Paleontological Profiles: Jerry Harris

In the first two installments of this series I had the chance to interview two of the most famous paleontologists in the field today, but there are many, many other skilled scientists that you may never have heard of. Dr. Jerry Harris, Director of Paleontology at Dixie State College, is an outstanding scientist (and friend) who has studied a variety of fossil vertebrates from Mesozoic bird tracks to enormous sauropods. Even though I botched some of the questions, Dr. Harris took the time to come up with some excellent responses about his work.

• [Brian Switek] What fascinates you about paleontology? What is it about ancient life that you find so intriguing?

[Dr. Jerry Harris] I actually get that question a lot, and the funny thing is that I don't have a stock answer, largely because the reasons have become myriad as I've progressed in my learning. Obviously, a divining interest in paleontology doesn't usually stem from reasoning like "I like working with people" (though I do!) or "I want to cure diseases" or "I want to invent better technologies" that seem to drive people in other fields. But I'm just fascinated with ancient worlds and ancient life...there's a powerful draw for me (and, I think, for most other paleontologists) in reconstructing and, yes, imagining worlds alien to human experience. That these worlds existed on our own planet - in the same places where humans are today - and that they continually changed through time makes them even more interesting and attractive. For that reason, the interest in dinosaurs that I developed as a child (around the age of two, my mom used to say) has - dare I say it? - evolved into a more general interest in evolution, particularly the products of evolution and the selective pressures that drove them. The interest in dinosaurs obviously hasn't left, though it too has broadened to encompass basically terrestrial ecosystems of the Mesozoic. (Not to belittle Paleozoic or Cenozoic terrestrial (land-based) ecosystems, or marine (ocean-based) ecosystems, of course, since a broad understanding irrespective of time and firmament is important...but one must narrow one's focus sometimes in order to get any actual research done!)

(I have yet to meet a paleontologist that didn't, to some degree or another, love science fiction, and I think that stems from the same love of the different, the alien, the unexperienced. Part of the attraction of paleontology [and, really, much of geoscience] for me is that it does involve imagination. After all, we have a limited data set [although people are continually developing newer and more clever ways to extract information from that set!] consisting of things that no human witnessed when in action, and beyond first- and second-level inferences, one has to be a bit creative, and I love that. Not too many sciences get to be as creative with their end results as paleontologists do, and I think that's part of the draw, at least for me.)

As a paleontologist, I've occasionally (thankfully, not often) encountered people that think that what I do, and where my interests lie, is a waste of time and resources. After all, paleontologists are not curing diseases or inventing better technologies, things that could be reasonably expected to better human lives in the short term. To some extent, I think that capitalism has driven funding more toward those avenues of research that have comparatively short-term benefits and financial returns and away from basic research (others have remarked on this much more extensively). There's nothing wrong (and a lot that's right) with bettering the human experience in one's lifetime, but I think that people have forgotten that basic, fundamental research also has benefits, albeit usually longer-term ones. Who knows what will happen 50, 100, even 500 or more years from now based on a foundation of what knowledge is obtained today, even if we can't possibly imagine it? And, really, it's not that hard to see that a broader paleontological understanding does have shorter term benefits. Our world's climate and environments are changing before our eyes - whether one wants to perceive those changes as anthropogenic or otherwise is irrelevant. We don't have crystal balls through which we can see the future; our only hope of predicting how life on Earth might respond to such changes is by seeing how it has responded in the past. I don't personally work on modern-day climate change, but I can certainly see that any expanded understanding we can get about how life reacts to different kinds of environmental change has modern application. I think more and more people are beginning to get this...I just keep waiting for that understanding to trickle down to the funding end of things...! In the end, I really hope that some of the work I do in my lifetime will create a greater understanding of Earth history and perhaps even to a greater understanding about how we're affecting the world we live in today.

