The Rise of the First Land Plants

Accelerated evolution of early angiosperms: Evidence from ranunculalean phylogeny by integrating living and fossil data

“…Accelerated angiosperm evolution has also been observed for particular clades such as the rosids, which might have diversified rapidly in perhaps as little as in 4–5 Myr (Wang et al, ), and the Saxifragales, which diversified rapidly in as little as 6 Myr (Jian et al, ). Chaloner () showed that the occurrence of spores preceded the finding of abundant megafossils of early land plants by at least 10–15 Myr. This suggests that spores and pollens might be found long before abundant angiosperm megafossils or mesofossils, and were common in sediments such as the Barremian, Aptian, and Albian angiosperm explosive diversity.…”

Pertica, a New Genus of Devonian Plants from Northern Maine

“…This is due to the efforts of several workers from various laboratories who have provided new and significant data. Third, changes in age determinations of certain floras have resulted in a more accurate understanding of the proper sequence of events: the Baragwanathia flora of Australia, now considered Siegenian (Jaeger, 1967), and the Rhynie Chert flora, possibly at the Siegenian-Emsian boundary (Chaloner, 1970 Pavlides et al, 1964; dates are in millions of years from the present (Harland et al, 1964) Dorf and Rankin (1962) in the northern part of Baxter State Park. Second, new plants have been discovered whose gross morphology, reproductive structures, and sometimes even internal anatomy have been described: Crenaticaulis (Banks and Davis, 1969); Kaulangiophyton (Gensel et al, 1969); Krithodeophyton and Steganotheca (Edwards, 1968(Edwards, , 1970.…”

Evolutionary Biology

“…Comparing the trends of spore-pollen evolution in the preangiosperms and the angiosperms, it is evident that the trend of morphological evolution, as reflected in the occurrence of the trimorphous condition of pollen grains in the preangiosperms suddenly changed in the angiosperms (see also Chaloner, 1970;Muller, 1970), in which new apertural forms represented by the tricolpate group appeared. The distribution of the two pollen apertural groups, the monocolpate and the tricolpate, in the angiosperms is suggestive of their phylogeny and evolutionary trends.…”

“…This scarcity and the general scarcity of reported fossil thallophytes appear to be a prime result of the emphasis on megascopic organisms traditional to paleobiology; although fossil prokaryotes, fungi, and unmineralized algae are no doubt of rather widespread occurrence, they commonly have been overlooked or ignored in studies chiefly concerned with remains of tracheophytes and metazoans. Recent increased interest in the phylogeny of thallophytes (Sagan, 1967;Klein and Cronquist, 1967;Whittaker, 1969;Raven, 1970) and in the origin of the vascular flora (Banks, 1968;Chaloner, 1970) should spur the search for new fossil evidence of lower plants. To date, it is only in deposits of Precambrian age, essentially devoid of traces of higher organisms, that bluegreen algae have received detailed attention (Schopf, 1968(Schopf, , 1970a, and there only a bare beginning has been made.…”

“…The angiosperms are the latest evolved group in the evolutionary hierarchy of the plant kingdom; all other plant groups that preceded it constitute the "preangiosperms," at some level of the evolution of which the origin and organization of the unique angiosperm morphostructure occurred (Puri, 1967;Axelrod, 1970;Chaloner, 1970;Muller, 1970;Nair, 1970a;Schopf, 1970;Schuster, 1972;Meeuse, 1972). Morphologists and phylogenetic taxonomists reckon the preangiosperms as being composed of the Thallophyta, Bryophyta, Pteridophyta, and Gymnospermae in the order of phylogenetic succession, but the origin and early evolution of each group are shrouded in mystery.…”