Share to:

 

Vertebrate

Vertebrate
Temporal range:
Cambrian Stage 3–Present,
518 –0 Ma[1]
Diversity: a sturgeon (Actinopterygii), an elephant (Tetrapoda), a shark (Chondrichthyes) and a lamprey (Agnatha).
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Superphylum: Deuterostomia
Phylum: Chordata
Clade: Olfactores
Subphylum: Vertebrata
J-B. Lamarck, 1801[2]
Infraphyla
Synonyms

Ossea Batsch, 1788[2]

Vertebrates (/ˈvɜːrtəbrɪts, -ˌbreɪts/)[3] are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain.

The vertebrates make up the subphylum Vertebrata with some 65,000 species, by far the largest grouping in the phylum Chordata. The vertebrates include mammals, birds, amphibians, and various classes of fish and reptiles. The fish include the jawless Agnatha, and the jawed Gnathostomata. The jawed fish include both the cartilaginous fish and the bony fish. Bony fish include the lobe-finned fish, which gave rise to the tetrapods, the animals with four limbs. Vertebrates make up less than five percent of all described animal species.

The first vertebrates appeared in the Cambrian explosion some 518 million years ago. Jawed vertebrates evolved in the Ordovician, followed by bony fishes in the Devonian. The first amphibians appeared on land in the Carboniferous. During the Triassic, mammals and dinosaurs appeared, the latter giving rise to birds in the Jurassic. Extant species are roughly equally divided between fishes of all kinds, and tetrapods. Populations of many species have been in steep decline since 1970 because of land-use change, overexploitation of natural resources, climate change, pollution and the impact of invasive species.

Characteristics

Unique features

Vertebrates belong to the chordates, a phylum characterised by five synapomorphies (unique characteristics), namely a notochord, a hollow nerve cord along the back, an endostyle (often as a thyroid gland), and pharyngeal gills arranged in pairs. Vertebrates share these characteristics with other chordates.[4]

Vertebrates are distinguished from all other animals, including other chordates, by multiple synapomorphies, namely the vertebral column; skull of bone or cartilage, large brain divided into 3 or more sections, a muscular heart with multiple chambers; an inner ear with semicircular canals; sense organs including eyes, ears, and nose; and digestive organs including intestine, liver, pancreas, and stomach.[5]

Physical

See also: Fish anatomy
Idealised vertebrate body plan, showing key characteristics

Vertebrates (and other chordates) belong to the Bilateria, a group of animals with mirror symmetrical bodies.[6] They move, typically by swimming, using muscles along the back, supported by a strong but flexible skeletal structure, the spine or vertebral column.[7] The name 'vertebrate' derives from the Latin vertebratus, 'jointed',[8] from vertebra, 'joint', in turn from Latin vertere, 'to turn'.[9]

Fossilized skeleton (cast) of Diplodocus carnegii, showing an extreme example of the vertebral column that gives the vertebrates their name. The species is a tetrapod, its four legs adapting the fish-like body plan for walking on land. The specimen is 26 m (85 ft) long.

As embryos, vertebrates still have a notochord; as adults, all but the jawless fishes have a vertebral column, made of bone or cartilage, instead.[7] Vertebrate embryos have pharyngeal arches; in adult fish, these support the gills, while in adult tetrapods they develop into other structures.[10][11]

In the embryo, a layer of cells along the back folds and fuses into a hollow neural tube.[12] This develops into the spinal cord, and at its front end, the brain.[12] The brain receives information about the world through nerves which carry signals from sense organs in the skin and body.[13] Because the ancestors of vertebrates usually moved forwards, the front of the body encountered stimuli before the rest of the body, favouring cephalisation, the evolution of a head containing sense organs and a brain to process the sensory information.[14]

Vertebrates have a tubular gut that extends from the mouth to the anus. The vertebral column typically continues beyond the anus to form an elongated tail.[15][16][17]

