Two reports on ancient reptiles
The first report is about finding fossils of ancient reptiles that swam in ancient Australia. The illustration is a reconstruction of Umoonasaurus demoscyllus showing an adult with crest (top) and juvenile (bottom).
BBC NEWS | Science/Nature | Australian 'Nessie' fossils found
Australia was once home to ancient reptiles that swam in huge icy lakes, fossil evidence suggests.
The large, carnivorous reptiles lived 115 million years ago, during the age of the dinosaurs, when much of the continent was covered in water.
Fossils of two new species of plesiosaur were discovered near Coober Pedy in South Australia.
Plesiosaurs are popular in science fiction and are said to resemble Scotland's mythical Loch Ness monster.
The Australian specimens are described in recent editions of the journals Biology Letters and Palaeontology.
One, known as Umoonasaurus demoscyllus , was about 2.4m (7.2ft) long and had crests on its head, perhaps for display or mating purposes.
"Imagine a compact body with four flippers, a reasonably long neck, small head and short tail, much like a reptilian seal," said the lead author of the two papers, Dr Benjamin Kear of the University of Adelaide.
The other species, Opallionectes andamookaensis , grew to about 5m (16ft) long and had small needle-like teeth.
Some 30 fossils were discovered at an opal mine near the outback mining town of Coober Pedy.
They are made up of the mineral opal, which filled the spaces left by bones when the original fossil-bearing rock was dissolved away by acidic ground water.
The fossils include several skeletons and a complete skull of Umoonasaurus, and a partial skeleton of Opallionectes.
They are thought to be of juvenile animals, suggesting the lake was a breeding and nursery ground.
Scientists believe sea-dwelling adults returned to the shallow inland waters to breed and raise their young.
At the time, Australia was much colder, and the inland ocean would have frozen over in places during the winter.
Scientists believe the creatures might have evolved mechanisms to cope with the harsh climate, such as a faster metabolic rate. They were carnivorous, feeding on fish and squid.
The second report solves a mystery about the nifty crest the male pterosaur sported, the dinosaur version of an expensive red sports car. (Thanks to John Latter and his comment with the link to the journal Palaeontology.)
BBC NEWS | Science/Nature | Flying reptile mystery 'solved'
UK scientists say they have solved the mystery of why prehistoric flying reptiles grew crests on their heads.
A rare skull specimen found in Brazil shows the crest appeared at puberty, suggesting it was used to attract attention from the opposite sex.
University of Portsmouth experts say pterosaurs, which ruled the air during the time of the dinosaurs, flaunted their headgear in sexual displays.
The findings are published in the journal Palaeontology.
Palaeobiologist Dr Darren Naish said the crest was a signal of sexual maturity; used like a peacock's tail to attract a mate.
"It would have been like a gigantic cockerel's comb, a brightly-coloured striking structure used in display," he told the BBC News website.
"We don't know this but we imagine they would have bobbed it around and used it to attract other pterosaurs.
The theory is based on the skull of a species of pterosaur known as Tupuxuara, which was unearthed recently in north-east Brazil.
It was a rare discovery; only a handful of fossil specimens exist in the world and all the others are the remains of adults.
Dr Naish and colleague Dr David Martill examined the skull and found that the crest was different in the juvenile.
Rather than forming one large triangular crest of bone extending from the snout to the back of the head, it was made up of two pieces.
One crest came from the back of the skull and the other from the front of the snout. The crest that sprouted from the front grew backwards, only fusing to form one large crest when the pterosaur reached puberty.
"This is a significant find as it links the growth of the crest to physical maturity and therefore presumably to sex," said Dr Naish.
"The specimen was extremely rare and it is great to be able to piece together a little bit more details about pterosaurs."