Research roundup: 7 cool science stories we almost missed

It’s a regrettable reality that there is never enough time to cover all the interesting scientific stories we come across each month. In the past, we’ve featured year-end roundups of cool science stories we (almost) missed. This year, we’ve experimented with a monthly collection. December’s list includes a fossilized bird that choked to death on rocks; a double-detonating "superkilonova"; recovering an ancient seafarer's fingerprint; the biomechanics of kangaroo movement; and cracking a dark matter...