor
By Mark Mancini
Kentaro Ohno, Wikimedia Commons // CC BY 2.0
One of the earliest known dinosaurs, this meek little fellow poses far more questions than it answers.
1. It’s Got an Evocative Name.
Eoraptor means “dawn plunderer,” a reference to its status as an animal that lived at or near the very “dawn” of the dinosaurs. Its full scientific name is Eoraptor lunensis. Roughly translated, that second word means “of the moon.” This is an homage to the Argentinian park in which Eoraptor's remains were first found. A sprawling, otherworldly place, the area is popularly called Valle de la Luna or Valley of the Moon.
2. Eoraptor Was Discovered on a Joint American-Argentinian Expedition.
On October 3, 1991, Eoraptor lunensis came to light. The big moment was made possible by American paleontologist Paul Sereno and Alfretto Monetta of the National University of San Juan. Together, they led an international team through the Andes foothills—and promptly went five weeks without finding anything significant. Happily, when all hope seemed lost, Argentinian student Ricardo Martinez saved the day. Fortune was with him when he spotted a conspicuous tooth, which just so happened to come with a skull and a reasonably-complete skeleton.
3. Eoraptor Was Most Likely an Omnivore.
Rooted in its mouth was a combination of blade-like and leaf-shaped teeth. Two hundred and thirty million years ago, the arrangement would have allowed Eoraptor to eat everything from green foliage to small, passing critters.
4. Although Eoraptor had Five Fingers on Each Hand, Two Were Probably Useless.
Three clawed, grasping digits are present at the end of each arm. While these no doubt helped Eoraptor gather food, the same can’t be said about its other fingers, which were stubby and clawless.
5. Some Scientists Think That We’ve Only Found Juvenile Eoraptor Specimens So Far.
Wikimedia Commons // CC BY-SA 3.0
Eoraptor eye sockets look almost disproportionately big. This is a trait we often associate with young, still-growing animals—including humans. Furthermore, a few specimens contain skull bones which aren’t fully fused together. Hence, a few experts conclude that all (or most) of the Eoraptor material we’ve yet uncovered came from immature animals.
6. A Few Other Primitive Dinos Shared its Habitat.
Herrerasaurus, Eoraptor’s neighbor/potential predator, was around 12 feet long and had a rather rectangular skull. Their turf (in modern-day South America) was also home to the nimble “dawn runner” Eodromaeus, which chased down small game on its lanky hind limbs. More about that guy later…
7. For its Time, Eoraptor Had an Unusual Neck.
In Eoraptor’s day, non-dinosaurian reptiles ran the show. Huge, quadrupedal predators called rauisuchians stalked the landscape. Crocodile-like phytosaurs basked on riverbanks. And the beaked, armor-plated aetosaurs spent their days digging up roots. Amidst such company, earth’s first dinos looked rather diminutive. Still, a few anatomical features helped them stand out anyway. For instance, as paleontologist Donald Henderson notes, basal dinosaurs “all had necks that were noticeably longer than those of [related reptiles] from the same period.”
8. Scientists Have Long Debated Eoraptor’s Placement on the Dino Family Tree ...
Since its discovery in the early '90s, paleontologists have been arguing about its evolutionary relationships. Some say that Eoraptor should be thought of as a very early theropod, or “meat-eating dinosaur” (think T. rex or Velociraptor). Others, meanwhile, lump it with the sauropodomorpha, a gang that includes long-necked giants like Jurassic Park’s Brachiosaurus. Together, both groups form an order of dinosaurs called the saurischia. So, perhaps Eoraptor is just a really early saurischian, one that emerged before the theropods and sauropodomorphs split apart.
9. … But, Hopefully, a New-ish Carnivore Will Help Clear Everything Up.
Cross your fingers, everybody! When Eodromaeus was discovered in 2011, the little beast convinced many dino classification buffs that Eoraptor rightly and truly belonged to the sauropdomorph crew. As you’ll recall, these two lived at the same place and at the same time. But while Eoraptor’s family ties are frustratingly ambiguous, no one can doubt sharp-toothed Eodromaeus’ credentials as a card-carrying theropod.
“Eodromaeus gives us the earliest picture of this predatory line,” says Sereno. Previously, he—like many—believed Eoraptor deserved that distinction. Eodromaeus changed his mind. “Eoraptor was incorrectly placed at the base of the theropod tree,” Sereno now claims. Today, the scientist holds that it was a sauropodomorph all along. After all, among other things, it did have those plant-slicing chompers (unlike Eodromaeus).
10. The Man Who Named Eoraptor Has an Impressive Fossil-Hunting Resume.
None other than Sereno himself coined the name back in 1993. Since then, he’s spearheaded numerous expeditions throughout Asia and Africa—one of his teams has even extracted 100 tons of dinosaur fossils from the Sahara desert. Brand-new species he’s had a hand in discovering include the wrinkle-faced carnivore Rugops primus, and the sizable sauropod Jobaria tiguidensis. On a random note, he was also named one of People magazine’s “50 Most Beautiful People” in 1997.