Barapasaurus

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Barapasaurus
Temporal range:
Ma
Life restoration
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: †Sauropodomorpha
Clade: †Sauropoda
Clade: †Gravisauria
Genus: †Barapasaurus
Jain et al., 1975
Species:
†B. tagorei
Binomial name
†Barapasaurus tagorei
Jain et al, 1975

Barapasaurus (

sauropod dinosaur from Jurassic rocks of India. The only species is B. tagorei. Barapasaurus comes from the lower part of the Kota Formation, which is of Early to Middle Jurassic age. It is therefore one of the earliest known sauropods. Barapasaurus is known from approximately 300 bones from at least six individuals, so that the skeleton is almost completely known except for the anterior cervical vertebrae and the skull
. This makes Barapasaurus one of the most completely known sauropods from the early Jurassic.

Discovery and naming

All known fossils come from a single locality in the vicinity of the village of

Maharastra, in central India).[1] The first bones were discovered in 1958, but most specimens were unearthed in 1960 and 1961.[2] In 1975, the finds were described scientifically by palaeontologist Sohan Lal Jain and colleagues.[1] In 2010, a more detailed osteological description was published by Bandyopadhyay and colleagues.[2] The material is archived in the palaeontological collection of the Indian Statistical Institute (ISI), while a majority of the bones are part of a mount at the Geological Museum of the ISI.[2]

Etymology

The name Barapasaurus ("big-legged lizard") is derived from bara meaning 'big' and pa meaning 'leg' in several Indian languages including Bengali; the Greek word sauros means 'lizard'.[1] This name was used as a nomen nudum since a femur measuring over 1.7 m was unearthed at 1961.[1] The specific name tagorei means 'Tagore's', which honours Bengali poet, writer, painter, and musician Rabindranath Tagore. The first year of fieldwork was carried out in the centenary year of Tagore's birth.[1]

Fossil record

Reconstructed skeletal mount of Barapasaurus tagorei, based on Jain (1979)[3]

Barapasaurus tagorei is known from a large

index fossils in the formation. The age has generally been interpreted as Early Jurassic, with the Lower Kota Formation in particular dating to the Sinemurian to Pliensbachian, roughly 184–200 million years ago. However, some studies have argued that the Kota Formation dates to the Middle Jurassic or even later.[4][5]

Taphonomy

The approximately 300 bones were found together with large trunks of trees scattered over an area of 276 square meters. Although one of the specimens was found partly articulated, most bones were found disarticulated. Because there are six left femora, the total number of individuals is at least six.[2]

Bandyopadhyay and colleagues (2002, 2010) interpret this assemblage as a herd that died due to a catastrophic event, likely a flood. This flood could have unearthed the trees and transported both trees and Barapasaurus a distance before they began to decompose. After decomposition progressed, the bones began to disarticulate. The disarticulated skull bones were removed by the water stream because they were light, leaving only the heavy postcranial bones at the site, which would explain why no skull bones were found.[2]

Description

Size comparison of Barapasaurus tagorei

Although a very early and unspecialised sauropod, Barapasaurus shows the building plan typical for later, more derived sauropods: the cervical vertebrae were elongated, resulting in a long neck. The trunk was short and holds columnar limbs which indicate an obligate quadrupedal posture.[3][2] Even the size, which is estimated at approximately 12-14 meters long and 7 tonnes in weight,[6][7] is comparable with that of later sauropods.[3]

The vertebral column already shows many traits that are typical for later sauropods which allowed them to attain great body sizes, although in later sauropods these traits are much more developed. The central and neural spines show early hints of hollowing as a weight-saving measure. The dorsal vertebrae are stabilised with hyposphene-hypantrum articulations, accessory projections that link the vertebrae with each other. The sacrum is strengthened through an additional fourth sacral vertebra.[2]

From the skull, only three whole teeth and three crowns are known. The largest known tooth is 5.8 cm in height. Like that of later sauropods, the teeth are spoon shaped and show wrinkled enamel. A basal trait is the coarse serration.[2]

Classification

Cladogram of basal Sauropoda
 Sauropoda 

 Jingshanosaurus

   

 Antetonitrus

   

 Chinshakiangosaurus

   

 Kotasaurus

   

 Barapasaurus

   
Bandyopadhyay 2010[2]

The relationships of this genus within the Sauropoda are debated. When first described in 1975, it was not attributed to one specific group at all, although the presence of many basal,

polyphyletic. Upchurch erected a clade named Eusauropoda that includes all known sauropods except some very basal forms. While Vulcanodon was classified outside the Eusauropoda, Barapasaurus was classified inside it, which means that Barapasaurus is more derived than Vulcanodon.[2][8] Although Upchurch's classification was accepted by most palaeontologists, a recent study from Bandyopadhyay and colleagues came to a contrary conclusion: these palaeontologists stated that Barapasaurus was in fact more basal than Vulcanodon and removed it from Eusauropoda.[2]

Habitat

Barapasaurus comes from clay and

rhynchocephalians, a lepidosaur and some mammals.[2]

References

  1. ^ a b c d e f Jain, S. L.; T. S. Kutty; T. Roy-Chowdhury; S. Chatterjee (18 February 1975). "The Sauropod Dinosaur from the Lower Jurassic Kota Formation of India".
    S2CID 84957608
    . Retrieved 13 October 2012.
  2. ^ a b c d e f g h i j k l m Bandyopadhyay, Saswati; David D. Gillette; Sanghamitra Ray; Dhurjati P. Sengupta (2010). "Osteology of Barapasaurus tagorei (Dinosauria: Sauropoda) from the Early Jurassic of India". Palaeontology. 53 (3): 533–569.
    ISSN 1475-4983
    .
  3. ^ a b c Jain, S. L.; T. S. Kutty; T. Roy-Chowdhury; S. Chatterjee (1979). "Some characteristics of Barapasaurus tagorei, a sauropod dinosaur from the Lower Jurassic of Deccan, India". Proceedings of the IV International Gondwana Symposium, Calcutta. Vol. 1. pp. 204–216.
  4. S2CID 253638698
    .
  5. S2CID 248368302
    .
  6. ^ Glut, Donald F. (1997). Dinosaurs, the encyclopedia. McFarland & Company, Inc. Publishers.
    ISBN 978-0-375-82419-7
    .
  7. ISBN 9780691137209
    .
  8. ^ Upchurch, Paul (29 September 1995). "The Evolutionary History of Sauropod Dinosaurs". Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 349 (1330): 365–390.
    ISSN 1471-2970
    .

External links
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