Soft dinosaur eggs

One of the biggest mysteries in paleontology— why there are so few dinosaur-egg fossils— appears to have been solved. The explanation: Early dinosaurs laid soft eggs, most of which decomposed before they fossilized. Researchers made the discovery after studying a clutch of embryos from the horned dinosaur Protoceratops. The 72 million– year-old embryos, found in Mongolia, were surrounded by a thin film rather than a shell. That film has the same chemical fingerprint as the soft eggs from animals such as turtles. Tests revealed that the fossilized egg of a long-necked dinosaur from Argentina called Mussaurus, which lived some 200 million years ago, also matched the soft-shelled fingerprint. Early dinosaurs may have buried their eggs to protect them from losing water through their permeable soft shells. The evolution of hard eggshells allowed the animals to lay eggs on hard ground. Lead author Mark Norell, from the American Museum of Natural History, suspects paleontologists will identify more soft-shelled eggs now they know what to look for. “Soft-tissue preservation,” he tells NPR.org, “occurs more and more and more frequently than any of us ever dreamed.”

sus on exactly how people become infected, reports The Wall Street Journal. Covid-19 isn’t easily contracted from a contaminated surface—such as a cardboard delivery box—or from brief encounters with people outside. The most likely method of transmission is close-up interaction, indoors, lasting 15 minutes or more. The 15-minute figure is only a guideline, though; a sneeze or cough in the face could transmit the virus in an instant. Poor ventilation increases the risk of the virus spreading, and so, too, does anything involving lots of heavy breathing or shouting, such as exercising in a gym, singing in a church, or talking loudly in a bar. Respiratory droplets—large drops of fluid emitted when people sneeze, cough, talk, and breathe—are the major mode of transmission and can transfer the virus from one person to another if they land on the nose, mouth, or eyes. These droplets typically fall to the ground not far from where they are exhaled, hence the 6-feet rule. Some researchers think the virus may also be carried by smaller droplets known as aerosols, which can linger in the air much longer.