A new longirostrine dyrosaurid (Crocodylomorpha,Mesoeucrocodylia) from the Paleocene of north‐eastern Colombia: biogeographic and behavioural implications for New‐World Dyrosauridae

Abstract: Fossils of dyrosaurid crocodyliforms are limited in South America, with only three previously diagnosed taxa including the short‐snouted Cerrejonisuchus improcerus from the Paleocene Cerrejón Formation of north‐eastern Colombia. Here we describe a second dyrosaurid from the Cerrejón Formation, Acherontisuchus guajiraensis gen. et sp. nov., based on three partial mandibles, maxillary fragments, teeth, and referred postcrania. The mandible has a reduced seventh alveolus and laterally depressed retroarticular process, both diagnostic characteristics of Dyrosauridae. Acherontisuchus guajiraensis is distinct among known dyrosaurids in having a unique combination of craniomandibular characteristics, and postcranial morphology that suggests it may have occupied a more placid, fluvial habitat than most known Old‐World dyrosaurids. Results from a cladistic analysis of Dyrosauridae, using 82 primarily cranial and mandibular characters, support an unresolved relationship between A. guajiraensis and a combination of New‐ and Old‐World dyrosaurids including Hyposaurus rogersii, Congosaurus bequaerti, Atlantosuchus coupatezi, Guarinisuchus munizi, Rhabdognathus keiniensis and Rhabdognathus aslerensis. Our results are consistent with an African origin for Dyrosauridae with multiple dispersals into the New World during the Late Cretaceous and a transition from marine habitats in ancestral taxa to more fluvial habitats in more derived taxa.     

Oxygen isotope fractionation between crocodilian phosphate and water

Oxygen isotope compositions of phosphate (δ¹⁸O_p) were measured in tooth enamel from captive and wild individuals of 8 crocodilian species. A rough linear correlation is observed between the δ¹⁸O_p of all the studied species and the oxygen isotope composition of ambient water (δ¹⁸O_w). Differences in mean air temperature, diet and physiology could contribute significantly to the large scatter of δ¹⁸O_p values. The combination of these parameters results in a fractionation equation for which the slope (0.82) is lower than that expected (≥ 1) from predictive model equations that assume temperature and diet as fixed parameters. Taking into account large uncertainties, the observed oxygen isotope fractionation between phosphate and ambient water does not statistically differ from that formerly established for aquatic turtles. Case studies show that δ¹⁸O_p values of fossil crocodile tooth enamel can be used to discriminate between marine and freshwater living environments within a precision of about ± 2‰ only.     

New data on the Dyrosauridae (Crocodylomorpha) from the Paleocene of Togo

Following our fieldwork in Paleogene deposits of Togo, we herein report cranial as well as postcranial elements belonging to the family Dyrosauridae. This assemblage is dated to the Late Paleocene (Thanetian) from two quarries in southern Togo. The specimens include a partial skull presenting two large supratemporal fossae and a massive occipital condyle; long and slender isolated teeth; amphicoelous vertebrae including several articulated ones; and two osteoderms devoid of carina. The morphology of the partial skull reveals similarities with some African longirostrine forms such as Rhabdognathus spp., although this attribution cannot be confirmed. Longirostrine forms, known in the late Paleocene and early Eocene of the Iullemmeden basin (Nigeria, Niger, Mali, Algeria) and in the phosphates of Morocco and Tunisia, is only represented in Thanetian levels in Togo. Different palaeoenvironmental settings seem to have characterized the various African basins during the lower Eocene, with consequences for the geographic distribution of dyrosaurids. These dyrosaurid remains confirm the presence of the family in Togo during the Paleocene and underline the fossiliferous potential of the coastal sedimentary basin in Togo and in the bay of Benin.     

