Urodela and Caecilian

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  • Amphibian Diversity and Biology
    • Gymnophiona (Caecilians
      • Superficially earthworm-like, limb-less, tail-less and fossorial amphibians
      • Diagnostics
        • No tail; terminal or subterminal cloaca
        • No limbs or girdles
        • Small, sometimes protrusible eyes or none
          • Otic notch and impedance-matching ear lost
            • Endochondral elements of the neurocranium are fused into an os basale (HEAVILY OSSIFIED SKULL); bones of the jaw fused into pseudodentary and pseudoangular
            • Behind jaw articulation a large process gives leverage for jaw-closing muscles that originate on the branchial skeleton
        • Internally fertilizing
        • Sensory tentacle (paired) between eye and nostril
        • Oviparous or viviparous
        • Two sets of jaw-closing muscles
          • STRONG JAWS
        • Dermal scales; skin annulations (concentric rings called annuli)
          • BREATHABLE
      • Reproduction
        • Internal insemination only
        • Male: long, tube-like intromittent organ (phallodeum)
        • 25% oviparous
          • egg guarding
          • Some eggs, the young already metamorphosed, some hatch as larvae (not fully aquatic). Any larvae gills are lost with time
        • 75% viviparous
          • Foetus fed inside female with cells lining the oviduct, which they eat with scraping teeth
        • Dermatothrophy
          • Egg-laying species that feeds young by developing outer skin high in fat etc which young peel off with scraping teeth
    • Urodela (Salamanders. Newts)
      • Elongate bodies, skin grooves along flanks, long tail, four equal/ subequal limbs where present
      • Diagnostics
        • Tail in Larvae/adults; two pairs equal limbs
        • NO otic notch or middle ear; stapes w/ short stylus and large footplate
          • Impedance-matching ear is reduced; maxilla does not connect posteriorly with the cheek, creating a gap in the skull margin
        • Gill slits/ external gills in aquatic larvae
        • No teeth on both jaws
        • Short, stumpy ribs borne on bicipital rib bearing processes
        • Small levator mandibulae posterior muscle
        • Most w/ intercostal grooves marking position of muscular septa in trunk
        • Dorsal origin for adductor mandibulae internus superficialis muscle
      • Diet/prey capture (generalist carnivores, primarily inverts)
        • Aquatic
          • Mouth gape
            • Suction into oral cavity; working with one way flow of gills,
            • Tongue: broad, flat immobile
        • Terrestrial
          • Thick, sticky tongue grabs prey
      • Senses
        • Aquatic
          • Vibrations- retain lateral line system
          • Taste chemicals
        • Terrestrial
          • Smell- Vomeronasal organ (nnon-volatile)
            • Bigger in males
            • Courtship/ identification
            • Nasolabial grooves: non-ciliated grooves, upper lips to nares
              • Sexually dimorphic (especially in repro season)
              • Aids in collection/ delivery of chem cues (capillary action)
          • Vision- acute
          • Smell- Olfactory epithelium (volitile)
          • Hearing- limited (no eardrum); primarily ground vibrations.
      • Larvae
        • Stream
          • Depressed body profile, narrow tail fin (not onto trunk), short thread-like or curly gills and all four legs at hatching
        • Pond
          • High body profile, broad tail fin extending up to head, long, plume-like gills, only front legs at hatching
      • Defence mechanisms
        • Biting
        • Toxins
        • Posture
        • Tail autotomy
        • Case: poking poison glands on flanks with needle-like ribs
        • Unkenreflex
        • Rolling up and rolling away

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