'Dahalokely tokana,' is estimated to have been between nine and 14 feet long, and belongs to a group called abelisauroids, carnivorous dinosaurs common to the southern continents.
Up to this point, no dinosaur remains from between 165 and 70 million years ago could be identified to the species level in Madagascar - a 95 million year gap in the fossil record. Dahalokely shortens this gap by 20 million years.
The fossils of Dahalokely were excavated in 2007 and 2010, near the city of Antsiranana (Diego-Suarez) in northernmost Madagascar.
Bones recovered included vertebrae and ribs. Because this area of the skeleton is so distinct in some dinosaurs, the research team was able to definitively identify the specimen as a new species.
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Several unique features - including the shape of some cavities on the side of the vertebrae - were unlike those in any other dinosaur. Other features in the vertebrae identified Dahalokely as an abelisauroid dinosaur.
Geological evidence indicates that India and Madagascar separated around 88 million years ago, just after Dahalokely lived.
The bones known so far preserve an intriguing mix of features found in dinosaurs from both Madagascar and India.
"We had always suspected that abelisauroids were in Madagascar 90 million years ago, because they were also found in younger rocks on the island.
"Dahalokely nicely confirms this hypothesis," said project leader Andrew Farke, Augustyn Family Curator of Paleontology at the Raymond M Alf Museum of Paleontology in California.
The name "Dahalokely tokana" is from the Malagasy language, meaning "lonely small bandit."
The study was published in the journal PLOS ONE.