Halecomorphi Temporal range:251–present Ma PreꞒ Ꞓ O S D C P T J K Pg N
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 †Furidae †Ionoscopidae †Oshuniidae †Ophiopsidae †Subortichthyidae †Panxianichthyiformes †Panxianichthyiidae †Parasemionotiformes †Parasemionidae †Promecosominidae

Halecomorphi is ataxon ofray-finnedbony fish in thecladeNeopterygii. The only extant Halecomorph species are thebowfin (Amia calva) and eyespot bowfin (Amia ocellicauda), but the group contains many extinctspecies in severalfamilies (includingAmiidae,Caturidae,Liodesmidae,Sinamiidae) in theorderAmiiformes, as well as theextinct ordersIonoscopiformes,Panxianichthyiformes, andParasemionotiformes. The fossil record of halecomorphs goes back at least to theEarly Triassicepoch.

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

• Unique jaw articulation in which thequadrate andsymplectic participate in the joint.
• Lengtheneddorsal fins (in some species)
• Two biconcavevertebrae per segment in the posterior body region (a condition known asdiplospondyly)
• Fan like arrangement of small bones (hypurals) in the tail.

On the systematic position of the Halecomorphi, there are two competinghypotheses:

• TheHalecostomi hypothesis proposes Halecomorphi as thesister group ofTeleostei, the major group of livingneopterygians, rendering theHolosteiparaphyletic.^[3]
• TheHolostei hypothesis proposes Halecomorphi as the sister group ofGinglymodi, the group which includesgars (Lepisosteidae) and their fossil relatives, rendering the Halecostomi paraphyletic.^[4][5][6]

The latter hypothesis is more widely accepted.^{[7][8][9][10]}

The followingcladogram^[11] summarizes theevolutionary relationships ofextinct (indicated with adagger, †) andlivingorders of Halecomorphi.

• Brian J. Gardiner, John G. Maisey, D. Tim J. Littlewood:Interrelationships of Basal Neopterygians. S. 117-146 in: Melanie L. J. Stiassny, Lynne R. Parenti, G. David Johnson (Hrsg.):Interrelationships of Fishes. Academic Press, 1996,ISBN 0-12-670950-5

• Halecomorphi
• Vertebrate unranked clades
• Taxa named by Edward Drinker Cope

• CS1 maint: multiple names: authors list
• Articles with short description
• Short description matches Wikidata
• Articles with 'species' microformats