Early Miocene Assemblages Research Articles

Cenozoic biostratigraphy of larger foraminifera from equatorial carbonate platform of northwestern Brazil

The off-shore Cenozoic succession of the Pará-Maranhão Basin of the Brazilian equatorial margin is studied to investigate skeletal and foraminiferal assemblages during the Oligocene-Miocene interval, one of the fundamental moments in the environmental evolution of our planet. The material from core 1-MAS-16-MA is analyzed using a combination of conventional paleontological analyses, and innovative approaches like micro-CT scan and U/Pb dating on carbonates. The results allowed to clearly constrain the Oligocene – Miocene interval and divide it into four foraminiferal assemblages and seven biofacies useful for both paleoenvironmental reconstructions and stratigraphic correlations. The paleoenvironmental analysis indicates a common pattern of relative sea-level oscillations with the nearby Foz do Amazonas Basin, highlighting a common behavior of this part of the equatorial passive margin during the Oligocene – Miocene interval. The comparison between the succession of skeletal and foraminiferal assemblages of the investigated core and other successions of the Southern and Central American area indicated the presence of stratigraphically relevant foraminiferal assemblages that could be useful for improving the correlation between the various Cenozoic successions of the area (assemblages dominated by nummulitids and lepidocyclinids in the Rupelian; assemblages dominated by Heterostegina (Vlerkina) antillea, lepidocyclinids, and primitive miogypsinids in the Chattian; assemblages dominated by Heterostegina (Vlerkina) antillea, lepidocyclinids, and miogypsinids other than Miogypsinoides and Miogypsinella, in the Aquitanian; assemblages dominated by advanced miogypsinids in the Burdigalian; post Early Miocene assemblages characterized by the lack of abundant lepidocyclinids and miogypsinids). Finally, the overall resilience of most of the large benthic foraminifera taxa to the Oligocene – Miocene transition testifies once more to the adaptability of this group of carbonate producers.

Micromammals from the late early Miocene of Çapak (western Anatolia) herald a time of change

AbstractThe new fossil micromammal assemblage of Çapak represents a mixture of both Anatolian and European faunal elements. The locality is very important for understanding faunal evolution in the less well-known time interval at the end of the early Miocene of western Anatolia. In Çapak, nine species of rodents and one species of ochotonid were encountered: the hamstersDemocricetodon gracilis,Megacricetodon primitivus,Eumyarionaff.E.montanus,Cricetodoncf.C.aliveriensis,Cricetodonsp., andKarydomyscf.K.strati, the mole-ratDebruijniasp., the squirrelAliveria luteyni, the dormouseMyomimus tanjuaen. sp., and the pikaAlbertona balkanica. The assemblage is referable to Anatolian local zone E or MN unit 4. The relative abundance of the various genera is markedly different from that of the older early Miocene assemblages, suggesting that the environment in Anatolia became drier and had a more open landscape.UUID:http://zoobank.org/75f3276c-dcd8-4090-b2f6-d8fc8d3c3f7c

Palaeoecology and distribution of upper Oligocene–lower Miocene foraminifera in the Qom Formation, the Bagher-Abad section, NE Isfahan, Central Iran

These palaeoecological investigations were carried out on foraminiferal assemblages from the Qom Formation in the Bagher-Abad section, northeast of Isfahan, Central Iran. Foraminiferal analysis of the lower limestone part of the succession revealed correlation with the Chattian zone SBZ (Shallow Benthic Zone) 23, and the overlaying marly strata revealed planktonic foraminifera of the Aquitanian Zone M1 (“Paragloborotalia” kugleri Taxon-range Zone). Finally, the topmost, barren zone, and benthic foraminifera assemblage were correlated with the Burdigalian, based on the regional stratigraphic scheme. Palaeoecological interpretations based on microfaunal composition and abundance of benthic foraminifera revealed that late Oligocene microfossils were dominated by larger foraminifera (Rotaliids), whereas early Miocene assemblage was dominated by miliolids. The foraminiferal associations generally reflect well-oxygenated shallow warm tropical waters within the photic zone (<50 m depth) during the Chattian–Burdigalian. These Oligocene/Miocene foraminiferal assemblages indicated middle shelf and inner shelf with normal marine salinity and oligotrophic-to-mesotrophic conditions.

Neogene sharks and rays from the Brazilian 'Blue Amazon'.

