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Lissamphibia

(Subclass)

Overview

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Lissamphibia is a biological subclass of animal that includes all recent amphibians. The name derives from the Latin for smooth amphibia.

Extant amphibians fall into one of three orders ? the Anura (frogs and toads), the Caudata or Urodela (salamanders and newts), and the Gymnophiona or Apoda (the limbless caecilians).

Though the ancestry of each group is unclear, 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 Ma) than had been thought by using the molecular clock alone.1]

Characteristics

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Some, if not all lissamphibia share the following characteristics. Some of these apply to the soft body parts, and hence don't appear in fossils. However, the skeletal characteristics also appear in several types of Palaeozoic amphibians:[2]

Relationships and definition

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Main article: Labyrinthodontia#Origin of modern amphibians
Three hypotheses of Lissamphibian origin: 1 - derived from lepospondyls, 2 - derived from temospondyls and 3 - bipyletic
Reconstruction of Gerobatrachus, possible ancestor of salamanders and frogs

The features uniting the Lissamphibia were first noted by Ernst Haeckel.[2][3] In the early to mid 20th cetury, a bipyletic origin of amphibians (and thus of tetrapods in general) was favoured.[4][5] In the late 20th century, a flood of new fossil evidence mapped out in some detail the nature of the transition between the elpistostegalid fish and the early amphibians, most paleontologists no longer accept the diphyletic view.[6] Whilst the monophyly of the Lissamphibia is accepted by most 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 paleontologists are convinced that the lissamphibia are indeed a natural group, as the various characteristics are also shared with some Palaeozoic amphibians, and it is still possible that these characteristics evolved independently.

Currently there are three prevailing theories of Lissamphibian origin:

Most molecular studies of extant amphibians support monophyly for caecilians, frogs, and salamanders, and the most recent molecular study based on multi-locus data suggest a Late Carboniferous - Early Permian origin of modern amphibians.[7][8]

b>Lissamphibia is a biological subclass of animal that includes all recent amphibians. The name derives from the Latin for smooth amphibia.

Extant amphibians fall into one of three orders ? the Anura (frogs and toads), the Caudata or Urodela (salamanders and newts), and the Gymnophiona or Apoda (the limbless caecilians).

Though the ancestry of each group is unclear, 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 Ma) than had been thought by using the molecular clock alone.1]

Characteristics

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Some, if not all lissamphibia share the following characteristics. Some of these apply to the soft body parts, and hence don't appear in fossils. However, the skeletal characteristics also appear in several types of Palaeozoic amphibians:[2]

Relationships and definition

[ Back to top ]
Main article: Labyrinthodontia#Origin of modern amphibians
Three hypotheses of Lissamphibian origin: 1 - derived from lepospondyls, 2 - derived from temospondyls and 3 - bipyletic
Reconstruction of Gerobatrachus, possible ancestor of salamanders and frogs

The features uniting the Lissamphibia were first noted by Ernst Haeckel.[2][3] In the early to mid 20th cetury, a bipyletic origin of amphibians (and thus of tetrapods in general) was favoured.[4][5] In the late 20th century, a flood of new fossil evidence mapped out in some detail the nature of the transition between the elpistostegalid fish and the early amphibians, most paleontologists no longer accept the diphyletic view.[6] Whilst the monophyly of the Lissamphibia is accepted by most 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 paleontologists are convinced that the lissamphibia are indeed a natural group, as the various characteristics are also shared with some Palaeozoic amphibians, and it is still possible that these characteristics evolved independently.

Currently there are three prevailing theories of Lissamphibian origin:

Most molecular studies of extant amphibians support monophyly for caecilians, frogs, and salamanders, and the most recent molecular study based on multi-locus data suggest a Late Carboniferous - Early Permian origin of modern amphibians.[7][8]

References

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  1. ^ a b Anderson J.S., Reisz R.R., Scott D., Fr?bisch N.B., Sumida S.S. (2008). "A stem batrachian from the Early Permian of Texas and the origin of frogs and salamanders". Nature 453 (7194): 515?518. doi:10.1038/nature06865. PMID 18497824. 
  2. ^ a b Trueb, William E. Duellman, Linda Trueb ; illustrated by Linda (1994). Biology of amphibians (Johns Hopkins pbk. ed. ed.). Baltimore: Johns Hopkins University Press. ISBN 080184780X. 
  3. ^ Haeckel, E (1866): Generelle Morphologie der Organismen : allgemeine Grundz?ge der organischen Formen-Wissenschaft, mechanisch begr?ndet durch die von C. Darwin reformirte Decendenz-Theorie. Berlin
  4. ^ S?ve-S?derbergh, G. (1934). Some points of view concerning the evolution of the vertebrates and the classification of this group. Arkiv f?r Zoologi 26A: pp 1-20
  5. ^ von Huene, F. (1956): Pal?ontologie und Phylogenie der niederen Tetrapoden, G. Fischer, Jena
  6. ^ Gordon, M.S. and Long, J.A. (2004): The Greatest Step In Vertebrate History: A Paleobiological Review of the Fish-Tetrapod Transition. Physiological and Biochemical Zoology no 77(5): pp 700-719. article
  7. ^ Sigurdsen T., Green D.M. (2011). "The origin of modern amphibians: a re-evaluation". Zoological Journal of the Linnean Society 162 (2): 457?469. doi:10.1111/j.1096-3642.2010.00683.x. 
  8. ^ San Mauro, D. (2010) A multilocus timescale for the origin of extant amphibians. Molecular Phylogenetics and Evolution 56: 554-561

