Giant Pterosaurs Research Articles

Small, immature pterosaurs from the Cretaceous of Africa: implications for taphonomic bias and palaeocommunity structure in flying reptiles

Pterosaurs reached only modest sizes in the Triassic-Jurassic. By contrast, the Cretaceous saw a trend toward large to giant size (2 m to >6 m wingspans), and while small-medium (<1 m–2 m wingspans) sized forms are known from the Lower Cretaceous they are rare in the Upper Cretaceous. This pattern has been ascribed to the appearance of birds in the mid-Mesozoic, and their displacement of pterosaurs from niches previously occupied by small-medium sized forms. Here we show how new finds of small-very small pterosaurs (<1 m wingspans) from the mid-Cretaceous Kem Kem Group of Morocco point to several sampling biases of the data upon which these patterns are founded. Evidence for the size range of these pterosaurs strongly correlates with sample-size: as the sample increased (from <100 to >400 specimens) both very small and giant forms have been discovered. Histological analysis suggests that very small/small morphs are immature individuals rather than species in which adults were small-bodied. This new data shows that size distribution patterns based on all available specimens differ markedly from those based on a much more restricted sub-set of named taxa. Critically, this analysis reveals that pterosaur size ranges in the Cretaceous do not reflect a switch to large and giant size, but an extension of the size range from very small through to giant forms. Cretaceous niches previously occupied by small pterosaurs in the Triassic and Jurassic were increasingly occupied not by birds but by early ontogenetic stages of large and giant pterosaurs.

A review and reappraisal of the specific gravities of present and past multicellular organisms, with an emphasis on tetrapods.

The density, or specific gravity (SG), of organisms has numerous important implications for their form, function, ecology, and other facets of beings living and dead, and it is especially necessary to apply SG values that are as accurate as practical when estimating their masses which is itself a critical aspect of living things. Yet a comprehensive review and analysis of this notable subject of anatomy has never been conducted and published. This is such an effort, being as extensive as possible with the data on hand, bolstered by some additional observations, and new work focusing on extinct animals who densities are least unknown: pterosaurs and dinosaurs with extensive pneumatic complexes, including the most sophisticated effort to date for a sauropod. Often difficult to determine even via direct observation, techniques for obtaining the best possible SG data are explained and utilized, including observations of floating animals. Neutral specific gravity (NSG) is proposed as the most important value for tetrapods with respiratory tracts of fluctuating volume. SGs of organisms range from 0.08 to 2.6, plant tissues from 0.08 to 1.39, and vertebrates from about 0.75 (some giant pterosaurs) to 1.2 (those with heavy armor and/or skeletons). Tetrapod NSGs tend to be somewhat higher than widely thought, especially those theropod and sauropod dinosaurs and pterosaurs with air-sacs because respiratory system volume is usually measured at maximum inhalation in birds. Also discussed is evidence that the ratio of the mass of skeletons relative to total body mass has not been properly assayed in the past.

Discovery of the largest pterosaur from South America

A giant humerus (450 mm total length) belonging to one of the largest pterosaur recorded in South America is described. The specimen (UNCUYO-LD 350) was discovered in the Upper Cretaceous (upper Coniacian – lower Santonian) Plottier Formation of the Mendoza Province, northern Neuquén Basin, Argentina. It was found associated with a smaller pterosaur specimen represented by around thirty postcranial bones. The specimen is assigned to Tapejaroidea and show characters of both Tapejaridae and Azhdarchidae. Based on comparisions with other Azdharchidae species, a wingspan of 9.1 m is estimated for UNCUYO-LD 350, showing that giant pterosaurs were present in South America during the Upper Cretaceous.

Breathing in a box: Constraints on lung ventilation in giant pterosaurs

ABSTRACTPterosaurs were the first vertebrates to achieve active flight, with some derived forms reaching enormous size. Accumulating fossil evidence confirms earlier indications that selection for large size in these flying forms resulted in a light, yet strong skeleton characterized by fusion of many bones of the trunk. However, this process also added mechanical constraints on the mobility of the thorax of large pterosaurs that likely limited the options available for lung ventilation. We present an alternative hypothesis to recent suggestions of an avian‐like mechanism of costosternal pumping as the primary means of aspiration. An analysis of the joints among the vertebrae, ribs, sternum, and pectoral girdle of large pterosaurs indicates limited mobility of the ribcage and sternum. Comparisons with modes of lung ventilation in extant amniotes suggests that the stiffened thorax, coupled with mobile gastralia and prepubic bones, may be most consistent with an extracostal mechanism for lung ventilation in large pterodactyloids, perhaps similar to a crocodile‐like visceral displacement system Anat Rec, 297:2233–2253, 2014. © 2013 Wiley Periodicals, Inc.

