I've been reading The Rise and Fall of the Dinosaurs: A New History of a Lost World by Stephen L. Brusatte. It's a well-written and interesting book and has a good balance of history/personal experiences/interesting people/dinosaurs to stay engaging. It was interesting to read how late in the game dinosaurs developed and took off. Mammals more or less became a distinct group a while before dinos and mammals and their precursors were at the top of the food chain until the very end of the Triassic. The mind blowing part of this is that the Triassic is portrayed in popular culture as being firmly in the era of dinosaurs even though it really wasn't. The dinos began to dominate as they got bigger and bigger - and their gigantism was fueled in part by some nifty traits. They had the lung and bone structure of birds which means that they have secondary air sacs (like mini-lungs) distributed throughout their bodies and in their bones. This makes it easier to get large and still maintain high energy levels while simultaneously making them lighter. The sauropods (leaf eaters) also had phenomenally adaptable body plans that allowed their necks and tails to stretch to their characteristic proportions. This allowed them to stand in one spot and hoover up a huge amount of plant material without having to move their bodies and expend a lot of energy in doing so. Oh and the changeover from Triassic to Jurassic was very reminiscent of what happened with the Cretaceous/Tertiary changeover only in reverse. Both were mass extinctions that eliminated all of the large-bodied plant and meat eaters from the food chain, allowing the second-rank species of a completely different group a chance to evolve into those emptied niches and grow large. From the Triassic to Jurassic the handover went from mammals to dinos while the Cretaceous to Tertiary handover went the opposite way. I just got to the section on T-Rex and it's clear that Stephen is either a fan or keenly aware of the need to fan service this most charismatic of dinos. It turns out the T-Rex had a large brain and had an EQ (a measure of body mass to brain size that is an OK indicator of intelligence) of 4, which is on par for dolphins and twice as high as dogs. Also, not only were the skulls huge and scary, they had a lot of adaptations in the adult animals that allowed them to literally chomp on big dinosaurs like triceratops. Very few predators then or now actually take huge chunks of their prey and instead wound it or strangle it and then pick the flesh off the bones. T-Rex was more like a great white in that it really could just take a chunk out of another dinosaur like you'd expect in a cartoon. The juveniles did not have this ability though, and would have had to hunt more like a typical predator by chasing it down and delivering many small bites; while the adults would rely more on ambush and sheer power. There is bone and footprint evidence that suggest that T-Rexes spent time together in large groups containing juveniles and adults. Stephen believes they probably hunted in mixed packs with the hunting strategies of the adults and juveniles complimenting each other. I can imagine a group of juvenile T-Rexes flushing a triceratops out of cover and straight into an ambush with a waiting adult T-Rex. Basically, little T-Rexes hunted like raptors and might have worked in teams with big T-Rexes that hunted like great whites. They could take down 20+ ton (i.e. tank-sized) animals. Terrifying stuff. They also had absurdly large olfactory areas in their brains (which may inflate their EQ scores to a degree), large eyes and very large inner ears. They weren't just smart and big - they had excellent sensory perception as well. Oh and they had feathers; although these feathers would have looked and functioned more like mammal hair than bird feathers. They have not found trace hair fossils on T-Rex itself but they have on its ancestors which makes it likely it was feathered.