Concretions are remarkable geological curiosities. They are spherical carbonate formations composed of mineral cement. Concretions are found near and far, from Western Kazakhstan to beaches in California. Usually the size of cannonballs, they form from water eroding a piece out of sedimentary rock. They almost look man-made.

(Warning: the following article contains spoilers, although minimal.)

Everyone loves dinosaurs—especially in movies.

Trilobites (a type of arthropod) appear in sedimentary rocks as part of the Cambrian Explosion.¹ In this episode, all the major animal groups first appear as fossils. They appear suddenly, fully-formed, and functional, and the older rock layers below them contain no ancestors.^2,3

Green blood is not something you see every day. The recent search for why several species of lizards found in New Guinea have green blood assumes an evolutionary origin for these creatures. It seems like the researchers started with a discovery that indicates green blood developed independently in four species from red-blooded ancestors.¹