Fossil species, some of which attained a great size, are known, to which the name Equisetites is given, since they appear to be closely allied to the existing forms. Two other extinct genera, Phyllotheca and Schizoneura, may be mentioned here.
Our knowledge of the extinct Equisetales, full as it is with respect to certain types, does not suffice for a strictly phylogenetic classification of the group. The usual subdivision is into Equisetaceae including Equisetum and Equisetites (with which Phyllotheca and Schizoneura may be provisionally associated), and Calamariaceae, including Calamites and Archaeocalamites.
Among other well-known Jurassic genera Nathorst has identified the following: Equisetites, Cladophlebis, Todites, Thinnfeldia, Otozamites, Williamsonia pecten, Araucarites.
The Palaeozoic Calamites were succeeded in the Triassic period by large Equisetites, differing, so far as we know, in no essential Equ;se- respect from existing Equisetums. The large stems taceae.
represented by casts of Triassic age, Equisetites arenaceus and other species, probably possessed the power of secondary growth in thickness; the cones were of the modern type, and the rhizomes occasionally formed large underground tubers like those frequently met with in Equisetum arvense, E.
Equisetites Muensteri is a characteristic and fairly widely spread Rhaetic and Liassic species, having a comparatively slender stem, with leaf-sheaths consisting of a few broad and short leaf-segments.
Equisetites columnaris, a common fossil in the Jurassic plant-beds of the Yorkshire coast, represents another type with relatively stout and occasionally branched vegetative shoots, bearing leaf-sheaths very like those of Equisetum maximum and other Horsetails.
Equisetites Burchardti and E.
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