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Pteraspidomorphi Temporal range: Furongian to Late Devonian PreꞒ Ꞓ O S D C P T J K Pg N
Pteraspis
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Infraphylum:	Agnatha
Class:	†Pteraspidomorphi Goodrich, 1909
Type species
Pteraspis rostrata Agassiz, 1835
Subgroups
†Anatolepis †Arandaspida †Heterostracomorphi †Astraspida †Eriptychiida †Heterostraci

Pteraspidomorphi is an extinct class of early jawless fish. They have long been regarded as closely related or even ancestral to jawed vertebrates, but the few characteristics they share with the latter are now considered as basal traits for all vertebrates.

Characteristics

Pteraspidomorphs are characterized by their massive dermal head armour having large, median, ventral and dorsal plates or shields.

The fossils show extensive shielding of the head. Many had hypocercal tails in order to generate lift to increase ease of movement through the water for their armoured bodies, which were covered in dermal bone. They also had sucking mouth parts and some species may have lived in fresh water.

Most pteraspidomorphs were marine, but lived very near to the shore, in lagoons and deltas. Some groups are thought to have been fresh water-dwelling. They were certainly bottom-dwellers, as shown by traces of abrasion of the ventral surfaces of their headshields.

Classification

Pteraspidomorphs have been first regarded as related to bony fishes, then to sharks, then ancestral to hagfishes, and finally as the closest jawless relatives of the gnathostomes.

This last theory was based on the fact that they seem to have a paired olfactory organ and a sensory-line pattern which is quite similar to that of the gnathostomes. These characteristics are, however, likely to be general for either the vertebrates or, at any rate, for the ensemble of all ostracoderms and the gnathostomes. Other ostracoderms, such as the Galeaspida are now known to have a paired olfactory organ. Current phylogenetic analysis using a large number of characteristics now place pteraspidomorphs as the sister-group of all other ostracoderms and the gnathostomes.

Phylogeny

Based on the work of Mikko Haaramo.

See also

• Ostracoderm

References

1. "Pteraspidomorphi". After Carroll, 1988, and Janvier, 1997. Retrieved 26 October 2013.
2. Janvier, Philippe (1997) Pteraspidomorphi The Tree of Life Web Project.
3. Haaramo, Mikko (2007). "†Pteraspidomorphi". Mikko's Phylogeny Archive. Retrieved 30 December 2016.

