Dorsal fin
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A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the f
Dorsal fin of a shark
Most fish, like this large goldfish, have one dorsal fin.
Many catfish can lock their dorsal fin spines erect and secrete venom to discourage predators.
The great white shark's dorsal fin contains stabilizing dermal fibers that stiffen dynamically as it swims faster to control roll and yaw.
Ichthyosauria
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Ichthyosauria is an order of large extinct marine reptiles sometimes referred to as "ichthyosaurs", although the term is also used for wider clades in which the order resides.
Dorsal fin
…environments, so the fins are not all homologous. They are found in most fish, in mammals such as whales, and in extinct ancient marine reptiles such as ichthyosaurs. Most have only one dorsal fin, but some have two or three. Wildlife biologists often use the distinctive nicks and wear patterns which develop on the…
Ichthyosaurus communis in London
An ichthyosaur and plesiosaur by Édouard Riou, 1863. This old representation of a plesiosaur lifting its head is not accurate and physically impossible.
The skull of specimen NHMUK PV R1158 found by Joseph Anning in 1811
The torso of specimen NHMUK PV R1158 found by Mary Anning in 1812