Possible postcranial pneumaticity in the last common ancestor of birds and crocodilians: evidence from Erythrosuchus and other Mesozoic archosaurs

Birds and crocodilians (extant archosaurs) have differing, distinctive morphologies. Birds have respiratory airsacs with diverticula that pneumatize the postcranial skeleton, a feature absent in crocodilians. Bony correlates of pneumatic sinuses are known in the vertebrae of some non-avian dinosaurs and in pterosaurs - taxa more closely related to birds than crocodilians. This and the apparent absence of pneumatic postcranial bones in fossil archosaurs more closely related to crocodilians than to birds, has been interpreted as evidence that postcranial pneumaticity is a derived character of birds and their nearest fossil relatives. The presence of apparent osteological correlates of postcranial pneumaticity is here reported in some non-crown-group archosaurs, and some of the fossil taxa more closely related to crocodilians than to birds. This suggests that the last common ancestor of birds and crocodilians might have had a pneumatized postcranium, and that the absence of this feature in crocodilians might be derived.     

The origin and early evolution of birds: discoveries,disputes, and perspectives from fossil evidence

The study of the origin and early evolution of birds has never produced as much excitement and public attention as in the past decade. Well preserved and abundant new fossils of birds and dinosaurs have provided unprecedented new evidence on the dinosaurian origin of birds, the arboreal origin of avian flight, and the origin of feathers prior to flapping flight. The Mesozoic avian assemblage mainly comprises two major lineages: the prevalent extinct group Enantiornithes, and the Ornithurae, which gave rise to all modern birds, as well as several more basal taxa. Cretaceous birds radiated into various paleoecological niches that included fish- and seed-eating. Significant size and morphological differences and variation in flight capabilities, ranging from gliding to powerful flight among early birds, highlight the diversification of birds in the Early Cretaceous. There is little evidence, however, to support a Mesozoic origin of modern avian groups. Controversy and debate, nevertheless, surround many of these findings, and more details are needed to give a better appreciation of the significance of these new discoveries.     

Sex- and age-related differences in the timing and body condition of migrating Reed Warblers Acrocephalus scirpaceus and Sedge Warblers Acrocephalus schoenobaenus

The migration strategies of birds may vary strongly between species and also between age and/or sex groups. We studied the autumn migration and body condition of molecularly sexed Reed Warblers Acrocephalus scirpaceus and Sedge Warblers Acrocephalus schoenobaenus (211 and 208 ind., respectively) at a stopover site on Lake Druzno, Northern Poland, in 2008. Immature male Reed Warblers were caught significantly later than females (median dates 9 days later), but in the Sedge Warbler, both sexes of immatures migrated at about the same time. Adult males and females of both species did not differ in their time of migration. Adult and immature males of both species were larger (wing length and body mass) than females. In both species, fat reserves were similar in both sexes of both age classes. Adults of both sexes of Reed and Sedge Warbler were generally caught earlier than immatures. In both species, the body mass and fat reserves of immatures were generally less than in adults. The autumn protogyny of immature Reed Warblers may allow smaller females to limit competition with bigger males during migration and at the wintering grounds. In the Sedge Warbler, which tends to match its migration to peak of occurrence of superabundant food at stopover sites, both sexes gain an advantage from migrating at the same time. Since part of the measured wing length variation in both species was explained by sex differences, temporal trends in wing length recorded at stopover sites should be interpreted with caution.     

Great cormorants (<Emphasis Type="Italic">Phalacrocorax carbo</Emphasis>) can detect auditory cues while diving

In-air hearing in birds has been thoroughly investigated. Sound provides birds with auditory information for species and individual recognition from their complex vocalizations, as well as cues while foraging and for avoiding predators. Some 10% of existing species of birds obtain their food under the water surface. Whether some of these birds make use of acoustic cues while underwater is unknown. An interesting species in this respect is the great cormorant (Phalacrocorax carbo), being one of the most effective marine predators and relying on the aquatic environment for food year round. Here, its underwater hearing abilities were investigated using psychophysics, where the bird learned to detect the presence or absence of a tone while submerged. The greatest sensitivity was found at 2 kHz, with an underwater hearing threshold of 71 dB re 1 μPa rms. The great cormorant is better at hearing underwater than expected, and the hearing thresholds are comparable to seals and toothed whales in the frequency band 1–4 kHz. This opens up the possibility of cormorants and other aquatic birds having special adaptations for underwater hearing and making use of underwater acoustic cues from, e.g., conspecifics, their surroundings, as well as prey and predators.     

