Elasmobranchii

Subclass of fishes

Elasmobranchs

Temporal range: Givetian–Recent

PreꞒ

Great white shark
(Carcharodon carcharias)
Scientific classification
Domain:  | Eukaryota
Kingdom:  | Animalia
Phylum:  | Chordata
Class:  | Chondrichthyes
Clade:  | Euselachii
Subclass:  | Elasmobranchii
Bonaparte, 1838
Subgroups

See text

Elasmobranchii (/ɪˌlæzməˈbræŋkiaɪ/[1]) is a subclass of Chondrichthyes or cartilaginous fish, including modern sharks (division Selachii), and batomorphs (division Batomorphi, including rays, skates, and sawfish). Members of this subclass are characterised by having five to seven pairs of gill slits opening individually to the exterior, rigid dorsal fins and small placoid scales on the skin. The teeth are in several series; the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper. The details of this jaw anatomy vary between species, and help distinguish the different elasmobranch clades. The pelvic fins in males are modified to create claspers for the transfer of sperm. There is no swim bladder; instead, these fish maintain buoyancy with large livers rich in oil.

The definition of the clade is unclear with respect to fossil chondrichthyans. Some authors consider it as equivalent to Neoselachii (the crown group clade including modern sharks, rays, and all other descendants of their last common ancestor). Other authors use the name Elasmobranchii for a broader branch-based group of all chondrichthyans more closely related to modern sharks and rays than to Holocephali (the clade containing chimaeras and their extinct relatives).[2] Important extinct groups of elasmobranchs sensu lato include the hybodonts (Order Hybodontiformes), xenacanths (order Xenacanthformes) and Ctenacanthiformes. These are also often referred to as "sharks" in reference to their similar anatomy and ecology to modern sharks.

The name Elasmobranchii comes from the Ancient Greek words elasmo- ("plate") and bránchia ("gill"), referring to the broad, flattened gills which are characteristic of these fishes.

> Elasmobranchs lack swim bladders, and maintain buoyancy with oil that they store in their livers. Some deep sea sharks are targeted by fisheries for this liver oil, including the school, gulper and basking sharks (pictured).[3] All three of these species have been assessed by the IUCN as vulnerable due to overfishing.[4][5][6]

> From a practical point of view the life-history pattern of elasmobranchs makes this group of animals extremely susceptible to over fishing. It is no coincidence that the commercially exploited marine turtles and baleen whales, which have life-history patterns similar to the sharks, are also in trouble.[7]

## Description

[edit]

Members of the Elasmobranchii subclass have no swim bladders, five to seven pairs of gill clefts opening individually to the exterior, rigid dorsal fins, and small placoid scales. The teeth are in several series; the upper jaw is not fused to the cranium, and the lower jaw is articulated with the upper.

Extant elasmobranchs exhibit several archetypal jaw suspensions: amphistyly, orbitostyly, hyostyly, and euhyostyly. In amphistyly, the palatoquadrate has a postorbital articulation with the chondrocranium from which ligaments primarily suspend it anteriorly. The hyoid articulates with the mandibular arch posteriorly, but it appears to provide little support to the upper and lower jaws. In orbitostyly, the orbital process hinges with the orbital wall and the hyoid provides the majority of suspensory support.

In contrast, hyostyly involves an ethmoid articulation between the upper jaw and the cranium, while the hyoid most likely provides vastly more jaw support compared to the anterior ligaments. Finally, in euhyostyly, also known as true hyostyly, the mandibular cartilages lack a ligamentous connection to the cranium. Instead, the hyomandibular cartilages provide the only means of jaw support, while the ceratohyal and basihyal elements articulate with the lower jaw, but are disconnected from the rest of the hyoid.[8][9][10] The eyes have a tapetum lucidum. The inner margin of each pelvic fin in the male fish is grooved to constitute a clasper for the transmission of sperm. These fish are widely distributed in tropical and temperate waters.[11]

Many fish maintain buoyancy with swim bladders. However elasmobranchs lack swim bladders, and maintain buoyancy instead with large livers that are full of oil.[12] This stored oil may also function as a nutrient when food is scarce.[7][13]

## Evolutionary history

[edit]

