# 蜥臀目[编辑]

| 蜥臀目 化石时期：三叠纪晚期至现今,可能还有三疊紀中期的记录
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| 始盗龙的骨架
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| 科学分类  |
| 界： | 动物界 Animalia |
| 门： | 脊索动物门 Chordata |
| 纲： | 蜥形纲 Sauropsida |
| 总目： | 恐龍總目 Dinosauria |
| 目： | **蜥臀目 Saurischia** Seeley, 1887 |
| 演化支
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| * †艾沃克龍屬 *Alwalkeria*
* †艾雷拉龍科 Herrerasauridae
* †邪靈龍屬 *Daemonosaurus*
* †太陽神龍屬 *Tawa*
* †欽迪龍屬 *Chindesaurus*
* †跳龍屬 *Saltopus*?
* †曙奔龍屬 *Eodromaeus*
* **真蜥臀類 Eusaurischia**
	+ †蜥腳形亞目 *Sauropodomorpha*
	+ 獸腳亞目 Theropoda
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**蜥臀目**（學名**Saurischia**）也稱為**龍盤目**或**蜥盤目**。名稱源自希臘文中的*σαυρος*（*sauros*；「蜥蜴」之意）與*ισχιον*（*ischion*；「髖關節」之意）。是恐龍之下所屬兩目中的其中一目。哈利·絲萊（Harry Seeley）在1888年根據恐龍的骨盆結構，將恐龍分類成為兩大目，分別是蜥臀目與鳥臀目（Ornithischia）。兩者的差異在於蜥臀目的骨盆型態比較接近早期的恐龍，蜥臀目恐龍從三疊紀晚期開始出現，與鳥臀目演化支分開個別演化，牠們所生存的時代一直延續到白堊紀結束為止。

蜥臀目之下的獸腳亞目包含了所有的肉食性恐龍，而蜥腳形亞目則是體型龐大的植食性動物演化支；兩者和鳥臀類最大的不同就是“幾乎沒有裝甲或者角”，體型簡單的由頭、頸部、身體、四肢、尾巴組成，就算有也不會像鳥臀目一樣有誇張的裝飾或者防禦特征。某些蜥臀目中的獸腳亞目大約在侏儸紀時期演變成為鳥類的祖先（雖然鳥臀目也擁有類似鳥類的骨盆結構，但是這是趨同演化的結果，並非鳥臀目進化為鳥類）。除了已經演變成為鳥類的分支之外，白堊紀晚期的白堊紀-第三紀滅絕事件使蜥臀目恐龍完全消失。依據系統發生學的分類法，現代鳥類是蜥臀目中獸腳亞目的一個次演化支。

## 敘述

蜥臀目的骨盆結構（左側）
蜥臀目恐龍具有三叉的骨盆結構，恥骨往前。鳥臀目恐龍演化出新的臀部結構，恥骨往後轉到與坐骨平行，並有一個往前的突起，形成四叉的骨盆結構。

鳥臀目的臀部結構類似鳥的臀部結構，這成為牠們的名稱來源，但牠們並不是現代鳥類的直系祖先。近年的研究多認為，蜥臀目（手盜龍類）在侏羅紀時期演化出鳥類。某些手盜龍類的先進物種改變骨盆結構，形成類似鳥臀目骨盆的平行排列，這是種平行演化的結果。

## 分類歷史

哈利·絲萊在在恐龍分為蜥臀目、鳥臀目之前，曾經參考過其他古生物學家提出的恐龍分類方案。哈利·絲萊傾向於奧塞內爾·查利斯·馬什（Othniel Charles Marsh）在1878年的分類法，馬什將恐龍分為四目：蜥腳目（Sauropoda）、獸腳目（Theropoda）、鳥腳目（Ornithopoda）、以及劍龍目（Stegosauria）。

