This was a very special week for many of us, as the most famous paleontologist, Professor John “Jack” Horner, visited Singapore to open the Science Centre’s latest exhibition Titans of the Past.
Titans of the Past tells a story through time, from the era of the dinosaurs, with “The Growth and Behaviour of Dinosaurs” segment in collaboration with The Museum of the Rockies and animatronics from Kokoro in Japan that showcases real fossils including MOR008, the world’s largest Tyrannosaurus rex skull that measures 59 inches long from its snout to the back of its skull. This is even larger than Sue from The Field Museum in Chicago, whose skull is 55.4 inches long. It also features a skull growth series that evidences the ontogeny of the Triceratops and evidences Prof Horner’s hypothesis that Triceratops and Torosaurus were in fact the same animal. The second segment, organized in collaboration with Aurea Exhibitions, features life-sized cast of an Argentinosaurus, a Giganotosaurus, and a T-rex. In the final segment, “Ice Age, The Exhibition”, visitors will marvel at animatronic mammals from the Ice Age including a mammoth, a mastodon, and a saber-toothed tiger.
As the world’s most famous preeminent paleontologist, Prof Horner is a legendary superstar who needs little introduction. He is Regents Professor of Paleontology at Montana State University, Curator of Paleontology at the Museum of the Rockies, recipient of the MacArthur Fellowship “Genius Grant”, technical advisor to Steven Spielberg for the Jurassic Park franchise, and inspiration to author Michael Crichton for the lead character Dr. Alan Grant. Perhaps even more than that, Prof Horner’s personal story of how he achieved the epitome of success in spite of his dyslexia has been incredibly inspiring. In his inimitable style, Prof Horner gave a special Science in the Café talk on “Why Some Dinosaurs had Horns, Frills and Crests on their Heads”.
Here is a summary of his arguments:
Dinosaurs have evolved to become birds. In the past, dinosaurs were portrayed as slow, unintelligent, cold-blooded reptiles. However, the fossil record has shown over 100 characteristics that dinosaurs shared with birds, such as being warm-blooded, feathered, having wishbones, hollow bones, oblong eggs, hard-shelled eggs, and sharing similar growth phases.
Dinosaurs were social. The largest concentration of dinosaur fossils is a monospecific bone bed of an estimated 115,000 skeletons averaging 30 bones per square meter for two square kilometers in North-Central Montana. This mass mortality of a single species show that duckbill dinosaurs lived in large herds, and needed to migrate frequently as the large size of their herd would have continually exhausted the vegetation in each area they travel to.
Dinosaurs cared for their young. One of Dr Horner’s earliest discoveries was dinosaur nests in the Western Hemisphere, as well as the first dinosaur embryos. These were of the Maiasaura species he discovered and named. Cutting into the bones of Maiasaura juveniles still congregating in a nest, he learnt that their bone structure was not fully ossified, with relatively soft and spongy ends made of cartilage that would not have allowed them to move out of the nests. This nest-bound behavior for grown, 3-feet long juveniles (hatchlings were only 12 inches long) indicated that their mothers would have stayed on to feed them even after their birth.
Dinosaurs changed their appearances as they matured. One of Dr Horner’s research approaches is to collect many of the same species, so as to study the developmental differences across specimens when they age (as indicated by the growth rings in their bone). He has amassed a growth series of over 100 Triceratops specimens of all ages, which evidence bone deposition and resorption in the horns, frills, crests, and spikes of Triceratops as they mature to dramatically change their appearances over time. These not only demonstrated that there were in fact fewer species of dinosaurs than previously thought, but also that dinosaurs’ physical appearances changed as they grew. For instance, he postulated that the Dracorex hogwartsia, the Stygimoloch, and the Pachycephalosaurus were the juvenile, sub-adult, and adult variations of the same dinosaur species. This indicated that the change in appearance could have been to signal maturity to their caregiving parents.
Physical features mostly likely as a signal to parents. Prof Horner believes that the dinosaurs’ horns, frills, crests, and spikes were not for combat, as birds are visual creatures who rely on display rather than physical attacks. Triceratops postorbital horns for instance hollowed out internally at the base, which would have rendered them unsuitable for territorial clashes.
It was also unlikely that the horns were used as defense from predators, as the changed in orientation as they matured. Postorbital horns are straight as babies, curved posteriorly in juveniles, straightened in subadults, and recurved anteriorly in adults.
Because there is no evidence for sexual dimorphism, i.e. male and female Triceratops horn features were not differentiated, it is also unlikely that they were used for sexual attraction.
Prof Horner argues that it is most likely that these features changed as dinosaurs attained sexual maturity, in order to visually signal to adults that they no longer required caring. This is similar to how modern birds such as the Cassowary only form their crest when they are 80% into adulthood, dinosaurs retained juvenile characteristics in their bone structures so they would be cared for by adults.
In person, Prof Horner turned out to be really passionate, informed, and humorous. After a lifetime of collecting fossils, his eyes still light up when he talks about dinosaurs. He backs up his theories with hard evidence, and despite his self-effacing charm you can tell that it is his contrarian opinions that have been really pushing the envelope in paleontology. Best of all, he is incredibly nice. He was gracious to stay till the very last visitors (our group!) left, generously answering all our questions, and signing autographs on our books, fossils, and memorabilia. We also got to meet his lovely researcher Vanessa, who very kindly helped to identify this fossil as a rarer Stygimoloch spike rather than a Pachycephalosaurus on the basis of its provenance and longer size. What a day!
The Titans of the Past exhibition at the Science Centre is open from 25 October 2013 to 23 February 2014, with admission charges at $25 for adults and $19 for children.