The lower Miocene Pirabas Formation in the North of Brazil was deposited under influence of the proto-Amazon River and is characterized by large changes in the ecological niches from the early Miocene onwards. To evaluate these ecological changes, the elasmobranch fauna of the fully marine, carbonate-rich beds was investigated. A diverse fauna with 24 taxa of sharks and rays was identified with the dominant groups being carcharhiniforms and myliobatiforms. This faunal composition is similar to other early Miocene assemblages from the proto-Carribbean bioprovince. However, the Pirabas Formation has unique features compared to the other localities; being the only Neogene fossil fish assemblage described from the Atlantic coast of Tropical Americas. Phosphate oxygen isotope composition of elasmobranch teeth served as proxies for paleotemperatures and paleoecology. The data are compatible with a predominantly tropical marine setting with recognized inshore and offshore habitats with some probable depth preferences (e.g., Aetomylaeus groups). Paleohabitat of taxa particularly found in the Neogene of the Americas (†Carcharhinus ackermannii, †Aetomylaeus cubensis) are estimated to have been principally coastal and shallow waters. Larger variation among the few analyzed modern selachians reflects a larger range for the isotopic composition of recent seawater compared to the early Miocene. This probably links to an increased influence of the Amazon River in the coastal regions during the Holocene.

Late Oligocene-Early Miocene magnetochronology of the mammalian faunas in the Lanzhou Basin-environmental changes in the NE margin of the Tibetan Plateau.

A large number of terrestrial mammalian fossils were reported in the well-exposed Paleogene and Neogene fluvio-lacustrine strata in Western China. Their accurate ages are crucial to understand the mammalian and environmental evolution associated with the step-wise uplift of the Tibetan Plateau. At present their ages are surprisingly poorly constrained. Here, we present a high-resolution magnetostratigraphic dating of the Late Oligocene–Early Miocene mammal assemblages from a 233-m thick fluvio-lacustrine section in the Lanzhou Basin located at the northeastern margin of the Tibetan Plateau, China. The results suggest that the section spans from the polarity subchron C6Cn.2r to C5En, i.e. ranging from ca 23 to 18 Ma. This magnetochronology provides considerably more robust ages for three associated land mammalian faunal assemblages. Updated ages end the debate on existing ambiguous and distinctly different magnetostratigraphic correlations for those Late Oligocene–Early Miocene assemblages. The new ages now enable precise correlation of these faunas to the European Land Mammal and North American Land Mammal Ages. The faunal assemblages further suggest a mixed setting of woodlands and grasslands associated with a humid environment in the Lanzhou Basin during the Late Oligocene–Early Miocene, in contrast to its modern poor vegetation cover and arid environment.

A new assemblage of stem pecoran ruminants from the Oligocene Chitarwata Formation, Bugti Hills, Baluchistan, Pakistan: Paleoenvironmental and paleobiogeographic implications

A new assemblage of stem pecoran ruminants from the Oligocene Chitarwata Formation (lower Bugti Member), Bugti Hills (Pakistan), consists of three identified genera and another indeterminate ruminant. Although limited, the dental and postcranial material is sufficient to identify the genera Amphitragulus and Mosaicomeryx, two common forms known from middle to late Oligocene deposits of Europe, thus reinforcing the ‘middle’ Oligocene age of the lowermost Chitarwata Formation. Mosaicomeryx is reported for the first time from the Indian Subcontinent and this occurrence considerably expands its geographical distribution. A new genus and species, Paalitherium gurki, is erected on the basis of an unusual and unique association of characters on its lower molars. The unclear definition and occurrences of? Gelocus gajensis Pilgrim, 1912 are re-examined in the light of new data from the Bugti and Zinda Pir areas (Pakistan). The new ruminant fauna from Paali is clearly distinctive from the early Miocene assemblage known from Bugti. In accordance with other fossil evidence, the ruminant fauna described here suggests the existence of a tropical forested environment under monsoonal regime with soft food supplies during the time of deposition of the lowermost Chitarwata Formation.

