Name: The Hunsrück Slate
Location: Western Germany
Age: Devonian
 


FLORA AND FAUNA


FAUNA

Around 300 species of animals have been described from the Hunsrück, dominated by benthic organisms, which come in a variety of shapes and sizes indicating juveniles as well as adults. The fauna includes major aquatic groups such as crustaceans, chelicerates, echinoderms, arthropods and fish. Sessile forms include crinoids, sponges, corals, bivalves, brachiopods and bryozoans.

   

An example of a pyritised starfish , the ophiuroid Loriolaster mirabilis.

Taken from Bartels, Briggs and Brassel, The Fossils of the Hunsruck Slate, Marine Life in the Devonian, Cambridge University Press, figure 29, p. 44. Collection Bartels, in German Mining Museum Bochum, Coll. Bartels. Used by kind permission of the Bergbau Museum, Germany.

The trilobite Chotecops in normal and enrolled state.

Taken from Bartels, Briggs and Brassel, The Fossils of the Hunsruck Slate, Marine Life in the Devonian, Cambridge University Press, figure 38, p. 58. Collection Bartels, in German Mining Museum Bochum, Coll. Bartels. Used by kind permission of the Bergbau Museum, Germany.

The vagrant benthos is dominated by trilobites such as Chotecops, which is often preserved in a partly enrolled state. When enrolled either the head (cephalon) or tail (pygidium) are tucked underneath the body. The rolling may be a defensive response by the organism, protecting itself from being overwhelmed by sediments.

The Hunsrück yields the only known example of an adult pycogonid (sea spider). Pycogonid walking limbs have eight segments and terminate with a pronounced claw. Limbs also had spines on the ventral margin. The sea spider was clearly a predator and possibly lived on sessile animals, gripping them with its claws.

   
The pycogonid Palaeoisopus problematicus. Taken from Bartels, Briggs and Brassel, The Fossils of the Hunsruck Slate, Marine Life in the Devonian, Cambridge University Press, figure 131, p. 154. Collection Bartels, in German Mining Museum Bochum, Coll. Bartels. By kind permission of the Bergbau Museum, Germany. Mimetaster hexagonalisTaken from Bartels, Briggs and Brassel, The Fossils of the Hunsruck Slate, Marine Life in the Devonian, Cambridge University Press, figure 96, p. 121. Collection Bartels, in German Mining Museum Bochum, Coll. Bartels. By kind permission of the Bergbau Museum, Germany.

There are a variety of forms that do not fit easily into the major groups such as Mimetaster, which has a star- like appearance, with six radiating spines. More than 20 individuals of Mimetaster hexagonalis are preserved in one slab, at the Eschen-Bocksberg quarry, suggesting a mass mortality event. Vachonisia is another form which was originally thought to be a branchiopod crustacean.

Larger swimming organisms include cephalopods and fish. The fish include the agnathans and the placoderms, many of which are arthrodires. The fish are flattened, which is a good indication that they lived on the substrate.

Agnathans are primitive jawless fish, ranging from 95 mmm to 685 mm in length, though most specimens are between 350-450 mm. Placoderms were diverse in the Devonian and had jaws but lacked replaceable teeth. Specimens are generally fragmented. The largest predator was an arthrodire which may have reached 2m in length.

 
Lenaspis heroldi.Taken from Bartels, Briggs and Brassel, The Fossils of the Hunsruck Slate, Marine Life in the Devonian, Cambridge University Press, figure 214, p. 233. By kind permission of Cambridge Univeristy Press and the Bergbau Museum, Germany.

Lenaspis,a placoderm, is known from relatively complete specimens, 300-450 mm long. The body is flattened, and it has Lenaspis had a flattened body with specimens a long head covered by bony plates. Large spinal plates project in front of the pectoral fins.

FLORA

Plants are terrestrial inhabitants of wetlands along coasts or inland. Spores are much more common than plant macrofossils because they are easily transportable. So far 40 species have been identified. Organic maturation studies indicate that during the Carboniferous metamorphic event the sediments were heated to a temperature of 400°C.

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