Terrestrial Lifestyle Research Articles

A new archosauromorph from South America provides insights on the early diversification of tanystropheids.

After the Permo-Triassic mass extinction, the archosauromorph fossil record is comparatively abundant and ecologically diverse. Among early archosauromorphs, tanystropheids gained considerable attention due to the presence of extreme skeletal adaptations in response to sometimes overspecialized lifestyles. The origin and early radiation of Tanystropheidae, however, remains elusive. Here, a new Early Triassic archosauromorph is described and phylogenetically recovered as the sister-taxon of Tanystropheidae. The new specimen, considered a new genus and species, comprises a complete posterior limb articulated with pelvic elements. It was recovered from the Sanga do Cabral Formation (Sanga do Cabral Supersequence, Lower Triassic of the Paraná Basin, Southern Brazil), which has already yielded a typical Early Triassic vertebrate assemblage of temnospondyls, procolophonoids, and scarce archosauromorph remains. This new taxon provides insights on the early diversification of tanystropheids and represents further evidence for a premature wide geographical distribution of this clade. The morphology of the new specimen is consistent with a terrestrial lifestyle, suggesting that this condition was plesiomorphic for Tanystropheidae.

Developmental and sexual divergence in the olfactory system of the marine insect Clunio marinus

An animal’s fitness strongly depends on successful feeding, avoidance of predators and reproduction. All of these behaviours commonly involve chemosensation. As a consequence, when species’ ecological niches and life histories differ, their chemosensory abilities need to be adapted accordingly. The intertidal insect Clunio marinus (Diptera: Chironomidae) has tuned its olfactory system to two highly divergent niches. The long-lived larvae forage in a marine environment. During the few hours of terrestrial adult life, males have to find the female pupae floating on the water surface, free the cryptic females from their pupal skin, copulate and carry the females to the oviposition sites. In order to explore the possibility for divergent olfactory adaptations within the same species, we investigated the chemosensory system of C. marinus larvae, adult males and adult females at the morphological and molecular level. The larvae have a well-developed olfactory system, but olfactory gene expression only partially overlaps with that of adults, likely reflecting their marine vs. terrestrial lifestyles. The olfactory system of the short-lived adults is simple, displaying no glomeruli in the antennal lobes. There is strong sexual dimorphism, the female olfactory system being particularly reduced in terms of number of antennal annuli and sensilla, olfactory brain centre size and gene expression. We found hints for a pheromone detection system in males, including large trichoid sensilla and expression of specific olfactory receptors and odorant binding proteins. Taken together, this makes C. marinus an excellent model to study within-species evolution and adaptation of chemosensory systems.

Is variation in tail vertebral morphology linked to habitat use in chameleons?

Chameleons (Chamaeleonidae) are known for their arboreal lifestyle, in which they make use of their prehensile tail. Yet, some species have a more terrestrial lifestyle, such as Brookesia and Rieppeleon species, as well as some chameleons of the genera Chamaeleo and Bradypodion. The main goal of this study was to identify the key anatomical features of the tail vertebral morphology associated with prehensile capacity. Both interspecific and intra-individual variation in skeletal tail morphology was investigated. For this, a 3D-shape analysis was performed on vertebral morphology using μCT-images of different species of prehensile and nonprehensile tailed chameleons. A difference in overall tail size and caudal vertebral morphology does exist between prehensile and nonprehensile taxa. Nonprehensile tailed species have a shorter tail with fewer vertebrae, a generally shorter neural spine and shorter transverse processes that are positioned more anteriorly (with respect to the vertebral center). The longer tails of prehensile species have more vertebrae as well as an increased length of the processes, likely providing a greater area for muscle attachment. At the intra-individual level, regional variation is observed with more robust proximal tail vertebrae having longer processes. The distal part has relatively longer vertebrae with shorter processes. Although longer, the small size and high number of the distal vertebrae allows the tail to coil around perches.

