When the Earth Was GreenRiley BlackSt. Martins Press, $29Imagine being a paleontologist exploring Utahs Jurassic-aged rocks. Imagine discovering the bones of a 20-meter-long, 20-ton herbivorous dinosaur. Then consider: How could any beast become so big? The answer, according to science writer and paleontologist Riley Black, lies in plants.Black narrates the story of this Jurassic saurian in a chapter of her latest book, When the Earth Was Green. The imagined Apatosaurus lumbers through lush cycads, ferns and conifers, vacuuming plant matter into her digestive system of enormous fermentation vats, which allows her to extract maximal nutrients. The abundance of verdant foliage available for the adult Apatosaurus to inhale drove its speciess gigantic size. Black even conjures the green pats of dung produced by the (probably) gassy animal as it farts along.With a focus firmly on plants, Black masterfully uses science to breathe life into ancient worlds in which some of our favorite prehistoric animals lived. Each chapter written as a vignette with its own appendix explaining the science behind Blacks story choices portrays a particular time and place.Take the first chapter, set in Arctic Canada 1.2 billion years ago. This is a world of no forests, no fish, no seashells. Bare rock studded with snowcapped mountains presided over sediment-filled oceans stocked with mats of cyanobacteria and other mostly unicellular organisms. Against this backdrop, Black describes something thats not quite plant. Its a multicellular, photosynthesizing red alga. Its only in this moment that what were once single cells are beginning to combine and coalesce into new and unexpected arrangements, she writes. We wouldnt be here without this evolutionary step.This red alga and its photosynthetic brethren are ancestors of the first plants that crept onto land, inadvertently luring critters out of the ocean. It was the plants, not fleshy-finned fish, that changed the world when they came ashore, Black writes.Paleontology is often framed as stories of colonization and conquest life colonized land, dinosaurs dominated the Mesozoic Era. Black rejects this framework, instead twining tales of communities into an evolutionary romance. She reminds us that we did not arrive here on our own, but as part of an ongoing relationship with the botanical. By itself, a dinosaur is just a dinosaur. Farting sauropods dining at the salad bars of Jurassic forests, warming the planet with their methane-rich malodors, is something else entirely.BuyWhen the Earth Was Green from Bookshop.org.Science Newsis a Bookshop.org affiliate and will earn a commission on purchases made from links in this article.