Halecomorphi

Halecomorphi is a taxon of ray-finned bony fish in the clade Neopterygii. The only extant Halecomorph species are the bowfin (Amia calva) and eyespot bowfin (Amia ocellicauda), but the group contains many extinct species in several families (including Amiidae, Caturidae, Liodesmidae, Sinamiidae) in the order Amiiformes, as well as the extinct orders Ionoscopiformes, Panxianichthyiformes, and Parasemionotiformes. The fossil record of halecomorphs goes back at least to the Early Triassic epoch.

The parasemionotiform †Watsonulus

The ionoscopiform †Ionoscopus

The amiiform †Caturus

The amiiform †Calamopleurus

The amiiform †Sinamia

Skull of Amia calva (bowfin)

Halecomorphi Temporal range:
Cretaceous †Cipactlichthys scutatus
Amia calva (bowfin)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Subclass:	Neopterygii
Infraclass:	Holostei
Clade:	Halecomorphi Cope, 1872
Orders and families[1]
Amiiformes Amiidae †Caturidae †Liodesmidae †Sinamiidae †Ionoscopiformes †Ionoscopidae †Oshuniidae †Ophiopsidae †Panxianichthyiformes †Panxianichthyiidae †Parasemionotiformes †Parasemionidae †Promecosominidae

The Halecomorphi exhibit a combination of ancestral features, such as most heavily mineralized scales, but also by more derived or "modern" features, particularly in the structure of the skull (e.g. position and shape of preopercles). Unique derived traits (synapomorphies) of the Halecomorphi include:[2]

• Unique jaw articulation in which the quadrate and symplectic participate in the joint.
• Lengthened dorsal fins (in some species)
• Two biconcave vertebrae per segment in the posterior body region (a condition known as diplospondyly)
• Fan like arrangement of small bones (hypurals) in the tail.