辽宁早白垩世义县组一新的三尖齿兽类(英文)

A NEW TRICONODONT (MAMMALIA) FROM THE EARLY CRETACEOUS YIXIAN FORMATION OF LIAONING, CHINA

描述了戈壁锥齿兽科 (Gobiconodontidae)一个新的属种———陆家屯弥曼齿兽 (Meeman nodonlujiatunensisgen .etsp .nov.)。标本产于辽宁西部朝阳市上园镇陆家屯下白垩统义县组一段的凝灰质砂岩层中 ,为一具完整齿列的左下颌骨。新属与戈壁锥齿兽 (Gobiconodon)共有以下区别于其他三尖齿兽类的特征 :2颗下门齿 ,i1增大 ,后部门齿、犬齿和前部前臼齿尖锥形 ,前臼齿具有高的中央尖和小的附尖 ,i～p1向前平伏。因此 ,新属被归入戈壁锥齿兽科。弥曼齿兽与戈壁锥齿兽及其相近属的区别在于 :下门齿和下犬齿更加平伏 ,i1在比例上更大 ,而i2则更小 ;最后一枚下前臼齿与第一枚下臼齿之间没有齿隙 ;前臼齿退化 ;下臼齿长度大于高度 ,主尖向后倾斜 ,与b尖和c尖相比 ,a尖较低 ,m1显著小于m2～ 4。新属下臼齿没有齿带 ,与爬兽 (Repenomamus)相似 ,而与戈壁锥齿兽不同。基于与爬兽齿列的对比 ,讨论了戈壁锥齿兽类的齿式 ,认为其应具有两颗门齿 ,而不是以前认为的 1颗门齿 ,从而将戈壁锥齿兽类下齿列齿式修订为 :2·1·2～ 3·5。

A new genus and species of gobiconodotid, Meemannodon lujiatunensis, from the basal member of the Early Cretaceous Yixian Formation at Lujiatun locality , Lianing, northeast China is described. The new genus, Mee,annodon, differs from other triconodonts but is similar to Godiconodon in having enlerged i1, lower incisors reduced to 2, conical and pointed posterior incisors, canines and anterior premolariforms, premolariforms with a tall central cusp but no accessory cusp, and procumbent i ～ p1. It differs from Gobiconodon and its close relatives in having more procumbent lower incisors and canines, proportionally larger i1 and smaller i2, lack of diastema between p2 ( the last premolariform ) and m1, main cusps of molariforms inclined posteriorly, molariform length greater than height, cusp a relatively low comeared to distinct cusps b and c, premolariforms reduced, and m1 signiflcantly smaller than m2～m4. It is similar to Repenomamus but further differs from Gobiconodon in lacking the cingulid on lower molariforms.