恐龙形类（Dinosauriformes）意为「恐龙」+「外形」，是鸟颈类主龙的一个演化支，包含恐龙与其最近亲，因此不包含恐龙形态类（Dinosauromorpha）的基础物种。恐龙形类的鉴定特征包含：较短的前肢、至少部份开口的髋臼（Acetabulum）…。其中，马拉鳄龙、兔鳄、伪兔鳄生存于三叠纪拉丁尼阶的阿根廷。西里龙生存于卡尼阶的波兰。塞龙生存于诺利阶的巴西。目前已知最早的物种是阿希利龙，生存于约2亿4500万年前，相当于三叠纪中期的安尼西阶。

在1992年，奥尼拉斯·诺瓦斯（Fernando Novas）创建这个分类单元，并创建演化支定义。奥尼拉斯·诺瓦斯当时将这名称包含恐龙与艾雷拉龙下目，诺瓦斯认为艾雷拉龙下目不属于恐龙。之后的大部分古动物学家，将艾雷拉龙下目归类于恐龙，而将恐龙形类包含恐龙与其最近亲。

Dinosauriformes is a clade of archosaurian reptiles that include the dinosaurs and their most immediate relatives. All dinosauriformes are distinguished by several features, such as shortened forelimbs and a partially to fully perforated acetabulum, the hole in the hip socket traditionally used to define dinosaurs. The oldest known member is Asilisaurus, dating to about 245 million years ago in the Anisian age of the middle Triassic period.