Osteoglossiformes

Arowana ( Osteoglossum bicirrhosum )

The Knochenzünglerartigen ( Osteoglossiformes ( Gr. " osteon " bone = " glossa " = tongue; Latin, " format " = form) ) are an order of primitive bony fishes Real ( Teleostei ), the disjoint on the southern continents (South America, Africa, South Asia, Australia) is common. It is residual populations in a larger area of ​​distribution in the past, which also Europe, North America, Central and East Asia included. Almost all Knochenzünglerartigen are pure freshwater fish, only some Old World knife-fish go in light brackish water. At the order includes six families, two of which contain only one type, another only four, two more nine and ten, and the richest, the mormyrids with over 210 species accounts for nearly 90 % of the diversity order.

Features

The Knochenzünglerartigen are very different in body shape and lifestyle. They generally have an elongate, laterally flattened body and reach lengths of five centimeters to over one meter. The largest species, the Arapaima ( Arapaima gigas ) is intended for earlier reports that can not be checked, have reached a maximum length of 4.5 meters and would thus be the longest pure freshwater fish. Confirmed are lengths of two meters.

The name derives from the order is the front with well-developed teeth, tongue, and the parasphenoid is dentate. Both form a scissors bite. The Zungenbezahnung lack the Großnilhecht ( Gymnarchus niloticus ) and the African osteoglossid ( Heterotis niloticus ). Since the Parasphenoidzähne with other primitive Teleostei occur ( Plesiomorphie ), they can not be regarded as an autapomorphy of Knochenzünglerartigen. For all species, however, are more teeth on Ectopterygoid and Mesopterygoid ( bones of the wing bone). The premaxilla is small and fixed to the skull connected. The Supramaxillare, a bone of the upper jaw does not exist. The nasal capsule is rigid, one - Antorbital supraorbital system missing to pump water over the olfactory mucosa. Epipleuralia ( bones ) are missing. The butterfly fish ( Pantodon buchholzi ) has an appendix, the other two Knochenzünglerartigen. In addition, one or two Pylorusschläuche present. The caudal fin is supported by 16 branched (only when Arapaima ) or less fin rays. The caudal fin skeleton has two or Uroneuralia, Urodermalia ( covering bones of sunken, merged scales) are missing.

Nutrition

The diet of different Knochenzünglerartigen is very different. Especially the big osteoglossid, knife fish and Großnilhecht are predators that feed primarily on other fish. Osteoglossum species also prey on large insects, frogs and small bats in the jump. The butterfly fish consumed insects and spiders that have fallen on the water surface ( approach food) mormyrids and elephant fish are especially Benthosfresser and look for food on the seabed. The African osteoglossid is a filter feeder, who lives just fine plankton and detritus.

Outer systematics

The Knochenzünglerartigen be reunited with their sister group, the North American moon eyes ( Hiodontiformes ) to the taxon Knochenzünglerähnlichen ( Osteoglossomorpha ). These are considered the most primitive living today genuine bony fish ( Teleostei ).

Inside systematics

The order is divided into two sub-orders and six families. Two families are still grouped into a superfamily.

• Family butterfly fish ( Pantodontidae )
• Subordination Osteoglossoidei Family osteoglossid ( Osteoglossidae )
• Family Arapaimidae

• Family Old World knife fish ( Notopteridae )
• Superfamily Mormyroidea Family mormyrids and elephant fish ( Mormyridae )
• Family Großnilhecht ( Gymnarchidae )

Phylogeny

The following cladogram shows the relationship of the Osteoglossiformes among themselves, as well as Lycoptera and Hiodontiformes as outgroups. Controversial is the position of the butterfly fish.

Lycoptera †

Hiodontiformes

Butterfly fish ( Pantodontidae )

Butterfly fish ( Pantodontidae )

Arapaimidae

Osteoglossid ( Osteoglossidae )

Old World knife fish ( Notopteridae )

Großnilhecht ( Gymnarchidae )

Mormyrids and elephant fish ( Mormyridae )

Fossil record

The fossil record of Knochenzünglerartigen enough with Xixiaichthys from China back to the Early Cretaceous. Some fossil taxa are summarized in the Saurocephalidae family whose fossil record from the Hauterivian ( Lower Cretaceous ) to the Bartonium ( Eocene ) is sufficient. Palaeonopterus from the Cretaceous of Morocco is close to the Mormyridae and / or the Notopteridae and Phareodus from the Eocene, North American Green River Formation is an early representative of the Osteoglossidae.

Use

Many bony tongues are trapped in their home regions as a food fish. Smaller species, especially the butterfly fish and elephant fish are exported to aquarium purposes. Large osteoglossid, but also knife fish and mormyrids are often seen in public aquaria. They can be ten to well over twenty years old there.