The Middle Eocene Fossillägerstätte of the Geiseltal lignite beds near Halle/S. (German Democratic Republic) is the reference locality of the European land mammal age Geiseltalian and of the Mammalian Paleogene reference levels MP 11 - MP 13. Due to this importance a reinvestigation is given of the lithostratigraphical development of the Geiseltal beds and of their vertebrate sites. The last are genetically related to the southwest border of the Geiseltal depression and the influx of carbonate-rich waters. The geographical distribution and stratigraphical position of the fossiliferous sites depends on subrosive and tectonically controlled distribution of coal seams. The geological factors and the known stratigraphical guide of some mammalian species suggest corrections of the age of some sites. Four of the alltogether five coal bearing phases contain the 35 sites with mammalian remains. By the distribution of the around 69 mammal species are characterized, with 5 faunal steps ranging from MP 11 to MP 14 or over the Geiseltalian up to the Lower Robiacian. Well distant are the faunas of MP 11 and MP 12. Beginning with MP 12 up to MP 13/14, the fossil record is very frequent by 27 sites. This evidence coincides somewhat more with the concept of land mammal ages compared to that of the punctual mammalian reference levels. 

New and hitherto unpublished mammals from the stratigraphical levels Unterkohle, Untere Mittelkohle and Obere Mittelkohle of the Geiseltal near Halle, GDR, are described (= biochronological levels MP 11-13, Geiseltalian sensu Franzen & Haubold 1986a, b). The marsupial taxa Amphiperatherium aff. maximum (MP 12), A. goethei (MP 12), and Peratherium aff. monspeliense (MP 12 and 13) are recorded for the first time. A lectotype for Amphiperatherium giselense is designated, and the alleged primate Microtarsioides voigzi is assigned to Marsupialia, incertae sedis. A new insectivore species, Saturninia ceciliensis n. sp., is described (MP 13). The anteater Eurotamandua joresi is recorded for the first time outside its type locality, Grube Messel, FRG (MP 11). The present humerus and ulna display the autapomorphic features of the myrmecophagids. 

In the course of the current revision of adapid primates from the Eocene Geiseltal, an almost complete specimen was found in the Geiseltal Museum collections. The fossil, the most complete adapid specimen so far discovered in Europe, has been determined as Pronycticebus neglectus n. sp.
Ecology and locomotion as well as the likely phylogenetic position within the infraorder Adapiformes are discussed. 

The present study of Artiodactyla from the Middle Eocene of the Geiseltal lignite beds concems systematics, biostratigraphy, and palaeoecology on the basis of 174 specimens: isolated remains to more complete skeletons. Instead of the formerly known five species of two families are now recognized 14 species of the Diacodexeidae, Dichobunidae, Cebochoeridae, and Haplobunodontidae. New species are Aumelasia maniai, Anthracobunodon neumarkensis, Masillabune franzeni. Four species of the Geiseltalfauna are definitely known from elswere, and five species are closely related to those from other European localities. Evidently the faunal situation of artiodactyls during the Middle Eocene of Europe was largely uniform. The distribution of artiodactyls within the sequence of the Geiseltal strata corroborates the biostratigraphical concept of the land mammal age Geiseltalian (Franzen & Haubold l986b) as well as the mammalian reference levels MP 11-13 (Franzen 1987). Reconstructions of the skulls and skeletons allow conclusions on the functional morphology and palaeoecology of the artiodactyls of the European Middle Eocene 

Palaeotis weigelti, from the Middle Eocene of central Europe, is a flightless, paleognathous bird. It appears to be a member of the ostrich lineage on the basis of trivial derived characters. It is a very primitive ratite, however, and does not possess any of the highly specialized cursorial adaptations that characterize the modern steppe -and savanna- dwelling ostriches. 

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). 

In the course of a revision of the Equoidea numerous dentitions as well as a partial skeleton of a Phenaeodont were discovered from the Middle Eocene lignite beds of the Geiseltal locality. These fossils are recognized as a new genus and species of Phenacodontidae : HaIlensia matthesi n.g. n.sp.. The species is present in the « untere und obere Unterkohle ›› (uUK, oUK = the lower and upper part of the Lower Coal Seam) as well as in the « obere Mittelkohle ›› (oMK = the upper part of the Middle Coal Seam). Two fragmentary upper jaws described and figured by Matthes (1977) as Propachynolophus gaudryi are also belonging to Hallensia matthesi. Thus the decisive argument for classifying the " Unterkohle " of the Geiseltal section as Lower Eocene has to be dropped. Another relict form of the Geiseltal is Esthonyx tardus n. sp. documented by a fragmentary mandible coming from the « untere Unterkohle ››. This is the latest Tillodont from Europe. Contrasting to E. munieri from the european Lower Eocene the dentition of E. tardus is morphologically more progressive.