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, Ophiopsiformes, Panxianichthyiformes, and Parasemionotiformes. The fossil record of halecomorphs goes back at least to the Early Triassic epoch.

thumb|left|The parasemionotiform †Watsonulus thumb|left|The ionoscopiform †Ionoscopus thumb|left|The amiiform †Caturus thumb|left|The amiiform †Calamopleurus thumb|left|The amiiform †Sinamia thumb|left|Skull of Amia calva (bowfin) 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: 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.