The skin of birds' feet: Morphological adaptations of the plantar surface.

The skin of the foot provides the interface between the bird and the substrate. The foot morphology involves the bone shape and the integument that is in contact with the substrate. The podotheca is a layer of keratinized epidermis forming scales that extends from the tarsometatarsus to the toe extremities. It varies in size, shape, amount of overlap and interacts with the degree of fusion of the toes (syndactyly). A study of toe shape and the podotheca provides insights on the adaptations of perching birds. Our analysis is based on micro-CT scans and scanning electron microscopy images of 21 species from 17 families, and includes examples with different orientations of the toes: zygodactyl (toes II and III forward), anisodactyl (toes II, III, and IV forward), and heterodactyl (toes III and IV forward). We show that in these three groups, the skin forms part of a perching adaptation that involves syndactyly to different degrees. However, syndactyly does not occur in Psittacidae that use their toes also for food manipulation. The syndactyly increases the sole surface and may reinforce adherence with the substrate. Scale shape and toe orientation are involved in functional adaptations to perch. Thus, both bone and skin features combine to form a pincer-like foot.

To Hop or Not to Hop? The Answer Is in the Bird Trees.

Birds can use different types of gaits to move on the ground: they either walk, hop, or run. Although velocity can easily explain a preference for running, it remains unclear what drives a bird species to favor hopping over walking. As many hopping birds are relatively small and arboreal, we wanted to test the link between size, arboreality, and hopping ability. First, we carried out ancestral character state reconstructions of size range, hopping ability, and habitat traits on over 1000 species of birds. We found that both hopping ability and arboreality were derived and significantly correlated traits in avian evolution. Second, we tested the influence of hopping ability on the morphology of the lower appendicular skeleton by quantifying the shape differences of the pelvis and the three long bones of the hind limbs in 47 avian species with different habitats and gait preferences. We used geometric morphometrics on 3D landmarks, digitized on micro-computed tomography (micro-CT) and surface scans of the pelvis, femur, tibiotarsus, and tarsometatarsus. Locomotion habits significantly influence the conformation of the pelvis, especially at the origin of hip and knee muscle extensors. Interestingly, habitat, more than locomotion habits, significantly changed tarsometatarsus conformation. The morphology of the distal part of the tarsometatarsus constrains digit orientation, which leads to a greater ability to perch, an advantageous trait in arboreality. The results of this work suggest an arboreal origin of hopping and illuminate the evolution of avian terrestrial locomotion.[Anatomy; avian; gait; leg; lifestyle; pelvis; tree-dwelling.].

Synonymization of the genus nomen Dendroplex Swainson, 1827 and description of a new genus of woodcreeper (Aves: Passeriformes: Dendrocolaptidae) with remarks on Articles 67.5 and 70.3 of the Code.

The polytypic Straight-billed Woodcreeper Dendroplex picus (J. F. Gmelin, 1788) is one of the most complex species-groups of Dendrocolaptidae (Aves: Passeriformes), from both the nomenclatural and morphological standpoints. Firstly, its alpha taxonomy is debatable. Virtually all recent works (e.g. Aleixo 2002; Marantz et al. 2003; del Hoyo Collar 2016) have recognized just two species in the group-Dendroplex picus and Zimmer's Woodcreeper Dendroplex kienerii (Des Murs, 1856)-although some of the other described taxa possess singular morphological characters and well-defined ranges somewhat isolated from their geographically closest relatives (e.g. Plain-throated Woodcreeper Dendroplex picirostris Lafresnaye, 1847). Secondly, the correct genus to which to allocate taxa presently included in this group (vide Aleixo 2002) has been controversial. There is a considerable confusion as to which nominal species should be regarded as the type of Dendroplex Swainson, 1827b. Three species are involved in the dispute (Cory Hellmayr 1925; Peters 1951; Aleixo et al. 2002; Marantz et al. 2003; Aleixo et al. 2007): Oriolus picus J. F. Gmelin, 1788; Dendrocolaptes guttatus M. H. C. Lichtenstein, 1818; and Dendrocolaptes ocellatus Spix, 1824. Here, we re-examine the nomenclatural issue and show that application of the nomen Dendroplex to the clade comprising the species-group D. picus (Aleixo et al. 2007) is based on a misunderstanding of the application of Article 70.3 of the Code (Anon. 1999) and that Dendrocolaptes ocellatus Spix, 1824, is its real type species. Consequently, the genus Dendroplex Swainson, 1827b, must be considered a junior synonym of Xiphorhynchus Swainson, 1827a. Because no generic nomen is currently available for them, we propose a new genus nomen to encompass the species originally described as Oriolus picus J. F. Gmelin, 1788, Dendroplex picirostris Lafresnaye, 1847, and Dendrornis kienerii Des Murs, 1856.

Foot shape in arboreal birds: two morphological patterns for the same pincer-like tool.

The feet are the only contact between the body and the substrate in limbed animals and as such they provide a crucial interface between the animal and its environment. This is especially true for bipedal and arboreal species living in a complex three-dimensional environment that likely induces strong selection on foot morphology. In birds, foot morphology is highly variable, with different orientations of the toes, making it a good model for the study of the role of functional, developmental, and phylogenetic constraints in the evolution of phenotypic diversity. Our data on the proportions of the phalanges analyzed in a phylogenetic context show that two different morphological patterns exist that depend mainly on habitat and toe orientation. In the anisodactyl foot, the hallux is the only backward-oriented toe and is enlarged in climbing species and reduced in terrestrial ones. Moreover, a proximo-distal gradient in phalanx size is observed depending on the degree of terrestriality. In the two other cases (heterodactyl and zygodactyl) that have two toes that point backward, the hallux is rather small in contrast to the other backward-pointing toe, which is enlarged. The first pattern is convergent and common among tetrapods and follows rules of skeletal development. The second pattern is unique for the clade and under muscle-morphogenetic control. In all cases, the functional result is the same tool, a pincer-like foot.

