Placoderms
Sign in to savePlacoderms (from Ancient Greek πλάξ [plax, plakos] 'plate' and δέρμα [derma] 'skin') are vertebrate animals of the class Placodermi, an extinct group of prehistoric fish known from Paleozoic fossils during the Silurian and the Devonian periods. While their endoskeletons are mainly cartilaginous, their head and thorax were covered by articulated armoured plates (hence the name), and the rest of the body was scaled or naked depending on the species.
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Placoderms were an extinct group of prehistoric fish that lived during the Silurian and Devonian periods, distinguished by their distinctive armor-plated heads and thoraxes covering mostly cartilaginous skeletons. They matter to our understanding of vertebrate evolution because they represent an early branch of fish that developed protective plating, a significant innovation in how ancient animals adapted to their environments.
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Article
23 sectionsContents
- Characteristics
- History of study
- Evolution and extinction
- Fossil record
- Taxonomy and phylogeny
- Placoderm orders
- Arthrodira
- Antiarchi
- Brindabellaspida
- Phyllolepida
- Ptyctodontida
- Rhenanida
- Acanthothoraci
- Petalichthyida
- Pseudopetalichthyida
- Stensioellida
- Cladogram
- See also
- Notes
- References
- Citations
- Other references
- External links
Placoderms (from Ancient Greek πλάξ [plax, plakos] 'plate' and δέρμα [derma] 'skin') are vertebrate animals of the class Placodermi, an extinct group of prehistoric fish known from Paleozoic fossils during the Silurian and the Devonian periods. While their endoskeletons are mainly cartilaginous, their head and thorax were covered by articulated armoured plates (hence the name), and the rest of the body was scaled or naked depending on the species.
Placoderms were among the first jawed fish (their jaws likely evolved from the first pair of gill arches), as well as the first vertebrates to have true teeth. They were also the first fish clade to develop pelvic fins, the second set of paired fins and the homologous precursor to hindlimbs in tetrapods. 380-million-year-old fossils of three other genera, Incisoscutum, Materpiscis and Austroptyctodus, represent the oldest known examples of live birth.