# News this Week

Science  23 Oct 2015:
Vol. 350, Issue 6259, pp. 360
1. # This week's section

### Predator wannabe just another T. rex

Some scientists think that Tyrannosaurus rex, which roamed the western United States between 68 million and 66 million years ago, had a smaller cousin named Nanotyrannus. But a new study, presented this week at the Society of Vertebrate Paleontology meeting in Dallas, Texas, supports the argument that Nanotyrannus is simply a juvenile version of T. rex. Scientists have wrangled over Nanotyrannus for decades: A skull found in Montana was first described in 1946 as a member of the tyrannosaur family, but other researchers later concluded that it was a separate, smaller taxon based on the fusing of the bones in its skull. Years later, another paleontologist concluded that the skull bones weren't fused and that it was a juvenile T. rex after all. A second skull and partial skeleton, found in 2002 in Montana, seemed to bolster this case. Now, the new study, based on a 3D computer reconstruction of the second skull and skeleton, counted microscopic “growth rings” in its calf bone and concluded that it was indeed a juvenile. Yet the debate isn't quite over: Scientists in the Nanotyrannus camp argue that a third skeleton—found in 2006 but mired in controversy after its owners tried to auction it—would provide the best evidence for their case. http://scim.ag/nanotyranno

## Findings

### Parts of Ebola virus hide in semen

Researchers have known since 1999 that traces of the Ebola virus could remain in semen for months; but two papers published in The New England Journal of Medicine last week offer details about the frightening possibility that survivors of an Ebola infection could rekindle outbreaks. In one study of 93 survivors in Sierra Leone, researchers found Ebola viral RNA in semen samples from 46 men; the likelihood of finding viral RNA declined over time. But there isn't enough information yet to assess how that translates to risk of transmission, the authors noted. However, the second paper documents a clear case of sexual transmission of Ebola virus: A 44-year-old Liberian woman was diagnosed with Ebola on 20 March, although there had been no cases of Ebola in the country in the previous 30 days. However, she reported having unprotected vaginal intercourse with an Ebola survivor on 7 March. The man had contracted Ebola in September 2014 and tested negative in early October; but a semen sample taken in March 2015 tested positive for Ebola. http://scim.ag/Ebolasemen

### Specks of oldest life?

Scientists have found potential evidence that life on Earth existed 300 million years earlier than previously thought. Researchers examined microscopic flecks of graphite in a 4.1-billion-year-old zircon crystal from the Jack Hills in Western Australia. Based on the ratio of light and heavy isotopes of carbon, the authors suggest the material is consistent with a biological origin, they report this week in the Proceedings of the National Academy of Sciences. If confirmed, the results would demonstrate that life evolved shortly after the formation of the planet 4.5 billion years ago. The authors acknowledge that nonbiological processes could also explain their results, but hope to find more graphite inclusions in other ancient zircons to help confirm their hypothesis. http://scim.ag/Zirconlife