Placodermi

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Placodermi
Bothriolepis panderi from the Devonian region of Novgorod Oblast, northwestern Russia

Bothriolepis panderi from the Devonian region of Novgorod Oblast , northwestern Russia

Temporal occurrence
late Silurian to late Devonian
418.7 to 359.2 million years
Locations
  • Worldwide
Systematics
Neumünder (Deuterostomia)
Chordates (chordata)
Vertebrates (vertebrata)
Jaw mouths (Gnathostomata)
Placodermi
Scientific name
Placodermi
McCoy , 1848

The Placodermi or Placodermata ('plate skin'), also panzerfish , are an extinct class of fish-like jaw - bearing vertebrates (Gnathostomata). They lived in the ancient times (Paleozoic) of the Upper Silurian and had their heyday in the following Devonian , but they died out again at the end of this period. The early Placodermi were freshwater inhabitants, only later did they also colonize the sea.

It is characteristic of the Placodermi that the head and trunk were armored with bone plates made of Cosmin , a dentin-like supporting tissue. The largest form was the Arthrodire Dunkleosteus , which was up to 10 meters long.

The Placodermi were the first vertebrates to develop jaws . It is believed that these developed from bones in the pharynx that previously supported the gill arches of the jawless fish . The gills were each supported by an upper and lower interconnected bone arch. So the step to the jointed jawbones was not far. However, the development of the pine is not documented in the fossil record .

Viviparia was detected for the first time in the Upper Devonian Australian placoderma Materpiscis attenboroughi , which belongs to the Ptyctodontida . A year later, viviparia was also discovered in the placoderm Incisoscutum ritchiei , which belongs to the Arthrodira .

Important sites in Germany are Blauer Bruch and Schmidts Bruch in the Ense area near Bad Wildungen , as well as the slate from the mines of Bundenbach ( Bundenbach slate ) and Gemünden in the Hunsrück . Well-preserved Placodermi from the Hunsrück schist sea of the Devonian period, such as Gemuendina and Lunaspis, can be seen in the Castle Park Museum in Bad Kreuznach in Rhineland-Palatinate .

Sub-taxa

Live reconstruction (model) of Bothriolepis canadensis

Individual evidence

  1. ↑ Long, JA et al. Life birth in the Devonian period. Nature 453: 650-653 (2008), doi : 10.1038 / nature06966
  2. ↑ Long, YES. et al .: Devonian arthrodire embryos and the origin of internal fertilization in vertebrates. Nature 457: 1124-1127 (2009), doi : 10.1038 / nature07732

Web links

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