Fossils of a tiny newly discovered dinosaur are making palaeontologists rethink the shape of evolutionary trees.
From its snout to the tip of its long tail, the plant-eating Foskeia pelendonum, which walked on two legs, measured just over half a metre. Upright it would just about reach a human's knee.
Palaeontologists analysed new cranial elements from at least five specimen of the rhabdodontomorph from the Lower Cretaceous period, which were uncovered in Salas de los Infantes in northern Spain.
What they found was that the dinosaur's skull was "weird and hyper-derived," Marcos Becerra from Universidad Nacional de Córdoba said, stressing: "Miniaturization did not imply evolutionary simplicity."
Research leader Paul-Emile Dieudonné, from Argentina's National University of Río Negro, said that "From the very first moment anybody sees this animal one is staggered by its extreme smallness ... and yet it preserves a highly derived cranium with unexpected anatomical innovations."
The study, published on Sunday in Papers in Paleontology, positions Foskeia near the origin of the European herbivorous lineage Rhabdodontidae.
Thierry Tortosa of the Sainte Victoire Natural Reserve said that the dinosaur "helps fill a 70-million-year gap, a small key that unlocks a vast missing chapter."
Penélope Cruzado-Caballero from Universidad de La Laguna agrees: "This is not a 'mini Iguanodon', it is something fundamentally different ... Its anatomy is weird in precisely the kind of way that rewrites evolutionary trees."
