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描述了陕西蓝田晚中新世灞河组的松鼠类和林跳鼠类。松鼠科化石包括3个种:骊山花鼠(新种)Eutamias lishanemis sp.nov.,细小岩松鼠(新种)Sciurotamias pusillus sp.nov.和松鼠属(未定种)Sciurus sp.;林跳鼠科有两个种:西安脊仓跳鼠(新种)Lophocricetus xianensis sp.nov.和脊仓跳鼠(未定种)Lophocricetus sp.。在牙齿的形态上,蓝田松鼠科的新种分别与现生花鼠(Eutamias sibiricus)和岩松鼠(Sciurotamias davidianus)很相似,但特征原始。其中Sciurotamias pusillus新种代表了该属最早的地史记录;Lophocricetus xianensis新种比内蒙古最晚中新世常见的葛氏脊仓跳鼠(Lophocricetus grabaui)原始得多,为中国现知较为原始的一种。这些新种的特征如下:骊山花鼠(Eutamias listmnensis):个体比现生花鼠(Eutamias sibiricus)稍大,前臼齿和第三臼齿的尺寸比现生种的相对大。P4具完整的前边脊,明显臼齿化;上臼齿的原尖较收缩,中附尖不发育;M3无后脊;下臼齿的下内尖几乎融汇于后边脊,下中尖很小。细小岩松鼠(Sciurotamias pusillus):岩松鼠属中个体较小的一种,齿尖和齿脊比Sciurota- mias wangi和S.leilaoensis的高且较强壮。P4似三角形,前附尖膨大;M1/2的原尖收缩,时见小的后小尖和中附尖;m1/2的下内尖界限模糊,唇侧谷窄浅;m3明显向后扩展。西安脊仓跳鼠(Lophocricetus xianensts):Lophocricetus属中个体较小的一种,M1和M2具小或脊状的原附尖,m1和m2的外附尖和齿带不甚发育。M1的中尖通常弱,中脊短,内脊连接前尖或原脊,后边脊连接后脊;M2常见双前边脊,中脊伸达齿缘;m1下外脊的后部低、弱甚至断开,下次尖与下内尖或下中尖与下内尖间的脊连接;m2的下原尖连接下后尖或前边脊。脊仓跳鼠是中亚和北亚特有的一属啮齿动物,被认为从异蹶鼠属(Heterosminthus)演化而来,近10余年来有较多的发现和研究。本文特别对其系统关系进行了探讨,对属种的区分作了进一步界定。哺乳动物的研究显示,陕西蓝田地区晚中新世早期的气候可能比现代还要干旱。灞河动物群中松鼠类和林跳鼠类的出现,还表明了在这个温带开阔的草原环境中,尚有一些灌丛和林地。
The squirrels and jumpers in Late Miocene Tahe Formation in Lantian, Shaanxi Province are described. There are 3 species of squirrel fossils: Eutamias lishanemis sp.nov, Sciurotamias pusillus sp. Nov and Sciurus sp., Sciurus sp. There are two species: Lophocricetus xianensis sp.nov. And Lophocricetus sp. In terms of the morphology of the teeth, the new species of Lantian squirrel is similar to Eutamias sibiricus and Sciurotamias davidianus, respectively, but the characteristics are primitive. Among them, the new species of Sciurotamias pusillus represented the earliest recorded history of the genus; the new species of Lophocricetus xianensis is much more primitive than the late-Miocene Lophocricetus grabaui in Inner Mongolia, Species. The characteristics of these new species are as follows: Eutamias listmnensis: The individual is slightly larger than the Eutamias sibiricus, the size of the premolar and third molars is relatively large compared to the present-day species. P4 with a complete anterior ridge, obvious molars; molar on the original point of the contraction more, in the apex is not developed; M3 no posterior ridge; inferior musculature of the lower tip almost converge in the back of the ridge, the next tip is very small. Sciurotamias pusillus: A lesser individual in the genus Ixodes, with a higher and stronger tip and cusp than the Sciurota mias wangi and S. leilaoensis. P4 resembles a triangle with anterior apical enlargement; M1 / 2 apex retracts, with small apical and apical apices; m1 / 2 inferior apical boundaries blurred and labial valleys narrowed; . Lophocricetus xianensts (Lophocricetus xianensts): Lophocricetus is a smaller one, M1 and M2 have small or ridge-shaped prongs, and m1 and m2 are not well-developed. M1 is usually weak in the tip, the spine is short, the anterior ridge connected to the spine or ridges, the posterior ridge connected to the spine; M2 common double anterior ridge, the spine extends up to the tooth edge; m1 lower posterior ridge of the ridge low or weak Off, the next tip and the next tip or under the tip and the next tip of the ridge connection between the ridge; m2 under the tip of the next connection of the tip or the front ridge. Chinenaria, a rodent peculiar to Central Asia and North Asia, is believed to have evolved from the genus Heterosminthus and has been discovered and studied for more than 10 years. In this paper, the system relations are discussed in detail, and the distinction of genus is further defined. Mammal studies show that the Lantian region in Shaanxi may be arid in the early Paleo-Miocene climate than in modern times. The appearance of squirrels and jumpers in the Tuanhe fauna also showed that there are still some shrubs and woodlands in this temperate open grassland environment.