ZOO 2090 Lecture Notes - Lecture 10: Stratum Basale, Sacrum, Lissamphibia
1 May 2018
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ZOO2090 – Modern Amphibians: Lissamphibia
Groups:
• Salamanders and newts
• Anurans (frogs and toads)
• Caecilians
Skin
• Thin stratum corenum (respiration; keratinized protection)– epidermis – stratum
germinativum – stratum spongiosum (mucous and granular glands)
• Mucous glands secrete mucus, helps with cutaneous respiration
• Granular glands secrete poisonous alkaloid compounds involved in defense
• Skin is thin to allow gas exchange but the more terrestrial beings are more keratinized to
protect against desiccation
• Only some caecilians and toads have bone elements in the dermis
Metamorphosis
• Terrestrial adult lays eggs in water aquatic larva
• Direct development may occur in some species
Padicellate Teeth
• Tooth has suture dividing base (pedicel) from tip (crown)
• Unique to amphibians in modern forms, also seen I some temnospondyls
• *see structure
Order: Anura (frogs)
• Main characters:
o absence of tail in adults
o jump for locomotion
o tympanum usually present (hearing)
o fertilization is external, except in Ascaphus
• Skull:
o Flattened and open with big jaws
o The palate is highly reduced, eyeballs drop into the oral cavity
o The hyomandibula becomes the first ear bone (the stapes)
• Axial Skeleton:
o Shortened vertebral column (<9 vertebrae)
o Atlas-skull junction forms movable joint through two condyles (can only move up
and down) improved mobility of head in dorsoventral axis
o Post sacral vertebrae is fused into a rod-shaped urostyle lying between two
elongated illium bones of the pelvic girdle
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