Holes gnawed into early land plants by elusive creatures
deutsche Version

Some of the various phenomena of damage to live plants are known from the Lower Devonian. A few specimens of the early land plants as those preserved in the Rhynie chert show signs of having been affected by some unknown agent. Most conspicuous are the big radially oriented void patterns occasionally appearing on cross-sections of Aglaophyton (Fig.1). They are certainly not due to creatures but represent a growth anomaly probably caused by some unidentified fungus pervading the tissue. Cavities of quite another type are those left by herbivores, like the one also seen in Fig.1, above right, and those in Figs.2,3.

Fig.1 (left): Cross-section of Aglaophyton with "flower-shaped" pattern of voids due to misguided growth, probably under the influence of some fungus, and with an additional hole in the tissue. Image width 4.4mm.
Aglaophyton with void patternAglaophyton with holeAglaophyton with hole_
Figs.2,3: Cross-sections of Aglaophyton with cavities eaten into the tissue by some unknown creature able to make an entrance, feed, and retreat.
widths Figs.2,3: 4.3mm, 2mm.

By lucky incidence the cut plane in Figs.2,3 reveals the access hole. The peculiar shape of the cavity with entrance suggests the idea that a lengthy creature crept half in, turned to either side while feeding, then retreated backwards. The creature seems to have visited its feeding place repeatedly since it could hardly have eaten the amount of tissue at one time.

Apparently there were creatures demanding food other than mere parenchyma tissue. They had gnawed holes into spore capsules with the intent to get at the spores (Fig.4). Since the chance of finding a hole on an arbitrary sample face is small, and a few have been found on sporangium walls, they are not quite rare. (The very existence of holes in sporangia of Aglaophyton was doubted not long ago, in 2004.)
The outer sporangium wall consisting of the so-called palisade cells, apparently meant to scare off offenders, had been removed locally to make the access hole seen in Fig.4. With another sample, a cavity in the inner sporangium wall with loose spore tetrads incidentally fallen in is seen in Fig.5. Remains of the decayed outer wall are hardly visible at the bottom of the frame.
Aglaophyton sporangium with hole
Aglaophyton spores
Fig.4 (left): Aglaophyton sporangium with hole gnawed through the outer and inner wall.
Image width 3.4mm.

Fig.5: Aglaophyton sporangium detail: cavity eaten into the inner wall, scattered spore tetrads.
Image width 2mm.

Fig.6 (below): Aglaophyton sporangium wall with cavity and access hole in the "palisade wall".
Image width 3mm.

Aglaophyton sporangium wall with hole
The damage had been done to the live plants as can be concluded from repair activities also seen in similar cases. This clearly contradicts the statement in [1], p47, that "There is no evidence of animals that eat living, growing plant material."
What remains to be done is to find the creatures which made the holes. This will be difficult since no creature has been seen in these chert samples. It may be concluded from Fig.2 and Fig.6 that the diameters of the
access holes are about 0.4mm. There must have been creatures able to squeeze themselves through these holes.
Other indications of the potential presence of unseen creatures looking for spores are provided by Nothia with its big tubes probably containing poisonous liquid serving as a repellant, also by Trichopherophyton with its pointed bristles.
The holes gnawed through unprotected capsule walls and the apparent precautions against attack on sporangia, like bristles and poison, seem not compatible with the statement that "The evidence for deliberately targeted spore-feeding in the Early Devonian is not conclusive" [2]. Spherical or ellipsoidal clots consisting of spores, possibly taken from sporangia and carefully glued together,
also seem to support the idea of spore feeding.
To sum up, access holes and cavities had been eaten into live specimens of the early land plant Aglaophyton by elusive herbivores.
RhX/1.2 (1.33kg): Fig.1.   Rh6/78.2 (0.1kg) found in 2003: Fig.2.   Rh15/84.1 (1.3kg) obtained from Barron in 2014: Fig.3.   Rh2/75.11 found before 2004: Fig.4.  
Rh2/98.1 (9.5kg) obtained from
in 2003: Fig.5.    Rh6/38.2 (about 0.2kg) found in 2003: Fig.6.     Weights refer to undivided samples.

H.-J. Weiss       2021  (slightly modified version)

P.G. Gensel, D. Edwards (eds.): Plants Invade the Land. Chapter 3: W.A. Shear, P.A. Selden: Rustling in the Undergrowth. Columbia Univ. Press (2001).
[2]  K.S. Habgood, H. Hass, H. Kerp: Evidence for an early terrestrial food web: coprolites from the Early Devonian Rhynie chert.
        Proc. Roy. Soc. Edinburgh, Earth Sci. 94 (2004), 371-389.
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