中国更新世兔属化石两新种

TWO PLEISTOCENE NEW SPECIES OF LEPUS (LEPORIDAE,LAGOMORPHA) FROM CHINA

中国更新世兔属(Lepus)化石较为丰富,尤其是周口店各化石地点产出了大量的标本。但受条件的限制,缺乏对现生骨骼标本的研究与对比,分类位置混乱或仅鉴定为未定种。详细观察研究了中国科学院动物研究所保存的现生兔属8种的187件头骨标本,归纳整理出Lepus各个种头骨与牙齿特征的个体差异和年龄变化以及稳定的特征。主要稳定特征包括:鼻骨基本形态,如长度、前后相对宽度等;额骨两侧凹陷深浅;眶上突上翘程度;颞窝的深浅及宽度;成年个体上间顶骨愈合,或不完全愈合;门齿前齿沟的形态及白垩质充填的情况;门齿孔宽,腭桥长及翼内窝宽度的比例关系;颧骨高度,浅层咬肌窝及咬肌突腹面三角的形态(反映出咬肌的发育程度);吻部形态;下颌骨基本形态(冠状突、上升支、齿隙骨体、颏孔位置等);颊齿基本形态等。在对现生标本观察研究的基础上,详细描述了周口店第13地点的兔头骨及颅后骨骼,命名一新种德氏兔Lepus teilhardisp. nov.。新种以下列特征区别于已知兔属各种:颅全长平均大于90 mm,眶上突轻微上翘,前支稍短,后支发育;额骨两侧凹陷浅;咬肌突腹面中等大小;颧弓浅层咬肌窝较深;翼内窝宽度明显大于腭桥最小纵径;门齿孔较细长;颞窝上突起较高;枕外结节向下延伸成一低脊;听泡较大;外枕骨较宽,顶视几乎覆盖岩乳骨及部分听泡;I2前齿沟"V"字形,内、外两侧的前缘较平直且几乎持平,充填少量白垩质;下颌骨冠状突倾斜。陕西蓝田陈家窝子发现的翁氏兔(Lepus wongi)也归入该种内。将山东淄博孙家山发现的标本命名为淄博兔Lepus ziboensissp. nov.。该种门齿前齿沟浅窄,充填白垩质;齿隙明显较长;腭桥较长;翼内窝宽度与腭桥长度近乎相等;P2外前褶沟窄浅,内前褶沟亦较浅;p3在1件标本上可见较浅的前内褶沟。根据共生动物群分析,淄博兔的时代为早更新世晚期,参照测年数据德氏兔的时代可能从早更新世晚期至中更新世早期。

Leporids are a group of widely distributed animals with a long history deep into the Middle Eocene. The earliest leporid fossils so far discovered are Lushilagus described by Li （1965） and Tong et al （ 1987 ）. The diversity of Leporidae has never been high during its long history. There are only nine extant genera all over the world, and only one genus, Lepus, is living in China. The most abundant fossil materials of Lepus in China were discovered from Zhoukoudian （Choukoutien） localities with well preserved skulls and postcranial bones （Young, 1927; Teil- hard de Chardin and Pei, 1941 etc. ）. However, identification and systematic study of these fossils have long been hampered by lack of detailed osteological study on the extant species. For a better understanding of the skull characters, the author studied and measured 185 specimens of 8 species of Lepus from China and two specimens of Lepus capensis from South Africa in the collection of Zoology Institute, Chinese Academy of Sciences. Characters with individual variation and/or age differences include ： width of nasal, outline of nasal-frontal suture, size of su- praorbital processes, position of the posterior end of incisor foramen, length of the palatine bridge and width of mesopterygoid fossa, development of the squamosal spine, morphology of the upper occipital, and tooth enamel structures etc. Stable characters on adults include： general outline of nasals, lateral depression on the frontal, elevation of the supraorbital processes, depth and width of the temporal fossa, fusion of interparietal with parietal, shape of the anterior groove of upper incisor and cement filling, width of incisive foramen, length of palatine bridge and width of mesopterygoid fossa, morphology of zygomatic, general outline of lower mandible and cheek teeth.