What are the characteristics of the class actinopterygii?
General Characters:
- Thin and elongated fishes.
- Body is covered by small cycloid scales. Head region is devoid of any scales. Some fishes are scaleless.
- Long dorsal and caudal fins are spineless. Fins may not be supported by fin rays.
- Mouth aperture is comparatively large.
- No accessory respiratory organs are present.
What are 2 examples of the Chondrosteans?
Sturgeons and Paddlefishes. The next-most primitive actinopterygian (ray-finned) fishes are the chondrostean sturgeons and paddlefishes. All 25 species of sturgeons live in the Northern Hemisphere. All spawn in fresh water, although some species move seasonally between marine and fresh water.
Do actinopterygii have teeth?
In the most derived actinopterygians, there are fewer attachments of these bones and teeth are rarely present. This increased flexibility has allowed to the upper jaw to extend and protrude so as to permit a variety of feeding specializations.
Do actinopterygii lay eggs?
They use fins to help them swim, and they breathe underwater with gills. The gills are usually found in one or more slits in the skin behind their heads. Some fish lay eggs, while others give birth to live babies.
What type of fish are in class actinopterygii?
ray-finned fishes
The group of ray-finned fishes (Class Actinopterygii) encompasses over 20,000 species of fish that have ‘rays,’ or spines, in their fins. This separates them from the lobe-finned fishes (Class Sarcopterygii, e.g., the lungfish and coelacanth), which have fleshy fins.
How many species are in actinopterygii?
24,000
Actinopterygii includes a remarkably diverse assemblage of fishes, including more than half of the living species of known vertebrates; over 24,000 valid species are known (see Eschmeyer, 1998).
Why Chondrostei are classified under osteichthyes?
Distinguishing taxonomic features The chondrosteans, which also include extinct forms, are grouped into about 12 orders and separated from one another, for the most part, on the basis of differences in dermal bone pattern, body shape, and fin form and position. Chondrostei is ranked as a class in some taxonomies.
Is a gar a Chondrostean?
Three major orders of this subclass (ray-finned bony fish) are in existence; the Chondrostei (paddlefish, sturgeon); Holostei (gar, bowfin); and the Teleostei, which constitute the most advanced order and comprise the vast majority of present-day fishes; the number of nonteleost species of bony fish is very limited.
What are the differences between the Chondrichthyes and actinopterygii fish?
The main difference between Chondrichthyes and Osteichthyes is that the Chondrichthyes is the class of bony fish whose endoskeleton is made up of cartilages whereas Osteichthyes is the class of cartilaginous fish whose endoskeleton is made up of bones.
What type of tail do actinopterygii have?
Their tails were heterocercal. On their bodies were thick ganoid scales that abutted each other, rather than overlapping as in most modern fishes.
How do actinopterygii feed?
Feeding. Ray-finned fishes have a wide variety of feeding strategies. One interesting technique is that of the anglerfish, which entice their prey toward them using a movable (sometimes light-emitting) spine that is above the fish’s eyes.
What animals belong to the class actinopterygii?
Actinopterygiiray-finned fishes
- OrderAcipenseriformessturgeons and paddlefishes.
- OrderAlbuliformesbonefishes.
- OrderAmiiformesbowfins.
- OrderAnguilliformeseels.
- OrderAteleopodiformesjellynose or tadpole fishes.
- OrderAtheriniformessilversides.
- OrderAulopiformesgrinners, lizardfishes and allies.
- OrderBatrachoidiformes.
How are the fins of Actinopterygii related to the skeleton?
Actinopterygii (/ˌæktɪˌnɒptəˈrɪdʒiaɪ/), or the ray-finned fishes, constitute a class or subclass of the bony fishes. These actinopterygian fin rays attach directly to the proximal or basal skeletal elements, the radials, which represent the link or connection between these fins and the internal skeleton (e.g., pelvic and pectoral girdles).
What kind of scales does an actinopterygian have?
Unlike ganoid scales, which are found in non-teleost actinopterygians, new scales are added in concentric layers as the fish grows. Ray-finned and lobe-finned fishes, including tetrapods, possessed lungs used for aerial respiration. Only bichirs retain ventrally budding lungs.
What kind of fish are Chondrostei and Neopterygii?
The latter comprised subclasses Chondrostei and Neopterygii. The Neopterygii, in turn, is divided into the infraclasses Holostei and Teleostei. During the Mesozoic and Cenozoic the teleosts in particular diversified widely, and as a result, 96% of all known fish species are teleosts.
How are actinopterygians related to terrestrial vertebrates?
During the Mesozoic and Cenozoic the teleosts in particular diversified widely, and as a result, 96% of all known fish species are teleosts. The cladogram shows the major groups of actinopterygians and their relationship to the terrestrial vertebrates (tetrapods) that evolved from a related group of fish.