The bones of a massive dinosaur unearthed in Egypt at a fossil-rich oasis in the Sahara desert that scientists had ignored for more than 60 years are those of the second largest dinosaur ever discovered, say researchers.

The giant, which lived during the late Cretaceous period, 94 million years ago, was found in 1999 at the Bahariya Oasis, 180 miles South-west of Cairo, by an American team led by Joshua Smith of the University of Pennsylvania.

Paralititan stromeri was announced this year to be an entirely new discovery among herbivorous dinosaurs. It would have been up to 30.5m long, 15m tall and would have weighed as much as 75 tonnes. Only Argentinosaurus, a relative that lived in South America, is larger among known dinosaurs, at 21m high, 36.5m long and 110 tonnes.

The new dinosaur’s name, which means “tidal giant of Stromer”, comes from Ernst Stromer von Reichenbach, a German palaeontologist who found four new species of dinosaur at the same oasis between 1915 and 1936. Incredibly, the site was scarcely touched again before Joshua Smith’s expedition.

Paralititan lived in mangrove swamps, on what was then a coastal plain, and was a sauropod dinosaur - from the group of huge, four-legged herbivores which had long necks, small heads, and long tails that also includes Brontosaurus and Diplodocus.

A cousin of Tyrannosaurus rex found in 1997 by British palaeontologists on the Isle of Wight and named Eotyrannus lengi after Gavin Leng, a local collector who discovered the first bone, has also now been announced to be a completely new species of predator. It lived about 120 to 125 million years ago, and measured 4.5m.

www.sciencemag.org Science magazine, where details of Paralititan are published

www.egyptdinos.org Bahariya Dinosaur Project

www.upenn.edualmanacbetweenDinoBone.html University of Pennsylvania site on Paralititan

www.dinodata.netnewsdesuk.htm Dinodata on Eotyrannus

www.miwg.freeserve.co.uk Museum of Isle of Wight Geology

DOCTORS in the United States have sparked a new controversy over the ethics of fertility treatment, with the announcement that they have helped almost 200 couples to choose a baby’s sex for social reasons.

The Genetics and IVF Institute, in Fairfax, Virginia, uses a machine to separate a father’s sperm into those carrying male and female genetic material, increasing the chances of conceiving a child of the desired sex to 92 per cent for girls, and 72 per cent for boys.

The MicroSort system stains and sorts the sperm according to whether they carry an X or a Y chromosome. X-bearing sperm fertilise eggs to produce female embryos, while Y-bearing sperm give rise to male babies.

Most doctors will agree to select a child’s sex only when a couple carry a genetic disease, such as haemophilia or some forms of muscular dystrophy that are inherited only by boys. Such conditions are carried on the X chromosome. While females have two of these, and thus have a spare if one is damaged, males have just one, along with a Y chromosome, and therefore contract the disease if their X chromosome is faulty.

The American team, however, have agreed to use the technique for what they call “family balancing” - choosing a sex for social reasons. Experts on medical ethics have accused them of irresponsible social engineering.

www.givf.com Genetics and IVF Institute

www.microsort.com Genetics and IVF Institute page on the MicroSort system

www.nuffieldfoundation.orgbioethics Nuffield Council for Bioethics

NASA is promising to stage a spectacular firework display to celebrate American Independence Day in 2005: the US space agency is designing a spacecraft that will blow up part of a comet with a huge copper bullet. The Deep Impact mission, which was recently approved, will launch in January 2004, before firing its lethal payload at a comet named Tempel 1 on July 4, 2005.

When the “impactor” projectile, which weighs about 350kg, collides at 22,300mph with the comet’s icy core, it will blast a hole seven storeys deep and as wide as a football pitch, releasing clouds of debris into space. A mother ship loaded with scientific instruments will analyse the dust, seeking clues about what comets are made of.

Many scientists describe comets as cosmic “time capsules”, formed at about the same time as planets, about 4.5 billion years ago. The information they glean from Deep Impact may yield important new details about the origins of the solar system. Researchers are also eager to learn whether gas and ice from comets is spewed into space as an “exhaust”, or is sealed inside the nucleus, and whether the interior of the comet is different from its surface. Such data, in time, could be crucial to any attempts to deflect a comet on a collision course with Earth.

http:deepimpact.jpl.nasa.gov Nasa site on Deep Impact, including animations of the mission.

Mark Henderson is science editor of ‘The Times’