Fossil groups from the Soom Shale

The fauna of the Soom Shale is characterised by nektonic and necktobenthic species, with conodonts being particularly common (Aldridge et al. 1994).  The conodonts are represented by isolated elements and, more commonly, by partial or complete feeding apparatuses;  several of the apparatuses have associated soft tissues, especially traces interpreted as representing the eyes, and one more complete conodont animal, preserving eye and trunk musculature, has been discovered (Gabbott et al. 1995).  The conodont elements are all extremely large, commonly 10-20 mm in length, and are all referable to a single species, the prioniodontid Promissum pulchrum.  Other nektonic fossils include a Jamoytius-like naked agnathan and orthoconic cephalopods, the latter of which are commonly encrusted by lingulate brachiopods and cornulitids.  Isolated lingulate brachiopods, including rare specimens of Lingula, and occasional ribbed articulate brachiopods also occur.  Arthropods are represented by the eurypterid Onychopterella, the naraoiid Soomaspis, the trilobite Mucronaspis, myodocopid ostracods and possible phyllocarids.  Soft tissues are particularly well preserved in several of the eurypterid specimens, which display musculature and book-gills.  The fauna also contains a number of enigmatic forms, some of which are soft-bodied and difficult to assign to a phylum;  additionally, there are numerous scattered organic-walled spines (Siphonacis) of unknown affinity.  Chitinozoans are abundant on some bedding planes as scattered individuals, large clusters or long chains;  they are sometimes associated with the orthocones or the conodonts.  Palynological preparations of the shale have produced more chitinozoans, as well as simple spores and spherical acritarchs.

In addition to providing a rare Ordovician conservat-Lagerstätte, the Soom Shale preserves a unique Early Palaeozoic cold-water community.  There is an apparent dominance of vagile predators and scavengers (conodonts, orthocones, large arthropods), with only the brachiopods and cornulitids evidently occupying a consumer niche.  The common habit of the lingulate brachiopods as pseudoplanktonic epibionts on orthocone shells attests to an inhospitable or barren sea-bottom environment.  The myodocopid ostracods are only found in association with the orthocone conches, on which they may have been scavenging.  There is evidence for the presence of undiscovered large predators or scavengers in the fairly common occurrence of coprolites containing crushed orbiculoid shells or fragmentary conodont elements.

Find out more about the different fossil groups preserved in the Soom Shale by clicking on the menu on the left.

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