Branchial arches bearing gills in a pike

The ancestral vertebrates, and most extant species, are aquatic and carry out gas exchange in their gills. The gills are finely-branched structures which bring the blood close to the water. They are positioned just behind the head, supported by cartilaginous or bony branchial arches.[18] In jawed vertebrates, the first gill arch pair evolved into the jaws.[19] In amphibians and some primitive bony fishes, the larvae have external gills, branching off from the gill arches.[20] Oxygen is carried from the gills to the body in the blood, and carbon dioxide is returned to the gills, in a closed circulatory system driven by a chambered heart.[21] The tetrapods have lost the gills of their fish ancestors; they have adapted the swim bladder (that fish use for buoyancy) into lungs to breathe air, and the circulatory system is adapted accordingly.[22] At the same time, they adapted the bony fins of the lobe-finned fishes into two pairs of walking legs, carrying the weight of the body via the shoulder and pelvic girdles.[22]

Vertebrates vary in size from the smallest frog species such as Brachycephalus pulex, with a minimum adult snout–vent length of 6.45 millimetres (0.254 in)[23] to the blue whale, at up to 33 m (108 ft) and weighing some 150 tonnes.[24]

Molecular

Molecular markers known as conserved signature indels in protein sequences have been identified and provide distinguishing criteria for the vertebrate subphylum.[25] Five molecular markers are exclusively shared by all vertebrates and reliably distinguish them from all other animals; these include protein synthesis elongation factor-2, eukaryotic translation initiation factor 3, adenosine kinase and a protein related to ubiquitin carboxyl-terminal hydrolase).[25] A specific relationship between vertebrates and tunicates is supported by two molecular markers, the proteins Rrp44 (associated with the exosome complex) and serine C-palmitoyltransferase. These are exclusively shared by species from these two subphyla, but not by cephalochordates.[25]

Evolutionary history

Cambrian explosion: first vertebrates

Further information: Cambrian explosion
The Cambrian Haikouichthys, 518 mya[26]

Vertebrates originated during the Cambrian explosion at the start of the Paleozoic, which saw a rise in animal diversity. The earliest known vertebrates belong to the Chengjiang biota[27] and lived about 518 million years ago.[1] These include Haikouichthys, Myllokunmingia,[27] Zhongjianichthys,[26] and probably Yunnanozoon.[28] Unlike other Cambrian animals, these groups had the basic vertebrate body plan: a notochord, rudimentary vertebrae, and a well-defined head and tail, but lacked jaws.[29] A vertebrate group of uncertain phylogeny, small eel-like conodonts, are known from microfossils of their paired tooth segments from the late Cambrian to the end of the Triassic.[30] Zoologists have debated whether teeth mineralized first, given the hard teeth of the soft-bodied conodonts, and then bones, or vice versa, but it seems that the mineralized skeleton came first.[31]

Paleozoic: from fish to amphibians

See also: Evolution of fish and Evolution of tetrapods
Acanthostega, a Devonian labyrinthodont, c. 365 mya[32]

The first jawed vertebrates may have appeared in the late Ordovician (~445 mya) and became common in the Devonian period, often known as the "Age of Fishes".[33] The two groups of bony fishes, Actinopterygii and Sarcopterygii, evolved and became common.[34] By the middle of the Devonian, a lineage of sarcopterygii with both gills and air-breathing lungs adapted to life in swampy pools used their muscular paired fins to propel themselves on land.[35] The fins, already possessing bones and joints, evolved into two pairs of walking legs.[36] These established themselves as amphibians, terrestrial tetrapods, in the next geological period, the Carboniferous.[37] A group of vertebrates, the amniotes, with membranes around the embryo allowing it to survive on dry land, branched from amphibious tetrapods in the Carboniferous.[38]

Mesozoic: from reptiles to mammals and birds

Hyperodapedon, a diapsid reptile of the Triassic, c. 230 mya

At the onset of the Mesozoic, all larger vertebrate groups were devastated after the largest mass extinction in earth history. The following recovery phase saw the emergence of many new vertebrate groups that are still around today, and this time has been described as the origin of modern ecosystems. On the continents, the ancestors of modern lissamphibians, turtles, crocodilians, lizards, and mammals appeared, as well as dinosaurs, which gave rise to birds later in the Mesozoic. In the seas, various groups of marine reptiles evolved, as did new groups of fish.[38] At the end of the Mesozoic, another extinction event extirpated dinosaurs (other than birds) and many other vertebrate groups.[39]

Cenozoic: Age of Mammals

Nahmavis, an Eocene bird, c. 50 mya

The Cenozoic, the current era, is sometimes called the "Age of Mammals", because of the dominance of the terrestrial environment by that group. Placental mammals have predominantly occupied the Northern Hemisphere, with marsupial mammals in the Southern Hemisphere.[40][41]