Giant pterosaurs and the limits of animal flight (13.3)

Pterosaurs appear to have had a particular propensity for the evolution of large size compared with other flying animals: at least eight genera of pterosaurs included species with wingspans in excess of 4 meters. I present a launch constraints model that accurately predicts size trends in pterosaurs. Azhdarchid pterosaurs evolved a suite of traits associated with improved terrestrial ability and rapid launch, including an expanded and curved deltopectoral crest, expanded coracoid flange, elongate metacarpal IV, and a reinforced fourth metacarpal‐phalangeal joint. This pattern explains why the largest pterosaurs were members of the Azhdarchidae. Most other “giant” pterosaurs were marine, and may have been more constrained in size than azhdarchids as a result of water launching requirements. Large marine pterosaurs, such as anhanguerids, tended to possess an expanded scapula, reinforced scapular‐notarial joint, warped deltopectoral crest, exceptionally broad wing pivot joint, expanded posterior brachial musculature, and reduced hind limbs. These traits are predicted as specializations to water launching. Pneumaticity, forelimb hypertrophy, and quadrupedal launch, combined with selection for low energy loitering and/or extended range, explains the repeated evolution of large size in pterosaurs.

Breathing in a box: Constraints on lung ventilation in giant pterosaurs

Pterosaurs were the first vertebrates to achieve active flight, with some derived forms reaching enormous size. Accumulating fossil evidence confirms earlier indications that selection for large size in these flying forms resulted in a light, yet strong skeleton characterized by fusion of many bones of the trunk. However, this process also added mechanical constraints on the mobility of the thorax of large pterosaurs that likely limited the options available for lung ventilation. We present an alternative hypothesis to recent suggestions of an avian-like mechanism of costosternal pumping as the primary means of aspiration. An analysis of the joints among the vertebrae, ribs, sternum, and pectoral girdle of large pterosaurs indicates limited mobility of the ribcage and sternum. Comparisons with modes of lung ventilation in extant amniotes suggests that the stiffened thorax, coupled with mobile gastralia and prepubic bones, may be most consistent with an extracostal mechanism for lung ventilation in large pterodactyloids, perhaps similar to a crocodile-like visceral displacement system.

Gargantuavis philoinos: Giant bird or giant pterosaur?

Gargantuavis philoinos was described as a giant terrestrial bird on the basis of various postcranial elements (synsacrum and pelvis, femur) from Late Cretaceous (Campanian-Maastrichtian) localities in Southern France. It has recently been suggested that these remains in fact belong to giant pterosaurs. A detailed comparison between bones referred to Gargantuavis and the corresponding skeletal elements of pterosaurs reveals considerable differences and confirms the avian nature of Gargantuavis. The broad pelvis of Gargantuavis is similar to that of various extinct graviportal terrestrial birds.

Pteranodon and beyond: the history of giant pterosaurs from 1870 onwards

Abstract The immense size of many pterosaurs is now well known to academics and laymen alike, but truly enormous forms with wingspans more than twice those of the largest modern birds were not discovered until 83 years after the first pterosaur fossils were found. These remains were discovered in an expedition to the Cretaceous chalk deposits of Kansas led by O.C. Marsh in 1870: initially revealing animals with 6.6 m wingspans, Marsh eventually found material from animals estimated to span 7.6 m. Marsh's record breaking pterosaur – the largest flying animal known for nearly 80 years – was equalled by a supposed wing bone described by C.A. Arambourg in 1954 , and then surpassed with the discovery of the 10 m span azhdarchid Quetzalcoatlus northropi by D. Lawson in 1972. Subsequent fragmentary azhdarchid discoveries suggest even larger forms: reinterpreting Arambourg's ‘wing bone’ as a cervical vertebra suggests an animal with an 11–13 m wingspan, while the Romanian taxon Hatzegopteryx thambema is a particularly large and robust form with a 12 m wingspan. Giant pterosaur footprints are also known, with the largest footprints recording walking azhdarchids of comparable size to those suggested by body fossils.

