山东莒南后左山恐龙公园早白垩世恐龙足迹化石初步研究

Early Cretaceous dinosaur tracks from the Houzuoshan Dinosaur Park in Junan County- Shandong Province- China

山东省莒南县后左山恐龙公园内保存了数量众多、形态各异的恐龙足迹化石。该足迹化石群产于早白垩世大盛群田家楼组,主要是兽脚类、鸟脚类恐龙的足迹,尤以前者占优质。最大的一个为椭圆形,大小100cm×70cm,可能系鸟脚类恐龙的足迹。鸟脚类足迹大多为椭圆形,长轴一般30～40cm,常呈幻迹保存。最大的兽脚类足迹为三趾型,长49cm,宽35cm,是大型肉食龙类的足迹;最小的一个长8.5cm,宽4.5cm,可能是虚骨龙类的足迹。另外还发现了少量可能是驰龙的足迹,具有2个很长的趾(Ⅲ和Ⅳ趾),趾间角极小,二者几乎平行。鸟脚类恐龙足迹层位分布局限,但密度较大,产出的层面常发育泥裂、波痕,甚至冰晶痕,与泥岩、粉砂质泥岩等层位相关性较强。

Abundant and diverse dinosaur tracks, associated with small numbers of fossil bird tracks, were discovered in the Tianjialou Formation of the Early Cretaceous Dasheng Group in the Houzuoshan Dinosaur Park, Junan County, Shandong Province. Preliminary study shows that the ichnofauna is mainly theropod and ornithopod tracks, with the former predominating. The largest one is elliptical in shape, 100 cm long and 70 cm wide, which is probably a ornithopod track. The ornithopod tracks are mostly elliptical in shape, the long axis being generally 30 to 40 cm long, and are usually preserved as undertracks. The largest theropod track in this tracksite is a tridactyl track, 49 cm long by 35 cm wide, attributable to carnosaurs. Furthermore, several possible dromaeosaurid tracks were also recognized, which are bidactyl, with digits Ⅲ and Ⅳ nearly parallel to each other and the so-called digit Ⅱ forming nodes at the inner proximal part of digit Ⅲ. The horizon of ornithopod tracks is of restricted distribution but the tracks are close-spaced. Mud cracks, ripples and even ice-crystal imprints are common on the bedding planes, which is closely related to mudstone and silty mudstone.