I'd like to explore one more thing in response to your question, just because "What fascinates you about paleontology?" is something I get asked in the guise of "How did you get interested in paleontology?" and as I said, my reasons have changed with time. I honestly don't know what first piqued my interest, not having a lot of memories from when I was two. I can only assume that it had something to do with being given dinosaur toys at some early point, and some of my earliest (and vaguest) memories are of sitting on a floor in the very early '70's playing with plastic dinosaur toys (some absolutely horrific ones, by today's anatomical standards - the ones Marx used to make in the '50's and '60's) and surrounded by gigantic dinosaur wall hangings. My mom always said that I dragged the family to the Field Museum in Chicago (not far from where we lived in Olympia Fields, south of Chicago proper) every other week or so, and somewhere there are pictures of mini-me next to the old "Gorgosaurus" mount that used to be in the atrium, as well as other exhibits. I don't know why children are fascinated by dinosaurs, though I really like Dave Barry's explanation that (paraphrasing) "dinosaurs are much bigger and more powerful than mommy and daddy, and wouldn't have to put up with being told to eat their vegetables or go to bed...they would just flick their tails and swat mommy and daddy through mommy- and daddy-shaped holes in the wall." I think there's a grain of truth in that - the first dinosaurs kids encounter are often some of the most impressive ones - giant theropods and sauropods, huge spiky ceratopsians and stegosaurs, etc. I think, in some ways, they might be a child's first experience with a concept that is so far outside the scope of what they see in their everyday lives that they just demand some attention and awe, and that makes a deep impression. That's a good thing, too, since I think there's a fair amount of evidence that dinosaurs are also a child's first experience with science, and I'd bet that many, many scientists got into science because that impression never really let go of them as they grew up.

• [Switek] For many years illustrators reconstructed dromeosaurs like Deinonychus walking on two toes with one digit held up off the ground. Recently you co-authored a paper with several other scientists on tracks that confirm what had been seen in the skeletal anatomy from not only one but two such dinosaurs. What did you think when you first saw the tracks, and what do the tracks tell us about what these dinosaurs were doing?

[Harris] I've actually not seen the actual tracks in person, though I have seen lots of pictures and have some casts of the tracks. That was a project that I was invited to participate in (in large part because of my involvement with the roadrunner-like Shandongornipes tracks from the same site), and was very happy to do so! When I first saw the pictures and casts, though, I remember kind of staring at them and letting my mind reel with the various implications. It was, as it always is for me in such situations, a great feeling - new data to throw at a problem (well, several, actually) that had been around for quite a while! I love that that's how paleontology works: someone, using what data they had plus a little imagination, concocted an hypothesis, something testable but for which no further data was known, and here someone found a new test for that hypothesis. So it was a thrill to see the Dromaeopodus and Velociraptorichnus tracks, particularly such well preserved ones, and ones in trackways that say more about the behavior that isolated tracks could!

As you say, the tracks support that deinonychosaurs held their second pedal digits aloft while they engaged in locomotion. The trackways show this for at least a slower pace, though I feel safe in generalizing it to apply at faster speeds, too, so I'd say it was likely a habitual posture (sometimes even in death, as body fossils seem to show). This would keep the "sickle claw" on that toe from wearing duller on the ground, as well as prevent it from potentially tripping up the animal by catching on something on the ground. Tracks are great in all sorts of ways like that for testing hypotheses established on body fossil data...too many paleontologists seem to forget (or ignore) that too often, though I think that the track experts like Martin Lockley, Joanna Wright, Brent Breithaupt, Neffra Matthews, Rich McCrea, and Jim Farlow in North America and Hartmut Haubold, Jesper Milàn, Marco Avanzini, Fabio Dalla Vecchia, Christian Meyer, Gerard Gierlinski, and a bunch of people in Spain are doing (and have done) some great work toward making ichnology (the study of trace fossils) more mainstream.

What else were these dinosaurs doing? Well, the trackway segments we've got for Dromaeopodus show that, at least some of the time, the track makers were gregarious - I can't think of a more parsimonious explanation for having several parallel trackway segments. The only other options, really, are to postulate that the track makers (1) wandered along randomly and individually, perhaps at widely separated intervals of time (over the course of a few days, max, based on the sedimentology) and just coincidentally created one area with parallel segments, and that by an even greater coincidence, that's the segment that got preserved; or (2) were restricted by some physiographic barriers. The trackways do seem to have been made alongside a body of water (again, based on the sedimentology), but I'm not positive why that would have restricted them - were the track makers hydrophobic? Was there a dense stand of trees on the other side? Why didn't they move single-file (and leave overlapping tracks)? There's no broader evidence for a local environmental reconstruction at present, so the most parsimonious conclusion is that their tracks don't overlap because they were limited by the body widths of individuals moving parallel simultaneously.

