We would like to thank the following for permission to use drawings and pictures, individually acknowledged, from the following Journals and Museums
In the early Devonian plants started to radiate and four different groups of plants can be distinguished: the Lycopods, the Rhyniophytes, the Trimerophythes and the Zosterophyllophytes. From the famous silicified material from the Rhynie Chert, a lower Devonian sinter deposit with exceptionally preserved plants and animals much has been learned about early plant life.
This tiny branchiopod crustacean (clam shrimp) can be found in most Devonian sediments and indicates a shallow water environment. It is common in the Upper Stromness and Rousay Flagstone groups. Depending on the type of sediment and the conditions of fossilization Ipsilonia orkneyensis is preserved as a tiny (few mm) thin valve often with growth lines (concentric rings) visible, see photomicrographs below.
The earliest stromatolites are found in the Precambrian. Stromatolites are sedimentary structures formed by cyano bacteria (blue green algae) together with other bacteria and algae. They play an important role in the Devonian of the Orcadian Lake
This tiny fish is found in large numbers in Caithness at Achanarras Quarry and its equivalent locality at Niand on the eastern coast of Caithness. The fish is extremely rare in the Sandwick Fish Bed on Orkney, which is regarded equivalent in time to Achanarras Quarry and part of the same lake.
This medium size fish can reach a length of 30 cm and is well known from the Sandwick Fish Bed but, since it is often not well-preserved people don’t bother to collect it. However, it is a very important fish in the evolution of living fish. It has very tiny scales in the size range of acanthodians. The scales are covered with ganoine (see general page on this site on actinopterygians).
The actinopterygians are the group of fishes ancestral to all the ray-finned fishes. Everything from the seahorse up to tuna belongs to the ray-finned fishes, some 20,000 or more species. The only actinopterygian found in the Middle Devonian sediments of Orkney is the species Cheirolepis trailli. This species is one of the earliest articulated examples found from this group and is described in several publications. A bit later in time (Givetian, Upper middle Devonian) is Stegotrachelis finlayi, a species found on Shetland.
This dipnoan is a small to medium sized fish (although few examples are known of specimens over 30 cm, see picture at the top) and was the most common fish in the Eday Flags. It had tooth plates that looked similar to Dipterus. The fish is recently described by Tom Challands et al. (2016). It looks much like the Devonian lungfish Scaumenacia curta from Miguasha, Canada. Both species have no cosmine on their scales and head plates.
At the start of the 19th century the lungfish Dipterus was one of the first fish described in many papers. It has peculiar tooth plates and a strange lower jaw. Together with this, and the fact that there are still lungfish living today, it makes this a very interesting fish. On Orkney articulated specimens can be found in the Sandwick Fish Bed and disarticulated specimens almost everywhere. In the Eday Subgroup Dipterus is “replaced” by Pentlandia macroptera.
The lungfish from the Devonian Orcadian Basin are well known and described in great detail in many publications. A new species of dipnoan, Pinalongus saxoni was recently identified from Caithness and was named after Jack Saxon the famous fossil expert from Caithness, Scotland who died in 2005.