Flightless Research Articles

The specialized thoracic skeletomuscular system of the myrmecophile Claviger testaceus (Pselaphinae, Staphylinidae, Coleoptera)

External and internal structures of the thorax of the myrmecophile beetle Claviger testaceus (Clavigeritae, Pselaphinae) were examined and documented with state-of-the-art visualization techniques. Following a general trend in the omaliine lineage (Staphylinidae), the skeletal elements of the pro- and pterothorax in Claviger reach a maximum degree of compactness, with largely reduced inter- and intrasegmental sutures and skeletal elements linked with the flight apparatus. The musculature, especially metathoracic direct and indirect flight muscles, also shows a high degree of reduction. Two forms of wings were found among individuals of C. testaceus, both non-functional and representing an advanced stage of reduction. However, that wing vestiges are still present and the metanotum, only slightly reduced, suggests that loss of flight in this species is likely the result of a young evolutionary process. Several structures are linked with myrmecophilous habits: small body size facilitates transportation of beetles by ant workers and makes it easier to move inside nest tunnels; the remarkably compact body and mechanically robust appendages make the beetles less vulnerable to attacks by ant mandibles; the improved elytral interlocking mechanism and unusually expanded epipleura enhance the protection of vulnerable dorsal parts of the pterothorax and anterior abdomen; and glands associated with trichomes on the posterolateral elytral angle produce secretions attractive for ants. Various modifications of the thorax and anterior abdomen lead to an optimization of intimate associations with ants. The morphological syndrome enabling these beetles to cope with life in ant colonies evolved in several steps. This is suggested by an increasing solidification of the thoracic skeleton in related non-myrmecophilous groups and also by less modified related clavigerites;for instance, ant-associated tropical species are still able to fly.

First assessment of persistent organic pollutants in the Greater rhea (Rhea americana), a near-threatened flightless herbivorous bird of the Pampas grasslands.

Persistent organic pollutants (POPs) are still globally distributed and can exert different effects on ecosystems. Little is known about the occurrence of these contaminants in terrestrial birds from South America. In this study, POPs were assessed for the first time in a flightless herbivorous species from the Pampas grasslands, the Greater rhea (Rhea americana). Concentrations of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCPs) were determined in 18 samples of feathers from free-ranging and captive individuals inhabiting four sites with different land uses in central Argentina. Among the 16 POPs tested in those feathers, 6 PCBs (28, 52, 101, 138, 153, and 180) and 8 OCPs (α-HCH, β-HCH, γ-HCH, p,p'-DDE, p,p'-DDD, o,p'-DDT, p,p'-DDT, and HCB) were quantified. No PBDEs were detected. The total concentration of POPs was higher in populations living in an intensive crop production area (agriculture 159 ng g -1 and farm: 97.53 ng g-1) compared with the population in an urban area (zoo 45.86 ng g-1) and an agroecosystem with extensive rearing of livestock (cattle rearing 36.77 ng g-1). PCBs were the most abundant pollutants in all the populations studied. Lower chlorinated CB 52 and CB 101 were the principal PCB congeners detected, representing at least 70% of the total quantified. All populations studied showed a DDE + DDD/DDT ratio > 1, indicating a historical application of this insecticide. This study provides a new contribution to the scarce data on POP concentrations in South American bird species. Further investigations are needed to evaluate their potential effects on the health of individuals and populations.

