. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 452 Bulletin Museum of Comparative Zoology, Vol. 149, No. 7. Figure 27. The world in Eocene time showing the distribution of the hystricognath groups and the Paramyidae, and the evolutionary relationships of hystricognath groups according to Lavocat (dashed lines) and according to us (solid lines). B—Bathyergoidea; C—Caviomorpha; F—Franimorpha; H—Hystricidae; P—Paramyidae; T—Thryonomyoidea; w— waif transport. Intercontinental migrations not marked w are assumed to have been via dry land. In our view bathyergids and hy
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 452 Bulletin Museum of Comparative Zoology, Vol. 149, No. 7. Figure 27. The world in Eocene time showing the distribution of the hystricognath groups and the Paramyidae, and the evolutionary relationships of hystricognath groups according to Lavocat (dashed lines) and according to us (solid lines). B—Bathyergoidea; C—Caviomorpha; F—Franimorpha; H—Hystricidae; P—Paramyidae; T—Thryonomyoidea; w— waif transport. Intercontinental migrations not marked w are assumed to have been via dry land. In our view bathyergids and hystricids reached Africa in early and late Miocene time, respectively. Europe and Asia were sufficiently dis- tinct to show that the Turgai Strait was a real barrier to interchange, whereas there were many similarities between the fau- nas of North America and northern Asia (Dawson, 1977). Discoveries in the early Eocene ot China of such typically Wasatchian mam- mals as Homogalax and Heptodon, un- known in Europe (Chow and Li, 1965), and of a paramyid in the size range of small species oi Microparamys (Li et ah, 1979) strongly indicate that a connection between Asia and North America was in existence at that time. Confirmatory evi- dence is provided by recent finds of mammals referable to or allied with North American genera in the early Eocene Naran Bulak Fonnation, Mon- golian People's Republic (Dashzeveg and McKenna, 1977, and references there cited). These authors point out that the presence in the Naran Bulak oi Altonius, an omomyid of North American anapto- mori^hine affinities, indicates a climate in the Bering Strait region sufficiently clem- ent to support very small primates. The Eocene, especially its earlier stages, does seem to have been a rather wami epoch. As an aside (by ), categorical state- ments that marsupials were absent in Asia may prove to have been premature. Didelphids reached Europe, via the North Atlantic early Eocene connection, and
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