Palaeos Palaeos Lycophyta
Plants Zosterophylls


Zosterophyllum deciduum whole plant reconstruction; (B) ovale protostele of Zosterophyllum.
Class: Zosterophyllopsida - Order Zosterophyllales - Family Zosterophyllacea
Frasnian of Euramerica

image Lab V - Lycophytes (1)

The zosterophylls are a small group of extinct primitive plants that may have been ancestral to the lycopsids.  They are best known from the Early and Middle Devonian.  Zosterophylls looked very much like the contemporary rhyniophytes and like trimerophytes.  Like them, Zosterophylls lacked true leaves and roots, and photosynthesis was probably carried out all over the stems. As with the rhyniophytes each stem dividing into two branches of equal size (dichotomous branching).  

Zosterophylls differed from other plants by having round to kidney-shaped sporangia (spore-cases) that were born on small stalks arranged in clusters along branches.  That is, they had many lateral, rather than terminal, sporangia. The branch tips unrolled like the head of a fern.

Sawdonia ornata
Class: Zosterophyllopsida - Order Zosterophyllales - Family Zosterophyllacea
Devonian of Euramerica

image courtesy of the University of California Museum of Paleontology web site
Copyright The Museum of Paleontology of The University of California at Berkeley and the Regents of the University of California.

Some genera, such as Zosterophyllum (top of page) and Gosslingia (up to 50 cm tall) had smooth stems.  Others, like Sawdonia (above, up to 30 cm tall), Serrulacaulis, and Crenaticaulis had stems covered with saw-tooth or scale-like spiny flaps of tissue that lacked vascularization and so were not true leaves.  These same organs also occur among the trimerophytes.

Web links Links Web links

Introduction to the Zosterophylls

web pagedrawingsEarly Devonian Zosterophylls


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page uploaded 1 April 2002, last modified 2 May
checked and slightly modified ATW051231
unless otherwise indicated, content Creative Commons Attribution M. Alan Kazlev
this material may be freely used as long as attribution is given