On the Size and Flight Diversity of Giant Pterosaurs, the Use of Birds as Pterosaur Analogues and Comments on Pterosaur Flightlessness

The size and flight mechanics of giant pterosaurs have received considerable research interest for the last century but are confused by conflicting interpretations of pterosaur biology and flight capabilities. Avian biomechanical parameters have often been applied to pterosaurs in such research but, due to considerable differences in avian and pterosaur anatomy, have lead to systematic errors interpreting pterosaur flight mechanics. Such assumptions have lead to assertions that giant pterosaurs were extremely lightweight to facilitate flight or, if more realistic masses are assumed, were flightless. Reappraisal of the proportions, scaling and morphology of giant pterosaur fossils suggests that bird and pterosaur wing structure, gross anatomy and launch kinematics are too different to be considered mechanically interchangeable. Conclusions assuming such interchangeability—including those indicating that giant pterosaurs were flightless—are found to be based on inaccurate and poorly supported assumptions of structural scaling and launch kinematics. Pterosaur bone strength and flap-gliding performance demonstrate that giant pterosaur anatomy was capable of generating sufficient lift and thrust for powered flight as well as resisting flight loading stresses. The retention of flight characteristics across giant pterosaur skeletons and their considerable robustness compared to similarly-massed terrestrial animals suggest that giant pterosaurs were not flightless. Moreover, the term ‘giant pterosaur’ includes at least two radically different forms with very distinct palaeoecological signatures and, accordingly, all but the most basic sweeping conclusions about giant pterosaur flight should be treated with caution. Reappraisal of giant pterosaur material also reveals that the size of the largest pterosaurs, previously suggested to have wingspans up to 13 m and masses up to 544 kg, have been overestimated. Scaling of fragmentary giant pterosaur remains have been misled by distorted fossils or used inappropriate scaling techniques, indicating that 10–11 m wingspans and masses of 200–250 kg are the most reliable upper estimates of known pterosaur size

Bone histology provides insights into the life history mechanisms underlying dwarfing in hipparionins

Size shifts may be a by-product of alterations in life history traits driven by natural selection. Although this approach has been proposed for islands, it has not yet been explored in continental faunas. The trends towards size decrease experienced by some hipparionins constitute a good case study for the application of a life history framework to understand the size shifts on the continent. Here, we analysed bone microstructure to reconstruct the growth of some different-sized hipparionins from Greece and Spain. The two dwarfed lineages studied show different growth strategies. The Greek hipparions ceased growth early at a small size thus advancing maturity, whilst the slower-growing Spanish hipparion matured later at a small size. Based on predictive life history models, we suggest that high adult mortality was the likely selective force behind early maturity and associated size decrease in the Greek lineage. Conversely, we infer that resource limitation accompanied by high juvenile mortality triggered decrease in growth rate and a relative late maturity in the Spanish lineage. Our results provide evidence that different selective pressures can precipitate different changes in life history that lead to similar size shifts

First report of Triassic vertebrate assemblages from the Villány Hills (Southern Hungary)

Abstract Remains of Triassic vertebrates discovered in the Villány Hills (SW Hungary) are described here. After the well-documented Late Cretaceous Iharkút locality, this material represents the second systematically collected assemblage of Mesozoic vertebrates from Hungary. Fossils were collected from both the classical abandoned road-cut at Templom Hill (Templom-hegy) and a newly discovered site at a construction zone located 200 meters west of the road-cut. Macrofossils of the construction site are mainly isolated bones and teeth of nothosaurs from the Templomhegy Dolomite, including a fragmentary mandible referred to as Nothosaurus sp. and placodont teeth tentatively assigned here to cf. Cyamodus sp. Affinities of these fossils suggest a Middle Triassic (Ladinian) age of these shallow marine deposits. New palynological data prove for the first time a Late Triassic (Carnian) age of the lower part of the Mészhegy Sandstone Formation. Vertebrate remains discovered in this formation clearly represent a typical Late Triassic shallow-marine fauna including both chondrichthyan (Lissodus, Palaeobates, Hybodus) and osteichthyan (cf. Saurichthys, ?Sphaerodus sp.) fish fossils. The presence of reworked nothosaur and placodont tooth fragments as well as of possible archosauriform teeth, suggest an increase of terrestrial influence and the erosion of underlying Triassic deposits during the Late Triassic. A belemnite rostrum collected from the lowermost beds of the Somssichhegy Limestone Formation proves that this Lower Jurassic (Pliensbachian) layer was deposited in a marine environment. Most of the vertebrate remains (nothosaurs, placodonts, hybodont shark teeth, perhaps Palaeobates, Lissodus) recovered from these beds are also reworked Triassic elements strongly supporting an erosive, nearshore depositional environment