Very little was known about the evolution of pterosaurs – such as how they evolved to fly – but now researchers are saying that they have identified the “missing link” in their family tree. A small reptile called lagerpetid may be the closest-known relative to pterosaurs found to date. There is, however, a significant difference between the two species which is that lagerpetids didn’t fly.
Since the 1700s, many fossils belonging to pterosaurs have been unearthed – they dated back to between 220 million and 65 million years ago. Pterosaurs were archosaurs – a name that translated from the ancient Greek word meaning “ruling lizard”. Archosaurs were a group that included dinosaurs, crocodylians, and birds as well as pterosaurs. They first showed up around 250 million years ago in the late part of the Permian period.
And now that the lagerpetid fossils have been analyzed, experts finally have a clue as to how pterosaurs became the first vertebrate to evolve into flying creatures. Interestingly, lagerpetid fossils have been found since the 1970s but at that time, researchers thought that it was more like a dinosaur than a pterosaur. As a matter of fact, the only real thing they knew about the creature was that it lived between 237 million and 210 million years ago.
But as the years passed, more complete fossils of the lagerpetid have been unearthed around the world. One example was the “tiny bug slayer” from Madagascar that dated back approximately 237 million years ago. At that point, they concluded that this species was closer related to pterosaurs than dinosaurs.
The researchers used computed tomography (micro-CT) to scan the braincase of a lagerpetid and they found that the shape of the brain as well as its inner ears were quite similar to those of a pterosaur. In an interview with Live Science, Sterling Nesbitt, who is an associate professor of geosciences at Virginia Tech and a co-researcher of the study, explained this further, “It has to do with the semicircular canals [in the ear], which orients you in 3D space.” “The shape of those canals correlates with ecology and how you move your head — basically, are you agile or not? And a lot of things that have flight have semicircular canals with a really large and characteristic [shape] because you’re flying, you’re in a lot more 3D space.”
While lagerpetids are not a direct ancestor of pterosaurs, they do have a common ancestor at the “base” of their family tree, so it does provide some interesting answers about the evolutionary history. David Unwin, who is a reader in paleobiology at the University of Leicester in England who studies pterosaurs but was not a part of the study, noted that the research “provides some impressive evidence” however “some difficult questions remain”.
He went on to say, “Lagerpetids, argued in this analysis to be the closest known relatives to pterosaurs, were small, lightly-built, fully bipedal [two-legged] animals with relatively short forelimbs.” “Pterosaurs, by contrast, were fully quadrupedal [four-legged] and had highly elongate[d] forelimbs.” He added that since there was such a big difference in their bodies, “these discoveries throw little light on when, where and how pterosaurs and their flight ability first evolved.” (Pictures of what the lagerpetid would have looked like can be seen here.)
The study was published in the journal Nature where it can be read in full.