The information processing organisms

In spite of the tremendous progress in recent decades of biological science, many aspects of the behaviour of organisms in general and of humans in particular remain still somewhat obscure. A new approach towards the study of the behaviour of man was presented by Heisenberg when he emphasized that a Cartesian view of nature as an object “out there” is an illusion in so far as “the observer is always part of the formula, the man viewing nature must be figured in, the experimenter into his experiment and the artist in the scene he paints.” (Heisenberg, 1969). The present study is an attempt to make a step forward in this direction by focusing on the ways and means of involvement of the observer which make him an indelible part of the observation. To get a fresh start let us have a look at the physical universe. Although showing an immense variety, all objects, living and non-living, have some characteristics in common. They all obey the physical laws and they all are engaged in perpetual interactions. How do we tell then the difference between living and non-living objects? According to the traditional concept it is the capacity for reproduction that distinguishes living from non-living objects. (Luria et al., 1981). The non-traditional concept presented in this study stresses the way in which objects interact as the crucial point of difference between living and non-living objects. This concept claims that living objects assert themselves as such only when and while interacting in terms of information processing. Under such conditions only, living objects are able to display relative independence of the physical laws, for instance active movement. This display of relative independence is governed by biological laws and defines the behaviour of the living objects as active in principle. All objects who share these characteristics are called living, they behave as wholes assessing themselves as individuals. The definition suggests that they all share the same internal organization which is principally dynamic.     

Anatomy of the crocodilian spinal vein

The crocodilian spinal vein is remarkably robust yet historically overlooked. Using corrosion casting, we describe the anatomy of this vessel and its connections with the caval and hepatic venous systems in representatives from four crocodilian genera. The spinal vein arises from an enlarged occipital sinus over the medulla and extends the entire length of the vertebral column. Unlike in squamate reptiles, the spinal vein is single (nonplexiform), voluminous, and situated dorsal to the spinal cord, and plexi lateral to the cord span between emerging intercostal veins. The connections with the other venous systems are otherwise similar to those in other tetrapods. The overall anatomy of this vessel and its abundant connections with the other venous systems indicate it likely plays a primary role in returning blood to the heart from all parts of the body. Preliminary studies of function suggest that this vessel could also play an adaptive role during basking and diving.     

Space competition in the acorn woodpecker: Power struggles in a cooperative breeder

During a 5-year study of the cooperatively living acorn woodpecker Melanerpes formicivorus, I observed 26 irruptions of agonistic behaviour involving large numbers of intruders invading a territory. Evidence from several sources suggests that these invasions are usually contests among potential immigrants for the opportunity to replace a missing group member (hence, ‘power struggles’). Thus, power struggles indicate intense competition among individuals to transfer out of their natal group. Such dispersal is not necessarily excluded by the hypothesis that individuals gain directly by living in cooperative groups through either increased foraging efficiency or better predator defence. However, birds involved in power struggles expend considerable energy and incur considerable risks. These costs are likely to be an acceptable part of dispersal only if cooperative living is a result of birds being forced to remain in groups as a result of resource localization.     

Arboreality,terrestriality and bipedalism

The full publication of Ardipithecus ramidus has particular importance for the origins of hominin bipedality, and strengthens the growing case for an arboreal origin. Palaeontological techniques however inevitably concentrate on details of fragmentary postcranial bones and can benefit from a whole-animal perspective. This can be provided by field studies of locomotor behaviour, which provide a real-world perspective of adaptive context, against which conclusions drawn from palaeontology and comparative osteology may be assessed and honed. Increasingly sophisticated dynamic modelling techniques, validated against experimental data for living animals, offer a different perspective where evolutionary and virtual ablation experiments, impossible for living mammals, may be run in silico, and these can analyse not only the interactions and behaviour of rigid segments but increasingly the effects of compliance, which are of crucial importance in guiding the evolution of an arboreally derived lineage.     

Influence of predation risk on the sheltering behaviour of the coral-dwelling damselfish, <Emphasis Type="Italic">Pomacentrus moluccensis</Emphasis>

Predation is a key ecosystem function, especially in high diversity systems such as coral reefs. Not only is predation one of the strongest top-down controls of prey population density, but it also is a strong driver of prey behaviour and function through non-lethal effects. We ask whether predation risk influences sheltering behaviour of damselfish living in mutualism with branching corals. Host corals gain multiple advantages from the mutualistic relationship which are determined by the strength of damselfish sheltering. Distance travelled by the Lemon Damselfish Pomacentrus moluccensis away from their host colony was measured here as a proxy for sheltering strength and was expected to be shortest under highest predation risk. Predation risk, defined as a function of predator abundance and activity, turbidity and habitat complexity, was quantified at four reef slope sites in Kepulauan Seribu, Indonesia. Damselfish sheltering strength was measured using stationary unmanned video cameras. Small damselfish (< 2 cm) increased their sheltering strength under high turbidity. Predator feeding activity, but not abundance, influenced damselfish sheltering strength. Contrary to our expectations, sheltering behaviour of adult damselfish decreased under high predator activity. While these observations are in line with risk-averse behaviour by juvenile P. moluccensis, they may indicate the presence of sentinel behaviour in the adults of this species. Habitat complexity seemed to be less important as a driver of damselfish behaviour. These counterintuitive results may indicate complex social behaviour and age-specific strategies for predator avoidance.     