Scaling of Soaring Seabirds and Implications for Flight Abilities of Giant Pterosaurs

The flight ability of animals is restricted by the scaling effects imposed by physical and physiological factors. In comparisons of the power available from muscle and the mechanical power required to fly, it is predicted that the margin between the powers should decrease with body size and that flying animals have a maximum body size. However, predicting the absolute value of this upper limit has proven difficult because wing morphology and flight styles varies among species. Albatrosses and petrels have long, narrow, aerodynamically efficient wings and are considered soaring birds. Here, using animal-borne accelerometers, we show that soaring seabirds have two modes of flapping frequencies under natural conditions: vigorous flapping during takeoff and sporadic flapping during cruising flight. In these species, high and low flapping frequencies were found to scale with body mass (mass −0.30 and mass −0.18) in a manner similar to the predictions from biomechanical flight models (mass −1/3 and mass −1/6). These scaling relationships predicted that the maximum limits on the body size of soaring animals are a body mass of 41 kg and a wingspan of 5.1 m. Albatross-like animals larger than the limit will not be able to flap fast enough to stay aloft under unfavourable wind conditions. Our result therefore casts doubt on the flying ability of large, extinct pterosaurs. The largest extant soarer, the wandering albatross, weighs about 12 kg, which might be a pragmatic limit to maintain a safety margin for sustainable flight and to survive in a variable environment.

PTEROSAURS PTAKE OFF

A strange little bone called the pteroid protruded from the wrists of pterosaurs, the flying reptiles of the Mesozoic. It was sort of like a thumb,but extended from the base of the wrist and pointed in the opposite direction- towards the body. Or at least that's what most palaeontologists believed,because that was the orientation it always took in fossilised animals. Now,Matthew Wilkinson, David Unwin and Charles Ellington argue that it pointed straight forward - and may have been instrumental in allowing the largest pterosaurs to fly at all.The main part of the pterosaur wing was a thin membrane stretching between the fore- and hindlimbs and supported in front by the arm with a hugely elongated fourth finger. In front of the arm, though, was a smaller forewing called the propatagium, supported by the pteroid bone. If the pteroid pointed forward, the propatagium would have formed a broad leading edge flap, with potentially dramatic aerodynamic consequences, Wilkinson thought.First, the researchers examined fossilised pterosaurs to make sure that it was possible for the pteroid bone to swing into a forward-pointing orientation. Facets in the joint where the small bone articulated made it clear that it could swing from pointing towards the body to pointing forwards,furling and extending the forewing.Then they built three models of the wing with different pteroid positions -fully extended forward, partially furled, and completely absent - and covered them with ripstop nylon to approximate the wing membrane. When they tested the wing models in the University of Cambridge wind tunnel, they found that the extended pteriod conferred a dramatic advantage. The broad forewing increased maximum lift forces by about 60% and, when the wing was nearly parallel with the flow, lift forces jumped from five times the drag force with the forewing furled to about 18 times the drag with forewing extended. As the wing angled up to become more perpendicular to the flow, the pteroid continued to help -it prevented the wing from stalling out, which would cause the lift to drop to zero. Surprisingly, the forewing only seemed to help when it was fully extended; the model with the partially furled forewing performed no better than the model with no forewing at all.In many ways, the forward-pointing pteroid and broad forewing increased the pterosaur wing's performance in the same way that a leading edge flap augments an airplane wing. So the results weren't unexpected - although the amount the forewing helped was impressive. But some researchers had previously rejected the idea of a forward-pointing pteroid, arguing that the puny bone couldn't have supported the stresses that a broad forewing would have imposed on it. Wilkinson waves this objection away, noting that the tip of the fourth digit -which supports the main part of the wing - is as slender as the pteroid and must have supported much higher forces.The pteroid's remarkable aerodynamic performance sheds light on how the largest pterosaurs took off. These giants had wingspans exceeding 10 m - as big as a small plane. But without propellers or jet engines, how did they take off? Some clearly jumped off cliffs. But other specimens have been found with fossilised footprints, suggesting that they took off from flat ground. Wilkinson's results suggest that giant pterosaurs might have merely needed to spread their wings while facing into a moderate breeze to take off.

A giant pterosaur from the Lower Cretaceous of the eastern Paris Basin

Abstract A large pterosaur bone, preserved as a natural cast of the interior cavity, was found in an old collection kept at the Natural History Museum of Troyes (France). Although no precise geographical data are available, the lithology of the matrix indicates that it comes from the Hauterivian Toxaster Limestone of the eastern Paris Basin. Despite its unusual preservation, the specimen shows various morphological details, and is identified as an ornithocheiroid pterosaur humerus. This specimen is among the largest known pterosaur humeri (length as preserved: 345 mm), indicating a wing span of more than 7 metres. It shows that giant pterosaurs had already appeared at a very early stage in the Cretaceous.

Giant pterosaurs from the Lower Cretaceous of the Isle of Wight, UK

Giant pterosaurs from the Lower Cretaceous of the Isle of Wight, UK