The dentitions as well as one complete and several partial skeletons of Equoids from the Eocene lignite beds of the Geiseltal locality are revised. Instead of 13 species distinguished up to now 3 chronoclines with 5 species and 3 separate species are recognized (text. fig. 1). Propalaeotherium hassiacum HAUPT, 1925 is evolving into Propalaeotherium isselanum (CUVIER, 1824) between the levels of the « obere Unterkohle ›› and the « untere Mittelkohle ›› of the Geiseltal section. Propalaeotherium argentonicum GERVAIS, 1849 is shown to be present in the « untere Unterkohle ››, whereas Lophiotherium pygmaeum (DEPERET,1901) occurs in the « obere Mittelkohle ›› and in the « oberes Hauptmittel ››. Plagiolophus cartieri STEHLIN, 1904 appears during the transition from the « Mittelkohle ›› into the « Oberkohle ›› as the earliest true Palaeothere. Therefore the « Oberkohle ›› is already regarded as Upper Eocene. This is corroborated by the occurrence of a phyletic descendant of Propalaeatherium parvulum (Propalaeotherium n.sp.) in the middle and upper "Oberkohle " because this species appears otherwise for the first time at the mammal level of Lissieu. On the other hand Propachynolophus gaudryz (LEMOINE, 1878) described by Matthes (1977) from the « untere Unterkohle ›› turns out te be in fact a Phenacodont. Thus the decisive argument for classifying the « untere Unterkohle ›› as Lower Eocene has to be dropped. Biostratigraphically the « Unterkohle ›› and the «Basishauptrnittel ›› correspond with the lower Middle Eocene (mammal level of Messel), whereas the «unteres Hauptmittel ›› and the « untere Mittelkohle ›› are equivalent to the middle part of the middle Eocene (mammal level of lssel), and the « obere Mittelkohle ›› together with the « oberes Hauptmittel ›› coincide with the upper Middle Eocene (mammal level of Bouxwiller). 

Previous chronological arrangements of South American Quaternary land mammal faunas are appraised on the basis of current geological and paleontological data. Three South American late Pliocene-Pleistocene land mammal ages are conventionally recognized, from oldest to youngest, the Uquian, Ensenadan, and Lujanian ; all are defined on Argentine faunas.

     The Uquian is based fundamentally and historically on the fauna from the Uquía Formation in Jujuy Province, northwestern Argentina. Important known formations in Argentina yielding Uquian Age faunas include the sub-surface Puelche Formation (or Puelchense) near the city of Buenos Aires, and the Barranca de Los Lobos and Vorohué Formations between Mar del Plata and Miramar, Buenos Aires Province. A tentative subdivision is propos-ed for the Uquian into three subages based on knowledge of the Mar del Plata-Miramar sequence, from oldest to youngest, the Barrancalobian, Vorohuean, and Sanandresian. In Argentina the Uquian is presently marked by the first known record of Scelidodon, Hydrochoeropsis, Ctenomys, Canidae, Ursidae, Gomphotheriidae, Equidae, Tapiridae, Camelidae, Cervidae, and the last known record of Thylatheridium, Thylophorops, Dankomys, Eumysops, Pithanotomys, Eucoelophorus, Hegetotheriidae, Sparassocynidae, and Microtragulidae.

The Ensenadan Age is based on the fauna from the Ensenada Formation near the city of Ensenada, Buenos Aires Province. In Argentina the Ensenadan is marked by the first known record of Lomaphorus, Neothoracophorus, Plaxhaplous, Cavia, Lyncodon, Lutra, Galera, Smilodon, Dicotyles, Lama, Vicugna, the last known record of Orthomyctera, and the only known record of Brachynasua.

     Typícal beds of late Lujanian Age in Argentina consist of fluvial deposits occupying stream channels, and shallow basins, often incised into beds of early Lujanian (i.e. Bonaerian of early workers) and Ensenadan Age. The Lujanian Age is based on a fauna from beds along the Rio Luján, about 65 km west of the city of Buenos Aires, Buenos Aires Province. The Lujanian in Argentina is marked by the first record of Equus, Chlamyphorus, and Holochilus, and the last record of Megatherioidea, Glyptodontoidea, Arctodus (=Arctotherium), Smilodon, Litopterna, Notoungulata, Proboscidea, Equidae, Morenelaphus, and Palaeolama.

