Giant pterosaurs may hog the spotlight, but here’s why the little guys deserve some love.
Long before birds took to the air, pterosaurs ruled the skies. This enterprising group of reptiles emerged in the Triassic period and exploded into a spectacular diversity of forms over the next 160 million years, until they were wiped out alongside the dinosaurs at the end of the Cretaceous by a massive asteroid strike.
To facilitate flight, pterosaur bones were lightweight and fragile, like a bird's. But those important qualities also mean that decent fossils from these extraordinary animals are extremely rare, especially among species with smaller, more delicate frames.
Every now and then, however, the fossil record literally throws paleontologists a bone. A team led by Elizabeth Martin-Silverstone, a palaeobiology PhD student based at the University of Southampton, presents just such a lucky find with new research published Tuesday in the journal Royal Society Open Science.
The study describes the partial skeleton of a pterosaur with a relatively diminutive wingspan of 1.5 meters (five feet) unearthed on Hornby Island in British Columbia.
"It likely does represent a new species, but we have chosen not to name it due to the fragmentary nature of the specimen," Martin-Silverstone told me. "However, the size and morphology does suggest it is a new animal."
The unnamed flyer lived about 77 million years ago, during the Late Cretaceous period. It belonged to a family of pterosaurs called the azhdarchoids, which produced the largest airborne creatures known, including the surreal Quetzalcoatlus northropi with its staggering 40-foot wingspan. Many azhdarchoids appear to have evolved disproportionately large heads, as illustrated by this delightful scale comparison of the new species with a house cat.
"There really hasn't been any work done on exactly why these animals would have had such big heads, just that we know from complete specimens that they did," Martin-Silverstone told me. "We also know how they got so big—their heads were full of sinuses and air, keeping them light. But as for why, that is currently unknown and would just be speculation at this point."
Though only the humerus, dorsal vertebrae, and some other stray skeletal parts from this small pterosaur have survived, close examination revealed that this animal was almost fully mature when it died, and was not a juvenile of a larger species like Quetzalcoatlus.
Adult pterosaurs with wingspans under two meters are scarce in Cretaceous formations, particularly in coastal British Columbia. Finding one suggests that small pterosaurs may have been as common as their more easily preserved (and much bigger) relatives, although they're trickier to find.
This is essential information for researchers interested in reconstructing the rich ecological puzzle of this period. Though pterosaurs pioneered powered flight long before birds first spread their wings, the two clades were fighting over many of the same niches during the Cretaceous, so it's important to know as much as possible about the sizes and shapes represented in each lineage.
"Other areas where pterosaurs are found at this time, like the Dinosaur Park Formation of Alberta, have a documented bias against small animals," Martin-Silverstone explained. "Since pterosaurs are already poorly preserved due to their hollow bones, this suggests that small pterosaurs would be even less likely [to be] preserved. In this case, I think we're just lucky."
This has been a big week for for pterosaur admirers. A separate team led by paleontologist Laura Codorniú of the National Scientific and Technical Research Council in Buenos Aires described another new species, named Allkaruen koi, in research published in PeerJ.
Though this animal hails from the Jurassic period and was found in Patagonia, Argentina, it is similar to the Hornby Island pterosaur in size, with a wingspan of only a few meters.
These exciting discoveries help to round out our understanding of the mind-boggling diversity of pterosaurs, both large and small, that shared Mesozoic Earth with the dinosaurs, along with early birds and mammals. They haven't flown in our skies for millions of years, but fortunately, that doesn't mean the fantastic legacy of these creatures has been erased.