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the tyrannosaur chronicles

1 september 2016

I grew up loving Tyrannosaurus rex as much as any kid of the 1960s – I like to think considerably more. It was right up there with the manned space program and the Chicago Cubs as one of my childhood delights. Yet I don't think I saw a "real" fossil of T. rex till I visited the American Museum of Natural History in New York as a middle-schooler in the early '70s. If there was a T. rex in Chicago in my youth, I believe it was a cast (not that there's anything wrong with casts, and a lot of "real" dinosaur skeletons include a lot of speculative cast material). Chicago is now home to Sue, the most famous of all tyrannosaurs, but fifty years ago specimens of Tyrannosaurus rex were few and far between.

The type specimen (the first to be scientifically described and named) is in Pittsburgh, at the Carnegie Museum, a couple of rooms away from the type specimen of Diplodocus. I didn't know that the type specimen of T. rex was in Pittsburgh till I was standing underneath it last year. Imagine growing up in Pittsburgh, with such a momentous fossil free for the running around on field trips. Imagine being that type specimen, chowing down on the hadrosaurs of the late Cretaceous, turning to stone in your long postmortem existence, and then millions of years later being dug up, shipped east, and mounted for the amusement of a bunch of scruffy mammals.

Tyrannosaurs are endlessly romantic, but there is little of the rapt or the sentimental in David Hone's recent book The Tyrannosaur Chronicles. It's an unusual and satisfying text: a monograph on technical issues in evolutionary biology, but written entirely for the lay reader. Hone's book offers a way into the current scientific literature if you're so inclined, or can stand for it if you have no plans to delve further.

As such, Hone admits that his project can barely stay ahead of new developments, and was assuredly obsolete upon publication. New fossils are being described all the time, and with each new fossil the picture of tyrannosaur diversity changes, and new ecological hypotheses arrive. Hone says ruefully that he'd predicted the discovery of "dwarf" species of tyrannosaur in a first draft, and by the time he'd gone to press they'd been found: Nanuqsaurus, as its name suggests a dweller on a remote Arctic island of the kind that often supports scaled-down populations of animal. Of course, a scaled-down tyrannosaur is still six meters long with a head the size of a horse's.

Despite ever-shifting data, it seems clear that tyrannosaurs were active hunters who held their tails high, laid eggs and practiced some parental care, had feathers, were possibly "warm-blooded" to some extent (maintaining body temperature either through metabolism or movement). These ideas, once the province of wacky theorizing, are now fairly well-established through keen inferences, sometimes from single fossils (sometimes single fossils of prey species). The amount of information that can be gleaned about the past from a few bones is amazing, a testimony to the care of their preparation and the logic of their preparers. Hone is very good at describing the process of scientific inference, and if he bogs down here and there in the wonders of taxonomy, it's with a pedagogical purpose. The book is among other things an excellent primer in evolutionary biology.

Above all, tyrannosaurs were very common creatures. Many odds are against their fossilization, as Hone argues. They were large predators, and as such were never going to dominate a landscape in terms of numbers or biomass, any more than mountain lions dominated the "American Serengeti" (as Dan Flores calls it) in the days of innumerable bison and antelope. Yet tyrannosaurs have been found in fair numbers on all continents and in many different climatic zones. They were adaptable and long-lived as a group, pace earlier common ideas about them as lumbering scavengers who could barely stand up on account of their silly little arms. They merit respect as the kings of the tyrant lizards they were.

Hone, David. The Tyrannosaur Chronicles: The biology of the tyrant dinosaurs. London: Bloomsbury, 2016.