A novel late Early Miocene assemblage of terrestrial gastropods from Santa Cruz (Patagonia, Argentina)

AbstractA remarkable fossil assemblage composed of five gastropod taxa is described from the Early Miocene of Santa Cruz (Patagonia, Argentina) in southernmost South America. The assemblage includes extinct and living genera South America, and on geographic distributions and represent background new information on spatial and across time distributions as well as identification of new taxa. A new taxon,Patagocharopa enigmatican. gen. n. sp., is tentatively assigned to Charopidae.Gastrocopta patagonican. sp. (Vertiginidae) represents the oldest record ofGastrocoptain Argentina and the southernmost record for the Americas.Punctum patagonicumn. sp. (Punctidae) represents the first record ofPunctumfor continental South America, and characterized by a protoconch with traces of axial costulae and a teleoconch with strong radial ribs.Zilchogyra miocenican. sp. is the first Miocene record of the charopid genusZilchogyra. Fragments of a possibleScolodonta(Scolodontidae) are recorded. Overall, the assemblage represents an important and useful paleoenvironmental tool. This fauna suggests that a more temperate and humid environment than today—with a more dense vegetation cover—was prevalent at this site during the Early Miocene.

Temporal Calibration and Biochronology of the Centenario Fauna, Early Miocene of Panama

New excavations along the Panama Canal have yielded a growing Early Miocene assemblage of mammals referred to as the Centenario Fauna. Despite the area’s proximity to South America, the mammals of the Centenario Fauna have entirely North American affinities. The Centenario Fauna is distributed throughout a ∼115-m stratigraphic interval encompassing the uppermost Culebra and Cucaracha Formations within the Panama Canal basin. Previously published ages constrain the age of the lower limit of the Centenario Fauna to no younger than ∼19 Ma, but the upper limit has remained problematical. A fresh exposure of the Cucaracha tuff, a prominent marker horizon within our measured sections, has yielded two new radioisotopic determinations: (1) an 40Ar/39Ar age of 18.96 ± 0.90 Ma and (2) a U-Pb zircon age of 18.81 ± 0.30 Ma. In addition, magnetostratigraphic data indicate that the Centenario Fauna occurs within chron C5Er, from 18.78 to 19.05 Ma on the geomagnetic polarity timescale of Gee and Kent. These correlations further confirm the calibration of the latest Arikareean (Ar4) to early Hemingfordian (He1) transition in Nebraska, at the base of chron C5Er, at about 19.05 Ma. The Centenario Fauna occurs at the beginning of the Hemingfordian North American Land Mammal Age, i.e., He1. A broad faunal province existed during the early Hemingfordian that can be recognized across a north-south range of 5000 km throughout North America, with the southernmost limits defined by the Centenario Fauna of Panama.

Middle Miocene vertebrates from the Amazonian Madre de Dios Subandean Zone, Perú

A new middle Miocene vertebrate fauna from Peruvian Amazonia is described. It yields the marsupials Sipalocyon sp. (Hathliacynidae) and Marmosa (Micoureus) cf. laventica (Didelphidae), as well as an unidentified glyptodontine xenarthran and the rodents Guiomys sp. (Caviidae), Scleromys sp., cf. quadrangulatus-schurmanni-colombianus (Dinomyidae), an unidentified acaremyid, and cf. Microsteiromys sp. (Erethizontidae). Apatite Fission Track provides a detrital age (17.1 +- 2.4 Ma) for the locality, slightly older than its inferred biochronological age (Colloncuran-early Laventan South American Land Mammal Ages: ~15.6e13.0 Ma). Put together, both the mammalian assemblage and lithology of the fossil-bearing level point to a mixture of tropical rainforest environment and more open habitats under a monsoonal-like tropical climate. The fully fluvial origin of the concerned sedimentary sequence suggests that the Amazonian Madre de Dios Subandean Zone was not part of the Pebas mega-wetland System by middle Miocene times. This new assemblage seems to reveal a previously undocumented spatiotemporal transition between the late early Miocene assemblages from high latitudes (Patagonia and Southern Chile) and the late middle Miocene faunas of low latitudes (Colombia, Peru, Venezuela, and ?Brazil).

The Integrated Plant Record vegetation analysis of Early Miocene assemblages from the Most Basin (Czech Republic)

The Integrated Plant Record vegetation analysis of Early Miocene assemblages from the Most Basin (Czech Republic)

New lophiomerycid ruminants from the Oligocene of the Bugti Hills (Balochistan, Pakistan)

ABSTRACT A new assemblage of ruminants from Paali in the lower Chitarwata Formation, Bugti Hills, Balochistan, central Pakistan, includes two lophiomerycids, Lophiomeryx, and Nalameryx gen. nov., allowing revision of ruminants previously reported from the Oligocene of the Indian Subcontinent. Two species are referred to Nalameryx: N. savagei (formerly Iberomeryx savagei), and N. sulaimani nov. sp. The middle Oligocene age previously assigned to the lower unit of the Chitarwata Formation in the Bugti area, mostly based on the rodent fauna from Paali, is supported by the composition of the ruminant fauna, which consists of taxa exclusively known in the Oligocene of Eurasia. The new ruminant fauna from Paali is clearly distinct from the early Miocene assemblages known in the Bugti hills, and suggests the existence of densely forested habitat probably mixed with more open areas in central Pakistan during the middle Oligocene.

