Biology:Gnathostomata

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Short description: Infraphylum of vertebrates
For the superorder of sea urchins, see Gnathostomata (echinoid). For jaw worms, see Gnathostomulid. Not to be confused with Gnathostoma, a genus of parasitic nematodes

Jawed vertebrates
Temporal range:
Early Silurian–Holocene, 439–0 Ma[1]
(Possible Late Ordovician record, 444 Ma)[1]
Gnathostomata.jpg
Example of jawed vertebrates: Dunkleosteus (Placodermi), Spotted wobbegong (Chondrichthyes), Silver arowana (Osteichthyes) and a Nile crocodile (Tetrapoda).
Scientific classification e
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Olfactores
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Gegenbauer 1874
Subgroups

Gnathostomata (/ˌnæθoʊˈstɒmətə/; from Greek: γνάθος (gnathos) "jaw" + στόμα (stoma) "mouth") are the jawed vertebrates. Gnathostome diversity comprises roughly 60,000 species, which accounts for 99% of all living vertebrates, including humans. In addition to opposing jaws, living gnathostomes have true teeth (a characteristic which has subsequently been lost in some), paired appendages (pectoral and pelvic fins, arms, legs, wings, etc.),[2] the elastomeric protein of elastin,[3] and a horizontal semicircular canal of the inner ear, along with physiological and cellular anatomical characters such as the myelin sheaths of neurons, and an adaptive immune system that has the discrete lymphoid organs of spleen and thymus,[4] and uses V(D)J recombination to create antigen recognition sites, rather than using genetic recombination in the variable lymphocyte receptor gene.[5]

It is now assumed that Gnathostomata evolved from ancestors that already possessed a pair of both pectoral and pelvic fins.[6] Until recently these ancestors, known as antiarchs, were thought to have lacked pectoral or pelvic fins.[6] In addition to this, some placoderms (extinct fish with bony plates) were shown to have a third pair of paired appendages, that had been modified to claspers in males and basal plates in females—a pattern not seen in any other vertebrate group.[7]

The Osteostraci (bony armored jawless fish) are generally considered the sister taxon of Gnathostomata.[2][8][9]

Jaw development in vertebrates is likely a product of the supporting gill arches. This development would help push water into the mouth by the movement of the jaw, so that it would pass over the gills for gas exchange. The repetitive use of the newly formed jaw bones would eventually lead to the ability to bite in some gnathostomes.[10]

Newer research suggests that a branch of Placoderms was most likely the ancestor of present-day gnathostomes. A 419-million-year-old fossil of a placoderm named Entelognathus had a bony skeleton and anatomical details associated with cartilaginous and bony fish, demonstrating that the absence of a bony skeleton in Chondrichthyes is a derived trait.[11] The fossil findings of primitive bony fishes such as Guiyu oneiros and Psarolepis, which lived contemporaneously with Entelognathus and had pelvic girdles more in common with placoderms than with other bony fish, show that it was a relative rather than a direct ancestor of the extant gnathostomes.[12] It also indicates that spiny sharks and Chondrichthyes represent a single sister group to the bony fishes.[11] Fossil findings of juvenile placoderms, which had true teeth that grew on the surface of the jawbone and had no roots, making them impossible to replace or regrow as they broke or wore down as they grew older, proves the common ancestor of all gnathostomes had teeth and place the origin of teeth along with, or soon after, the evolution of jaws.[13][14]

Late Ordovician-aged microfossils of what have been identified as scales of either acanthodians[15] or "shark-like fishes",[16] may mark Gnathostomata's first appearance in the fossil record. Undeniably unambiguous gnathostome fossils, mostly of primitive acanthodians, begin appearing by the early Silurian, and become abundant by the start of the Devonian.

Classification

Gnathostomata is traditionally a infraphylum, broken into three top-level groupings: Chondrichthyes, or the cartilaginous fish; Placodermi, an extinct grade of armored fish; and Teleostomi, which includes the familiar classes of bony fish, birds, mammals, reptiles, and amphibians. Some classification systems have used the term Amphirhina. It is a sister group of the jawless craniates Agnatha.

