1.1 At the Starting Gate
Enter the dinosaurs, a jumpstart for my scientific imagination.
I might never have given this isolated episode another thought were it not for the seemingly unrelated fact that, like so many kids before and since, I had avidly collected dinosaur models. But not just any models. While there were the standard brightly colored clunky dino toys still available in grocery store packets today, in the early 1960s a series of particularly well-crafted replicas were being issued, based on the spectacular paleontological mural, “The Age of Reason,” painted by Rudolph Zallinger decades before for the Peabody Museum at Yale University. Gould (1993b, 8-9) illustrates the famed dinosaurian segment, while the full panorama is available at the Peabody Museum website (peabody.yale.edu/mural). I still see the molds for many of the “Yale series” being used today, though rarely executed with the comparative precision of the originals in my collection.
As long as sales held up, whoever was responsible for the set kept issuing new ones, and might presumably have eventually modeled every animal shown on the Yale mural. That didn’t happen, but the ones they did get to included many that were distinctly not dinosaurs, such as the flying reptile Pteranodon, nor even contemporary with them (though in this regard you can imagine what I might have believed had I been reared on the Young Earth creationism—YEC for short—of Henry Morris (1918-2006) or Duane Gish (1921-2013) instead of the World Book Encyclopedia). While the woolly mammoth and sabertooth tiger in the set were clearly more recent than Brontosaurus or T. rex, they makers included reptiles not so popular in modern prehistoric life series, creatures far more ancient than the dinosaurs. These were Dimetrodon, Sphenacodon, and Moschops, which lived during the Permian period just preceding the Mesozoic “Age of Dinosaurs.”
That trio represented some of the early eccentric therapsid reptiles that will figure so prominently in the creation/evolution debate (per Chapter 7 below), though conspicuously absent in the Yale mural were many of the most important protomammals then known, as noted by Peter Ward (2000, 49-51). Assuming Zallinger knew of them and consciously elected to exclude them, size may have played a role, as he would have had to either show the small transitional therapsids out of scale in the foreground, or shown them hunkered down almost invisibly amid the increasingly massive dinosaur stars.
The fin-backed Dimetrodon shown in the mural would, of course, become a familiar cliché from many a prehistoric beast movie, when before the era of facile computer graphics the only alternative to laborious stop-motion animation was to stick a fin on some cooperative Gila monster and call it a Dimetrodon. That was what was done for the geologically preposterous but nonetheless highly entertaining 1959 film version of Jules Verne’s Journey to the Center of the Earth. That very familiarity has served Dimetrodon well, for it still gets included in a lot of “dinosaur” sets along with Pteranodon.
But those two other Permian creatures, Sphenacodon and Moschops, were dull indeed compared to my mighty dinosaurs. Low-slung quadrupedal predator Sphenacodon might have been a terror in its Permian heyday, but the herbivorous Moschops was a complete disappointment to me. Looking much like an overgrown frog, it had splayed legs and a congenitally dippy expression I could barely tolerate. Fortunately they belonged to an earlier age, which meant my budding sense of historical sequence permitted me to segregate them on chronological grounds, so they would never need to actually hobnob with the noble dinosaurs during imaginative maneuvering of critters among the miniature palm frond dioramas I assembled on my bedroom desk.
Beyond the pressing concerns of reptile esthetics, though, I had even more trouble grasping the matter of dinosaur size. It was apparent the Tyrannosaurus model was much too large compared to Brontosaurus, but my encyclopedia reading only compounded the problem by illustrating another sauropod instead, Diplodocus, which was supposedly even longer. Was Diplodocus the same size as Brontosaurus but with longer neck and tail? Or was it a smaller animal that only ended up being longer due to proportionally lengthier appendages? Without a way to scale to them together, I couldn’t tell. Nor could I keep clear in my mind what it meant to be a “lizard-hipped” Saurischian dinosaur as opposed to the “bird-hipped” Ornithischian ones, since both had examples that stood upright while others were on all fours. Without scale models representing all these types, I simply couldn’t keep any of it straight, and for years there the problem rested.
I grew up, learned geometry and history, began to believe some silly things, attended college, added some more silly things, began to figure out why I was wrong on all that, and finally invaded the job market, by which time it was the 1980s and there was a very big dinosaur revolution going on. A comprehensive series of uniform scale models appeared, far more accurate than my old Yale set. Based on the specimens at the British Museum (now known as the London Natural History Museum), they were joined later by equally detailed editions representing the Boston Museum and Pittsburgh’s Carnegie collections. With these in hand I could see that my second hypothesis about Diplodocus was the correct one: smaller than Brontosaurus but with a really long neck and tail.