Approaches to classification

Taxonomic history

In 1811, Jean-Baptiste Lamarck defined the vertebrates as a taxonomic group,[2] a phylum distinct from the invertebrates he was studying.[42] He described them as consisting of four classes, namely fish, reptiles, birds, and mammals,[43] but treated the cephalochordates and tunicates as molluscs.[42] In 1866, Ernst Haeckel called both his "Craniata" (vertebrates) and his "Acrania" (cephalochordates) "Vertebrata".[42] In 1877, Ray Lankester grouped the Craniates, cephalochordates, and "Urochordates (tunicates) as "Vertebrata".[42] In 1880–1881, Francis Maitland Balfour placed the Vertebrata as a subphylum within the Chordates.[42] In 2018, Naoki Irie and colleagues proposed making Vertebrata a full phylum.[42]

Traditional taxonomy

Diversity of various groups of vertebrates through the geologic ages. The width of the bubbles signifies the number of families.

Conventional evolutionary taxonomy groups extant vertebrates into seven classes based on traditional interpretations of gross anatomical and physiological traits. The commonly held classification lists three classes of fish and four of tetrapods.[44] This ignores some of the natural relationships between the groupings. For example, the birds derive from a group of reptiles, so "Reptilia" excluding "Aves" is not a natural grouping; it is described as paraphyletic.[45][46]

In addition to these, there are two classes of extinct armoured fishes, Placodermi and Acanthodii, both paraphyletic.

Other ways of classifying the vertebrates have been devised, particularly with emphasis on the phylogeny of early amphibians and reptiles. An example based on work by M.J. Benton in 2004[47] is given here († = extinct):

While this traditional taxonomy is orderly, most of the groups are paraphyletic, meaning that the structure does not accurately reflect the natural evolved grouping.[47] For instance, descendants of the first reptiles include modern reptiles, mammals and birds; the agnathans have given rise to the jawed vertebrates; the bony fishes have given rise to the land vertebrates; a group of amphibians, the labyrinthodonts, have given rise to the reptiles (traditionally including the mammal-like synapsids), which in turn have given rise to the mammals and birds. Most scientists working with vertebrates use a classification based purely on phylogeny, organized by their known evolutionary history.[42]

External phylogeny

It was once thought that the Cephalochordata was the sister taxon to Vertebrata. This group, Notochordata, was taken to be sister to the Tunicata (the Notochordata hypothesis).[48] Since 2006, analysis has shown that the tunicates + vertebrates form a clade, the Olfactores, with Cephalochordata as its sister (the Olfactores hypothesis), as shown in the following phylogenetic tree.[49][50][25]

 Chordata 
 Cephalochordata 

 Amphioxiformes (lancelets)

Olfactores

 Tunicata (sea squirts, etc)

 Vertebrata

Internal phylogeny

The internal phylogeny of the vertebrates is shown in the tree.[51]

Vertebrata

Agnatha

(jawless)
Chondrichthyes

(cartilaginous)
Osteichthyes
(bony fishes)
(jawed)
(backbone)

The placement of hagfishes on the vertebrate tree of life has been controversial. Their lack of proper vertebrae (among other characteristics of jawless lampreys and jawed vertebrates) led phylogenetic analyses based on morphology to place them outside Vertebrata.[52] Molecular data, however, indicates they are vertebrates closely related to lampreys.[53][54] An older view is that they are a sister group of vertebrates in the common taxon of Craniata.[55] In 2019, Tetsuto Miyashita and colleagues reconciled the two types of analysis, supporting the Cyclostomata hypothesis using only morphological data.[56]

†Myllokunmingiida

Vertebrata

†Anaspida

†Pipiscius

†Euconodonta

Cyclostomata (lampreys and hagfishes)

Jawed vertebrates

(crown group)

Diversity

Species by group

Described and extant vertebrate species are split roughly evenly but non-phylogenetically between non-tetrapod "fish" and tetrapods. The following table lists the number of described extant species for each vertebrate class as estimated in the IUCN Red List of Threatened Species, 2014.3.[57] Paraphyletic groups are shown in quotation marks.

