| Rahiolisaurus | |
|---|---|
 | |
| Life restoration ofRahiolisaurus gujaratensis | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Abelisauridae |
| Subfamily: | †Carnotaurinae |
| Genus: | †Rahiolisaurus Novaset al.,2010 |
| Species: | †R. gujaratensis |
| Binomial name | |
| †Rahiolisaurus gujaratensis | |
Rahiolisaurus is agenus ofabelisauridtheropoddinosaur which existed inIndia during theLate Cretaceous period. It was described in2010, based on fossils recovered from theLameta Formation in the Indian state ofGujarat. These fossils include elements from at least seven different individuals and are believed to have been from theMaastrichtian stage, sometime between 70 and 66 million years ago, making it one of the last non-avian dinosaurs known in the fossil record. Despite representing a variety of different growth stages, all recovered fossils from the locality indicate a single species, thetype speciesRahiolisaurus gujaratensis.
During two expeditions, one in 1995 and the other in 1997, numerous remains of abelisaurids were recovered from a single quarry 50 square metres in area. The collected remains included cervical, dorsal, sacral, and caudal vertebrae, portions of pectoral and pelvic girdles, and several hind limb bones. Because of the unearthing of seven differently sized right tibiae, it was suggested that the assemblage was formed by at least seven individuals of different ontogenetic stages. Within the collection were several duplicate bones, such as the ilia, pubes, femora and tibiae, that exhibited similar morphological features of typical abelisauroid traits. However, despite these remains being of different size gradation and representing growth series, hardly any taxonomic variation was discovered. It was interpreted by Novas et al. that the entire theropod collection from this quarry may be referred to the single speciesRahiolisaurus.[1]
Individual bones of the newly discovered abelisaurid was given separate catalogue numbers. Theholotype ofRahiolisaurus is represented by a partial association of pelvic elements and a femur that were found in the field. It consists of a right ilium (ISIR 550), a right pubis (ISIR 554), and a right femur (ISIR 557). In addition, an axis (ISIR 658) was found in articulation with cervicals 3 (ISIR 659) and 4 (ISIR 660) and are attributed to the species. These bones are currently housed at the collection of the Geology Museum,Indian Statistical Institute, Kolkata.[1]
Rahiolisaurus was named after the village of Rahioli, located near the fossil site where the dinosaurs remains were discovered. The specific name,gujaratensis, means "fromGujarat" in Latin.[1]
Rahiolisaurus was initially described as a large-sized abelisaurid and around 8 metres (26 ft) long and weighing 2 metric tons (2.2 short tons),[1][2] but the allometry-based estimate for different specimens suggest a shorter body length of 6.22–6.75 metres (20.4–22.1 ft).[3] It shares many similarities with another Indian abelisaurid,Rajasaurus, but includes differences such as an overall more gracile and slender-limbed form.[1] Abelisaurids typically had four fingers, short arms, and, to compensate, a heavily constructed head which was the primary tool for hunting; however, the skull was short, they probably had modest jaw musculature, and the teeth were short.[2] Abelisaurids likely had a bite force similar toAllosaurus at around 3,500 newtons (790 lbf).[4]
In 2014, the subfamilyMajungasaurinae was erected by palaeontologist Thierry Tortosa to separate the newly discovered EuropeanArcovenator,Majungasaurus,Indosaurus,Rahiolisaurus, andRajasaurus from South American abelisaurids based on physical characteristics such as elongatedantorbital fenestrae in front of the eye sockets, and a sagittal crest that widens into a triangular surface towards the front of the head. In more recent analyses Rahiolisaurus as appeared as being more closely related to the South American abelisaurids, further strengthening the faunal similarities between India and South America in themesozoic.
The following cladogram was recovered by Tortosa (2014):[5]
A phylogeny from 2018 recoveredRahiolisaurus as forming a clade with the Madagascan abelisauridDahalokely within majungasaurinae.[6] Only the phylogenies for Abelisauridae is depicted here.
In 2021,Rahiolisaurus andDahalokely were again recovered as sister taxa, however they were placed outside of majungasaurinae as basalbrachyrostrans.[7]
Rahiolisaurus has been found in theLameta Formation, a rock unitradiometrically dated to theMaastrichtianage of the latest Cretaceous representing anarid orsemi-arid landscape with a river flowing through it–probably providing shrub cover near the water–which formed between episodes of volcanism in theDeccan Traps.[8][9]Rahiolisaurus likely inhabited what is now the Narmada River Valley. The formation is known for being a sauropod nesting site, yielding several dinosaur eggs, and sauropod herds likely chose sandy soil for nesting;[10] though eggs belonging to large theropods have been found, it is unknown if they belong toRahiolisaurus.[11] Sauropodcoprolite remains indicate they lived in a forested landscape, consuming plants such asPodocarpus,Araucaria, andCheirolepidiaceaeconifers;cycads;palm trees; earlygrass; andCaryophyllaceae,Sapindaceae, andAcanthaceae flowering plants.[12]
Several dinosaurs have been described from theLameta Formation, such as thenoasauridLaevisuchus; abelisauridsIndosaurus,Indosuchus,Lametasaurus, andRajasaurus; and thetitanosaurian sauropodsJainosaurus,Titanosaurus, andIsisaurus. The diversity of abelisauroid and titanosaurian dinosaurs in Cretaceous India indicates they shared close affinities to the dinosaur life of the otherGondwanan continents, which had similar inhabitants.[13] Dinosaurs in India probably went extinct due to volcanic activity around 350,000 years before theCretaceous–Paleogene boundary. They likely avoided areas with volcanicfissure vents andlava flows.[14]
.jpg)
.png)
.png)
.jpg)
.jpg)
.png)
.jpg)
