Psephoderma

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Psephoderma
Psephoderma alpinum in the American Museum of Natural History

Psephoderma alpinum in the American Museum of Natural History

Temporal occurrence
Upper Triassic ( Norium - Rhaetium )
228 to 201.3 million years
Locations
Systematics
Amniotes (Amniota)
Sauropsida
Diapsida
Sauropterygia
Placodontia
Psephoderma
Scientific name
Psephoderma
Meyer , 1858
species
  • P. alpinum Meyer, 1858

Psephoderma ( Greek f1 for "pebble skin" from ψῆφος psepho "pebble" and δέρμα derma "skin") is an extinct genus of placodons . Psephoderma reached a total length of up to 1.25 meters. As a representative of the Placochelyidae , like other genera of this family, it has a body armor thatat first glance resembles thatof turtles . Most of the specimens come from the Upper Triassic of the Zorziner limestone near Bergamo in the Italian Alps ( Bergamasque Alps ).

features

The body of Psephoderma is flattened dorso-ventrally. The back armor consists of sturdy hexagonal osteoderms . In the anterior tail area, another plate covers the posterior pelvic region, with the posterior extremities in between. The belly is not protected by a uniform armor, but strongly pronounced belly ribs offer protection here. The skull is just as low and extremely pointed in front. The extremities are small compared to the body and the tail is very long. The rear extremities are more pronounced.

Way of life

Thanks to numerous finds, Psephoderma is one of the best-known placodons . The morphology of the skeleton indicates a preferred way of life in the shallow sea. The poorly ossified extremities confirm this. Psephoderma was certainly a slow swimmer who might only come ashore to lay eggs. Indications that Psephoderma was still slightly adapted to short-term shore excursions are the arrangement of the pelvis and the shoulder girdle. There are also nails on the fingers of the hand and feet. When swimming, the rear extremities were responsible for propulsion. Overall, a way of life that is strongly related to shallow seabeds can be assumed. So Psephoderma looked for food in the mud with its pointed snout and was well protected from attacks from above by its armor.

Systematics

The superfamily of the Cyamodontoidea is divided into the Cyamodontida and the Placochelyida . Psephoderma belongs to Neenan, et al. (2015) on the Placochelyida. The following phylogenetic tree comes from the same scientific work that uses skull features as an aid.

 Placochelyida  

 Protenodontosaurus


   

 Macroplacus


   

 Psephochelys


  Placochelyidae  

 Psephoderma


   

 Glyphoderma


   

 Placochelys





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Geography and stratigraphy

Most of the finds come from the northern Italian region of Bergamo , Brescia and Udine (Zorziner Kalk, or Dolomia di Forni). Psephoderma was known here from the Norium and the Rhaetium . Furthermore, a find from the Älplihorn unit ( Kössen strata ) of the late Norian to early Rhaetian near Schesaplana (Switzerland / Austrian border) was reported. Psephoderma was first described in Germany . Meyer (1858) reports this genus from the Kössen strata of the Rhaetium near the Winklmoos Alm in the Bavarian Alps . From England may not be diagnostic groups are derived from psephoderma . In Austria was psephoderma in Rodaun In Vienna found. Here, too, the remains come from the rhaetium / norium border area

Psephoderma alpinum carapace
Reconstruction of Psephoderma

Selection of museums with copies

Italy

Sources and References

literature

Web links

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

Individual evidence

  1. ↑ a b O. Rieppel: The Dermal Armor of the Cyamodontoid Placodonts (Reptilia, Sauropterygia): Morphology and Systematic Value. In: Geology, New Series 46, 2002, pp. 1-41. doi: 10.5962 / bhl.title.3275
  2. ↑ a b c d e f G. Pinna & S. Nosotti: Anatomia, morfologia funzionale e paleoecologia del rettile placodonte Psephoderma alpinum MEYER, 1858 In: Memorie Società Italiana di Scienze Naturali, Museo di Storia Naturale Milano 25, 1989, p. 17 -49.
  3. ^ D. Naish: Fossils explained 48. Placodonts. In: Geology Today 20 (4), 2004, pp. 153-158. Available online (accessed October 23, 2015)
  4. ↑ a b J.M. Neenan & TM Scheyer: New specimen of Psephoderma alpinum (Sauropterygia, Placodontia) from the Late Triassic of Schesaplana Mountain, Graubünden, Switzerland In: Swiss Journal of Geosciences 107, 2014, pp. 349-357. doi: 10.1007 / s00015-014-0173-9
  5. ↑ a b H. Zapfe: A large ichthyosaur from the Kössen layers of the Northern Alps In: Annalen des Naturhistorisches Museum in Wien 80, 1976, pp. 239–250. Available online (accessed October 23, 2015)
  6. ^ A b H. von Meyer: Psephoderma Alpinum from the Dachstein limestone of the Alps. In: New yearbook for mineralogy, geognosy, geology and petrefactuality , 1858, pp. 646–650
  7. ↑ http://dipbsf.uninsubria.it/paleo/psephoderma1.htm (accessed October 29, 2015)
  8. ↑ JM Neenan, C. Li, O. Rieppel & TM Scheyer: The cranial anatomy of Chinese placodonts and the phylogeny of Placodontia (Diapsida: Sauropterygia) In: Zoological Journal of the Linnean Society 175 (2), 2015, p. 415– 428 doi: 10.1111 / zoj.12277
  9. ↑ H. v. Meyer: Communication to Professor HB Geinitz. In: New year book for mineralogy, geognosy, geology and petrefactuality 1864, pp. 698–701.