The Devonian Styginid Trilobite Paralejurus, With New Data From Spain and Morocco

Coaptative devices, enrollment, and life habits in Paralejurus, a particular case in scutelluid trilobites

“…Similar arguments have been recently developed by McKellar and Chatterton (2009) to explain the differences in the frequency of documented examples of volvation between some Early and Middle Devonian phacopids from southern Morocco. Semi-endobenthic life habits have already been suggested for Paralejurus by Schraut and Feist (2004) using lithological and morphological arguments. They emphasised that beds yielding this trilobite are most exclusively calcilutites with obvious evidence of bioturbation and therefore they constituted appropriate substrates for an endobenthic life style.…”

“…vaulted exoskeleton, effaced furrows, wide axis; Westrop 1983;Fortey 1986), the abundance of terrace ridges on its dorsal side (Schmalfuss 1981), the anterior arch below the frontal area in some taxa (Hammann 1985), and possibly also the presence of ridges on or nearby articulations (in so far as these latter prevented sediment particles from hindering free functioning of articulations, see above), all point to significant burrowing capacities in Paralejurus. These latter are emphasised after comparison with xiphosurans (Schraut and Feist 2004) which additionally indicate poor abilities for swimming, as well as by the postures of some specimens displaying dorsally inflexed thoraces (e.g. Fig.…”

“…As all these trilobites are provided with normally sized eyes, shallow off-shore muddy bottom conditions within the photic zone may be inferred for this population. The Late Emsian Paralejurus are common in thick beds of homogenous calcilutites of the Tazoulait Formation in the Maider region (Schraut and Feist 2004). Associated with numerous asteropygines, a lesser number of phacopids, other scutelluids, proetids and odontopleurids, they make up to 40% of the population.…”

“…Also, to complement the observations made on the two enrolled specimens of P. aff. brongniarti, juvenile and adult specimens of two additional species from Morocco, P. rehamnanus Alberti 1970 and P. tenuistriatus Schraut and Feist 2004, including one entirely enrolled adult specimen of the former, were also investigated. This revealed that these younger representatives (latest Emsian to earliest Eifelian) had developed a variety of structures that improved volvation and avoided lateral shearing.…”

The phacopine trilobite genera Morocops Basse, 2006 and Adrisiops gen. nov. from the Devonian of Morocco

“…Nonetheless, the incursion of "Bohemian" trilobites in the French Ardennes in the basal Eifelian indicates that exchange of trilobite faunas between the southern and northern margins of the Rheic Ocean was unhindered at this time. In fact, it has been suggested in other studies (e.g., Schraut & Feist 2004;van Viersen 2013van Viersen , 2015 that the incursion of "Bohemian" trilobites in Laurussia already started in the Emsian or even the Pragian. We regard this as evidence to support the putative close relationship between species of Morocops and Geesops despite the fact that they were separated by an ocean.…”