From Scientific American, Tiny, Ancient Crustacean Preserved in Fool’s Gold, Legs, Eggs and All, By Jennifer Frazer, March 27, 2014
... Incredibly, the paper describing these new fossils notes that the arrangement of some of the structures on the first antenna is the same as that of the group of living ostracods they are hypothesized to have belonged to, “even down to the tiny ventral seta and two long distal setae.” That such details could remain unchanged over 450 million years is, in my opinion, mind-boggling....
Image: Have Shell, Will Travel. The pyritized Luprisca incuba in all its glory with leg-like antennae on top and eggs on bottom. From Siveter et al., 2014. Click for source.