5.6 Flying reptiles

Flying reptiles dominated the Mesozoic skies, showcasing incredible diversity and adaptations. From tiny Nemicolopterus to giant Quetzalcoatlus, these creatures evolved unique anatomical features like elongated wing fingers and lightweight bones for powered flight.

Pterosaurs, the most successful flying reptiles, occupied various ecological niches throughout their 150-million-year reign. Their fossil record reveals a fascinating evolutionary journey from small, toothed forms to specialized filter-feeders and massive terrestrial predators before their ultimate extinction.

Types of flying reptiles

• Flying reptiles were a diverse group of animals that evolved the ability to fly independently from birds and bats
• Pterosaurs were the most successful and well-known flying reptiles, but other groups like the sharovipterygids and kuehneosaurids also developed gliding or flying abilities
• Flying reptiles showcase the power of convergent evolution, where similar traits (like wings) evolve independently in different lineages

Pterosaurs vs other flying reptiles

Top images from around the web for Pterosaurs vs other flying reptiles

• 

  Studying the History of Life ‹ OpenCurriculum View original

  Is this image relevant?

• 

  Pterosaur - Wikipedia View original

  Is this image relevant?

• 

  Studying the History of Life ‹ OpenCurriculum View original

  Is this image relevant?

• 

  Pterosaur - Wikipedia View original

  Is this image relevant?

1 of 2

Top images from around the web for Pterosaurs vs other flying reptiles

• 

  Studying the History of Life ‹ OpenCurriculum View original

  Is this image relevant?

• 

  Pterosaur - Wikipedia View original

  Is this image relevant?

• 

  Studying the History of Life ‹ OpenCurriculum View original

  Is this image relevant?

• 

  Pterosaur - Wikipedia View original

  Is this image relevant?

1 of 2

• Pterosaurs were the largest and most diverse group of flying reptiles, with over 100 known species ranging from sparrow-sized to airplane-sized
• Other flying reptiles, like sharovipterygids and kuehneosaurids, were much smaller and less diverse than pterosaurs
  • Sharovipterygids (Sharovipteryx) were small, lizard-like gliders from the Triassic Period
  • Kuehneosaurids (Kuehneosaurus) were another group of Triassic gliding reptiles with elongated ribs that supported a gliding membrane
• Pterosaurs had unique anatomical features like a elongated fourth finger that supported the wing membrane, while other flying reptiles used different strategies like elongated ribs or a skin flap

Diversity in size and appearance

• Pterosaurs ranged in size from tiny species like Nemicolopterus with a wingspan of just 25 cm (10 inches) to giant forms like Quetzalcoatlus with a wingspan of over 10 meters (33 feet)
• Pterosaur diversity peaked in the Cretaceous Period, with a wide variety of shapes and sizes coexisting
  • Some pterosaurs like Pterodaustro had thousands of needle-like teeth for filter-feeding, while others like Pteranodon were toothless
  • Unusual forms included Tapejara with its huge, sail-like head crest and Nyctosaurus with its extremely elongated wing fingers
• This diversity in size and appearance suggests that pterosaurs occupied a wide range of ecological niches, from coastal filter-feeders to inland predators and scavengers

Anatomy of pterosaurs

• Pterosaurs had a highly modified skeleton adapted for flight, with lightweight, hollow bones and unique anatomical features not seen in other animals
• The pterosaur body plan included an enlarged braincase, elongated neck and trunk, and a short, stiffened tail
• Pterosaurs are often incorrectly reconstructed with bat-like wings or as quadrupedal crawlers, but their anatomy was very different from either bats or typical reptiles

Unique skeletal adaptations for flight

• Pterosaur bones were incredibly lightweight and hollow, with a complex system of internal struts and braces for strength
  • Some pterosaur bones had a higher strength-to-weight ratio than bird bones
• The pterosaur shoulder girdle was highly modified to support the flight muscles, with a large, keeled sternum and ossified sternal ribs
• Pterosaurs had an elongated fourth finger (the "wing finger") that supported the main part of the wing membrane
  • This wing finger could be folded back alongside the body when not in use, unlike the permanently outstretched wings of birds and bats

