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Dravidosaurus
Dravidosaurus ("Dravidian lizard") is a dubious genus of Late Cretaceous reptiles, variously interpreted as either a ornithischian (possibly a stegosaurian) dinosaur or a plesiosaur. The genus contains a single species, D. blanfordi, known from mostly poorly preserved fossils from the Coniacian (Late Cretaceous) of southern India.
Dravidosaurus was originally described as a late-surviving stegosaur in 1979, younger in age than other known stegosaurs by tens of millions of years. This classification was questioned by Sankar Chatterjee in 1991, who suggested that the fossils were actually plesiosaurian. Chatterjee did however not formally reclassify any of the fossil specimens and did not examine all of them. Since 1991, researchers have variously followed Chatterjee's assessment, maintained Dravidosaurus as a stegosaur, or considered it an indeterminate ornithischian dinosaur.
Researchers in favor of a stegosaurian identity point to the presence of plates and spikes among the fossils, as well as certain morphological features. In 2017, Peter Galton and Krishnan Ayyasami reaffirmed that Dravidosaurus was a stegosaur and announced that further likely stegosaurian fossils from the same original site were currently being studied.
Dravidosaurus blanfordi was described in 1979 by Ponnala Yadagiri and Krishnan Ayyasami, based on fossils recovered from the Coniacian Anaipadi Formation of the Trichinopoly Group in southern India during the 1970s. The fossils were discovered at a site west of the village of Siranattam. The Dravidosaurus fossils were the first fossils assigned to a ornithischian dinosaur to be reported from India.
The fossils attributed to Dravidosaurus included the holotype GSI SR Pal 1, a partial skull, as well as fossils identified as an isolated tooth, a sacrum, an ilium, an ischium, ten armor plates, and a tail spike, designated (in order) as GSI SR Pal 2–7. Yadigiri and Ayyasami identified several of the skull bones in GSI SR Pal 1, of which the most well-preserved were the parietals, frontals, supraorbitals, squamosal, and quadrate. In addition to the armor plate GSI SR Pal 6, nine other fossils identified as armor plates were found associated with the referred specimens. These fossils have since their discovery been housed in the Palaeontological Laboratory of the Geological Survey of India. The fossils attributed to Dravidosaurus were at the time of its description determined to not be worn and to indicate that there had not been much transportation before burial. The hard limestone matrix around the fossil made extraction and preparation, done using a dental drill and chiselling. As of 2024, several bones originally attributed to Dravidosaurus is not available in the collections of the Geological Survey of India.
The generic name Dravidosaurus comes from Dravidanadu, a term often used for the southern part of India in which the Trichinopoly Group is situated. Dravidosaurus thus literally means "Dravidanadu lizard", though the name is sometimes interpreted as "lizard from south India". The specific name blanfordi honours H.F. Blanford, responsible for the pioneering research on the Cretaceous in southern India.
Yadagiri and Ayyasami identified Dravidosaurus as a stegosaur mainly based on features of the skull (GSI SR Pal 1) and the isolated tooth found associated with it (GSI SR Pal 2). Although differing in some characteristics, they determined that the skull was similar to that of Stegosaurus and that the tooth, merely 3 millimetres (0.1 in) long, closely resembled the teeth referred to other stegosaurian genera such as Kentrosaurus. The presence of fossil elements identified as armor plates and spikes were also interpreted as suggesting a stegosaurian identity. Yadagiri and Ayyasami placed Dravidosaurus in the subfamily Stegosaurinae.
Since they also identified what they considered to be diagnostic traits among the fossils, differentiating them from other stegosaurs known at the time, Yadagiri and Ayyasami erected the new genus Dravidosaurus. In terms of the proportions of the skull itself, Dravidosaurus was determined to be similar to Stegosaurus. Among the features that distinguished GSI SR Pal 1 were the postfrontal being absent, the beak being slightly different from that of Stegosaurus, the postorbital being thin and straight, and the pterygoid being thick and rectangular. GSI SR Pal 2 was distinguishable from the similar teeth of Kentrosaurus through possessing three rather than six crenulations. In addition to these features, Yadagiri and Ayyasami also distinguished Dravidosaurus by features of its sacrum, which indicated that it possessed ribs that were more slender than those of Kentrosaurus.