Assume the Globe: Tennyson's Jubilee Ode and the Institutions of Imperialism

Assume the Globe:Tennyson's Jubilee Ode and the Institutions of Imperialism Cornelia Pearsall (bio) [L]eft to itself all power tends ultimately to construct a chimeric coherence for itself—with its fixations, its archaic landscapes, its arbitrary importance, and its pathological forms. Achille Mbembe, "Thinking, in Lightning and Thunder" The world has not yet seen an 'Imperial Institute' and no one appears yet to know precisely what it is for," observed a reviewer in The British Architect, assessing the six finalists in a design competition for a building to commemorate the 1887 Jubilee of Queen Victoria. Lacking clarity about the intentions of the Imperial Institute of the United Kingdom, the Colonies, and India (its full title), "[e]ach architect seems to have had to fancy for himself the sort of thing an Imperial Institute should be." This impression of confusion, or indeed absence, of purpose leads the author to suggest a startling analogy: "it seems very much like asking six Palaeontologists to furnish plans and elevations for a dodo, without supplying them with bones to evolve it from."1 The dodo, a flightless bird native to Mauritius that had gone extinct by the late seventeenth century, less than a century after its first recorded sighting by Dutch sailors, was for Victorian Britain a figure for failure of a potentially comical sort.2 Even had the imagined paleontologists possessed sufficient fossil evidence, to reverse engineer a dodo is to construct an organism marked from inception for extinction, to design for disappearance. Form could not follow function in the "plans and elevations" for the Imperial Institute, which had been proposed by the Prince of Wales; thus, dysfunction was built into the structure from its foundation. "Already a failure" was the prescient verdict of Thomas H. Huxley, a major proponent of Darwinian evolutionary theory who was an avid early supporter but soon an embittered detractor of the Imperial Institute. Before the building had begun to take material shape, he declared it destined "to become eventually a ghost [End Page 177] like the Albert Hall or revive as a tea garden" (Sheppard, p. 222). It became the latter before it became the former—one of various bathetic trajectories this essay traces—but this prediction had already found correlative voicing in a poem that, paradoxically, helped bring this doomed institution into being. Alfred Tennyson's "Carmen Sæculare. An Ode in Honour of the Jubilee of Queen Victoria," commonly called the Jubilee Ode, also suggests the Imperial Institute's proleptic collapse before the building took actual form. The poem's own form itself became, like the building, an object of amused dismissal. Both the institute and the ode found correlates in a grandiose and short-lived organization that became similarly subject to charges of internal incoherence and irrelevance, the Imperial Federation League, which had disbanded by 1893, less than a decade after its founding in 1884. The organization boasted a prominent membership, including the Poet Laureate, as well as J. R. Seeley, the historian and author of the highly influential 1883 imperialist treatise, The Expansion of England: Two Courses of Lectures. This is a crucial affiliation in Tennyson's final decade; as a footnote in Hallam Tennyson's two-volume memoir of his father states, "[o]ne of the deepest desires of his life was to help the realization of the ideal of an Empire by the most intimate union of every part of our British Empire."3 A specific aim of the Imperial Federation League was to promote the permanent union of the British Empire into a single federal entity, with a London-based imperial parliament responsible for common trade and defense policy.4 This desire for the "most intimate" and permanent union of all parts of the empire was expressed by both the organization and the ode. When in 1893 the Imperial Institute formally opened its doors, George Baden-Powell, in an article titled "The Empire and Its Institute," called it not only "a necessity" but also "the consummation of what is meant by the popular phrase 'Imperial Federation.'"5 The first part of this essay addresses some aims and influences of the Imperial Federation League, especially in its multimodal ideological intersections...

Genomics Reveals Widespread Ecological Speciation in Flightless Insects.

Recent genomic analyses have highlighted parallel divergence in response to ecological gradients, but the extent to which altitude can underpin such repeated speciation remains unclear. Wing reduction and flight loss have apparently evolved repeatedly in montane insect assemblages and have been suggested as important drivers of hexapod diversification. We test this hypothesis using genomic analyses of a widespread wing-polymorphic stonefly species complex in New Zealand. We identified over 50,000 polymorphic genetic markers generated across almost 200 Zelandoperla fenestrata stonefly specimens using a newly generated plecopteran reference genome, to reveal widespread parallel speciation between sympatric full-winged and wing-reduced ecotypes. Rather than the existence of a single, widespread, flightless taxon (Zelandoperla pennulata), evolutionary genomic data reveal that wing-reduced upland lineages have speciated repeatedly and independently from full-winged Z. fenestrata. This repeated evolution of reproductive isolation between local ecotype pairs that lack mitochondrial DNA differentiation suggests that ecological speciation has evolved recently. A cluster of outlier single-nucleotide polymorphisms detected in independently wing-reduced lineages, tightly linked in an approximately 85 kb genomic region that includes the developmental "supergene" doublesex, suggests that this "island of divergence" may play a key role in rapid ecological speciation. [Ecological speciation; genome assembly; genomic island of differentiation; genotyping-by-sequencing; incipient species; plecoptera; wing reduction.].

