Fossil of Bothriolepis panderi showing its caliper-like pectoral fins
Scientific classification
Domain:
Eukaryota
Kingdom:
Animalia
Phylum:
Chordata
Subphylum:
Vertebrata
Infraphylum:
Gnathostomata
Class:
†Placodermi McCoy, 1848
Orders
†Antiarchi
†Arthrodira (includes Phyllolepida)
†Petalichthyida
†Ptyctodontida
†Rhenanida
†Acanthothoraci (paraphyletic)
"Maxillate placoderms"
†Qilinyu
†Entelognathus
†Silurolepis
†Bianchengichthys
†Minjinia
?Eugnathostomata
†Xiushanosteus
†Brindabellaspis
?†Pseudopetalichthyida
?†Stensioella
Synonyms
Placodermata
Placoderms (from Greek πλάξ (plax, plakos) 'plate' and δέρμα (derma) 'skin')[1] are members of the class Placodermi, a group of prehistoric fish known from Paleozoic fossils which lived from the Silurian to the end of the Devonian period. 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.
Placoderms are thought to be paraphyletic, consisting of several distinct outgroups or sister taxa to all living jawed vertebrates, which originated among their ranks.[2] In contrast, one 2016 analysis concluded that placodermi are likely monophyletic.[3]
Placoderms were also the first fish clade to develop pelvic fins, the second pair of paired fins and the precursor to hindlimbs in tetrapods, as well as true teeth.[4] 380-million-year-old fossils of three other genera, Incisoscutum, Materpiscis and Austroptyctodus, represent the oldest known examples of live birth.[5]
The first identifiable placoderms appear in the fossil record during the late Llandovery epoch of the early Silurian.[6] The various groups of placoderms were diverse and abundant during the Devonian, but became extinct at the end-Devonian Hangenberg event 358.9 million years ago.[7]
Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).
^Colbert, Edwin H. (Edwin Harris); Knight, Charles Robert (1951). The dinosaur book: the ruling reptiles and their relatives. New York: McGraw-Hill. p. 153.
^Li, Qiang; Zhu, You-an; Lu, Jing; Chen, Yang; Wang, Jianhua; Peng, Lijian; Wei, Guangbiao; Zhu, Min (August 2021). "A new Silurian fish close to the common ancestor of modern gnathostomes". Current Biology. 31 (16): 3613–3620.e2. Bibcode:2021CBio...31E3613L. doi:10.1016/j.cub.2021.05.053. PMID 34146483. S2CID 235477130.
^King, Benedict; Qiao, Tuo; Lee, Michael S. Y.; Zhu, Min; Long, John A. (5 December 2016). "Bayesian Morphological Clock Methods Resurrect Placoderm Monophyly and Reveal Rapid Early Evolution in Jawed Vertebrates". Systematic Biology. 66 (4): 499–516. doi:10.1093/sysbio/syw107. PMID 27920231.
^Rücklin, M.; Donoghue, P. C. J.; Johanson, Z.; Trinajstic, K.; Marone, F.; Stampanoni, M. (2012). "Development of teeth and jaws in the earliest jawed vertebrates". Nature. 491 (7426): 748–751. Bibcode:2012Natur.491..748R. doi:10.1038/nature11555. PMID 23075852. S2CID 4302415.
^"Fossil reveals oldest live birth". BBC. May 28, 2008. Retrieved May 30, 2008.
^Burrow, Carol & Turner, Susan (September 1998). "A review of placoderm scales, and their significance in placoderm phylogeny". Journal of Vertebrate Paleontology. 19 (2): 204–219. doi:10.1080/02724634.1999.10011135.
^Sallan, Lauren & Coates, Michael (June 2010). "End-Devonian extinction and a bottleneck in the early evolution of modern jawed vertebrates". Proceedings of the National Academy of Sciences. 107 (22): 10131–10135. Bibcode:2010PNAS..10710131S. doi:10.1073/pnas.0914000107. PMC 2890420. PMID 20479258.
