Species - Species-species transitions known from other...

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Species-species transitions known from other misc. mammal groups Bookstein et al. (1975) describef gradual shifts in mean size in early Eocene mammals (cited in Gingerich, 1985). Gingerich (1980) documented gradual change in a lineage of early Eocene tillodonts: Esthonyx xenicus to E. oncylion to E. grangeri . Hulbert and Morgan (in Martin, 1993) describe gradual evolution through 2.3 million years in a genus of giant armadillo in Florida, Holmesina , with a noticeable spurt of evolution at 1.1 Ma when H. septentrionalis changed to H. floridanus . This concludes our tour of the Cenozoic placental mammal record! However, please do not unfasten your seatbelts until the FAQ has come to a complete stop. A quote from Gingerich (1985) about Eocene mammals also applies to the mammal record as a whole: "The fossil record of early Eocene mammals appears to be both gradual and punctuated. It is gradual in the sense that early and late representatives of all species, whether changing or not, are connected by intermediate forms. Some ancestor-descendant pairs of species are also connected by intermediates. The record is punctuated in the sense that new lineages appear abruptly at the Clarkforkian-Wasatchian boundary, and some possible ancestor-descendant pairs of species are not connected by intermediates." In summary, as Carroll (1988) said, "There is considerable evidence from Tertiary mammals that significant change does occur during the duration of species, as they are typically recognized, and this change can account for the emergence of new species and genera." Conclusion: What does the vertebrate fossil record show?
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Species - Species-species transitions known from other...

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