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. The formation was first identified and defined by geologist Richard Dixon Oldham in 1886.
Dinosaur remains are among the known fossils recovered from this formation.Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, Asia)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 593–600. .
Strophodus jaisalmerensis, a hybodont, was named after this formation and the Jaisalmer District where its holotype was found.
Sub-units The Badabag, Fort, Joyan and Hamira members represent the Middle Jurassic Bajocian and Bathonian stages, while the Jajiya and Kuldhar members represent the Middle Jurassic Callovian and the Late Jurassic Oxfordian stages.
The Fort Member is the most extensively studied and consists of fine to medium grain sandstones and oolitic limestones.Narayanan, K., Subrahmanyan, M., Srinivasan, S., (1961). Geology of Jaisalmer. Unpublished report, Oil and Natural Gas Corporation Dehradun, India. The Badabag Member consists of intraformational conglomerate and is fossil bearing.
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. The Kuldhar Member Limestone contained carbonate microfacies that also indicate a depositional environment composed mainly of lagoons, shoals and open marine environments.
Paleofauna
Dinosaurs
Sauropods Sauropods of the Jaisalmer Formation Genus Species Locality Material Notes PhotosTuriasauria indet. IndeterminateChandoo Village quarry Fragmentary tooth A turiasaur Tharosaurus T. indicusJethwai Village RWR-241 (A–K), partial cervical, dorsal, and caudal vertebrae and a dorsal rib A potentially dubious eusauropod
Theropods Theropods of the Jaisalmer Formation Genus Species Locality Material Notes Photos Spinosauridae indet.IndeterminateChandoo Village quarry RAJ/JAIS/CVQS002, pedal ungual phalanx Possibly the oldest spinosaurid Averostra indet. IndeterminateChandoo Village quarry RAJ/JAIS/JWGQ001, an isolated tooth.A possible allosauroid, ceratosaur, or non-spinosaurid megalosauroid
Other reptiles Other reptiles of the Jaisalmer Formation Genus Species Locality Material Notes Photos Cf. Teleosaurus Cf. T. cadomensisChandoo Village quarry RAJ/JAIS/015, a single isolated osteoderm of 6 cm in length and 5.5 cm in width, the osteoderm has randomly arranged and separated elliptical pits.A teleosaurid thalattosuchian Plesiosauria IndeterminateChandoo Village quarry RAJ/JAIS/009-010, two teeth that are single-cusped, lingually curved and slender, they're similar to the gracile teeth of Cryptoclidus. A plesiosaur. Described as a plesiosaurid but the teeth are similar to Cryptoclidus, a cryptoclididTeleosauridaeIndeterminateChandoo Village quarryRAJ/JAIS/002, a tooth that is robust, conical and single-cuspedAn indeterminate teleosauridMachimosauridaeIndeterminateChandoo Village quarryRAJ/JAIS/005, a single tooth that is large, single cusped and conical.A indeterminate machimosauridMetriorhynchoideaIndeterminateChandoo Village quarryRAJ/JAIS/006, a single moderately largest tooth that is lingually curved and mediolateral compressed.A indeterminate metriorhynchoid
Fish Fishes of the Jaisalmer Formation Genus Species Locality Material Notes Photos Hybodontiformes indet. IndeterminateStrophodus S. jaisalmerensisJethwai village Teeth A hybodont sharkS. indicusChandoo Village quarry S. magnusChandoo Village quarryS. mediusChandoo Village quarry Planohybodus P. aff. grossiconus Chandoo Village quarryTeethA hybodont sharkOsteichthyes indet.IndeterminateChandoo Village quarryTeeth and scaleFound along with an averostran toothEomesodonE. sp.Jethwai VillagePrearticular dental plate and isolated teethOldest east gondwanan pycnodont
Crustaceans Crustaceans of the Jaisalmer Formation Genus Species Locality Material Notes PhotosCytherellaC. indicaMicropneumatocythereM. joyanensisProgonocythereP. khoslaiTrichordisT. minuta
Ichnofossils ?Bichordites sp. – IchnofossilsKulkarni, K.G., Borkar, V.D., Petare, T.J., (2008). Ichnofossils from the Fort Member (Middle Jurassic), Jaisalmer Formation, Rajasthan. Journal of the Geological Society of India, 71, 731-738 Planolites sp. – Ichnofossils Rhizocorallium irregulare – Ichnofossils Rhizocorallium jenense – Ichnofossils Taenidium serpentinum – Ichnofossils Thalassinoides sp. – Ichnofossils
References