# 原口动物[编辑]

| 原口动物 化石时期：埃迪卡拉纪到現在
 |
| --- |
|  |
| 对虾
 |
| 科学分类  |
| 界： | 动物界 Animalia |
| 演化支： | 副同源异形基因动物 ParaHoxozoa |
| 演化支： | 两侧对称动物 Bilateria |
| 演化支： | 腎管動物 Nephrozoa |
| 演化支： | **原口动物 Protostomia** |
| 演化支
 |
| * 蜕皮动物总门 Ecdysozoa
* 螺旋动物 Spiralia
 |

**原口动物**（学名：Protostomia）又名**前口動物**或**舊口動物**，是两侧对称动物的一个大分支，也是已知的真核生物中最大的一个类群。其特征是有完整单向的消化道，胚胎时期的原口会发展为成体的口，而肛门则是另外形成的。原口动物主要分蜕皮动物（Ecdysozoa）和螺旋动物（Spiralia）两大演化支。其卵裂方式为螺旋式，因其不均匀分裂会导致中间有一个时期，出现四个大细胞（Macromere）和四个小细胞（Micromere）。该类动物若具有体腔，则体腔是由中胚层形成的。

具体与另一有完整消化道的两侧对称动物演化支——后口动物之间的区别，请参看后口动物条目。

## 演化树

以下为与**原口动物**（及姐妹群后口动物）相关的支序演化树示意图。 演化支出现距今的年代以百万年为单位（Mya）记。

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 肾管动物 Nephrozoa
 |

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 后口动物
 |

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 脊索动物门
 |

|  |  |
| --- | --- |
|  |
头索动物亚门 Cephalochordata  |
|  |
| 嗅球类
 |

|  |  |
| --- | --- |
|  |
被囊动物亚门 Urochordata (tunicates)  |
|  |
|  |
脊椎动物 Vertebrata/Craniata  |
|  |

 |
| Olfactores
 |

 |
| Chordata
 |
| 步带动物Ambulacraria
 |

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 棘皮动物
 |

|  |  |
| --- | --- |
|  |
海百合 Crinoidea  |
|  |
|  |

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

|  |  |
| --- | --- |
|  |
海星 Asteroidea  |
|  |
|  |
蛇尾 Ophiuroidea  |
|  |

 |
|  |
|  |

|  |  |
| --- | --- |
|  |
海胆 Echinoidea  |
|  |
|  |
海参 Holothuroidea  |
|  |

 |
|  |

 |
|  |

 |
| Echinodermata
 |
| 半索动物门
 |

|  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
| 羽鳃纲
 |

|  |  |
| --- | --- |
|  |
头盘虫科 Cephalodiscidae  |
|  |
|  |
Rhabdopleuridae  |
|  |

 |
| Pterobranchia
 |
| 肠鳃纲
 |

|  |  |
| --- | --- |
|  |
玉钩虫科 Harrimaniidae  |
|  |
|  |

|  |  |
| --- | --- |
|  |
无翼柱头虫科 Spengelidae

 |
|  |
| Ptychoderidae
 |

|  |  |
| --- | --- |
|  |
殖翼柱头虫科 Ptychoderidae  |
|  |
|  |
Torquaratoridae  |
|  |

 |
|  |

 |
|  |

 |
| Enteropneusta
 |

 |
| Hemichordata
 |

 |
| 526 mya
 |

 |
| Deuterostomia
 |
| **原口动物 Protostomia** |

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 蛻皮动物 Ecdysozoa
 |

|  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
| 有棘動物
 |

|  |  |
| --- | --- |
|  |
鳃曳动物门 Priapulida  |
|  |
|  |
动吻动物门 Kinorhyncha  |
|  |

 |
| Scalidophora
 |
|  |

|  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
| 線蟲動物
 |

|  |  |
| --- | --- |
|  |
线虫动物门 Nematoda  |
|  |
|  |
线形虫动物门 Nematomorpha  |
|  |

 |
| Nematoida
 |
|  |

|  |  |
| --- | --- |
|  |
铠甲动物门 Loricifera  |
|  |
| 泛节肢动物 Panarthropoda
 |

|  |  |
| --- | --- |
|  |
有爪动物 Onychophora  |
|  |
| 序足動物
 |

|  |  |
| --- | --- |
|  |
缓步动物门 Tardigrada  |
|  |
|  |
节肢动物 Arthropoda  |
|  |

 |
| Tactopoda
 |

 |
|  |

 |
|  |

 |
|  |

 |
| >529 mya
 |
| 螺旋动物 Spiralia
 |

|  |  |
| --- | --- |
|  |
有顎動物 Gnathifera  |
|  |
| 扁虫动物
 |

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

|  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- |
| 吮食動物
 |

|  |  |
| --- | --- |
|  |
腹毛动物门 Gastrotricha  |
|  |
|  |
扁形動物門 Platyhelminthes  |
|  |

 |
| Rouphozoa
 |
|  |
中生動物 Mesozoa  |
|  |

 |
|  |
| 冠轮动物
 |

|  |  |
| --- | --- |
|  |
环口动物门 Cycliophora  |
|  |
| 环节动物门
 |

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

|  |  |
| --- | --- |
|  |
螠蟲目 Echiura

 |
|  |
|  |

|  |  |
| --- | --- |
|  |
环带纲 Clitellata  |
|  |
|  |
西伯加蟲科 Siboglinidae  |
|  |

 |
|  |

 |
|  |
|  |
星虫动物纲 Sipuncula

 |
|  |

 |
| Annelida
 |
|  |

|  |  |
| --- | --- |
|  |
软体动物门 Mollusca  |
|  |
|  |
隱擔輪動物 Kryptotrochozoa  |
|  |

 |
|  |

 |
| Lophotrochozoa
 |

 |
| Platytrochozoa
 |

 |
|  |
|  |
金伯拉虫 Kimberella († 555 mya)  |
|  |

 |
| 550 mya
 |

 |
| 575 mya
 |

## 参考资料