Everything about Chondrostei totally explained
Chondrostei are primarily
cartiliginous fish showing some
ossification. There are 52 species divided among two orders, the
Acipenseriformes (
sturgeons and
paddlefishes) and the
Polypteriformes (
reedfishes and
bichirs).
It is thought that the ancestors of the chondrosteans were
bony fish but this characteristic was lost in later
evolutionary development, resulting in a lightening of the frame. Elderly chondrosteans show beginnings of ossification of the skeleton which suggests that this process is delayed rather than lost in these fish.
This group has at times been classified with the
sharks: the similarities are obvious, not only do the chondrosteans mostly lack bone, the structure of the jaw is more akin to that of sharks than other bony fish, and both lack
scales (excluding the
sturgeons). However the fossil record suggests that these fish have more in common with the
Teleostei than their external appearance might suggest.
Additional shared features include
spiracles and (sturgeons) a heterocercal tail (the
vertebrae extend into the larger lobe of the
caudal fin).
Chondrostei is
paraphyletic meaning that this subclass doesn't contain all the descendants of their common ancestor; reclassification of the Chondrostei is therefore not out of the question.
The name comes from
Greek chondros meaning cartilage and
osteo meaning bone.
Further Information
Get more info on 'Chondrostei'.
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