Cristozoa

Cristozoa
	African elephant ( Loxodonta africana )
Systematics
without rank:	Bilateral animals (bilateria)
without rank:	Nephrozoa
Over trunk :	Neumünder (Deuterostomia)
Trunk :	Chordates (chordata)
without rank:	Olfactores
without rank:	Cristozoa
Scientific name
	Cristozoa
	Chen , 2008

The Cristozoa include all back-string animals (chordates, chordata ) that form a neural crest during their embryonic development . The Cristozoa consist of four groups, three of which are only known from fossils. The only representatives of the Cristozoa still living today are the numerous skull animals (Craniata), which are commonly equated with the vertebrates ( Vertebrata ). Thus include fish , amphibians , sauropsids including birds and mammals , including modern humans to Cristozoa.

features

The common characteristic of all Cristozoa is the neural crest. However, it is only embryonic . Therefore it cannot be used to recognize adult Cristozoa as such. The same difficulty applies to fossils, of which embryonic stages are very rarely found. On the other hand, embryonic cells tie off from the neural crest, which settle in certain regions of the body and form certain tissues and organs there. Such neural crest formations remain visible in the adult organisms and can possibly be identified in fossils. The neural crest formations include, for example, the skin pigment cells ( melanocytes ), certain muscles in the head area and parts of the peripheral nervous system .

Systematics

The Cristozoa represent a group within the system of multicellular animals . Its sister taxon are the tunicata . With them they form the community of descent of the Olfactores . The olfactores are combined with today's lancet fish ( Leptocardia ) to form the back string animals (Chordata).

Four animal groups are assigned to the Cristozoa. Only one of them still exists, so it's recent . However, this surviving group is the cranial animals (Craniata), which developed into a very diverse and widespread lineage.

External classification of the Cristozoa
Chordata (back string animals) Leptocardia (lancet fish) Olfactores Tunicata (tunicates) Cristozoa

Internal systematics of the recent and fossil Cristozoa

Cristozoa

Myllokunmingiida ^a †

Pikaiidae ^b †

	Conodontophora ^c †

	Craniata ^d

A : The skull loose Myllokunmingiida the genera belonged Haikouichthys (= Myllokunmingia ) metaspriggina and Zhongjianichthys . The Myllokunmingiida died out before the end of the Cambrian .
b : The only known genus belonging to the family of the skullless Pikaiidae was Pikaia . The Pikaiidae died out before the end of the Cambrian.
c : The skullless conodont animals ( Conodontophora ) had very resistant mouthparts, which have been preserved in large quantities. Fossils of their soft tissue anatomy have been found extremely rarely. The oldest fossil documented genus is called Protohertzina and came from the Lower Cambrian. The conodont animals died out at the end of the Triassic .
d : The skull animals ( Craniata ) include all Cristozoa with skulls . The oldest fossil documented genus is called Anatolepis and came from the Upper Cambrian.

literature

Nicholas D. Holland, Junyuan Chen: Origin and early evolution of the vertebrates: new insights from advances in molecular biology, anatomy, and palaeontology . In: BioEssays . Volume 23, 2001, doi : 10.1002 / 1521-1878 (200102) 23: 2 <142 :: AID-BIES1021> 3.0.CO; 2-5 , pp. 142-151.
Jun-Yuan Chen: Early Crest Animals and the Insight They Provide Into the Evolutionary Origin of Craniates . In: Genesis . Volume 46, 2008, doi : 10.1002 / dvg.20445 , pp. 623-639.

Individual evidence

^ Gerhard Mickoleit: Phylogenetic systematics of vertebrates . Publishing house Dr. Friedrich Pfeil, Munich 2004, ISBN 3-89937-044-9 , p. 15.
↑ Alessandro Mongera: The Role of Neural Crest in Vertebrate Evolution . Tübingen, 2013, pp. 15-18 ( Link ).
^ Alfred Goldschmid: Deuterostomia . In: Wilfried Westheide, Gunde Rieger (Ed.): Special Zoology Part 1: Protozoa and Invertebrates . Springer-Verlag, Berlin / Heidelberg 2013, ISBN 978-3-642-34695-8 , p. 779.
^ Systematics according to (1a) Jun-Yuan Chen: Early Crest Animals and the Insight They Provide Into the Evolutionary Origin of Craniates . In: Genesis . Volume 46, 2008, doi : 10.1002 / dvg.20445 , p. 623. In combination with (1b) Diego C. García-Bellido, Michael SY Lee, Gregory D. Edgecombe, James B. Jago, James G. Gehling, John R. Paterson: A new vetulicolian from Australia and its bearing on the chordate affinities of an enigmatic Cambrian group . In: BMC Evolutionary Biology . Volume 14, 2014, doi : 10.1186 / s12862-014-0214-z , p. 8. Updated with (1c) Jian Han, Simon Conway Morris, Qiang Ou, Degan Shu, Hai Huang: Meiofaunal deuterostomes from the basal Cambrian of Shaanxi (China) . In: Nature . Volume 542, 2017, doi : 10.1038 / nature21072 , p. 230; "Myllokunmingiida" (instead of "Yunnanozoa") according to Michael J. Benton: Paleontology of the vertebrates . Publishing house Dr. Friedrich Pfeil, Munich 2007, ISBN 978-3-89937-072-0 , p. 53.
↑ Degan Shu: A paleontological perspective of vertebrate origin . In: Chinese Science Bulletin . Volume 48, 2003, doi : 10.1007 / BF03187041 , p. 725.
↑ Hou Xian-gang, Richard J. Aldridge, David J. Siveter, Derek J. Siveter, and Feng Xiang-hong: New evidence on the anatomy and phylogeny of the earliest vertebrates . I. Proceedings of the Royal Society B: Biological Sciences . Volume 269, 2002, doi : 10.1098 / rspb.2002.2104 , p. 1865.
^ Simon Conway Morris, Jean-Bernard Caron: A Primitive Fish from the Cambrian of North America . In: Nature . Volume 512, 2014, doi : 10.1038 / nature13414 , p. 419.
↑ Degan Shu: A paleontological perspective of vertebrate origin . In: Chinese Science Bulletin . Volume 48, 2003, doi : 10.1007 / BF03187041 , p. 727.
^ Simon Conway Morris, Jean-Bernard Caron: Pikaia gracilens Walcott, a stem-group chordate from the Middle Cambrian of British Columbia . In: Biological Reviews . Volume 87, 2012, doi : 10.1111 / j.1469-185X.2012.00220.x , p. 480.
↑ Philip CJ Donoghue, Joseph N. Keating: Early vertebrate evolution . In: Palaeontology . Volume 57, 2014, doi : 10.1111 / pala.12125 , p. 883.
↑ Vladimir V. Missarzhevsky: Conodont-shaped organisms from the Precambrian-Cambrian boundary strata of the Siberian Platform and Kazakhstan. In: IT Zhuravleva (Ed.): Palaeontological and Biostratigraphic Problems in the Lower Cambrian of Siberia and the Far East . Nauka, Novosibirsk 1973, p. 53.
^ M. Paul Smith, Ivan I. Sansom: The affinity of Anatolepis . In: Geobios . Volume 28, 1995, doi : 10.1016 / S0016-6995 (95) 80088-3 , p. 61.

