Cuticular Anatomy of Angiosperm Leaves from the Lower Cretaceous Potomac Group I. Zone I Leaves
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Angiosperm leaf cuticles from the oldest part of the Potomac Group reinforce previous paleobotanical evidence for a Cretaceous flowering plant diversification. Dated palynologically as Zone I of Brenner (Aptian?), these remains show a low structural diversity compared to later Potomac Group and modem angiosperms. All cuticle types conform to a single plan of stomatal construction that is unusual in its extraordinary plasticity: both the number of subsidiary cells and their arrangement vary greatly on a single epidermis, such that the stomatamight be classified as paracytic, anomocytic, laterocytic, and intermediate. Such stomatal diversity is uncommon in extant angiosperms but is known from a few Magnoliidae. Many species possess secretory cells comparable to the oil cells of modem Magnoliidae, and a few show the bases of probable uniseriate hairs. None of the cuticle types can be assigned to a single modem family, but several show similarities with Chloranthaceae and Illiciales. These results support the concept that subclass Magnoliidae includes some of the most primitive living angiosperms.
CitationUpchurch, G. R. (1984). Cuticular anatomy of angiosperm leaves from the lower Cretaceous Potomac Group. I Zone I Leaves. American Journal of Botany, 71(2), pp. 192-202.
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