See also: Evolution of fish

The oldest unambigous total group elasmobranch, Phoebodus, has its earliest records in the Middle Devonian (late Givetian), around 383 million years ago.[14] Several important groups of total group elasmobranchs, including Ctenacanthiformes and Hybodontiformes, had already emerged by the latest Devonian (Famennian).[15] During the Carboniferous, some ctenacanths would grow to sizes rivalling the modern great white shark with bodies in the region of 7 metres (23 ft) in length.[16] During the Carboniferous and Permian, the xenacanths were abundant in both freshwater and marine environments, and would continue to exist into the Triassic with reduced diversity.[17] The hybodonts had achieved a high diversity by the Permian,[18] and would end up becoming the dominant group of elasmobranchs during the Triassic and Early Jurassic. Hybodonts were extensively present in both marine and freshwater environments.[19] While Neoselachii/Elasmobranchi sensu stricto (the group of modern sharks and rays) had already appeared by the Triassic, they only had low diversity during this period and only began to extensively diversify from the Early Jurassic onwards, when modern orders of sharks and rays appeared.[20] This co-incided with the decline of the hybodonts, which had become minor components of marine environments by the Late Jurassic but would remain common in freshwater environments into the Cretaceous.[21] The youngest remains of hybodonts date to the very end of the Cretaceous.[22]

## Taxonomy

[edit]

Elasmobranchii was first coined in 1838 by Charles Lucien Bonaparte. Bonaparte's original definition of Elasmobranchii was effectively identical to modern Chondrichthyes, and was based around gill architecture shared by all 3 living major cartilaginous fish groups. During the 20th century it became standard to exclude chimaeras from Elasmobranchii; along with including many fossil chondrichthyans within the group. The definition of Elasmobranchii has since been subject to much confusion with regard to fossil chondrichthyans. Maisey (2012) suggested that Elasmobranchii should exclusively be used for the last common ancestor of modern sharks and rays, a grouping which had previously been named Neoselachii by Compagno (1977).[2] Other recent authors have used Elasmobranchii in a broad sense to include all chondrichthyans more closely related to modern sharks and rays than to chimaeras.[14]

The total group of Elasmobranchii includes the cohort Euselachii Hay, 1902, which groups the Hybodontiformes and a number of other extinct chondrichthyans with Elasmobrachii sensu stricto/Neoselachii, to the exclusion of more primitive total group elasmobranchs, which is supported by a number of shared morphological characters of the skeleton.[23][24][25][26]

* Total group Elasmobranchii
* †Order Phoebodontiformes
* †Order Squatinactiformes
* †Infraclass Xenacanthimorpha
* †Order Xenacanthiformes
* †Order Ctenacanthiformes
* †Order Jalodontiformes
* †Bandringa
* Infraclass Euselachii
* †Order Hybodontiformes
* †Family Protacrodontidae
* †Family Tristychiidae
* Tristychius
* Acronemus
* †Artiodus
* Division Neoselachii (Elasmobranchii sensu stricto)
* †Family Anachronistidae
* †Order Synechodontiformes (incertae sedis)
* Subdivision Selachii (Selachimorpha) (modern sharks)
* Superorder Galeomorphi
* Order Heterodontiformes (bullhead sharks)
* Order Orectolobiformes (carpet sharks)
* Order Lamniformes (mackerel sharks)
* Order Carcharhiniformes (ground sharks)
* Superorder Squalomorphi
* Order Echinorhiniformes (bramble sharks)[27][28]
* Order Hexanchiformes (frilled and cow sharks)
* Order Squaliformes (dogfish sharks)
* †Family Protospinacidae
* Order Squatiniformes (angel sharks)
* Order Pristiophoriformes (sawsharks)
* Subdivision Batoidea (rays, skates, and sawfish)
* Order Torpediniformes (electric rays)
* Order Rhinopristiformes (sawfishes, guitarsfishes, wedgefishes and relatives)
* Order Rajiformes (skates and relatives)
* Order Myliobatiformes (stingrays and relatives)

The 5th edition of Fishes of the World sets out the following classification of the Elasmobranchs:[29]

* Infraclass Elasmobranchii
* Division Selachii (sharks)
* Superorder Galeomorphi
* †Order Synechodontiformes
* Order Heterodontiformes
* Order Orectolobiformes
* Suborder Parascyllioidei
* Suborder Orectoloboidei
* Order Lamniformes
* Order Carcharhiniformes
* Superorder Squalomorphi
* Series Hexanchida
* Order Hexanchiformes
* Series Squalida
* Order Squaliformes
* Series Squatinida
* †Order Protospinaciformes
* Order Echinorhiniformes
* Order Squatiniformes
* Order Pristiophoriformes
* Division Batomorphi (rays)
* Order Torpediniformes
* Order Rajiformes
* Order Pristiformes
* Order Myliobatiformes
* Suborder Platyrhinoidei
* Suborder Myliobatoidei

Recent molecular studies suggest the Batoidea are not derived selachians as previously thought. Instead, skates and rays are a monophyletic superorder within Elasmobranchii that shares a common ancestor with the selachians.[30][31]

