Kierarges morrisoni a rare Trilobite from Morocco

Description

This Kierarges morrisoni is a rare Trilobite from the Fezouata Formation north of Zagora. The well preserved complete specimen here measures 4.75″ or 12,1 cm. It comes as positive and negative. The relative unstructured pygidium shows very fine lines along the edges.The species Kierarges morrisoni is not only found in the Zagora region in Morocco but also in the Lower Ordovician of Portugal. The species Kierarges morrisoni was first believed to be a Trilobite known under different names prior to Kierarges morrisoni in 2014 by Corbacho. That Trilobite was first  described 1872 by Barrande as Asaphus alienus, that became Megistaspis alienus or Nerudaspis alienus (1965 Pribyl and Vanek). The sources here relied on a dozen parts parts and two incomplete specimen. They where found in the Sarka Formation of Praha Sarka and Osek in the Czech Republic. Kierarges morrisoni has a lot of similarities with its closed relative Megistaspis hammondi, that has been found also in the Fezouata Formation of Zagora/Morocco. However Kierarges does not have a long spine at the end of the pygidium, has a unstructured pygidium and the glabella shows no glabellar furrows.

The Fezouata Formation is deposited at a time, when Africa and South America where connected. The position of Africa back then was under the South Pole. The fossils of the Fezouata Formation are usually covered with a dust of Pyrite (leading to brown coloration) or tin minerals (leading to a red coloration). This is a similarity to the Cambrian Chengjang Shale in China. Another similarity exists in the composition of taxa to the Cambrian Burgess shale of Canada.

The well preserved complete specimen here measures 4.75″ or 12,1 cm. It comes as positive and negative. The relative unstructured pygidium shows very fine lines along the edges. Scratch on Pygidium.

Acknowledging that it is hard to find information about this Trilobite, Kierarges morrisoni is presented with one example on the website of the American Museum of Natural History under Ordovician Period Trilobites / AMNH. All other sources are scarce spread. One article is written in Spanish by Corbacho: ” Un nuevo genero de Isotelinae” and features pictures. The sources regarding Barrandes and Pribyl/Vaneks work: ” The Type Specimen of Fossils in the National Museum Prague, Vol.1 Trilobita” by the Museum of Natural History are published in 1970 and can be seen only in that book.

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Additional information