Home • CORE Members/Images of Them• Contact • Publications • Free Reprints of F&S Monographs • Related Sites and Links • Imprint

Other Faunal Components

The 'Orsten' arthropod fauna in general is interpreted as a special bottom fauna, more precisely a fauna living in and on a flocculent bottom layer (fluff zone), or at the sediment water interface of this layer. Its size range indicates that most if not all Orsten animals can be regarded as representatives of the meiofauna.

Viewing at the alum shales and the limestone nodes as a special event leading to their growth, one has to think of a dysoxic bottom water regime of a possibly offshore sehelf region, maybe some 50-100 m deep. The bottom was organic rich, a soft muddy zone (but no clay! which is absent in Orsten rocks as much as any sand minerals) with a flocculent layer on top. A comparable environment is present, e.g. in the Golfo San George, Argentina. It is characterized by a fairly specialzied, therefore, species-poor macrofauna, lacking several components of hard substrate areas (Dieter cruised there in 1978 on board of the German fisheries research vessel "Walother Herwig"). Indeed the trilobites of the Alum shales, for example, are rather small and special compared to other faunal regimes.

Euan Clarkson, who is working on trilobites from the Alum Shales of Sweden, has described long-spined forms, which might have rested on their cephalic spines and cound hold their tain above the muddy bottom. Each stratum of the former Upper Cambrian Alum-shale sequence has its special trilobite, often exclusive and variously, small agnostids, equally specific. Creepers like annelids, molluscs or echinoderms seem to me absent, but also so-called mud stickers. Actually, Dieter has not seen them in samples collected by him in the Golfo-San-George area of the Argentinian coast .

A more in-depth-investigation of all alum-shale and nodule faunal components has not yet been made so far, but would be really interesting and helpful, but at present no one has dared to do the job.

Trilobita (for this group in general see this site in English or this in German)

Several trilobites occur in the later Cambrian strata in Sweden, often known as zone fossils. Yet, while being partly abundant in the shales and also within the nodules, after etching not a single piece has been detected that could be affiliated with trilobites – strange as it is. Their cuticle seems completely different. We only have empty shells of later stages of agnostids.

Trilobite on a piece of alum shale, region Falbygden, Västergötland, Sweden.

Brachiopoda (for this group in general see this site)

Brachiopods occur in the form of horny-shelled taxa in Swedish nodules and they are also numerous on the bedding planes of the surrounding alum shales (alum skiffer). Due to their shell size of about 5 mm, they are easily to be detected. Empty shells are abundant and uncompacted. Few specimens, smaller than 1 mm, have been etched in 3d from the limestones, with their lophophore carriers still in place. – For details you might contact Lars Holmer from the Rijksmuseet in Stockholm.

Conodontophorida (see also this site)

Conodonts often occur in a translucent-whitish preservation and are fairly common in all uppermost Middle Cambrian to uppermost Furongian strata in Sweden (e.g., Müller & Hinz 1991). Conodonts have been subdivided into proto- para- and euconodonts. If may even these do not form a natural assemblage of taxa, i.e. that part of this set does not belong to craniote chordates, the place suggested for the euconodonts. Protocononts have rather been affiliated longer ago with chaetognaths, a still enigmatic group of pelagic/planktonic predators (e.g., Szaniawski). Jean Vannier and his collaborator David Casenove form France are going to restudy this.

More Taxa

Palaeoscolecida (pictures in the next future)

This is a diverse group of vermiform animals with a slender, multi-annulated body and an integument adorned with numerous plates of different sizes and shapes. Palaeoscolecids, which we consider as cycloneuralian nemathelminths, occur widespread in Early Palaeozoic sediments and may eventually have some potential as index fossils (Müller & Hinz-Schallreuter 1993). Isolated tesserae or plate-like pieces of cuticle have been previously described as „small shelly fossils“ under names like Hadimopanella or Lenargyrion. A particularly well-preserved example in the material may be determined as aff. Hadimopanella oezguli Gedik, 1977 (Müller et al. 1995, their fig. 5C), as based on its simple configuration of nodes with a circular base on its upper side.

Several problematic fossils have also been etched from the rock, such as various small, globular, hollow balls, approximately 160 µm in diameter and having a faint neck around a circular aperture of 65 µm in width. Preservation is rather poor and granular (Müller et al. 1995, their fig. 5D). A single specimen of another problematicum is discoidal and very flat, about 200 µm in diameter and 20-30 µm thick. It seems to be coiled, with the wide end of the shallow helix deeply excavated (Müller et al. 1995, their fig. 5E, F).
Other taxa include chancelloriids, sponge spicules preserved either in silica or in probably glauconitic matter (see above), fragments of phosphatic tubes, and fecal pellets.

In all, we think, there is much potential in a more detailed faunistic analysis also with regard to future exploration of more localities yielding 'Orsten'-type preservation.

For the different species described from Orsten sites see also:
To top To top   Last revision: September 25, 2009