Vertebrate groups Image Class Estimated number of
described species[57][58] 		Group
totals[57]
Anamniote

lack
amniotic
membrane
so need to
reproduce
in water 		Jawless "Fish" Myxini
(hagfish) 		78 >32,900
Hyperoartia
(lamprey) 		40
Jawed cartilaginous
fish 		>1,100
ray-finned
fish 		>32,000
"lobe-finned
fish" 		8
Tetrapods amphibians 7,302 33,278
Amniote

have
amniotic
membrane
adapted to
reproducing
on land 		"reptiles" 10,711
mammals 5,513
birds 10,425
Total described species 66,178

The IUCN estimates that 1,305,075 extant invertebrate species have been described,[57] which means that less than 5% of the described animal species in the world are vertebrates.[59]

The Living Planet Index, following 16,704 populations of 4,005 species of vertebrates, shows a decline of 60% between 1970 and 2014.[60] Since 1970, freshwater species declined 83%, and tropical populations in South and Central America declined 89%.[61] The authors note that "An average trend in population change is not an average of total numbers of animals lost."[61] According to WWF, this could lead to a sixth major extinction event.[62] The five main causes of biodiversity loss are land-use change, overexploitation of natural resources, climate change, pollution and invasive species.[63]

See also

References

  1. ^ a b Yang, Chuan; Li, Xian-Hua; Zhu, Maoyan; Condon, Daniel J.; Chen, Junyuan (2018). "Geochronological constraint on the Cambrian Chengjiang biota, South China" (PDF). Journal of the Geological Society. 175 (4): 659–666. Bibcode:2018JGSoc.175..659Y. doi:10.1144/jgs2017-103. S2CID 135091168. Archived (PDF) from the original on 9 October 2022.
  2. ^ a b c Nielsen, C. (July 2012). "The authorship of higher chordate taxa". Zoologica Scripta. 41 (4): 435–436. doi:10.1111/j.1463-6409.2012.00536.x. S2CID 83266247.
  3. ^ "vertebrate". Dictionary.com Unabridged (Online). n.d.
  4. ^ Freeborn, Michelle (2015). Roberts, Clive Douglas; Stewart, Andrew L.; Struthers, Carl D. (eds.). The fishes of New Zealand. Vol. 2. Te Papa Press. p. 6. ISBN 978-0-9941041-6-8.
  5. ^ Farina, Stacy (23 August 2018). "Vertebrate Phylogeny" (PDF). Howard University. Retrieved 7 December 2024.
  6. ^ "Trends in evolution". University of California Museum of Paleontology. Retrieved 10 January 2019.
  7. ^ a b Romer, Alfred S.; Parsons, Thomas S. (1977). The Vertebrate Body. Holt-Saunders. pp. 161–170. ISBN 0-03-910284-X.
  8. ^ "vertebrate". Online Etymology Dictionary.
  9. ^ "Definition of Vertebra". Merriam-Webster. 25 November 2024.
  10. ^ Graham, A. (2003). "Development of the pharyngeal arches". American Journal of Medical Genetics Part A. 119A (3): 251–256. doi:10.1002/ajmg.a.10980. PMID 12784288. S2CID 28318053.
  11. ^ Graham, A. (July 2001). "The development and evolution of the pharyngeal arches". Journal of Anatomy. 199 (Pt 1-2): 133–141. doi:10.1046/j.1469-7580.2001.19910133.x. PMC 1594982. PMID 11523815.
  12. ^ a b Martín-Durán, José M.; Pang, Kevin; Børve, Aina; Lê, Henrike Semmler; Furu, Anlaug; et al. (4 January 2018). "Convergent evolution of bilaterian nerve cords". Nature. 553 (7686): 45–50. doi:10.1038/nature25030. PMC 5756474. PMID 29236686.
  13. ^ "In brief: How does the nervous system work?". InformedHealth.org. 4 May 2023. Retrieved 30 November 2024.
  14. ^ Brusca, Richard C. (2016). "Introduction to the Bilateria and the Phylum Xenacoelomorpha: Triploblasty and Bilateral Symmetry Provide New Avenues for Animal Radiation". Invertebrates (PDF). Sinauer Associates. pp. 345–372. ISBN 978-1605353753.