  Vertebrata  
  Gnathostomata  
 

  †Placodermi  Dunkleosteus terrelli 2023 reconstruction.png

 
  Eugnathostomata  
 

  Acanthodians, incl. Chondrichthyes (cartilaginous fishes)White shark (Duane Raver).png

 
  Euteleostomi  
 

  Actinopterygii  Atlantic sturgeon flipped.jpg

 
  Sarcopterygii  
  Tetrapoda  
 

  Amphibia  Salamandra salamandra (white background).jpg

 
  Amniota  
  Sauropsida  
 

  Sauria  Deinosuchus riograndensis.png

 
 
  Synapsida  
 

  Mammalia  Phylogenetic tree of marsupials derived from retroposon data (Paucituberculata).png

 
 
 
 
 
 
 
 
 
Subgroups of jawed vertebrates
Subgroup Common name Example Comments
† Placodermi
(extinct) 		Armoured fish C cuspidatus.png
Coccosteus
 †Placodermi (plate-skinned) is an extinct class of armoured prehistoric fish, known from fossils, which lived from the late Silurian to the end of the Devonian Period. Their head and thorax were covered by articulated armoured plates and the rest of the body was scaled or naked, depending on the species. Placoderms were among the first jawed fish; their jaws likely evolved from the first of their gill arches. A 380-million-year-old fossil of one species represents the oldest known example of live birth.[17] The first identifiable placoderms evolved in the late Silurian; they began a dramatic decline during the Late Devonian extinctions, and the class was entirely extinct by the end of the Devonian.
Chondrichthyes Cartilaginous fishes Great white shark
Great white shark
 Chondrichthyes (cartilage-fish) or cartilaginous fishes are jawed fish with paired fins, paired nares, scales, a heart with its chambers in series, and skeletons made of cartilage rather than bone. The class is divided into two subclasses: Elasmobranchii (sharks, rays and skates) and Holocephali (chimaeras, sometimes called ghost sharks, which are sometimes separated into their own class). Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates, the extant members of which all fall into Teleostomi.
† Acanthodii
(extinct) 		Spiny sharks Acanthodes BW.jpg
Acanthodes bronni
 †Acanthodii, or spiny sharks are a class of extinct fishes, sharing features with both bony and cartilaginous fishes, now understood to be a paraphyletic assemblage leading to modern Chondrichthyes.[11] In form they resembled sharks, but their epidermis was covered with tiny rhomboid platelets like the scales of holosteans (gars, bowfins). They may have been an independent phylogenetic branch of fishes, which had evolved from little-specialized forms close to recent Chondrichthyes. Acanthodians did, in fact, have a cartilaginous skeleton, but their fins had a wide, bony base and were reinforced on their anterior margin with a dentine spine. They are distinguished in two respects: they were the earliest known jawed vertebrates, and they had stout spines supporting their fins, fixed in place and non-movable (like a shark's dorsal fin). The acanthodians' jaws are presumed to have evolved from the first gill arch of some ancestral jawless fishes that had a gill skeleton made of pieces of jointed cartilage. The common name "spiny sharks" is really a misnomer for these early jawed fishes. The name was coined because they were superficially shark-shaped, with a streamlined body, paired fins, and a strongly upturned tail; stout bony spines supported all the fins except the tail – hence, "spiny sharks". The earliest recorded acanthodian, Fanjingshania renovata,[18] comes from the lower Silurian (Aeronian) of China and it is also the oldest jawed vertebrate with known anatomical features.[18] Coeval to Fanjingshania is the tooth-based acanthodian species Qianodus duplicis[19] that represents the oldest unequivocal toothed vertebrate.
Osteichthyes Bony fishes Blue runner.jpg
Blue runner
 Osteichthyes (bone-fish) or bony fishes are a taxonomic group of fish that have bone, as opposed to cartilaginous skeletons. The vast majority of fish are osteichthyes, which is an extremely diverse and abundant group consisting of 45 orders, with over 435 families and 28,000 species.[20] It is the largest class of vertebrates in existence today. Osteichthyes is divided into the ray-finned fish (Actinopterygii) and lobe-finned fish (Sarcopterygii). The oldest known fossils of bony fish are about 420 million years ago, which are also transitional fossils, showing a tooth pattern that is in between the tooth rows of sharks and bony fishes.[21]
Tetrapoda Tetrapods Deutschlands Amphibien und Reptilien (Salamandra salamdra).jpg
Fire salamander

Evolution

Vertebrate classes
Spindle diagram for the evolution of fish and other vertebrate classes.[22] The earliest classes that developed jaws were the now extinct placoderms and the spiny sharks.