Placoderms (from Greek πλάξ (plax, plakos) 'plate' and δέρμα (derma) 'skin') are members of the class Placodermi, a group of prehistoric fish known from...
This list of placoderms is an attempt to create a comprehensive listing of all genera from the fossil record that have ever been considered to be members...
Dunkleosteus consists of ten species, some of which are among the largest placoderms ("plate-skinned") to have ever lived: D. terrelli, D. belgicus, D. denisoni...
record from the Silurian by two groups of fish: the armoured fish known as placoderms, which evolved from the ostracoderms; and the Acanthodii (or spiny sharks)...
thought to have lacked pectoral or pelvic fins. In addition to this, some placoderms (extinct fish with bony plates) were shown to have a third pair of paired...
lepis 'scale') was a widespread, abundant and diverse genus of antiarch placoderms that lived during the Middle to Late Devonian period of the Paleozoic...
characteristics are considered homologous characteristics derived from common placoderm ancestors[clarification needed], and present also in basal cartilaginous...
connection between the teeth and the original dermal scales. The old placoderms did not have teeth at all, but had sharp bony plates in their mouth. Thus...
including all living cartilaginous and bony fish, as well as the extinct placoderms and acanthodians. Most fish are cold-blooded, their body temperature varying...
goniatites). Trilobites and ostracoderms decline, while jawed fishes (placoderms, lobe-finned and ray-finned bony fish, and acanthodians and early cartilaginous...
leading the Devonian to often be dubbed the Age of Fishes. The armored placoderms began dominating almost every known aquatic environment. In the oceans...
during the Silurian was the diversification of jawed fish, which include placoderms, acanthodians (which gave rise to cartilaginous fish) and osteichthyan...
research presented in 2024 is a list of new taxa of jawless vertebrates, placoderms, acanthodians, fossil cartilaginous fishes, bony fishes, and other fishes...
bonytongue fish of the family Osteoglossidae Draconichthys, an arthrodire placoderm named after Stomiid dragonfishes Dragonfish (novel), a 2015 novel by Vu...
of the first fish to have jaws were the armoured and mainly predatory placoderms of the Silurian to Devonian periods, one of which, the 6 m (20 ft) Dunkleosteus...
groups of placoderms. Arthrodire placoderms are notable for the movable joint between armor surrounding their heads and bodies. Like all placoderms, they...
Devonian fishes, including an early shark Cladoselache, Eusthenopteron and other lobe-finned fishes, and the placoderm Bothriolepis (Joseph Smit, 1905)....
Titanichthys is an extinct genus of giant, aberrant marine placoderm from shallow seas of the Late Devonian of Morocco, Eastern North America, and possibly...
Bothriolepidoidei is a suborder of antiarch placoderm fishes. The group is considered paraphyletic. The cladogram is taken from Bothriolepid antiarchs...
class Placodermi. Recent studies indicate that Osteichthyes evolved from placoderms like Entelognathus, while acanthodians are more closely related to modern...
conodonts and ostracoderms, as well as jawed fish such as the armored placoderms (e.g. Dunkleosteus), the spiny acanthodians and early bony fish. The Devonian...
probably originally evolved in the Silurian period and appeared in the Placoderm fish which further diversified in the Devonian. The two most anterior...
of its body, which is not common in other fish (Tarrasius, Mandageria, placoderms and extant seahorses being some exceptions; see also Lepidogalaxias and...
placoderm. Asterolepis A. alticristata NV2K17 locality. Numerous specimens. A placoderm. A. cf. radiata NV2K17 locality. Multiple plates. A placoderm...
research presented in 2022 is a list of new taxa of jawless vertebrates, placoderms, acanthodians, fossil cartilaginous fishes, bony fishes, and other fishes...
contrasted with the Chondrichthyes (cartilaginous fish) and the extinct placoderms and acanthodians, which have endoskeletons primarily composed of cartilage...
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