Fossil specimen of Lasanius problematicus, from here.

Belongs within: Chordata.
Contains: Myxinidae, Petromyzontidae, Conodonta, Birkeniida, Pteraspidomorphi, Thelodontomorphi, Gnathostomata.

The Vertebrata are the group of animals including fish, amphibians, reptiles, birds and mammals, characterised by the presence of an internal skeleton with vertebrae. Vertebrates also possess a well-developed brain contained within a cranium. In development, sensory structures in the head region are formed from ectodermal placodes, while neural crest cells give rise to the dermal skeleton, skeletal material of jaws and branchial arches, trabeculae, parts of sensory capsules, pigment cells, some cardiac and aortic-arch motor neurons and some sensory cranial nerves (Bond 1996). Within living vertebrates, our understanding of higher-level phylogeny is relatively stable except for the position of the Myxinidae (hagfish). Morphological studies place hagfish, which possess a cranium but lack vertebrae, outside the vertebrates, but molecular studies place hagfish as sister to Petromyzontidae (lampreys), implying that their lack of some vertebrate synapomorphies may represent a secondary loss.

<==Vertebrata [Cephalaspidomorphi, Hyperoartii, Jamoytiiformes, Monorhina, Myopterygii]
    |--Cyclostomata MW07
    |    |  i. s.: Pipiscius zangerli M96, SCM99
    |    |         Gilpichthyes M96
    |    |--+--Myxinikela siroka GCR06, M96
    |    |  `--Myxinidae MW07
    |    `--+--Euphaneropidae N02
    |       |    |--Euphanerops longaevus Woodward 1900 GCR06, BMM02
    |       |    |--Legendrelepis N02
    |       |    `--Cornovichthys Newman & Trewin 2001 N02
    |       |         `--C. blaauweni Newman & Trewin 2001 N02
    |       `--Petromyzontiformes [Hyperoartia] MW07
    |            |  i. s.: Hardistiella GCR06
    |            |--Mayomyzon GCR06
    |            `--+--Priscomyzon Gess, Coates & Rubidge 2006 GCR06
    |               |    `--*P. riniensis Gess, Coates & Rubidge 2006 GCR06
    |               `--+--Mesomyzon GCR06
    |                  `--Petromyzontidae GCR06
    `--+--Conodonta GCR06
       `--+--Jamoytius kerwoodi White 1946 GCR06, BMM02
          `--+--Anaspida [Anaspidiformes] GCR06
             |    |  i. s.: Ctenopleuron nerepisense Matthew 1907 BMM02
             |    |         Vilkitskilepis valentinae Märss 2002 BMM02
             |    |--Birkeniida BMM02
             |    `--Lasanius Traquair 1898 [Lasaniidae] BMM02
             |         |--L. armatus Traquair 1898 BMM02
             |         `--L. problematicus Traquair 1898 BMM02
             `--+--Pteraspidomorphi GCR06
                `--+--Thelodontomorphi GCR06
                   `--+--+--Gnathostomata MW07
                      |  `--Osteostraci GCR06
                      |       |--Norselaspis glacialis M96
                      |       `--Hirella gracilis M96
                      `--Galeaspida [Galeaspidiformes] GCR06
                           |--Sangiaspis B96
                           |--Polybranchiaspis B96
                           |--Duyunaspis paoyangensis M96
                           `--Eugaleaspis BMM02
                                |--E. changi [=Galeaspis changi] W97
                                `--E. xujiachongensis W97

Vertebrata incertae sedis:
  Boothialepis thorsteinssoni Märss 1999 SM01
  Canonia grossi MG01
  Jianichthys longicephalus ZBH03
  Longdeichthys lujiaxiaensis ZBH03
  Protopsephurus liui ZBH03
  Yanosteus longidorsalis ZBH03
  Irenichthys S02
  Tesseraspis tesselata Wills 1935 BMM02
  Didymaspis Lankester 1867 BMM02
  Paralogania BMM02
    |--P. kummerowi (Gross 1967) BMM02
    `--P. ludlowiensis Gross 1967 SM01
  Cephalaspidiformes B96
    |  i. s.: Hemicyclaspis murchisoni (Egerton 1857) B96, BMM02
    |--Ateleaspidae B96
    |--Tremataspidae B96
    |    |--Tremataspis B96
    |    `--Dartmuthia B96
    `--Cephalaspidae B96
         |--Cephalaspis Agassiz 1835 BMM02
         `--Thyestes egertoni (Lankester 1870) B96, BMM02
  Dipteronotus cythus SS02
  Fagea Buen 1940 C92
  Lophacanthus Stock 1880 C92
  Pezopallichthys [Furcacaudiformes] SM01
    `--P. ritchiei Wilson & Caldwell 1998 SM01
  Angaralepis moskalenkoae K-TS03
  Skiichthys halsteadi K-TS03
  Ebenaqua [Bobasatraniformes] RE01
    `--E. ritchiei Campbell & Duy Phuoc 1983 RE01
  Achanarella Newman 2002 [Achanarellidae] N02
    `--*A. trewini Newman 2002 N02
  Hanilepis wangi W97
  Yunnanolepis W97
    |--Y. chii W97
    `--Y. parvus W97
  Procondylolepis qujingensis W97
  Gantarostrataspis geni W97
  Machaerasthus bohemicus W97
  Hunanolepis tieni JP97
  Clarorbis apponomedianus JP97