  15. ^ Handrigan, Gregory R. (2003). "Concordia discors: duality in the origin of the vertebrate tail". Journal of Anatomy. 202 (Pt 3): 255–267. doi:10.1046/j.1469-7580.2003.00163.x. PMC 1571085. PMID 12713266.
  16. ^ Holland, Nicholas D.; Holland, Linda Z.; Holland, Peter W. H. (23 April 2015). "Scenarios for the making of vertebrates". Nature. 520 (7548): 450–455. doi:10.1038/nature14433.
  17. ^ Hejnol, Andreas; Martín-Durán, José M. (2015). "Getting to the bottom of anal evolution". Zoologischer Anzeiger - A Journal of Comparative Zoology. 256: 61–74. doi:10.1016/j.jcz.2015.02.006.
  18. ^ Scott, T. (1996). Concise encyclopedia biology. De Gruyter. p. 542. ISBN 978-3-11-010661-9.
  19. ^ Brazeau, Martin D.; Castiello, Marco; El Fassi El Fehri, Amin; Hamilton, Louis; Ivanov, Alexander O.; et al. (20 November 2023). "Fossil evidence for a pharyngeal origin of the vertebrate pectoral girdle". Nature. 623 (7987): 550–554. Bibcode:2023Natur.623..550B. doi:10.1038/s41586-023-06702-4. hdl:10044/1/107350. PMC 10651482. PMID 37914937.
  20. ^ Szarski, Henryk (1957). "The Origin of the Larva and Metamorphosis in Amphibia". The American Naturalist. 91 (860): 283–301. doi:10.1086/281990. JSTOR 2458911. S2CID 85231736.
  21. ^ Simões-Costa, Marcos S.; Vasconcelos, Michelle; Sampaio, Allysson C.; et al. (2005). "The evolutionary origin of cardiac chambers". Developmental Biology. 277 (1): 1–15. doi:10.1016/j.ydbio.2004.09.026. PMID 15572135.
  22. ^ a b Clack, J. A. (2002). "From Fins to Feet: Transformation and Transition". Gaining ground: the origin and evolution of tetrapods. Indiana University Press. pp. 187–260.
  23. ^ Bolaños, Wendy H.; Dias, Iuri Ribeiro; Solé, Mirco (7 February 2024). "Zooming in on amphibians: Which is the smallest vertebrate in the world?". Zoologica Scripta. 53 (4): 414–418. doi:10.1111/zsc.12654. S2CID 267599475.
  24. ^ Chamary, J.V. (6 June 2024). "How large can animals grow?". BBC Discover Wildlife. Retrieved 29 November 2024.
  25. ^ a b c d Gupta, Radhey S. (January 2016). "Molecular signatures that are distinctive characteristics of the vertebrates and chordates and supporting a grouping of vertebrates with the tunicates". Molecular Phylogenetics and Evolution. 94 (Pt A): 383–391. Bibcode:2016MolPE..94..383G. doi:10.1016/j.ympev.2015.09.019. PMID 26419477.
  26. ^ a b Shu, D. (2003). "A paleontological perspective of vertebrate origin". Chinese Science Bulletin. 48 (8): 725–735. doi:10.1360/03wd0026.
  27. ^ a b Shu, D-G.; Luo, H-L.; Conway Morris, S.; Zhang, X-L.; Hu, S-X.; et al. (1999). "Lower Cambrian vertebrates from south China". Nature. 402 (6757): 42–46. Bibcode:1999Natur.402...42S. doi:10.1038/46965. S2CID 4402854.
  28. ^ Chen, J.-Y.; Huang, D.-Y.; Li, C.-W. (1999). "An early Cambrian craniate-like chordate". Nature. 402 (6761): 518–522. Bibcode:1999Natur.402..518C. doi:10.1038/990080. S2CID 24895681.
  29. ^ Waggoner, B. "Vertebrates: Fossil Record". University of California Museum of Paleontology. Archived from the original on 29 June 2011. Retrieved 15 July 2011.
  30. ^ Donoghue, P. C. J.; Forey, P. L.; Aldridge, R. J. (May 2000). "Conodont affinity and chordate phylogeny". Biological Reviews. 75 (2): 191–251. doi:10.1111/j.1469-185X.1999.tb00045.x. PMID 10881388. S2CID 22803015.