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Dravidosaurus
Dravidosaurus ("Dravidian lizard") is a dubious genus of Late Cretaceous reptiles, variously interpreted as either a ornithischian (possibly a stegosaurian) dinosaur or a plesiosaur. The genus contains a single species, D. blanfordi, known from mostly poorly preserved fossils from the Coniacian (Late Cretaceous) of southern India.
Dravidosaurus was originally described as a late-surviving stegosaur in 1979, younger in age than other known stegosaurs by tens of millions of years. This classification was questioned by Sankar Chatterjee in 1991, who suggested that the fossils were actually plesiosaurian. Chatterjee did however not formally reclassify any of the fossil specimens and did not examine all of them. Since 1991, researchers have variously followed Chatterjee's assessment, maintained Dravidosaurus as a stegosaur, or considered it an indeterminate ornithischian dinosaur.
Researchers in favor of a stegosaurian identity point to the presence of plates and spikes among the fossils, as well as certain morphological features. In 2017, Peter Galton and Krishnan Ayyasami reaffirmed that Dravidosaurus was a stegosaur and announced that further likely stegosaurian fossils from the same original site were currently being studied.
Dravidosaurus blanfordi was described in 1979 by Ponnala Yadagiri and Krishnan Ayyasami, based on fossils recovered from the Coniacian Anaipadi Formation of the Trichinopoly Group in southern India during the 1970s. The fossils were discovered at a site west of the village of Siranattam. The Dravidosaurus fossils were the first fossils assigned to a ornithischian dinosaur to be reported from India.
The fossils attributed to Dravidosaurus included the holotype GSI SR Pal 1, a partial skull, as well as fossils identified as an isolated tooth, a sacrum, an ilium, an ischium, ten armor plates, and a tail spike, designated (in order) as GSI SR Pal 2–7. Yadigiri and Ayyasami identified several of the skull bones in GSI SR Pal 1, of which the most well-preserved were the parietals, frontals, supraorbitals, squamosal, and quadrate. In addition to the armor plate GSI SR Pal 6, nine other fossils identified as armor plates were found associated with the referred specimens. These fossils have since their discovery been housed in the Palaeontological Laboratory of the Geological Survey of India. The fossils attributed to Dravidosaurus were at the time of its description determined to not be worn and to indicate that there had not been much transportation before burial. The hard limestone matrix around the fossil made extraction and preparation, done using a dental drill and chiselling. As of 2024, several bones originally attributed to Dravidosaurus is not available in the collections of the Geological Survey of India.
The generic name Dravidosaurus comes from Dravidanadu, a term often used for the southern part of India in which the Trichinopoly Group is situated. Dravidosaurus thus literally means "Dravidanadu lizard", though the name is sometimes interpreted as "lizard from south India". The specific name blanfordi honours H.F. Blanford, responsible for the pioneering research on the Cretaceous in southern India.
Yadagiri and Ayyasami identified Dravidosaurus as a stegosaur mainly based on features of the skull (GSI SR Pal 1) and the isolated tooth found associated with it (GSI SR Pal 2). Although differing in some characteristics, they determined that the skull was similar to that of Stegosaurus and that the tooth, merely 3 millimetres (0.1 in) long, closely resembled the teeth referred to other stegosaurian genera such as Kentrosaurus. The presence of fossil elements identified as armor plates and spikes were also interpreted as suggesting a stegosaurian identity. Yadagiri and Ayyasami placed Dravidosaurus in the subfamily Stegosaurinae.
Since they also identified what they considered to be diagnostic traits among the fossils, differentiating them from other stegosaurs known at the time, Yadagiri and Ayyasami erected the new genus Dravidosaurus. In terms of the proportions of the skull itself, Dravidosaurus was determined to be similar to Stegosaurus. Among the features that distinguished GSI SR Pal 1 were the postfrontal being absent, the beak being slightly different from that of Stegosaurus, the postorbital being thin and straight, and the pterygoid being thick and rectangular. GSI SR Pal 2 was distinguishable from the similar teeth of Kentrosaurus through possessing three rather than six crenulations. In addition to these features, Yadagiri and Ayyasami also distinguished Dravidosaurus by features of its sacrum, which indicated that it possessed ribs that were more slender than those of Kentrosaurus.