Fred Ruhe
Well-known member
Guillermo Navalón, Luis M. Chiappe, Augustin G. Martinelli, William Nava & Daniel J. Field, 2022
Fossil basicranium clarifies the origin of the avian central nervous system and inner ear
Proceedings of the Royal Society B: Biological Sciences. 289 (1983). 20221398. doi:10.1098/rspb.2022.1398
Abstract and free pdf: https://royalsocietypublishing.org/doi/10.1098/rspb.2022.1398
Among terrestrial vertebrates, only crown birds (Neornithes) rival mammalsin terms of relative brain size and behavioural complexity. Relatedly,the anatomy of the avian central nervous system and associated sensorystructures, such as the vestibular system of the inner ear, are highly modifiedwith respect to those of other extant reptile lineages. However, a dearth of three-dimensional Mesozoic fossils has limited our knowledge of the originsof the distinctive endocranial structures of crown birds. Traits such as an expanded, flexed brain, a ventral connection between the brain and spinalcolumn, and a modified vestibular system have been regarded as exclusiveto Neornithes. Here, we demonstrate all of these‘advanced’traits in anundistorted braincase from an Upper Cretaceous enantiornithine bonebed in southeastern Brazil. Our discovery suggests that these crown bird-like endocranial traits may have originated prior to the split between Enantiornithes and the more crownward portion of avian phylogeny over 140 Ma, while coexisting with a remarkably plesiomorphic cranial base and posterior palate region. Altogether, our results support the interpretation that the distinctive endocranial morphologies of crown birds and their Mesozoic relatives are affected by complex trade-offs between spatial constraintsduring development.
Enjoy,
Fred
Fossil basicranium clarifies the origin of the avian central nervous system and inner ear
Proceedings of the Royal Society B: Biological Sciences. 289 (1983). 20221398. doi:10.1098/rspb.2022.1398
Abstract and free pdf: https://royalsocietypublishing.org/doi/10.1098/rspb.2022.1398
Among terrestrial vertebrates, only crown birds (Neornithes) rival mammalsin terms of relative brain size and behavioural complexity. Relatedly,the anatomy of the avian central nervous system and associated sensorystructures, such as the vestibular system of the inner ear, are highly modifiedwith respect to those of other extant reptile lineages. However, a dearth of three-dimensional Mesozoic fossils has limited our knowledge of the originsof the distinctive endocranial structures of crown birds. Traits such as an expanded, flexed brain, a ventral connection between the brain and spinalcolumn, and a modified vestibular system have been regarded as exclusiveto Neornithes. Here, we demonstrate all of these‘advanced’traits in anundistorted braincase from an Upper Cretaceous enantiornithine bonebed in southeastern Brazil. Our discovery suggests that these crown bird-like endocranial traits may have originated prior to the split between Enantiornithes and the more crownward portion of avian phylogeny over 140 Ma, while coexisting with a remarkably plesiomorphic cranial base and posterior palate region. Altogether, our results support the interpretation that the distinctive endocranial morphologies of crown birds and their Mesozoic relatives are affected by complex trade-offs between spatial constraintsduring development.
Enjoy,
Fred
