Cerin Lagerstätte

The site belonging to the Bugey historical region was erected at 560 meters above the sea level and is located 20 km off Belley, 75 km off Lyon, 80 km off Grenoble and 90 km off Geneva.^[4]

Cerin was reputed by the end of the 19th century for the quality of its lithographic limestone. The area was, during the Late Jurassic, a tropical lagoon. Lithographic limestone is formed by sedimentation of a very thin carbonated mud deposited at the bottom of a lagoon 153 million of years ago. Those deposits are disposed in strata.

The quarry exploitation, which began in 1835 during the lithography golden age, allowed to periodically uncover prints of prehistoric animals and plants fossilized in stone. Paleontology was at its beginning and those discoveries were still little-known.^[3]

In 1838, thanks to the engineer Aimé Drian, a passionate amateur geologist, and Lyonese geologist, and Victor Thiollière, those fossils were discovered and the existence of the paleontological site of Cerin was revealed to the scientific world. The site has an international reputation and rivals with the Solnhofen Limestone, in Bavaria. Until his death, Victor Thiollière never ceased to collect and study a maximum of fossils from the site, and it was, in large part, thanks to his study of the Cerin fossils that he was recognized in the palaeontology world.

His works showed the similarities of the lithographic limestones of Cerin and Solnhofen. He described several new species of fish. He published in 1854 the first part of his "Description des poissons fossiles provenant des gisements coralliens du Jura dans le Bugey" ("Description of the fossil fish from the Jura corallian deposits in the Bugey"), but died shortly before the publication of the second part, the descriptions and lithographic plates already finished.^[5]

Research on the Late Kimmeridgian site (Late Jurassic, around −153 Ma),^[6] occurred from 1975 to 1995, it was a unique operation and involved advanced technology. Directed by geologists from Claude Bernard University in Lyon, it necessitated heavy equipment of civil engineering.

This operation allowed the discovery of algae, ferns, conifers, molluscs, sea urchins, starfish, crustaceans such as the holotypes of Cyclerion bourseaui and Soleryon amicalis,^[7] reptiles, fish, as well as tracks of turtles and other reptiles.^[8] A thorough study permitted to determine the age and nature of the site (a tropical lagoon 153 million years old) and to understand the reasons of this exceptional fossilization.^[1]

A one-of-a-kind Late Jurassic fossilized track of prehistoric marine turtle was discovered in Cerin.

To understand the fossilization process in Cerin, scientists went on an expedition to Aldabra in the Indian Ocean, to observe a fossilization process similar to the one that happened on the Cerin site.

153 million years ago, the climate was tropical. The lagoon had only few contacts with the open sea, and evaporation was intense. Terrestrial animals venturing in the lagoon shores left their tracks in a quickly drying mud.

During storms, a large quantity of saltwater, carrying mud, vegetal remains, and dead or alive animals, entered the lagoon; clearwater, brought by rains and water runoff, brought as well large quantities of particulate matters. When the calm was settling, the fine particles deposited in a regular layer which carpeted the depths and covered remains and tracks.

This layer gave then birth to a strata of lithographic limestone.

When evaporation made the water level drop again, it became under oxygenated and over-concentrated on salt, which led to the death of many living beings, while protecting their bodies from scavengers. The microbial mats, who thrived in this environment, covered the corpses and vegetal remains, helping their conservation as fossils.^[1]

• 
  Ophiopsis guigardi
• 
  Thrissops henkeli
• 
  Orthocormus teyleri
• 
  Macrosemius dumortieri
• 
  Notagogus cf. imimontis

Algae^[9]

More information Genus, Species ...

Genus	Species	Classification	Note	Picture
Campbelliella	C. striata	Dasycladales
Clypeina	C. jurassica	Dasycladales	Clusters of this species attain more than 10 cm.
Goniolina	G. janeti	Dasycladales

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Plants^[9][10]

More information Genus, Species ...

Genus	Species	Classification	Note	Picture
Apoldia	A. latifolia	Cycadales
Brachyphyllum
	B. desnoyersii	Pinales
	B. elegans	Pinales
	B. speciosa	Pinales
Crossozamia[11]		Cycadopsida	Formerly described as Cycalacis.
Cupressinoxylon	C. sp	Coniferales
Cycadopteris	C. jurensis	Pteridospermatophyta
Pachypteris		Pteridospermatophyta
Pagiophyllum	P. cirinicum	Araucariaceae
Zamites	Z. feneonis	Bennettitales	Very abundant in the site.
Z. pumilio	Bennettitales

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Cnidarians^[12]

Lophotrochozoans^[13][9]

More information Genus, Species ...

Genus	Species	Classification	Note	Picture
Aspidoceras	A. cf. catalaunicum	Aspidoceratidae
Hibolites		Belemnoidea
Laevaptychus[14]	L. latus		A kind of Aptychus. Formerly referred as Aptychus latus.
Lithacoceras	L. cf. ulmense	Ataxioceratidae
	L. sp. gr. siliceus	Ataxioceratidae
	L. sp	Ataxioceratidae	Potentially a new species.
Nanogyra[15]	N. virgula	Bivalvia
Nerinea[15]	N. suprajurensis	Gastropoda
Rhynchonellida		Rhynchonellida
Subplanites	S. cf. rueppellianus	Perisphinctidae
Terebratulidae		Terebratulidae

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Arthropods^[9][16]

More information Genus, Species ...

