Comparative brain morphology of Neotropical parrots (Aves, Psittaciformes) inferred from virtual 3D endocasts

Abstract

Psittaciformes are a very diverse group of non-passerine birds, with advanced cognitive abilities and highly developed locomotor and feeding behaviours. Using computed tomography and three-dimensional (3D) visualization software, the endocasts of 14 extant Neotropical parrots were reconstructed, with the aim of analysing, comparing and exploring the morphology of the brain within the clade. A 3D geomorphometric analysis was performed, and the encephalization quotient (EQ) was calculated. Brain morphology character states were traced onto a Psittaciformes tree in order to facilitate interpretation of morphological traits in a phylogenetic context. Our results indicate that: (i) there are two conspicuously distinct brain morphologies, one considered walnut type (quadrangular and wider than long) and the other rounded (narrower and rostrally tapered); (ii) Psittaciformes possess a noticeable notch between hemisphaeria that divides the bulbus olfactorius; (iii) the plesiomorphic and most frequently observed characteristics of Neotropical parrots are a rostrally tapered telencephalon in dorsal view, distinctly enlarged dorsal expansion of the eminentia sagittalis and conspicuous fissura mediana; (iv) there is a positive correlation between body mass and brain volume; (v) psittacids are characterized by high EQ values that suggest high brain volumes in relation to their body masses; and (vi) the endocranial morphology of the Psittaciformes as a whole is distinctive relative to other birds. This new knowledge of brain morphology offers much potential for further insight in paleoneurological, phylogenetic and evolutionary studies.

Comparative morphology of snake (Squamata) endocasts: evidence of phylogenetic and ecological signals

“…, ; Carril et al. ). Several studies on snake brain have shown a link between structure and function (Kubie et al.…”

“…Computed tomography (CT) allows the reconstruction of high-quality 3D models of both hard and soft tissues that can be used for different purposes, such as anatomical and biomechanical studies. It thus constitutes an important exploratory tool in biology and opens a range of new possible investigations (Boistel et al 2011a;Carril et al 2015).…”

“…Computed tomography is now widely used to visualize the endocranial space with the construction of digital endocasts that may reflect the morphology of the brain and associated tissues (Anderson et al 2000;Macrini et al 2007;Olori, 2010;Bienvenu et al 2011;Smith & Clarke, 2012;Racicot & Colbert, 2013;Ahrens, 2014;Carril et al 2015;Corfield et al 2015;Danilo et al 2015;Gonzales et al 2015;Kawabe et al 2015), the inner ear (Chapla et al 2007;Georgi & Sipla, 2008;Walsh et al 2009;Ekdale, 2010Ekdale, , 2011Ekdale, , 2013Willis et al 2013), the vascular system (Porter & Witmer, 2015), the cranial nerves (George & Holliday, 2013) and pneumatic sinuses (Bona et al 2013). Endocasts are generated at the interface between the skeleton (typically bone or cartilage) and the soft tissues (or fluid) lying immediately near it (Balanoff et al 2015).…”

Novel insights into early neuroanatomical evolution in penguins from the oldest described penguin brain endocast

“…Phylogenetically informed studies of gross neuroanatomical characters remain uncommon – neuroanatomical apomorphies have been detected in two major avian clades: Charadriiformes (Smith & Clarke, ) and Psittaciformes (Carril et al. ). Comparative study of the endocranial features of the Paleognathae has also been examined, supporting the presence of endocranial apomorphies in this clade as well (Corfield et al.…”

“…; Carril et al. ), providing insight into avian neuroanatomical variation as it relates to phylogeny, sensory function, and ecology.…”