Jaisalmer Formation

The Jaisalmer Formation is a Middle to Late Jurassic-aged geologic formation located in India near the city of Jaisalmer that consists mainly of marine deposits.^[2] The formation was first identified and defined by geologist Richard Dixon Oldham in 1886.^[1]

Jaisalmer Formation
Stratigraphic range: Middle-Late Jurassic, Bajocian–Oxfordian PreꞒ Ꞓ O S D C P T J K Pg N
An outcrop of the Jaisalmer Formation which is the type locality for Tharosaurus indicus. Photographed between 2019-21.
Type	Geological formation
Sub-units	Badabag Member, Fort Member, Hamira Member, Jajiya Member, Joyan Member, Kuldhar Member
Underlies	Baisakhi Formation
Overlies	Lathi Formation
Thickness	Variable, typically 120–170 km (75–106 mi)
Lithology
Primary	Siltstone, sandstone
Other	Limestone
Location
Coordinates	26.911661°N 70.922928°E / 26.911661; 70.922928
Country	India
Extent	Jaisalmer
Type section
Named for	Jaisalmer, India
Named by	Richard Dixon Oldham
Year defined	1886[1]

Dinosaur remains are among the known fossils recovered from this formation.^[3]

Strophodus jaisalmerensis, a hybodont, was named after this formation and the Jaisalmer District where its holotype was found.^[4]

Sub-units

The Badabag, Fort, Joyan and Hamira members represent the Middle Jurassic Bajocian and Bathonian stages,^[2] while the Jajiya and Kuldhar members represent the Middle Jurassic Callovian and the Late Jurassic Oxfordian stages.^[2]

The Fort Member is the most extensively studied and consists of fine to medium grain sandstones and oolitic limestones.^[5] The Badabag Member consists of intraformational conglomerate and is fossil bearing.^[6]

Paleoenvironment

The Jaisalmer district of India is a landlocked district in the state of Rajasthan. However, during the Middle Jurassic, the Jaisalmer Formation was located on the Tethyan coast of Gondwanan India. A marine paleoenvironment is supported by the presence of Hybodont sharks.^[4] The Kuldhar Member Limestone contained carbonate microfacies that also indicate a depositional environment composed mainly of lagoons, shoals and open marine environments.^[7]

Paleofauna

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Dinosaurs

Sauropods

Sauropods of the Jaisalmer Formation
Genus	Species	Locality	Material	Notes	Photos
Turiasauria[6]	indeterminate	Chandoo Village quarry	Fragmentary tooth.	The oldest turiasaur.
Tharosaurus[8]	T. indicus	Jethwai Village	Partial cervical, dorsal, and caudal vertebrae and a dorsal rib.	Oldest dicraeosaurid and oldest diplodocoid.

Theropods

Theropods of the Jaisalmer Formation
Genus	Species	Locality	Material	Notes	Photos
Spinosauridae[9]	Indeterminate	Chandoo Village quarry	Pedal ungual phalanx.	Possibly the oldest spinosaurid. Had affinities with spinosaurinae.	Specimen RAJ/JAIS/CVQS002
Averostra[10]	indeterminate	Chandoo Village quarry	Isolated tooth.	A possible Ceratosaur or a Non Spinosaurid Megalosauroid or a Allosauroid.

Other Reptiles

Reptiles of the Jaisalmer Formation
Genus	Species	Locality	Material	Notes	Photos
Crocodylomorpha[6]	Indeterminate	Chandoo Village quarry	Scutes.
Neodiapsida[6][10]	Indeterminate	Chandoo Village quarry	Teeth.	Either a sauropterygian, thalattosaurian, choristodere or an ichthyosauromorph.

Fish

Fishes of the Jaisalmer Formation
Genus	Species	Locality	Material	Notes	Photos
Hybodontiformes Indet.[11]	Indeterminate
Strophodus	S. jaisalmerensis	Jethwai village	Teeth.	A hybodont shark.
	S. indicus[12]	Chandoo Village quarry
	S. magnus[12]	Chandoo Village quarry
	S. medius[12]	Chandoo Village quarry
Planohybodus	P. aff. grossiconus [12]	Chandoo Village quarry	Teeth.	A hybodont shark.
Osteichthyes[10]	Indeterminate.	Chandoo Village quarry	Teeth and scales.	Found along with an averostran tooth.
cf. Eomesodon[13]	cf. Eomesodon sp.	Jethwai Village	Prearticular dental plate and isolated teeth.	Oldest East Gondwanan Pycnodont.

Crustaceans

Crustaceans of the Jaisalmer Formation
Genus	Species	Locality	Material	Notes	Photos
Cytherella[14]	C. indica
Micropneumatocythere[14]	M. joyanensis
Progonocythere[14]	P. khoslai
Trichordis[14]	T. minuta

Ichnofossils

• (?)Bichordites sp. – "Ichnofossils"^[15]
• Planolites .sp – "Ichnofossils"^[15]
• Rhizocorallium irregulare – "Ichnofossils"^[15]
• Rhizocorallium jenense – "Ichnofossils"^[15]
• Taenidium serpentinum – "Ichnofossils"^[15]
• Thalassinoides .sp – "Ichnofossils"^[15]