Minute theropod eggs and embryo from the Lower Cretaceous of Thailand and the dinosaur-bird transition

We report on very small fossil eggs from the Lower Cretaceous of Thailand, one of them containing a theropod embryo, which display a remarkable mosaic of characters. While the surficial ornamentation is typical of non-avian saurischian dinosaurs, the three-layered prismatic structure of the eggshell is currently known only in extant and fossil eggs associated with birds. These eggs, about the size of a goldfinch's, mirror at the reproductive level the retention of small body size that was paramount in the transition from non-avian theropods to birds. The egg-layer may have been a small feathered theropod similar to those recently found in China.     

The evolutionary position of turtles revised

Consensus on the evolutionary position of turtles within the amniote phylogeny has eluded evolutionary biologists for more than a century. This phylogenetic problem has remained unsolved partly because turtles have such a unique morphology that only few characters can be used to link them with any other group of amniotes. Among the many alternative hypotheses that have been postulated to explain the origin and phylogenetic relationships of turtles, a general agreement among paleontologists emerged in favoring the placement of turtles as the only living survivors of the anapsid reptiles (those that lack temporal fenestrae in the skull). However, recent morphological and molecular studies have radically changed our view of amniote phylogenetic relationships, and evidence is accumulating that supports the diapsid affinities of turtles. Molecular studies favor archosaurs (crocodiles and birds) as the living sister group of turtles, whereas morphological studies support lepidosaurs (tuatara, lizards, and snakes) as the closest living relatives of turtles. Accepting these hypotheses implies that turtles cannot be viewed any longer as primitive reptiles, and that they might have lost the temporal holes in the skull secondarily rather than never having had them.     

First evidence of poisonous shrews with an envenomation apparatus

Herein, we report evidence of an envenomation apparatus (EA) in two different species of extinct “giant” shrews, Beremendia and an indeterminate soricine (Mammalia, Eulipotyphla, Soricidae), documented by very well preserved fossil specimens recovered from two Early Pleistocene cave deposits of the Sierra de Atapuerca in Burgos, Spain. The two soricine taxa from Atapuerca have evolved specialized teeth as EAs, which differ from those of recently reported mammals of the Paleocene age, being more similar to the ones described in the modern Solenodon. This discovery reveals the first instance of shrews possessing what appears to be an EA, an evolutionary adaptation that, in these species, was probably related to an increase in body mass and hunting of a larger-sized prey. The Atapuerca specimens would have a highly specialized EA, one of the very few reported for an extinct or living mammal of any time. In addition to the presence of a gutter-like groove along the medial side of the crown of the lower incisors, these two species also present stout jaws and a modified mandibular symphysis with a conspicuous cavity, which in life would likely contain large amounts of connective tissue. The strong mandible architecture of these large shrews would be, in this way, reinforced by a more immovable symphysis, increasing the bite force exerted over a potential prey. This adaptation, together with the grooved incisors, would ensure a rapid and efficient transmission of the poisonous saliva to paralyze relatively large-sized prey.     

A large Cretaceous theropod from Patagonia, Argentina, and the evolution of carcharodontosaurids

The Cretaceous Carcharodontosauridae is the latest clade of carnosaurs, including the largest predatory dinosaurs yet recorded. Albeit spectacular for their size, the skeletal anatomy of these theropods remains poorly-known, and their diversity was until recently restricted to two Cenomanian species: the highly derived Giganotosaurus carolinii, from southern South America, and the incompletely known Carcharodontosaurus saharicus, from northern Africa. Here we describe an older and basal member of the group, Tyrannotitan chubutensis gen. et sp. nov., from Aptian strata of Patagonia, Argentina. The new taxon gives new insights into the systematics and evolution of carcharodontosaurids and offers a better understanding of the evolution of Southern theropod faunas. We suggest that carcharodontosaurids radiated in Gondwana sharing with spinosaurids the role of top-predators until their extinction in Cenomanian–Turonian times. During this interval, the diplodocoid sauropods and giant titanosaurians went extinct (probably as part of a global-scale crisis), and the smaller abelisaurid theropods took dominance, reigning until the end of the Cretaceous. Electronic Supplementary Material is available.Electronic Supplementary Information  Supplementary material is available for this article at     