## See also

[edit]

* List of Elasmobranch cestodes, tape worms which infect sharks, rays and skates

## References

[edit]

1. ^ "Elasmobranch". Merriam-Webster.com Dictionary. Merriam-Webster.
2. ^ a b Maisey, J. G. (April 2012). "What is an 'elasmobranch'? The impact of palaeontology in understanding elasmobranch phylogeny and evolution". Journal of Fish Biology. 80 (5): 918–951\. Bibcode:2012JFBio..80..918M. doi:10.1111/j.1095-8649.2012.03245.x. PMID 22497368.
3. ^ Vannuccini, Stefania (2002) Shark liver oil products Archived 2013-06-26 at the Wayback Machine In: Shark Utilization, Marketing and Trade, Fisheries Technical paper 389, FAO, Rome. ISBN 92-5-104361-2.
4. ^ Fowler, S.L. (2005). "Cetorhinus maximus". IUCN Red List of Threatened Species. 2005: e.T4292A10763893. doi:10.2305/IUCN.UK.2005.RLTS.T4292A10763893.en.
5. ^ Walker, T.I.; Rigby, C.L.; Pacoureau, N.; Ellis, J.; Kulka, D.W.; Chiaramonte, G.E.; Herman, K. (2020). "Galeorhinus galeus". IUCN Red List of Threatened Species. 2020: e.T39352A2907336. doi:10.2305/IUCN.UK.2020-2.RLTS.T39352A2907336.en. Retrieved 11 November 2021.[permanent dead link]
6. ^ Finucci, B.; Bineesh, K.K.; Cheok, J.; Cotton, C.F.; Dharmadi, Kulka, D.W.; Neat, F.C.; Pacoureau, N.; Rigby, C.L.; Tanaka, S.; Walker, T.I. (2020). "Centrophorus granulosus". IUCN Red List of Threatened Species. 2020: e.T162293947A2897883. doi:10.2305/IUCN.UK.2020-3.RLTS.T162293947A2897883.en. Retrieved 11 November 2021.`{{cite journal}}`: CS1 maint: multiple names: authors list (link)
7. ^ a b Hoenig, J.M. and Gruber, S.H. (1990) "Life-history patterns in the elasmobranchs: implications for fisheries management" Archived 2013-02-18 at the Wayback Machine In: Elasmobranchs as living resources: advances in the biology, ecology, systematics and the status of the fisheries, eds. J. H. L. Pratt, S. H. Gruber and T. Taniuchi, US Department of Commerce, NOAA technical report NMFS 90, pp.1–16.
8. ^ Wilga, C.D. (2005). "Morphology and evolution of the jaw suspension in lamniform sharks". Journal of Morphology. 265 (1): 102–19\. doi:10.1002/jmor.10342. PMID 15880740. S2CID 45227734.
9. ^ Wilga, C. D.; Motta, P. J.; Sanford, C. P. (2007). "Evolution and ecology of feeding in elasmobranchs". Integrative and Comparative Biology. 47 (1): 55–69\. doi:10.1093/icb/icm029. PMID 21672820.
10. ^ Wilga, Cheryl A.D. (2008). "Evolutionary divergence in the feeding mechanism of fishes". Acta Geologica Polonica. 58 (2): 113–20\. Archived from the original on 2018-08-19. Retrieved 2017-05-24.
11. ^ Bigelow, Henry B.; Schroeder, William C. (1948). Fishes of the Western North Atlantic. Sears Foundation for Marine Research, Yale University. pp. 64–65\. ASIN B000J0D9X6.
12. ^ Oguri, M (1990) "A review of selected physiological characteristics unique to elasmobranchs" Archived 2013-02-18 at the Wayback Machine In: Elasmobranchs as living resources: advances in the biology, ecology, systematics and the status of the fisheries, eds. J. H. L. Pratt, S. H. Gruber and T. Taniuchi, US Department of Commerce, NOAA technical report NMFS 90, pp.49–54.
13. ^ Bone, Q.; Roberts, B. L. (2009). "The density of elasmobranchs". Journal of the Marine Biological Association of the United Kingdom. 49 (4): 913. doi:10.1017/S0025315400038017. S2CID 85871565.
14. ^ a b Frey, Linda; Coates, Michael; Ginter, Michał; Hairapetian, Vachik; Rücklin, Martin; Jerjen, Iwan; Klug, Christian (2019-10-09). "The early elasmobranch Phoebodus : phylogenetic relationships, ecomorphology and a new time-scale for shark evolution". Proceedings of the Royal Society B: Biological Sciences. 286 (1912): 20191336. doi:10.1098/rspb.2019.1336. ISSN 0962-8452. PMC 6790773. PMID 31575362.
15. ^ Schultze, H.-P., Bullecks, J., Soar, L. K., & Hagadorn, J. (2021). Devonian fish from Colorado’s Dyer Formation and the appearance of Carboniferous faunas in the Famennian. In A. Pradel, J. S. S. Denton, & P. Janvier (Eds.), Ancient Fishes and their Living Relatives: a Tribute to John G. Maisey (pp. 247–256.). Verlag Dr. Friedrich Pfeil.
16. ^ Maisey, John G.; Bronson, Allison W.; Williams, Robert R.; McKinzie, Mark (2017-05-04). "A Pennsylvanian 'supershark' from Texas". Journal of Vertebrate Paleontology. 37 (3): e1325369. Bibcode:2017JVPal..37E5369M. doi:10.1080/02724634.2017.1325369. ISSN 0272-4634. S2CID 134127771.