Overlooked diversity with terrestrial lifestyle in the predominantly freshwater and snow phylogroup Chloromonadinia (Volvocales, Chlorophyceae)

ABSTRACTThe phylogroup Chloromonadinia (Volvocales, Chlorophyceae) encompasses ecologically versatile green microalgae with a predominantly freshwater and snow lifestyle. Although a few species have been described from soils, the evolutionary history of terrestrial volvocalean flagellates is poorly known due to undersampling. Here we provide new insights into the phylogenetic position of terrestrial flagellates within the Chloromonadinia and investigate six unresolved strains from terrestrial and freshwater habitats in both hemispheres. The terrestrial strains differed in cell morphology, ultrastructure and lifestyle from the freshwater ones, therefore, we expected them to represent distinct evolutionary lineages (species or genera). While the terrestrial strain SAG 25.87 (Chloromonas gracillima comb. & stat. nov.) from Czech mountains clustered within the psychrotolerant core Chloromonas clade, the other terrestrial strains formed a phylogenetically separate lineage which we proposed as Ostravamonas gen. nov. The new genus differs from other closely related Chloromonadinia genera by chloroplast, eyespot, papilla and cell-wall morphology. Two terrestrial strains, CAUP G 1401 (coal spoil heap; Czechia) and SAG 12.72 (acidic soil; New Zealand), were designated as Ostravamonas chlorostellata comb. nov. and represent the first Chloromonadinia microalgae discovered in acidic terrestrial environments. Closely related ‘Chlamydomonas’ strains SAG 75.81 (ditch; France) and CCAP 11/108 (origin unknown) were reassigned to Ostravamonas meslinii comb. nov. and Ostravamonas tenuiincisa sp. nov., respectively. Our study shows that the traditional ‘Chlamydomonas’ still hides an overlooked diversity of species with a terrestrial lifestyle that are nested phylogenetically within the Chloromonadinia phylogroup.

Insights into the 400 million-year-old eyes of giant sea scorpions (Eurypterida) suggest the structure of Palaeozoic compound eyes

Sea scorpions (Eurypterida, Chelicerata) of the Lower Devonian (~400 Mya) lived as large, aquatic predators. The structure of modern chelicerate eyes is very different from that of mandibulate compound eyes [Mandibulata: Crustacea and Tracheata (Hexapoda, such as insects, and Myriapoda)]. Here we show that the visual system of Lower Devonian (~400 Mya) eurypterids closely matches that of xiphosurans (Xiphosura, Chelicerata). Modern representatives of this group, the horseshoe crabs (Limulidae), have cuticular lens cylinders and usually also an eccentric cell in their sensory apparatus. This strongly suggests that the xiphosuran/eurypterid compound eye is a plesiomorphic structure with respect to the Chelicerata, and probably ancestral to that of Euchelicerata, including Eurypterida, Arachnida and Xiphosura. This is supported by the fact that some Palaeozoic scorpions also possessed compound eyes similar to those of eurypterids. Accordingly, edge enhancement (lateral inhibition), organised by the eccentric cell, most useful in scattered light-conditions, may be a very old mechanism, while the single-lens system of arachnids is possibly an adaptation to a terrestrial life-style.

Oxygen isotopes and ecological inferences of Permian (Guadalupian) tetrapods from the main Karoo Basin of South Africa

The Abrahamskraal Formation of South Africa has a diverse middle Permian (Guadalupian) fossil tetrapod fauna comprising largely basal therapsids and pareiasaurian parareptiles. Knowledge on the paleoecology of these animals is limited because inferences of many ecological traits in mid-Permian tetrapods are based on deductions from morphology. While it is widely accepted that the rhinesuchid amphibians were aquatic, the ecological lifestyle of pareiasaurs and dinocephalian therapsids remains uncertain. To investigate the ecological roles of different middle Permian tetrapod taxa we studied stable oxygen isotope compositions of phosphate from teeth and bones as a proxy for water dependence. Our results reveal similar δ18Op values for pareiasaurs, the dinocephalian Anteosaurus, and therocephalians, with a range of values similar to those of extant terrestrial species. The consistent δ18Op values for pareiasaurs strengthen our interpretation of a terrestrial lifestyle for these parareptiles, but the lower Anteosaurus δ18Op values might question the interpretation and a larger sample size may result in a more conclusive outcome. These results conclude the debate on the ecology of middle Permian pareiasaurs. A terrestrial lifestyle is applicable only to the middle Permian species and a different lifestyle is possible for pareiasaurs species that lived after the end Capitanian extinction.

Paw Morphology in the Domestic Guinea Pig (Cavia porcellus) and Brown Rat (Rattus norvegicus).

