Rajasaurus

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Rajasaurus
Temporal range:
Ma
↓
Profile picture of the skull with the left side visible
Reconstructed skull, Regional Museum of Natural History, Bhopal
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family: †Abelisauridae
Subfamily: †Majungasaurinae
Genus: †Rajasaurus
Wilson et al., 2003
Species:
†R. narmadensis
Binomial name
†Rajasaurus narmadensis
Wilson et al., 2003

Rajasaurus (meaning "

braincase, spine, hip bone, legs, and tail–a first for an Indian theropod. The dinosaur likely measured 6.6 metres (22 ft), and had a single horn on the forehead which was probably used for display and head-butting. Like other abelisaurids, Rajasaurus was probably an ambush predator
.

India at this time was an island, due to the break-up of the

sauropods
, similar to other Gondwanan landmasses. The area during the Cretaceous was probably forested, and served as nesting grounds for several creatures.

Discovery and naming

A calm, blue river with forested banks visible on either side
The Narmada River, near which the remains of Rajasaurus were found

The Lameta Formation was first discovered in 1981 by geologists working for the Geological Survey of India (GSI), G. N. Dwivedi and Dhananjay Mahendrakumar Mohabey, after being given limestone structures–later recognised as dinosaur eggs–by workers of the ACC Cement Quarry in the village of Rahioli near the city Balasinor in the Gujarat state of western India. The remains of Rajasaurus were found in this fossil-rich limestone bed to which GSI geologist Suresh Srivastava was assigned to excavate on two separate trips from 1982–1983 and 1983–1984. In 2001, teams from the American Institute of Indian Studies and the National Geographic Society, with the support of the Panjab University, joined the study in order to reconstruct the excavated remains. Fragments of Rajasaurus were also found near Jabalpur in Madhya Pradesh in the northern part of the Lameta Formation, namely a piece of the upper jaw.[1] Rajasaurus was then formally described in 2003 by geologist Jeffrey A. Wilson and colleagues.[2]

The

synonymous, though this cannot be confirmed due to fragmentary remains, and the Lametasaurus specimen has been lost.[2][3]

The

generic name Rajasaurus derives from the Sanskrit rāja, meaning 'king, sovereign, chief, or best of its kind' and Ancient Greek sauros, meaning 'lizard'; and its specific name narmadensis refers to the Narmada River in central India near where it was discovered.[2]

Description

Scale diagram of Rajasaurus and a human

In 2010, palaeontologist

Lametasaurus have been suggested to belong to Rajasaurus, based on shared features in the ilium.[8] It also appears to be from a larger specimen than the holotype.[9]

Life restoration

On the braincase, only the left sides of the

otic capsule bone in the ear, more so juts outward as a stump.[2]

tibiae
; G is Rajasaurus

Rajasaurus had a low horn on its forehead that is primarily made of nasal bone more than frontal, unlike the horn on Majungasaurus. The horn in life was probably the same size as the fossilised horn, unlike in Carnotaurus where in life the horn was extended by a thickened layer skin. Though Rajasaurus did have a thickened layer of skin, it probably did not add to the overall length of the horn.[7] A trough-like groove bordered by a raised wall is present where the frontal meets the nasal, decreasing in height and width towards the midline, serving to support the horn on the nasal.[2]

Only one

tail vertebrae were found, likely from the middle-section of the tail, and they also have concave faces, but are more cylindrical than spool-shaped.[2][10]

The part of the hip that juts out to attach to the

pubic peduncle, which causes the hip-joint to be farther down on the back-underside of the hip. The iliac crests, on the other side of the hip from the ischium and pubic bone, are thin compared to the hip-joint area, 1 and 8 centimetres (0.39 and 3.15 in) respectively in thickness. The fibula, on the outside portion of the lower leg below the knee, decreases in width from top to bottom and is slightly concave. Similar to Ceratosaurus, the second metatarsal bone which connects the ankle bone to the second toe, is robust, has an oval-shaped and slightly concave joint between it and the ankle, and the width does not decrease as it gets nearer the toes. The fourth metatarsal bone has similar proportions to the second metatarsal. Both second metatarsals are preserved and only the left fourth metatarsal is preserved.[2]

Classification

Wilson, in 2003, assigned Rajasaurus to the subfamily

Middle Cretaceous.[3][12][13]

In 2014, the subfamily

island hopping and an indirect path to Asia, though these are still questionable explanations.[14][15]

The following cladogram was recovered by Tortosa (2014):[14]

Ceratosauria

Rajasaurus is distinguished from other genera by its single forehead horn (though Majungasaurus also only has one), the elongated supratemporal fenestrae (holes in the upper rear of the skull), and the ilia bones on the hip which feature a ridge separating the brevis shelf from the hip joint.[2]

Palaeobiology

Restoration of Rajasaurus with prey

The horn of Rajasaurus could have been used for

cancellous bone in the skull, could have been both or either low-motion shoving matches like modern day marine iguanas (Amblyrhynchus cristatus), or focused on the neck and the flank like giraffes (Giraffa spp.). The neck muscles, though, in abelisaurids were adapted for withstanding high stress. The horn could have been used for defending territory or for mating matches.[7]

Abelisaurids may have been ambush predators, using a bite-and-hold tactic to hunt large prey. The leg bones of Majungasaurus are comparatively short to other similarly-sized theropods, suggesting the dinosaur was comparatively slower–this same condition is seen in Rajasaurus. However, ceratosaurs may have been able to rapidly accelerate.[7][16]

