Jawed Fish Flashcards

1
Q

Jawed Vertebrates

A

Gnathostomata = “jaw + mouth”
- where did the jaws come from?
- why did they evolve?
- why are they one of the biggest vertebrate developments?

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2
Q

Origin of Jaws

A

From “2 pairs” or endochondral cartilaginous articulated arches: mandibular and hyoid arches
- Evo-devo and genetic evidence:
- similar in form, machinery, and origin to gill arches (i.e., supports and pumps water across gills)
- But note the 2 pairs of pseudobranches anterior to these:
- evo-devo evidence: derived from mandibular arch

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3
Q

Paired Fins

A
  • Pectoral and pelvic pairs
  • yaw, pitch, roll
  • Two-part hypothesis origins:
    1. Finfolds (e.g., anaspids) -> row of finlets -> paired fins
    2. Outgrowths of lateral plate mesoderm tissue
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4
Q

“Placoderms”: The First Gnathostomes

A
  • The armored fishes with jaws
    • Ornamented bony shield
  • Separate head and trunk shield (unlike “ostracoderms”)
  • Mobile joints (jaws, hinged head/neck, fins)
    • head lifted up during feeding
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5
Q

“Placoderm” Endo and Exoskeleton

A

Endoskeleton: cartilage
Exoskeleton: dermal bone
Placoderms were the most common, most diverse of Devonian vertebrates; now extinct

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