Halecomorphi

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 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)

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.

Systematics and phylogeny

On the systematic position of the Halecomorphi, there are two competing hypotheses:

• The Halecostomi hypothesis proposes Halecomorphi as the sister group of Teleostei, the major group of living neopterygians, rendering the Holostei paraphyletic.[3]
• The Holostei hypothesis proposes Halecomorphi as the sister group of Ginglymodi, the group which includes gars (Lepisosteidae) and their fossil relatives, rendering the Halecostomi paraphyletic.[4][5][6]

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

Neopterygii	Teleostei Holostei Ginglymodi (gars and their fossil relatives) Halecomorphi (bowfin and its fossil relatives)

The following cladogram[11] summarizes the evolutionary relationships of extinct (indicated with a dagger, †) and living orders of Halecomorphi.

Halecomorphi	†Parasemionotiformes †Panxianichthyiformes †Ionoscopiformes Amiiformes (bowfin and its fossil relatives)

References

1. J. S. Nelson; T. C. Grande; M. V. H. Wilson (2016). Fishes of the World (5th ed.). Wiley. p. 752. ISBN 978-1-118-34233-6. Archived from the original on 2019-04-08. Retrieved 2018-05-24.
2. Ax, Peter [translated by Dr.Richard. E. Dunmur] (2003). "Halecomorphi — Teleostei". Multicellular Animals. Berlin: Gardners Books. pp. 207–210. doi:10.1007/978-3-662-08874-6_29. ISBN 978-3-642-05515-7.
3. Patterson C. Interrelationships of holosteans. In: Greenwood P H, Miles R S, Patterson C, eds. Interrelationships of Fishes. Zool J Linn Soc, 1973, 53(Suppl): 233–305
4. Olsen P. E. (1984). "The skull and pectoral girdle of the parasemionotid fish Watsonulus eugnathoides from the Early Triassic Sakemena Group of Madagascar with comments on the relationships of the holostean fishes". J Vertebr Paleontol. 4 (3): 481–499. Bibcode:1984JVPal...4..481O. CiteSeerX 10.1.1.384.2050. doi:10.1080/02724634.1984.10012024.
5. Grande, Lance; Bemis, William E. (1998). "A Comprehensive Phylogenetic Study of Amiid Fishes (Amiidae) Based on Comparative Skeletal Anatomy. an Empirical Search for Interconnected Patterns of Natural History". Journal of Vertebrate Paleontology. 18 (sup001): 1–696. Bibcode:1998JVPal..18S...1G. doi:10.1080/02724634.1998.10011114.
6. López-Arbarello, Adriana; Sferco, Emilia (March 2018). "Neopterygian phylogeny: the merger assay". Royal Society Open Science. 5 (3): 172337. Bibcode:2018RSOS....572337L. doi:10.1098/rsos.172337. PMC 5882744. PMID 29657820.
7. Betancur-R (2016). "Phylogenetic Classification of Bony Fishes Version 4". Archived from the original on 2017-07-11. Retrieved 2021-06-06.
8. Nelson, Joseph, S. (2016). Fishes of the World. John Wiley & Sons, Inc. ISBN 978-1-118-34233-6.
9. "Actinopterygii". Integrated Taxonomic Information System. Retrieved 3 April 2006.
10. R. Froese and D. Pauly, ed. (February 2006). "FishBase".
11. Sun, Zuoyu; Tintori, Andrea; Xu, Yaozhong; Lombardo, Cristina; Ni, Peigang; Jiang, Dayoung (April 2017). "A new non-parasemionotiform order of the Halecomorphi (Neopterygii, Actinopterygii) from the Middle Triassic of Tethys". Journal of Systematic Palaeontology. 15 (3): 223–240. Bibcode:2017JSPal..15..223Z. doi:10.1080/14772019.2016.1181679. S2CID 133176227.

• 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