DOI: 10.5061/dryad.qv9s4mwdk
title: High-density 3-D coordinate data of avian and non-avian dinosaur endocasts

description: How do large and unique brains evolve? Historically, comparative
 neuroanatomical studies have attributed the evolutionary genesis of highly
 encephalized brains to deviations along, as well as from, conserved
 scaling relationships among brain regions. However, the relative
 contributions of these concerted (integrated) and mosaic (modular)
 processes as drivers of brain evolution remain unclear, especially in
 non-mammalian groups. While proportional brain sizes have been the
 predominant metric used to characterize brain morphology to date, we
 perform a high-density geometric morphometric analysis on the encephalized
 brains of crown birds (Neornithes or Aves) compared to their stem taxa—the
 non-avialan coelurosaurian dinosaurs. When analyzed together with
 developmental neuroanatomical data of model archosaurs
 (Gallus, Alligator), crown birds exhibit a distinct allometric
 relationship that dictates their brain evolution and development.
 Furthermore, analyses by neuroanatomical regions reveal that the
 acquisition of this derived shape-to-size scaling relationship occurred in
 a mosaic pattern, where the ‘avian’-grade optic lobe and cerebellum
 evolved first among non-avialan dinosaurs, followed by major changes to
 the evolutionary and developmental dynamics of cerebrum shape after the
 origin of Avialae. Notably, the brain of crown birds is a more integrated
 structure than non-avialan archosaurs, implying that diversification of
 brain morphologies within Neornithes proceeded in a more coordinated
 manner, perhaps due to spatial constraints and abbreviated growth period.
 Collectively, these patterns demonstrate a plurality in evolutionary
 processes that generate encephalized brains in archosaurs and across
 vertebrates.
description: The landmark data were collected using the program Landmark
 Editor v3.6 to virtually place three-dimensional (3-D) coordinate points
 on polygon mesh files of endocasts reconstructed from micro-computed
 tomography (CT) data. The landmark scheme includes a combination of
 discrete landmarks, curve semi-landmarks, and surface semi-landmarks that
 characterizes the shape of endocasts and their regions (cerebrum, optic
 lobe, cerebellum, medulla). Initially, coordinate data were collected from
 both sides of the endocasts (e.g., left and right cerebrum) which were
 subjected to generalized Procrustes alignment minimizing total bending
 energy with sliding semi-landmarks while projecting the semi-landmarks on
 mesh surfaces. After alignment, the median and left landmarks were
 extracted (i.e., right landmarks removed) from the aligned dataset to
 remove redundant shape information and to avoid artifacts associated with
 aligning one-sided data of bilaterally symmetric structures.
description: The dataset is organized as a 2-D matrix, where rows are
 specimens and columns are coordinate values. The specimen sampling (n=72)
 comprises six non-avialan coelurosaurian dinosaurs (specimens
 2,42,55,56,57,72 in dataset), <em>Archaeopteryx</em> (specimen
 19), and 38 crown birds (specimens 1,17,18, 20–26,41,43–54,58–71), as well
 as developmental series of <em>Alligator</em> (specimens 3–16)
 and <em>Gallus</em> (specimens 27–40).
 Important Note: The dataset includes 225 3-D (semi-)landmarks
 that encompass bilateral form of endocasts. The semi-landmarks have been
 slid based on minimizing total bending energy and scale has been retained
 so that centroid size could still be calculated. To prevent artifacts
 related to aligning one-sided coordinate data of bilateral structures, the
 dataset should first be subjected to typical generalized Procrustes
 alignment minimizing total Procrustes distance without sliding
 semilandmarks because sliding has already been conducted. After alignment,
 then the left and median (semi-)landmarks should be extracted:
 landmarks 1–54, 109–137, 168–170, 173–175, 178–180, 183–185, 188–190,
 193–195, 198–200, 203–205, 208–210, 213–215, 218–220, 222–224. This
 left-sided dataset should include 119 3-D (semi-)landmarks. The landmark
 dataset is partitioned into left cerebrum (landmarks 1–54), left optic
 lobe (landmarks 55–83), left side of cerebellum (landmarks 84–101), and
 left side of medulla (102–119).