Wing structure and composition

• Pterosaur wings were composed of three main parts: the propatagium (fore-wing), brachiopatagium (main wing), and uropatagium (hind-wing)
  • The propatagium stretched from the shoulder to the wrist
  • The brachiopatagium was the largest part of the wing, supported by the elongated fourth finger
  • The uropatagium connected the legs to the tail and may have helped with steering and stability
• The wing membrane was composed of several layers of stiffened skin, muscle fibers, and blood vessels
  • Pterosaur wing membranes preserved as fossils show a complex pattern of muscle fibers that likely helped control the shape and tension of the wing during flight

Skull and dental variations

• Pterosaur skulls were highly variable in shape and size, reflecting their diverse diets and feeding strategies
  • Basal pterosaurs like Rhamphorhynchus had long, toothed jaws suited for catching fish
  • More derived pterodactyloids like Pteranodon had elongated, toothless beaks for snapping up fish or squid
  • Bizarre forms like Pterodaustro and Nyctosaurus had hugely elongated jaws with specialized teeth for filter-feeding
• Pterosaur teeth, when present, were typically conical and pointed, but some species had highly specialized dental arrangements
  • Ctenochasma had up to 200 long, thin, closely-packed teeth for sieve-feeding
  • Dsungaripterus had short, blunt teeth with thickened enamel for crushing shellfish

Flight mechanics

• Pterosaur flight has been a topic of debate and research since the first pterosaur fossils were discovered in the 18th century
• Scientists have used a variety of methods to study pterosaur flight, including comparisons with living animals, aerodynamic models, and wind tunnel experiments
• While many aspects of pterosaur flight are now well-understood, some questions still remain about their flight capabilities and limitations

Theories of pterosaur flight

• Early theories suggested that pterosaurs were clumsy gliders or that they were quadrupedal launchers, taking off with a leap from all four limbs
• Modern research indicates that pterosaurs were active, flapping flyers capable of powered flight
  • Pterosaur wings were shaped like airfoils, producing lift during flapping flight
  • The pterosaur shoulder girdle and flight muscles were well-developed for active flapping
  • Trackways and bone strength analysis suggest pterosaurs were competent walkers and runners, not quadrupedal launchers
• Different pterosaur species likely had different flight styles depending on their size and ecology
  • Larger pterosaurs may have relied more on soaring and gliding, while smaller forms were more active flappers

Comparisons to modern flying animals

• Pterosaurs have been compared to both birds and bats in terms of their flight mechanics and capabilities
• Like birds, pterosaurs had hollow bones, a keeled sternum, and a stiffened torso for anchoring flight muscles
  • However, pterosaur wings were composed of a skin membrane rather than feathers, and their wing finger allowed the wing to be folded back when not in use
• Like bats, pterosaurs had a skin membrane wing and an elongated hand that supported the wing
  • However, pterosaur wings were stiffer and more muscular than bat wings, and pterosaurs lacked the clawed fingers of bats
• Pterosaurs represent a unique mode of vertebrate flight, with similarities to both birds and bats but also key differences

Limitations and capabilities of flight

• Pterosaur flight was likely constrained by factors like size, weight, and wing shape
  • Very large pterosaurs like Quetzalcoatlus may have been limited to soaring flight and short bursts of flapping, due to the high energy costs of powered flight at large sizes
  • Pterosaurs with short, broad wings like Anurognathus were likely more maneuverable but less efficient at gliding than long-winged forms like Zhejiangopterus
• Pterosaurs were likely capable of a wide range of flight behaviors, including:
  • Soaring on thermals and updrafts
  • Flap-gliding with alternating periods of powered flight and gliding
  • Rapid take-offs and landings
  • Aerial maneuvering to catch prey or avoid predators
• However, pterosaurs may have been less agile and maneuverable than birds, due to their membrane wings and lack of a separate, mobile tail for steering

Evolutionary history

• Pterosaurs evolved in the Triassic Period and diversified through the Jurassic and Cretaceous, before going extinct at the end of the Cretaceous along with the non-avian dinosaurs
• The pterosaur fossil record shows a clear trend towards larger sizes and more specialized forms over time
• Despite their long evolutionary history, many aspects of pterosaur origins and evolution remain uncertain due to gaps in the fossil record