Relationship between jaw apparatus, feeding habit, and food source in oriental woodpeckers.

Associations among feeding habit, beak type, and food source in birds have been widely studied and are well known to exist. The relationship between feeding habit and jaw apparatus in birds has not attracted attention from ornithologists, perhaps because of the complexity of the skeletal morphology of the feeding system of birds. The goal of this study was to compare the jaw apparatus and foraging strategies of various Oriental species of the Picidae (Meiglyptini and Picini tribes) using a morphofunctional analysis of the skeletal structure of the jaw apparatus. This study showed that there are at least three types of jaw apparatus in these woodpeckers, as follows: 1) robust, developed, and complex; 2) complexity and development intermediate, as observed in Meiglyptes tristis and Dinopium spp., whose main foraging method involves gleaning, probing, and tapping; and 3) poorly developed, as observed in Picus miniaceus and Hemicircus concretus. The success of woodpeckers as a natural group is due not only to their feeding diversity, but also their ability to explore a wide range of different resources, as appropriate to their jaw apparatus.

Locomotion patterns in two South American gymnophthalmid lizards: Vanzosaura rubricauda and Procellosaurinus tetradactylus.

We quantified gait and stride characteristics (velocity, frequency, stride length, stance and swing duration, and duty factor) in the bursts of locomotion of two small, intermittently moving, closely related South American gymnophthalmid lizards: Vanzosaura rubricauda and Procellosaurinus tetradactylus. They occur in different environments: V. rubricauda is widely distributed in open areas with various habitats and substrates, while P. tetradactylus is endemic to dunes in the semi-arid Brazilian Caatinga. Both use trot or walking trot characterised by a lateral sequence. For various substrates in a gradient of roughness (perspex, cardboard, sand, gravel), both species have low relative velocities in comparison with those reported for larger continuously moving lizards. To generate velocity, these animals increase stride frequency but decrease relative stride length. For these parameters, P. tetradactylus showed lower values than V. rubricauda. In their relative range of velocities, no significant differences in stride length and frequency were recorded for gravel. However, the slopes of a correlation between velocity and its components were lower in P. tetradactylus on cardboard, whereas on sand this was only observed for velocity and stride length. The data showed that the difference in rhythmic parameters between both species increased with the smoothness of the substrates. Moreover, P. tetradactylus shows a highly specialised locomotor strategy involving lower stride length and frequency for generating lower velocities than in V. rubricauda. This suggests the evolution of a central motor pattern generator to control slower limb movements and to produce fewer and longer pauses in intermittent locomotion.

Comparative anatomy of the syrinx in the tribe arini (Aves psittacidae)

The syrinx is the organ responsible for producing the vast majority of bird sounds. Because its anatomyvaries greatly among bird taxa, prior knowledge of variations is extremely important to studies of functionalanatomy and phylogenetic systematics. With the aim of accessing and describing morphological variationin birds of the tribe Arini, this paper presents the findings of a comparative analysis of the syrinxes of 156specimens belonging to 47 species in 22 genera of the tribe. A number of hitherto unknown variationsare highlighted and confronted with the knowledge produced to date on the morphology of the syrinx inPsittaciformes. Some of the variations detected occurred in structures probably involved in sound productionand this should be taken into consideration in future studies of functional anatomy. Several characterssuggest the presence of a phylogenetic signal, given the congruence between their distribution among taxaand the hypotheses regarding monophyletic groupings proposed in the literature. Some of the variationsfound, including those suggesting a phylogenetic signal, are intraspecifically polymorphic, which reinforcesthe importance of using series of specimens in studies of syrinx anatomy.

Molecular phylogenetics and biogeography of Neotropical piping guans (Aves: Galliformes): Pipile Bonaparte, 1856 is synonym of Aburria Reichenbach, 1853.

The Cracidae are Neotropical galliform birds with 11 genera currently recognized. To investigate the questioned validity of Pipile Bonaparte, 1856 and the monotypic Aburria Reichenbach, 1853 as separate genera, we gathered data from 2727 bp of mitochondrial DNA (cytochrome b, ND2 and control region) and 151 osteological characters. Our phylogenetic analyses of DNA sequences indicated that Aburria aburri is embedded within Pipile. Also, genetic distances between Aburria and any Pipile species are equivalent to the distances estimated for other congeneric cracid species, which genus status is not doubtful. Although the osteological characters do not have phylogenetic signal to solve the phylogenetic relationships at species level, five synapomorphies were found for Aburria and Pipile. Therefore, we suggest that Pipile should be merged with Aburria, which is the oldest described genus. We estimated that speciation in this group occurred in the Plio-Pleistocene, concordant with other birds, primates and rodents that have similar geographic distribution, and proposed a diversification hypothesis based on the occurrence of sea transgressions and the formation of the Amazon Lagoon. Therefore, we conclude that these palaeogeographic events may have contributed to Neotropical taxa diversification to a greater extent than previously suspected.