Living in a “stethoscope”: burrow-acoustics promote auditory specializations in subterranean rodents

Subterranean mammals rely to a great extent on audition for communication and to be alerted to danger. The only hitherto published report on burrow acoustics revealed that in tunnels of blind mole-rats (Spalax ehrenbergi), airborne sounds of 440 Hz propagated best whereas lower and higher frequencies were effectively attenuated. Morpho-functional analyses classify the ear of subterranean mammals as a low-sensitivity and low-frequency device. Concordantly, hearing is characterized by low sensitivity and a restricted frequency range tuned to low frequencies (0.5–4 kHz). Some authors considered the restricted hearing in subterranean mammals vestigial and degenerate due to under-stimulation. In contrast to this view stand a rich (mostly low-frequency) vocal repertoire and progressive structural specializations of the middle and inner ear. Thus, other authors considered these hearing characteristics adaptive. To test the hypothesis that acoustical environment in burrows of different species of subterranean mammals is similar, we measured sound attenuation in burrows of Fukomys mole-rats (formerly known as Cryptomys, cf. Kock et al. 2006) of two differently sized species at different locations in Zambia. We show that in these burrows, low-frequency sounds (200–800 Hz) are not only least attenuated but also their amplitude may be amplified like in a stethoscope (up to two times over 1 m). We suggest that hearing sensitivity has decreased during evolution of subterranean mammals to avoid over-stimulation of the ear in their natural environment. We dedicate this work to Mathias Kawalika, who died in March 2006.     

Osteological evidence for sister group relationship between pseudo-toothed birds (Aves: Odontopterygiformes) and waterfowls (Anseriformes)

The phylogenetic affinities of the extinct pseudo-toothed birds have remained controversial. Some authors noted that they resemble both pelicans and allies (Pelecaniformes) and tube-nosed birds (Procellariiformes), but assigned them to a distinct taxon, the Odontopterygiformes. In most recent studies, the pseudo-toothed birds are referred to the family Pelagornithidae inside the Pelecaniformes. Here, I perform a cladistic analysis with five taxa of the pseudo-toothed birds including two undescribed new species from the Early Tertiary of Morocco. The present hypothesis strongly supports a sister group relationship of pseudo-toothed birds (Odontopterygiformes) and waterfowls (Anseriformes). The Odontoanserae (Odontopterygiformes plus Anseriformes) are the sister group of Neoaves. The placement of the landfowls (Galliformes) as the sister taxon of all other neognathous birds does not support the consensus view that the Galloanserae (Galliformes plus Anseriformes) are monophyletic. Electronic supplementary material  Supplementary material is available in the online version of this article at . Communicated by G. Mayr     

Unusually high-pitched neonate distress calls of the open-habitat Mongolian gazelle (<Emphasis Type="Italic">Procapra gutturosa</Emphasis>) and their anatomical and hormonal predictors

In neonate ruminants, the acoustic structure of vocalizations may depend on sex, vocal anatomy, hormonal profiles and body mass and on environmental factors. In neonate wild-living Mongolian gazelles Procapra gutturosa, hand-captured during biomedical monitoring in the Daurian steppes at the Russian-Mongolian border, we spectrographically analysed distress calls and measured body mass of 22 individuals (6 males, 16 females). For 20 (5 male, 15 female) of these individuals, serum testosterone levels were also analysed. In addition, we measured relevant dimensions of the vocal apparatus (larynx, vocal folds, vocal tract) in one stillborn male Mongolian gazelle specimen. Neonate distress calls of either sex were high in maximum fundamental frequency (800–900 Hz), but the beginning and minimum fundamental frequencies were significantly lower in males than in females. Body mass was larger in males than in females. The levels of serum testosterone were marginally higher in males. No correlations were found between either body mass or serum testosterone values and any acoustic variable for males and females analysed together or separately. We discuss that the high-frequency calls of neonate Mongolian gazelles are more typical for closed-habitat neonate ruminants, whereas other open-habitat neonate ruminants (goitred gazelle Gazella subgutturosa, saiga antelope Saiga tatarica and reindeer Rangifer tarandus) produce low-frequency (<200 Hz) distress calls. Proximate cause for the high fundamental frequency of distress calls of neonate Mongolian gazelles is their very short, atypical vocal folds (4 mm) compared to the 7-mm vocal folds of neonate goitred gazelles, producing distress calls as low as 120 Hz.     