External links

• Pteraspidomorphi at Tolweb
• Pteraspidomorphi at Palaeos

v t e Pteraspidomorphi
Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata
Pteraspidomorphi Pteraspidomorphi Anatolepis Arandaspida Arandaspidiformes Astraspididae Astraspis Arandaspididae Andinaspis Apedolepis Arandaspis Areyongalepis Pircanchaspis Porophoraspis Ritchieichthys Sacabambaspis Heterostracomorphi Astraspida Astraspidiformes Astraspididae Astraspis Pycnaspis Tesakoviaspidida Tesakoviaspididae Kodinskaspis Tesakoviaspis Eriptychiida Eriptychiiformes Eriptychiidae Eleochera Eriptychiidae Eriptychius Oniscolepididae Kallostrakon Oniscolepis Heterostraci see below↓
Heterostraci Heterostraci Cyathaspidiformes see below↓ Pteraspidiformes see below↓ Cardipeltida Cardipeltis Lepidaspidida Lepidaspis Corvaspidida Corvaspis Tolypelepidida Asketaspis Athenaegis Tolypelepis Tesseraspidiformes Natlaspis Tesseraspis Traquairaspidiformes Phialaspididae Munchoaspis Phialaspis Toombsaspis Traquairaspididae Pseudotraquairaspis Rimasventeraspis Traquairaspis Weigeltaspididae？ Weigeltaspis
Cyathaspidiformes Cyathaspidiformes Nakaolinaspis？ Cyathaspidida Cyathaspidae Cyathaspis Americaspis Archegonaspis Capitaspis Dikenaspis Dinaspidella Homaspidella Irregulareaspis Nahanniaspis Pionaspis Poraspis Ptomaspis Seretaspis Steinaspis Torpedaspis Veronaspis Ariaspidae Ariaspis Anglaspis Listraspis Liliaspis Paraliliaspis Ctenaspidae Ctenaspis Allocryptaspis Alainaspis Zaphoctenaspis Arctictenaspis Boothiaspis Amphiaspidida incertae sedis Gunaspis Amphiaspidoidei Amphiaspididae Amphiaspis Amphoraspis Edaphaspididae Edaphaspis Gabreyaspididae Gabreyaspis Prosarctaspis Pelaspis Tareyaspis Olbiaspididae Olbiaspis Kureykaspis Angaraspis Hibernaspidoidei Hibernaspididae Hibernaspis Eglonaspididae Eglonaspis Gerronaspis Lecaniaspis Empedaspis Pelurgaspis Aphataspididae Aphataspis Putoranaspis Siberiaspidoidei Siberiaspididae Siberiaspis Argyriaspis Tuxeraspididae Tuxeraspis Litotaspis Dotaspis
Pteraspidiformes Pteraspidiformes Anchipteraspididae Anchipteraspis Rhachiaspis Ulutitaspis Podolaspididae Dnestraspis Parapteraspis Semipodolaspis Protopteraspididae Protopteraspis Doryaspis Escharaspis Miltaspis Stegobranchiaspis Unkaraspis "Trygonaspis" Psammosteida Tartuosteus Weigeltaspis？ Drepanaspididae Drepanaspis Guerichosteidae Guerichosteus Hariosteus Pycnolepis Pycnosteidae Tartuosteus Pycnosteus Psammolepididae Psammosteus Psammosteidae Crenosteus Elgaia Karelosteus Osteoplax Placosteus Psammosteus Psarkosteus Rohonosteus Selerolepis Vladimirolepis Obrucheviidae Obruchevia Pteraspidoidei incertae sedis Palanasaspis Pteraspididae Althaspis Blieckaspis Brachipteraspis Errivaspis Escharaspis Grumantaspis Helaspis Larnovaspis Loricopteraspis Miltaspis Mitraspis Mylopteraspidella Mylopteraspis Podolaspis Pteraspis Rhinopteraspis Stegobranchiaspis Gigantaspididae Gigantaspis Protaspididae Protaspis Cosmaspis Lampraspis Europrotaspis Cyrtaspidichthys Oreaspis Psephaspis Rodenaspis Tuberculaspis Xylaspis Zascinaspis Woodfjordaspis Pirumaspis
Category

v t e Evolution of fish
Fish Timeline of fish evolution
Forerunners	Basal member †Pikaia Cephalochordate †Cathaymyrus Lancelet Olfactores †Haikouella Tunicate †Myllokunmingiidae? (†Haikouichthys, †Myllokunmingia) †Zhongxiniscus?
Jawless fish	Cyclostomata Hagfish Hyperoartia Lamprey †Conodonts †Protoconodonta? †Paraconodontida †Conodonta †Ostracoderms †Pteraspidomorphi †Thelodonti †Anaspida †Cephalaspidomorphi †Galeaspida †Pituriaspida †Osteostraci
Jawed fish	†Placoderms †Antiarchi †Arthrodira †Brindabellaspida †Petalichthyida †Phyllolepida †Ptyctodontida †Rhenanida †Acanthothoraci †Pseudopetalichthyida? †Stensioellida? †Acanthodii †Acanthodiformes †"Climatiiformes" †Diplacanthiformes †Ischnacanthiformes Cartilaginous Elasmobranchii †Ctenacanthiformes †Hybodontiformes †Phoebodontiformes †Xenacanthida Ray Shark Holocephali †Eugeneodontida †Iniopterygiformes †Petalodontiformes †Symmoriiformes Chimaera Bony Lobe-finned †Onychodontiformes Coelacanth Rhipidistia †Porolepiformes Lungfish Tetrapodomorpha Ray-finned †"Palaeonisciformes" Cladistia Polypteriformes Chondrostei Acipenseriformes Neopterygii †Pycnodontiformes Halecomorphi Ginglymodi Teleost
Lists	Lists of prehistoric fish spiny sharks placoderms cartilaginous bony lobe-finned List of transitional fossils
Related	Prehistoric life Transitional fossils Vertebrate paleontology
† extinct

• Pteraspidomorphi
• Furongian first appearances
• Late Devonian animals
• Late Devonian extinctions
• Prehistoric fish classes