Wind plays a major but not exclusive role in the prevalence of insect flight loss on remote islands.

Terrestrial species on islands often show reduced dispersal abilities. For insects, the generality of explanations for island flight loss remains contentious. Although habitat stability is considered the most plausible explanation, others are frequently highlighted. Adopting a strong inference approach, we examined the hypotheses proposed to account for the prevalence of flightlessness in island insect assemblages, for a region long suspected to be globally unusual in this regard-the Southern Ocean Islands (SOIs). Combining comprehensive faunal inventories, species' morphological information, and environmental variables from 28 SOIs, we provide the first quantitative evidence that flightlessness is exceptionally prevalent among indigenous SOI insect species (47%). Prevalence among species which have evolved elsewhere is much lower: Arctic island species (8%), species introduced to the SOIs (17%), and globally (estimated as approx. 5%). Variation in numbers of flightless species and genera across islands is best explained by variation in wind speed, although habitat stability (thermal seasonality proxy) may play a role. Variables associated with insularity, such as island size, are generally poor predictors of flightlessness. The outcomes redirect attention to Darwin's wind hypothesis. They suggest, however, that wind selects for flightlessness through an energy trade-off between flight and reproduction, instead of by displacement from suitable habitats.

Anthropogenic extinctions conceal widespread evolution of flightlessness in birds

Human-driven extinctions can affect our understanding of evolution, through the nonrandom loss of certain types of species. Here, we explore how knowledge of a major evolutionary transition-the evolution of flightlessness in birds-is biased by anthropogenic extinctions. Adding data on 581 known anthropogenic extinctions to the extant global avifauna increases the number of species by 5%, but quadruples the number of flightless species. The evolution of flightlessness in birds is a widespread phenomenon, occurring in more than half of bird orders and evolving independently at least 150 times. Thus, we estimate that this evolutionary transition occurred at a rate four times higher than it would appear based solely on extant species. Our analysis of preanthropogenic avian diversity shows how anthropogenic effects can conceal the frequency of major evolutionary transitions in life forms and highlights the fact that macroevolutionary studies with only small amounts of missing data can still be highly biased.

Description of a new species of Gastornis (Aves, Gastornithiformes) from the early Eocene of La Borie, southwestern France

The early Eocene locality of La Borie is located near the village of Saint-Papoul, in southwestern France. It consists of clay deposits that have yielded numerous vertebrate fossils, including remains of the giant flightless bird Gastornis. These remains were initially attributed to the species G. parisiensis, which is otherwise recorded from the late Paleocene and earliest Eocene of the North Sea Basin. New fossil birds collected in the La Borie clay pit in 2018 include an almost complete mandible of Gastornis. We describe a new species of Gastornis based on this mandible and we show that the previously described remains from La Borie must be assigned to this new species. The new species differs from other species of Gastornis in the morphology of the mandible, maxilla and quadrate. The morphological diversity of the genus Gastornis, which existed in Europe for at least 17 million years, is emphasized.LSID of publication: urn:lsid:zoobank.org:pub:10E7938B-C972-4127-94DC-169D35977B11.

