Dog-sized dinosaur species found

With the help of 200-million-year-old fossilised bones, scientists have identified a new species of dinosaur that was largely herbivorous and the size of a small dog.

Named Laquintasaura venezuelae, the dinosaur is the first to be discovered in northern South America and shares its name with the La Quinta formation in Venezuela where it was found.

"It is always exciting to discover a new dinosaur species but there are many surprising firsts with Laquintasaura," said lead author Paul Barrett from Natural History Museum in London, Britain.

Measuring up at about a metre long and 25 cm tall, Laquintasaura would have been about the size of a small dog and was largely herbivorous - though the curve of some of its teeth suggest it might have also feasted on insects and small prey.

Scientists unearthed Laquintasauras tangled together in small groups including juveniles and fully grown adults.

The dinosaurs found together probably died at the same time, say the scientists, which could mean they were living in herds - a complex social interaction, so far not seen in this sort of dinosaur until the Late Jurassic around 40 million years later.

"It is fascinating and unexpected to see they lived in herds, something we have little evidence of so far in dinosaurs from this time," Barrett added.

Laquintasaura belongs to the "bird-hipped", or "Ornithischia", group of dinosaurs which later gave rise to Stegosaurus.

Analysing the residual radioactivity of tiny crystals in the rock, the scientists could pin down the age of Laquintasaura to the earliest Jurassic.

That means Laquintasaura possibly lived just 500,000 years after a mass extinction event that wiped out most other species on the Earth and marked the boundary between the Triassic and Jurassic.

The study appeared in the journal Proceedings of the Royal Society B.