Genus	Species	Classification	Note	Picture
Antrimpos	A. speciosus	Penaeidae
Cycleryon	C. bourseaui[7]	Eryonidae
	C. propinquus	Eryonidae
Dusa	D. monocera	Penaeidae	Its presence at Cerin might be a mistake caused by confusion due to misattribution of specimens hailing from the Solnhofen Limestone.
Eryma	E. modestiformis	Erymidae
Eryon	E. arctiformis	Eryonidae	Its presence at Cerin might be a mistake caused by confusion due to misattribution of specimens hailing from the Solnhofen Limestone.
Gigacerina	G. saemanni	Glypheoidea	One of the largest known glypheids. Formerly referred to as Glyphea saemanni.
Glyphea	G. pseudoscyllarus	Glypheoidea	Macrourites cerensis is a synonym.
Mecochirus	M. brevimanus	Glypheoidea	Its presence at Cerin might be a mistake caused by confusion due to misattribution of specimens hailing from the Solnhofen Limestone. This species is also considered a synonym of M. longimanatus, likely to represent a female morphotype.[17]
	M. sp	Glypheoidea
Mesolimulus	M. walchi	Limulidae
Soleryon [7]	S. amicalis	Eryonidae

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Echinoderms^[9][18][19]

More information Genus, Species ...

Genus	Species	Classification	Note	Picture
Acrocidaris[15]	A. nobilis	Euechinoidea
?Ceramaster	? C. chantrei	Goniasteridae
Cidaris[15]	C. carinifera	Cidaroida
Comptoniaster	C. meyeri	Goniasteridae
Ophiopetra	O. lithographica	Aplocomidae
Pentasteria	P. lithographica	Astropectinidae
Pseudodiadema	P. cf. pseudodiadema	Pseudodiadematidae
Pygurus		Clypeidae
Solanocrinites	S. thiollieri	Crinoidea

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Chondrichthyes^[20]

More information Genus, Species ...

Genus	Species	Classification	Note	Picture
Belemnobatis	B. sismondae	Asterodermidae
Corysodon	C. cirinensis	Carcharhiniformes	The genus Corysodon has been synonymized with Palaeoscyllium by Cappetta, 1987. However the validity of Corysodon was maintained by Thies & Candoni, 1998[21], this was related by later studies.
Phorcynis	P. catulina	Squatiniformes
Spathobatis	S. bugesiacus	Asterodermidae

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Sarcopterygians^[20]

Actinopterygians^[20]

More information Genus, Species ...

