Abstract

A review of all known species of the scutelluine trilobite Paralejurus corroborates its distinction from contemporaneous representatives of the subfamily. The overall morphology together with observed habitat conditions favor the view of its having had a semiendobenthic life habit analogous to that of many earlier illaenids. Particular features that are shared with the Silurian Rhaxeros, such as the pronounced convexity of the exoskeleton and the wide axis, are considered as homeomorphies related to a burrowing lifestyle rather than the expression of phyletic relationships. The data set based on conodont biostratigraphy reveals earliest occurrences of Paralejurus in the Pragian and the disappearance of last representatives at the base of the Middle Devonian. In the lower Early Devonian Paralejurus was restricted to the North Gondwana margin and related microplates. Later and in consequence of geodynamic plate movements that led to the reduction of oceanic barriers, the Paralejurus dormitzeri group succeeded in spreading to the epicontinental margin of Laurussia in Late Emsian times. New material from Southern Morocco, including Paralejurus spatuliformis n. sp. and Paralejurus tenuistriatus n. sp., and the first representative of the genus from Spain, Paralejurus carlsi n. sp., are described. Paralejurus dormitzeri rehamnanusAlberti, 1970 is considered an independent species emphasized by the discovery of complete exoskeletons.

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