The Sables du Castrais Formation, also known as the Molasses du Castrais, is a geologic formation of Eocene (Ypresian to Bartonian) age,Marandat, B. (1987) La biostratigraphie mammalienne de l'Éocène continental du versant sud de la Montagne noire. Reconsidération d'après les nouvelles données. Muench. Geowiss. Abh. (A), 10 (1987), pp. 149-158 outcropping in the Montagne-Noire region of France.Noulet, J.-B. (1858) – Du terrain éocène supérieur considéré comme l'un des étages constitutifs des Pyrénées. Bulletin de la Société géologique de France, 1858, p. 277-284

History "Petrified fossil remains" were known from the Sables du Castrais Formation since at least the 18th century,Fauré, Philippe. (2011). UN PATRIMOINE GEOLOGIQUE PEU CONNU : LES GISEMENTS DE VERTEBRES FOSSILES DE L'EOCENE MOYEN DU CASTRAIS (TARN, LUTETIEN SUPERIEUR A BARTONIEN SUPERIEUR). and several of these fossils were described by Cuvier (1804) and Cuvier (1822) as belonging to Palaeotherium and Lophiodon.Cuvier, G. (1804). Sur les espèces d'animaux dont proviennent les os fossiles répandus dans la pierre à plâtre des environs de Paris. Ann. Mus. Nat. Hist. Nat. (1804), pp. 275-303 (Pl. 23-29)Cuvier, G. (1822) – Recherche sur les ossements fossiles où l'on rétablit les caractères de plusieurs animaux dont les révolutions du globe ont détruit les espèces. Nouvelle édition.. Tome second, 1er partie.

In 1845, a jaw assigned to Lophiodon lautricensis was discovered in the formation and was described by Noulet (1851);Noulet, J.B. (1851) – Sur une nouvelle espèce de Pachyderme fossile du genre Lophiodon (Lophiodon lautricensis). Mémoires de l'Académie des Sciences Inscription et Belles Lettre de Toulouse, 4 ser., t. I, p. 245-250. Noulet also mentioned that he had himself collected fossils from the formation alongside pharmacist J. Parayre as early as .Noulet, J.-B. (1863) – Etude sur les fossiles du terrain éocène supérieur de l'Agout (Tarn). Mémoires de l'Académie des Sciences Inscription et Belles Lettre de Toulouse, 6e sér., t. I, p. 181-206.

Léonce Roux du Carla discovered several more fossils from the Grès d'Issel Member of the Sables du Castrais formation from February 1855 until his death in 1859, and this helped Noulet (1858) to confirm the Eocene age of the deposit. Despite this, all that remains today of du Carla's collection is a single jaw of Palaeotherium castrense from the Sables du Castrais Formation.

Between 1850 and 1868, during the construction of the Castres - Albi railroad, several more fossils were recovered from the Sables du Castrais Formation, including M. Zebrowsky's 1868 discovery of fossils within the area.Noulet, J.B. (1870) – Du Chéropotame de Lautrec, espèce nouvelle des grès à Palaeotherium du bassin de l'Agout (Tarn). Mémoires de l'Académie des Sciences Inscription et Belles Lettre de Toulouse, 7e sér., t.. II, p. 331-335.

The Grès d'Issel Member was identified by Henri de Sévérac in 1873, and the Sables du Castrais Formation was first described by M. Richard in 1946.M. Richard. (1946). Contribution a l'étude du basin d'Aquitaine, Les Gisements de Mammiferes Tertiares. Memoires de la Societe Geologique de France, Nouvelle Serie 24(52):1-380

The Grès d'Issel Member is located in a quarry which closed around 1966 and is now inaccessible due to it currently being located underneath a private garden.

Age of the formation The age of the Sables du Castrais Formation was listed as Eocene by Noulet (1858) and in 1867, Gervais noted that the Issel Member likely dated to the Early Eocene, while the Villeneuve-la-Comptal Member likely dated to the Middle Eocene.Gervais P. (1867-69) – Zoologie et Paléontologie générales. Nouvelles recherches sur les Vertébrés vivants et fossiles. Paris, Arthus Bertrand, Editeur. 50 pl. The formation as a whole falls within the unit MP16 of the Mammal Paleogene zones stratigraphic range.

Caraven-Cachin (1898) was the first to assign the Sables du Castrais Formation to the Bartonian.Caraven-Cascin, A., (1898) – Description géographique, géologique, minéralogique, paléontologique, paléthnologique et agronomique des départements du Tarn et Tarn et Garonne. Privat, Toulouse & Masson, Paris, 1898, 684 p. Stehlin (1910) and Escarguel (1999) dated the formation to the Lutetian-Bartonian and found it to overlie the Molasses de Saix et de Lautrec Formation.Stehlin, H.G. (1910) – Die Säugetiere des schweitzerischen Eocaens. 6ème part. Mémoire de la Société Paléontologique suisse, t. XXXVI, p. 838-1164-258ESCARGUEL G. (1999) – Les rongeurs de l'Eocène inférieur et moyen d'Europe occidentale. Systématique, Phylogénie, biochronologie et paléobiogéographie des niveaux repères MP 7 à MP 14. Paleovertebrata, 28, n° 2-4, p. 89-351. Fauré (2011) agreed with the more recent dating of the formation to the Ypresian-Bartonian.