What the track makers might have been doing (other than ambulating, of course...!) while moving as a coherent group is anybody's guess. There's a temptation, I think, to conflate "gregariousness" with "hunting" here - thanks in large part to a recent push from "Jurassic Park" - to want to extrapolate "exciting," "action packed" interpreted behaviors from the tracks. It's something we specifically took pains to denounce both in the paper and with the media because it is not evidence for hunting in packs...just moving in groups, at least on occasion. There's no way to tell from the trackways whether or not the track makers were hunting when they made the tracks, or whether they ever hunted in packs; certainly, the track makers don't seem to have been in any big hurry; nor do they seem to be "stalking" slowly, but who knows? Still, it's an evocative portrait...just one that involves using that imagination to move a bit beyond the actual data. Interestingly, I was introduced to these tracks literally just before a paper came out (Roach, B.T., and Brinkman, D.B. 2007. A reevaluation of cooperative pack hunting and gregariousness in Deinonychus antirrhopus and other nonavian theropod dinosaurs. Bulletin of the Peabody Museum of Natural History 48(1):103-138.) that used some other data and reasoning to hypothesize that deinonychosaurs did not engage in group behavior. Most of what that paper says is justifiable based on the data discussed therein - our data just show otherwise, at least to the extent of being able to say that gregariousness was not an impossibility (and, in fact, occurred, at least on occasion) among non-avian theropod dinosaurs. That, in turn, says interesting things about evolution in that group and about convergent evolution of gregariousness in many different clades and how powerful selective pressures must have been to produce the behavior repeatedly.

• [Switek] You have published work on other footprints as well. Why is it important to study preserved tracks and what can they tell us about the animals that made them?

[Harris] I kind of came to footprints by accident. Initially, I was guilty of being one of those people that didn't give tracks and traces much notice, and understood them largely from "famous" cases like the parallel theropod and sauropod tracks in the Paluxy. But while I was working at the Denver Museum of Nature and Science (then called the Denver Museum of Natural History), I was given the opportunity to work on some peculiar theropod tracks from the Late Cretaceous of Wyoming...these ultimately became known as Saurexallopus in my first-ever scientific publication. In addition to being exciting because they were something previously unknown, those tracks really opened my eyes to what tracks could tell us. I've avoided becoming a track specialist because my interests are broader than that - it's more that I'm not at all adverse to dealing with tracks when they tell interesting stories, and I'm involved in more work along those lines that hopefully will come out soon.

As others have noted, dinosaur skeletons are great - they're certainly among the most striking and evocative fossils that draw people into museums, and I think they're the ones that make the strongest impressions on people (children and adults). But skeletons are from dead animals, even if they were once part of living animals. Tracks and most other trace fossils (ichnites) are rarely made by dead animals - they're generally made by living ones, in the act of behaving in some way. Thus, they directly capture information about how animals lived. Yes, there is plenty of information about living animals to be found in skeletons, too (especially when the animals died in the act of behaving, like the "fighting dinosaurs" pair of Protoceratops and Velociraptor, or the brooding oviraptorosaurs from Mongolia, or the sleeping Mei), but an animal has but one skeleton throughout its life. That same individual can make millions of trace fossils, and it can make them while engaged in all sorts of behaviors. Footprints primarily, but not exclusively, inform about locomotion and locomotory behaviors, which is important for testing against functional morphological and behavioral hypotheses made from the studies of bones. Because an individual can make millions of traces throughout its lifetime, tracks provide an excellent opportunity to examine components of an ecosystem that may not be known from body fossils. Twelve years since I helped first describe them, Saurexallopus tracks still don't have a good body fossil candidate for track maker; neither does Shandongornipes. The former, being Maastrichtian in age, tell us that there was at least one more dinosaur out there for taxon lists of what was going on with dinosaurs just prior to the end of the Cretaceous (though I never see it on such lists, which are invariably body fossil-based) - does this mean that dinosaurs really were declining in this time? The latter tell us a great deal about the ecological, morphological, and size diversities that birds achieved very shortly after Archaeopteryx, but again, in surveys of Mesozoic birds, one rarely encounters mention of the track evidence (although to be fair, Shandongornipes is a bit too new to be on any existing lists...but it's not the only Mesozoic bird track type, either...again, more on this hopefully in the near future!). Even the Dromaeopodus tracks, while confirming something hypothesized previously from body fossils, also mean that there were really sizeable dromaeosaurids running around in the Early Cretaceous of Asia, something not previously known from body fossils. So to sum up, trace fossils complement very nicely the body fossil record by fleshing out our understanding of diversity and of behavior, two of the critical components to understanding what Mesozoic worlds and their "casts of characters" were like.

