Ischnacanthiformes

Extinct order of cartilaginous fishes

Ischnacanthiformes Temporal range: 418–409 Ma PreꞒ Ꞓ O S D C P T J K Pg N

Nerepisacanthus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	†Acanthodii
Order:	†Ischnacanthiformes
Families
Ischnacanthidae Poracanthidae Xylacanthus

Ischanacanthiformes is a prehistoric order of "acanthodian" stem-chondrichthyans found in Canada, Ukraine and United Kingdom. Members of this order were nektonic carnivores,^[1] eating animals that swim rather than plankton. They had slender builds, light armor, deeply inserted spines, shark-like teeth, and two dorsal fins.^[1] Some species were around 2 meters (6.56 feet) long.^[2] It was described by Berg in 1940.^[3]^[4]

References

^ ^a ^b McGraw-Hill Dictionary of Scientific & Technical Terms (6 ed.). McGraw-Hill Companies, Inc. 2003.
^ "Palaeos Vertebrates Acanthodii: Teleostomi". palaeos.com. Retrieved 2018-09-30.
^ "†order Ischnacanthiformes Berg 1940 (spiny fish)". Fossilworks. Retrieved 11 January 2014.
^ Burrow, Carole. Acanthodians with dentigerous jaws: the Ischnacanthiformes and Acanthodopsis. Department of Zoology and Entomology, University of Queensland.

Evolution of fish

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

†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