Overview
The Lissamphibia includes all recent amphibians and means smooth amphibia.
Extant amphibians fall into one of three orders—the Anura (frogs, including toads), the Caudata or Urodela (salamanders, including newts), and the Gymnophiona or Apoda (the limbless caecilians). Although the ancestry of each group is controversial, all share certain common characteristics, which indicates they evolved from a common ancestor and so form a clade. The publication of a Permian-period stem form Gerobatrachus hottoni showed the frogs and salamanders had a common ancestor more recently (ca 290 Mya) than had been thought by using the molecular clock alone.
Characteristics
The following characteristics are shared by some, most, or all Lissamphibia. Some of these apply to th e soft body parts and hence not present in fossils. However, those which refer to the skeleton are also known from several types of Palaeozoic amphibians.
- Two types of skin glands (mucous & granular)
- Fat bodies associated with gonads
- Double-channeled sensory papillae in the inner ear
- Green rods (a special type of visual cell, unknown in caecilians)
- Ribs do not encircle body
- Ability to elevate the eye (with levetator bulbi muscle)
- Forced pump respiratory mechanism
- Cylindrical centra (the main body of the vertebra; cylindrical centra are also found in several groups of early tetrapods)
- Pedicellate teeth (the crown of the teeth is separated from the root by a zone of fibrous tissue; also found in some Dissorophoidea; the teeth of some fossil salamanders are not pedicellate)
- Bicuspid teeth (two cusps per tooth, also found in juvenile dissorophoids)
- Operculum (small bone in the skull, linked to shoulder girdle by the opercularis muscle; perhaps involved in hearing and balance; absent in caecilians and some salamanders, fused to the stapes (ear bones) in most anurans)
- Loss of posterior skull bones (also in Microsauria and Dissorophoidea)
- Small, widely separated pterygoids (also found in Temnospondyli and Nectridea)
- Wide cultriform process of the parasphenoid (also found in some Microsauria (Rhynchonchos) and Lysorophia)
- Double or paired occipital condyle
Relationships and Definition
Whilst the monophyly of the Lissamphibia is accepted by many herpetologists and paleontologists, the origin and relationships of the various Lissamphibian groups both with each other and among other early tetrapods remains controversial. Not all paleontologist s are convinced that the lissamphibia are indeed a natural group, as the various characteristics are also shared with some Paleozoic amphibians, and it is still possible that these characteristics evolved independently.
Currently there are three prevailing theories of Lissamphibian origin:
- Monophyletic within the temnospondyli
- Monophyletic within lepospondyli
- Diphyletic (two separate ancestries) with apodans within the lepospondyls and salamanders and frogs within the temnospondyli.
Photos
Taxonomy
The Subclass Lissamphibia is a member of the Class Amphibia. Here is the complete "parentage" of Lissamphibia:
- Domain: Eukaryota
Whittaker & Margulis,1978 - eukaryotes
- Kingdom: Animalia
Linnaeus, 1758 - animals
- Subkingdom: Bilateria
(Hatschek, 1888) Cavalier-Smith, 1983 - bilaterians
- Branch: Deuterostomia
Grobben, 1908 - Deuterostomes
- Infrakingdom: Chordonia
(Haeckel, 1874) Cavalier-Smith, 1998
- Phylum: Chordata
Bateson, 1885 - Chordates
- Subphylum: Vertebrata
Cuvier, 1812 - Vertebrates
- Infraphylum: Gnathostomata
Auct. - Jawed Vertebrates
- Superclass: Tetrapoda
Goodrich, 1930 - Tetrapods
- Class: Amphibia
(am-FIB-ee-uh)
C. Linnaeus, 1758
- Subclass: Lissamphibia Haeckel, 1866
- Class: Amphibia
(am-FIB-ee-uh)
C. Linnaeus, 1758
- Superclass: Tetrapoda
Goodrich, 1930 - Tetrapods
- Infraphylum: Gnathostomata
Auct. - Jawed Vertebrates
- Subphylum: Vertebrata
Cuvier, 1812 - Vertebrates
- Phylum: Chordata
Bateson, 1885 - Chordates
- Infrakingdom: Chordonia
(Haeckel, 1874) Cavalier-Smith, 1998
- Branch: Deuterostomia
Grobben, 1908 - Deuterostomes
- Subkingdom: Bilateria
(Hatschek, 1888) Cavalier-Smith, 1983 - bilaterians
- Kingdom: Animalia
Linnaeus, 1758 - animals
The Subclass Lissamphibia is further organized into finer groupings including:
- Infraclass (1): Pterygota
- Order (6): Allocaudata · Anura · Caudata · Gymnophiona · Proanura · Urodela
Orders
Allocaudata
Anura
Frogs are in the order Anura (meaning "tail-less", from Greek an-, without + oura, tail), formerly referred to as Salientia (Latin saltare, to jump). The name frog derives from Old English frogga, (compare Old Norse frauki, German Frosch, older Dutch spelling kikvorsch), cognate with Sanskrit plava (frog), probably deriving from Proto-Indo-European praw = "to jump". [more]
Caudata
Salamander is a common name of approximately 500 of amphibians. They are typically characterized by their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant species are grouped together as the Urodela. Most salamanders have four toes on their front legs and five on their rear legs. Their moist skin usually makes them reliant on habitats in or near water, or under some protection (e.g., moist ground), often in a wetland. Some salamander species are fully aquatic throughout life, some take to the water intermittently, and some are entirely terrestrial as adults. Uniquely among vertebrates, they are capable of regenerating lost limbs, as well as other body parts. [more]
Gymnophiona
The caecilians (sg. pronounced ) are an order (Gymnophiona or Apoda) of that superficially resemble earthworms or snakes. They mostly live hidden in the ground, which makes them the least explored order of amphibians, and widely unknown. [more]
Proanura
Urodela
Salamander is a common name of approximately 500 of amphibians. They are typically characterized by their slender bodies, short noses, and long tails. All known fossils and extinct species fall under the order Caudata, while sometimes the extant species are grouped together as the Urodela. Most salamanders have four toes on their front legs and five on their rear legs. Their moist skin usually makes them reliant on habitats in or near water, or under some protection (e.g., moist ground), often in a wetland. Some salamander species are fully aquatic throughout life, some take to the water intermittently, and some are entirely terrestrial as adults. Uniquely among vertebrates, they are capable of regenerating lost limbs, as well as other body parts. [more]
At least 1,034 species and subspecies belong to the Order Urodela.
More info about the Order Urodela may be found here.
References
- Benton, M. J. (2005), Vertebrate Paleontology, 3rd ed. Blackwell Science Ltd
- Carroll, RL (1988), Vertebrate Paleontology and Evolution, WH Freeman & Co.
- San Mauro, Diego; Miguel Vences, Marina Alcobendas, Rafael Zardoya and Axel Meyer (May 2005). "Initial diversification of living amphibians predated the breakup of Pangaea" ([dead link] – Scholar search). American Naturalist 165: 590–599. doi:
Sources
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