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Dr. Jack Horner is one of the most recognized paleontologists working in the field today, and is presently the Ameya Preserve Curator of Paleontology and Montana State University Regents’ Professor of Paleontology. He has authored numerous books, papers, and popular articles, and during his career has named the dinosaurs Maiasaura peeblesorum, Orodromeus makelai, Hypacrosaurus stebingeri, Prosaurolophus blackfeetensis, Gryposaurus latidens, and Brachylophosaurus goodwini, although he is probably most well-known for his studies of the eggs & young of Maiasaura. This week I had the chance to ask Dr. Horner about his work and thoughts about dinosaurs;
- [Brian Switek] What first inspired you to become a paleontologist, and what keeps you going back into the field year after year?
[Dr. Jack Horner] Near as I can remember, I was born wanting to be a dinosaur paleontologist. This will be my 40th consecutive year in the field. Every specimen I find generates the same amount of excitement as I experienced the first time I found a dinosaur, and regardless of how many I find representing a single species (ie: Triceratops or Maiasaura), I still feel the same excitement. Every new specimen offers something new.
- [Switek] In your book Dinosaur Lives you wrote “A dinosaur out of context is like a character without a story. Worse than that, the character suffers from amnesia.” In terms of ecological context, what was the Upper Cretaceous of Montana like during the time that dinosaurs such as Maiasaura lived?
[Horner] First off, that quote is in reference to specimens taken from the field before the proper scientific studies have been completed.
As for the ecology of Maiasaura, there are clearly different scenarios for the different ages of individuals. Maiasaura hatched out of their eggs in the confines of bowl-shaped mud nests, and remained in these nest-like structures until they had more than doubled their hatchling size. The nests we’ve found were on the over-banks of small streams, and these streams flowed into shallow lakes. The streams and lakes were surrounded by various conifers, and low-growing bushes. Volcanoes existed some 50 miles to the south of the nesting ground, and the Cretaceous Intercontinental Seaway was approximately 300 miles to the east. the newly forming Rockies were about 20 miles to the west. Tropical storms, possibly even hurricanes tracked northward from the Gulf of Mexico, causing devastation along the coastal plain. An aggregation of several thousand Maiasaura adults and juveniles were killed in either a storm such as this, or possibly a catastrophic eruption of the nearby volcano. A bonebed of Maiasaura containing thousands of their bones attests to this event.
- [Switek] In 1978 you discovered a number of skeletons of baby Maiasaura, sparking a major change in what was known about dinosaur reproduction. What was early life like for a baby Maiasaura, and how might it have differed from the early lives of some of the theropods like Troodon that lived nearby?
[Horner] Unfortunately taphonomic information doesn’t provide this kind of data. Maiasaura nested along rivers, and Troodon nests are found on what is interpreted as islands and the shore of the lakes. Maiasaura and Troodon both died in the catastrophic event.
- [Switek] In many documentaries and in your book The Complete T. rex you suggest that Tyrannosaurus was more of a scavenger than a hunter. Bob Bakker and other paleontologists advocate that Tyrannosaurus was an active predator. Do you think that our understanding of the paleobiology of the massive theropod has benefited from this debate, and what are your current thoughts about the habits of the famous dinosaur?
[Horner] Scientific inquiry is about method rather than conclusions. When we “do” science we create hypotheses based on physical evidence, and then attempt to falsify these hypotheses by discovering contrary evidence. Science is about falsification, not verification. As an educator, my primary job is to show people, including kids, how science works, so that they too can then search for contrary evidence. I also teach kids that if they are only interested in being right, then science is the wrong field to go into. If they are interested in finding the right answer, then it is likely that they will be often wrong. I also teach people that most preconceived ideas are wrong, because they are seldom based on physical evidence.
So, as there was never any physical evidence provided to support an actual hypothesis that T-rex was an active predator, we should, as good scientists begin our search without any preconceived ideas. In other words we should begin by asking how did T-rex acquire its meat?
What I did was to make a comparison of a T-rex skeleton with that of a Velociraptor, since we have pretty good evidence (from the fighting dinosaurs of Mongolia) that Velociraptor was a predatory dinosaur. We don’t however, have any direct evidence such as this for any other meat-eater. And, we should not assume that all meat-eaters were necessarily predators, because scavenging is certainly an option.
Comparing T-rex with Velociraptor, virtually all characters are the opposite of one another. T has short arms, V has long arms, T has long femur/short tibia, V has short femur/long tibia, T has large olfactory, V has small olfactory, T has bone-crushing teeth (and gains them during ontogeny), and V has bladed-shaped meat-slicing teeth, T is common in its ecosystem, and V is rare.