Mammals have adapted to different habitats, food types, and modes of locomotion, which are reflected in a diverse range of paw morphologies. While the behavior of rats and guinea pigs is well defined, especially in terms of their locomotor and foraging behaviors, the anatomy of their foot pads has not yet been explored and compared. This study investigated adaptations in paw morphology in the domestic guinea pig (Cavia porcellus) and the brown rat (Rattus norvegicus). We predicted that rat paws would display adaptations associated with paw dexterity for handling prey items and climbing, whereas guinea pig paws would support mechanical pressure absorption for a herbivorous, sedentary, and terrestrial lifestyle. Using histology techniques and scanning electron microscope, we show that rat paws have many small, deformable pads that are relatively spaced out to enable movement. The pads are clustered toward the anterior of the foot, which coincides with where the most force occurs during locomotion, as rats walk on their toes and toward the front of their paw. Guinea pigs had fewer and larger pads and the posterior pad of the forepaw was textured and contained cartilage, which may act to reduce friction and compression during standing and locomotion. We suggest that differences in paw morphology in rat and guinea pig are associated with loading during locomotion as well as paw mobility. Examining paw morphology and movement abilities in more species will give further insights in to the evolution of locomotor adaptations and paw dexterity in rodents. Anat Rec, 302:2300-2310, 2019. © 2019 American Association for Anatomy.

Crocodylomorph cranial shape evolution and its relationship with body size and ecology.

Crocodylomorpha, which includes living crocodylians and their extinct relatives, has a rich fossil record, extending back for more than 200 million years. Unlike modern semi-aquatic crocodylians, extinct crocodylomorphs exhibited more varied lifestyles, ranging from marine to fully terrestrial forms. This ecological diversity was mirrored by a remarkable morphological disparity, particularly in terms of cranial morphology, which seems to be closely associated with ecological roles in the group. Here, I use geometric morphometrics to comprehensively investigate cranial shape variation and disparity in Crocodylomorpha. I quantitatively assess the relationship between cranial shape and ecology (i.e. terrestrial, aquatic, and semi-aquatic lifestyles), as well as possible allometric shape changes. I also characterize patterns of cranial shape evolution and identify regime shifts. I found a strong link between shape and size, and a significant influence of ecology on the observed shape variation. Terrestrial taxa, particularly notosuchians, have significantly higher disparity, and shifts to more longirostrine regimes are associated with large-bodied aquatic or semi-aquatic species. This demonstrates an intricate relationship between cranial shape, body size and lifestyle in crocodylomorph evolutionary history. Additionally, disparity-through-time analyses were highly sensitive to different phylogenetic hypotheses, suggesting the description of overall patterns among distinct trees. For crocodylomorphs, most results agree in an early peak during the Early Jurassic and another in the middle of the Cretaceous, followed by nearly continuous decline until today. Since only crown-group members survived through the Cenozoic, this decrease in disparity was likely the result of habitat loss, which narrowed down the range of crocodylomorph lifestyles.

Ecomorphological diversification of the Late Palaeozoic Palaeodictyopterida reveals different larval strategies and amphibious lifestyle in adults.

The Late Palaeozoic insect superorder Palaeodictyopterida exhibits a remarkable disparity of larval ecomorphotypes, enabling these animals to occupy diverse ecological niches. The widely accepted hypothesis presumed that their immature stages only occupied terrestrial habitats, although authors more than a century ago hypothesized they had specializations for amphibious or even aquatic life histories. Here, we show that different species had a disparity of semiaquatic or aquatic specializations in larvae and even the supposed retention of abdominal tracheal gills by some adults. While a majority of mature larvae in Palaeodictyoptera lack unambiguous lateral tracheal gills, some recently discovered early instars had terminal appendages with prominent lateral lamellae like in living damselflies, allowing support in locomotion along with respiratory function. These results demonstrate that some species of Palaeodictyopterida had aquatic or semiaquatic larvae during at least a brief period of their post-embryonic development. The retention of functional gills or gill sockets by adults indicates their amphibious lifestyle and habitats tightly connected with a water environment as is analogously known for some modern Ephemeroptera or Plecoptera. Our study refutes an entirely terrestrial lifestyle for all representatives of the early diverging pterygote group of Palaeodictyopterida, a greatly varied and diverse lineage which probably encompassed many different biologies and life histories.

