新疆准噶尔盆地发现世界最大的亚洲足迹

The largest species of Asianopodus footprints from Junggar Basin, Xinjiang, China

在新疆准噶尔盆地西北缘乌尔禾地区下白垩统吐谷鲁群胜金口组,发现保存在灰绿色细砂岩层面上的13个恐龙足迹,形成3条行迹和4个孤立足迹.通过对足迹、行迹特征的详细观察研究,识别出两种足迹类型,其中大型三趾型足迹为一兽脚类足迹新种.依据其尺寸大(长47.0~56.0 cm、宽31.0~42.0 cm)、趾行式、无拇趾印迹和尾迹、轴对称、V字形、蹠趾垫(脚跟)明显等特征,将其归入实雷龙足迹科(Eubrontidae)亚洲足迹属,并建立一个新种:Asianopodus niui ichnosp.nov.(牛氏亚洲足迹),这是目前发现的最大亚洲足迹.中型三趾型足迹相对较小(长21.0~27.0 cm、宽18.0~20.0 cm)、趾行式、无拇趾印迹和尾迹、轴对称、外侧趾间角为46.63°~51.40°、蹠趾垫印迹明显,归入跟垫亚洲足迹(Asianopodus pulvinicalx).相关分析表明,两种足迹类型的造迹恐龙都处于漫步状态,行走于滨浅湖环境.

A discovery has been made where thirteen footprints,two invertebrate traces and symmetrical ripple marks were found in a greyish green calcareous fine sandstone bed.The discovery was found in the Lower Cretaceous Shengjinkou Formation of Urho area,northwestern Junggar Basin,Xinjiang and it formed three trackways and four isolated tracks.Classic methods were used to study the dinosaur footprints in the Urho area,which included measuring the stratigraphic sections and the footprint parameters in the field.Similar standards of measurements were used for the measurement of footprint length and width,digit length and width,the divarication between digits,the length and width of anterior triangle,pace and stride lengths.In addition,photos of each footprint were taken and the orientation and distance between the neighboured tracks were measured.Distributions and outlines of the footprints were drawn in the computer by using Corel DRAW.On the other hand,silicone rubber demould was used for the well preserved specimens for a detailed research and from the detailed study of the footprints and trackways,two different types of theropod footprints were identified.The large three-toed footprints were a new species,named Asianopodus niui ichnosp.nov.,which are large sized tridactyl(47.0–56.0 cm long and 31.0–42.0 cm wide,width/length between 0.66–0.75),the divarication between digitsⅡandⅣis 49.00°–55.34°,subsymmetrical,digitⅢis slightly longer than digitⅡ,but more longer than digitⅣ,the length/width of anterior triangle between 0.34–0.37,Ⅴ-shape tracks with a distinct bulbous heel impression,without manus and tail impressions,the phalangeal formula is 3-3-2,the pace length is between 164–180 cm,the stride length is 328–336 cm.It is significant to note that this is the largest Asianopodus footprints that have been discovered.The medium-sized tracks belong to Asianopodus pulvinicalx,which are middle sized tridactyl(21.0–27.0 cm long and 18.0–20.0 cm wide,width/length between 0.72–0.86),the divarication between digitsⅡandⅣis 46.63°–51.40°,subsymmetrical,digitⅢis more longer than digitⅡand digitⅣ,the length/width of anterior triangle between 0.44–0.54,V-shape tracks with a distinct bulbous heel impression and without manus and tail impressions,the phalangeal formula is 3-3-3,the pace length is between76.5–83.2 cm,the stride length is 160 cm.According to the footprint length,pace and stride length,relative stride length of the tracks,we calculated that the body length of A.niui ichnosp.nov.is 5.89 m and the speed is 8.14 km/h,while the body length of A.pulvinicalx is 2.52 m and speed is 6.48 km/h.Based on the symmetric ripple marks and invertebrate traces on the surface of the footprints layer,we infered that both the trackmakers of the Urho dinosaur footprints walked in the shore and shallow lacustrine environment.