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Extant Amphibia

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Caudata. Most have internal fertilization, but no copulatory organ. Male ... Caudata. 3 main groups, with distinct evolutionary lineages (distinct clades) ... – PowerPoint PPT presentation

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Title: Extant Amphibia


1
Extant Amphibia
  • Caecilians and Urodeles

2
Caudata
  • Most have internal fertilization, but no
    copulatory organ.
  • Male deposits spermatophore.
  • Female picks up the spermatophore with her
    cloacal lips.
  • All families probably arose in the Mesozoic.

3
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4
Caudata
  • 3 main groups, with distinct evolutionary
    lineages (distinct clades).
  • Basic phylogeny is unresolved except for 3 major
    groups. This is probably because of the high
    level of neoteny, which may obscure important
    characters.

5
Caudata Meantes
  • These are the sirens.
  • Eel like
  • small pectoral appendages
  • lack pelvic girdle hind limbs
  • no premaxillary teeth - have horny beak.
  • Gills, therefore neotenic (paedomorphic)
  • external fertilization.

6
Caudata Cryptobranchoidea
  • Hynobiidae
  • Usually have functional lungs.
  • Not neotenic (paedomorphic).
  • External fertilization.
  • Cryptobranchidae
  • Neotenic lack gills but retain gill slits
  • external fertilization.
  • Lungs reduced or absent
  • they are large, up to about 1.5m.

7
Caudata Salamandroidea
  • Proteidae
  • Neotenic
  • unusual distribution, may not be a natural group.
  • Includes the mudpuppy, Necturus.
  • Females guard eggs.
  • Dicamptodontidae
  • Pacific NW of USA.
  • Free columella
  • Spinal nerves exit intravertebrally (ancestral)
  • Some forms are permanently neotenic, some are
    facultatively neotenic.

8
Caudata Salamandroidea
  • Amphiumidae
  • eel-like and aquatic
  • Neotenic loose gills but retain gill slits and
    lidless eyes.
  • Limbs and girdles are reduced.
  • Internal fertilization male deposits
    spermatophore directly into Female cloaca.
  • Salamandridae (newts)
  • Posess lungs.
  • Only 2 anteriormost spinal nerves exit
    intervertebrally.
  • Usually bright colors.
  • 2 species are live bearers.
  • Some lay terrestrial eggs.

9
Salamandrid life cycles
  • 1) Larvae metamorphose --gt aquatic juveniles
  • 2) Aquatic larvae metamorphose --gt terrestrial
    form --gt water to breed.
  • 3) aquatic larvae --gt terrestrial juvenile (efts)
    --gt aquatic adults.

10
CaudataSalamandroidea
  • Ambystomatidae
  • Terrestrial adults, usually return to water to
    breed.
  • Some neotenic.
  • Lg. functional lungs.
  • Winter breeders during warm spells.
  • Male deposits numerous spermatophores.
  • Plethodontidae
  • Only forms to have nasolabial grooves.
  • Spinal nerves exit intra-vertebrally
  • They have no lungs live in rapid, turbulent
    mountain streams.

11
Plethodontid forms
  • 1) Desmognathinae upper jaw opens up while the
    lower jaw is stationary.
  • 2) Plethodontinae jaws function in the normal
    way.

12
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13
Caecilians
  • 1) Fossil record consists of 1 fossil vertebra
    from the Paleocene of Brazil.
  • 2) It is most similar to the african genus
    Geotrypetes in the family Caeciliaidae.
  • 3) The Caeciliaidae are african and s. american.
    Thus, Gondwana is probably the place of origin,
    and the modern families exist in the Paleocene.

14
Caecilians
  • Earthworm-like in appearance
  • Annular rings
  • Bony ossicles/dermal scales may be present.
  • Eyes lie below skin or even below the
    dermocranium.
  • Tentacles - sensory papilla around mouth
    (between nostril and eye).

15
Caecilians
  • Jaw is underhung
  • Designed for fossorial life and serpentine and
    concertina locomotion.
  • No ear openings.
  • All forms have internal fertilization.
  • Male has a phallodeum which is a modified portion
    of the cloacal wall.
  • Development may be internal or external, direct
    or indirect.

16
Caecilians
  • Distribution is worldwide tropics except
    madagascar and Papua-New Guinea/Australia.
  • There are 150 species in 6 families.

17
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18
Cacilian Characters
  • A Loss of tail
  • B Underhung jaw
  • C Tentacles anterior to eye and nasolacrimal
    duct.
  • D Reduced of annular scales in annular rings.
  • E Fusion of premax and nasals to add rigidity to
    tip of skull for fossoriality.
  • F Articulation of squamosal and frontals to
    improve rigidity.
  • G Direct devel.
  • H Lat. Compr. Body

19
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