Hornbills (family Bucerotiae) are a group of birds characterized by a long, down-curved bill, sometimes with a casque on the upper mandible. Frequently, the bill is brightly coloured. Many of the birds are now endangered. Some species of hornbill are protected in Malaysia. Both the common English and the scientific name of the family refer to the shape of the bill, "buceros" being "cow horn" in Greek. In addition, they possess a two-lobed kidney. Hornbills are the only birds in which the first two neck vertebrae (the axis and atlas) are fused together; this probably provides a more stable platform for carrying the bill.