Dwarf Dinosaurs vs. Giant Pterosaurs

Transylvania, a place most people associate with vampires, creepy castles, and the Carpathians. But not us—we think of giant pterosaurs, the flying reptiles, and dwarfed sauropods, commonly called long-neck dinosaurs. My University of Southampton vertebrate paleontology research group and I recently joined local Romanian paleontologists from the Sebes Municipal Museum and the Transylvanian Museum Society for their weeklong fieldwork ranging the basins of Transylvania and Hatszeg in search of these prehistoric creatures.

The field trip, sponsored by the National Geographic Society, had two goals: to prospect and excavate for fossils and to give the group’s master’s and Ph.D. students (like me) the opportunity to get more fieldwork experience—which, a lot of paleontologists agree, is the best part of the job. Our group leader, senior lecturer Dr. Gareth Dyke, set up a collaboration with local Romanian paleontologists so we could gain knowledge and they could gain extra pairs of eyes. We were exceptionally lucky with the weather, especially considering that last year’s field trip saw snow.

SONY DSCThe Southampton vertebrate paleo-team with Radu Totoianu from the Sebes Municipal Museum and Matyas Vremir from the Transylvanian Museum Society. (Photo courtesy of Liz Martin)

The “Island Rule”: Dwarfism in Dinos

The rocks we were examining were from the late Cretaceous (late Campanian and Maastrichtian), right at the demise of the age of the dinosaurs, a turbulent time in the world’s history, with dramatic climate change and volcanic activity. In most parts of the world dinosaurs like Tyrannosaurus rex grew to massive sizes. But in what’s now Romania, something else was going on.

Transylvania at this time consisted of a shallow sea with many small islands. These were inhabited by small dinosaurs like the famous double-clawed raptor Balaur. Overhead flew giant pterosaurs (or perhaps they walked around). But what’s strange is that many of the dinosaurs found here were actually dwarves, at least compared to related species found elsewhere in the world.

The first person to notice and describe this tendency was the infamous Baron Nopcsa. Describing this phenomenon, later termed “the island rule,” he stated that animals get smaller on islands as resources and space is limited. The dwarf dinos are exemplified by the euornithopod Zalmoxes (close relative of Rhabdodon), which had a body length of about eight to ten feet, tiny for an ornithopod dinosaur. The pterosaurs, on the other hand, could fly and were hence an exception to the rule (though they were maybe not the largest—who knows?).

balur - the famous double clawed raptor - Photo Aubrey RobertsBalaur, the infamous double-clawed raptor. (Photo  courtesy of Aubrey Roberts)

DANGER: Risk of Trench Foot

The exposed layers (outcrops) of the fossil-bearing red sedimentary rocks were located in and along rivers, so we spent most of our time wading around in too deep water for our Wellington boots. The brave went in their sandals or hiking boots and got wet; the smart had brought along waders. I, on the other hand, had Norwegian woolly socks in my Wellies, which wasn’t such a bad choice after all, as wool keeps you warm even when wet. Luckily, I had a couple of extra pairs for people with cold feet. However, after a week in wet Wellies, “trench foot” was a real risk.

SONY DSCGareth Dyke risks getting wet feet to reach the outcrop, which is bright red. (Photo courtesy of Liz Martin)

“Getting Your Eye In”

We investigated several well-known field sites and some new ones. Being at the foot of the Carpathian Mountains, the Hatszeg basin was particularly spectacular. It took a couple of days to, as we paleontologists call it, get “your eye in” and find bone. Especially as the bone color could vary between localities from nearly black to red, green, or white. We scoured the riverbed and eroded sides of the river and found several partial and some complete bones.

sauropod caudalA sauropod vertebra fresh from the field and after preparation. (Photo courtesy of Matyas Vremir)

A Real “Littlefoot”: The Dwarf Sauropods

Sauropod fossils were definitely a theme on this trip, as we found several isolated bones. One of the previous master’s students, Rebecca Groom, was lucky enough to find a partial sauropod femur. The bone was definitely a lot smaller than the ones from most relatives that can be seen in museums. Even I found a tail vertebra! It’s hard to imagine that the sauropods, a group of dinosaurs that grew to be the largest land animals on Earth, had a miniature species. The species that have been described from Romania are of the genus Magyarosaurus, estimated to be nearly 20 feet long. These, in turn, could have been prey to the giant pterosaurs that have also been described from the region.

Rebecca Groom and her sauropodPrevious master student Rebecca Groom holds up her great find–the sauropod femur! (Photo courtesy of Aubrey Roberts)

Giant Pterosaurs

Compared to the stocky sauropods, pterosaurs had more gracile and hollow bones, and hence are not as easily preserved. The wing bones, in particular, are easily crushed and deformed and are rare finds. Liz Martin, my fellow Ph.D. student (and pterosaur specialist) and I did, however, find some fragments that could be from a pterosaur—we won’t know until they’re cleaned and prepared. This brought so much joy to Liz that her heart nearly exploded and we ran round singing Tom McFadden’s Fossil Rock Anthem for over an hour. Ah, the joys of being a paleontologist. The largest beastie so far reported from this region was Hatzegopteryx, with an estimated wingspan of about 33 feet! I wouldn’t like to mess with that creature.

Mark Witton and Darren Naish’s research and Witton’s illustrations first gave life to the image of giant pterosaurs like Quetzalcoatlus northropi nipping up small sauropods like this unfortunate juvenile titanosaur. (IIllustration by Mark Witton, Creative Commons in the PLOS ONE paper doi:10.1371/journal.pone.0002271.g009)

Crocodile (and Turtle) Dundee

Not only sauropods and pterosaurs are found in this region. Several turtle and crocodile species have been described. Unfortunately, we didn’t find anything more complete than a few fragments, but they could still be important, telling us something about the diversity of these reptile groups in the area, especially from new sites. Every little bit helps!

Cloudy with a risk of crocsCloudy with a chance of crocs! (Photo courtesy of Aubrey Roberts)

Personally, my only field experience had been in the cold reaches of Svalbard, so this was all new to me. Being able to wander round looking for fossils in shorts and actually get sunburnt while doing it was a completely new and fantastic experience. Exploring new regions and finding new exciting fossils—that is what paleontology is all about!



Aubrey Roberts is a graduate student in paleontology, working with National Geographic Emerging Explorer Jørn Hurum and grantee Gareth Dyke. She writes from the field and the lab with a new take on very, very old things. Her main field of work focuses on ancient marine reptiles from Svalbard (Norway).