Lametasaurus

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Lametasaurus
Temporal range: Late Cretaceous, 70 Ma
↓
Tibia from the holotype of L. indicus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Genus: †Lametasaurus
Matley, 1923
Type species
†Lametasaurus indicus

Lametasaurus (lə-MAY-tə-SOR-us - meaning "Lameta lizard") named for the Lameta Formation, Jabalpur, India, is the generic name given to a possibly chimeric dinosaur species.[1] The type species is L. indicus.

History of discovery[edit]

Between October 1917 and 1919 Charles Alfred Matley excavated fossils near Jabalpur.[2] In 1921 he reported the find in the "Carnosaur Bed" of what he considered to be two megalosaurians, theropod dinosaurs.[3] In 1923/1924 he named one of these as the type species Lametasaurus indicus. The generic name refers to the Lameta Formation, dating from the Maastrichtian, the specific name refers to India. However, Matley no longer identified it as a theropod but as a member of the Stegosauria instead, which concept at the time also included the armoured dinosaurs today assigned to the Ankylosauria; at first Matley had seen it as a stegosaurian in the modern sense and even intended to name it as a species of Omosaurus.[2] The type specimen consisted of a number of dermal scutes, a sacrum of at least five sacral vertebrae, a pelvis, a tibia and teeth.[4] In 1933 Matley and Friedrich von Huene described some more remains collected by Barnum Brown,[2] thought to have been part of a tail club;[5] later this was shown to be a large osteoderm.[2]

However, in 1935 Dhirendra Kishore Chakravarti contested the interpretation as an armoured dinosaur. He claimed that the specimen was a chimera including titanosaurid armor, crocodile teeth and theropod hindlimb material.[6] In 1964 Alick Walker chose the scutes as the lectotype, thus removing the teeth and the bones from the type material.[7] The name Lametasaurus now designated the scutes only and was generally considered to represent a member of the Nodosauridae. The pelvis and hindlimb bones have in 2003 been suggested to belong to Rajasaurus, based on shared features in the ilium.[8] In 2008 Matthew Carrano e.a. discarded the possibility the scutes were ankylosaurian, stating they were probably titanosaurian, but noted that a comparison to the osteoderms of Ceratosaurus would help in determining its affinities. If in which case the species were to be found ceratosaurian, it would possibly be a senior synonym of Indosaurus and/or Rajasaurus.[9] Most recently, it has been suggested that some of the osteoderms assigned to Lametasaurus show ankylosaurian synapomorphies,[10] which renders Lametasaurus a chimera regardless of the affinities of the other material.

The type material has been lost, lacking a known inventory number, making it difficult to test the several hypotheses. The taxon is today commonly seen as a nomen dubium.[11]

References[edit]

  1. ^ Bervoets, Fred. "Lametasaurus Indicus". Dino Data. Archived from the original on 2013-03-17. Retrieved 2012-04-23.
  2. ^ a b c d Carrano, M.T., J.A. Wilson, P. M. Barrett, 2010, "The history of dinosaur collecting in central India since 1828", In: Moody, R.T.J., E. Buffetaut, D. Naish, and D. M. Martill (eds.), Dinosaurs and Other Extinct Saurians: A Historical Perspective. Geological Society, London, Special Publications 343: 161–173
  3. ^ Matley, C.A., 1921, "On the stratigraphy, fossils and geological relationships of the Lameta beds of Jubbulpore", Records of the Geological Survey of India 53: 142–169
  4. ^ Matley, C.A., 1923, "Note on an armoured dinosaur from the Lameta beds of Jubbulpore", Records of the Geological Survey of India, 55: 105-109
  5. ^ Huene, F. von, & Matley, C.A., 1933, "The Cretaceous Saurischia and Ornithischia of the central provinces of India", Palaeontologia Indica, 21: 1–74
  6. ^ Chakravarti, D. K., 1935, "Is Lametasaurus indicus an armored dinosaur?", American Journal of Science 30(5): 138-141
  7. ^ Walker, A., 1964, "Triassic reptiles from the Elgin area: Ornithosuchus and the origin of carnosaurs", Philosophical Transactions of the Royal Society of London B 248: 53-134
  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. ^ M.T. Carrano and S.D. Sampson, 2008, "The phylogeny of Ceratosauria (Dinosauria: Theropoda)", Journal of Systematic Palaeontology 6(2): 183-236
  10. ^ Rozadilla, Sebastián; Agnolín, Federico; Manabe, Makoto; Tsuihiji, Takanobu; Novas, Fernando E. (2021-09-01). "Ornithischian remains from the Chorrillo Formation (Upper Cretaceous), southern Patagonia, Argentina, and their implications on ornithischian paleobiogeography in the Southern Hemisphere". Cretaceous Research. 125: 104881. doi:10.1016/j.cretres.2021.104881. ISSN 0195-6671.
  11. ^ F.E. Novas, S. Chatterjee, D.K. Rudra and P.M. Datta, 2010, "Rahiolisaurus gujaratensis, n. gen. n. sp., a new abelisaurid theropod from the Late Cretaceous of India". In: S. Badyopadhyay (ed.), New Aspects of Mesozoic Biodiversity. Lecture Notes in Earth Sciences 132, pp. 45-62

External links[edit]

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