哈利·絲萊希望能夠根據有效的特徵，以更系統的方式將恐龍分類。他根據骨盆的形狀，將上述四目分為兩個群體；新建立的鳥臀目包含鳥腳亞目、劍龍亞目，而蜥臀目包含獸腳亞目、蜥腳亞目。哈利·絲萊認為這兩種骨盆的差異大，代表恐龍並非一個天然演化支，而是主龍類的兩個獨自演化的目。哈利·絲萊的恐龍複系群理論相當有影響力，長期被科學文獻、大眾讀物沿用。直到1960年代，科學界才發現蜥臀目、鳥臀目具有最近共同祖先，而恐龍是個單系群。

另一方面，哈利·絲萊的分類法經過長時間的考驗，近年的親緣分支分類法更支持此一分類法。羅伯特·巴克（Robert Bakker）曾對此分類法提出異議，他在《*The Dinosaur Heresies*》一書中，將獸腳亞目獨立為個別的目，並將蜥腳形亞目與鳥臀目集合為另一個目「Phytodinosauria」（意為「植物恐龍」）或是「Ornithischiformes」。羅伯特·巴克根據慢龍類同時具有鳥臀目與原蜥腳類的特徵，而認為鳥臀目、原蜥腳類是近親，而鳥臀目演化自原蜥腳類恐龍。但近年的研究發現，慢龍類其實是群獨特的植食性獸腳類恐龍，而且是鳥類的近親。因此，巴克的分類方案已不被採用。

### 分類

* 恐龍總目 Dinosauria
	+ **蜥臀目 Saurischia**
		- ?始盜龍 *Eoraptor*
		- ?艾雷拉龍類 Herrerasauria
		- 蜥腳形亞目 Sauropodomorpha
			* 原蜥腳下目 Prosauropoda
			* 蜥腳下目 Sauropoda
		- 獸腳亞目 Theropoda
			* 腔骨龍超科 Coelophysoidea
			* 角鼻龍類 Ceratosauria
			* 堅尾龍類 Tetanurae
				+ 斑龍超科 Megalosauroidea
				+ 肉食龍下目 Carnosauria
				+ 虛骨龍類 Coelurosauria
					- 暴龍超科 Tyrannosauroidea
					- 手盜龍形類 Maniraptoriformes

另外，巴西大龍（*Teyuwasu*）與*Agnosphitys*可能代表早期蜥臀目恐龍，或是更原始的非恐龍動物。

### 種系發生學

蜥臀目在不同分類法的系統發育位置
| Müller & Garcia, 2020
 | Novas *et al.*, 2021
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| 恐龍總目
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| **蜥臀目** |

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†艾雷拉龍科  |
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†邪靈龍屬  |
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†太陽神龍屬  |
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†跳龍屬  |
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†始馳龍屬  |
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| **真蜥臀類** |

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†蜥腳形亞目  |
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獸腳亞目  |
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|  | †鳥臀目 (包括 "西里龍科")  |
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| 龍群類
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†西里龍科  |
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| 恐龍總目
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†鳥臀目  |
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| **蜥臀目** |

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| †Herrerasauria
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†邪靈龍屬  |
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†艾雷拉龍科  |
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| **真蜥臀類** |

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|  | †蜥腳形亞目  |
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| 擬議的鳥腿龍類， 傳統上分類為蜥臀目的分類單元顯示為綠色.
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| Baron *et al.*, 2017
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| 龍群類
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†西里龍科  |
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†艾雷拉龍科  |
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†蜥腳形亞目  |
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| (=蜥腳形亞目; =Pachypodosauria)
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| 鳥腿龍類 |

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†鳥臀目  |
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| 龍群類
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† 西里龍科 (包括*皮薩諾龍屬*)  |
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| † Herrerasauria
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† *太陽神龍屬*  |
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† *邪靈龍屬*  |
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† 艾雷拉龍科  |
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| 恐龍總目
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† 蜥腳形亞目  |
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† *始馳龍屬*  |
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## 參考資料