In search of the last common ancestor: new findings on wild chimpanzees

Modelling the behaviour of extinct hominins is essential in order to devise useful hypotheses of our species'' evolutionary origins for testing in the palaeontological and archaeological records. One approach is to model the last common ancestor (LCA) of living apes and humans, based on current ethological and ecological knowledge of our closest living relations. Such referential modelling is based on rigorous, ongoing field studies of the chimpanzee (Pan troglodytes) and the bonobo (Pan paniscus). This paper reviews recent findings from nature, focusing on those with direct implications for hominin evolution, e.g. apes, using elementary technology to access basic resources such as food and water, or sheltering in caves or bathing as thermoregulatory adaptations. I give preference to studies that directly address key issues, such as whether stone artefacts are detectible before the Oldowan, based on the percussive technology of hammer and anvil use by living apes. Detailed comparative studies of chimpanzees living in varied habitats, from rainforest to savannah, reveal that some behavioural patterns are universal (e.g. shelter construction), while others show marked (e.g. extractive foraging) or nuanced (e.g. courtship) cross-populational variation. These findings allow us to distinguish between retained, primitive traits of the LCA versus derived ones in the human lineage.     

Inferring kinship from behaviour: Maternity determinations in yellow baboons

Kinship is commonly inferred from behaviour in primate field studies, but the validity of such inferences has not yet been documented. A comparison of the relationships of six three-year-old yellow baboon (Papio cynocephalus) females with 14 adult females showed that when a juvenile's mother was living she could easily be identified from behavioural data. The most useful behaviour in this context was Presenting For Grooming. When the mother was not living, however, the juvenile compensated by forming a strong relationship with a less closely related or unrelated adult female. If compensation also occurs in other populations and other species, past attempts to infer kinship from behaviour have probably included a few cases in which a female was incorrectly identified as a juvenile's mother. Multivariate statistical techniques revealed differences between mother-daughter relationships and strong relationships based on compensation among other individuals. These differences involved comparisons of the frequencies of certain behaviours (frequency of Grooming by adult versus frequency of Grooming by juvenile, frequency of Grooming versus frequency of aggression) as well as the magnitudes of frequencies (amount of Grooming, number of Interventions).     

A sentinel system in the Florida scrub jay

One postulated advantage of living in groups is increased protection from predators. Living in small, permanent groups of stable composition allows for the formation of a sentinel system, in which individuals coordinate their vigilance. Florida scrub jays, Aphelocoma coerulescens coerulescens, live in family groups, and coordinate their vigilance into a sentinel system. Observed vigilance behaviour was compared with models generating similar behaviour patterns at random. The occurrence of one jay terminating vigilance in the same minute that another initiated vigilance was greater than expected by chance, and the occurrence of more than one vigilant jay at one time was less frequent than expected by chance. The seasonal pattern of scrub jay sentinel behaviour suggests that it functions primarily for predator detection, especially of raptors. Most aerial predator alarm calls were given by sentinels, and a sentinel was most likely to give the alarm call first.     

Solving the riddle of codon usage preferences: a test for translational selection

Translational selection is responsible for the unequal usage of synonymous codons in protein coding genes in a wide variety of organisms. It is one of the most subtle and pervasive forces of molecular evolution, yet, establishing the underlying causes for its idiosyncratic behaviour across living kingdoms has proven elusive to researchers over the past 20 years. In this study, a statistical model for measuring translational selection in any given genome is developed, and the test is applied to 126 fully sequenced genomes, ranging from archaea to eukaryotes. It is shown that tRNA gene redundancy and genome size are interacting forces that ultimately determine the action of translational selection, and that an optimal genome size exists for which this kind of selection is maximal. Accordingly, genome size also presents upper and lower boundaries beyond which selection on codon usage is not possible. We propose a model where the coevolution of genome size and tRNA genes explains the observed patterns in translational selection in all living organisms. This model finally unifies our understanding of codon usage across prokaryotes and eukaryotes. Helicobacter pylori, Saccharomyces cerevisiae and Homo sapiens are codon usage paradigms that can be better understood under the proposed model.     