  31. ^ Murdock, Duncan J. E.; Dong, Xi-Ping; Repetski, John E.; Marone, Federica; Stampanoni, Marco; Donoghue, Philip C. J. (2013). "The origin of conodonts and of vertebrate mineralized skeletons". Nature. 502 (7472): 546–549. doi:10.1038/nature12645.
  32. ^ Benton, Michael J. (2019). "Acanthostega". Vertebrate Palaeontology (Kindle ed.). Wiley. p. 90.
  33. ^ Encyclopædia Britannica. Vol. 17. Encyclopædia Britannica. 1954. p. 107.
  34. ^ Berg, L. R.; Solomon, E. P.; Martin, D. W. (2004). Biology. Cengage Learning. p. 599. ISBN 978-0-534-49276-2.
  35. ^ Carroll, Robert L. (1977). Hallam, Anthony (ed.). Patterns of Evolution, as Illustrated by the Fossil Record. Elsevier. pp. 405–420. ISBN 978-0-444-41142-6. Archived from the original on 14 April 2021. Retrieved 15 October 2020.
  36. ^ Narkiewicz, Katarzyna; Narkiewicz, Marek (January 2015). "The age of the oldest tetrapod tracks from Zachełmie, Poland". Lethaia. 48 (1): 10–12. Bibcode:2015Letha..48...10N. doi:10.1111/let.12083.
  37. ^ Hall, Brian K. (15 September 2008). Fins into Limbs: Evolution, Development, and Transformation. University of Chicago Press. p. 209. ISBN 9780226313405. Archived from the original on 9 August 2020. Retrieved 25 April 2020.
  38. ^ a b Benton, Michael (2014). Vertebrate Palaeontology (4th ed.). John Wiley & Sons. pp. 119, 148. ISBN 978-1-118-40764-6.
  39. ^ Fortey, Richard (1999). Life: A Natural History of the First Four Billion Years of Life on Earth. Vintage Books. pp. 238–260. ISBN 978-0-375-70261-7.
  40. ^ Pires, Mathias; Mankin, Brian; Silvestro, Daniele; Quental, Tiago (26 September 2018). "Diversification dynamics of mammalian clades during the K–Pg mass extinction". Biology Letters. 14 (9). doi:10.1098/rsbl.2018.0458. PMC 6170748. PMID 30258031.
  41. ^ Lowery, Christopher; Fraass, Andrew (8 April 2019). "Morphospace expansion paces taxonomic diversification after end Cretaceous mass extinction". Nature Ecology & Evolution. 3 (6): 900–904. Bibcode:2019NatEE...3..900L. doi:10.1038/s41559-019-0835-0. hdl:1983/fb08c3c1-c203-4780-bc90-5994ec1030ff. PMID 30962557. S2CID 102354122 – via Nature.
  42. ^ a b c d e f g Irie, Naoki (26 December 2018). "The phylum Vertebrata: a case for zoological recognition". Zoological Letters. 4 Article Number 32: 32. doi:10.1186/s40851-018-0114-y. PMC 6307173. PMID 30607258.
  43. ^ Blitz, David. "Lamarck and Species Evolution". Central Connecticut State University. Retrieved 7 December 2024.
  44. ^ Campbell, Neil A. (1997). Biology (4th ed.). Benjamin Cummings. p. 632. ISBN 978-0-8053-1940-8.
  45. ^ Farris, James S. (1974). "Formal definitions of paraphyly and polyphyly". Systematic Zoology. 23 (4): 548–554. doi:10.2307/2412474. JSTOR 2412474.
  46. ^ Rieppel, Olivier (2005). "Monophyly, paraphyly, and natural kinds". Biology and Philosophy (20): 465–487. doi:10.1007/s10539-004-0679-z. Something had therefore to be done about the term 'Reptilia.' It could no longer be considered to designate a natural (monophyletic) group without including birds, but only to designate an artificial (non-monophyletic) group
  47. ^ a b Benton, M.J. (1 November 2004). Vertebrate Palaeontology (Third ed.). Blackwell Publishing. p. 33. ISBN 978-0632056378. Archived from the original on 19 October 2008. Retrieved 16 March 2006.
  48. ^ Stach, Thomas (2008). "Chordate phylogeny and evolution: a not so simple three-taxon problem". Journal of Zoology. 276 (2): 117–141. doi:10.1111/j.1469-7998.2008.00497.x.