THE OLIGOCENE-MIOCENE TRANSITION ON CORAL REEFS IN THE FALCON BASIN (NW VENEZUELA)

The Oligocene–Miocene Transition (OMT) was an interval of regional environmental and biotic change on Caribbean reefs. During the late Oligocene, a diverse Tethyan biota contributed to extensive reef building across the region, but by the early Miocene, reef building had declined, and a regional extinction had removed up to 50% of the late Oligocene diversity. The general decline in reef building in the Caribbean has been attributed to changes in regional water quality. New collections of scleractinian reef corals from four different units in the northwestern Falcon Basin of Venezuela include distinct late Oligocene and early Miocene assemblages. The distribution of fossil coral species and reef limestones suggests that the thick carbonates of the San Luis Formation were deposited during the late Oligocene and that changing water quality during the OMT resulted in the demise of San Luis coral-reef ecosystems. Previous studies have noted an increase in surface-water productivity after the OMT in the region and have suggested oceanographic reorganization as the primary cause; this interval, however, also coincides with a switch in the outlet position of an ancestral Orinoco River. A change in the terrestrial geography of South America might have caused the regional decline in reef building by altering surface-water characteristics, just as modern Orinoco and Amazon outflows exert strong control on shallow-water habitats off the coast of northeastern South America.

Creodonts and carnivores from the Middle Miocene Muruyur Formation at Kipsaraman and Cheparawa, Baringo District, Kenya

The Middle Miocene Muruyur Formation (ca 14.5 Ma), Tugen Hills, Kenya, has yielded a huge creodont and a variety of carnivores ranging in size from mongoose-sized viverrids and herpestids to lion-sized amphicyonids. The fauna partly fills what used to be a major gap in our knowledge of Neogene African carnivores, spanning the period between the better known Early Miocene assemblages of western Kenya and eastern Uganda, and the Late Miocene and Plio–Pleistocene faunas of East Africa. Present in the deposits are Megistotherium, two species of Hecubides, one species of Agnotherium, Herpestes, Vishnuictis, and one or two undetermined felids.

Radiolarian faunal turnover across the Oligocene/Miocene boundary in the equatorial Pacific Ocean

The global warming trend of the latest Oligocene was interrupted by several cooling events associated with Antarctic glaciations. These cooling events affected surface water productivity and plankton assemblages. Well-preserved radiolarians were obtained from upper Oligocene to lower Miocene sediments at Ocean Drilling Program (ODP) Leg 199 Sites 1218 and 1219 in the equatorial Pacific, and 110 radiolarian species were identified. Four episodes of significant radiolarian faunal changes were identified: middle late Oligocene (27.5 to 27.3 Ma), latest Oligocene (24.4 Ma), earliest Miocene (23.3 Ma), and middle early Miocene (21.6 Ma). These four episodes approximately coincide with increases and decreases of biogenic silica accumulation rates and increases in δ 18O values coded as “Oi” and “Mi” events. These data indicate that Antarctic glaciations were associated with change of siliceous sedimentation patterns and faunal changes in the equatorial Pacific. Radiolarian fauna was divided into three assemblages based on variations in radiolarian productivity, species richness and the composition of dominant species: a late Oligocene assemblage (27.6 to 24.4 Ma), a transitional assemblage (24.4 to 23.3 Ma) and an early Miocene assemblage (23.3 to 21.2 Ma). The late Oligocene assemblage is characterized by relatively high productivity, low species richness and four dominant species of Tholospyris anthophora, Stichocorys subligata, Lophocyrtis nomas and Lithelius spp. The transitional assemblage represents relatively low values of productivity and species richness, and consists of three dominant species of T. anthophora, S. subligata and L. nomas. The characteristics of the early Miocene assemblage are relatively low productivity, but high species richness. The two dominant species present in this assemblage are T. anthophora and Cyrtocapsella tetrapera. The most significant faunal turnover of radiolarians is marked at the boundary between the transitional/early Miocene assemblages. We also reviewed changes in other microfossil assemblages in the low latitudes during the late Oligocene through early Miocene. The microfossil assemblages of major groups show sequential changes near the Oligocene/Miocene (O/M) boundary (23.8 Ma). Many extinction events and some first occurrences of calcareous nannofossils and many occurrences of radiolarians are found from about 24.8 to 23.3 Ma, and first occurrences of planktic foraminifers and diatoms followed from 23.2 through 22 Ma. Hence, the O/M boundary is identified as a significant level for microfossil evolutions.

