Ventarura taking shape
deutsche Version

The latest discovery of a „higher“ plant in the Lower Devonian Rhynie chert dates back no further than to the mid-nineties. As described in [1] it had been found in fragments of one large pod dug up near the Windyfield farms and thus named Ventarura, which is the Latin equivalent of windy field. (*)
Cross-section of Ventarura upright shoot with reinforcing tube Its prominent feature is a conspicuous dark ring seen on cross-sections of the upright axes. It consists of cells obviously more resistant against decay than other parts of the tissue are. Various proposals concerning its possible function have been considered in [1]. ****

Fig.1: Ventarura cross-section of upright axis with typical ring consisting of persistent cell walls. Width of the section 5mm;

Additional structural information came unexpectedly from a small piece of chert (0.2kg) found in 1998, whose true nature was recognized only after the paper [1] became available (**). In addition to Ventarura cross-sections as the one in Fig.1 it shows pairs of such. One type of sections (Fig. 2) seems to represent the 30 forking reported in [1], which may occur near the fertile region. Another type, also pictured in Fig.4, may occur below or on sterile shoots. The branching seems to be fairly symmetrical here but there is other evidence [2] that this is not always so.
Ventarura fork section

Fig.2: Cross-section of forking axis of Ventarura. The dark tube inside has become two separate tubes but the faintly seen outline indicates that there is a connection between them (see Fig.4). Note also the horizontal agate bands revealing that the plant was not upright but lying low during silicification. Width of the picture 13mm.

First evidence of curled tip of Ventarura shoot
Another thin slab cut from the small specimen in 2004 reveals a tiny incurved tip, probably the top of a not fully grown-up shoot (Fig. 3). This sparse additional fossil material discovered lately has led to a tentative reconstruction (Fig.4).

Fig.3 (left): Section of incurved tip, dark spots possibly representing nascent sporangia. Width of the picture 4.6mm. Photograph: Hagen Sahm



Schematic drawing of Ventarura showing curved tips and forking sclerenchyma tube
Fig.4 (right): Tentative reconstruction of Ventarura based on [1] and own finds. (***)
 
Specimens found lately as well as those described in [1] indicate more profuse and unequal branching below. Also there is evidence for new shoots developing inside older ones, similar as observed with Trichopherophyton.

Annotations
*   The chert where Ventarura was discovered differs in location and stratigraphy from the previously known stack of Rhynie chert layers and therefore has been named Windyfield chert [3].
** This chert sample was found well away from the Windyfield site so that it is either displaced Windyfield chert or else can serve as first evidence for the presence of Ventarura in other Rhynie chert layers.  Presented at the 3rd Chert Meeting, Chemnitz, 2004.

*** According to [1] and a few new finds, the rhizome is more profusely branched.
**** Evidence contradicting the idea of a reinforcing tube inside Ventarura has been accumulated since. See
Rhynie Chert News 60, 66, 82 .

Sample: 0.2kg, found by
Sieglinde Weiss in 1998. The rolled-up tip in Fig.3 has remained the only one ever found up to now (2016).

H.-J. Weiss      2005, emended up to 2016

[1]   C.L. Powell, D. Edwards, N.H. Trewin: A new vascular plant from the Lower Devonian Windyfield chert, Rhynie, NE Scotland.
      Trans. Roy. Soc. Edinburgh, Earth Sci. 90(2000 for 1999), 331-349.
[2]   www.abdn.ac.uk/rhynie
[3]   N.H. Trewin, C.M. Rice:  Stratigraphy and Sedimentology of the Devonian Rhynie chert locality.
      Scottish J. Geol. 28(1992) , 37-47.
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