Hypoxia causes woodlice (Porcellio scaber) to select lower temperatures and impairs their thermal performance and heat tolerance.

Environmental temperatures and oxygen availability are important for the balance between oxygen supply and demand. Terrestrial organisms are generally perceived to be less limited by access to oxygen than their aquatic counterparts. Nevertheless, even terrestrial environments can be deficient in oxygen, especially for organisms occurring in soil, litter, wood, rotten fruit or at high elevations. While isopods are the best adapted to a terrestrial lifestyle among crustaceans, many species, including woodlice, occupy environmental gradients of temperature and oxygen. To investigate whether mismatches between oxygen supply and demand can result in a loss of performance in a terrestrial organism, we studied the effects of atmospheric oxygen concentration on the thermal performance of the common rough woodlouse (Porcellio scaber). We compared the thermal preference, thermal sensitivity of running speed, and tolerance to extreme temperatures of woodlice exposed to one of two oxygen concentrations (21% - normoxia, 7% - hypoxia). Under hypoxia, P. scaber preferred microhabitats with temperatures that were on average 3°C lower than those preferred under normoxia. The running speed tended to reach its maximum at a lower temperature under hypoxia than under normoxia (25.13°C vs 28.87°C, respectively, although p was equal to 0.09), and normoxic woodlice ran approximately 1.5-fold faster than hypoxic woodlice at the point of maximum speed. Heat tolerance was significantly lower under hypoxia (38.9°C) than under normoxia (40.7°C), but there was no difference in cold tolerance (5.81°C under normoxia and 5.44°C under hypoxia). Overall, our results indicate that environmental gradients of temperature and oxygen may shape the physiological performance of terrestrial ectotherms, likely via their effects on the balance between oxygen supply and demand, which may have fitness consequences for these organisms in nature.

Small terrestrial crocodyliform from the Lower Cretaceous (late Aptian) of central Texas and its implications on the paleoecology of the Proctor Lake Dinosaur locality

ABSTRACTWithin the Twin Mountains Formation, the Proctor Lake dinosaur locality in central Texas is distinct from other Early Cretaceous localities by having an abundance of vertebrate fossils representing a low-diversity assemblage. However, it has yielded two small-bodied crocodyliforms, Wannchampsus kirpachi and Tarsomordeo winkleri, gen. et sp. nov. This new species is represented by a single partial skeleton with a complete dentary, trough-shaped mandibular symphysis, amphicoelous vertebrae, nearly square dorsal osteoderms, and gracile, elongated limbs. In addition, limb morphology indicates a parasagittal posture, an attribute for a terrestrial lifestyle that could have allowed T. winkleri to fill an ecological niche as an active predator of nesting dinosaurs and other small prey. A phylogenetic analysis places this new taxon within Eusuchia as a member of Paralligatoridae and the sister taxon to Paralligator major and Rugosuchus nonganensis, providing further evidence for the presence of this clade in North America. This new Proctor Lake crocodyliform expands the taxonomic diversity of the Early Cretaceous units of central Texas and provides additional insight into the paleoecology of the Proctor Lake dinosaur nesting site.

Triturus newts

Ben Wielstra introduces Eurasian newts of the genus Triturus.

Changes in ontogenetic patterns facilitate diversification in skull shape of Australian agamid lizards

BackgroundMorphological diversity among closely related animals can be the result of differing growth patterns. The Australian radiation of agamid lizards (Amphibolurinae) exhibits great ecological and morphological diversity, which they have achieved on a continent-wide scale, in a relatively short period of time (30 million years). Amphibolurines therefore make an ideal study group for examining ontogenetic allometry. We used two-dimensional landmark-based geometric morphometric methods to characterise the postnatal growth patterns in cranial shape of 18 species of amphibolurine lizards and investigate the associations between cranial morphology, and life habit and phylogeny.ResultsFor most amphibolurine species, juveniles share a similar cranial phenotype, but by adulthood crania are more disparate in shape and occupy different sub-spaces of the total shape space. To achieve this disparity, crania do not follow a common post-natal growth pattern; there are differences among species in both the direction and magnitude of change in morphospace. We found that these growth patterns among the amphibolurines are significantly associated with ecological life habits. The clade Ctenophorus includes species that undergo small magnitudes of shape change during growth. They have dorsoventrally deep, blunt-snouted skulls (associated with terrestrial lifestyles), and also dorsoventrally shallow skulls (associated with saxicolous lifestyles). The sister clade to Ctenophorus, which includes the bearded dragon (Pogona), frill-neck lizard (Chlamydosaurus), and long-nosed dragon (Gowidon), exhibit broad and robust post-orbital regions and differing snout lengths (mainly associated with scansorial lifestyles).ConclusionsAustralian agamids show great variability in the timing of development and divergence of growth trajectories which results in a diversity of adult cranial shapes. Phylogenetic signal in cranial morphology appears to be largely overwritten by signals that reflect life habit. This knowledge about growth patterns and skull shape diversity in agamid lizards will be valuable for placing phylogenetic, functional and ecological studies in a morphological context.

