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About 83 million years separated Late Jurassic icons—such as this Torvosaurus—from Cretaceous celebrities like Tyrannosaurus. Photo by the author.

You can’t understand dinosaurs without a sense of time. We need to know when a dinosaur lived to comprehend how it fits into what paleontologist William Diller Matthew called “life’s splendid drama.” But we throw around Deep Time estimates, framed in millions of years, so often that it’s easy to become inured to the wider context of life’s history.

The Mesozoic Era, which lasted from about 250 million to 66 million years ago, is often called the Age of Dinosaurs. As a kid, this brought to mind one endless summer when dinosaurs flourished. And many of the books I read picked one environment from three different periods within the era to represent dinosaur life. Little Coelophysis was the canonical Triassic dinosaur; the huge sauropods and theropods of the Morrison Formation represented the Jurassic, and a Cretaceous Tyrannosaurus versus Triceratops face-off ultimately capped off the succession. With the periods juxtaposed this way, millions of years didn’t seem so very long.

But let’s unpack some of that scenery. Diplodocus, Apatosaurus, Allosaurus, Stegosaurus and their neighbors roamed western North America about 150 million years ago. This slice of time falls in the latter portion of the Jurassic. The traditional representatives of the latest Cretaceous scene—Tyrannosaurus and Triceratops—did not evolve until about 67 million years ago. By themselves, these dates are just labels, but think of them falling along evolution’s timeline. About 83 million years separated Apatosaurus from Tyrannosaurus and Allosaurus from Triceratops. The so-called Age of Mammals—which began when the non-avian dinosaurs were wiped out—has been going on for about 66 million years. Less time separates us from Tyrannosaurus rex than separated T. rex from Stegosaurus.

Consider how much life has changed in the past 66 million years. Archaic mammals flourished and ultimately went extinct long before anything like the world’s modern fauna appeared. Saber-fanged, knobbly-headed herbivores such as Uintatherium, lemur-like primates called adapiforms, razor-jawed carnivores known as creodonts and many other strange forms proliferated and disappeared. Even lineages familiar to us today, such as horses, rhinos and elephants, evolved and diversified and are now represented by just remnants of what once existed.

The time between the last Triceratops and now has seen radical evolutionary changes. Now think of the 83 million years between the Jurassic and Cretaceous titans. During that time, the first flowering plants bloomed; the fish-like ichthyosaurs disappeared as plesiosaurs and mosasaurs became the predominant predators of the seas; vast herds of hadrosaurs and ceratopsids occupied places once dominated by sauropods; tiny tyrant dinosaurs transformed into apex predators, and early birds established themselves in ever-greater variety alongside their dinosaurian kin. These are just a few highlights, and that is part of the wonder and frustration of tracking the history of life on earth. We are offered only glimpses of an ever-changing picture, and when viewed separately, it’s easy to forget how those snippets relate to each other. But when we can step back, and consider how all those snippets run together, the long and ever-changing history of life on our planet seems all the more fantastic.

Baby Maiasaura and a parent at a mount in the Wyoming Dinosaur Center. Baby Maiasaura bones and egg fragments were the first dinosaur fossils in space. Photo by the author.

Last year, David Willetts hit a sour note when he unveiled his vision of improving science education in Great Britain. “The two best ways of getting young people into science” the Minister of State for Universities and Science said, “are space and dinosaurs. So that’s what I intend to focus on.”

Researchers, writers and science fans quickly jumped on the comment. And rightly so. Space and dinosaurs are popular, but they don’t appeal to everyone. Not every child dreams of becoming an astronomer or paleontologist. But my favorite response to the British official’s comments was the genesis of #spacedino on Twitter. If only spacedino were real, critics joked, we would have a perfect outreach tool. Who wouldn’t love dinosaurs in space? What I didn’t know at the time was that dinosaurs had already been beyond our planet.

The first dinosaur to venture into space was a species that greatly influenced our understanding of dinosaur lives, the hadrosaur Maiasaura peeblesorum. This 76-million-year-old “good mother lizard” cared for its young in large nesting colonies, and small bits of bone and eggshell found at a nesting site were carried by astronaut Loren Acton during his brief mission to SpaceLab 2 in 1985. This was a glamorous time for the dinosaur; Maiasaura was made Montana’s state dinosaur the same year.