Genus	Species	Classification	Note	Picture
Ainia	A. armata[23]	Halecomorphi
Allothrissops	A. regleyi	Ichthyodectiformes	Formerly placed in the genus Thrissops.
Amblysemius[24]	A. bellicianus	Caturidae
Anaethalion	A. affinis	Elopiformes
	A. cirinensis	Elopiformes
	A. knorri	Elopiformes
	A. cf. subovatus	Elopiformes
Ankylophorus	A. similis	Ankylophoridae	Formerly placed in the genus Pholidophorus.
Apomesodon[25]	A. comosus	Pycnodontiformes	Synonym of A. gibbosus.
	A. gibbosus	Pycnodontiformes	Formerly referred to as Eomesodon gibbosus.[26]
	A. surgens	Pycnodontiformes	Synonym of A. gibbosus.
Aspidorhynchus[27]	A. acutirostris	Aspidorhynchidae
Belonostomus	B. tenuirostris	Aspidorhynchidae	Some authors are more prudent about the identification of this species as B. tenuirostris.[28]
	B. sp.[28]	Aspidorhynchidae	At least one more species is present in Cerin, it is similar to B. kochii.
Caturus	C. furcatus	Caturidae
Cerinichthys[29]	C. koelblae	Halecomorphi
Eoprotelops	E. vireti	Elopiformes
Gyrodus	"G". hexagonus[30]	Pycnodontiformes	The specimens from Cerin probably belong to a more derived pycnodontiform, it might not be the same species as Gyrodus hexagonus.
	G. sp.	Pycnodontiformes	Specimens from Cerin were formerly referred to as Mesturus verrucosus.[25]
Ionoscopus	I. desori	Amiiformes
Lehmanophorus[31]	L. segusianus	Ankylophoridae	Formerly referred to as Pholidophorus segusianus.
Leptolepides[32]	L. sp.	Orthogonikleithridae	There might be more than one species present in Cerin.
Macromesodon[33]	M. macropterus	Pycnodontiformes	Formerly referred to as Coelodus jourdani, which is now considered a junior synonym.
Macrosemius	M. fourneti	Macrosemiidae
Notagogus	N. helenae	Macrosemiidae
	N. inimontis	Macrosemiidae
Oligopleurus	O. esocinus[29]	Halecomorphi
Ophiopsiella[34]	O. guigardi	Halecomorphi	Formerly referred to as Ophiopsis guigardi.
	O. macrodus	Halecomorphi	Formerly referred to as Ophiopsis macrodus.
	O. procera	Halecomorphi	Specimens from Cerin were formerly referred to as Ophiopsis attenuata.
Ophiopsis[34]	O. muensteri	Ionoscopiformes	The occurrence from Cerin was formerly described as Furo praelongus. However, this species has been synomymized with Furo muensteri.[35] This species was moved to the genus Ophiopsis after a taxonomic reassessment.
Orthocormus	O. teyleri	Pachycormiformes
Orthogonikleithrus[32]	O. francogalliensis	Orthogonikleithridae	Specimens previously assigned to Leptolepides sprattiformis belong to this species.
	O. sp.	Orthogonikleithridae	There is at least one more species of Orthogonikleithrus. Specimens previously referred to Ascalabos voithi actually belong to O. sp.[36]
Palaeomacrosemius[37]	P. thiollieri	Macrosemiidae
Pholidophorichthys	P. inermis	Pholidophoridae
Pholidophoristion	P. cf. ovatus	Pholidophoridae
"Pholidophorus"[24]	"P". velifer	Caturidae	Formerly known as Caturus velifer, it surely does not belong to Caturus. Its taxonomic statue is still unclear and is being studied.
Pleuropholis	P. thiolleri	Pleuropholidae
Propterus	P. microstomus	Semionotiformes	Material from Cerin was previously described as Histionotus falsani. This species was later regarded as a synonym of Histionotus oberndorferi, itself synonymized with Propterus microstomus.[38]
Proscinetes[39]	P. bernardi	Pycnodontiformes
	P. distantidens	Pycnodontiformes
	P. elegans	Pycnodontiformes
	P. intermedius	Pycnodontiformes
	P. itieri	Pycnodontiformes
	P. sauvanausi	Pycnodontiformes
	P. thiolleri	Pycnodontiformes
Scheenstia[40]	S. laevis	Lepisosteiformes	Formerly referred to as Lepidotes laevis.
Solnhofenamia[29]	S. elongata	Amiidae	Formerly placed in the genus Urocles as U. elongatus.[41]
Tharsis	T. dubius	Ascalaboidiformes
Thiollierepycnodus[42]	T. wagneri	Pycnodontiformes	Formerly referred to as Gyrodus wagneri.
Thrissops[43]	T. cirinensis	Ichthyodectiformes
	T. formosus	Ichthyodectiformes
Turboscinetes[44]	T. egertoni	Pycnodontiformes	Formerly referred to as Proscinetes egertoni.

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Reptiles^[45][46]

More information Genus, Species ...

Genus	Species	Classification	Note	Picture
Achelonia	A. formosa	Eurysternidae
Alligatorellus	A. beaumonti	Atoposauridae
Alligatorium	A. meyeri	Atoposauridae
Atoposaurus	A. jourdani	Atoposauridae
Crocodilaemus	C. robustus	Pholidosauridae	Sometimes orthographied Crocodileimus.
Euposaurus[47]	E. cirinensis	Rhynchocephalia	Sometimes orthographied as E. cerinensis. This species certainly does not belong to Euposaurus.
	E. lorteti	Rhynchocephalia	This species certainly does not belong to Euposaurus.
	E. thiollierei	Lepidosauromorpha	Sometimes orthographied as E. thiollieri. This species is known from a single young individual and might be a lizard.
Gavialinum	G. rhodani	Teleosauroidea	This species is now regarded as a nomen dubium.
Homoeosaurus	H. jourdani	Rhynchocephalia	Synonym of H. maximiliani.
	H. maximiliani	Rhynchocephalia
	H. rhodani	Rhynchocephalia
Hydropelta	H. meyeri	Eurysternidae
Idiochelys	I. fitzingeri	Eurysternidae
Kallimodon	K. cerinensis	Rhynchocephalia
	K. pulchellus	Rhynchocephalia
Piocormus	P. cf. laticeps	Rhynchocephalia	Some authors have argued that Piocormus might be the same as Sapheosaurus.[47]
Pleurosaurus	P. goldfussi	Pleurosauridae	A rhynchocephalian particularly well adapted to an aquatic lifestyle.
Pterodactylus	P. cirinensis	Pterosauria	Now considered an indeterminate pterosaur.
Sapheosaurus	S. thiollierei	Rhynchocephalia
Stelliosaurus			This genus is old (Gervais, 1871) and poorly documented, for those reasons, it is considered a nomen nudum and might instead be considered a synonym of Homoeosaurus.

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• The Musée des Confluences showcases 24 fossils from Cerin, some of them found by Victor Thiollière;
• The Musée paléoécologique de Cerin;
• The Museum of Natural Sciences showcases casts of fossils from the site of Cerin.des moulages de fossiles issus du site de Cerin;
• The Teylers Museum in Haarlem (Netherlands) showcases fossils from Cerin.

• Solnhofen Limestone
• Canjuers Lagerstätte
• Mörnsheim Formation