Origins in the Triassic Period

• The oldest known pterosaur fossils come from the Late Triassic, around 215 million years ago
  • The earliest pterosaurs like Eudimorphodon were small, toothed forms with long tails and relatively short wings
  • These early pterosaurs were already capable of powered flight, indicating that pterosaurs likely originated even earlier in the Triassic
• The exact relationships of pterosaurs to other reptile groups are still debated
  • Some analyses place pterosaurs as close relatives of dinosaurs, while others suggest they branched off earlier from the archosaur family tree
• The ancestors of pterosaurs were likely small, arboreal reptiles that developed gliding abilities as an adaptation for moving between trees

Diversification in the Jurassic

• Pterosaurs underwent a major diversification in the Jurassic Period, evolving a wide variety of sizes and specializations
  • Rhamphorhynchoids like Rhamphorhynchus and Scaphognathus were common in the Early and Middle Jurassic, with long tails and toothed jaws
  • Pterodactyloids like Pterodactylus and Germanodactylus appeared in the Late Jurassic, with shorter tails and more elongated skulls
• The Jurassic saw the evolution of filter-feeding pterosaurs like Pterodaustro, as well as the first giant pterosaurs like Arambourgiania
• By the end of the Jurassic, pterosaurs had spread across the globe and occupied a variety of ecological niches, from coastal fish-eaters to terrestrial insectivores

Decline and extinction in the Cretaceous

• Pterosaurs continued to diversify in the Cretaceous Period, but their fossil record becomes sparser and more fragmentary towards the end of the period
• Giant azhdarchids like Quetzalcoatlus and Hatzegopteryx were the dominant pterosaurs of the Late Cretaceous, with wingspans of over 10 meters
  • These giant pterosaurs were likely terrestrial stalkers and scavengers, similar to modern storks and ground hornbills
• Other Cretaceous pterosaurs included small, specialized forms like the crested Nyctosaurus and the filter-feeding Pteranodontia
• Pterosaurs went extinct at the end of the Cretaceous, around 66 million years ago, along with the non-avian dinosaurs and many other groups
  • The cause of the pterosaur extinction is still debated, but likely factors include the Chicxulub impact event and associated global environmental changes
  • Competition with birds, which were diversifying rapidly in the Late Cretaceous, may also have contributed to pterosaur decline

Ecology and behavior

• Pterosaurs occupied a wide variety of ecological niches and habitats, from coastal marine environments to inland forests and plains
• Pterosaur behavior is difficult to study directly from fossils, but clues can be found in their anatomy, trackways, and coprolites (fossilized feces)
• Pterosaurs likely had complex social behaviors and reproductive strategies, similar to modern birds and other archosaurs

Habitat preferences

• Pterosaurs are found in a variety of depositional environments, indicating they occupied diverse habitats
  • Many pterosaurs, like Pteranodon and Anhanguera, are found in marine sediments and were likely coastal fish-eaters
  • Other pterosaurs, like Quetzalcoatlus and Hatzegopteryx, are found in terrestrial sediments and were likely inland predators and scavengers
• Pterosaur trackways are known from a variety of substrates, including beaches, mudflats, and river banks
  • These trackways suggest that pterosaurs were competent walkers and runners, not just aerial specialists
• Some pterosaur fossils show evidence of swimming adaptations, like webbed feet in Pterodactylus
  • These pterosaurs may have been able to take off and land on water, like modern seabirds

Feeding strategies and diet

• Pterosaur diets can be inferred from their tooth and jaw morphology, as well as direct evidence like gut contents and coprolites
• Many pterosaurs, especially early forms, were piscivores (fish-eaters) with long, toothed jaws for catching slippery prey
  • Pteranodon and other toothless pterosaurs were also likely fish-eaters, using their long beaks to snap up prey from the water's surface
• Other pterosaurs were filter-feeders, using specialized teeth to strain small prey from the water
  • Pterodaustro had up to 1000 thin, closely-packed teeth for filtering plankton and other small organisms
• Some pterosaurs, like Quetzalcoatlus, were likely terrestrial predators and scavengers
  • These giant pterosaurs had long, stork-like beaks and reduced teeth, suitable for picking up small vertebrates and carrion
• Pterosaur coprolites contain the remains of fish, crustaceans, insects, and even small dinosaurs, confirming their diverse diets

