1 D19. Paleontology: Invertebrate Paleobiology

Sunday, 22 September 2019
8:00 AM - 12:00 PM
Room 227ABC, North Building

COMPOSITE SEA STAR REPICHNIA/CUBICHNIA AND ASSOCIATED ICHNOFOSSILS FROM UPPER ORDOVICIAN SILTSTONES WITHIN THE KTAOUA GROUP, RAMLIA, MOROCCO

Paper number: 1-9
Program: Technical Sessions
Time: 10:00 AM – 10:15 AM

Authors

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.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-334329

© Copyright 2019 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.