White Matt A, Bell Phil R, Cook Alex G, Poropat Stephen F, Elliott David A
Mechanical Engineering, University of Newcastle , Callaghan, New South Wales , Australia ; Palaeontology, Australian Age of Dinosaurs Museum of Natural History , Winton, Queensland , Australia.
School of Environmental and Rural Science, University of New England , Armidale, New South Wales , Australia.
PeerJ. 2015 Dec 15;3:e1512. doi: 10.7717/peerj.1512. eCollection 2015.
Megaraptorid theropods were an enigmatic group of medium-sized predatory dinosaurs, infamous for the hypertrophied claw on the first manual digit. Megaraptorid dentition is largely restricted to isolated teeth found in association with skeletal parts; however, the in situ maxillary dentition of Megaraptor was recently described. A newly discovered right dentary pertaining to the Australovenator holotype preserves in situ dentition, permitting unambiguous characterisation of the dentary tooth morphology. The new jaw is virtually complete, with an overall elongate, shallow profile, and fifteen visible in situ teeth at varying stages of eruption. In situ teeth confirm Australovenator exhibited modest pseudoheterodonty, recurved lateral teeth with a serrate distal carina and reduced mesial carina, similar to other megaraptorids. Australovenator also combines of figure-of-eight basal cross-section with a lanceolate shape due to the presence of labial and lingual depressions and the lingual twist of the distal carina. Computed tomography and three-dimensional imagery provided superior characterisation of the dentary morphology and enabled an accurate reconstruction to a pre-fossilised state. The newly established dental morphology also afforded re-evaluation of isolated theropod teeth discovered at the Australovenator holotype locality and from several additional Winton Formation localities. The isolated Winton teeth are qualitatively and quantitatively similar to the in situ dentary teeth of Australovenator, but are also morphometrically similar to Abelisauridae, Allosauridae, Coelophysoidea, Megalosauridae and basal Tyrannosauroidea. Qualitative characters, however, clearly distinguish the teeth of Australovenator and the isolated Winton teeth from all other theropods. Evidence from teeth suggests megaraptorids were the dominant predators in the Winton Formation, which contrasts with other penecontemporaneous Gondwanan ecosystems.
巨盗龙类兽脚亚目恐龙是一群神秘的中型掠食性恐龙，因其第一指上的巨大爪子而声名狼藉。巨盗龙类的牙齿大多仅限于与骨骼部分相关联的孤立牙齿；然而，最近对巨盗龙的原位上颌牙齿进行了描述。新发现的与南方猎龙模式标本相关的右侧齿骨保存了原位牙齿，从而能够明确描述齿骨牙齿的形态。新的颌骨几乎完整，整体呈细长、浅的轮廓，有十五颗处于不同萌出阶段的可见原位牙齿。原位牙齿证实南方猎龙表现出适度的假异形齿，外侧牙齿向后弯曲，远端有锯齿状嵴，近中嵴退化，这与其他巨盗龙类相似。由于存在唇侧和舌侧凹陷以及远端嵴的舌侧扭转，南方猎龙还具有八边形的基部横截面和披针形的形状。计算机断层扫描和三维成像提供了对齿骨形态的更优描述，并能够准确重建到化石形成前的状态。新确定的牙齿形态也使得对在南方猎龙模式标本产地以及温顿组其他几个产地发现的孤立兽脚亚目恐龙牙齿进行重新评估成为可能。温顿组的孤立牙齿在定性和定量上与南方猎龙的原位齿骨牙齿相似，但在形态测量上也与阿贝力龙科、异特龙科、腔骨龙超科、斑龙科和基础暴龙超科相似。然而，定性特征清楚地将南方猎龙的牙齿和温顿组的孤立牙齿与所有其他兽脚亚目恐龙区分开来。牙齿证据表明巨盗龙类是温顿组的主要掠食者，这与其他同期的冈瓦纳生态系统形成了对比。
