A new mobergellan (small shelly fossils) from the Middle Cambrian of Morocco and its significance

A new mobergellan genus and species, Tateltella ranoculata, is described from the early Middle Cambrian (Agdzian Stage) of Morocco. The new taxon is characterized by only four pairs of muscle scars and is furthermore distinguished from other mobergellans by its strongly concave shape and its distall...

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Bibliographic Details
Published in:Palàˆontologische Zeitschrift 2006, Vol.80 (3), p.209
Main Authors: Streng, Michael, Skovsted, Christian
Format: Article
Language:English
Subjects:
Earth sciences
Exogen geovetenskap
Exogenous earth sciences
Geovetenskap
Historical geology and palaeontology
Historisk geologi och paleontologi
Middle Cambrian
Mobergellidae
Morocco
NATURAL SCIENCES
NATURVETENSKAP
phylogeny
shell structure
small shelly fossils
taxonomy
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Summary:A new mobergellan genus and species, Tateltella ranoculata, is described from the early Middle Cambrian (Agdzian Stage) of Morocco. The new taxon is characterized by only four pairs of muscle scars and is furthermore distinguished from other mobergellans by its strongly concave shape and its distally rising muscle scars. The individual specimens of Tateltella ranoculata distinctly vary in size and display different ontogenetic stages. Juvenile, intermediate, and adult stages can be distinguished by means of the development of the muscle scars that differ in position relative to the apex, size, and distinctness between individual stages. The shell of T. ranoculata is composed of a succession of thin phosphatic lamellae separated by interlamellar gaps, presumably originally filled by organic material. The interlamellar gaps may be divided by septum-like structures producing discrete cavities. The specimens are the youngest mobergellans known so far and correlation of their stratigraphic position suggests a correspondence with the lower part of the Amgan stage of the Siberian Platform. In addition, they are the first reported mobergellans from the present day continent Africa. Other mobergellan taxa and mobergellan-like species are briefly reviewed and the genus Hippoklosma MISSARZHEVSKY, previously assigned to the Mobergellidae, is excluded from the family due to its different shell structure. An evolutionary trend of reduction in the number of muscle scars from 14 in the early Early Cambrian to only eight in the early Middle Cambrian is apparent among mobergellans.
ISSN:0031-0220