Halecomorphi

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Halecomorphi
Temporal range: 251–present Ma
Cipactlichthys scutatus holotype.png
Cretaceous Cipactlichthys scutatus
Amia calva 1908.jpg
Amia calva/bowfin
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Subclass: Neopterygii
Infraclass: Holostei
Clade: Halecomorphi
Cope, 1872
Orders and families[1]

Halecomorphi is a taxon of ray-finned bony fish in the clade Neopterygii. The sole living Halecomorph is the bowfin (Amia calva), 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 , , 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 )
  • Fan like arrangement of small bones () 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
Holostei

Ginglymodi (gars and their fossil relatives) Lepisosteus platostomus.jpg

Halecomorphi (bowfin and its fossil relatives) Amia calva.jpg

Teleostei Engraulis ringens.jpg

The following cladogram[11] sumarizes the evolutionary relationships of living and fossil orders of Halecomorphi.

Halecomorphi

Parasemionotiformes Albertonia cupidinia 34.jpg

Eoeugnathus megalepis.JPG

Ionoscopus analibrevis.jpg

Amiiformes (bowfin and its fossil relatives) Amia calva.jpg

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.
  2. ^ Ax, Peter [translated by Dr.Richard. E. Dunmur] (2010). "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: 481–499.
  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. doi:10.1080/02724634.1998.10011114.
  6. ^ López-Arbarello, Adriana; Sferco, Emilia (March 2018). "Neopterygian phylogeny: the merger assay". Royal Society Open Science. 5: 172337. doi:10.1098/rsos.172337.
  7. ^ Betancur-R (2016). "Phylogenetic Classification of Bony Fishes Version 4".
  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, editors (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. doi:10.1080/14772019.2016.1181679.
  • 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
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