Deciduous Dentitions of Eocene Cebochoerid Artiodactyls and Cetartiodactyl Relationships

Deciduous lower premolars (milk teeth) of the Eocene artiodactyl family Cebochoeridae possess accessory denticles and are remarkably similar to both deciduous and adult teeth of the cetacean family Basilosauridae, suggesting that morphological characters of juvenile dentitions are important to understanding the phylogenetic origin of whales and morphological transitions in the cetartiodactyl lineage. Incorporation of these new characters into a larger phylogenetic analysis of morphological characters of artiodactyls, mesonychids, and basal and recent whales supports a monophyletic Cetartiodactyla, but does not directly support a whale–hippo relationship. However, the presence of accessory denticles on some artiodactyl dentitions weakens the morphological support for a monophyletic Artiodactyla, suggesting either that whales and cebochoerids may be more closely related than had been thought, or that cebochoerids share a developmental pathway with cetaceans.     

内蒙古苏崩地点的古新世软食中兽(哺乳纲,中兽目):古新世-始新世界线附近“东方伊甸园”扩散模式的新证据(英文)

记述了发现于内蒙古苏崩晚古新世格沙头期的中兽类软食中兽Hapalodectes属的一个新种。这是软食中兽在中国古新世地层中的首次发现,也是亚洲格沙头期的第二种软食中兽。已有的系统学和生物地层学证据支持软食中兽属和软食中兽科(Hapalodectidae)亚洲起源的观点。软食中兽显然是在古新世-始新世极热事件(PETM)期间通过白令陆桥扩散到北美大陆的,因而符合"东方伊甸园"学说中的生物地理格局。软食中兽有限的(即非欧洲的)地理分布使得我们可以重建该属生物地理学历史。如同软食中兽一样的"东方伊甸园"式的扩散模式,可以看作是大的环境变化事件导致多个支系产生相似的系统学和生物地理学分布格局的生物地理扩散机制。严格地检查了所谓的在古新世-始新世界线上或其附近的与"东方伊甸园"模式相矛盾的大陆间哺乳动物扩散事例,结果发现这些例子都是不可靠的。"东方伊甸园"生物地理学说充分解释了PETM时期哺乳动物群更替以及劳亚古陆哺乳动物地理分布格局的成因。     

Phylogenetic aspects of Cetacean origins: A morphological perspective

The evolutionary steps leading up to the origin of cetaceans involved pervasive changes in the masticatory apparatus, the ear, and limb morphology. These changes bear heavily on the phylogenetic relationships of Cetacea, and are investigated here on the basis of two of its earliest members:Pakicetus andAmbulocetus. A phylogenetic analysis of cetaceans, five groups of mesonychians, and five other groups of ungulates indicates thatPakicetus is the sister group to all other cetaceans, and that Cete (mesonychians and Cetacea) is a monophyletic group.