| Bilaterais |
| --- |
| *Stenopus hispidus* |
| Clasificación científica |
| 

|  |  |
| --- | --- |
| Reino: | Animalia |
| División: | Eumetazoa |
| Clase: | **Bilateria** |

 |
| Phyla |
| * Orthonectida
* Rhombozoa
* Acoelomorpha
* Chaetognatha
* **Superfilo Deuterostomia**
	+ Chordata
	+ Hemichordata
	+ Echinodermata
	+ Xenoturbellida
	+ Vetulicolia †
* ***Protostomia (sen rango)***
	+ **Superfilo Ecdysozoa**
		- Scalidophora (sen rango)
			* Kinorhyncha
			* Loricifera
			* Priapulida
		- Nematoda
		- Nematomorpha
		- Panarthropoda (sen rango)
			* Lobopodia †
				+ Onychophora
				+ Tardigrada
			* Arthropoda
	+ **Superfilo Platyzoa**
		- Platyhelminthes
		- Gastrotricha
		- Rotifera
		- Acanthocephala
		- Gnathostomulida
		- Micrognathozoa
		- Cycliophora
	+ **Superfilo Lophotrochozoa**
		- Sipuncula
		- Hyolitha †
		- Nemertea
		- Phoronida
		- Bryozoa
		- Entoprocta
		- Brachiopoda
		- Mollusca
		- Annelida
		- Echiura
 |

Os **bilaterais** (**Bilateria**) son os animais con simetría bilateral, na cal o organismo é simétrico respecto a un plano (*plano saxital*) que divide o corpo en dúas metades idénticas en espello. Polo tanto, estes seres teñen unha parte dianteira e unha traseira (eixe anterior-posterior), así como unha dorsal e outra ventral (eixe dorsal-ventral). Este tipo de simetría é o máis estendido no reino animal.

Os animais evolutivamente máis primitivos e que teñen un tipo de vida sedentario posúen unha simetría radial en cambio os animais que teñen unha vida activa precisan da simetría bilateral para poder desenvolver as súas actividades. Para os animais radiados un lado do animal é tan importante como calquera outro pero se o individuo é activo precisa estar en busca de alimento, refuxio, lugares de repouso, e compañeiros de reprodución, todo isto require un conxunto de estratexias e dunha organización nova do corpo cunha forma alongada, con cabeza (anterior) e rematando nunha cola (posterior), en definitiva, unha estrutura bilateral do corpo. 
Todos os filos triblásticos presentan simetría bilateral, aínda que secundariamente poidan perdela en estado adulto, como sucede nos equinodermos.

Filoxenia
---------

Hai cando menos dous superfilos de Bilaterais. Os *deuteróstomos* que inclúen os equinodermos, Hemicordados, Cordados e posiblemente algúns filos menores, e os *protóstomos* que inclúen o resto dos bilaterais, como artrópodos, anélidos, moluscos, e outros seres vivos. Hai unha serie de diferenzas, principalmente na forma como o embrión se desenvolve. Unha das máis importantes consiste na apertura do embrión que tórnase en boca en protóstomos e ano en deuteróstomos.

Moitos taxonomistas recoñecen agora polo menos dous superfilos entre os protóstomos: *Ecdysozoa* e *Lophotrochozoa*. Outros taxonomistas recoñecen tamén outro Superfilo dentro dos protóstomos chamado *Platyzoa*, mentres que outros dicen que os Platyzoa están dentro dos Lophotrochozoa e outros non os inclúen en ningún Superfilo.

A filoxenia dos bilaterais proposta por Nielsen (2001) é a seguinte (hai que ter en conta que isto non concorda coa caixa taxonómica que está neste artigo xa que nesta árbore clasifícase, por exemplo, a Phoronida e Brachiopoda como Deuteróstomos en vez Protóstomos) Unha filoxenia alternativa suxire un grupo basal chamada *Ecdysozoa*.


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|   | 

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| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Protostomia | 

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Spiralia | 

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Schizocoelia | 

|  |  |
| --- | --- |
|   | Sipuncula |
|   |
| Articulata | 

|  |  |
| --- | --- |
|   | Mollusca |
|   |
| Euarticulata | 

|  |  |
| --- | --- |
|   | Annelida |
|   |
| Panarthropoda | 

|  |  |
| --- | --- |
|   | Onychophora |
|   |
|   | 

|  |  |
| --- | --- |
|   | Tardigrada |
|   |
|   | Arthropoda |
|   |

 |
|   |

 |
|   |

 |
|   |

 |
|   |

 |
|   |
| Bryozoa | 

|  |  |
| --- | --- |
|   | Ectoprocta |
|   |
|   | Entoprocta |
|   |

 |
|   |
| Parenchymia | 

|  |  |
| --- | --- |
|   | Platyhelminthes |
|   |
|   | Nemertini |
|   |

 |
|   |
| Gnathifera | 

|  |  |
| --- | --- |
|   | Chaetognatha |
|   |
|   | 

|  |  |
| --- | --- |
|   | Gnathostomulida |
|   |
|   | Rotifera |
|   |

 |
|   |

 |
|   |

 |
|   |
| Cycloneuralia | 

|  |  |
| --- | --- |
|   | Gastrotricha |
|   |
| Introverta | 

|  |  |
| --- | --- |
|   | Nematoda |
|   |
|   | Nematomorpha |
|   |

 |
|   |
| Cephalorhyncha | 

|  |  |
| --- | --- |
|   | Priapulida |
|   |
|   | 

|  |  |
| --- | --- |
|   | Kinorhyncha |
|   |
|   | Loricifera |
|   |

 |
|   |

 |
|   |

 |
|   |

 |
|   |
| Deuterostomia | 

|  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
|   | 

|  |  |
| --- | --- |
|   | Phoronida |
|   |
|   | Brachiopoda |
|   |

 |
|   |
|   | 

|  |  |
| --- | --- |
|   | Echinodermata |
|   |
|   | Pterobranchia |
|   |
|   | 

|  |  |
| --- | --- |
|   | Enteropneusta |
|   |
|   | Chordata |
|   |

 |
|   |

 |
|   |

 |
|   |

 |
|   |

Notas
-----

1. ↑  "The Invertebrate Animals". Arquivado dende o orixinal o 10 de marzo de 2010. Consultado o 11 de decembro de 2009.
2. ↑  Nielsen, C. 2001. Animal Evolution: Interrelationships of the Living Phyla. Second Edition. Oxford University Press, Oxford.

Véxase tamén
------------

|  |  |
| --- | --- |
|  | Wikimedia Commons ten máis contidos multimedia na categoría:  ***Bilateral Modificar a ligazón no Wikidata*** |

### Bibliografía

* Hickman, C. Roberts, L. e Larson, A. *Integrate principes of zoology* (2001), 11 edición. Ed McGraw-Hill, Nova York, ISBN 0-07-290961-7

### Ligazóns externas

* Tree of Life web project — Bilateria Arquivado 16 de novembro de 2020 en Wayback Machine. *(en inglés)*
* University of California Museum of Paleontology — Sistemática dos Metazoos *(en inglés)*

|  |  |
| --- | --- |
| Control de autoridades | 
* Wd: Q5173
* EBID: ID
* GND: 4283392-9
* MAG: 2777738586

 |

|  |  |
| --- | --- |
| Identificadores taxonómicos | 
* ADW: Bilateria
* EOL: 3014411
* Fossilworks: 67103
* iNaturalist: 506553
* ITIS: 914154
* NCBI: 33213

 |

|  |  |
| --- | --- |
| Identificadores | 
* UMLS: C1004398

 |