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Lissamphibia

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Title: Lissamphibia  
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Subject: Tetrapod, Amphibian, Temnospondyli, Taxobox/testcases, List of transitional fossils
Collection: Amphibians, Early Triassic First Appearances
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Lissamphibia

Lissamphibians
Temporal range: Early TriassicPresent (Possible Cisuralian record)
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Emerald glass frog (Centrolene prosoblepon)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Subclass: Lissamphibia
Haeckel, 1866
Subgroups

Batrachia
Gymnophiona

The Lissamphibia are a group of tetrapods that includes all modern amphibians. Lissamphibians consist of three living groups: the Salientia (frogs, toads, and their extinct relatives), the Caudata (salamanders, newts, and their extinct relatives), and the Gymnophiona (the limbless caecilians and their extinct relatives). A fourth group, the Allocaudata, was moderately successful, spanning 160 million years from the Middle Jurassic to the Early Pliocene, but became extinct 3.6 million years ago.

For several decades, this name has been used for a group that includes all living amphibians, but excludes all the main groups of Paleozoic tetrapods, such as Temnospondyli, Lepospondyli, Embolomeri, and Seymouriamorpha.[1] Some scientists have concluded that all of the primary groups of modern amphibians, the frogs, salamanders, caecilians are closely related, but others[2] hold that frogs and salamanders evolved from temnospondyls, while caecilians evolved from lepospondyls, so Lissamphibia is polyphyletic with respect to other tetrapods.

Some writers have argued that the early Permian dissorophoid Gerobatrachus hottoni is a lissamphibian.[2] If it is not,[3] the earliest known lissamphibians are Triadobatrachus and Czatkobatrachus from the Early Triassic.[4][5]

Contents

  • Characteristics 1
  • Relationships and definition 2
  • References 3
  • Bibliography 4
  • External links 5

Characteristics

Reconstruction of Gerobatrachus, possible ancestor of salamanders and frogs

Some, if not all, lissamphibians share the following characteristics. Some of these apply to the soft body parts, hence do not appear in fossils. However, the skeletal characteristics also appear in several types of Palaeozoic amphibians:[6]

Relationships and definition

The features uniting the Lissamphibia were first noted by Ernst Haeckel, even though in Haeckel's work, Lissamphibia excluded the caecilians.[6][7] Nevertheless, Haeckel considered the caecilians to be closely related to what he called Lissamphibia (which is now called Batrachia and includes frogs and salamanders). In the early to mid 20th century, a biphyletic origin of amphibians (and thus of tetrapods in general) was favoured.[8][9] 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 view that amphibians have arisen twice, from two related but separate groups of fish.[10] With the single origin of amphibians being accepted by most herpetologists and paleontologists, it was assumed that Lissamphibia was monophyletic as well. However, the origin and relationships of the various lissamphibian groups both with each other and among other early tetrapods remains controversial. Not all paleontologists today are convinced that Lissamphibia is indeed a natural group, as there are important characteristics shared with some non-lissamphibian Palaeozoic amphibians.

Currently, the three prevailing theories of lissamphibian origin are:

One of the hypotheses regarding their ancestors is that they evolved by paedomorphosis and miniaturization from early tetrapods.[12]

Recent molecular studies of extant amphibians based on multiple-locus data favor one or the other of the monophyletic alternatives and indicate a Late Carboniferous date for the divergence of the lineage leading to caecilians from the one leading to frogs and salamanders, and an early Permian date for the separation of the frog and salamander groups.[13][14]

References

  1. ^  
  2. ^ a b c Anderson, J.S.; Reisz, R.R.; Scott, D.; Fröbisch, N.B.; Sumida, S.S. (2008). "A stem batrachian from the Early Permian of Texas and the origin of frogs and salamanders" (PDF). Nature 453 (7194): 515–518.  
  3. ^ a b Marjanović, D.; Laurin, M. (2009). "The origin(s) of modern amphibians: a commentary". Evolutionary Biology 36 (3): 336–338.  
  4. ^ Marjanović, D.; Laurin, M. (2007). "Fossils, molecules, divergence times, and the origin of lissamphibians". Systematic Biology 56 (3): 369–388.  
  5. ^ Evans, S. E.; Borsuk-Białynicka, M. (2009). from Poland"Czatkobatrachus"The Early Triassic stem−frog (PDF). Palaeontologica Polonica 65: 79–195;. 
  6. ^ a b Duellman, W. E.; Trueb, L. (1994). Biology of amphibians. illustrated by L. Trueb. Johns Hopkins University Press.  
  7. ^ Haeckel, E. (1866), Generelle Morphologie der Organismen : allgemeine Grundzüge der organischen Formen-Wissenschaft, mechanisch begründet durch die von Charles Darwin reformirte Descendenz-Theorie. Berlin
  8. ^  
  9. ^ von Huene, F. (1956) Paläontologie und Phylogenie der niederen Tetrapoden, G. Fischer, Jena
  10. ^ Gordon, M.S.; Long, J.A. (2004). "The Greatest Step In Vertebrate History: A Paleobiological Review of the Fish-Tetrapod Transition" (PDF). Physiological and Biochemical Zoology 77 (5): 700–719.  
  11. ^ Ruta, M.; Coates, M. I. (2007). "Dates, nodes and character conflict: addressing the lissamphibian origin problem". Journal of Systematic Palaeontology 5 (1): 69–122;.  
  12. ^ "First Land Creatures Had Wild Appearances". LiveScience.com. 
  13. ^ Sigurdsen, T.; Green, D.M. (2011). "The origin of modern amphibians: a re-evaluation". Zoological Journal of the Linnean Society 162 (2): 457–469.  
  14. ^ San Mauro, D. (2010). "A multilocus timescale for the origin of extant amphibians". Molecular Phylogenetics and Evolution 56: 554–561.  

Bibliography

External links

  • Biology 356 - Major Features of Vertebrate Evolution by Dr. Robert Reisz, University of Toronto
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