Dental microwear patterns of extant and extinct Muridae (Rodentia, Mammalia): ecological implications

Extant species of Muridae occupy a wide array of habitats and have diverse dietary habits. Consequently, their dental microwear patterns represent a potential clue to better understand the paleoecology of their extinct relatives, which are abundant in many Old World Neogene localities. In this study, dental microwear is investigated for specimens of 17 extant species of murine and deomyine rodents in order to test the reliability of this method and infer dietary preferences on the fossil species Saïdomys afarensis. This extinct form comes from a mid-Pliocene site (AL 327) located at the Hadar Formation (Ethiopia) known to have delivered many hominid specimens of Australopithecus afarensis. A significant correlation between microwear patterns and diet is detected. Thus, grass, fruit, and insect eaters display, respectively, high amounts of fine scratches, wide scratches, and large pits. Moreover, some aspects of the paleoecology of S. afarensis, including feeding habits, could be assessed in regard to its dental microwear pattern. Indeed, it probably had feeding habits similar to that of living grass eaters. These results concur with the presence of open to woodland areas covered by an herbaceous vegetal layer, including monocotyledons, in the vicinity of this mid-Pliocene locality.     

湖北省湿地水禽资源研究

1996年5月至2003年7月,使用直接计数法、样方法和专项调查法研究了湖北省湿地水禽资源,包括物种多样性、分布和种群数量。结果表明:湖北省共有水禽131种,隶属于7目19科58属;记录到107种,其中有黄嘴白鹭、小苇(?)、红脚苦恶鸟和长嘴剑(?)4个新记录种。按区系型分,古北界种类占优势,有80种,广布种26种,东洋种25种;按季节型分,冬候鸟为主体,有75种,夏候鸟32种,旅鸟14种,留鸟10种;按生活型分,涉禽占优势,共81种,游禽50种。湖北省水禽种群总数为159.396 9×104只,密度为101.96只/km₂;种群数量在1×104只以上的有28种。角(?)(?)等24种未发现。     

Bizarre tubercles on the vertebrae of Eocene fossil birds indicate an avian disease without modern counterpart

Remains of fossil birds with numerous bony tubercles on the cervical vertebrae are reported from the Middle Eocene of Messel in Germany and the Late Eocene of the Quercy fissure fillings in France. These structures, which are unknown from extant birds and other vertebrates, were previously described for an avian skeleton from Messel but considered a singular feature of this specimen. The new fossils are from a different species of uncertain phylogenetic affinities and show that tuberculated vertebrae have a wider taxonomic, temporal, and geographic distribution. In contrast to previous assumptions, they are no ontogenetic feature and arise from the vertebral surface. It is concluded that they are most likely of pathologic origin and the first record of a Paleogene avian disease. Their regular and symmetrical arrangement over most of the external vertebral surface indicates a systemic disorder caused by factors that do not affect extant birds, such as especially high-dosed phytohormones or extinct pathogens.     

Hibernation and daily torpor minimize mammalian extinctions

Small mammals appear to be less vulnerable to extinction than large species, but the underlying reasons are poorly understood. Here, we provide evidence that almost all (93.5%) of 61 recently extinct mammal species were homeothermic, maintaining a constant high body temperature and thus energy expenditure, which demands a high intake of food, long foraging times, and thus exposure to predators. In contrast, only 6.5% of extinct mammals were likely heterothermic and employed multi-day torpor (hibernation) or daily torpor, even though torpor is widespread within more than half of all mammalian orders. Torpor is characterized by substantial reductions of body temperature and energy expenditure and enhances survival during adverse conditions by minimizing food and water requirements, and consequently reduces foraging requirements and exposure to predators. Moreover, because life span is generally longer in heterothermic mammals than in related homeotherms, heterotherms can employ a ‘sit-and-wait’ strategy to withstand adverse periods and then repopulate when circumstances improve. Thus, torpor is a crucial but hitherto unappreciated attribute of small mammals for avoiding extinction. Many opportunistic heterothermic species, because of their plastic energetic requirements, may also stand a better chance of future survival than homeothermic species in the face of greater climatic extremes and changes in environmental conditions caused by global warming.     

