From Today in Science History:
Published this Day, 1989: a 150-million-year-old fossil egg discovered in Utah was found by CAT scan to contain the oldest dinosaur embryo. The egg was still inside the mother, in , Hirsch, K.F.; Stadtman, K.L.; Miller, W.E. & Madsen, J.H.Jr. 1989. Upper Jurassic dinosaur egg from Utah. Science 243: 1711-1713.
Published this Day,1871: Charles Darwin's Descent of Man, and Selection in Relation to Sex is published in London.