General aspects of the evolutionary history of whales and dolphins

Abstract The Cetacea are the most diverse and highly aquatically adapted group of mammals. Their fossil record extends back at least to the Middle Eocene ( ca 50 Ma), and they will possibly be found earlier, judging by the relatively highly evolved nature of the earliest known whales. The most likely terrestrial ancestors of whales are the mesonychids, primitive hoofed mammals with omnivorous diets. Recently discovered archaeocetes with large, mesonychid-like heads and dentitions and functional hind limbs reconfirm earlier ideas about the mesonychid origin of cetaceans and the amphibious nature of the earliest transitional forms. Fossil cetaceans are relatively abundant and diverse thoughout the world, and are now known from every continent, including Antarctica. Odontocetes evolved echolocation to locate food. Mysticetes developed bulk feeding adaptations. Both undoubtedly evolved from archaeocetes, and the monophyly of Cetacea is the most parsimonious present hypothesis. Chromosomal and molecular evidence has taken an increasingly important role in determining cetacean relationships, but fossils and classical comparative morphological studies remain a necessary and pivotal source of information about cetacean phylogeny.     

Classification and distribution of Oligocene Aetiocetidae (Mammalia; Cetacea; Mysticeti) from western North America and Japan

Abstract Fossil whales in the very rare, primitive, extinct cetacean family Aetiocetidae are small, relict, toothed mysticetes that persisted into Late Oligocene time after more highly derived baleen-bearing mysticetes had already evolved. No known aetiocetid could be ancestral to baleen-bearing mysticetes, but aetiocetid morphology is in many ways intermediate between archaeocetes and baleen-bearing mysticetes, demonstrating the probable transitional steps passed through in the evolution of baleen-bearing mysticetes. Their discovery indicates that mysticetes evolved from Archaeocetes, and supports theories of the monophyly of Cetacea. Late Oligocene aetiocetids have been found on both sides of the North Pacific Ocean: on Vancouver Island, British Columbia, Canada; in Oregon and Washington, USA; in Baja California Sur, México; and the islands of Kyushu and Hokkaido, Japan. The most primitive North American aetiocetid, Chonecetus sookensis Russell, 1968, is from the early Late Oligocene Hesquiat Formation on Vancouver Island, British Columbia, Canada. A more derived, Late Oligocene species, Chonecetus goedertorum Barnes and Furusawa, new species, from the Late Oligocene Pysht Formation, Olympic Peninsula, Washington, has the primitive placental mammalian tooth count of 11/11. The type genus of the family, Aetiocetus Emlong, 1966, has as its type species, A. cotylalveus Emlong, 1966, known only from the Late Oligocene Yaquina Formation on the coast of Oregon. It has 11 upper teeth on each side of the rostrum. A more derived species, Aetiocetus weltoni Barnes and Kimura, new species, from a higher stratigraphic level in the Yaquina Formation, has a more posteriorly positioned cranial vertex and a tooth count of 11/12. We describe four new species of aetiocetids in three genera from the Late Oligocene Morawan Formation near Ashoro, Hokkaido, Japan. The most primitive, Ashorocetus eguchii Barnes and Kimura, new genus and species, has a primitive stage of cranial telescoping, and is closely related to Chonecetus Russell, 1968. Another, Morawanocetus yabukii Kimura and Barnes, new genus and species, in some ways intermediate between Chonecetus and Aetiocetus, has a suite of unique derived characters, including a much foreshortened brain case. The third, Aetiocetus tomitai Kimura and Barnes, new species, is the most primitive species of Aetiocetus yet discovered. The fourth, Aetiocetus polydentatus Sawamura, new species, the most derived species of Aetiocetus known, has a highly telescoped cranium, homodonty, polydonty and a dental count of 13–14/14–15. The fossil record now indicates considerable diversity in the family, with several different contemporaneous lineages in three new subfamilies: Chonecetinae, Morawanocetinae and Aetiocetinae. Aetiocetids are not known outside the North Pacific. Many Recent mysticetes are essentially cosmopolitan, and aetiocetids might have also been relatively widely dispersed. We suspect that with time their remains will be found around other ocean basins also. If so, then they may be potentially useful in trans-oceanic geological correlations.     

Description of a new toothed mysticete from the Late Oligocene of San Juan de La Costa,B.C.S., México

This paper describes a toothed mysticete that belongs to a basal family found in Oligocene sedimentary rocks deposited in the North Pacific Ocean. The material that is described here belongs in the Chattian stage of the Oligocene, and it was collected near Arroyo El Saladito from the San Juan Member in the El Cien Formation, Baja California Sur, México. The sedimentary environment of this area has been interpreted to be a continental platform with nutrient-rich waters combined with anoxic conditions. Therefore, the specimens that have been found in the phosphorite layers lived in an environment of shallow coastal waters. The material described is a dentary fragment, a skull and fragments of the teeth. The new taxon is located within the Superfamily Aetiocetoidea due to the presence of functional teeth, which have a slightly globose shape with eight slightly triangular apices. Niparajacetus palmadentis presents a morphology that contrasts with other toothed whales. For example, it shows an elongated and wide skull in the posterior region with a triangular shape, and its estimated total length is 3.2–3.5 m.     

Scutocyamus antipodensis n.sp. (Amphipoda: Cyamidae) on Hector's dolphin (Cephalorhynchus hectori) from New Zealand

The whale‐louse Scutocyamus antipodensis n.sp., ectoparasitic on Hector's dolphin, Cephalorhynchus hectori (van Beneden), is described and figured from material collected in Cloudy Bay, Cook Strait, New Zealand. Morphologically the new species is very close to S. parvus Lincoln & Hurley, the type and only other species of the genus, known only from the North Sea. However, the two species differ in the detailed structure and spinosity of the body and pereopods.     

鲸类线粒体基因组特征分析及分子标记探讨

综合分析鲸类32个物种的线粒体基因组全序列,全面揭示了鲸类线粒体基因组的基本特征、蛋白质编码基因、选择压力和差异位点等.鲸类线粒体基因组均编码后生动物标准的37个基因.绝大多数鲸类线粒体基因组的基因排列顺序完全相同,而且与脊椎动物线粒体基因组的典型排列一致.4个类群(真露脊鲸属、须鲸属、原海豚属和宽吻海豚属)线粒体基因...     

A new type of primitive baleen whale (Cetacea; Mysticeti) from Kyushu, Japan

Abstract An important and relatively complete fossil mysticete cetacean specimen was collected from the Oligocene age Ashiya Group in Kyushu, Japan. The specimen includes a complete skull, with the anterior part of the vertebral column, several ribs, and the left pectoral limb. It provides significant information about the early evolution of cetotheres and transitional steps from the Archaeoceti to Mysticeti. Several features of the specimen, such as the anterior position of the nasal opening and large mandibular foramen, are primitive, but others are derived, such as the wide maxilla, broad supraorbital process of the frontal, occipital shield overhanging the temporal fossae, and the flat articulation of the distal end of the humerus. This animal, therefore, has a mixture of primitive and derived characters. It represents a stage of evolution in mysticetes that has been previously unrecognized.