Guilt through association: Reputational contagion and the Boeing 737-MAX disasters

The unfortunate set of circumstances surrounding the loss of both Lion Air Flight 610 and Ethiopian Airlines Flight 302 led to the immediate grounding of the advertised ‘incredibly fuel-efficient’ Boeing 737-MAX. The side-effects of the decision to ground such flights led to delays and cancellation of orders. Companies with entire Boeing fleets and a heavy reliance on the proposed cost-savings in an ultra-competitive industry thereby made their shareholders aware that identified future revenue generation was now on hold indefinitely. Results indicate that investors identified this reliance, but also, the subsequent negative polarity and subjectivity of social media response is found to have significantly influenced the share price of airlines with no fleet diversification, and subsequently, no reputational diversification.

Simultaneous Wing Molt as a Catalyst for the Evolution of Flightlessness in Birds.

AbstractComplex features, such as vision, limbs, and flight, have been lost by many groups of animals. Some groups of birds are more prone to loss of flight than others, but few studies have investigated possible reasons for this variation. I tested the hypothesis that a rare strategy of flight feather replacement is involved in rate variation in the evolution of flightlessness in birds. This strategy involves a simultaneous molt of the flight feathers of the wing, resulting in a temporary flightless condition during molt. I hypothesized that adaptations for this flightless period may serve as preadaptations for permanent flightlessness under conditions that favor permanent loss of flight. I found an elevated rate of loss of flight in lineages with simultaneous wing molt compared with loss of flight in lineages without simultaneous wing molt. This may indicate that birds with simultaneous molt are more prepared to adjust quickly to open niches that do not require flight, such as terrestrial niches on island habitats. These results illustrate how molt strategies can influence the long-term evolutionary trajectories of birds and provide insight into how phenotypic precursors may act as a mechanism of rate variation in the loss of complex traits.

The loss of flight in ant workers enabled an evolutionary redesign of the thorax for ground labour

BackgroundExplanations for the ecological dominance of ants generally focus on the benefits of division of labour and cooperation during foraging. However, the principal innovation of ants relative to their wasp ancestors was the evolution of a new phenotype: a wingless worker caste optimized for ground labour. Ant workers are famous for their ability to lift and carry heavy loads, but we know surprisingly little about the morphological basis of their strength. Here we examine the consequences of the universal loss of flight in ant workers on skeletomuscular adaptations in the thorax for enhanced foraging on six legs.ResultsUsing X-ray microcomputed tomography and 3D segmentation, we compared winged queens and wingless workers in Euponera sikorae (subfamily Ponerinae) and Cataglyphis savignyi (subfamily Formicinae). Workers are characterized by five major changes to their thorax: i) fusion of the articulated flight thorax (queens) into a rigid box optimized to support the muscles that operate the head, legs and abdomen, ii) redesign of internal cuticular structures for better bracing and muscle attachment, iii) substantial enlargement of the neck muscles for suspending and moving the head, iv) lengthening of the external trochanter muscles, predominant for the leg actions that lift the body off the ground, v) modified angle of the petiole muscles that are key for flexion of the abdomen. We measured volumes and pennation angles for a few key muscles to assess their increased efficacy. Our comparisons of additional workers across five genera in subfamilies Dorylinae and Myrmicinae show these modifications in the wingless thorax to be consistent. In contrast, a mutillid wasp showed a different pattern of muscle adaptations resulting from the lack of wing muscles.ConclusionsRather than simply a subtraction of costly flight muscles, we propose the ant worker thorax evolved into a power core underlying stronger mandibles, legs, and sting. This contrasts with solitary flightless insects where the lack of central place foraging generated distinct selective pressures for rearranging the thorax. Stronger emphasis is needed on morphological innovations of social insects to further our understanding of the evolution of social behaviours.

Some like it odd: Long‐term research reveals unusual behaviour in the flightless Kagu of New Caledonia

AbstractThe observation of rare behaviours can provide unexpected insights into the biology of a species. Here, we report new observations of unusual or rare behaviours by the Kagu Rhynochetos jubatus of New Caledonia, a flightless bird already known for many curious traits. We observed the broken‐wing display, adoption of a chick by a neighbouring family and flexibility in the selection of cooperative breeding partners in response to disruption in their social organisation. Although infrequent, these observations demonstrate the highly developed social flexibility that enables Kagu to counter heavy population losses caused by predation. We think that rare behaviours could often be overlooked in species because restricted research objectives might not allow their discovery.