• [Switek] Several years ago you described the new sauropod Suuwassea emilieae, and you've published several papers on the anatomy of the diplodocid since then. What makes Suuwassea different from other sauropods, and what sort of environment did it live in?

[Harris] Well, Suuwassea wasn't a diplodocid in our analyses...it was a diplodocoid, though. (A mere one letter difference, I know, but with specific phylogenetic implications. I personally hate those kinds of nomenclatural similarities. To avoid those kinds of uncreative proliferations, we named a clade [the Flagellicaudata] that includes the Diplodocidae [Apatosaurus, Barosaurus, Diplodocus, and a few others] and the Dicraeosauridae [Amargasaurus, Brachytrachelopan, Dicraeosaurus]; it turned out that Suuwassea is also in this clade but not clearly either a diplodocid or a dicraeosaurid. Begin rant: I certainly could have done the "Archosauromorpha - Archosauriformes - Archosauria"/"Dinosauromorpha" - "Dinosauriformes" - "Dinosauria" thing with the name, and erected, say, a "Diplodociformes" for the clade, but obviously there's a lot of potential there for confusion, especially where short-hand terms come into play. For example, the term "titanosaur." Does that mean any member of the Titanosauria? Titanosauriformes? Titanosauridae? Could be any of them...if people can't specify "titanosaurian," "titanosauriform," or "titanosaurid" and never say "titanosaur" - and while many people are this careful, many aren't - then better to give the clades names that are unambiguous, IMHO. End rant.)

Anyway, Suuwassea is, in most respects of its anatomy, subtly different from other flagellicaudatans. Its most striking feature (based on the fossils we have of it) is that it has a postparietal foramen on the braincase. Many people have heard of a parietal foramen (sometimes, though erroneously, called the pineal foramen or pineal eye) that many reptiles have; it's a tiny opening in the skull covered with a light-sensitive tissue that provides seasonal and temporal information to the pineal gland, which produces melatonin to regulate various body cycles. No dinosaur has an inarguable parietal foramen, though one has been posited for a few taxa (also primarily sauropods). Dicraeosaurids, though, were long known for having a peculiar postparietal foramen - an opening similar to, though larger than, a proper parietal foramen and lying caudal to where the parietal foramen ought to lie. It does not appear to be associated with the pineal gland, so what it was for is still a mystery. Among sauropods, only the Gondwanan dicraeosaurids were known for this; finding it in a North American sauropod was surprising. Yet in terms of most of the rest of its anatomy, Suuwassea is clearly more conservative and similar to the diplodocids of North America. But there are subtle differences, too, including the shapes and positions of the spinous processes on the cervical (neck) and very distal caudal (tail) vertebrae, the shapes of the humerus (upper arm bone) and tibia (shin bone), and some other elements - enough to justify placing it in its own taxon. Other workers have some different ideas, and I'm eager to see their data and their conclusions documented on that.

