据国外媒体报道，目前，考古学家最新研究揭开了与恐龙同时期存在爬行动物恩吐龙(aetosaurs)物种的真实面目，他们依据这些物种化石证据分析其行为特征颇似鳄鱼、母牛和犰狳的混合体，同时，他们发现在其泄殖腔附近环绕着锋利的刺状突起，它们如何进行交配生殖仍是一个谜团。
这项发现发表在近期出版的《脊椎动物古生物学期刊》（Journal of Vertebrate Paleontology）中，特别是恩吐龙物种中的正体龙(Typothorax)，它是恐龙成为地球霸主之前较大的食草动物之一。它是2.3亿-2亿年前一种8英尺长、225磅重的爬行动物，它们的身体上覆盖着重厚的甲层和锋利的刺状突起。美国新墨西哥国家历史科学博物馆的马修·塞伦斯基说：“考古学家曾挖掘发现三叠纪末期的多数恐龙物种，比如：像火鸡般大小的腔骨龙，它们太过于瘦脊，难以对覆盖厚甲的正体龙构成威胁。”
塞伦斯基解释称，现已灭绝的恩吐龙之后进化为两个分支：恐龙和近亲物种，鳄鱼的祖先和近亲物种。而正体龙正是后一个分支。
近期，两位考古学家在美国新墨西哥州荒原上发现两具正体龙骨骼残骸，他们分析显示正体龙从头部至脚趾都覆盖着坚硬的甲层。期间他们获得一项惊人发现，锋利的刺状突起环绕在泄殖腔(这一生理结构包括肠道、生殖器和泌尿道)。
令考古学家置疑的是正体龙如何进行交配？塞伦斯基称，我们并不知道这些环绕在泄殖腔周围锋利的刺状突起如何影响交配行为，尽管我们确信这两只正体龙可实现正常交配繁殖。
通过分析两具正体龙骨骼，考古学家发现这种爬行动物长着短而粗的脖颈，钝状鼻头和小型叶状牙齿。前肢可伸展，后肢较大且直立。美国阿巴拉契亚大学地质教授安迪·海克特称，正体龙主要的掠食对象可能是半水栖植龙。(生物谷Bioon.com)
生物谷推荐原文出处：
Journal of Vertebrate Paleontology DOI: 10.1080/02724631003763524
Articulated skeletons of the aetosaur Typothorax coccinarum Cope (Archosauria: Stagonolepididae) from the Upper Triassic Bull Canyon Formation (Revueltian: early-mid Norian), eastern New Mexico, USA
Andrew B. Heckert a; Spencer G. Lucas b; Larry F. Rinehart b; Matthew D. Celeskey b; Justin A. Spielmann b;Adrian P. Hunt b
a Department of Geology, Appalachian State University, Boone, North Carolina, U.S.A.
b New Mexico Museum of Natural History and Science, Albuquerque, New Mexico, U.S.A.
We report two nearly complete, articulated skeletons of the crurotarsan archosaur Typothorax coccinarum from the Upper Triassic Bull Canyon Formation of east-central New Mexico. These are the most complete, articulated aetosaurs from North America and provide a wealth of new anatomical and paleobiological data, including articulated presacral armor that confirms the distinctiveness of T. coccinarum from the closely related T. antiquum and from Redondasuchus. Cervical vertebrae are small, but the corresponding reduction in armor is accomplished by a reduced number of cervical osteoderms. The third row of osteoderms includes a thin, elongate, lateral spike. The ventral armor consists of 10 thoracic columns and four caudal columns of osteoderms. Spiked osteoderms near the cloacal vent are the first spikes reported in aetosaurian ventral osteoderms. The forelimb of T. coccinarum was very short, only ～0.65 the length of the hind limb, possesses some adaptations found in digging taxa, and was held in a sprawling or 'semi-erect' position. In contrast the hind limb is much more robust, 'pillar erect,' and functionally mesotarsal. The articulated pes, including unguals, has, minimally, the phalangeal formula 2-3-3?-4?-3? with relative digit lengths III > II > IV > I > V, digits I-IV equally as wide as long and other characteristics of the footprint ichnogenus Brachychirotherium, often attributed to an aetosaurian trackmaker. Both specimens are ～2.5 m long and the preserved armor and limb bones are as large or larger than known Typothorax fossils, suggesting that this approximates the upper size limit of T. coccinarum, and we calculate body mass estimates of ～100-104 kg for both specimens.
