中国第一个完整的锯齿龙头骨

中国已经命名了7种锯齿龙,但是没有一个有完整的头骨。本文描述一个产自鄂尔多斯盆地孙家沟组的新材料,包括一个近于完整头骨及关连的下颌。根据下列特征将其归入埃尔金龙科(Elginiidae):头骨的膜质骨突起形成长而尖的角,面颊上装饰有显著的锥型角,上颞骨角从头骨一角向侧后方伸出,副基蝶骨细长且腹面中间有凹沟,案骨加大并在中间相互接触,使后顶骨不参与形成头骨边缘。该标本与矮小三川龙(Sanchuansaurus pygmaeus)有下列共同特征:鼻孔后的上颌骨前背支有小的突起,上颌齿齿冠扇形,9—11个齿尖;但是有以下特征区别于后者:眶下神经两个外开口距离更近且更接近上颌骨腹缘,齿冠不重叠,只有14个牙槽。与柳林黄河龙(Huanghesaurus)共有以下特征:下颌腹缘直、光滑,隅骨突位于后缘,下颌齿有中脊,17个齿尖;不过其下颌前部厚度比后部大。新标本表明三川龙和黄河龙关系接近,两者都应可能属于埃尔金龙科。根据新标本建立一个新种并暂时归入石千峰龙属,即完整石千峰龙(Shitienfenia completus);但是目前不能排除这个标本属于二叠石千峰龙的可能性。

THE FIRST COMPLETE PAREIASAUR SKULL FROM CHINA

Although seven pareiasaur species have been named from China, none of them is represented by well-preserved cranial material. Here we briefly describe a new material from Ordos Basin, it includes a nearly complete skull with occluding mandibles. This specimen can be referred to Elginiidae by dermal bosses of cranial bones that have a long and pointed horn, cheek ornamentation in the form of prominent conical horns, supratemporal horn projecting posterolaterally from corner of skull table, slender parabasisphenoid with median, ventral groove, and enlarged tabulars (supernumerary bones) that contact each other medially, thereby excluding the postparietals from the caudal margin of the skull roof. It shares the following features with Sanchuansaurus pygmaeus: a small boss on the maxillary anterodorsal process posterior to the naris, maxillary teeth with fan-shaped crown, 9~11 cusps; and differs from the latter by two exits for the infraorbital canal on the lateral surface are closer and more ventrally (close to the alveoli margin), crown nearly not overlapped, only 14 alveoli (tooth sockets). It shares unique features on the mandible with Huanghesaurus liulinensis for the ventral margin of the mandible nearly straight, the angular with a boss towards the posterior end, dentary teeth with ~17 cusps, the midline bulge ascends the medial face of the crown. The previous cladistics analyses do not support a closely relationship of Huanghesaurus with Elgiidae, but the new specimen supports a closely relationship between Sanchuansaurus and Huanghesaurus, and both should be a member of Elginiidae. The new specimen is referred to Shitienfenia as a new species, S. completus. However, it is also possibly belonged to Shitienfenia permica while Sanchuansaurus pygmaeus and Huanghesaurus liulinensis are valid species. Recently, many skeletons have been collected from the same locality, they will help to resolve the interrelationships of Shitienfenia, Huanghesaurus, and Sanchuansaurus.