Mean: 72% 1 Flying Reptiles of the Mesozoic Bird Evolution Summary - - PowerPoint PPT Presentation

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Mean: 72% 1 Flying Reptiles of the Mesozoic Bird Evolution Summary - - PowerPoint PPT Presentation

Jul 27, 2023 314 likes •773 views

Histogram of x 12 10 8 Frequency 6 4 2 0 0.0 0.2 0.4 0.6 0.8 1.0 Score Mean: 72% 1 Flying Reptiles of the Mesozoic Bird Evolution Summary Birds are theropod dinosaurs, demonstrated by similarities in osteology, oology,

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Histogram of x

Score Frequency 0.0 0.2 0.4 0.6 0.8 1.0 2 4 6 8 10 12

Mean: 72%

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Flying Reptiles of the Mesozoic

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  • Birds are theropod dinosaurs, demonstrated by similarities in
  • steology, oology, integument, and behavior
  • Feathers and arm flapping evolved before the animals were

capable of powered flight

  • Flight likely first evolved in paravian theropods (not in birds),

but they were poor fliers

  • Further acquisition of flight adaptations (pygostyle, sternum,

alula) occurred during Mesozoic bird evolution

  • Flying pterosaur reptiles are not related to birds but display

convergent evolution of many flight adaptations

Bird Evolution Summary

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Pterosauria Earliest vertebrates known to evolve powered flight!

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Pterosauria

10 in 33 ft 23 ft 13 ft

Quetzalcoatlus

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Pterosauria: early forms Late Triassic - Late Jurassic

Eudimorphodon: (sea gull sized) Already and advanced flyer

Short body Elongate 4th finger Pteroid bone

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Archosauria Crown-clade Archosauria Ornithodira

Crurotarsi Ornithosuchidae Pterosauria Dinosauria “Rauisuchia” Crocodylomorpha Basal archosaurs

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Pterosauria

Ornithodira:

Scleromochlus Pterosauria Lagosuchus Dinosauria Upright gait S-curved necks Hinged Ankle Aves

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Pterosaur Traits

Hollow limb bones Breastbone with Keel Enlarged brain Stiff torso Pteroid Elongate 4th finger 3 membranes: First Arm Tail Cranial Crests

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Pterosaur Traits: pneumatic bones

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Pterosaur Traits: air sacs

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Dsungaripterus Pteranodon

Pterosaur Traits: cranial crests Keratinous

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Pterosaur Traits: cranial crests

Nyctosaurus; late Cretaceous Sometime, ridiculous things happen.

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Pterosaur Traits: jaw diversity

Ramphorynchids

Scaphognathus Dorygnathus Sordes Campylongnathoides

Basal Pterosaurs (paraphyletic) Late Triassic Long teeth and nails Most lacked bony crests

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Dimorphodon

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Ornithocheirus Pterodaustro Ctenochasma

Fisheaters, Filterers

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Pterosaur Traits: jaw diversity Pteranodon

No teeth Scoop-shaped bill One of the best known large Pterosaurs Sexually Dimorphic crests Heavily fused body to protect against flight-related stress Potentially more Glider-like (Wing shape similar to Albatross)~ dynamic soaring Piscivore

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Pterosaur Traits: skin

Covered in hair-like filaments: Pycnofibres NOT HAIR Similar in structure: convergent evolution Very convincing evidence that these animals were endothermic

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Sordes pilosus “Hairy Demon”

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Pterosaur Eggs

Thin, soft shelled eggs No evidence of multiple laminar layers

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Pterosaur Flight

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high aspect ratio (long, slender) low aspect ratio (short, squat) Frigate Bird

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Convergent Flight Adaptations in Pterosaurs

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Pterosaurs independently evolved a pectoral girdle for supporting flight muscles Pterosaur pectoral girdle Avian pectoral girdle

Pectoral Girdle Similarities

Large fused sternum with keel Strut-like coracoid bones fused to sternum Short, stout humerus (arm bone)

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No feathers – instead use skin membrane stretched across hand Wing surface primarily supported by extended finger digit IV Pteroid bone – unique to pterosaurs Bird alula Bird wing: feathers Wing surface primarily supported by ulna, wrist

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Unique Flight Adaptations in Pterosaurs

Wing support Outer wing supported by Actinofibrils 3 distinct layers of criss-crossed fibers Keratin? Elastin? Unknown. Oxygenated by looping blood vessels

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Actinofibrils: Arranged perpendicularly to lines of highest tension in wing Tension

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Alternative Wing Structures

Wing structure highly variable in modern animals Almost certainly was variable among Pterosaurs There is likely no ‘One right answer’ here

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Pterosaur Walking

An evolving concept... A) 1970s: Belly dragging B) 1980s: Bipedality C) 1990: Semi-erect D) 1990s: Sprawling Still a source of contention!

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Top: Pteraichnus Bottom: Running Caiman

A B

Pterosaur Walking

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Tail Vanes

Present among early Pterosaurs; particularly Ramphorynchus Much reduced among derived Pterosaurs Probably a stabilizing feature More diamond-shaped among older animals

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Unique Flight Adaptations in Pterosaurs

Laser Beam eyes Convergently evolved in Kryptonian humanoids

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Largest bird (Argentavis, Miocene) had 7 m wingspan and weighed 80 kg

Giant Flying Animals

Largest pterosaur (Quetzalcoatlus, from the latest Cretaceous) had a 12 m wingspan and weighed 100 kg

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Largest pterosaurs were probably excellent gliders but would have had difficult reaching takeoff velocity

Giant Pterosaurs

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Pterosaur documentary 10:13

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