Empty cephalopod conchs as substrates for gastropod eggs from the Hangenberg Black Shale (Late Devonian) of the Maïder Basin (Morocco)

Abstract

In the latest Famennian, black shale deposition occurred in many regions, some suggested a marine transgression
as the explanation while others saw a link with higher organic input from the land. In either case, the Hangenberg Black Shale was most likely deposited under low oxygen conditions, which enabled exceptional fossil preservation in some regions such as the southern Maïder Basin of Morocco. Here, we provide the first account of small circular structures, in some cases with thin carbon films, which remained on ammonoid and bactritoid conchs. Due to similarities in their morphology and size with other occurrences documented from Europe, we propose that these structures may represent gastropod eggs. We also discuss whether egg-deposition occurred in the water column or on the sediment surface.
Key words: Ammonoidea, Bactritoidea, Vetigastropoda, Famennian, taphonomy, Konservat-Lagerstätte