Quercy Phosphorites Formation

The Quercy Phosphorites Formation (French: Phosphorites du Quercy) is a geologic formation and lagerstätte in Occitanie, southern France. It preserves fossils dated to the Paleogene period (latest Bartonian to Late Oligocene), or MP16 to MP28 zones of the European land mammal age classification, ranging from approximately 38 to 25 Ma.

It qualifies as a Lagerstätte because beside a large variety of mammals, birds, turtles, crocodiles, flora and insects, it also preserves the soft tissues of amphibians and squamates, in addition to their articulated skeleton in what has been called natural mummies.

The genera Quercylurus, Quercymegapodius, Quercypsitta, Quercypodargus, Quercycerta and Quercygama, and species Mosaicomeryx quercyi, Robiacina quercyi, Palaeophyllophora quercyi, Archaeomys quercyi, Eomys quercyi, Eucricetodon quercyi and Tarnomys quercynus, as well as the lizards Paraplacosauriops quercyi and Pseudolacerta quercyini and the insect Palaeortona quercyensis were named after the formation.

Description
The first phosphate deposits in Quercy were discovered in 1869 and published by Daubré and Trutat independently in 1871. The first fossils from the formation were described by Delfortie (1872) and Gervais in the same year and extensively studied by Filhol from 1877 onwards. The first geologic investigation of the formation was performed by Thévenin in 1903, and apart from a description by Gèze in 1938, the paleontological richness was not studied until a team of researchers of the Universities of Montpellier and Paris visited the site in 1965.

The karstified phosphate deposits are found from the Lot and Célé river valleys in the north to the left bank of the Aveyron in the south and from the Villefranche Fault in the east to the lacustrine deposits of the Aquitaine Basin in the west. The formation is found in fissures (karst) incising Jurassic and Triassic rocks east of Cahors. The age of the fossiliferous unit, in which almost 12,000 specimens were found ranges from the MP16 to MP28 zones of the European land mammal age classification. These ages correspond to the latest Bartonian to Chattian, from about 38 to 25 Ma.

Paleontological significance
The Quercy Phosphorites Formation is a highly fossiliferous unit designated as a Lagerstätte due to the excellent preservation of fossils. The phosphorite conserves up to the nerves, digestive tract and stomach content, insect larvae and other elements of the paleobiology in the formation. Nearly all Quercy fly pupae were preserved as isolated endocasts, of which many were still covered by the puparium, the hardened skin of the last larval instar. The formation also straddles the Grande Coupure and shows diversity changes (number of species) of frog, salamander, lizard and snake fossil records across the formation. It is assumed that the Quercy arthropods fossilized by a rapid fixation by phosphate-rich water followed by encrustation and mineralization.

Fossil content
The following fossils have been reported from the formation:

Apatemyidae

 * Artiodactyls

Birds

 * Caprimulgiformes

Reptiles

 * Crocodiles
 * Lizards


 * Snakes


 * Cadurcoboa insolita
 * Coluber cadurci
 * Dunnophis cadurcensis
 * Eoanilius europae
 * Natrix mlynarskii
 * Palaeopython cadurcensis
 * P. filholi
 * P. neglectus
 * Paleryx cayluxi
 * Platyspondylia lepta
 * Plesiotortrix edwardsi


 * Turtles


 * Ptychogaster cayluxensis
 * Testudo phosphoritarum
 * Testudinidae indet.

Amphibians

 * Frogs


 * Bufo serratus
 * T. gezei
 * Thaumastosaurus bottii


 * Salamanders


 * Heteroclitotriton zitteli
 * Megalotriton filholi
 * M. portisi
 * Phosphotriton sigei

Insects

 * Coptera anka
 * Onthophilus intermedius
 * Palaeortona quercyensis
 * Xenomorphia handschini
 * X. resurrecta
 * Blattodea
 * Coleoptera
 * Diptera
 * Ensifera
 * Hymenoptera
 * Lepidoptera
 * Myriapoda

Flora

 * Palmocaulon sp.
 * Anacardiaceae indet.
 * Caryophyllales indet.
 * Malvaceae indet.
 * Menispermacae indet.
 * Sapotaceae indet.
 * Ulmaceae indet.
 * Vitaceae indet.