17. ^ Pauliv, Victor E.; Martinelli, Agustín G.; Francischini, Heitor; Dentzien-Dias, Paula; Soares, Marina B.; Schultz, Cesar L.; Ribeiro, Ana M. (December 2017). "The first Western Gondwanan species of Triodus Jordan 1849: A new Xenacanthiformes (Chondrichthyes) from the late Paleozoic of Southern Brazil". Journal of South American Earth Sciences. 80: 482–493\. Bibcode:2017JSAES..80..482P. doi:10.1016/j.jsames.2017.09.007.
18. ^ Koot, Martha B.; Cuny, Gilles; Tintori, Andrea; Twitchett, Richard J. (March 2013). "A new diverse shark fauna from the Wordian (Middle Permian) Khuff Formation in the interior Haushi-Huqf area, Sultanate of Oman". Palaeontology. 56 (2): 303–343\. Bibcode:2013Palgy..56..303K. doi:10.1111/j.1475-4983.2012.01199.x. ISSN 0031-0239. S2CID 86428264.
19. ^ Rees, J. A. N., and Underwood, C. J., 2008, Hybodont sharks of the English Bathonian and Callovian (Middle Jurassic): Palaeontology, v. 51, no. 1, p. 117–147.
20. ^ Underwood, Charlie J. (March 2006). "Diversification of the Neoselachii (Chondrichthyes) during the Jurassic and Cretaceous". Paleobiology. 32 (2): 215–235\. Bibcode:2006Pbio...32..215U. doi:10.1666/04069.1. ISSN 0094-8373. S2CID 86232401.
21. ^ Rees, Jan; Underwood, Charlie J. (January 2008). "Hybodont Sharks of the English Bathonian and Callovian (Middle Jurassic)". Palaeontology. 51 (1): 117–147\. Bibcode:2008Palgy..51..117R. doi:10.1111/j.1475-4983.2007.00737.x. ISSN 0031-0239.
22. ^ Carrillo-Briceño, Jorge D.; Cadena, Edwin A.; Dececchi, Alex T.; Larson, Hans C. E.; Du, Trina Y. (2016-01-01). "First record of a hybodont shark (Chondrichthyes: Hybodontiformes) from the Lower Cretaceous of Colombia". Neotropical Biodiversity. 2 (1): 81–86\. Bibcode:2016NeBio...2...81C. doi:10.1080/23766808.2016.1191749. ISSN 2376-6808.
23. ^ Maisey, John G. (March 2011). "The braincase of the Middle Triassic shark Acronemus tuberculatus (Bassani, 1886)". Palaeontology. 54 (2): 417–428\. Bibcode:2011Palgy..54..417M. doi:10.1111/j.1475-4983.2011.01035.x. ISSN 0031-0239. S2CID 140697673.
24. ^ Coates, Michael I.; Tietjen, Kristen (March 2017). "The neurocranium of the Lower Carboniferous shark Tristychius arcuatus (Agassiz, )". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 108 (1): 19–35\. Bibcode:2017EESTR.108...19C. doi:10.1017/S1755691018000130. ISSN 1755-6910. S2CID 135297534.
25. ^ Villalobos-Segura, Eduardo; Stumpf, Sebastian; Türtscher, Julia; Jambura, Patrick; Begat, Arnaud; López-Romero, Faviel; Fischer, Jan; Kriwet, Jürgen (2023-03-08). "A Synoptic Review of the Cartilaginous Fishes (Chondrichthyes: Holocephali, Elasmobranchii) from the Upper Jurassic Konservat-Lagerstätten of Southern Germany: Taxonomy, Diversity, and Faunal Relationships". Diversity. 15 (3): 386. doi:10.3390/d15030386. ISSN 1424-2818. PMC 7614348. PMID 36950327.
26. ^ Luccisano, Vincent; Rambert-Natsuaki, Mizuki; Cuny, Gilles; Amiot, Romain; Pouillon, Jean-Marc; Pradel, Alan (2021-12-02). "Phylogenetic implications of the systematic reassessment of Xenacanthiformes and 'Ctenacanthiformes' (Chondrichthyes) neurocrania from the Carboniferous–Permian Autun Basin (France)". Journal of Systematic Palaeontology. 19 (23): 1623–1642\. Bibcode:2021JSPal..19.1623L. doi:10.1080/14772019.2022.2073279. ISSN 1477-2019.
27. ^ Ebert, David A.; Fowler, Sarah; Dando, Marc (2021). Sharks of the world: a complete guide. Princeton: Princeton University Press. ISBN 978-0-691-20599-1.
28. ^ "WoRMS - World Register of Marine Species - Echinorhiniformes". Retrieved 2022-01-04.
29. ^ Nelson, J.S.; Grande, T.C.; Wilson, M.V.H. (2016). Fishes of the World (5th ed.). Hoboken, NJ: John Wiley & Sons. p. 56\. doi:10.1002/9781119174844. ISBN 978-1-118-34233-6. LCCN 2015037522. OCLC 951899884. OL 25909650M.
30. ^ Winchell, Christopher J; Martin, Andrew P; Mallatt, Jon (2004). "Phylogeny of elasmobranchs based on LSU and SSU ribosomal RNA genes". Molecular Phylogenetics and Evolution. 31 (1): 214–24\. doi:10.1016/j.ympev.2003.07.010. PMID 15019621.
31. ^ Douady, Christophe J.; Dosay, Miné; Shivji, Mahmood S.; Stanhope, Michael J. (2003). "Molecular phylogenetic evidence refuting the hypothesis of Batoidea (rays and skates) as derived sharks". Molecular Phylogenetics and Evolution. 26 (2): 215–21\. doi:10.1016/S1055-7903(02)00333-0. PMID 12565032.

