Paleontology

• what is within Lepidosauria?

  lizards, snakes, and their earlier lizards
• what is Rhynchocephalia?


  - early lizards - Tuatara today
• when did Rhynchocephalia evolve?


  Triassic
• what is Squamata?


  modern lizards
• when did Squamata evolve?

  Jurassic and Cretaceous
• when did snakes evolve?

  evolved from lizards by the Late Cretaceous
• what are the main characteristics of lepidosaurs?

  - overlapping scales that are shed as the animal grows

  - modern lepidosaurs have a mobile quadrate bone and have lost the bars beneath the lower temporal fenestrae (how snakes unhinge their jaws)
• when did turtles and tortoises evolve?

  early Triassic
• what did turtles evolve from?

  diapsids NOT ANAPSIDS
• what are the physical characteristics of turtles?


  - solid skull with no fenestrae

  - shell develops from ribs

  - plastron evolved before the rest of the shell

  - limbs modified for walking or swimming
• what are the different groups of marine reptiles?

  turtles, ichthyosaurs, plesiosaurs, mosasaurs
• when did ichthyosaurs evolve?

  Early Triassic
• what are the characteristics of ichthyosaurs?

  - fish shaped marine reptiles

  - large eyes, long snouts with sharp teeth, and streamlined bodies suggest they were active predators

  - the vertebrae in their caudal fin go down
• when did plesiosaurs evolve?

  at the end of the Triassic, became common in the Jurassic
• what are the characteristics of plesiosaurs?

  most had less streamlined bodies with an elongate neck and large flippers
• what are the characteristics of pliosaurs and polycotylids?

  - shorter necks and larger head

  - adapted to hunting larger prey as they had larger and more robust teeth
• when did mosasaurs evolve?

  during the Cretaceous
• what did mosasaurs evolve from?

  aquatic lizards (lepidosaurs)
• what niche did mosasaurs fill?

  common predators in the inland seas of the Cretaceous
• how do marine reptiles regulate their temperature?

  all marine reptiles except turtles were likely endothermic
• how do marine reptiles give birth?

  all marine reptiles except turtles gave birth to live young (viviparous)
• when did marine reptiles go extinct?


  - ichthyosaurs disappeared early in the Late Cretaceous

  - plesiosaurs and mosasaurs went extinct at the end Cretaceous

  - turtles are still alive
• what are the different groups within Archosauria?

  crocodiles, pterosaurs, dinosaurs, birds
• what characteristic do all archosaurs have?


  derived diapsids with an antorbital fenestra and deep socketed teeth
• when did archosaurs appear?

  Late Triassic
• what are the two groups in Archosauria?

  pseudosuchians and avemetatarsalians
• what are pseudosuchians?


  crocodiles and alligators
• what type of posture do pseudosuchians have?

  sprawling gait with legs splayed out to the side
• what are avemetatarsalians?


  dinosaurs, pterosaurs, and birds
• what type of posture do avemetatarsalians have?

  upright posture for better mobility, but higher metabolic costs
• what did crocodilians evolve from?


  pseudosuchians
• generally explain crocodilian evolution

  - early crocodilians in the Triassic were largely terrestrial and heavily armoured

  - became more diverse in the Jurassic with the evolution of marine forms

  - most modern crocodilians evolved in the Late Cretaceous
• what is the stratigraphic range of pterosaurs?

  Late Triassic to Cretaceous
• what are the physical characteristics of pterosaurs?

  - small and delicate skeletons and large wings supported by an elongate fourth finger

  - probably endothermic and covered in hair like feathers
• what did pterosaurs eat?

  fish in coastal areas and insects in more inland environments to support their high metabolism
• when did dinosaurs evolve?

  Late Triassic
• what bones do dinosaurs walk on?

  the metatarsals, digitigrade stance
• what is digitigrade stance?

  walking on toes
• what is plantigrade stance?


  walking on whole foot
• what is unguligrade stance?


  walking on hooves