Lepospondyli

Lepospondyli
The microsaur Pelodosotis elongatum , graphic reconstruction
Temporal occurrence
Carbon to Permian
326.5 to 251 million years
Locations
North America, Europe, North Africa
Systematics
Chordates (chordata) Jaw mouths (Gnathostomata) Vertebrates (vertebrata) Land vertebrates (Tetrapoda) Lepospondyli
Scientific name
Lepospondyli
Zittel , 1888

The Lepospondyli ("Hüllen- or Hülsenwirbler") are an extinct group of amphibian-like, primitive and morphologically very diverse terrestrial vertebrates (Tetrapoda). Fossil remains of the Lepospondyli were found almost exclusively in North America and Europe, only the Nectridea are also known from North Africa.

features

In contrast to the mostly large and heavily built Temnospondyli , the Lepospondyli are rather small, most forms were only 10 to 20 cm long, and are similar to today's tail or sneak amphibians . Her skeleton was only weakly ossified. The enamel layers of their strong teeth were not folded like a labyrinth , their snouts were short, their skulls were compact. The rear edge is straight, an ear slit is missing. The ribs were long and curved. The eponymous and most important common feature are the spindle-shaped vertebrae . This shape of the vertebral bodies could be an adaptation to the small body size and thus a reduction feature. In this case, the lepospondyli could be descended from various primitive land vertebrates of the Upper Devonian or Mississippian ("Lower Carboniferous") and their monophyly is therefore questionable.

Systematics

In the traditional system , they are listed as a subclass of amphibians , but the relationship to today's amphibians is unclear. The Lepospondyli could be their sister group , but they could also be a non-monophyletic association of core group representatives of the amphibians. At present, however, there is more evidence that they belong as a basal branch to the trunk group of the Amniota . After a new investigation of the kinship relationships of the early terrestrial vertebrates, a team of scientists comes to the conclusion that Westlothiana is basal to the lepospondyli and forms a clade with them.

Cladogram according to Benton 2007 with addition according to Ruta et al.

• Land vertebrates (Tetrapoda)
  • basal tetrapods
  • † Temnospondyli → (Modern amphibians )
  • unnamed monophylum
    • unnamed monophylum
      • † West Lothiana
      • † Lepospondyli
    • Reptiliomorpha
      • † " Anthracosauria "
      • Batrachosauria
        • † Seymouriamorpha
        • † Diadectomorpha
        • Amniota

Sub-taxa

The nectride Diploceraspis burkei , live reconstruction

The lepospondyli are divided into six subgroups according to anatomical features.

• Aïstopoda
• Nectridea
• Microsauria
• Lysorophidae
• Adelogyrinidae
• Acherontiscidae

literature

• Robert L. Carroll : Paleontology and Evolution of the Vertebrates , Thieme, Stuttgart (1993), ISBN 3-13-774401-6
• Wilfried Westheide & Reinhard Rieger : Special Zoology Part 2: Vertebrae and Skull Animals , 1st edition, Spectrum Akademischer Verlag Heidelberg • Berlin, 2004, ISBN 3-8274-0307-3
• Robert Reisz: Lepospondyls and Lissamphibians. PDF

Individual evidence

1. ↑ Marcello Ruta, Michael I. Coates & Donald LJ Quickie (2003): Early tetrapod relationships revisited. Biological Reviews, 78, pp 251-345 doi : 10.1017 / S1464793102006103
2. ↑ Michael J. Benton : Paleontology of the vertebrates. 2007, ISBN 3-89937-072-4

Web links

Commons : Lepospondyli  - collection of images, videos and audio files

• Laurin, Michel: Terrestrial Vertebrates. Stegocephalians: Tetrapods and other digit-bearing vertebrates. Version October 13, 2008. in The Tree of Life Web Project