Condylarthra presaged the herbivorous groups; but before the close of this period, so favourable were the conditions of life to a rapid evolution of types, that most of the great orders had been clearly defined, though none of the Eocene genera are still extant. Among the early carnivores were Arctocyon, Palaeonictis, Amblyctonus, Hyaenodon, Cynodon, Provivera, Patriofelis. The primitive dog-like forms did not appear until late in the period, in Europe; and true cats did not arrive until later, though they were represented by Eusmilus in the Upper Eocene of France. The primitive ungulates (Condylarths) were generalized forms with five effective toes, exemplified in Phenacodus. The gross Amblypoda, with five-toed stumpy feet (Coryphodon), were prominent in the early Eocene; particularly striking forms were the Dinoceratidae, Dinoceras, with three pairs of horns or protuberances on its massive skull and a pair of huge canine teeth projecting downwards; Tinoceras, Uintatherium, Loxophodon, &c.; these elephantine creatures, whose remains are so abundant in the Eocene deposits of western America, died out before the close of the period. The divergence of the hoofed mammals into the two prominent divisions, the odd-toed and even-toed, began in this period, but the former did not get beyond the three-toed stage. The least differentiated of the odd-toed group were the Lophiodonts: tapirs were foreshadowed by Systemodon and similar forms (Palaeotherium, Paloplotherium); the peccary-like Hyracotherium was a forerunner of the horse, Hyrochinus was a primitive rhinoceros. The evolution of the horse through such forms as Hyracotherium, Pachynolophus, Eohippus, &c., appears to have proceeded along parallel lines in Eurasia and America, but the true horse did not arrive until later. Ancestral deer were represented by Dichobune, Amphitragulus and others, while many small hog-like forms existed (Diplopus, Eohyus, Hyopotamus, Homacodon). The primitive stock of the camel group developed in N. America in late Eocene time and sent branches into S. America and Eurasia. The edentates were very generalized forms at this period (Ganodonta); the rodents (Tillodontia) attained a large size for members of this group, e.g. Tillotherium. The Insectivores had Eocene forerunners, and the Lemuroids—probable ancestors of the apes—were forms of great interest, Anaptomorphus, Microsyops, Heterohyus, Microchaerus, Coenopithecus; even the Cetaceans were well represented by Zeuglodon and others.
| Stages. | Paris Basin. | England. | Belgian Basin. | Mediterranean regions and Great Central sea. | Flysch Phase. | North America. | |
| Bartonien.[1] | Limestone of Saint-Ouen. Sands of Mortefontaine. Sands of Beauchamp. Sands of Auvers. |
Barton beds. Upper Bagshot sands. |
Sands of Lede. | Nummulitic limestones, sandstones and shales. |
Upper part of the Alpine Flysch and Vienna and Carpathian sandstones. Macigno of the Apennines and Maritime Alps. |
Unita Group and Jacksonian. | |
| Lutétien. | Calcaire grossier. | Bracklesham and Bournemouth beds. Lower Bagshot sands. |
Laekenien. Bruxellien. Panisélien. |
Bridger Group and Claibornian. | |||
| Yprésien. | Nummulitic sands of Soissons and Sands of Cuise and Aizy. |
Alum Bay leaf beds. | Sands of Mons en Pévèle. Flanders Clay. |
Wind River Group. Wasatch Group and | |||
| Landé- nien. |
Sparn- acien. |
Plastic Clay and lignite beds. |
London Clay. Oldhaven beds. Woolwich and Reading beds. |
Upper Landénien sands. Sands of Ostricourt. |
Chickasawan. | ||
| Thane- tien. |
Limestones of Rilly and Sézanne. Sands of Rilly and Bracheux. |
Thanet sands. |
Landénien tuffeau. Marls of Gelinden. |
Torrejon Group and Midwayan. Puerco Group. | |||
The non-placental mammals although abundant were taking a secondary place; Didelphys, the primitive opossum, is noteworthy on account of its wide geographical range.
Among the birds, the large flightless forms, Eupterornis, Gastornis, were prominent, and many others were present, such as the ancestral forms of our modern gulls, albatrosses, herons, buzzards, eagles, owls, quails, plovers. Reptiles were poorly represented, with the exception of crocodilians, tortoises, turtles and some large snakes.
The flora of the Eocene period, although full of interest, does not convey the impression of newness that is afforded by the fauna of the period. The reason for this difference is this: the newer flora had been introduced and had developed to a considerable extent in the Cretaceous period, and there is no sharp break between the flora of the earlier and that of the later period; in both we find a mixed assemblage—what we should now regard as tropical palms, growing side by side with mild-temperate trees. Early Eocene plants in N. Europe, oaks, willows, chestnuts (Castanea), laurels, indicate a more temperate climate than existed in Middle Eocene when in the Isle of Wight, Hampshire and the adjacent portions of the continent, palms, figs, cinnamon flourished along with the cactus, magnolia, sequoia, cypress and ferns. The late Eocene flora of Europe was very similar to its descendant in modern Australasia.
See A. de Lapparent, Traité de géologie, vol. iii. (5th ed., 1906), which contains a good general account of the period, with numerous references to original papers. Also R. B. Newton, Systematic List of the Frederick E. Edwards Collection of British Oligocene and Eocene Mollusca in the British Museum (Natural History) (1891), pp. 299-325; G. D. Harris, “A Revision of our Lower Eocenes,” Proc. Geologists’ Assoc. x., 1887–1888; W. B. Clark, “Correlation Papers: Eocene” (1891), U.S. Geol. Survey Bull. No. 83. For more recent literature consult Geological Literature added to the Geological Society’s Library, published annually by the society. (J. A. H.)
EON DE BEAUMONT, Charles Geneviève Louise Auguste
André Timothée d’ (1728–1810), commonly known as the
Chevalier d’Eon, French political adventurer, famous for the
supposed mystery of his sex, was born near Tonnerre in Burgundy,
on the 7th of October 1728. He was the son of an advocate
of good position, and after a distinguished course of study at the
Collège Mazarin he became a doctor of law by special dispensation
before the usual age, and adopted his father’s profession. He
- ↑
Bartonien from Barton, England. Lutétien ” Lutetia = Paris. Yprésien ” Ypres, Flanders. Landénien ” Landen, Belgium. Thanetien ” The Isle of Thanet. Sparnacien ” Sparnacum = Épernay. Laekenien ” Laeken, Belgium. Bruxellien ” Brussels. Panisélien ” Mont Panisel, near Mons. Other names that have been applied to subdivisions of the Eocene not included in the table are Parisien and Suessonien (Soissons); Ludien (Ludes in the Paris basin) and Priabonien (Priabona in the Vicentine Alps); Heersien (Heer near Maastricht) and Wemmelien (Wemmel, Belgium); very many more might be mentioned.
