Ferns from Yorkshire
|Click on the photos for more information.
Many of the plant fossils from the North Yorkshire coast belong to the group of the ferns. One of the most common ferns is Todites williamsonii, a representative of the Osmundaceae family, which includes also the living Royal Fern (Osmunda regalis). The leaflets (pinnules) of this species are often somewhat bent upward and in many cases they are occupied with sori (clusters of sporangia) on the lower side. The axes of the pinnae (a pinna is an axis with leaflets) and also the main axes are relatively thick. The pinnae are long and they have almost parallel sides (they are gradually getting narrower to the top). Click on the photo on the right for more pictures.
There is also a species with denticulate leaflets: Todites denticulata, which has fertile as well as sterile leaflets on the same frond.
In Cayton Bay many specimens are found of a species with pointed, sharply toothed, exclusively sterile leaflets. This species is called Cladophlebis denticulata. The relationship with Todites denticulata is not yet cleared. Possibly these are sterile leaves of the latter plant, but they could also be leaves of a completely different plant from the Royal Fern family. Click on the photo on the right.
common fern is Eboracia lobifolia (click on the photo to the left;
Eboracum is the Latin name for York). The foliage resembles that of Todites
williamsonii very much, but the axes are more slender. Todites:
thick axes, Eboracia: thinner axes. A second difference is that in
a complete pinna the basal leaflet in Eboracia differs from the other
leaflets (larger and split in segments), while they are all the same in
Todites. Furthermore the leaflets of Eboracia are somewhat
undulated while those of Todites look more rigid.
Eboracia belongs to the Dicksionaceae family, which has the sporangia arranged in groups (sori) along the borders of the leaflets.
(rather large) leaves of Dictyophyllum rugosum are reminiscent of
leaves of modern, flowering plants, because they show a reticulate venation.
Mostly only fragments are found but these are easily recognisable. Click
on the photo on the right.
Dictyophyllum is a species from the Dipteridaceae, the only one still living fern family with real reticulate venation.
Phlebopteris polypodioides is also a plant with living relatives (family Matoniaceae). The leaflets are characterized by angular veins, sometimes forming a partly reticulate pattern (click on the photo on the left). Furthermore the sori (if present) are arranged parallel to the midrib.
exilis is a small fern which can be found rather easily in the Gristhorpe
Plant Bed, but which is rare elsewhere in the Yorkshire area. It is a guide
fossil for the Middle Jurassic. The leaflets are attached
Pecopteris-like, i.e. with a broad base. Click on the photo to the
Klukia exilis is a member of the Schizaeaceae, a fern family with relatively large sporangia, each placed apart on the lower side of the leaflets along the secondary veins.
In Hayburn Wyke fossils of the genus Coniopteris are abundant, but they occur also in other places, however less frequent. They are ferns with strongly branched leaves, which are, however, in most cases severely damaged before fossilizing. Almost always one finds detached pinnae or parts thereof.
The species Coniopteris hymenophylloides (because of the difficult name also informally called Conhym) is very common. Fertile as well as sterile leaves are found and these are rather different: the fertile leaflets are strongly reduced. Click on the photo on the left.
Coniopteris murrayana has overlapping leaflets and pinnae, but
this is not a reliable feature. It is better to look at the form of the basal
leaflet of a pinna (but regrettably these are rarely preserved). In Conhym
the first basal leaflet on the lower side of the pinna is finely divided
(aphlebia-like), while in Coniopteris murrayana just the first basal
leaflet on the upper side is finely divided ... I haven't found a convincing
specimen of Conmur.
Just like Eboracia, Coniopteris belongs to the Dicksionaceae family.