That’s a lot of fossils in a title! I’ve decided to do a short blog post on the Fossil Courtyard in the Royal Botanic Gardens Edinburgh (RBGE), one of the network of national botanic gardens in Scotland. The Fossil Courtyard contains two fossils but they are big specimens.
The first one is the largest fossil plant known from Great Britain, an example of one of several specimens of Pitus withami, one of the large trees that grew in the wetlands of the Carboniferous Period that provided the raw organic material that was transformed into coal.
However, this tree was impregnated with minerals from hot fluids (permineralized), which stopped it from decaying to form peat. With the action of increased pressure and temperature due to deeper burial, peat becomes various grades of coal, culminating in the ‘black diamonds’ of anthracite, the highest grade of coal.
This specimen, along with one that may be found in the grounds of the Natural History Museum, came from the huge quarry at Craigleith in the Gullane Formation that produced so many of the sandstone blocks that were used in the construction of buildings around Edinburgh. Like so many former quarries, it has been filled in to allow buildings to be erected on the reclaimed land. All that remains of the lost quarry now are a few exposed faces.
The other specimen behind the titanic tree is an example of the root system, called Stigmaria, of the large tree-like form Lepidodendron. The root systems are quite often found in the Carboniferous rocks exposed along the coasts of the Lothians and Fife.
One of the challenges that palaeobotanists face is that parts of the same plant may turn up in the fossil record separate from each other. So palaeobotany becomes a case of naming the parts and then gaining an understanding of which fossil elements are elements of the same plant. Another internationally important site, Fossil Grove in Glasgow, provided the key evidence that helped demonstrate that Stigmaria and Lepidodendron were part of the same organism.
Lepidodendron, unlike Pitus withami, does have some close living relatives: the clubmosses. In contrast to the huge size of Lepidodendron, which could grow to 45 m in height, clubmosses are usually only a few centimetres tall. The place I most often see those plants is among the vegetation communities of the high mountains of Scotland. However, if you pay to enter the glasshouses of the Botanics, you can see a larger range of the living relatives of fossil plants . If you do venture into the Ferns and Fossils House look out for the replica model of Westlothiana lizzae, aka ‘Lizzie the Lizard’, that Stan Wood excavated from the East Kirton Quarry in West Lothian. But that is another fossil story.