Müller et al. 2020 brought us a first peek
at a basal dinosaur brain within an excellent Buriolestes specimen (Fig. 1).
From the Müller et al. abstract:
“Our knowledge on the anatomy of the first dinosaurs (Late Triassic, 235–205 Ma) has drastically increased in the last years, mainly due to several new findings of exceptionally well‐preserved specimens. Nevertheless, some structures such as the neurocranium and its associated structures (brain, labyrinth, cranial nerves, and vasculature) remain poorly known, especially due to the lack of specimens preserving a complete and articulated neurocranium. This study helps to fill this gap by investigating the endocranial cavity of one of the earliest sauropodomorphs, Buriolestes schultzi, from the Upper Triassic (Carnian—c. 233 Ma) of Brazil.”
Here, in the large reptile tree (LRT, 1760+ taxa; subset Fig. 2) Buriolestes nests basal to Sauropodomorpha. It also nests basal to another plant-eating clade, Ornithischia. It also nests basal to several other basal phytodinosaurs at the base of the LRT clade Phytodinosauria. Add pertinent taxa to discover this for yourself.
Continuing the Müller et al. abstract:
“The endocranial anatomy of this animal sheds light on the ancestral condition of the brain of sauropodomorphs, revealing an elongated olfactory tract combined to a relatively small pituitary gland and well‐developed flocculus of the cerebellum. These traits change drastically across the evolutionary history of sauropodomorphs, reaching the opposite morphology in Jurassic times.”
“Furthermore, we present here the first calculations of the Reptile Encephalization Quotient (REQ) for a Triassic dinosaur. The REQ of B. schultzi is lower than that of Jurassic theropods, but higher than that of later sauropodomorphs. The combination of cerebral, dental, and postcranial data suggest that B. schultzi was an active small predator, able to track moving prey.”
Recovered outgroups in the LRT include Herrerasaurus, Staurikosaurus and Gnathovorax, three bipedal Middle Triassic predators. So it’s no surprise that Buriolestes was considered an active small predator based on its brain and teeth.
Author quotes in the NYTimes:
“They found that one portion of the cerebellum, the floccular lobe, was particularly large in Buriolestes.
“This structure is related with the capability to track prey with the eyes,” Dr. Müller said.”
Buriolestes also had small olfactory bulbs, suggesting that smell wasn’t of crucial importance to the little hunter. In later sauropods, these bulbs grew in relative size, which might have helped them smell each other or detect predators.
Most striking, however, was the brain’s large size relative to the rest of the body, Dr. Müller said. In many lineages, relative brain size increases over time, he said — but not, apparently, in this case. “Probably this change is related with the feeding habits changing,” he said. “Carnivorous animals generally need more cognitive capabilities.”
These details about Buriolestes’s brain are intriguing because it is such an early dinosaur, said Lawrence Witmer, a paleontologist and professor of anatomy at Ohio University who studies sauropods.
“It gives us a window into the earliest evolution of the brain and sensory systems of the largest animals ever to walk on land, the sauropod dinosaurs,” he said, noting that Buriolestes’s inner ear canal and floccular lobe suggest it used quick, coordinated movements of the head, neck and eyes.”
Cabreira SF et al. (13 co-authors) 2016. A unique Late Triassic dinosauromorph assemblage reveals dinosaur ancestral anatomy and diet. Current Biology (2016), http://dx.doi.org/10.1016/j.cub.2016.09.040
Greenwood V 2020. “We’ve Rarely Seen a Dinosaur Brain Like This Before – While later dinosaurs in this lineage were giant herbivores with tiny brains, this small species packed a lot more power in its skull”. The New York Times. Retrieved 3 November 2020.
Müller RT et al. (5 co-authors 2018. Early evolution of sauropodomorphs: anatomy and phylogenetic relationships of a remarkably well-preserved dinosaur from the Upper Triassic of southern Brazil. Zoological Journal of the Linnean Society, zly009 (advance online publication) doi: https://doi.org/10.1093/zoolinnean/zly009
Müller RT, Ferreira JD, Pretto F A, Bronzati M and Kerber L 2020. The endocranial anatomy of Buriolestes schultzi (Dinosauria: Saurischia) and the early evolution of brain tissues in sauropodomorph dinosaurs. Journal of Anatomy 2020; 00: 1– 19. https://doi.org/10.1111/joa.13350