Using playback to estimate the distribution and density of the world’s smallest flightless bird, the Inaccessible Island Rail Atlantisia rogersi

SummaryThe Inaccessible Island Rail Atlantisia rogersi, the world’s smallest extant flightless bird, is endemic to Inaccessible Island, a 14-km2 uninhabited island in the Tristan da Cunha archipelago, central South Atlantic Ocean. Rail populations are notoriously hard to survey and the rugged topography of Inaccessible Island makes a survey particularly challenging. Fortunately, Inaccessible Island Rails are very vocal, because their secretive behaviour means birds are hard to observe in the dense vegetation. We assessed the distribution of rails across Inaccessible Island using playbacks at 350 point-count sites in October–November 2018. Rail calls were heard at 98% of sites and we estimate the rail population to be in the order of 10,300 birds (95% CI 9,100–12,200), based on estimated rail densities in the six main habitats. Historic population estimates were reasonably crude and thus not suitable for inferring population trends, but the population appears to be stable and we recommend the species’ status remains as ‘Vulnerable’. The accidental introduction of alien mammals poses the greatest threat to the survival of the Inaccessible Island Rail and the removal of house mouse Mus musculus and ship rat Rattus rattus from neighbouring Tristan da Cunha Island would greatly reduce the risk of such a catastrophe.

The origin of the giant ground beetleAplothorax burchellion St Helena Island

AbstractSome highly isolated oceanic islands harbour endemic ground beetles that have lost the ability to fly. Here, we investigated the origin of the possibly extinct flightless giant ground beetle Aplothorax burchelli on St Helena Island in the South Atlantic. Aplothorax burchelli was initially considered to be a member of the subtribe Calosomina (=genus Calosoma) of the subfamily Carabinae (Coleoptera: Carabidae) closely related to the genus Ctenosta (=Calosoma subgenus Ctenosta), but this proposition was questioned due to its unique external and genital morphology. We conducted a phylogenetic analysis of mitogenome sequences using historical specimens of A. burchelli and samples of representative species of Carabinae. Our analysis of 13 protein-coding gene sequences revealed that A. burchelli is definitely a member of Calosomina, most closely related to a species of Ctenosta. Further analysis using NADH dehydrogenase subunit 5 gene sequences from most groups in Calosomina showed that A. burchelli formed a monophyletic group with Ctenosta species from Africa and Madagascar. Our results suggest that the ancestor of A. burchelli, which had the ability to fly, colonized St Helena from Africa after the emergence of the island 14 Mya, and has since undergone evolutionary changes in conjunction with loss of flight.

Osteological description of casque ontogeny in the southern cassowary (Casuarius casuarius) using micro-CT imaging.

Extant cassowaries (Casuarius) are unique flightless birds found in the tropics of Indo-Australia. They have garnered substantial attention from anatomists with focus centered on the bony makeup and function of their conspicuous cranial casques, located dorsally above the orbits and neurocranium. The osteological patterning of the casque has been formally described previously; however, there are differing interpretations between authors. These variable descriptions suggest that an anatomical understanding of casque anatomy and its constituent elements may be enhanced by developmental studies aimed at further elucidating this bizarre structure. In the present study, we clarify casque osteology of the southern cassowary (C. casuarius) by detailing casque anatomy across an extensive growth series for the first time. We used micro-computed tomography (μCT) imaging to visualize embryonic development and post-hatching ontogeny through adulthood. We also sampled closely related emus (Dromaius novaehollandiae) and ostriches (Struthio camelus) to provide valuable comparative context. We found that southern cassowary casques are comprised of three paired (i.e., nasals, lacrimals, frontals) and two unpaired elements (i.e., mesethmoid, median casque element). Although lacrimals have rarely been considered as casque elements, the contribution to the casque structure was evident in μCT images. The median casque element has often been cited as a portion of the mesethmoid. However, through comparisons between immature C. casuarius and D. novaehollandiae, we document the median casque element as a distinct unit from the mesethmoid.