A Miocene algal assemblage dominated by Pediastrum leonensis n. sp. (Chlorophyceae) from Patagonia, Argentina: paleoenvironmental implications

Taxonomic identification of Pediastrum species in an Early Miocene assemblage from southeast Patagonia, Argentina, is used to assess paleoecological conditions. Pediastrum leonensis n. sp. is described based on unique features of the coenobia morphology. It belongs to the P. kawraiskyi–mustersii–patagonicum complex and has no known living counterpart. This group seems to have a long evolutionary history in the region. P. kawraiskyi and P. mustersii are recorded for the first time in pre-Quaternary deposits and their presence suggests a depositional environment represented by a cold stenothermal lake conditions, indicating a temperate to a cold-temperate climate.

A list of fossil cetaceans in Japan

Abstract Fossil cetacea of Japan are abundant and diverse. Despite several summary articles, all the known taxa have not previously been compiled in one place. Here we present a list of the published fossil cetacean records from the Japanese archipelago. The record extends from Middle or Late Oligocene to the Holocene, and includes representatives of both the suborders Odontoceti and Mysticeti. No Eocene Cetacea or Archaeoceti are recorded from Japan. As is typical of the eastern North Pacific and the South Pacific, the Oligocene and Early Miocene assemblages are comprised of archaic and usually extinct families, and the younger assemblages are represented by modern groups comprised of extant genera and families.

Response of deep-sea benthic foraminifera to Miocene paleoclimatic events, DSDP Site 289

Changes in the Miocene deep-sea benthic foraminifera at DSDP Site 289 closely correlate to the climatically induced variations in deep and bottom waters in the Pacific Ocean. In early Miocene time, oxygen and carbon isotopes indicate that bottom waters were relatively warm and poorly oxygenated. Benthic foraminiferal assemblages are characterized by various species inherited from the Oligocene. Expansion of the Antarctic icecap in the early middle Miocene, 14–16 m.y. ago, increased oxygen isotope values, produced cold, more oxygenated bottom waters and lead to a turnover in the benthic foraminifera. An Oligocene—early Miocene assemblage was replaced by a cibicidoid-dominated assemblage. Some species became extinct and benthic faunas became more bathymetrically restricted with the increased stratification of deep waters in the ocean. In mid-Miocene time, Epistominella exigua and E. umbonifera, indicative of young, oxygenated bottom waters, are relatively common at DSDP Site 289. Further glacial expansion 5–9 m.y. ago lowered sealevel, increased oceanic upwelling and associated biological productivity and intensified the oxygen minima. Abundant hispid and costate uvigerines become a dominant faunal element at shallow depths above 2500 m as E. umbonifera becomes common to abundant below 2500 m. By late Miocene time, benthic faunas similar in species composition and proportion to modern faunas on the Ontong-Java plateau, had become established.

Cenozoic radiolarian paleobiogeography: Implications concerning plate tectonics and climatic cycles