Palaeoecology

India was an island in the Late Cretaceous

Rajasaurus has been found in the Lameta Formation, a rock unit

palm trees; early grass; and Caryophyllaceae, Sapindaceae, and Acanthaceae flowering plants.[21] The prehistoric snake Sanajeh mainly raided the nests of sauropods for eggs, though it is possible it also targeted smaller theropod eggs.[22]

Rajasaurus and other dinosaurs would have faced intense volcanism due to the Deccan Traps

India, by the Late Cretaceous, had separated from Madagascar and South America during the break-up of Gondwana, and Rajasaurus lived on an isolated island, likely causing

egg taxa suggests an inter-continental migration of animals between India, Europe, and South America during the Cretaceous, despite water barriers.[25]

Several dinosaurs have been described from the Lameta Formation, such as the

titanosaurian sauropods Jainosaurus, Titanosaurus, and Isisaurus. The diversity of abelisauroid and titanosaurian dinosaurs in Cretaceous India indicates they shared close affinities to the dinosaur life of the other Gondwanan continents, which had similar inhabitants.[2][26]

The dinosaurs in India probably all went extinct due to volcanic activity around 350,000 years before the

lava flows.[relevant?][27]

Cultural significance

The Gujarat state has declared the fossil site in Balasinor a "dinosaur park," sometimes called the "Jurassic Park of India" in reference to the

Adlabs Imagica features the Rajasaurus River Adventure, a water ride following the fictional "Dr. Roy" through prehistoric times.[30] Rajasaurus also appeared in the "Badlands" episode of Prehistoric Planet, where at least two individuals are shown hunting down Isisaurus hatchlings as they pass through the volcanic fields of the Deccan Traps
.

See also

References

  1. ^ a b c "Rajasaurus narmadensis – India's own dinosaur emerges from oblivion" (PDF). Geological Survey of India. Archived from the original (PDF) on 28 May 2008. Retrieved 8 April 2009.
  2. ^ a b c d e f g h i j k Wilson, J. A.; Sereno, P. C.; Srivastava, S.; Bhatt, D. K.; Khosla, A.; Sahni, A. (2003). "A new abelisaurid (Dinosauria, Theropoda) from the Lameta Formation (Cretaceous, Maastrichtian) of India" (PDF). Contributions from the Museum of Paleontology University of Michigan. 31 (1): 1–42.
  3. ^
    S2CID 30068953. Archived from the original
    (PDF) on 22 May 2018.
  4. ^
    ISBN 978-0-691-13720-9
    .
  5. doi:10.1016/j.cretres.2016.09.001
    .
  6. S2CID 130262308
    .
  7. ^
    PMID 29950661
    .
  8. ^ J.A. Wilson, P.C. Sereno, S. Srivastava, D.K. Bhatt, A. Khosla and A. Sahni, 2003, "A new abelisaurid (Dinosauria, Theropoda) from the Lameta Formation (Cretaceous, Maastrichtian) of India", Contributions from the Museum of Paleontology, University of Michigan 31(1): 1-42
  9. ISBN 978-0-691-18031-1
    .
  10. S2CID 129240095
    .
  11. ^ Mathur, U. B. ubmathur (2004). "Rajasaurus narmadaensis" (PDF). Current Science. 86 (6).
  12. S2CID 13345182
    .
  13. PMID 15306329
    .
  14. ^
    doi:10.1016/j.annpal.2013.10.003
    .
  15. ^ Kapur, V. V.; Khosla, A. (2016). "Late Cretaceous terrestrial biota from India with special reference to vertebrates and their implications for biogeographic connections". Cretaceous Period: Biotic Diversity and Biogeography. 71: 161–172.
  16. PMID 22043292
    .
  17. doi:10.1016/0195-6671(87)90008-5
    .
  18. ^ Mohabey, D. M. (1996). "Depositional environment of Lameta Formation (late Cretaceous) of Nand-Dongargaon inland basin, Maharashtra: the fossil and lithological evidences". Memoirs of the Geological Survey of India. 37: 1–36.
  19. doi:10.1016/0031-0182(94)00128-U
    .
  20. ^ Lovgren, S. (13 August 2003). "New Dinosaur Species Found in India". National Geographic News. Archived from the original on 11 December 2003. Retrieved 8 April 2009.
  21. S2CID 135418472
    .
  22. PMID 20209142
    .
  23. ^ "Rajasaurus narmadensis – A new Indian dinosaur" (PDF). Current Science. Vol. 85, no. 12. 2003. p. 1661.
  24. S2CID 83532299
    .
  25. S2CID 86208659
    .
  26. ISBN 978-0-520-24209-8
    .
  27. ^ Mohabey, D. M.; Samant, B. (2013). "Deccan continental flood basalt eruption terminated Indian dinosaurs before the Cretaceous–Paleogene boundary". Geological Society of India Special Publication (1): 260–267.
  28. ^ "The dinosaur wonders of India's Jurassic Park". BBC News. 11 May 2010. Retrieved 23 July 2018.
  29. ^ Bhattacharya, S. (16 January 2013). "India's Jurassic Park hopes 'princely lizards' will attract tourists". The National. Retrieved 23 July 2018.
  30. ^ "Rajasaurus River Adventure". imagica. Archived from the original on 23 July 2018. Retrieved 23 July 2018.

External links

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