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Classification of Vertebrates

  • Reptilian vertebrates

    • Chordata: Animals with a notochord at some stage of life

    • Vertebrata: Chordates with vertebrae and a cranium

    • Gnathostomata: Vertebrates with jaws

    • Osteichthyes: Bony fishes and tetrapods

    • Tetrapoda: Four-limbed vertebrates

    • Amniota: Tetrapods with embryos having extraembryonic membranes

Key Groups of Vertebrates

  • Protochordata: Non-vertebrate chordates

    • Agnatha: Jawless fish (hagfishes, lampreys)

    • Cephalochordata: Lancelets

    • Urochordata: Tunicates

  • Chondrichthyes: Cartilaginous fishes (sharks, rays)

  • Actinopterygii: Ray-finned fishes

  • Lobefinned fishes: Ancestors of tetrapods

  • Amphibia: Frogs, salamanders

  • Mammalia: Animals with hair and mammary glands

  • Reptilia: Includes lizards, snakes, crocodilians, turtles, birds (Aves)

Characteristics of Amniotes

  1. Amniotic Egg: Structure includes amnion, allantois, chorion, shell, and yolk sac for support, waste storage, and nutrient storage.

  2. Copulatory Organs: Adaptations for internal fertilization.

  3. Skin: Thicker and more keratinized to prevent water loss.

  4. Stronger Jaws: Enable better prey handling.

  5. Rib Ventilation: Draws air into lungs.

  6. Cardiovascular System: High-pressure setup with separate ventricles.

  7. Water-Conserving Excretion: Nitrogenous wastes primarily urea or uric acid.

  8. Advanced Sensory Organs: Enhanced brain and olfactory capacities.

Order Testudines (Turtles)

  • Ectothermic reptiles; keratinized jaws, oviparous reproduction.

  • Shell composed of carapace and plastron.

  • Varied detection abilities: poor hearing, good color vision, excellent olfaction.

Order Squamata (Lizards and Snakes)

  • Kinetic skull allowing for prey manipulation.

  • Includes various reproductive strategies: oviparous, ovoviviparous, viviparous.

  • Snakes evolved from lizard lineage.

Lizards

  • Have movable eyelids and external ears.

  • Include diverse forms such as geckos, iguanas, and chameleons.

Snakes

  • Limbless; utilize numerous vertebrae for movement.

  • Unique adaptations for prey capture: Jacobson’s organs, constriction, venom.

Order Crocodilia (Crocodilians)

  • Four-chambered heart; sister group to birds.

  • Distinct features include robust skull and jaw structure, egg care behavior.