Variation of foraging rate and wing loading, but not resting metabolic rate scaling, of insect pollinators

Morphological, physiological and behavioural variation with body size (i.e. scaling) may affect costs of living in a particular environment for insects and, ultimately, pollination or foraging success. However, few studies have directly assessed the scaling of these traits at the species level. Using two similar-sized pollinator species (the hawkmoth Macroglossum trochilus and the fly Moegistorhynchus longirostrus), we compare intraspecific scaling relationships of resting metabolic rate (RMR), foraging rate (FR) and wing loading (WL) to address this paucity of data. Scaling of RMR was similar for both taxa although the intercepts for the relationships differed. However, these two species showed variation in WL scaling relationships and fundamentally different FR scaling. For M. longirostrus, FR scaling was positive but non-significantly related to body mass while for M. trochilus FR scaling was negative. This suggests that variation in FR and WL, but not RMR scaling, among these flies and hawkmoths may impose significant energetic costs which could affect animal–plant interactions in the wild.     

The Use of Low-Level Jets by Migrating Birds

 Birds flying at high altitudes have occasionally been observed above mountain areas and the open sea. For the first time the regular occurrence of migrating birds flying within a low-level jet at heights of 5000 to almost 9000 m asl. have now been verified by radar above the Negev desert in southern Israel. Tracks of rather large birds with wing-beat frequencies of 5–6 Hz were measured to have horizontal flight speeds up to 50 m/s. Visual observations, seasonal occurrence, and wing-beat frequencies allowed to associate them with small species of the order Ciconiiformes (mainly Ardeidae) and possibly with members of the Laro-Limicolae group. These wading birds seem prone to continuing nocturnal migration into daytime under favorable conditions and to make use of high wind speeds at sometimes extreme altitudes. Received: 21 June 1999 / Accepted in revised form: 26 August 1999     

The evolutionary continuum of limb function from early theropods to birds

The bipedal stance and gait of theropod dinosaurs evolved gradually along the lineage leading to birds and at some point(s), flight evolved. How and when did these changes occur? We review the evidence from neontology and palaeontology, including pectoral and pelvic limb functional morphology, fossil footprints/trackways and biomechanical models and simulations. We emphasise that many false dichotomies or categories have been applied to theropod form and function, and sometimes, these impede research progress. For example, dichotomisation of locomotor function into ‘non-avian’ and ‘avian’ modes is only a conceptual crutch; the evidence supports a continuous transition. Simplification of pelvic limb function into cursorial/non-cursorial morphologies or flexed/columnar poses has outlived its utility. For the pectoral limbs, even the classic predatory strike vs. flight wing-stroke distinction and separation of theropods into non-flying and flying—or terrestrial and arboreal—categories may be missing important subtleties. Distinguishing locomotor function between taxa, even with quantitative approaches, will always be fraught with ambiguity, making it difficult to find real differences if that ambiguity is properly acknowledged. There must be an ‘interpretive asymptote’ for reconstructing dinosaur limb function that available methods and evidence cannot overcome. We may be close to that limit, but how far can it be stretched with improved methods and evidence, if at all? The way forward is a combination of techniques that emphasises integration of neontological and palaeontological evidence and quantitative assessment of limb function cautiously applied with validated techniques and sensitivity analysis of unknown variables.     

<Emphasis Type="BoldItalic">Osedax</Emphasis> borings in fossil marine bird bones

The bone-eating marine annelid Osedax consumes mainly whale bones on the deep-sea floor, but recent colonization experiments with cow bones and molecular age estimates suggesting a possible Cretaceous origin of Osedax indicate that this worm might be able grow on a wider range of substrates. The suggested Cretaceous origin was thought to imply that Osedax could colonize marine reptile or fish bones, but there is currently no evidence that Osedax consumes bones other than those of mammals. We provide the first evidence that Osedax was, and most likely still is, able to consume non-mammalian bones, namely bird bones. Borings resembling those produced by living Osedax were found in bones of early Oligocene marine flightless diving birds (family Plotopteridae). The species that produced these boreholes had a branching filiform root that grew to a length of at least 3 mm, and lived in densities of up to 40 individuals per square centimeter. The inclusion of bird bones into the diet of Osedax has interesting implications for the recent suggestion of a Cretaceous origin of this worm because marine birds have existed continuously since the Cretaceous. Bird bones could have enabled this worm to survive times in the Earth’s history when large marine vertebrates other than fish were rare, specifically after the disappearance of large marine reptiles at the end-Cretaceous mass extinction event and before the rise of whales in the Eocene.