Acanthodii

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Acanthodii
Live reconstruction of Nerepisacanthus denisoni

Live reconstruction of Nerepisacanthus denisoni

Temporal occurrence
Untersilur to Sakmarium ( Perm )
440 to 290.1 million years
Locations
  • worldwide
Systematics
Neumünder (Deuterostomia)
Chordates (chordata)
Vertebrates (vertebrata)
Jaw mouths (Gnathostomata)
Acanthodii
Scientific name
Acanthodii
Owen , 1846

The Acanthodii are a class of extinct, very diverse fish. Systematically they belong to the superclass jaw mouths (Gnathostomata) and are the sister group of the bony fish (Osteichthyes), with which they form the taxon Teleostomi . They are the first fossilized Gnathostomata and lived from the Silurian to the Permian . They flourished in Devon . Individual fossilized spines and scales (so-called ichthyodoruliths ) have already been found from the Lower Silurian, reliable, well-preserved finds from this period are still unknown. The often used German name "Stachelhaie" means no close relationship, but only refers to the shark-like appearance of many Acanthodians with the typical feature that the membranous fins were supported on their front edge by a stinger.

features

The Acanthodii were 8 cm to 2.5 meters long and were found in the sea, but mainly in fresh water. Their inner skeleton was made of cartilage, but the brain skull was made of a piece of bone (albeit with deep cartilage bays - but without joints). The head and body were covered with small scales. Some species had gill covers made of bony "radii". All species had jaws , but teeth were often missing. When present, they often only sat on the lower jaw. The toothless genera ( e.g. Acanthodes ) are considered pelagic filter feeders. The hyoid arch was initially interpreted as a "normal gill arch", but more detailed investigations (Miles 1973) showed that it supported the jaw arch as in sharks , rays and bony fish ; the spray hole was often between the two . On the other hand, there was as yet no pharyngeal with fangs . The Unpaarflossen had no own finned , but sat on prolonged neural or Hämalfortsätzen (on the notochord ). The small pair fins were sometimes independent of the ventral rows of spines. The shoulder girdle was weak. The fins had no rays yet, just scales for support. The eyes were set far forward and had scleral rings; the nasal organs must have been small, but there were already two narins (nostrils).

Systematics (incomplete)

The Ischnacanthiformes and Climatiiformes can already be found in the Silurian, while the Acanthodiformes are only known from the Lower Devonian.

Climatiiformes

Diplacanthus longispinus in the Museum für Naturkunde , Berlin

Except for the Diplacanthides, they had many jaw teeth.

Ischnacanthiformes

Acanthodiformes

Vonu: Mesacanthus , Parexus and Ischnacanthus , three life forms of Devonian Acanthodii

All Acanthodiformes had only one dorsal fin, while the Climatiiformes and the Ischnacanthiformes each have two. They were probably filter feeders, mostly there are no teeth.

  • Acanthodidae family
    • Acanthodes Lower Carboniferous to Lower Permian, localities: Europe, North America, Australia, South Africa, East Asia
    • Cheiracanthus Middle Devonian, localities: Europe
    • Homalacanthus Upper Devonian to Lower Carboniferous, localities: North America, Europe
    • Mesacanthus Lower to Middle Devonian, localities: Europe
    • Traquairichthys Upper Devonian to Lower Carboniferous, localities: Europe, North America
    • Triazeugacanthus Upper Devonian, localities: North America

Some genera of uncertain systematic position

  • Onchus Lower Silurian to Lower Devonian, localities: North America and Europe
  • Antarchtonchus Middle and Upper Devonian, localities: Antarctica
  • Monopleurodus Upper Silurian, localities: Europe

annotation

  1. ↑ d. H. fossils of the more primitive Placodermi are only known from the border with the Devonian

literature

  • Robert L. Carroll : Paleontology and Evolution of the Vertebrates. Thieme publishing house, Stuttgart. 1993
  • Frickhinger, Karl Albert: Fossil atlas, fishes Melle: Mergus, Publ. For Natural History and Pet Books Baensch. 1995 ISBN 1-56465-115-0
  • Miles, RS (1973): Relationships of acanthodians.- In: PH Greenwood, RS Miles, and C. Patterson (eds.), Interrelationships of Fishes, 63-103. Supplement 1, Zoological Journal of the Linnean Society, Volume 53, Academic Press, London.
  • Valiukevičius, J. New Wenlock-Pridoli (Silurian) acanthodian fishes from Lithuania. Acta Palaeontologica Polonica 49 (1): page 147-160. (2004)

Web links

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