Bony fish showcase
The fan-finned fishes - Actinopterygii - belong to the bony fishes. The oldest fan-finned fishes are known from the Devonian. Already early in their evolutionary history there were many different kinds of fan-finned fishes that were adapted to different sources of food and habitat. This has continued through their approximately 400 milllion year long history and up to the present day.
Fan-finned fishes live in the oceans as well as in rivers and lakes. Today there are about 25 000 different species of fan-finned fishes ranging from the tiniest forms up to giants of several hundred kilogrammes. The drawings to the right and left show the outline of some fan-finned fishes of today. They are not shown to the same scale.
The lobe-finned fishes - Crossopterygii - belong to the bony fishes.
Lung fishes - Dipnoi - belong to the bony fishes. They live in water and breathe with gills. But as the name implies, lung fishes also have developed lungs. Therefore they can periodically stay out of water and breathe in the air. During their 400 million years of evolution, they show suprisingly little variation in body design. In the early Devonian (about 400 million years ago), we find the first remnants of lung fishes. Later in the Devonian and the Carboniferous, the lung fishes were relatively common. But the diversity decreased through time and there are only three genera of lung fishes living today.
Most lung fishes do not have teeth along the jaw edges. Instead, they have developed large teeth plates that act as powerful grinding apparatuses. The African lung fish Protopterus has both gills and lungs. The skin is covered by small scales. The pectoral and pelvic fins have been transformed into thin threads. The anal- and dorsal fins have fused with the tail fin, making a rim around the posteriormost part of the body. There are only three genera of lung fishes living today, and all live in fresh water. They live in the northern part of South America (Lepidosiren), central Africa (Protopterus) and the north eastern part of Australia (Neoceratodus). The African lung fishes bury themselves in the ground during droughts. Here they live in small cavities and breathe with lungs. List of contents in the bony fish showcase
Publisert 18. mai 2011 16:00