External links

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Taxonomy

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The Subclass Lissamphibia is a member of the Class Amphibia. Here is the complete "parentage" of Lissamphibia:

The Subclass Lissamphibia is further organized into finer groupings including:

Orders

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Allocaudata

[more]

Anura

Frogs are amphibians in the order Anura (meaning "tailless", from Greek an-, without + oura, tail), formerly referred to as Salientia (Latin salere (salio), "to jump"). Most frogs are characterized by a short body, webbed digits (fingers or toes), protruding eyes, bifid tongue and the absence of a tail. Frogs are widely known as exceptional jumpers, and many of the anatomical characteristics of frogs, particularly their long, powerful legs, are adaptations to improve jumping performance. Due to their permeable skin, frogs are often semi-aquatic or inhabit humid areas, but move easily on land. They typically lay their eggs in puddles, ponds or lakes, and their larvae, called tadpoles, have gills and tails to develop in water. Adult frogs follow a carnivorous diet, mostly of arthropods, annelids and gastropods. Frogs are most noticeable by their call, which can be widely heard during the night or day, mainly in their mating season. [more]

Caudata

Salamander is a common name of approximately 550 extant species of amphibians. They are typically characterized by a superficially lizard-like appearance, with 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. Unique among vertebrates, they are capable of regenerating lost limbs, as well as other body parts. [more]

Gymnophiona

The caecilians are an order (Gymnophiona) of amphibians that superficially resemble earthworms or snakes. They mostly live hidden in the ground, making them the least familiar order of amphibians. All extant caecilians and their closest fossil relatives are grouped as the clade Apoda. They are mostly distributed in the tropics of South and Central America, Africa, and South Asia. The diet of caecilians is not well known. [more]

Proanura

[more]

Urodela

Salamander is a common name of approximately 550 extant species of amphibians. They are typically characterized by a superficially lizard-like appearance, with 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. Unique among vertebrates, they are capable of regenerating lost limbs, as well as other body parts. [more]

At least 18 species and subspecies belong to the Order Urodela.

More info about the Order Urodela may be found here.

References

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  1. ^ a b Anderson J.S., Reisz R.R., Scott D., Fr?bisch N.B., Sumida S.S. (2008). "A stem batrachian from the Early Permian of Texas and the origin of frogs and salamanders". Nature 453 (7194): 515?518. doi:10.1038/nature06865. PMID 18497824. 
  2. ^ a b Trueb, William E. Duellman, Linda Trueb ; illustrated by Linda (1994). Biology of amphibians (Johns Hopkins pbk. ed. ed.). Baltimore: Johns Hopkins University Press. ISBN 080184780X. 
  3. ^ Haeckel, E (1866): Generelle Morphologie der Organismen : allgemeine Grundz?ge der organischen Formen-Wissenschaft, mechanisch begr?ndet durch die von C. Darwin reformirte Decendenz-Theorie. Berlin
  4. ^ S?ve-S?derbergh, G. (1934). Some points of view concerning the evolution of the vertebrates and the classification of this group. Arkiv f?r Zoologi 26A: pp 1-20
  5. ^ von Huene, F. (1956): Pal?ontologie und Phylogenie der niederen Tetrapoden, G. Fischer, Jena
  6. ^ Gordon, M.S. and Long, J.A. (2004): The Greatest Step In Vertebrate History: A Paleobiological Review of the Fish-Tetrapod Transition. Physiological and Biochemical Zoology no 77(5): pp 700-719. article
  7. ^ Sigurdsen T., Green D.M. (2011). "The origin of modern amphibians: a re-evaluation". Zoological Journal of the Linnean Society 162 (2): 457?469. doi:10.1111/j.1096-3642.2010.00683.x. 
  8. ^ San Mauro, D. (2010) A multilocus timescale for the origin of extant amphibians. Molecular Phylogenetics and Evolution 56: 554-561

External links

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Sources

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Last Revised: August 24, 2012
2012/08/24 13:07:27