Composite sea star Repichnia/Cubichnia and associated ichnofossils from Upper Ordovician siltstones within the Ktaoua Group, Ramlia, Morocco

Joseph Devera, Hassane M'Hamdi

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

An ichnofossil assemblage found near Ramlia, Morocco in an Upper Ordovician siltstone represents intertidal to subtidal transition. A trackway preserved as hypichnial podia marks appear to be made by tube feet of an asteroidean. One slab collected shows the composite relationship between the repichnial traces and cubichnial trace of Astericites. Preservation of connected behaviors, in this case repichnia and cubichnia of a sea star are rarely found together. Diameter of trackways range between 3 to 6 cm. Hyporeliefs of the podia yield circular impressions suggesting that the tube feet had terminal disks or suckers. The meandering repichnia in a larger Ordovician slab is similar to some modern asteroids that inhabit the intertidal environment. Along with asteroidean repichnia/cubichnia are traces that are considered to be repichnial movements of the same species of sea star preserved in siltstone layers above the trackway of the sea star. This may have occurred in the water saturated zone where the organism was moving through thixotropic silty sediment leaving a unique epichnial trace of movements of the arms of the sea star. Other associated traces are Diplichnites, Cruziana and Rusophycus, which occur with asteroidean traces. Smaller repichnial hyporeliefs and horizontal "worm" tubes are also found.
Original languageEnglish (US)
Title of host publicationAbstracts with Programs - Geological Society of America
Volume51
DOIs
StatePublished - 2019

Keywords

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