As easily as observing zoo specimens, I could now draw on the insights of torrent of profusely illustrated works by a new generation of highly articulate dinosaur paleontologists. Hence my aestivating interest revived with a bang and in two shakes of a theropod tail I had become a dedicated student of the Dinosauria. I must commend the excellent dinosaur encyclopedia, David Norman (1985a), which particularly ignited my imagination. A world authority on the large Cretaceous herbivores, the iguanodontids (which also turned out to play a recurrent role in this present work), Norman concisely described both the fine details and legitimate controversies of modern paleontology, while John Sibbick’s stunning illustrations captured the vitality of these long lost creatures.
Coming back to dinosaurs when I did meant more than just catching up on lost time, though. It was a case of confronting the very nature of scientific inquiry. Being extinct animals, almost everything about their study had an inferential character about it. When I was young, dinosaurs were invariably characterized as brute, sluggish creatures that only managed to lumber on as long as they did because the supposedly “superior” mammals had yet to dislodge them. But that conception was toast by the 1980s, as paleontologists had discovered more new dinosaur genera than in all the preceding century. The structure and distribution of these beasts disposed of old concepts but raised fresh questions.
Were dinosaurs warm-blooded after all? Or did they possess a uniquely “dinosaurian” metabolism? Without living examples, how exactly could you tell? To examine this one issue alone required understanding the full range of animal thermoregulation. The implications of body stance and herding characteristics and bone histology (the internal structure of blood vessels) all had to be carefully evaluated. Some dinosaurs turn out to have lived in ancient polar regions. That meant you had to know paleoclimatology to decide just how nippy the Mesozoic Arctic and Antarctic were, in order to infer the metabolic range of the dinosaurs living in those regions.
In the quest to make sense of the dinosaurs, you could see the science being done, and exactly how it was being done. Clearly on display was the technique whereby any aspect of the natural world might be understood. So while Robert Bakker (1986) defended full blown warm-blooded endothermy for dinosaurs, Fastovsky & Weishampel (1996, 328-355), Padian (1997a) and Dingus & Rowe (1998, 224-227) favored a metabolic mix: functionally endothermic predatory theropods versus large herbivores managing quite well on cold-blooded ectothermy, and subsequent analyses have trended towards an intermediate “mesothermy” for dinosaurs: Fricke & Rogers (2000), Chinsamy-Turan (2008), McNab (2009), Eagle et al. (2011), and Balter (2014g) re Grady et al. (2014).
So many disciplines played a part in this debate. Take bone histology, the study of the arrangement of spaces in the bone structure. Growth rates of animals tell tales about their underlying metabolism, and the evidence has supported a non-reptilian growth rate for dinosaurs that in turn related to the potential origin of birds: Chinsamy & Elzanowski (2001), G. Erickson et al. (2001), Padian et al. (2001), Horner & Padian (2004), Horner et al. (2005) and G. Erickson et al. (2009). See also Padian (2012) re Köhler et al. (2012) on relevant findings apropos mammal bone growth patterns, and for lagniappe, one may compare Dalton (2000d), Stokstad (2001c) and Rowe et al. (2001) on the metabolic implications of the problematic Thescelosaurus “heart” fossil of Fisher et al. (2000).
All this is just the tip of a very big inferential iceberg.
Asking whether dinosaurs traveled in migratory herds, like many an active endothermic mammal today, again carried with it presumptions about their underlying biology, their social behavior, and adaptability to changing local conditions. Learning moreover that mammals had coexisted as seemingly trivial denizens of this dinosaur-dominated habitat only added to the mystery of why these wonderfully successful animals had gone extinct at all. A hundred and fifty million years of success, and then poof! Gone forever. How come? Raising this question naturally brought up the issue of patterns, for the dinosaur exit was only the most recent radical gear shifting of life. One system collapses, and the survivors build a new one, only to have it fall apart in turn (albeit many millions of years on). Have the living things that go extinct en mass just “worn out,” reaping the declining fruit from the seeds of their own decay? Or was it more the luck of the draw, mere contingency?
A sample of perspectives suggests how intriguing the issue has been, as well as how difficult it is to resolve from the vantage of many millions of years later: Gore (1989), Eldredge (1991b), J. Erickson (1991), Raup (1991), Whitfield (1993, 182-187), Glen (1994), P. Ward (1994; 2000), Douglas Palmer (1999, 90-91, 126-129, 196-197), P. Ward & Brownlee (2000, 157-188), Gibbs (2001c), Jablonski (2001), Kerr (2001), C. Zimmer (2001g, 143-186) and Becker (2002).
As we’ll see in later chapter modules, the nature and pacing of extinctions (mass and otherwise) and subsequent biological rebounding will figure in a lot of the antievolution debate, but for the moment it’s a good idea to get a few of the highlights on the table up front.