Size dependence of offspring production in isopods: a synthesis.

In isopods, parental care takes the form of offspring brooding in marsupial pouches. Marsupial brooding was an important step towards the origin of terrestrial lifestyles among isopods, but its potential role in shaping isopod life histories remains unknown. It is here considered that marsupial brooding imposes costs and creates a temporary association between the survival of mothers and that of their offspring. Integrating findings from different life history models, we predicted that the effects of marsupial brooding set selective conditions for the continuation of growth after maturation, which leads to indeterminate growth, and the production of larger offspring by larger females. Based on this perspective, a study on the size dependence of offspring production in the woodlouse Porcellioscaber was performed and the generality of the results was tested by reviewing the literature on offspring production in other isopods. In P.scaber and almost all the other studied isopods, clutch size is positively related to female size. Such dependence is a necessary pre-condition for the evolution of indeterminate growth. The body mass of P.scaber differed six-fold between the largest and smallest brooding females, indicating a high potential for post-maturation growth. Our review showed that offspring size is a rarely studied trait in isopods and that it correlates negatively with offspring number but positively with female size in nearly half of the studied species. Our study of P.scaber revealed similar patterns, but the positive effect of female size on offspring size occurred only in smaller broods, and the negative relation between clutch size and offspring size occurred only in larger females. We conclude that the intraspecific patterns of offspring production in isopods agree with theoretical predictions regarding the role of offspring brooding in shaping the adaptive patterns of female investment in growth, reproduction, and the parental care provided to individual offspring.

Massive Expansion of Bitter Taste Receptors in Blind Cavefish, Astyanax mexicanus.

A sensory deficit both at the individual and at the species level can be compensated by increased acuity in other senses. The loss of vision in blind cavefish, Astyanax mexicanus, appears to be partially counterbalanced by enhanced chemosensory perception. Whether such improvement also involves adaptive changes in chemosensory receptor repertoires was unknown. The typical bitter taste receptor repertoire of teleost fish is reported as 3-5 genes, much smaller than that of many terrestrial species. Interestingly, several fish species, for example, mudskipper, have evolved a terrestrial lifestyle, but again it was unknown, whether this change in habitat is reflected in the size of gustatory receptor repertoires. We have searched the genomes of 15 fish species and performed a thorough phylogenetic analysis to delineate their bitter taste receptor repertoires. We report no adaptation for 4 mudskipper species, which exhibit 3-4 bitter taste receptor genes, and thus a typical teleost repertoire, shaped by few gene losses and minor gene duplications from an ancestral repertoire of 4 genes. However, and in sharp contrast to all other teleost fish species analyzed, blind cavefish possess more than 20 intact bitter taste receptors and several pseudogenes, rivaling the complexity of the human bitter taste receptor repertoire. The gene duplications giving rise to the current cavefish bitter taste receptor repertoire appear to have occurred well before the loss of vision, consistent with this increase in repertoire size constituting a preadaptive trait that conceivably could compensate to some extent for the lack of visual cues.