A preliminary study of the paleobiogeographic patterns of radiolarian facies during the Paleogene and subsequent time shows that: (1) Through time radiolarian assemblages display distinct faunal provincialism reminiscent of modern faunal distributions correlated with planetary temperature gradients and surface oceanic conditions. The equatorial—tropical radiolarian fauna extended apparently unrestricted across the Pacific Ocean, the Caribbean Sea and the Atlantic Ocean through Early Miocene time. In the Caribbean Sea and the Atlantic Ocean, radiolarians reached their maximum abundance in the Eocene and Oligocene. Subsequently, they gradually declined to virtual disappearance in these areas in the early Miocene. Their Pacific counterparts remained practically undisturbed, except that post early Miocene assemblages there showed a marked trend toward decreasing test thickness. This trend has since been a worldwide characteristic of Neogene radiolarian assemblages and their modern equivalents. It is postulated that the disappearance of radiolarians in the Carribean Sea and the Atlantic Ocean at the end of the Paleogene is related to the onset of the emergence of the isthmus of Panama which interrupted the preexisting oceanic circulation between the Pacific and Atlantic Oceans. (2) Throughout the Paleogene there have been marked sequential fluctuations in the radiolarian assemblages of the Caribbean Sea which indicate intermittent incursions of higher-latitude fauna in this area. Associated with the faunal fluctuations are cyclic variations in the total carbonate of the sediment with patterns also comparable in duration to Pleistocene carbonate cycles in the equatorial Pacific known to have been induced by climatic changes. Based on similarities with Pleistocene climatic cycles in the equatorial Pacific and elsewhere, it is surmised that the faunal and lithologic fluctuations observed in Paleogene radiolarian sediments were also induced by the biologic and physico-chemical processes associated with worldwide changes in the climatic conditions of that time.

Outline of Eastern North Pacific Fossil Cetacean Assemblages

Barnes, Lawrence G. (Section of Vertebrate Paleontology, Natural History Museum of Los Angeles County, Los Angeles, California 90007) 1976. Outline of eastern North Pacific fossil cetacean assemblages. Syst. Zool. 25:321-343.-Geologic formations on the west coast of North America from Baja California, Mexico to central California, U.S.A., provide fossil evidence for a succession of Tertiary cetacean assemblages. Formations representing time periods of stage magnitude from early Miocene to Pleistocene age produce diverse aggregates of Cetacea containing fewer species than can now be found in latitudes corresponding to the Californian Province in the Pacific Ocean. Most fossil assemblages include a sperm whale, several dolphin-like taxa, and 3 or 4 baleen whales, although taxonomy is unstable, and many specimens cannot be assigned to named genera and species. New records of the earliest North Pacific occurrence of the families Balaenidae, Ziphiidae, Monodontidae, Phocoenidae, and Delphinidae (sensu stricto) date from the Miocene, and of the Eschrichtiidae from the Pleistocene. Squalodontidae are notable by their rarity. Early Miocene assemblages are dominated by Eurhinodelphidae, and late Tertiary ones by Stenodelphininae and primitive Balaenopteridae. On the generic level, there is a high degree of endemism among small Odontoceti, and a low degree among Physeteridae and Mysticeti. Collecting biases and deficiencies prevent recognition of antitropical distributions of fossil taxa, and paleoclimatology can not yet be inferred from the fossils. The status of the knowledge of fossil Cetacea in marine sedimentary deposits along the western border of North America is such that a summary and prospectus can now be formulated. A variety of Cenozoic fossil cetaceans are documented in the existing paleontologic literature, but these in no way reflect the real abundance of taxa or of specimens in the field or in museum collections. This article is in part, therefore, a summary of previously unrecorded specimens under study by the author (Barnes, 1972b). Mitchell (1966b) presented an earlier, more popularized overview of marine mammal evolution in the North Pacific Ocean. More fossil species are now represented by skulls and skeletons than previously, and some new interpretations of taxonomy and morphology are forthcoming in more detailed studies. These more complete specimens provide, in some cases, an opportunity for more precise determinations of phylogenetic and taxonomic relationships than was possible in the past for taxa founded upon fragmentary specimens. Kellogg (1923:38) has pointed out that comparisons among many fossil Cetacea have been hampered because of the lack of directly comparable parts of skeletons. Additionally, some taxa are described from skeletal parts having dubious taxonomic value. Cope (1868a, 1868b), Leidy (1851, 1869), and Deraniyagala (1969) have used isolated vertebrae and teeth, and Kellogg (1931) has used isolated periotics. In reality, both convergence and evolutionary conservativism may cause vertebrae and even teeth to be non-diagnostic in cetaceans. Even the isolated periotic has been proven, among Recent Cetacea, to sometimes be only generically and not specifically identifiable (Kasuya, 1973:72). This is particularly true for species of Kogia Gray, 1846 and for Delphinus bairdi Dall, 1873 and Stenella attenuata Gray, 1846 (see Kasuya, 1973:figs. 71-72). Recently, Ginsburg and Janvier (1971); and Hatai, Hayasaka, and Masuda (1963), have used isolated teeth and auditory bullae as holotypes. In light of such recent digressions in the quality of fossil cetacean systematics, I recommend that all subsequent cetacean holotypes include at least skull parts,