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Beyond endocasts: using predicted brain structure volumes of extinct birds to assess neuroanatomical and behavioral inferences Project ID: 00000C882 Public
35 Media · 33 Specimens · Managed by: Catherine Early

DESCRIPTION

The shape of the brain influences skull morphology in birds, and both traits are driven by
phylogenetic and functional constraints. Studies on avian cranial and neuroanatomical evolution are
strengthened by data on extinct birds, but complete, 3D-preserved vertebrate brains are not known
from the fossil record, so brain endocasts often serve as proxies. Recent work on extant birds shows
that the Wulst and optic lobe faithfully represent the size of their underlying brain structures, both of
which are involved in avian visual pathways. The endocasts of seven extinct birds were generated
from microCT scans of their skulls to add to an existing sample of endocasts of extant birds, and the
surface areas of their Wulsts and optic lobes were measured. A phylogenetic prediction method
based on Bayesian inference was used to calculate the volumes of the brain structures of these extinct
birds based on the surface areas of their overlying endocast structures. This analysis resulted in
hyperpallium volumes of five of these extinct birds and optic tectum volumes of all seven extinct
birds. Phylogenetic ANCOVA (phyANCOVA) were performed on regressions of the brain-structure
volumes and endocast structure surface areas on various brain size metrics to determine if the relative
sizes of these structures in any extinct birds were significantly different from those of the extant
birds in the sample. Phylogenetic ANCOVA indicated that no extinct birds studied had relative
hyperpallial volumes that were significantly different from the extant sample, nor were any of their
optic tecta relatively hypertrophied. The optic tectum of Dinornis robustus was significantly smaller
relative to brain size than any of the extant birds in our sample. This study provides an analytical
framework for testing the hypotheses of potential functional behavioral capabilities of other extinct
birds based on their endocasts.

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Number of media
35
Number of represented specimens
33
Number of represented cultural heritage objects
0
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