Fossil remains of a bird from the Late Cretaceous suggest it was up to three metres tall and weighed more than 50kg

Two slender shafts of bone unearthed in the remote desert of southern Kazakhstan belong to one of the largest birds ever to stalk the Earth.

The fossilised remains form two sides of the lower jaw of a bird – at least as big as an ostrich – that lived alongside dinosaurs in central Asia 100m years ago.

The size of the bones, more than 27cm-long each, point to a bird that stood two to three metres tall, making it the largest bird known from the Late Cretaceous. Many primitive birds alive at the time were closer in size to chickens.

The lack of other remains from the creature has left palaeontologists unable to confirm whether the bird was capable of flight. If it did fly, its wingspan probably topped 4m – wider than that of a large albatross.

Details of the bird, named Samrukia nessovi, are reported in the latest issue of the Royal Society journal, Biology Letters.

The two lengths of bone were uncovered at a site called Shakh-Shakh about 372 miles (600km) east of the Aral Sea during a Soviet-East German expedition in the 1970s. The fossil was reconstructed using plaster, glue and paint, to make it look like a complete jaw, passed through the hands of a German collector, and later went on display in a Belgian museum.

Gareth Dyke, a palaeontologist at University College Dublin, dissolved the plaster and other materials used to reconstruct the fossil with solvents before analysing the bone fragments. Measurements of the remains suggest they belonged to a bird whose skull was 30cm from front to back. The creature, if flightless, almost certainly weighed more than 50kg.

"This is one of the largest birds that's ever been described of any age. We don't have much of it, but we know the lower jaw is at least as big if not bigger than the ostrich lower jaw. At the age it is, it's pretty exciting," Dyke told the Guardian.

"We have always assumed that giant size in birds was something that evolved relatively late in the history of the group, so to find a specimen so early is remarkable. This is a giant of a bird with no teeth from the Late Cretaceous."

The bird earned its forename from Samruk, the mythological Kazakh phoenix. The latter part of its name honours Lev Nessov, an eccentric Russian palaeontologist who used to take the bus or train from St Petersburg into Central Asia to embark on long hikes into the desert to hunt for fossils. He killed himself in 1995 at the age of 48 after the breakup of the Soviet Union restricted his travels.

Another large bird, named Gargantuavis, that lived in southern France 70m years ago was discovered in the late 1990s. "Samrukia adds another giant bird to the Cretaceous roster. Arguably, in fact, it increases the significance of Gargantuavis, since it shows that it wasn't a one-off," said co-author Darren Naish at Portsmouth University.