But so what? So Suuwassea is another big, dead sauropod from the Morrison Formation - we described it, threw it into a data matrix, yadayadayada - huzzah. Well, one of the things that Suuwassea brought to my attention was that it might be a harbinger of understanding something about the Morrison Formation that wasn't known before, despite the fact that it's a unit that has been studied and producing dinosaurs for over 130 years now. For one, Suuwassea comes from the unit in Montana, and Morrison dinosaurs in Montana have been singularly rare, so much so that some old authors basically declared it unfossiliferous. That may be why it was virtually unexamined until so recently (that and the fact that Montana tends to draw more Cretaceous dinosaur workers because of its absolutely spectacular record of Early and Late Cretaceous fossils). Granted, it was found only a few miles north of the Wyoming border, and of course there were no states or artificial borders when the dinosaurs were milling around there in the Late Jurassic, but still... The fact that it could not clearly be placed into any of the existing Morrison sauropod taxa was interesting...a few other people have tried to erect new Morrison sauropod taxa in relatively recent history (e.g., Cathetosaurus, Seismosaurus, Ultrasauros), but aside from the classic Cope 'n' Marsh taxa, only one has stuck (Supersaurus). So a new Morrison sauropod was interesting...could it be different because of its geography?

People have generally treated the Morrison Formation as "the same everywhere, all the time." Basically, this means that if you wanted to dig a dinosaur out of the Morrison Formation, it wouldn't really matter whether you did it in New Mexico, Colorado, Utah, or Wyoming (the classic states for Morrison dinosaurs) - you'd find pretty much the same animals in all those places, and all of them lived more or less contemporaneously. That's a fair generalization (though still a generalization) based on history - Dinosaur National Monument, Dry Mesa, Morrison, CO, Cañon City, Como Bluff, the Howe Quarry all produce more or less the same set of taxa on a gross level, particularly of dinosaurs. It's certainly an assumption I would have made years ago. But even though Suuwassea is the only one that's been described to date, it's not the only report of a sauropod from the Morrison in Montana (and even northernmost Wyoming) that can't be shoe-horned into an existing taxon. On top of that, most of these reports are of relatively small animals - they're still sauropods and they're still big by human standards, but compared to the sauropods produced from the Morrison in the "classic" areas, they're smaller. So a picture is beginning to emerge that the Morrison might be different in Montana than elsewhere.

Why would this be so? To understand this, one has to go back in time before the Morrison Formation. The basin in which the sediments that would ultimately become the Morrison Formation were deposited was, earlier in the Jurassic, occupied by an extensive, shallow seaway (the Sundance Sea) that came down through Canada from the proto-Arctic ocean. (Don't confuse the Sundance Sea with its more famous, Late Cretaceous parallel, the Western Interior Seaway!) At its maximum extent, in the Middle Jurassic, this sea extended into what is today southern Colorado and southern Utah, but after that, it began to retreat northward again. As it did so, sediment being shed off various mountain ranges to the south and west was no longer dumped into the sea, but deposited on land primarily by river systems, in environments occupied by terrestrial animals, including dinosaurs. This terrestrial sedimentation followed the regressing seaway northward until, ultimately, it started in Montana. By that time, though, terrestrial sediment had been being deposited farther south for quite a long time. It's possible, therefore, that the Morrison in Montana is slightly younger in age than most of the Morrison to the south - this is something I'm working on at present and so won't say more. But in addition to a possible age difference, the Morrison in Montana was closer to the regressing sea. Just as today environments nearer the sea are usually different from those more inland (more humid and less seasonal, for example), it's possible that there were different paleoenvironments in the northern part of this basin than there were in the south, where semi-arid, seasonal environments are pretty well established for the Morrison. The Morrison in Montana does include some indications of this: there are thin coals interbedded with the fluvial (river) deposits there, though all farther north than were Suuwassea came from. So perhaps the Morrison in Montana preserves a somewhat different paleoenvironment, one that was home to a somewhat different fauna than occurs in the south. That's the hypothesis I'm currently working with, and it can be tested in various different ways, but more work on the unit in Montana is called for!

• [Switek] In addition to non-avian dinosaurs, you've also done some research on Early Cretaceous birds. What does the presence of Early Cretaceous birds tell us about the evolution of birds from dinosaurs?

[Harris] Well, the bird fossils we're working on in Gansu Province don't speak directly to the origination of birds from non-avian theropod dinosaurs, but more broadly, Early Cretaceous birds have been very important to fleshing out our understanding of that evolutionary lineage. But it's not their presence that does that - it's their anatomical features that are most informative in that respect. Mesozoic birds have been a passion of mine since I was an undergrad and worked a bit (literature-wise) on my senior thesis, which, in retrospect, was truly awful and demonstrated, if nothing else, that I didn't know Thing One about how to do research! So working on some actual Mesozoic birds has been kind of a dream come true!

