Chondrostei

Chondrostei is a diverse clade of ray-finned fishes belonging to the subclass Actinopterygii. They are an ancient lineage, with fossil records dating back to the Paleozoic era, and are considered a basal group within the bony fishes. Chondrostei are characterized by their cartilaginous skeletons, which, despite their name, are often partially ossified. This group includes a variety of species, some of which are quite familiar, such as sturgeons and paddlefish.

Adriatic sturgeon – Acipenser naccarii

Siberian sturgeon – Acipenser baerii

White sturgeon – Acipenser transmontanus

Shortnose sturgeon – Acipenser brevirostrum

Starry sturgeon – Acipenser stellatus

Sterlet sturgeon – Acipenser ruthenus

Lake sturgeon – Acipenser fulvescens

Common Names

The term "Chondrostei" does not have a common name in the same way that other groups of fish do, such as "salmon" or "tuna." Instead, the common names refer to the specific families and genera within the clade. For example, sturgeons are known as "sturgeons," paddlefish are known as "paddlefish," and so on.

Characteristics

Chondrostei share a number of characteristics that distinguish them from other ray-finned fishes. These include:

  • Cartilaginous skeleton: While their skeletons are mostly made of cartilage, they are often partially ossified, meaning that some of the cartilage has been replaced by bone.
  • Ganoid scales: Many chondrosteans have a unique type of scale called ganoid scales, which are thick, diamond-shaped, and often have a shiny, enamel-like coating.
  • Heterocercal tail: The tail fin is asymmetrically lobed, with the upper lobe larger than the lower lobe. This is in contrast to the homocercal tails found in most other teleost fishes.
  • Barbels: Many chondrosteans have barbels, fleshy appendages near their mouths that are used to sense prey.

Environments

Chondrostei occupy a variety of aquatic environments, ranging from freshwater rivers and lakes to saltwater oceans. Sturgeons, for example, are often found in large rivers and estuaries, while paddlefish inhabit large rivers and lakes in North America.

References

For more information on Chondrostei, consult the following resources: