Spore-like bodies or cryptospores have been described from Middle Ordovician, Silurian and Lower Devonian rocks of continental and nearshore settings. They include 'permanent' alete monads, dyads and tetrads (e.g. Tetrahedrales, Fig. 13.12a). The botanical and evolutionary affinities of these microfossils are highly controversial. Some resemble the spores of modern bryophytes (Gray 1985; Richardson 1992) and some are referable to the Turma Hilates. A detailed description of this group can be found in Richardson (in Jansonius & McGregor 1996, vol. 2, pp. 555-575).

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Freehand Sketching An Introduction

Freehand Sketching An Introduction

Learn to sketch by working through these quick, simple lessons. This Learn to Sketch course will help you learn to draw what you see and develop your skills.

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