Présence du crocodilienPhosphatosaurus (Mesosuchia,Dyrosauridae) dans le paléocène du niger et du Mali

Jaw fragments of the large dyrosaurid crocodilianPhosphatosaurus Bergounioux, 1955, previously known only from the Lower Eocene of Tunisia, are described from the Lower Palaeocene of Niger and Mali. Teeth described by Gemmellaro from the Maastrichtian of Egypt are also referred to a similar form. Although too incomplete to be specifically identified, all these remains indicate that this group of dyrosaurids with a robust snout and large teeth has differentiated early. The evolution of the genusPhosphatosaurus was marked by an elongation of the mandibular symphysis. Résumé Des restes de mâchoires du grand Crocodilien dyrosauridéPhosphatosaurus Bergounioux, 1955, connu jusqu’ici seulement dans l’Eocène inférieur de Tunisie, sont décrits en provenance du Paléocène inférieur du Niger et du Mali. Des dents du Maestrichtien d’Egypte décrites par Gemmellaro sont aussi rapportées à une forme similaire. Bien que trop incomplets pour être identifiés spécifiquement, tous ces restes montrent que ce groupe de Dyrosauridae à museau robuste et à grosses dents s’est différencié de façon précoce. L’évolution du genrePhosphatosaurus a été marquée par une elongation de la symphyse mandibulaire.     

The daytime behaviour of domestic cats in a free-roaming population

The cats (Felis catus) of this study were found to fluctuate daily between solitary and group living. These temporal changes in behaviour were interpreted as reflecting adjustments made by the cats for maximum use of different food sources available at these times. The dependence on both a solitary and communal life style for food procurement prevented any intricacy of either pattern from evolving. The structure of each behavioural pattern is discussed.     

Dispersion Behaviour of Silica Nanoparticles in Biological Media and Its Influence on Cellular Uptake

Given the increasing variety of manufactured nanomaterials, suitable, robust, standardized in vitro screening methods are needed to study the mechanisms by which they can interact with biological systems. The in vitro evaluation of interactions of nanoparticles (NPs) with living cells is challenging due to the complex behaviour of NPs, which may involve dissolution, aggregation, sedimentation and formation of a protein corona. These variable parameters have an influence on the surface properties and the stability of NPs in the biological environment and therefore also on the interaction of NPs with cells. We present here a study using 30 nm and 80 nm fluorescently-labelled silicon dioxide NPs (Rubipy-SiO₂ NPs) to evaluate the NPs dispersion behaviour up to 48 hours in two different cellular media either supplemented with 10% of serum or in serum-free conditions. Size-dependent differences in dispersion behaviour were observed and the influence of the living cells on NPs stability and deposition was determined. Using flow cytometry and fluorescence microscopy techniques we studied the kinetics of the cellular uptake of Rubipy-SiO₂ NPs by A549 and CaCo-2 cells and we found a correlation between the NPs characteristics in cell media and the amount of cellular uptake. Our results emphasize how relevant and important it is to evaluate and to monitor the size and agglomeration state of nanoparticles in the biological medium, in order to interpret correctly the results of the in vitro toxicological assays.     

