Morphometric Study of Phylogenetic and Ecologic Signals in Procyonid (Mammalia: Carnivora) Endocasts

Abstract

Endocasts provide a proxy for brain morphology but are rarely incorporated in phylogenetic analyses despite the potential for new suites of characters. The phylogeny of Procyonidae, a carnivoran family with relatively limited taxonomic diversity, is not well resolved because morphological and molecular data yield conflicting topologies. The presence of phylogenetic and ecologic signals in the endocasts of procyonids will be determined using three-dimensional geometric morphometrics. Endocasts of seven ingroup species and four outgroup species were digitally rendered and 21 landmarks were collected from the endocast surface. Two phylogenetic hypotheses of Procyonidae will be examined using methods testing for phylogenetic signal in morphometric data. In analyses of all taxa, there is significant phylogenetic signal in brain shape for both the morphological and molecular topologies. However, the analyses of ingroup taxa recover a significant phylogenetic signal for the morphological topology only. These results indicate support for the molecular outgroup topology, but not the ingroup topology given the brain shape data. Further examination of brain shape using principal components analysis and wireframe comparisons suggests procyonids possess more developed areas of the brain associated with motor control, spatial perception, and balance relative to the basal musteloid condition. Within Procyonidae, similar patterns of variation are present, and may be associated with increased arboreality in certain taxa. Thus, brain shape derived from endocasts may be used to test for phylogenetic signal and preliminary analyses suggest an association with behavior and ecology. Anat Rec, 297:2318Rec, 297: -2330Rec, 297: , 2014. V C 2014 Wiley Periodicals, Inc.Key words: neuroanatomy; encephalization; phylogeny; Procyonidae; MephitidaeNeuroanatomy and the evolution of brain size have long been of interest to paleomammalogists. The foundations for interpreting differences in brain size and shape in Mammalia were established, in part, by work on the

Endocranial shape variation in the squirrel‐related clade and their fossil relatives using 3D geometric morphometrics: contributions of locomotion and phylogeny to brain shape

“…The olfactory bulbs of arboreal squirrels are slightly shorter compared to other groups. Ahrens () also discovered that large paraflocculi and relatively small olfactory bulbs were present in arboreal Procyonidae Carnivora (e.g. raccoons, coatis, kinkajous) but absent in the more terrestrial musteloids such as Martes (Ahrens, ).…”

“…Three‐Dimensional GM has been employed by paleontologists to examine the relationship between the shape of the bony labyrinth (Grohé et al ., ), cranial (Samuels, ; Samuels & Van Valkenburgh, ; Hautier, Lebrun & Cox, ; Curtis & Van Valkenburgh, ; Lu et al ., ), and postcranial (Milne, Vizcaíno & Fernicola, ) elements in association with variables such as phylogeny and ecology in mammals. Less common has been the use of GM to study cranial endocasts in mammals, although some recent studies have investigated endocranial shape variation within the genus Homo (Bruner, Manzi & Arsuaga, ), among carnivores (Ahrens, ; Iurino et al ., ), and in the species Equus caballus (Danilo et al ., ). Endocasts are the imprint of the brain against the inner part of the cranium and are the best proxy for investigating brain shape and size in fossil mammals because brain tissues are not preserved in the fossil record (e.g., Edinger, ; Jerison, ).…”

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

“…; Olori, ; Bienvenu et al. ; Smith & Clarke, ; Racicot & Colbert, ; Ahrens, ; Carril et al. ; Corfield et al.…”

“…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).…”

Neuroanatomy and inner ear labyrinths of the narwhal, Monodon monoceros, and beluga, Delphinapterus leucas (Cetacea: Monodontidae)

“…Macrini et al. ,b; Macrini, ; Ekdale, , ; Ahrens, ). Establishing levels of variation and areas of morphology more prone to variation in populations informs on the functional importance (or lack thereof) of certain features (e.g.…”