Anyway, the evolutionary origin of birds from within the Theropoda is, in my mind, very solidly established - it's easily one of the best evolutionary "transitions" (if such can be said to exist given that boundaries between categories are drawn arbitrarily by humans!) documented in the fossil record, rivaling some of the other long-touted examples, like the evolution of tetrapods with the Sarcopterygii or the evolution of horses from "condylarths"; it's up there with whale evolution for sheer jaw-dropping astonishment as something to present to the public or in classes to exemplify evolution and what it's capable of producing. Bird origins have attained this level of clarity thanks, of course, to the extremely fortuitous discoveries of feathered non-avian theropods (e.g., Sinosauropteryx, Caudipteryx, Protarchaeopteryx, Sinornithosaurus, etc.) and all sorts of basal birds (e.g., Jeholornis, Confuciusornis, Sapeornis, etc.) in the Early Cretaceous of China, followed by a lot of interesting and hard work by a huge number of people.

What's really interesting, though, is that that understanding could have taken a very different, and much earlier, track, had someone pursued one of the earliest discoveries: that of Gansus yumenensis from northwestern China. The holotype of Gansus - just an isolated left ankle and foot - turned up during the course of a paleoichthyological expedition in the Changma Basin in the early 1980's. When the specimen was named and described, its Early Cretaceous age and very modern bird-like morphology were recognized, and at the time, it was one of the more complete pre-Late Cretaceous birds known. Strangely, no one really jumped on the potential of the specimen for filling in what were, at the time, some pretty large "gaps" in our understanding of bird evolution - no one mounted an expedition back to Changma to look for more! I have no idea why this is...it may be that this was, until recently, a relatively remote region, though there is a town there so I imagine there must have been roads. But if someone had undertaken such an expedition, I bet they'd've found the fossils our team now has of Gansus, and the evolution of our understanding of avian origins might have followed a very different path! (Same conclusions, though.)

The primary importance of Gansus is not what it says about the evolution of birds from non-avian theropods, but what it says about the diversity of Early Cretaceous birds and the rates of evolution of many of the characteristic features of modern birds. The facts that (1) it has so many "modern" characteristics, (2) it lived in a world that, as far as we can currently tell, was dominated by enantiornithean ("opposite") birds, and (3) lived somewhere around 30-35 million years after Archaeopteryx collectively tell us that the avian lineage to which it belongs (the Ornithurae) was undergoing relatively rapid evolution during this time. Of course, I feel compelled to be a good li'l scientist and note the caveats on that! For one, the outcome of our initial analysis has yet to be confirmed - it was, after all, based just on five specimens, none of which was complete (and none of which had a skull or most of the cervical vertebrae) and which were exposed in a restricted number of views, so we didn't have as much data as possible to plug into a matrix and run an analysis. But we have literally dozens of other new specimens now, too, that we hope will rectify all these problems and enable us to provide the most detailed anatomical description of any Cretaceous bird and give us more resolution on the phylogenetic issue. That number of specimens will also enable to us to do some really good histological analysis because we can examine the same element for multiple specimens, something that's only been done for Confuciusornis among Mesozoic birds. One of our other primary research goals (of a long list!) is to get a better handle on the age of the bird and the strata from whence it came - we're fairly certainly that it's late Early Cretaceous, but we'd like to have something more specific. We're in the midst of seeking grant funding for this, and we've got a lot of really talented and wonderful people on board to help!

• [Switek] During your career you have conducted research on a variety of ancient creatures from a range of locations and time periods, from theropods like Acrocanthosaurus to phytosaurs to sauropods. Do you have a favorite fossil creature (or group of fossil creatures)?