Geology The base of the Sables du Castrais Formation, which overlies Danian rocks, is made up of Ypresian gravel clays and the Issel Sandstones, which range from , and the Argiles rutilants d'Issel et de Saint-Papoul Member is deposited within the gravel clays, and is between thick.

The Argiles rutilants d'Issel et de Saint-Papoul Member is overlain by the Lutetian Grès d'Issel Member, which is between thick, and is overlain by the Bartonian Molasses du Castelnaudary Member.Cavaillé, A., Debat, P., Calas, G. (1975). Castelnaudary, notice explicative. Carte géologique de la France à 1/50 000. 1036, Orléans: BRGM, 17 pp.Adnet, S., Crochet, J-Y., Baillet, L. (2014). Gisement à vertébrés lutétiens d'Issel. Inventaire du patrimoine géologique du Languedoc-Roussilon, LRO-1104, DREAL Languedoc-Roussillon, 4 pp. The whole formation underlies the Molasses de Saix et de Lautrec Formation.

The Grès de Carcassonne Member also appears to be slightly younger than the Grès d'Issel Member, likely dating to the late Lutetian or early Bartonian.Depéret, C. (1921). Sur Un Petit Lophiodontidae (Lophiaspis Occitanicus Mutation Cesserasicus) Des Grès éocènes de Laure (Aude). Bulletin de La Société d'Etudes Scientifiques de l'Aude 27: 44–54.

The Sables du Castrais Formation was described by Capera and Baillet (2014) as a typical fluviatile formation, with lenticular channels, formed by conglomerates and sandstones, with calcareous cement and large trough cross-strata.Capera, J-C., Baillet, L. (2014). Carrière de grès éocènes de Carcassonne. Inventaire du patrimoine géologique du Languedoc-Roussilon, LRO-1052, DREAL Languedoc-Roussillon, 4 pp.

Paleofauna

Mammals Artiodactyl Taxa Species Locality Stratigraphic position Material Notes ImagesCatadontheriumC ? paquieriCebochoerusC.(Gervachoerus) campichiiC.(Cebochoerus) helveticus ChoeropotamusC. lautricensis Dacrytherium D. elegans Pseudoamphimeryx P. sp.RobiacinaR. minuta Tapirulus Tapirulus cf. schlosseri Xiphodon X. castrense Lipotyphia Taxa Species Locality Stratigraphic position Material Notes Images Saturninia S. sp. Marsupial Taxa Species Locality Stratigraphic position Material Notes Images Paratherium P. sp.

Pan-Carnivora Taxa Species Locality Stratigraphic position Material Notes ImagesHyaenodon H. nouleti H. spKerberosK. langebadreaeMontespieuMP16A partial skull with lower jaws, a fibula, and several lower limb bones Quercygale Q. angustidens

Perissodactyl Taxa Species Locality Stratigraphic position Material Notes Images AnchylophusA. cf. desmarestiA. cf. gaudini Eurohippus E. parvulus Lophiodon L. isselense. L. lautricense. L. sp. Plagiolophus P. cartailhaci P. cf. minor Leptolophus L. nouleti Lophiaspis L. occitanicus Paralophiodon P. isselensePalaeotherium P. castrense P. (Frantzenitherium) lautricense P. isselanum P. rhinocerodes P. siderolithicum P. pomeli Propalaeotherium P. sp.

Primates Taxa Species Locality Stratigraphic position Material Notes Images Adapis A. aff. parisiensis A. rouxii Necrolemur N. sp. Rodent Taxa Species Locality Stratigraphic position Material Notes Images Gliravus G. sp.Suevoscurius S. sp. Pseudoltinomys P. sp.

Reptiles Crocodilians Taxa Species Locality Stratigraphic position Material Notes Images Asiatosuchus A. depressifrons AtacisaurusA. glareaeA. cf. sp.CrocodylusC. rouxiiDentaneosuchusD. crassiproratus A mandibular symphysis. A giant sebecid crocodile. IberosuchusI. cf. macrodonKentisuchusK. astreiPristichampsusP. rollinati

Turtles Taxa Species Locality Stratigraphic position Material Notes ImagesAllaeochelysA. pareyreiA. nouletiA. castrensisHadrianusH. castrensisNeochelysN. mengautiN. sp.F. Lapparent de Broin. (2003). Neochelys sp. (Chelonii, Erymnochelyinae), from Silveirinha, early Eocene, Portugal. Ciencias da Terra (UNL) 15:117-132 TrionyxT. filholiT. sp.F. Broin. (1977). Contribution a l'etude des Cheloniens. Cheloniens continentaux due Cretace et du Tertiare de France. Memoires du Museum National d'Histoire Naturelle, Nouvelle Serie, Serie C, Sciences de la terre 38:1-366.

References