Extant Amphibia

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Extant Amphibia

• Caecilians and Urodeles

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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Plethodontid forms

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

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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.

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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).

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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.

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Caecilians

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

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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

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