. Advances in herpetology and evolutionary biology : essays in honor of Ernest E. Williams. Williams, Ernest E. (Ernest Edward); Herpetology; Evolution. 388 Advances in Herpetology and Evolutionary Biology. Figure 10. Suggested area of origin (stippled) and later dispersals (arrows) in primitive anguioids. Map data as in Figure 3. Dashed line indicates possible dispersal of xenosaurs to Central Asia. Dates at end of arrows represent earliest known pre-Pleistocene fossils of the group in that area. See text for further explanation. Atlantic route for glyptosaur entrance into Europe (Fig. 11), r
. Advances in herpetology and evolutionary biology : essays in honor of Ernest E. Williams. Williams, Ernest E. (Ernest Edward); Herpetology; Evolution. 388 Advances in Herpetology and Evolutionary Biology. Figure 10. Suggested area of origin (stippled) and later dispersals (arrows) in primitive anguioids. Map data as in Figure 3. Dashed line indicates possible dispersal of xenosaurs to Central Asia. Dates at end of arrows represent earliest known pre-Pleistocene fossils of the group in that area. See text for further explanation. Atlantic route for glyptosaur entrance into Europe (Fig. 11), rather than the Bering connection. An apparent glypto- saurine from the Eocene of the Canadian Arctic Archipelago (Estes and Hutchin- son, 1980) indicates that dispersal could have been through the North Atlantic connection to Europe, which was main- tained at least until the end of the Early Eocene. In North America the gerrhonotine and diploglossine groups appeared early, the former perhaps as early as the Late Cretaceous, the latter in the Eocene (Gauthier, 1982). Diploglossine em- placement on the West Indies was probably from North America; how and when they reached South America is less easily determined. While gerrhonotines and diploglos- sines appear to have originated in North America, the case of the anguines is less clear. Ophisaurs appear earlier in Europe (Eocene) than in North America (Oligo- cene), suggesting that they were Eura- sian derivatives from an anguioid stock. The fossil record for these times, from both areas, is good enough to allow some confidence in this hypothesis. Several possibilities for origin of anguines exist that can be tested by future work. One is that the predominantly "grass-swim- ming" ophisaurs arose in the early Ceno- zoic in association with the distribution of grassland and savannah environments, finally achieving their present extensive Laurasian distribution. Another possi- bility, which I consider less likely, is that th
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