江苏发现卢氏兔和细齿兽的意义

DISCOVERY OF LUSHILAGUS AND MIACIS IN JIANGSU AND ITS ZOOGEOGRAPHICAL SIGNIFICANCE

江苏溧阳县发现一始新世哺乳动物群,包括12个目.根据其中发现的洛河卢氏兔与卢氏细齿兽,认为该动物群的时代与河南卢氏动物群大致相当,为中始新世末期或晚始新世初期.

An Eocene mammalian fauna is discovered from the fissure fillings in a limestone quarry in Liyang county, Jiangsu Province. So far 12 orders have been recognized in the fauna, including marsupials, primates (3-4 species), notoungulates, rodents, lagomorphs, chiropterans, insectivores, carnivores, tillodonts, creodonts, perissodactyls and artiodactyls, etc. In addition to those, there still are several specimens which can not be identified yet. All the specimens were mainly collected by washing method. The specimens, Lushilagus lohoensis and Miacis lushiensis, are reported and described in this paper. According to the presence of the two species, the age of the fauna is considered to be of the end of the Middle Eocene or the beginning of the Late Eocene. It is approximately equivalent to that of Lushi fauna in Henan Province. Lagomorpha Brandt, 1885 Leporidae Gray, 1821 Palaeoginae Dice, 1929 Lushilagus lohoensis Li, 1965: (Fig. 1) Material V9515: a left P^3 and V9516: right M^1 (Table 1). Discussion Lushilagus lohoensis was first reported by Li (1965). The disgnosis of the p^3 of the species are: 1) non-molarization; 2) double roots; 3) tri-lobe crown pattern. The differences between Lushilagus lohoensis and another species, Lushilagus danjiangensis described by Tong and Lei (1987), on p^3 and p^4 are: the outer root relatively weak and almost closed crescentic valley in the former, while the outer root robust and crescentic valley quite open in the latter. Because of their similarities to Lushilagus lohoensis, we deem that V9515 and V9516 should be referred to this form. Carnivora Bowdich, 1821 Miacidae Cope, 1880 Miacis lushiensis Chow, 1975 (Fig. 2) Material V9517: a left M^1; V9518: a broken lower jaw with P_4 (broken), M_1 and M_2 (Table 2 and 3). Discussion There are three previously known sites of genus Miacis in China: 1) Miacis invictus from Nei Mongol (Matthew and Granger, 1925); 2) Miacis lushiensis from Lushi Formation in Henan Province (Chow, 1975); and 3) Miacis lushiensis from Hetaoyuan Formation in Henan Province (Xu et al., 1979; Tong and Lei, 1986). V9518 bears some resemblances to Miacis lushiensis found in Lushi Formation in two aspects: dimensions and tooth patterns. It is obviously smaller than that of the specimen (V5362) from Hetaoyan Formation. The two M^1: V7999 (Tong and Lei, 1986) and V9717 (this paper) have some differences as follows: 1) V7999: paraconule more prominent; 2) V7999: anterior cingulum more wide; and 3) V7999: hypocone shelf more robust. But the similar character of both (relatively weak postprotocrista) differs from that of Miacis invictus which has a very clear postprotocrista. So that the conclusion is certain: there are at least two distinct species of Miacis in China.