The ‘Ashdown maniraptoran’
Most palaeontologists now accept that birds are descended from non-avian dinosaurs and are therefore the only living representatives of otherwise terrestrial animals that ruled the world during the Mesozoic. That being the case, the Cuban bee hummingbird, which measures just 5cm in length and weighs about 1.8g, is arguably the world’s smallest dinosaur. However, if birds are excluded and looking only at the non-avian dinosaurs, all of which became extinct in the often-discussed mass extinction event at the end of the Cretaceous, what is the world’s smallest dinosaur? Until very recently and considering only animals that are thought to be fully grown, the answer is Anchiornis huxleyi (Hu et al., 2009; Fig. 1) from the earliest Late Jurassic of China. This tiny, feathered troodontid has been estimated to be between 34 to 40cm long (excluding the tail feathers). In the ever-changing environment of what represents the world’s largest and what the smallest, Anchiornis’ position as the world’s smallest dinosaur has now been threatened and quite possibly overturned. The fossil concerned is not another wonderful specimen from the Late Jurassic or Early Cretaceous of China, but a single, tiny cervical (neck) vertebra (Fig. 2) discovered at a brickworks near Bexhill, in East Sussex.