*Type species of generic name indicated


[BMM02] Blom, H., T. Märss & C. G. Miller. 2002. Silurian and earliest Devonian birkeniid anaspids from the Northern Hemisphere. Transactions of the Royal Society of Edinburgh: Earth Sciences 92: 263-323.

[B96] Bond, C. E. 1996. Biology of Fishes 2nd ed. Saunders College Publishing: Fort Worth.

[C92] Crawford, R. L. 1992. Catalogue of the genera and type species of the harvestman superfamily Phalangioidea (Arachnida). Burke Museum Contributions in Anthropology and Natural History 8: 1-60.

[GCR06] Gess, R. W., M. I. Coates & B. S. Rubidge. 2006. A lamprey from the Devonian period of South Africa. Nature 443: 981-984.

[JP97] Ji S. & Pan J. 1997. The macropetalichthyids (Placodermi) from Guangxi and Hunan, China. Vertebrata PalAsiatica 35 (1): 18-34.

[K-TS03] Karatajute-Talimaa, V., & M. M. Smith. 2003. Early acanthodians from the Lower Silurian of Asia. Transactions of the Royal Society of Edinburgh: Earth Sciences 93: 277-299.

[M96] Mallatt, J. 1996. Ventilation and the origin of jawed vertebrates: a new mouth. Zoological Journal of the Linnean Society 117: 329-404.

[MW07] Mallatt, J., & C. J. Winchell. 2007. Ribosomal RNA genes and deuterostome phylogeny revisited: more cyclostomes, elasmobranchs, reptiles, and a brittle star. Molecular Phylogenetics and Evolution 43: 1005-1022.

[MG01] Märss, T., & P.-Y. Gagnier. 2001. A new chondrichthyan from the Wenlock, Lower Silurian, of Baillie-Hamilton Island, the Canadian Arctic. Journal of Vertebrate Paleontology 21 (4): 693-701.

[N02] Newman, M. J. 2002. A new naked jawless vertebrate from the Middle Devonian of Scotland. Palaeontology 45 (5): 933-941.

[RE01] Ritchie, A., & G. D. Edgecombe. 2001. An odontogriphid from the Upper Permian of Australia. Palaeontology 44 (5): 861-874.

[SCM99] Shu, D., S. Conway Morris, X.-L. Zhang, L. Chen, Y. Li & J. Han. 1999. A pipiscid-like fossil from the Lower Cambrian of south China. Nature 400: 746-749.

[S02] Sinitshenkova, N. D. 2002. Ecological history of the aquatic insects. In History of Insects (A. P. Rasnitsyn & D. L. J. Quicke, eds) pp. 388-426. Kluwer Academic Publishers: Dordrecht.

[SM01] Soehn, K. L., T. Märss, M. W. Caldwell & M. V. H. Wilson. 2001. New and biostratigraphically useful thelodonts from the Silurian of the Mackenzie Mountains, Northwest Territories, Canada. Journal of Vertebrate Paleontology 21: 651-659.

[SS02] Spencer, P. S., & G. W. Storrs. 2002. A re-evaluation of small tetrapods from the Middle Triassic Otter Sandstone Formation of Devon, England. Palaeontology 45 (3): 447-467.

[W97] Wang N. 1997. Restudy of thelodont microfossils from the lower part of the Cuifengshan Group of Qujing, eastern Yunnan, China. Vertebrata PalAsiatica 35 (1): 1-17.

[ZBH03] Zhou, Z., P. M. Barrett & J. Hilton. 2003. An exceptionally preserved Lower Cretaceous ecosystem. Nature 421: 807-814.

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