Allkaruen means ‘ancient brain’ and Koi is ‘lake’ in Tehuelche. The name was chosen by the researchers for this new species of pterosaur – that is to say, flying reptile – and refers to two facts linked to its discovery. The first one is related to the state of preservation, which allowed scientists to study in detail the anatomy of the pterosaurs’ brain and its evolution. And the second fact is that this species was found in an environment of ancient Patagonian lakes.
Diego Pol, CONICET principal researcher at the Egidio Feruglio Paleontology Museum (MEF in Spanish) of Chubut, is one of the authors of the study published in PeerJ. The scientist explains that these flying reptiles are the ancestors of pterodactyls and share with them some characteristics. “
“They had the fourth finger, which would be like the ring finger. It was long because it contained the membrane of the wings, in some way similar to the ones that bats have. Allkaruen koi was relatively small: the wingspan was 50 feet, that is to say, it had the size of a bird like a seagull.
This species’ snout was very thin and long, with sharp teeth and was probably pscivorous, as the models that were found were near lacustrine systems or coastal areas.
Image of a brain with memories
Most of the remains of the pterosaurs are preserved in slab, that is to say in two dimensions because they were squashed by the sediments that accumulated on them. This find had a surprise: an excellent state of fossils’ conservation in three dimensions, what allowed scientists to analyze the skull with different technologies.
“One was the computerized tomography, so we could reconstruct how the anatomy of the brain was and compare how the different regions of the brain were and how developed they were”, Pol comments.
This allows researchers to fill the gap in the pterosaurs’ evolution chain. So far there were not old and well preserved models available to understand their brain evolution or their relationship with the huge pterodactyl.
“The conservation of the neurocranium, or braincase, enabled scientists to reconstruct the complete anatomy of the brain and inner ear in 3D, which is known today in other two species: Anhanguera of the Cretaceous of Brasil and Rhamphorhynchus of the Triassic of Germany. Allkaruen represents an intermediate phase between these two species”, Ariana Paulina Carabajal states. She is a CONICET associate researcher at the Research Institute for Biodiversity and Environment (INIBIOMA, CONICET-UNCOMA in Spanish).
The neurocranium is a complex structure formed by several bones whose main function is to lock and protect the brain and sense organs. The great preservation state of these fossils allowed experts to create a digital mould that was analyzed through microtomographies. This technique virtually cuts the brain to observe the internal structures without destroying the material and nowadays is one of the most used tools in paloneurology.
“In the evolution of pterosaurs, scientists could reconstruct the brain of a very primitive species and another of a highly evolved species, almost one of the last of its kind. When they were compared, the researchers noticed that in the evolution of pterosaurs there was a big modification in all the brain anatomy. The great preservation state of Allkaruen koi allowed scientists to provide information about an intermediate phase in the evolution of pterosaurs’ brains, which adapted to fly and eat”, Pol affirms.
These species’ flight was the most complex type of locomotion that appeared during the evolution. There are only three cases in which the vertebrates evolved and were able to fly: the birds, pterosaurs and bats.
Animals can develop the capacity to fly when they manage to beat gravity. Their skeleton is modified so as to be lighter and their previous members turn into wings to have propulsive capacity. Furthermore, flight demands a complete modification of all senses to make them extremely keen and sensitive because any mistake in the landing or equilibrium can result in death.
These changes are reflected in the greater or lesser development of certain brain structures. “For instance, the cerebellum –in charge of controlling the equilibrium- was more developed in pterosaurs, what indicates a good development of the optical passage reflex and a great dependence on visual stabilization, and this coincides with the evolutionary need to have a better control of that aspect”, Carabajal comments.
In this regard, the anatomy of the Allkaruen brain is similar to the one of living birds, where the cerebral hemisphere are considerably expanded, the olfactory bulbs are small and the optic lobes are highly developed, thus proving that the sense of vision was one of the most important ones of these species.
“Its evolution is one of the least known subjects because due to their adaptation to flight, this species had extremely delicate bones such as the birds nowadays. The remains of these flying reptiles are preserved only under specific conditions. In this context, the find of a new flying reptile becomes really significant”, Pol concludes.
About the research:
Diego Pol. Principal researcher. MEF.
Ariana Paulina Carabajal. Associate researcher. INIBIOMA.
Laura Codorniú. Associate researcher. UNSL.
David Unwin. School of Museum Studies, University of Leicester, UK.
Oliver W.M. Rauhut. Department of Earth and Environmental Sciences and GeoBioCenter, Germany.
By Ana Belluscio.