Icthyology - Conodonts & Agnatha ( Lecture 2)

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Last updated 4:40 AM on 10/3/26
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8 Terms

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<ol><li><p>Early chordates </p></li></ol><p></p>

  1. Early chordates


  • Urochordates: Also known as Tunicates + sales

  • Cephalochordates: Lancelets

  • Craniata : vertebrates


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Craniata Synapomorphies ( vertebrates)

  • Cranium → The hard skull and protects the brain

  • Cartilage and / or bone →

  • Chambered heart → heart divided into separate sections

  • Neutral crest → They develop into the skull , jaws, parts of the nervous system


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<ol start="2"><li><p>Conodonts </p></li></ol><p></p>

  1. Conodonts


  • Early vertebrate like animals

  • Appeared about 530 million years ago

  • Known for tooth like/ bitting elements → having tiny , mineralized tooth like fossil


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  1. Early vertebrates - Agnatha


Synapomorphies

  • No jaws → they have round suckers like mouth

  • No pelvic fins → They have only basic tail

  • Appeared 530 MYA


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Ostracoderms

  • Early jawless vertebrates

  • armored

  • Paraphyletic →they are not complete evolutionary tree


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  1. Hagfish - class Myxini


  • 30-35 species

  • Marine only

  • deep water

  • Scavengers → that feed on dead and dying creatures on the ocean floor

  • Isosmotic

  • Do not osmoregulate:

  • Develop directly from eggs


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  1. Lampreys - class Petromyzontida


  • 40 species

  • Freshwater + ocean

  • Osmoregulate

  • Often parasitic


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Larva : Ammocoete

  • Filter feeds

  • Then → metamorphosis → adult