The opposite characters suggest that T-rex is doing something very different from Velociraptor, and its bone crushing teeth suggest it was likely a scavenger. Suggesting that it was both would not be falsifiable, but hypothesizing that it is 100% scavenger can likely be falsified if incorrect. Personally, I don’t care how T-rex got its meat, but I do care that kids understand how we do science. I also care that they realize that opinions are not scientific even if they are the opinions of scientists. Physical evidence is the most important ingredient in science. Parsimony is the second most important! The simplest (least number of steps) explanation based on the physical evidence? The third most important is phylogeny. Dinosaurs are related to extant birds and crocodilians, and so our initial explanations should be based on related taxa. Some birds are exclusive scavengers, so its not complicated to suggest that T-rex was an exclusive scavenger.
- [Switek] At the last SVP meeting in Texas, you, Holly Woodward, and Mark Goodwin proposed that the pachycephalosaurs Stygimoloch and Dracorex were really juvenile representatives of Pachycephalosaurus (an idea that Bob Bakker has also recently challenged). Can you elaborate on the similarities that led you to this hypothesis?
[Horner] I’ve known Bob for many years, and like him a lot. He’s a very bright guy, but in this case especially, he’s just not thinking ontogenetically. Dinosaurs change as they grow up, and some of them change drastically. Crested duck-billed dinosaurs are a clear case of this, as is the extant dinosaur Cassowary. Cassowary doesn’t acquire its crest until the skull of the bird is 80% adult size. That means that a juvenile and adult look very different from one another, and can be almost identical in size.
Dracorex, Stygimoloch and Pachycephalosaurus specimens vary in size from Dracorex being the smallest, Stygimoloch second, and Pachycephalosaurus, the largest. On top of that the cranial ornamentations of these three taxa are identical except for the size of the sqaumosal spikes and the dome. Bob states in his interview that Triceratops didn’t have any “reversals” where the bone grew to a particular size and then reversed getting smaller, but that is not true, for as I showed in my SVP talk, Triceratops eppocipitals do in fact grow from small triangular shapes to large triangular shapes, and then reduce to flatten against the frill. You can see this shape change in a paper Mark Goodwin and I have just published in the new JVP.
We have evidence, based on histological sections of several spikes, that the spikes did in fact increase in size, and then reduce in size, with spike reduction corresponding to the enlargement of the dome. And, there is more of this cranial shape change in these animals that I cannot tell you about at this time, as the paper is soon to go to review. This is also true of Triceratops. Cranial shape change was extreme in the marginocephalian dinosaurs, and it all has to do with the extraordinary kind of bone tissue that makes up their skulls. Not at all like the tissues that make up the skulls of mammals.
As an added piece of information, on account of the extraordinary cranial bone tissues, pachycephalosaur skulls would have shattered had they butted heads. These dinosaurs most likely had vertebral locks to help hold up their heavy heads, for these animals have the heaviest, densest bone of any animal we have on record.
- [Switek] In addition to writing several books and appearing in countless documentaries, you’ve also advised the production teams for all the Jurassic Park films about dinosaurs. Is it difficult being such a well-known paleontologist, balancing your technical work with popularizing paleontology?
[Horner] Nope, its all the same thing, its all about education. I’m very happy that so many people are as interested in dinosaurs as I am.
- [Switek] Many of the readers of this blog are students hoping to be professional paleontologists themselves someday. Do you have any advice for college students who want to pursue a career in paleontology?
[Horner] Strive to be a good, objective scientist, understanding that if you are indeed more interested in being right than in having the right answer, you should go into politics. Also, keep in mind that a paleontologist needs to always be thinking in terms of stratigraphy, taphonomy, phylogeny and ontogeny. And of course, about education. The most important character you can possess if you really want a paleontology career is passion. You have to be passionate about your endeavor because there is a lot of competition. Be the best, and you will get the best job!
- [Switek] Paleontology is a field that is rich in history and colorful personalities. Is there any paleontologist, past or present, that has served as an inspiration for your own work?
[Horner]When I was a little kid I had the book All About Dinosaurs by Roy Chapman Andrews, and always wanted to go to Mongolia to help find the dinosaur eggs, and see the double-humped camels, and walk around the Flaming Cliffs.
Now, fifty years later, after having been there many times, we’ve built a preparation laboratory there, and I have two Mongolian graduate students, and a Mongolian Post-Doc. I feel like I have had a part in helping the Mongolians create their own paleontology research and education projects so that when future kids read books about Mongolian dinosaurs, they will want to be like the Mongolian scientists, rather than like some American or other foreigner.
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