[Harris] (laughs) Actually, no. Like I mentioned above, Mesozoic birds have been kind of a passion, but I don't have a particular favorite. Because my interests have become so broad, I've developed a real appreciation for...well, just about everything! All fossils have potential uses, whether it's in studying biostratigraphy, paleobiogeography, paleoecosystems, and/or evolution. But in the course of various of my projects (both fossil prep and research), I've had the good fortune to encounter all sorts of things - the ones you mention, basal crocodylomorphs, and even invertebrates, like ostracodes, conchostracans, insects, and palynomorphs. Though overlooked by a lot of vertebrate paleontologists, they are really very important components when trying to understand a holistic picture of what's going on in any place or any point in time. I've also come to appreciate how little is actually known about some of these organisms - maybe that's because they're just not as glamorous as the vertebrates - when was the last time you heard some child begging their parents to take them to the museum to see the ostracodes? - but any budding paleontologists out there looking for a real challenge and niche that will make their services be "in demand" and give them innumerable publication opportunities, take a close look at these things - for instance, conchostracan systematics and evolution aren't at all well understood, yet they are given great importance in things like terrestrial biostratigraphy and correlation. If they co-occur with dinosaurs and other vertebrates, and if the vertebrates themselves don't provide good information about, say, biostratigraphy or paleobiogeography, understanding the "less impressive" components of the ecosystem becomes extremely helpful! ...Anyway, while dinosaurs form the core of my interests, and they're still where I've been focusing my research efforts, I can't say that I have a particular favorite organism or group of organisms - I've had fun with just about everything I've been involved with!

• [Switek] Finally, paleontology is a very active and diverse field with a rich history. Is there any paleontologist, past or present, who has served as an inspiration in your own work?

[Harris] Although my interest in dinosaurs and fossils began early, I really don't have any recollections of being aware of the names or identities of various paleontologists as a child - I'm sure I must have read names like Cope, Marsh, Osborn, Lull, Andrews, Colbert, etc., but I don't recall that those names, or those personages, made any real impression on me - I was more interested in the animals than their discoverers. Maybe that was a flaw of the authors of the books I read in not playing those up enough; I don't know. But my point is that early on, there wasn't a particular paleontologist that I wanted to emulate. I went through a brief period circa junior high when my interest in paleontology waned and other interests received more serious consideration as career paths, but it was when I was in high-school, during a visit to the University of Colorado at Boulder, where one of my step-brothers was a student, that my interest in dinosaurs and paleontology was re-ignited. My step-brother was giving the family a campus tour, and that included their small museum. This was at a time when Bob Bakker still hung up his shingle there, and the exhibit was largely his and patterned after much of his book (The Dinosaur Heresies). Though small, the exhibit was enough to teach me that most of what I had learned of dinosaurs earlier in life may have been not just wrong, but radically wrong. That was intriguing; the small gift shop had (of course) his book for sale, which I got and read. So, like a lot of paleontologists of my generation, I guess I can say that it was that book that really pulled me into paleontology as a career.

Toward the end of my own student tenure at Boulder, I began volunteering at the Denver Museum, where I came under the tutelage of Ken Carpenter, and it was Ken that showed me the paleontological ropes in terms of fieldwork, research, exhibitry, and fossil prep. So he's been kind of my paleontological "father" and one of my biggest influences and inspirations. While at Denver, I also had the good fortune to do some work with and learning from Bryan Small, Kirk Johnson and Richard Stucky, too, and I got to know many other people there that started as volunteers and have since moved on to their own successful paleontological careers, like Jeff Martz, Virginia Tidwell, and Lorrie McWhinney. At Boulder, I had many classes with Judith Harris (no relation) and Peter Robinson. Since then, I've been very fortunate to learn from many other prominent paleontological figures, like Lou Jacobs, Bonnie Jacobs, Dale Winkler, Alisa Winkler, Tony Fiorillo, Spencer Lucas, Tom Williamson, Gary Morgan, Andy Heckert, Kate Zeigler, Peter Dodson, Ken Lacovara, Josh Smith, Matt Lamanna, Mandi Lyon, Hailu You, Allison Tumarkin-Deratzian, Barb Grandstaff, Jim Kirkland, Luis Chiappe, and a vast number of others (both paleontologists and not) that, for the sake of brevity, I'll leave off. From each and every one of them I've learned interesting and very useful perspectives about various aspects of paleontology, and I like to think that my tendency to apply holistic approaches to any paleontological problem is the combined result of everything that all these people have taught me (and continue to teach me). So even though it probably sounds cliché, they've all been inspirations and continue to be inspirations. If I'm ever even half as smart and successful as these people have been, I'll consider myself very lucky indeed...!