The appearance of the early vertebrate jaw has been described as "a crucial innovation"[23] and "perhaps the most profound and radical evolutionary step in the vertebrate history".[24][25] Fish without jaws had more difficulty surviving than fish with jaws, and most jawless fish became extinct during the Triassic period. However studies of the cyclostomes, the jawless hagfishes and lampreys that did survive, have yielded little insight into the deep remodelling of the vertebrate skull that must have taken place as early jaws evolved.[26][27]

The ancestor of all jawed vertebrates have gone through two rounds of whole genome duplication. The first happened before the gnathostome and cyclostome split, and appears to have been an autopolyploidy event (happened within the same species). The second occurred after the split, and was an allopolyploidy event (the result of hybridization between two lineages).[28]

The customary view is that jaws are homologous to the gill arches.[29] In jawless fishes a series of gills opened behind the mouth, and these gills became supported by cartilaginous elements. The first set of these elements surrounded the mouth to form the jaw. The upper portion of the second embryonic arch supporting the gill became the hyomandibular bone of jawed fish, which supports the skull and therefore links the jaw to the cranium.[30] The hyomandibula is a set of bones found in the hyoid region in most fishes. It usually plays a role in suspending the jaws or the operculum in the case of teleosts.[31]

While potentially older Ordovician records are known, the oldest unambigious evidence of jawed vertebrates are Qianodus and Fanjingshania from the early Silurian (Aeronian) of Guizhou, China around 439 million years ago, which are placed as acanthodian-grade stem-chondrichthyans.[32][33]

