Jaisalmer Formation
Geologic formation in India
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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, | |
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 |
| 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
|
Notes Uncertain or tentative taxa are in small text; |
Dinosaurs
Sauropods
| Sauropods of the Jaisalmer Formation | |||||
|---|---|---|---|---|---|
| Genus | Species | Locality | Material | Notes | Photos |
| Turiasauria indet.[6] | Indeterminate | Chandoo Village quarry | Fragmentary tooth | A turiasaur | |
| Tharosaurus[8] | T. indicus | Jethwai Village | RWR-241 (A–K), partial cervical, dorsal, and caudal vertebrae and a dorsal rib | A potentially dubious eusauropod |
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Theropods
| Theropods of the Jaisalmer Formation | |||||
|---|---|---|---|---|---|
| Genus | Species | Locality | Material | Notes | Photos |
| Spinosauridae indet.[9] | Indeterminate | Chandoo Village quarry | RAJ/JAIS/CVQS002, pedal ungual phalanx | Possibly the oldest spinosaurid |  |
| Averostra indet.[10] | Indeterminate | Chandoo 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[11] | Cf. T. cadomensis | Chandoo 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[11] | Indeterminate | Chandoo 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 cryptoclidid | |
| Teleosauridae[11] | Indeterminate | Chandoo Village quarry | RAJ/JAIS/002, a tooth that is robust, conical and single-cusped | An indeterminate teleosaurid | |
| Machimosauridae[11] | Indeterminate | Chandoo Village quarry | RAJ/JAIS/005, a single tooth that is large, single cusped and conical. | A indeterminate machimosaurid | |
| Metriorhynchoidea[11] | Indeterminate | Chandoo Village quarry | RAJ/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.[12] | Indeterminate | ||||
| Strophodus | S. jaisalmerensis | Jethwai village | Teeth | A hybodont shark | |
| S. indicus[13] | Chandoo Village quarry | ||||
| S. magnus[13] | Chandoo Village quarry | ||||
| S. medius[13] | Chandoo Village quarry | ||||
| Planohybodus | P. aff. grossiconus [13] | Chandoo Village quarry | Teeth | A hybodont shark | |
| Osteichthyes indet.[10] | Indeterminate | Chandoo Village quarry | Teeth and scale | Found along with an averostran tooth | |
| Eomesodon[14][15] | E. 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[16] | C. indica | ||||
| Micropneumatocythere[16] | M. joyanensis | ||||
| Progonocythere[16] | P. khoslai | ||||
| Trichordis[16] | T. minuta | ||||
Ichnofossils
- ?Bichordites sp. – Ichnofossils[17]
- Planolites sp. – Ichnofossils[17]
- Rhizocorallium irregulare – Ichnofossils[17]
- Rhizocorallium jenense – Ichnofossils[17]
- Taenidium serpentinum – Ichnofossils[17]
- Thalassinoides sp. – Ichnofossils[17]