Fred Ruhe
Well-known member
NEUROANATOMICAL EVOLUTION OF PALAEOGNATHS: INSIGHT FROM NEW CRANIAL ENDOCASTS OF ELEPHANT BIRDS (AEPYORNITHIFORMES)
TORRES, Christopher R., University of Texas at Austin, Austin, TX, United States of America; VIOLA, Paul, University of Texas at Austin, Austin, TX, United States of America; ELIASON, Chad M., University of Texas at Austin, Austin, TX, United States of America; CLARKE, Julia A., University of Texas at Austin, Austin, TX, United States of America
The evolutionary history of palaeognathous birds is marked by repeated evolution of island endemism, gigantism, nocturnality and flight loss. Understanding whether and how the neuroanatomy of palaeognaths tracks these patterns could shed light on the processes by which these patterns occurred. In particular, the endocranial morphology of extinct Malagasy elephant birds, the largest birds that ever lived, represents a crucial gap in our understanding of the neuroanatomical evolution of these birds. Here, we report new digital reconstructions of the endocasts and endosseous labyrinths of adult elephant birds, a moa, and a cassowary, and compare them with other palaeognaths and representatives from across Aves. The resulting 3D digital models were analyzed in a comparative framework taking into account phylogeny and used to infer ancestral head posture and identify evolutionarily shifts in neuroanatomy. Many neuroanatomical traits show variation across Palaeognathae, including the size and shape of the olfactory bulbs and development of the telencephalon, Wulst, optic lobe and cerebellum. In particular, the optic lobe of the elephant bird is highly reduced. Only the nocturnal kiwi shows more midbrain reduction, and we suggest the elephant bird may have had a similar nocturnal activity pattern. The elephant bird and kiwi, recovered as sister taxa by molecular phylogenetic analyses, also display many endocranial differences, for example, in the size and shape of the telencephalon and pneumaticity of the skull roof. The endosseous labyrinth has been mostly overlooked in investigations of palaeognath neuroanatomy; our study reveals striking differences in the shape and orientation of semicircular canals among palaeognaths, even among elephant birds. These neuroanatomical shifts, as well as others reported here, indicate trends in brain shape evolution among palaeognaths that likely correspond to changes in locomotor mode and activity patterns.
TORRES, Christopher R., University of Texas at Austin, Austin, TX, United States of America; VIOLA, Paul, University of Texas at Austin, Austin, TX, United States of America; ELIASON, Chad M., University of Texas at Austin, Austin, TX, United States of America; CLARKE, Julia A., University of Texas at Austin, Austin, TX, United States of America
The evolutionary history of palaeognathous birds is marked by repeated evolution of island endemism, gigantism, nocturnality and flight loss. Understanding whether and how the neuroanatomy of palaeognaths tracks these patterns could shed light on the processes by which these patterns occurred. In particular, the endocranial morphology of extinct Malagasy elephant birds, the largest birds that ever lived, represents a crucial gap in our understanding of the neuroanatomical evolution of these birds. Here, we report new digital reconstructions of the endocasts and endosseous labyrinths of adult elephant birds, a moa, and a cassowary, and compare them with other palaeognaths and representatives from across Aves. The resulting 3D digital models were analyzed in a comparative framework taking into account phylogeny and used to infer ancestral head posture and identify evolutionarily shifts in neuroanatomy. Many neuroanatomical traits show variation across Palaeognathae, including the size and shape of the olfactory bulbs and development of the telencephalon, Wulst, optic lobe and cerebellum. In particular, the optic lobe of the elephant bird is highly reduced. Only the nocturnal kiwi shows more midbrain reduction, and we suggest the elephant bird may have had a similar nocturnal activity pattern. The elephant bird and kiwi, recovered as sister taxa by molecular phylogenetic analyses, also display many endocranial differences, for example, in the size and shape of the telencephalon and pneumaticity of the skull roof. The endosseous labyrinth has been mostly overlooked in investigations of palaeognath neuroanatomy; our study reveals striking differences in the shape and orientation of semicircular canals among palaeognaths, even among elephant birds. These neuroanatomical shifts, as well as others reported here, indicate trends in brain shape evolution among palaeognaths that likely correspond to changes in locomotor mode and activity patterns.
