论文部分内容阅读
记述了一件与下颌咬合在一起的完整的祖熊头骨化石。化石发现于甘肃临夏州广河县槐沟村柳树组地层中上部,其层位与时代为新近纪灞河阶/期的晚期,距今约8 Ma。对比研究表明,该头骨与目前所有已知熊类祖先类型都不同,应为一新种,定名为Ursavus tedfordi(戴氏祖熊)。采用TNT软件包对11种祖先熊类和37个特征组成的数据进行不同条件(non-additive,additive等)下全搜索(Implicit Enumeration),并采用自引导法(bootstrapping)进行可信度评价。我们从基于部分特征加积(partially additive)条件下所得出8个最简约树中选取树5作为最可信简约树。该树表明,熊科从渐新世-早中新世的豺熊类(hemicyonids)分出后产生了两类基干类型,Ballusia elmensis和B.orientalis。后者稍更进步,可能为一特异支。此后产生了两大次支:一支向印度熊(可能还有郊熊)+大熊猫演化;另一支则由中-晚中新世的祖熊(Ursavus)和此后由某类祖熊所产生的现生熊类(不包括大熊猫)组成。从现有的化石判断,新建戴氏祖熊是与现生熊类在形态上最为接近的祖先类型,但戴氏祖熊具有某些自近裔性状,可能为一早期旁支。
Describes a complete ancestral Zombie skull fossilized with the jaw. The fossils were found in the middle and upper part of the Willow Formation in Huaiogou Village, Guanghe County, Linxia, Gansu. The strata and age of these fossils are late Pleistocene 灞 阶 / /, dating about 8 Ma ago. The comparative study shows that the skull is different from all known ancestors of the known bear species and should be a new species named Ursavus tedfordi. The data of eleven ancestral bears and 37 traits were subjected to the full search under different conditions (non-additive, additive, etc.) using the TNT software package. The trustworthiness was evaluated by bootstrapping. We select tree 5 from the eight most parsimonious trees based on partial additive conditions as the most plausible minimal tree. The tree shows that the two families of stem types, Ballusia elmensis and B. orientalis, have been developed from the families of the Beaux-Arts from the late Oligocene-Early Miocene hemicyonids. The latter slightly improved, may be a specific branch. Two major sub-divisions were then created: one that evolved to the Indian (and possibly suburban) bears + the giant panda; the other from the Ursavus of the Middle-Neoproterozoic (Ursavus) Emergence of existing bear species (excluding giant panda) composition. Judging from the existing fossils, the newly formed Dendrocalamus andeanis is the morphologically closest ancestor type to the existing species of bears, but the Dendrite Anomala has some self-descent traits and may be an early shunt.