The enigmatic palaeoecology and palaeobiogeography of the giant, horned, fossil turtles of Australasia: a review and reanalysis of the data

The distribution pattern of the bizarre Australasian giant, horned, fossil turtles of the clade Meiolaniidae has puzzled biogeographers since their discovery late in the nineteenth century. While their distribution suggests a Gondwanan origin, the lack of fossil evidence from key times and places has inhibited a better understanding of their dispersal pathways to Australia and the south-west Pacific islands in which their fossils have been found. Much palaeoecological speculation related to their dispersal capabilities, ranging from purely terrestrial to freshwater, estuarine, and saltwater lifestyles, has been proposed to explain their enigmatic presence across a wide swath of Oceania. Various lines of fossil, anatomical and ecological evidence now strongly suggest a highly terrestrial lifestyle, and we believe these traits, reinforced by an abundance of marine predators and ever-widening saltwater gaps between land areas during the Late Mesozoic and Tertiary, minimise the importance of saltwater dispersal as an explanation for the observed meiolaniid distribution pattern. Here we propose that the fragmentation of Gondwana provided the main dispersal vehicle for the meiolaniids and that land connections were also used to access suitable habitats and expand their range. The recently recognised continent of Zealandia, along with Australia, South America, and probably Antarctica, transported all known meiolaniid turtles to their present locations. However, ice cover on Antarctica, and the nearly total submergence of Zealandia in essence preclude the current likelihood of fossil discovery in these critical locations. The islands of New Caledonia, Tiga (in the Loyalty Islands), Walpole, and Lord Howe served as refugia for Zealandia meiolaniids as the continent submerged.

Lumbering on land costs elephant seals dear

In the transition from a terrestrial lifestyle to an existence beneath the waves, elephant seals (Mirounga angustirostris) are pretty far along. With a streamlined body, blubber for insulation and the ability to carry extensive oxygen supplies for lengthy dives, elephant seals are as well equipped as many whales and dolphins. However, when the colossal mammals haul themselves onto gently shelving beaches to mate and give birth, the tables turn against them. ‘There is an energetic consequence to becoming aquatic; it becomes easier to swim but harder to walk’, says Frank Fish from West Chester University, USA; the question was, how hard? Having previously filmed and analysed the movements of relatively diminutive harbour and grey seals, which are about one-tenth the size of elephant seals, Fish and graduate student Kelsey Tennett teamed up with Dan Costa from the University of California, Santa Cruz, USA, to get up close and personal with the gigantic mammals in California's Año Nuevo State Park.‘It was in January, the time when males are trying to mate with females and the females are pupping’, says Fish, recalling how the massive seals weren't too bothered by the scientists and their cameras; they had other things on their minds. Setting up a camera about 6–12 m from a seal that was taking a brief rest after dragging itself across the sand, the team waited until the animal showed signs of moving again before filming. ‘We could tell when the animal was about to move because it would start to rise up with its head and chest’, says Fish. Having filmed the seals humping along before collapsing on the sand, Fish then dashed into shot behind the animal with a 0.5 m long stick, so that Tennett could calculate the size of the animal and measure its movements back in the lab.Analysing the seals’ cumbersome manoeuvres, Fish realised that each elephant seal initially reared its head and chest up before allowing its torso to slump forward to initiate a charge. As its chest crashed down, the animal then flexed its body like an inchworm to shift its hindflippers forward, allowing it to push down on the sand with its pelvis as the wave of movement travelled forward along its body. This then allowed it to thrust its chest, head and neck back off the sand, using its foreflippers like crutches, ready to lurch forward once again and initiate the next cycle. Sometimes the animals could only manage a few ‘strides’ covering 5–10 m before grinding to a halt, while some males maintained speeds of up to 2.5 m s−1 over 30–40 m in pursuit of a female or rival.But what did all of this mean for the giant animals’ efficiency as they thundered across the sand – were they more or less efficient than smaller seals? Fish and Tennett teamed up with physicist Anthony Nicastro, also from West Chester University, to answer the question. They calculated that the elephant seals were using approximately 40 times more energy at any instant to shuffle along at speeds of about 2 m s−1 (which equates to 0.6 times their body length), than smaller grey seals scuffling about at a similar speed – relative to their body size – of 1.3 m s−1.‘Bigger is not always better, particularly when you are highly adapted for swimming rather than terrestrial locomotion’, says Fish, adding that elephant seals are paying an energetic penalty for their aquatic lifestyle. And, having scrutinised the largest seals in the northern hemisphere, Fish is keen to visit their even more gigantic relatives in the south. ‘I want to see if they [southern elephant seals] have reached a limit in how big a seal can be’, he says.

Ornamentation of dermal bones of Metoposaurus krasiejowensis and its ecological implications.