References

  1. ↑ 1.0 1.1 Brazeau, M. D.; Friedman, M. (2015). "The origin and early phylogenetic history of jawed vertebrates". Nature 520 (7548): 490–497. doi:10.1038/nature14438. PMID 25903631. Bibcode: 2015Natur.520..490B. 
  2. ↑ 2.0 2.1 Zaccone, Giacomo; Dabrowski, Konrad; Hedrick, Michael S. (5 August 2015). Phylogeny, Anatomy and Physiology of Ancient Fishes. CRC Press. p. 2. ISBN 978-1-4987-0756-5. https://books.google.com/books?id=YmFECgAAQBAJ&pg=PA2. Retrieved 14 September 2016. 
  3. ↑ Rodriguez-Pascual, Fernando (2021-10-27), "The Evolutionary Origin of Elastin: Is Fibrillin the Lost Ancestor?", in Sashank Madhurapantula, Rama; Orgel P.R.O., Joseph; Loewy, Zvi (in en), Extracellular Matrix - Developments and Therapeutics, Biochemistry, 23, IntechOpen, doi:10.5772/intechopen.95411, ISBN 978-1-83968-235-3 
  4. ↑ Mitchell, Christian D.; Criscitiello, Michael F. (December 2020). "Comparative study of cartilaginous fish divulges insights into the early evolution of primary, secondary and mucosal lymphoid tissue architecture". Fish & Shellfish Immunology 107 (Pt B): 435–443. doi:10.1016/j.fsi.2020.11.006. PMID 33161090. 
  5. ↑ Cooper MD, Alder MN (February 2006). "The evolution of adaptive immune systems". Cell 124 (4): 815–22. doi:10.1016/j.cell.2006.02.001. PMID 16497590. 
  6. ↑ 6.0 6.1 Zhu, Min (4 January 2012). "An antiarch placoderm shows that pelvic girdles arose at the root of jawed vertebrates". Biology Letters 8 (3): 453–456. doi:10.1098/rsbl.2011.1033. PMID 22219394. PMC 3367742. https://www.researchgate.net/publication/51984082. 
  7. ↑ "The first vertebrate sexual organs evolved as an extra pair of legs". https://theconversation.com/the-first-vertebrate-sexual-organs-evolved-as-an-extra-pair-of-legs-27578. 
  8. ↑ Keating, Joseph N.; Sansom, Robert S.; Purnell, Mark A. (2012). "A new osteostracan fauna from the Devonian of the Welsh Borderlands and observations on the taxonomy and growth of Osteostraci". Journal of Vertebrate Paleontology 32 (5): 1002–1017. doi:10.1080/02724634.2012.693555. ISSN 0272-4634. https://www2.le.ac.uk/departments/geology/people/purnell-ma/personal/pdfs/Keating_etal2012.pdf. 
  9. ↑ Sansom, R. S.; Randle, E.; Donoghue, P. C. J. (2014). "Discriminating signal from noise in the fossil record of early vertebrates reveals cryptic evolutionary history". Proceedings of the Royal Society B: Biological Sciences 282 (1800): 2014–2245. doi:10.1098/rspb.2014.2245. ISSN 0962-8452. PMID 25520359. 
  10. ↑ Gridi-Papp, Marcos (2018). "Comparative Oral+ENT Biology" (2018). Pacific Open Texts. 4.. Pacific Open Texts. 
  11. ↑ 11.0 11.1 11.2 Min Zhu (10 October 2013). "A Silurian placoderm with osteichthyan-like marginal jaw bones". Nature 502 (7470): 188–193. doi:10.1038/nature12617. PMID 24067611. Bibcode: 2013Natur.502..188Z. 
  12. ↑ Zhu, Min; Yu, Xiaobo; Choo, Brian; Qu, Qingming; Jia, Liantao; Zhao, Wenjin; Qiao, Tuo; Lu, Jing (2012). "Fossil Fishes from China Provide First Evidence of Dermal Pelvic Girdles in Osteichthyans". PLOS ONE 7 (4): e35103. doi:10.1371/journal.pone.0035103. PMID 22509388. Bibcode: 2012PLoSO...735103Z. 
  13. ↑ Choi, Charles Q. (17 October 2012). "Evolution's Bite: Ancient Armored Fish Was Toothy, Too". http://www.livescience.com/24050-ancient-armored-fish-teeth.html. 
  14. ↑ Rücklin, Martin; Donoghue, Philip C. J.; Johanson, Zerina; Trinajstic, Kate; Marone, Federica; Stampanoni, Marco (17 October 2012). "Development of teeth and jaws in the earliest jawed vertebrates" (in en). Nature 491 (7426): 748–751. doi:10.1038/nature11555. ISSN 1476-4687. PMID 23075852. Bibcode: 2012Natur.491..748R. https://www.nature.com/articles/nature11555. 
  15. ↑ Hanke, Gavin; Wilson, Mark (January 2004). "New teleostome fishes and acanthodian systematics". Journal of Vertebrate Paleontology: 187–214. https://www.researchgate.net/publication/258494594. 
  16. ↑ Sansom, Ivan J.; Smith, Moya M.; Smith, M. Paul (15 February 1996). "Scales of thelodont and shark-like fishes from the Ordovician of Colorado". Nature 379 (6566): 628–630. doi:10.1038/379628a0. Bibcode: 1996Natur.379..628S. 