   These land mammal ages are often difficult to recognize in other South American countries. The compositions of South American Pleistocene faunas vary with the environment. Some taxa were widely distributed in fossil deposits throughout the continent, but their occurrences need not reflect synchroneity. This is a result of changing climates and habitats in time. Consequently, proposed intracontinental correlations need confirmation based on magnetostratigraphy and a radioisotope time scale. Paleontologic characterizations of these land mammal ages (i.e. first and last record, and guide fossils) are useful for much of Argentina, but extensions to most of the other parts of South America are at best tenuous.

The majority of known non-Argentine Pleistocene faunas are believed to be Lujanian in age. Possible non Argentine early Pleistocene (Uquian) faunas include Ayo Ayo and Anzaldo in Bolivia, and Cocha Verde in southern Columbia. A possible middle Pleistocene (Ensenadan or early Lujanian) fauna is the Chichense of Ecuador. Paleomagnetic and radioisotopic date (MacFadden et al., 1983) clearly indicate that the greater part of the Tarija fauna (Bolivia) is Ensenadan in age.

  The end of the Pleistocene and beginning of the Holocene in South America is marked by extinction of nearly all large mammalian herbivores and their specialized large predators. Radiocarbon age determinations suggest that large scale extinctions of megafauna occurred between 15,000 and 8,000 yrs. B.P. (years before present). 

The principles and practices employed in establishment and recognition of South American land mammal ages are reviewed along with previous and present concepts of distinguishing time, rock, and faunal units. Previous chronological arrangements of South American Tertiary land mammal faunas are appraised on the basis of recent geological and paleontological data. Twelve South American Tertiary land mammal ages are here recognized [from oldest to youngest, Riochican (middle to late Paleocene); Casamayoran (early Eocene); Mustersan (middle Eocene); Divisaderan (late Eocene); Deseadan (early [to middle?] Oligocene); Colhuehuapian (late Oligocene); Santacrucian (early Miocene); Friasan (middle Miocene); Chasicoan (late Miocene); Huayquerian (latest Miocene); Montehermosan (early to middle Pliocene); and Chapadmalalan (late Pliocene)]. As all except the Friasian were originally defined on the basis of Argentine faunas, these are discussed first and at length, and each is reviewed with discussion of type locality, stratigraphy, type fauna, and faunal correlations. Non-Argentine faunas are then discussed country by country in alphabetical order.

     A review is given of radioisotope dates obtained on volcanic rocks (i.e., basalts, tuffs) associated with mammalbearing beds in Argentina. Based on these age determinations and on correlation of the late Tertiary land mammals involved in the interchange between North and South America, a chronology of South American land mammal ages correlated with North American land mammal ages and European marine stages is proposed.

It is concluded that South America was an island continent through most of the Tertiary Period (ca 65 to about 3 Ma). As a result, the land mammal fauna of South America developed in isolation and was dominated by autochthonous endemic groups. Toward the end of the Tertiary (i.e., middle Miocene) a unique faunal balance had been achieved by the descendants of the ancient inhabitants (notoungulates, litopterns, condylarths, astrapotheres, edentates, marsupials) and of later (late Eocene) waif immigrants (caviomorph rodents, platyrrhine primates). A prominent feature of this mammal fauna was the combination of carnivorous and omnivorous marsupials with native placental herbivorous ungulates, subungulates, and edentates.

Sometime during the late Miocene, a limited but important interchange of mammalian taxa between North and South America took place. Procyonids (raccoons and their allies), a group of North American origin, first appear in South America in strata of Huayquerian Age, while members of the extinct South American ground sloth families Megalonychidae and Mylodontidae first appear in North America in early Hemphillian time. These groups dispersed along island arcs before the appearance of the Panamanian land bridge in the Pliocene (ca 3.0 Ma). Cricetine rodents, a group of North American origin, are first known in South America in strata of Montehermosan Age. The known taxa are too advanced and diversified to be considered the first of this group to invade South America. lt is believed by some workers that these rodents arrived before the Montehermosan, possibly in the late Miocene or earlier, by waif dispersal from North America.

The isolation of South America ended with the appearance of the Panamanian land bridge, which provided a direct, dry land connection between the two Americas. Across this portal an extensive interchange of terrestrial faunas occurred, and the fossil record documents an intermingling of these long-separated land mammals faunas.