Social behavior and reproduction

• Pterosaur social behavior is difficult to study directly, but some inferences can be made from modern animals and fossil evidence
• Many pterosaur fossils are found in mass death assemblages, suggesting they may have lived in flocks or colonies
  • These mass assemblages often contain individuals of different ages and sizes, indicating pterosaurs had extended parental care like modern birds
• Pterosaur trackways sometimes show multiple individuals walking together, possibly reflecting social or mating behavior
• Pterosaur eggs and embryos are known from several sites, providing clues about their reproductive strategies
  • Pterosaur eggs were small and pliable, similar to modern reptile eggs
  • Some pterosaur embryos show well-developed flight membranes, suggesting they were able to fly soon after hatching (precocial development)
• Pterosaurs may have had mating displays and territorial behavior, like modern birds, but direct evidence is lacking

Fossil record

• Pterosaurs have a patchy and incomplete fossil record, due to their delicate bones and the specific conditions required for preservation
• However, some exceptional fossil sites have yielded well-preserved pterosaur specimens that provide detailed insights into their anatomy and ecology
• New pterosaur fossils continue to be discovered, filling in gaps in the fossil record and revealing previously unknown diversity

Notable pterosaur fossil discoveries

• The first pterosaur fossil was discovered in the 18th century, but was misidentified as a marine creature
  • In 1784, Cosimo Collini described a partial pterosaur skeleton from Germany, naming it Pterodactylus antiquus
• The 19th century saw a flurry of pterosaur discoveries, including the first non-pterodactyloid pterosaurs and the recognition that pterosaurs were flying reptiles
  • In 1828, Mary Anning discovered the first rhamphorhynchoid pterosaur, Dimorphodon, in England
  • In 1876, Othniel Charles Marsh named Pteranodon, the first giant pterosaur known from good fossil material
• The 20th century saw the discovery of many important pterosaur fossils, including the first known eggs and embryos
  • In 1971, Douglas Lawson discovered a Pteranodon pelvis with an egg inside, confirming that pterosaurs laid eggs
  • In the 1990s, deposits in Brazil and China yielded spectacularly preserved pterosaur fossils, including soft tissue impressions and 3D eggs
• The 21st century has seen a boom in pterosaur discoveries, with dozens of new species named from around the world
  • In 2014, the discovery of a new specimen of Quetzalcoatlus in Texas confirmed its status as the largest known flying animal of all time

Preservation bias and rarity

• Pterosaur fossils are rare due to several factors that limit their preservation potential
  • Pterosaur bones were lightweight and hollow, making them easily crushed or destroyed after death
  • Pterosaurs lived mostly in terrestrial environments, where carcasses are quickly scavenged and weathered
  • Pterosaur wings were composed of soft tissue that rarely fossilizes
• As a result, the pterosaur fossil record is heavily biased towards aquatic environments and exceptional preservation conditions
  • Most pterosaur fossils are found in marine sediments, where carcasses can sink to the bottom and be buried quickly
  • Lagerstätten (fossil beds with exceptional preservation) like the Solnhofen Limestone in Germany and the Santana Formation in Brazil have yielded the majority of well-preserved pterosaur fossils
• This preservation bias means that our understanding of pterosaur diversity and ecology is likely incomplete
  • Terrestrial pterosaurs and soft-tissue features are probably underrepresented in the fossil record

Insights from exceptional fossil sites

• Exceptional fossil sites have provided detailed insights into pterosaur anatomy, diversity, and behavior that are not possible from more typical fossils
• The Solnhofen Limestone in Germany has yielded many well-preserved pterosaur fossils, including soft tissue impressions and stomach contents
  • Rhamphorhynchus specimens from Solnhofen preserve the wing membrane and tail vane in detail, allowing for detaile