Ostracoderm
Ostracoderm
Ostracoderm (pronounced: /ˈɒstrəkəˌdɜːrm/), from the Greek words "ostrakon" meaning shell and "derma" meaning skin, refers to any member of the extinct class of jawless fish, known for their hard, bony shields which covered their bodies.
Etymology
The term "Ostracoderm" is derived from the Greek words "ostrakon" and "derma". "Ostrakon" translates to "shell" or "tile", and "derma" translates to "skin". This name is a reference to the hard, bony shields that characterized these early fish.
Characteristics
Ostracoderms were among the first vertebrates, appearing in the Ordovician period and thriving until the end of the Devonian period. They were characterized by their lack of jaws, and instead, they had a simple mouth opening. Their bodies were covered in a bony shield, which served as a form of protection against predators.
Classification
Ostracoderms are classified under the superclass Agnatha, which includes all jawless fish. They are further divided into several orders, including the Cephalaspidomorphi, Pteraspidomorphi, and Thelodonti.
Evolution
The evolution of ostracoderms is significant as they represent one of the earliest forms of vertebrates. They are believed to have evolved from invertebrate chordates. The development of their bony shields is considered a major evolutionary step in the development of vertebrates.
Extinction
Ostracoderms became extinct at the end of the Devonian period, likely due to the emergence of more advanced fish with jaws, which were better adapted to the changing environment and could outcompete the ostracoderms for resources.
See Also
External links
- Medical encyclopedia article on Ostracoderm
- Wikipedia's article - Ostracoderm
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