中国原大羚化石的再研究

RESTUDY OF CHINESE FOSSIL BOVIDS REFERRED TO PROTORYX(BOVIDAE,ARTIODACTYLA)

在研究新发现化石材料及对已有标本重新观察的基础上,讨论中国晚中新世至早上新世原大羚(?Protoryx)的系统分类位置。依据头骨、角心和牙齿等方面所具有的独特性状,建议把发现于中国北方曾归入?Protoryx的种类从旧大陆同时代或时代稍早的Protoryx Major, 1891中分出,另立2个新属:以?Protoryx yushensis Teilhard&Trassaert,1938为属型种的华北羚(Huabeitragus gen．nov．)和以?Protoryx shansiensis Bohlin,1935为属型种的粗壮羚(Macro- tragus gen．nov．)。华北羚体型中等大小,头骨窄长,颅轴与面轴夹角近直角,弯曲发生在角前的额部,眶上孔小,分开远,脑颅部短窄,间顶骨长方形,基枕骨方形,没有中纵沟或中嵴,角心长而纤细,基部靠近,向上分散度大,基部横断面近三角形,具前棱。Macrotragus头骨大而粗壮,其弯曲发生在角心基部之间的额面,弯曲度大于直角;角基之间的额中缝隆起呈脊;脸部宽;眶前窝浅;眶下孔后缘位于P3之上。眼眶向头骨两侧突出不明显,其前缘位于M3后缘之后;脑颅部短宽,呈简状,背面稍凸;枕面高、呈半圆形;基枕部为长方形或梯形,具中纵沟和弱的中纵脊;卵圆孔大,面向侧方;角心大而粗壮,内外侧扁,无棱,基部紧靠,向上的分散度小,基部横切面为椭圆形。无角后窝。前臼齿列退化。这两个属之间的主要不同在于前者的个体较小;角心较细弱,向上分散度大(前面观),具前棱,基部横切面呈次三角形;头骨窄,其弯曲位置靠前,弯曲接近90°;脑颅部窄;枕面平,为低矮的长方形;基枕部呈方形,面平,无中纵沟和中纵脊,前、后节结不发育和卵圆孔相对小等。在系统位置上,它们可能属于山羊亚科(Caprinae)。

Based on newly discovered materials and old collections we review one important bovid group previously referred to ？ Protoryx.Detailed comparison with other forms from western Eurasia suggests that all the Protoryx forms tound in China can be separated into two groups, which are both different from other forms described as Late Miocene or earlier species of Protoryx.Hence, we propose two new genera, Huabeitragus gen. nov., and Macrotragus gen. nov. in this paper. Huabeitragus has a strongly bent cranial braincase, which makes the cranial axis interact with the facial axis at a right angle. The turning point occurs at the fontal anterior to the horn bases. The supraorbital foramina are small and widely set apart. There is a raised ridge along the frontal suture between the horn cores. The braincase is short and narrow. The occipital surface is low and wide, facing posteriorly. The basiocci- pital is rectangular with a flat or slightly concave surface, without a developed longitudinal groove or ridge, and the anterior and posterior tuberosities less developed. The horn cores have anterior keels and subtriangular shaped cross sections. The horn cores are very divergent upwards in anterior view. Macrotrgus has a large skull and horn cores. The facial, orbital, and cranial parts are wide. The upper orbital rims do not protrude laterally. The supraorbital foramina are small and widely set apart. The braincase is shorter and wide, with parallel lateral sides. The occipital surface is flat, facing posteriorly. The horn cores are laterally compressed and curved. Compared with the molar row the premolar row is shortened. Huabeitragus differs from Macrotragus in its smaller size, strongly bent braincase with the turning point more anterior, narrower braincase, lower and wider occipital surface, rectangular basioccipital without longitudinal groove and weak ridge, smaller foramina ovalia, and less robust, more divergent horn cores, with subtriangular cross section at the base and having keels. Characters shared by Huabeitragus and Macrotragus, are comparable with those of Caprinae. Therefore, we consider these two new genera as members of Caprinae.