## External links

[edit]

* Skaphandrus.com Elasmobranchii

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Evolution of fish

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Forerunners|

* Basal member
* †Pikaia
* Cephalochordate
* †Cathaymyrus
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* Olfactores
* †Haikouella
* Tunicate
* †Myllokunmingiidae? (†Haikouichthys, †Myllokunmingia)
* †Zhongxiniscus?

Jawless fish

| Cyclostomata|

* Hagfish
* Hyperoartia
* Lamprey

|

†Conodonts|

* †Protoconodonta?
* †Paraconodontida
* †Conodonta

†Ostracoderms|

* †Pteraspidomorphi
* †Thelodonti
* †Anaspida
* †Cephalaspidomorphi
* †Galeaspida
* †Pituriaspida
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Jawed fish|

| †Placoderms|

* †Antiarchi
* †Arthrodira
* †Brindabellaspida
* †Petalichthyida
* †Phyllolepida
* †Ptyctodontida
* †Rhenanida
* †Acanthothoraci
* †Pseudopetalichthyida?
* †Stensioellida?

|

†Acanthodii|

* †Acanthodiformes
* †"Climatiiformes"
* †Diplacanthiformes
* †Ischnacanthiformes

Cartilaginous|

* Elasmobranchii
* †Ctenacanthiformes
* †Hybodontiformes
* †Phoebodontiformes
* †Xenacanthida
* Ray
* Shark

* Holocephali
* †Eugeneodontida
* †Iniopterygiformes
* †Petalodontiformes
* †Symmoriiformes
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Bony|

| Lobe-finned|

* †Onychodontiformes
* Coelacanth
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* †Porolepiformes
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|

Ray-finned|

* †"Palaeonisciformes"

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Lists|

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* List of transitional fossils

Related|

* Prehistoric life
* Transitional fossils
* Vertebrate paleontology

† extinct

Taxon identifiers

Elasmobranchii|

* Wikidata: Q194257
* Wikispecies: Elasmobranchii
* ADW: Elasmobranchii
* AFD: Elasmobranchii
* BioLib: 15236
* BOLD: 34196
* CoL: LB
* EoL: 1857
* GBIF: 121
* iNaturalist: 47273
* ITIS: 159786
* NCBI: 7778
* NZOR: 66341afb-b617-40fd-b239-6d2f83d2ac9d
* Open Tree of Life: 278117
* Paleobiology Database: 54499
* Plazi: 03923C45-FF85-FF8E-337D-F9ADFE8F17DF
* WoRMS: 10193

Authority control databases: National |

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*[e]: Edit this template
*[†]: Extinct