BackgroundAmphibians are animals strongly dependent on environmental conditions, like temperature, water accessibility, and the trophic state of the reservoirs. Thus, they can be used in modern palaeoenvironmental analysis, reflecting ecological condition of the biotope.MethodsTo analyse the observed diversity in the temnospondyl Metoposaurus krasiejowensis from Late Triassic deposits in Krasiejów (Opole Voivodeship, Poland), the characteristics of the ornamentation (such as grooves, ridges, tubercules) of 25 clavicles and 13 skulls were observed on macro- and microscales, including the use of a scanning electron microscope for high magnification. The different ornamentation patterns found in these bones have been used for taxonomical and ecological studies of inter- vs. intraspecific variation.ResultsTwo distinct types of ornamentation (fine, regular and sparse, or coarse, irregular and dense) were found, indicating either taxonomical, ecological, individual, or ontogenetic variation, or sexual dimorphism in M. krasiejowensis.DiscussionAnalogies with modern Anura and Urodela, along to previous studies on temnospondyls amphibians and the geology of the Krasiejów site suggest that the differences found are rather intraspecific and may suggest ecological adaptations. Sexual dimorphism and ontogeny cannot be undoubtedly excluded, but ecological variation between populations of different environments or facultative neoteny (paedomorphism) in part of the population (with types of ornamentations being adaptations to a more aquatic or a more terrestrial lifestyle) are the most plausible explanations.

Novel data on aetosaur (Archosauria, Pseudosuchia) osteoderm microanatomy and histology: palaeobiological implications

AbstractOne of the most striking features of aetosaurs is the possession of an extensive bony armour composed of dorsal, ventral and appendicular osteoderms. With the purpose of establishing the main histological changes during ontogeny and the degree of histological variation within the armour, we analysed the bone histology of dorsal (paramedian and lateral), ventral and appendicular osteoderms from different taxa from the Late Triassic of South America, including Aetosauroides scagliai, Aetobarbakinoides brasiliensis and Neoaetosauroides engaeus. Histological data support an intramembranous origin for osteoderms. Nevertheless, evidence for metaplastic ossification (i.e. structural fibres) at advanced ontogenetic stages, in at least some elements, is also present. A variant type of parallel fibred bone, which we have named ‘crossed parallel fibred bone’, is characterized for aetosaurs. In this pseudosuchian group, osteoderms exhibit very important microstructural changes during ontogeny, which can be useful for determining ontogenetic stages from isolated elements. Histological data suggest a relatively early onset of sexual maturity among aetosaurs. Microanatomical analysis from different taxa reveal that having high values of compactness is the plesiomorphic condition for Aetosauria. The notably increased compactness of the osteoderms does not appear to be related to size, ontogeny, sex or reproductive status of the individuals. Although a high degree of compactness of osteoderms and other bones has been considered as evidence for an aquatic lifestyle in vertebrates, such an inference contradicts the current concept of a fully terrestrial lifestyle in aetosaurs.

Reinterpretation of a previously described Jehol bird clarifies early trophic evolution in the Ornithuromorpha.

STM35-3 from the Yixian Formation is the only Early Cretaceous ornithuromorph preserving direct evidence of granivory. The crop contains numerous seeds and the preservation of gastroliths presumably within the ventriculus indicates this diet was paired with the presence of a gastric mill as in living granivorous birds. STM35-3 was originally referred to Hongshanornis longicresta, member of a diverse clade of small, basal ornithuromorphs with elongate hindlimbs known as the Hongshanornithidae. Hindlimb proportions suggest that hongshanornithids were wading birds, an ecological inference somewhat in conflict with direct evidence suggesting Hongshanornis fed on seeds. However, close inspection of STM35-3 reveals that the specimen represents a new species not closely related to hongshanornithids, distinguished by large forelimbs that exceed the length of the hindlimbs, robust and narrow coracoids, and a delicate edentulous rostrum. By contrast, all hongshanornithids have hindlimbs that far exceed the length of the forelimbs, coracoids with wide sternal margins, and small teeth throughout the upper and lower jaws. Reinterpretation of this new taxon, Eogranivora edentulata gen. et sp. nov, helps to clarify trophic driven patterns of tooth loss within the Ornithuromorpha. Apparent loss of the hallux may represent the first such occurrence in a Mesozoic bird and suggests a highly terrestrial lifestyle.