Notostraca trackways in Permian playa environments of the Lodève basin (France)

Abstract

For nearly 20 years, Dr. Lapeyrie, surgeon at Lodeve, has gathered many fossils coming from the Salagou Formation of the Lodeve Permian basin. They are Insects, Notostraca, plants and ichnofossils. Among the latter, appears a multitude of Arthropoda trackways, finely preserved, which were collected in the top of sequences deposited in a playa environment. The locomotion experiments undertaken with extant animals suggested allocation of the majority of these trackways to Notostraca which are also known by several hundreds of remains (carapace, appendages, body whole). From these different parts, it was described as Triops cancriformis permiensis and Lepidurus occitaniacus. All these trackways were made under water and correspond to various etho-morphotypes known in the literature under the name of Acripes for the walking prints, Rusophycus for resting traces (= stationary digging; horizontal, procline and opisthocline positions) and Cruziana for locomotion active and digging. Many fossiliferous slabs clearly allow to see the passage from one activity to another. A similar situation was also filmed with the modern Lepidurus. The following ichnotaxa were distinguished: Acripes multiformis nov. isp, Rusophycus eutendorfensis, R. carbonarius, R. versans, R. minutus, R. furcosus, Cruziana problematica, C. pascens and Scoyenia, isp., less common. With also numerous footprints, this assemblage characterizes the Scoyenia facies restricted to overbank settings. For the Salagou Formation, they correspond to a floodplain/playa in which shallow and temporary pools were inhabited by Nostotraca, Insects, Arachnids and Conchostraca (= Spinicaudata + Laevicaudata), this last group only known by body-fossils. This distal playa environment under arid climate lasted during most of the Permian, possibly between Upper Cisuralian to lower Lopingian.