Nocturnal dispersal flight of crickets: Behavioural and physiological responses to cool environmental temperatures

Abstract Flight of nocturnal insects may be limited by cool nighttime environmental temperatures. We used laboratory and field experiments to explore the thermal basis of nocturnal flight in wing‐polymorphic Gryllus lineaticeps crickets consisting of long‐winged (LW), flight‐capable morphs and short‐winged (SW), flight‐incapable morphs. These crickets are a model for life history evolution and loss of flight, but their thermal requirements for flight have been unknown. We hypothesized that LW crickets achieve warm body temperatures required for flight through a combination of behavioural thermoregulation, producing heat endogenously (either by initiating muscular thermogenesis or increasing resting metabolic rate) and minimizing heat loss (by circulatory adjustments or insulation). Summer evening air temperatures in the field gradually declined from 25 to 18°C during the hours of nighttime cricket activity. Laboratory LW crickets did not fly at a body temperature of 18°C, and 60% flew at 25°C. In an experimental thermal gradient, spontaneous flight did not occur until body temperature exceeded 35°C, confirming that nocturnal field air temperature limits flight in this species. In a thermal gradient, LW crickets preferred higher temperatures (~36°C) than SW crickets (~32.5°C). In the field, all crickets were warmer than air temperature but considerably cooler than their preferred temperatures. LW crickets had higher field body temperatures (24.3°C) than SW crickets (22.3°C). LW crickets spontaneously initiated muscular thermogenesis through wing vibrations, increasing body temperature to a pre‐flight maximum of 35°C. Muscular thermogenesis was limited below 25°C. LW crickets cooled more slowly and had higher metabolic rates than SW crickets. We conclude that LW crickets prepare to fly on cool nights by gaining heat from warm substrates, activating endogenous muscular thermogenesis and reducing their cooling rate. These mechanisms are absent or less pronounced in SW crickets. The overall thermoregulatory strategy we report represents a previously unrecognized component of insect dispersal polymorphism. We suggest that thermal constraints on nocturnal flight may have contributed to evolutionary loss of flight in other insect groups. A free Plain Language Summary can be found within the Supporting Information of this article.

First description of an ostrich from the late Miocene of Kerassia (Euboea, Greece): remarks on its cervical anatomy

ABSTRACT The present study describes an almost complete cervical region of the fossil ostrich Struthio karatheodoris from the Turolian locality of Kerassia (Euboea, Greece). The material comes from two distinct fossiliferous horizons and consists of twelve cervical vertebrae, ten of which belong to the same individual. These specimens are the first remains of a large flightless bird from Kerassia and represent some of the very few findings of the genus Struthio in the sub-Paratethyan (Balkan-Iranian) bioprovince from the late Miocene. The morphology of the cervical vertebrae implies that the neck of S. karatheodoris had similar biomechanical properties to that of extant ostriches, pointing to similar ecological adaptations, relating to food procurement. However, it probably had a more flexible and stronger neck, which might indicate a somewhat different ecology. Furthermore, considerable intraspecific size and morphological variation of the cervical vertebrae of S. karatheodoris is observed. This signifies that S. karatheodoris was not necessarily larger than S. camelus as previously suspected, but their size ranges in fact overlap significantly.

Convergent morphological responses to loss of flight in rails (Aves: Rallidae).

The physiological demands of flight exert strong selection pressure on avian morphology and so it is to be expected that the evolutionary loss of flight capacity would involve profound changes in traits. Here, we investigate morphological consequences of flightlessness in a bird family where the condition has evolved repeatedly. The Rallidae include more than 130 recognized species of which over 30 are flightless. Morphological and molecular phylogenetic data were used here to compare species with and without the ability to fly in order to determine major phenotypic effects of the transition from flighted to flightless. We find statistical support for similar morphological response among unrelated flightless lineages, characterized by a shift in energy allocation from the forelimbs to the hindlimbs. Indeed, flightless birds exhibit smaller sterna and wings than flighted taxa in the same family along with wider pelves and more robust femora. Phylogenetic signal tests demonstrate that those differences are independent of phylogeny and instead demonstrate convergent morphological adaptation associated with a walking ecology. We found too that morphological variation was greater among flightless rails than flighted ones, suggesting that relaxation of physiological demands during the transition to flightlessness frees morphological traits to evolve in response to more varied ecological opportunities.