      The beginning of this interchange by land route in South America is marked by the appearance of mammals which evolved from North American emigrants in the Chapadmalal Formation of Argentina. These include a mustelid (Conepatus), a tayassuid (Argyrohyus), and four genera (Akodon, Dankomys, Graomys, Reithrodon) of cricetine rodents. The appearance of this contingent of northern animals favors the existence of the Panamanian land bridge by this time. Likewise, a large number of terrestrial vertebrates of South American origin appear in North America in beds of late Blancan Age date around 2.7 Ma. Among the mammals are Neochoerus, Erethizon, Glyptotherium, Glossotherium, Kraglievichia, and Dasypus. 

The mammalian faunas of the Paleogene of Europe and their localities are reviewed with comments on problems of European stratigraphy (epoch, stage and substage limits) and on the possibilities of faunal migrations. Radiometric dating is discussed. A stratigraphic scale for the Paleogene is presented, as well as a refined system of sequential faunal levels. 

The Pantolestidae from the middle eocene of Bouxwiller are the subject of a detailed study. Buxolestes hammeli (n. g., n. sp.) is not closely related to any other European or North American form described until now; it presents, however, some characters in common with Pantolestes, a form of the same age from North America. A parallel evolution from a common ancestral form could explain this ressemblance.
Another form (gen. and sp. indet.) accompanies Buxolertes hammeli in the Bouxwiller fauna.
  

Designated the type-locality of a late Eocene paleomammal zone, Robiac has recently been the object of important excavations. The first results of the new collecting, as  well as a revision of the material in old collections, are given in this work.
Two stratigraphic section, cutting through the two sites presently distinguished (Robiac-Nord and Robiac-Sud) reveal the lithologic variation at the base of the Fons Limestone and the localization of three fossiliferous beds at Robiac-Sud.
The molluscan fauna and the flora (charophytes), which have already been described, as well as that of the lower vertebrates, have been listed.
A list of 46 mammalian species (only 16 species were known previous to 1964) has been established. The micro-mammals, nearly all new in this fauna (marsupials, insectivores, bats, rodents, primates, and some smallsized artiodactyls), Were obtained only after screen-washing of the matrix; about 4 tons of sediment were thus treated.
The artiodactyls have been the most extensively analyzed; 6 genera, of which one is new, have been recognized. The latter is described as Robiacina minum n.g., n.sp., and represents a very small artiodactyl of the family Anoplotheriidae. The taxonomie status of certain species formerly described has been clarified by the designation of lectotypes (Cebochoerus robiucensis, Catodonerium robiacense, Xiphodon castrense).
The paleontologic corrélations at present possible between the late Eocene faunas have allowed the relative positions of te different French localities of this age to be established; the Guépelle locality, it seems, could define in the future a new paleomammal zone.
  

A late Pleistocene deposit of 60 species of vertebrates and 12 of invertebrates is described from Robinson Cave, Overton County, Tennessee, U.S.A. Forty-eight species of mammals are represented by at least 2,483 individuals; 10 % are extinct, 10 % occur in the state only as boreal relicts in the Great Smoky Mountains; 23 % no longer occur as far south as Tennessee; 57 % occur at or near the site today. Nínety-one percent of the Recent mammal species can be found living today in the Minnesota-Wisconsin area, approximately 10 degrees farther north. Fluorine analysis suggests a long period of accumulation. The following 10 mammalian species are recorded from Tennessee for the first time. Sorex arcticus, Microsorex hoyi, Citellus tridecemlineatus, Clethrionomys gapperi, Microtus pennsylvanicus, Synaptomys cooperi, Synaptomys borealis, Zapus nudsonius, Napaeozapus insignis, Martes americana. Six additional species are present as boreal relicts in the Great Smoky Mountains of eastern Tennessee but not at the site today : Sorex cinereus, Sorex dispar, Sorex palustris, Parascalops breweri, Glaucomys sabrinus, Mustela nivalis. Six forms are extinct: Canis dirus, Ursus americanus amplidens, Sangamona furtiva, Dasypus bellus, Mammut americanus,Megalonyx jeffersoni. Twenty-six additional species of mammals, all of the snails, birds, reptiles, and amphibians recovered from the fauna still inhabit the area today: The fauna is indicative of a cold-temperate climatic episode associated with the Wisconsin glaciation, but may be chronologically mixed.