Adaptive significance of antipredator behaviour in artiodactyls

We used comparative data to test functional hypotheses for 17 antipredator behaviour patterns in artiodactyls. We examined the literature for hypotheses about auditory and visual signals, defensive behaviour and group-related antipredator behaviour in this taxon and derived a series of predictions for each hypothesis. Next, we documented occurrences of these behaviour patterns and morphological, ecological and behavioural variables for 200 species and coded them in binary format. We then pitted presence of an antipredator behaviour against presence of an independent variable for cervids, bovids and all artiodactyls together using nonparametric tests. Finally, we reanalysed the data using Maddison's (1990, Evolution, 44, 539-557) concentrated-changes tests and a consensus molecular and taxonomic phylogeny. We found evidence that snorting is both a warning signal to conspecifics and a pursuit-deterrent signal, lack of evidence that whistling alerts conspecifics and indications that foot stamping is a visual signal to warn group members. Evidence suggested that tail flagging was a signal to both conspecifics and predators, that bounding, leaping and stotting were used both as a signal and to clear obstacles and that prancing functioned similarly to foot stamping. Analyses of tail flicking, zigzagging and tacking were equivocal. We confirmed that inspection occurs in large groups, freezing enhances crypticity, and species seeking refuge in cliffs tend to be small. Entering water and attacks on predators had few correlates. Finally, group living, a putative antipredator adaptation, was associated with large body size and species living in open habitats, confirming Jarman's (1974, Behaviour, 48, 215-267) classic hypothesis. Bunching and group attack apparently deter predators. Despite limitations, comparative and systematic analyses can bolster adaptive hypotheses and raise new functional explanations for antipredator behaviour patterns in general.     

Percussive technology in human evolution: an introduction to a comparative approach in fossil and living primates

Percussive technology is part of the behavioural suite of several fossil and living primates. Stone Age ancestors used lithic artefacts in pounding activities, which could have been most important in the earliest stages of stone working. This has relevant evolutionary implications, as other primates such as chimpanzees and some monkeys use stone hammer-and-anvil combinations to crack hard-shelled foodstuffs. Parallels between primate percussive technologies and early archaeological sites need to be further explored in order to assess the emergence of technological behaviour in our evolutionary line, and firmly establish bridges between Primatology and Archaeology. What are the anatomical, cognitive and ecological constraints of percussive technology? How common are percussive activities in the Stone Age and among living primates? What is their functional significance? How similar are archaeological percussive tools and those made by non-human primates? This issue of Phil. Trans. addresses some of these questions by presenting case studies with a wide chronological, geographical and disciplinary coverage. The studies presented here cover studies of Brazilian capuchins, captive chimpanzees and chimpanzees in the wild, research on the use of percussive technology among modern humans and recent hunter–gatherers in Australia, the Near East and Europe, and archaeological examples of this behaviour from a million years ago to the Holocene. In summary, the breadth and depth of research compiled here should make this issue of Philosophical Transactions of the Royal Society B, a landmark step forward towards a better understanding of percussive technology, a unique behaviour shared by some modern and fossil primates.     

Chronobiologische Untersuchungen zur Raum-Zeit-Nutzung bei einem Orang-Utan-Paar im Zoo Osnabrück

Research about influences of natural and artificial environmental influences to animal behaviour is essential for the improvement of animal welfare in zoos and can be of importance for the conservation of free living animal populations. In literature on Orang-Utans (Pongo spec.), the biggest and heaviest of arboreal mammals, a connection between solar altitude and circadian rhythm was found. Activity during the waking hours was additionally influenced by weather, food supply, intra- and interspecific influences. Sunset marked the end of daily activity and the animals showed their anticipation among other things in the daily construction of tree nests.An examination of artificial influences, Orang-Utans in everyday zoo life are exposed to, is starting point for the present study. Further intentions were to record the activity patterns of two adult Zoo-Orang-Utans from evening to morning and gather information about nest building and the dominance situation between the two animals. During six weeks the Orang-Utan couple Buschi and Astrid (1.1) in the Zoo of Osnabrück was observed in the indoor enclosures every day from evening to morning via a video surveillance system (hours of observation: 623.5 h (Buschi, male); 236.5 h (Astrid, female)).The activity profiles of Buschi and Astrid fit into the results of field studies concerning chronobiological organisation and activity pattern. In the afternoon both animals were quite active and fed, afterwards they constructed their nests and laid down on them. The present observation leads to the conclusion that both, sunlight as well as the artificial lights, are able to influence their behaviour as so-called zeitgebers. Every night Buschi's sleep was interrupted several times by short active phases, in which he scratched himself extensively and adjusted his nest. Until this observation no comparable data concerning comfort activity by night in field and zoo situations was available.Nest building behaviour similar to free living Orang-Utans has been shown by Buschi and Astrid as well, changes being dependant on available material and the lack of necessity for safety and stability. The behaviour of Buschi taking nest parts from Astrid, suggests dominance between the mates and the nest as a reason for competition.