Complete mitochondrial genomes offer insights into the evolutionary relationships and comparative genetic diversity of New Zealand’s iconic kiwi (Apteryx spp.)

ABSTRACT Kiwis (Apterygidae) are an enigmatic family of flightless birds endemic to New Zealand. Apterygidae is made up of a single genus, Apteryx with five species, four of which are characterised as at risk of greater by the New Zealand Department of Conservation. These five species are further separated into two morphologically and genetically distinguishable clades, containing A.haastii, and A.owenii in one and A.rowi, A.mantelli, and A.australis in the other. We reconstructed 17 kiwi mitochondrial genomes from previously published genomic data, nine from A.rowi and eight from A.owenii. Mitochondrial diversity analyses uncovered low levels of genetic diversity consistent with their reduced ranges and conservation concern. We further used one of the assembled A.rowi mitochondrial genomes together with mitochondrial genomes from A.haastii, A.owenii, A.mantelli, and several other individuals from Palaeognathae to estimate the within and between clade divergence times of kiwis. Our study exemplifies how available published data can be used in novel ways to provide new and complementary evolutionary insights to previous studies.

Morphological Disparity of the Humerus in Modern Birds

From a functional standpoint, the humerus is a key element in the skeleton of vertebrates as it is the forelimb’s bone that connects with the pectoral girdle. In most birds, the humerus receives both the forces exerted by the main flight muscles and the aerodynamical stresses exerted upon the wing during locomotion. Despite this functional preeminence, broad scale studies of the morphological disparity of the humerus in the crown group of birds (Neornithes) are lacking. Here, we explore the variation in shape of the humeral outline in modern birds and its evolutionary relationship with size and the evolution of different functional regimes, including several flight strategies, wing propelled diving and complete loss of wing locomotory function. Our findings suggest that most neornithines evolved repeatedly towards a general humeral morphology linked with functional advantages related with more efficient flapping. Lineages evolving high-stress locomotion such as hyperaeriality (e.g., swifts), hovering (e.g., hummingbirds) and wing-propelled diving (e.g., penguins) greatly deviate from this general trend, each exploring different morphologies. Secondarily flightless birds deviate to a lesser degree from their parent clades in humeral morphology likely as a result of the release from constraints related with wing-based locomotion. Furthermore, these taxa show a different allometric trend that flighted birds. Our results reveal that the constraints of aerial and aquatic locomotion are main factors shaping the macroevolution of humeral morphology in modern birds.

Between space and time. Naturalist taphonomic observations of lesser rhea (Rhea pennata pennata) remains in southern patagonia and its archaeological implications

The results of taphonomic observations of modern bones of lesser rhea, a large flightless bird, endemic to South America, are presented. The aim was to know the sequence of disarticulation and destruction of bone elements of this species, as a means to interpret and understand the anatomical frequencies in zooarcheological assemblages. The results obtained in a wide spatial or landscape scale are combined with those of longitudinal or long-term observations of naturally deposited lesser rhea carcasses. These bird remains are scarce in the archaeological deposits of the region, while exhibiting an anatomical representation in which the elements of the hindlimbs predominate. Actualistic observations showed a similar representation in modern natural assemblages, in which the joints that last longer include the pelvis/sacrum-hindlimbs, and hindlimbs elements from each other. The latter are the last to be destroyed. That is to say that two different processes, natural recycling and the human action of selective transport, can result in the same representation pattern of skeletal parts of Rhea pennata pennata, which poses a problem of equifinality that is difficult to solve.