3 Extant groups of Lissiamphibia1. Anura - Frogs & Toads – 45 families 7000 species2. Urodela (Salamanders) – 8 fam 5503. Gymnophiona (caecilians) – 3 fam 170Batrachia = (Anura, Urodela)Lissamphibia = gymnophiona (anura, urodela)Anura – frogs & toads MOST ABUNDANT tetrapod group-most diverse in tropics - majority terrestrial as adultsSkeleton: Defining Characteristics associated w/ jumping Tailless as adults Short vertebral column (w/ few presarcal vertebrae) Long hind limbs & toes Modified sarcal area – Urostyle Massive mouths Almost all lack teeth on the lower jawFrog vs Toad – frogs can jump long distances, have long legs & smooth skin - Toads – get around using short hops instead of long leaps, relatively short legs & warty skin are traditionally referred to as toadsThese morpho-types have evolvednumerous times independently indifferent anuran lineages and so thenames frogs and toads do not refer tomonophyletic groupsUrodela/ Caudata – salamanders1. N hemisphere2. Majority adult terr. But many full aqua.3. UNLIke aquatic anurans, the majority of aquatic salamanders retain larval characteristics & are referred to as paedomorphic or neotenicSkeleton1. diff from anurans but similar to early terr. Tetra’s2. long tail3. short fore & hindlimbs4. long vertebral column5. sacral area unmodified6. also have teeth in upper & lower jawsPaedomorphosis – larve become sexually mature w/o attaining adult body formFor salamanders: 2 Diff Kinds1. Obligate neotenes – remain neotenic throughout entire lifecycle – keep gills never become adulta. Ex: mudpuppies (necturidae) & Sirens (Sirenidae)2. Facultative neotenes – can choose whether remain neotenic or to metamorphose into terrest. Adult – depending on conditionsa. Ex: North Am. Salamanders of genus AmbystomaGymnophiona (caecilians)1. Tropical no NA2. Terrestrial (burrowing) & aquatic forms3. All legless, reduced eyes, solid craniums – for burrowing4. Large rings ANNULI around bodies make em looklike earthwormsSkeleton: 1. Modern caecilians are legless but earliest fossil had legs (eocaecilia)2. short tail or no tail 3. Teeth in upper & lower jaws4. The skull is a solid box – facilitates burrowingRelation b/w the 3SYNAPOMORPHIES TO SUPPORT AMPHIBIAN MONOPHYLYFeatures related to skin, transmission of sound to theinner ear, structure of the eyes & structure of the teeth (pedicellate teeth)1. All amphibians also have poison (granular) glands in the skin2. Papilla Amphobiorum. All amphibians have a special sensory area, the papilla amphibiorum in the wall of the sacculus of the inner ear. The Papilla amphibiorum is sensitive to freq below 1000 hz and a second sensory area the Papilla Basilaris, detects sound frequencies above 1000 hz3. Pedicellate teeth – Nearly all modern amphibianshave teeth in which the crown & base (pedicel) are composed of dentine & are separated by a narrow zone of uncalcified dentine or fibrous connective tissue. A few amphibians lack pedicellate teeth & the boundary b/w the crown& base is obscured in some other genera. These teeth also occur in some actinopterygian fishes & are not thought to be related to amphibians4. Structure of the levator bulbi muscle – muscle is a thin sheet in the floor of the orbit that is innervated by the 5th cranial nerve. It causes the eyes to bulge outward, thereby enlarging the buccal cavity. This muscle is salamanders & anurans & in modified form of caeciliansRelation hypotheses1. anurans & caudates sister groups (a group referred to as batrachia) with the caecilians forming the sister group to the Batrachia (i.e that modern amphibians are monophyletic) & derived from a group of temnospondyl tetrapods2. others suggest the batrachian amphibians (salamanders & anurans) are derived from the temnospondyls and that caecilians are derived from a completely unrelated group of lepospondyl tetrapods – i.e. that modern amphibians are not monophyleticFossil Record1. early amphibian fossil record is poor 2. Oldest fossils that can be identified as belonging to any of the extant groups date back to the Permian & are represented only by vertebrae2. All extant groups present by JurassicAmphibian skin: Moist & permeable1. most noted2. lissamphibia refers to texture of skin (greel Liss = smooth) refers to modern amphibians being diff from early tetras which were covered in dermal armor like fishes3. Skina. Thin epidermal layerb. Highly vascularizedc. Different types of multicellular glandsi. Mucus glandsii. Poison glandsiii. Hedonic glandsI. Skin highly vascularizeda. Large capillary beds close to the surface, just below thin epidermisb. Skin is actually involved in respiration (cutaneous respiration) & the thin epidermis facilitates gas exchangeII. Different glands in skina. Mucus glands produce mucusb. Poison glands capable of producing irritable to extremely toxic substances c. Hedonic glands which are involved in pheromone productionPoison Glands- poisons – unpleasant/puke to extremely toxic & include biogenic amines, peptides proteins w/ hemolytic properties alkaloids etc- Named after amphibian group from which they were first described (ex bufotoxin from bufonidae)- These substances may be distributed evenly across the surface of skin or more in an area ex: poison sac- APOSEMATIC (warning) coloration & behaviors typically advertise distasteful properties- Cryptal dorsal color – camouflage sometimes combined w/ aposematic – only revealed when threatenedPhyllobates terribilis – thought to be the most toxicfrogCutaneous respiration1. complicated – gills young vs lungs adult2. major changes to circulatory system take place during metamorphosis3. one common theme in amphibian respiration is the role of the skin both larvae & adults rely on the skin surface for gas exchange4. The proportion of O2 obtained via cutaneous repiration varies across groupsa. Majority of anurans rely on lungs for O2 requirements as adults – esp during periods of high energy uptake (mating)b. Some fully aquatic anurans rely almost exclusively on the skin for gas exchange (even though have lungs)c. –numerous species known to lack lungs entirely (only tetras lacking lungs) – solely on cutaneous repirationLUNG LOSS3 separate times in history- once in urodela ----common ancestor of the Plethodontidae- Once in gymnophonia – 2 species of caecilians known to lack lungs- Once in anuraLunglessness is known only from amphibians amongst the tetrapodsMay be