Dinosaurs didn’t return to space until 1998. In January of that year, the shuttle Endeavor borrowed the skull of the small Triassic theropod Coelophysis from the Carnegie Museum of Natural History for its mission to the Mir space station. Like the remains of Maiasaura before it, the fossil skull was returned to earth after the mission was over.

I guess I was wrong about spacedino. The simple combination of space and dinosaurs isn’t very exciting at all. Dinosaurs on spacecraft amounts to nothing more than trivia. It was not as if the dinosaurs were going to be included in some kind of time capsule—like the Golden Record on the Voyager spacecraft—to teach whoever might eventually discover it about past life on our planet. Real space dinosaurs just can’t compete with their science fiction counterparts.

The head of Coelophysis - a close relative of Camposaurus - as restored by John Conway. Image from Wikipedia.

If you haven’t heard of Camposaurus, you’re not alone. This is one obscure dinosaur (and not to be confused with the better-known and very different Camptosaurus). First described in 1998, this animal may hold a critical place in the evolutionary tree of theropod dinosaurs, although, then again, it might not.

Very little is known about Camposaurus. The only parts that have been found and definitively referred to this dinosaur, recovered from the Late Triassic rock of Arizona, are a few parts of the dinosaur’s lower limb bones. (The original description mentioned bones from other individuals, but it is unclear whether these really belong to Camposaurus.) Still, the anatomy of these parts identified the dinosaur as a neotheropod dinosaur, and its geologic context made it potentially the oldest known representative of the huge, diverse group of dinosaurs which contained genera such as Ceratosaurus, Allosaurus, Tyrannosaurus, Spinosaurus and many, many more. The Camposaurus fossils, as a consequence, could be important for calibrating the early evolutionary history of theropod dinosaurs.

Naturally, the fact that so little is known about Camposaurus has made it a controversial dinosaur. Paleontologists have been trying to figure out where it fits in the theropod family tree—and whether the dinosaur even deserves a distinct name—for over a decade. The known bones are so hard to properly diagnose that they seem more likely to confuse than enlighten. Now paleontologists Martin Ezcurra and Stephen Brusatte have published a reexamination of the paltry Camposaurus bones, and they affirm that the dinosaur will remain important to questions about the early days of theropod dinosaurs.

According to Ezcurra and Brusatte, there are two subtle features which set Camposaurus apart from other early theropods, such as the well-known Coelophysis. The first is a distinctive ridge on one of the lower leg bones—the tibia—where it articulates with the fibula, and the second is the absence of a knob of bone on part of the ankle. Such subtle differences can make all the difference between whether a dinosaur genus or species is kept as distinct, ends up being lumped into another taxon, or remains a problematic mystery.

Ezcurra and Brusatte also attempted to figure out where Camposaurus fit among other theropod dinosaurs. As had been previously suspected, the dinosaur turned out to be most closely related to Coelophysis—so close, in fact, that Camposaurus might turn out to be a species of Coelophysis itself. Additional fossils will be needed to be sure, and, at Chinleana, paleontologist Bill Parker brings up an important point about the significance of the specimen in terms of its age.

Camposaurus has been thought to be the oldest known neotheropod dinosaur based upon the geologic details of the place it was found, known as the Placerias quarry. This site was thought to correspond to a certain part of Triassic rock called the Mesa Redondo Member of the Chinle Formation, but Parker reports that he has found this to be in error. The quarry is actually in slightly younger rock than has been proposed, meaning that Camposaurus is not as old as had been assumed. It’s still a very old theropod, but how old it really is and its relationship to other theropods remains tentative.

The takeaway from all these paleontological jots and tittles is that our knowledge of early dinosaurs is still in a state of flux. Determining the identities, relationships and ages of Triassic dinosaurs is an ongoing task, and our understanding will continue to change as new fossils are found. At the moment, the Camposaurus fossils play an important role in providing some of the only context we have for the early evolution of the neotheropod dinosaurs, and hopefully paleontologists will soon find the fossil clues that will allow us to understand how this great lineage got its start.

References:

EZCURRA, M., & BRUSATTE, S. (2011). Taxonomic and phylogenetic reassessment of the early neotheropod dinosaur Camposaurus arizonensis from the Late Triassic of North America Palaeontology, 54 (4), 763-772 DOI: 10.1111/j.1475-4983.2011.01069.x