  49. ^ Delsuc, F. (2006). "Tunicates and not cephalochordates are the closest living relatives of vertebrates" (PDF). Nature. 439 (7079): 965–968. Bibcode:2006Natur.439..965D. doi:10.1038/nature04336. PMID 16495997. S2CID 4382758. Archived (PDF) from the original on 9 October 2022.
  50. ^ Dunn, C.W. (2008). "Broad phylogenetic sampling improves resolution of the animal tree of life". Nature. 452 (7188): 745–749. Bibcode:2008Natur.452..745D. doi:10.1038/nature06614. PMID 18322464. S2CID 4397099.
  51. ^ "Adding time to the tree". Understanding Evolution. University of California Museum of Paleontology. Retrieved 8 December 2024.
  52. ^ Ota, Kinya G.; Fujimoto, Satoko; Oisi, Yasuhiro; Kuratani, Shigeru (25 January 2017). "Identification of vertebra-like elements and their possible differentiation from sclerotomes in the hagfish". Nature Communications. 2: 373. Bibcode:2011NatCo...2..373O. doi:10.1038/ncomms1355. PMC 3157150. PMID 21712821.
  53. ^ Kuraku; Hoshiyama, D.; Katoh, K.; Suga, H.; Miyata, T. (December 1999). "Monophyly of Lampreys and Hagfishes Supported by Nuclear DNA–Coded Genes". Journal of Molecular Evolution. 49 (6): 729–35. Bibcode:1999JMolE..49..729K. doi:10.1007/PL00006595. PMID 10594174. S2CID 5613153.
  54. ^ Stock, D.; Whitt, G. S. (7 August 1992). "Evidence from 18S ribosomal RNA sequences that lampreys and hagfish form a natural group". Science. 257 (5071): 787–789. Bibcode:1992Sci...257..787S. doi:10.1126/science.1496398. PMID 1496398.
  55. ^ Nicholls, H. (10 September 2009). "Mouth to Mouth". Nature. 461 (7261): 164–166. doi:10.1038/461164a. PMID 19741680.
  56. ^ Miyashita, Tetsuto; Coates, Michael I.; Farrar, Robert; Larson, Peter; Manning, Phillip L.; et al. (5 February 2019). "Hagfish from the Cretaceous Tethys Sea and a reconciliation of the morphological–molecular conflict in early vertebrate phylogeny". Proceedings of the National Academy of Sciences of the United States of America. 116 (6): 2146–2151. Bibcode:2019PNAS..116.2146M. doi:10.1073/pnas.1814794116. PMC 6369785. PMID 30670644.
  57. ^ a b c d The World Conservation Union. 2014. IUCN Red List of Threatened Species, 2014.3. Summary Statistics for Globally Threatened Species. Table 1: Numbers of threatened species by major groups of organisms (1996–2014).
  58. ^ Nelson, Joseph S. (2016). Fishes of the World. John Wiley & Sons. pp. 20, 23, 40, 102, 241. ISBN 978-1-118-34233-6.
  59. ^ Zhang, Zhi-Qiang (30 August 2013). "Animal biodiversity: An update of classification and diversity in 2013. In: Zhang, Z.-Q. (Ed.) Animal Biodiversity: An Outline of Higher-level Classification and Survey of Taxonomic Richness (Addenda 2013)". Zootaxa. 3703 (1): 5. doi:10.11646/zootaxa.3703.1.3. Archived from the original on 24 April 2019. Retrieved 2 March 2018.
  60. ^ "Living Planet Report 2018". wwf.panda.org. Retrieved 21 May 2020.
  61. ^ a b Grooten, M.; Almond, R. E. A. (2018). Living Planet Report – 2018: Aiming Higher (PDF). World Wide Fund for Nature. ISBN 978-2-940529-90-2. Archived (PDF) from the original on 9 October 2022.
  62. ^ "WWF Finds Human Activity Is Decimating Wildlife Populations". Time. Retrieved 21 May 2020.
  63. ^ IPBES (25 November 2019). S. Diaz; J. Settele; E.S. Brondízio; H.T. Ngo; M. Guèze; et al. (eds.). Summary for policymakers of the global assessment report on biodiversity and ecosystem services. Bonn: IPBES Secretariat. pp. 1–56. doi:10.5281/zenodo.3553579.

Bibliography

Wikispecies has information related to Vertebrata.
Kembali kehalaman sebelumnya