  17. ↑ "Fossil reveals oldest live birth". BBC. 28 May 2008. http://news.bbc.co.uk/2/hi/science/nature/7424281.stm. 
  18. ↑ 18.0 18.1 Andreev, Plamen S.; Sansom, Ivan J.; Li, Qiang; Zhao, Wenjin; Wang, Jianhua; Wang, Chun-Chieh; Peng, Lijian; Jia, Liantao et al. (September 2022). "Spiny chondrichthyan from the lower Silurian of South China" (in en). Nature 609 (7929): 969–974. doi:10.1038/s41586-022-05233-8. ISSN 1476-4687. PMID 36171377. Bibcode: 2022Natur.609..969A. https://www.nature.com/articles/s41586-022-05233-8. 
  19. ↑ Andreev, Plamen S.; Sansom, Ivan J.; Li, Qiang; Zhao, Wenjin; Wang, Jianhua; Wang, Chun-Chieh; Peng, Lijian; Jia, Liantao et al. (September 2022). "The oldest gnathostome teeth" (in en). Nature 609 (7929): 964–968. doi:10.1038/s41586-022-05166-2. ISSN 1476-4687. PMID 36171375. Bibcode: 2022Natur.609..964A. https://www.nature.com/articles/s41586-022-05166-2. 
  20. ↑ Bony fishes SeaWorld. Retrieved 2 February 2013.
  21. ↑ Jaws, Teeth of Earliest Bony Fish Discovered
  22. ↑ Benton, M. J. (2005). Vertebrate Palaeontology (3rd ed.). John Wiley. p. 14. ISBN 9781405144490. https://books.google.com/books?id=VThUUUtM8A4C&q=Benton+2005+%22%27Vertebrate+Palaeontology%22. 
  23. ↑ Kimmel, C. B.; Miller, C. T.; Keynes, R. J. (2001). "Neural crest patterning and the evolution of the jaw". Journal of Anatomy 199 (1&2): 105–119. doi:10.1017/S0021878201008068. PMID 11523812. 
  24. ↑ Gai, Z.; Zhu, M. (2012). "The origin of the vertebrate jaw: Intersection between developmental biology-based model and fossil evidence". Chinese Science Bulletin 57 (30): 3819–3828. doi:10.1007/s11434-012-5372-z. Bibcode: 2012ChSBu..57.3819G. 
  25. ↑ Maisey, J. G. (2000). Discovering Fossil Fishes. Westview Press. pp. 1–223. ISBN 978-0-8133-3807-1. https://books.google.com/books?id=gAiAPwAACAAJ. 
  26. ↑ Janvier, P. (2007). "Homologies and Evolutionary Transitions in Early Vertebrate History". in Anderson, J. S.; Sues, H.-D.. Major Transitions in Vertebrate Evolution. Indiana University Press. pp. 57–121. ISBN 978-0-253-34926-2. https://books.google.com/books?id=WKDuAAAAMAAJ&pg=PA57. 
  27. ↑ Khonsari, R. H.; Li, B.; Vernier, P.; Northcutt, R. G.; Janvier, P. (2009). "Agnathan brain anatomy and craniate phylogeny". Acta Zoologica 90 (s1): 52–68. doi:10.1111/j.1463-6395.2008.00388.x. 
  28. ↑ Hagfish genome illuminates vertebrate whole genome duplications and their evolutionary consequences
  29. ↑ For example: (1) both sets of bones are made from neural crest cells (rather than mesodermal tissue like most other bones); (2) both structures form the upper and lower bars that bend forward and are hinged in the middle; and (3) the musculature of the jaw seem homologous to the gill arches of jawless fishes. (Gilbert 2000)
  30. ↑ Gilbert (2000). Evolutionary Embryology. Sinauer Associates. https://www.ncbi.nlm.nih.gov/books/NBK10049/. 
  31. ↑ Clack, J. A. (1994). "Earliest known tetrapod braincase and the evolution of the stapes and fenestra ovalis". Nature 369 (6479): 392–394. doi:10.1038/369392a0. Bibcode: 1994Natur.369..392C. 
  32. ↑ Andreev, Plamen S.; Sansom, Ivan J.; Li, Qiang; Zhao, Wenjin; Wang, Jianhua; Wang, Chun-Chieh; Peng, Lijian; Jia, Liantao et al. (September 2022). "Spiny chondrichthyan from the lower Silurian of South China". Nature 609 (7929): 969–974. doi:10.1038/s41586-022-05233-8. PMID 36171377. Bibcode: 2022Natur.609..969A. https://www.nature.com/articles/s41586-022-05233-8. 
  33. ↑ Andreev, Plamen S.; Sansom, Ivan J.; Li, Qiang; Zhao, Wenjin; Wang, Jianhua; Wang, Chun-Chieh; Peng, Lijian; Jia, Liantao et al. (2022-09-28). "The oldest gnathostome teeth". Nature 609 (7929): 964–968. doi:10.1038/s41586-022-05166-2. ISSN 0028-0836. PMID 36171375. Bibcode: 2022Natur.609..964A. http://dx.doi.org/10.1038/s41586-022-05166-2. 

External links

Wikidata ☰ Q26214 entry



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