Scientists have estimated the size of an extinct flying reptile, a pterosaur, based on fragments of a fossil finger bone discovered in southern England in June 2022. The results make it the largest British pterosaur yet described, and the second-largest Jurassic pterosaur in the world.
This 149-million-year-old fossil, known as EC K2576 and dubbed “Abfab” by the researchers, was found in Abingdon, Oxfordshire – and it’s fantastic. Since then, they’ve been trying to figure out what kind of pterosaur it was – its taxonomy – and how big the animal was.
During the Mesozoic Era, the “Age of Reptiles” that lasted from 252 to 66 million years ago and includes the Jurassic Period, dinosaurs, pterosaurs and other giant reptiles roamed the Earth – many of which dwarfed the largest land animals alive today.
The scientists estimated the body size of this particular species, which has no modern descendants, by collecting data from similar fossil bones in more complete fossil pterosaur skeletons, for which the size of each animal has been reliably estimated.
They then extrapolated to estimate the wingspan of EC K2576 based on its finger bone. The same team of scientists also applied this technique to predict the body size of other pterosaurs, including extrapolating based on pterosaur footprints alone.
What were pterosaurs?
There are over 110 described species of pterosaurs. They can be grouped and separated based on their anatomy—the shape of their bones—which is related to ecology: where they lived, what they ate, and how they behaved. They can also be grouped and separated based on their phylogeny (evolutionary history) and biomechanics (physics of their bodies).
It is not possible to identify EC K2576 to the species level from such limited material. However, by comparing the partial bone to the same skeletal element from other, more complete pterosaur skeletons, the team was able to identify the bone as belonging to a large pterosaur from the group known as the Ctenochasmatoidea. These were similar to pterodactyls, the best-known of all pterosaur groups.
Ctenochasmatoids were mainly aquatic or semi-aquatic pterosaurs. They had long bodies with short wing proportions, like wading birds, and large webbed hind feet. They were probably not as graceful in flight as other pterosaurs, and they had a long bony crest on their heads.
All pterosaurs were carnivorous, but within the Ctenochasmatoidea, some specialized in eating mollusks (the group of animals that includes snails and mussels), others were filter feeders, and still others were sweep feeders (sweeping the water with their jaws to catch food). This strategy is also used by modern birds such as spoonbills.
Of the pterosaur species that EC K2576 most closely resembles, Pterodaustro-guinazui was a filter feeder and Ctenochasma elegans was probably a sweep-feeder. It is thus possible to infer ecology and behavior from partial skeletal material.
Based on a partial finger bone, the scientists estimate that EC K2576’s wingspan was between 3.2 and 3.65 meters. This is roughly equivalent to the 3.5-meter wingspan of the snowy albatross, the largest living flying bird species, which has a wingspan about twice that of two average-sized humans.
The largest Jurassic pterosaur based on footprints alone may have been even larger, with a wingspan of up to four meters. The largest known Jurassic pterosaur based on fossils is a specimen belonging to the group Pterodactyloidea, found in Switzerland, which had a wingspan of about five meters.
The paper confirms growing evidence that there were more large pterosaur species in the Jurassic than historically would have been the case.
Pterosaurs have previously been highlighted as an example of Cope’s Rule: that lineages tend to increase in body size over the course of evolution. While the new science behind EC K2576 suggests that Jurassic pterosaurs were larger than we thought, the largest pterosaurs appeared at the end of the Cretaceous, the last period of the Mesozoic Era.
These giants of the Cretaceous period lived between about 77 and 66 million years ago, just before the asteroid that wiped out all pterosaurs and non-avian dinosaurs. The pterosaurs Hatchetty Opteryx And Quetzalcoatlus were the largest living creatures ever to fly, with a wingspan of over ten meters (about six times the length of an average human).
The scientists in the latest study also reevaluated size estimates of known pterosaurs. This included shrinking one of the most complete Jurassic pterosaurs yet discovered, Dear sgiathanch from the Isle of Skye in Scotland. DarlingIts wingspan has been revised from about 2.5 m to 2.04 m. It remains a large animal, comparable to a British eagle or swan today.
EC K2576 joins the growing community of British Jurassic pterosaurs Darling and the recently described, more modestly sized (1.6 m wingspan) Ceopteraalso from Skye.
Why fossils are important
I am an ecologist with a strong interest in anatomy and biomechanics. Bones allow us to infer behavior through functional anatomy – the shape, size, and structure of bones reflect their function. And bones can also inform us about the life history of the individual – for example, through growth and signs of injury and disease.
I’ve written about inferring parental care in pterosaurs based on skeletal growth. Sometimes we get a fossil skeleton that records a particular behavior—like fighting, predation, sex, or care of young.
This study is interesting because knowledge and insight in anatomy and biomechanics are applied to reconstruct elements of morphology (body shape and form) and the life history of an extinct species.
Extrapolation from isolated bones and fragments can be applied more broadly – to reconstruct the sizes of other extinct animal groups, such as dinosaurs and aquatic reptiles including ichthyosaurs, mosasaurs and plesiosaurs. By reimagining extinct ecosystems, we can better understand how the world and its ecological communities functioned in the past and differed from the present.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Jason Gilchrist is not an employee of, an advisor to, an owner of stock in, or a recipient of funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond his academic appointment.