[Mickoleit_15-1] Gerhard Mickoleit: Phylogenetic systematics of vertebrates . Publishing house Dr. Friedrich Pfeil, Munich 2004, ISBN 3-89937-044-9 , p. 15.

[Mongera_15-18-2] Alessandro Mongera: The Role of Neural Crest in Vertebrate Evolution . Tübingen, 2013, pp. 15-18 ( Link ).

[Goldschmid_779-3] Alfred Goldschmid: Deuterostomia . In: Wilfried Westheide, Gunde Rieger (Ed.): Special Zoology Part 1: Protozoa and Invertebrates . Springer-Verlag, Berlin / Heidelberg 2013, ISBN 978-3-642-34695-8 , p. 779.

[Systematik_Cristozoa-4] Systematics according to (1a) Jun-Yuan Chen: Early Crest Animals and the Insight They Provide Into the Evolutionary Origin of Craniates . In: Genesis . Volume 46, 2008, doi : 10.1002 / dvg.20445 , p. 623. In combination with (1b) Diego C. García-Bellido, Michael SY Lee, Gregory D. Edgecombe, James B. Jago, James G. Gehling, John R. Paterson: A new vetulicolian from Australia and its bearing on the chordate affinities of an enigmatic Cambrian group . In: BMC Evolutionary Biology . Volume 14, 2014, doi : 10.1186 / s12862-014-0214-z , p. 8. Updated with (1c) Jian Han, Simon Conway Morris, Qiang Ou, Degan Shu, Hai Huang: Meiofaunal deuterostomes from the basal Cambrian of Shaanxi (China) . In: Nature . Volume 542, 2017, doi : 10.1038 / nature21072 , p. 230; "Myllokunmingiida" (instead of "Yunnanozoa") according to Michael J. Benton: Paleontology of the vertebrates . Publishing house Dr. Friedrich Pfeil, Munich 2007, ISBN 978-3-89937-072-0 , p. 53.

[Shu_725-5] Degan Shu: A paleontological perspective of vertebrate origin . In: Chinese Science Bulletin . Volume 48, 2003, doi : 10.1007 / BF03187041 , p. 725.

[Xian-gang_1865-6] Hou Xian-gang, Richard J. Aldridge, David J. Siveter, Derek J. Siveter, and Feng Xiang-hong: New evidence on the anatomy and phylogeny of the earliest vertebrates . I. Proceedings of the Royal Society B: Biological Sciences . Volume 269, 2002, doi : 10.1098 / rspb.2002.2104 , p. 1865.

[Morris_419-7] Simon Conway Morris, Jean-Bernard Caron: A Primitive Fish from the Cambrian of North America . In: Nature . Volume 512, 2014, doi : 10.1038 / nature13414 , p. 419.

[Shu_727-8] Degan Shu: A paleontological perspective of vertebrate origin . In: Chinese Science Bulletin . Volume 48, 2003, doi : 10.1007 / BF03187041 , p. 727.

[Morris_480-9] Simon Conway Morris, Jean-Bernard Caron: Pikaia gracilens Walcott, a stem-group chordate from the Middle Cambrian of British Columbia . In: Biological Reviews . Volume 87, 2012, doi : 10.1111 / j.1469-185X.2012.00220.x , p. 480.

[Donoghue_883-10] Philip CJ Donoghue, Joseph N. Keating: Early vertebrate evolution . In: Palaeontology . Volume 57, 2014, doi : 10.1111 / pala.12125 , p. 883.

[Missarzhevsky_53-11] Vladimir V. Missarzhevsky: Conodont-shaped organisms from the Precambrian-Cambrian boundary strata of the Siberian Platform and Kazakhstan. In: IT Zhuravleva (Ed.): Palaeontological and Biostratigraphic Problems in the Lower Cambrian of Siberia and the Far East . Nauka, Novosibirsk 1973, p. 53.

[Smith_61-12] M. Paul Smith, Ivan I. Sansom: The affinity of Anatolepis . In: Geobios . Volume 28, 1995, doi : 10.1016 / S0016-6995 (95) 80088-3 , p. 61.