Dr. Thomas R. Holtz, Jr., Univeristy of Maryland
Specialist in theropod paleobiology, with special concentration on/obsession with/affection for the Tyrannosauroidea
1. What first got you interested or involved in your research field?
As a young kid (about 3 years or so) I got two different toy dinosaurs: a Tyrannosaurus and a “Brontosaurus“. I asked my mom what they were, and she said “dinosaurs”. I apparently was very skeptical, because how could these two animals which looked SO different from each other both be called the same thing, when horses and cows (which looked a lot more similar) had their own names. So she bought a copy of the How and Why Wonderbook of Dinosaurs and read to me from it. At that point I decided I would grow up to be a dinosaur. Somewhat later (when my parents convinced me that this was not going to happen), I decided I would be a paleontologist.
2. What is your favourite piece of research?
I think my favorite pieces of research include: establishment under a phylogenetic context that tyrannosaurs were coelurosaurs (already suggested since the early 20th Century, and independently developed by Currie, Novas, and Sereno while I was doing my work); functional anatomy of the arctometatarsus (again there had been previous work on the subject, but by giving the structure a name it seems to have attracted more rigorous studies (e.g., various papers by Eric Snively); and the critical analysis of the obligate scavenging hypothesis for Tyrannosaurus and kin.
3. What do you think is the most interesting or important discovery in your field in recent years?
Feathers. Feathers galore. Feathers on fairly basal coelurosaurs, and maybe deeper. (However, I would also say that work on growth rates in dinosaurs and the revolution in studies of respiration and air sacs in archosaurs are also revolutionary for the field).
4. What do you think is the biggest unanswered question in your field right now?
How basal were feathers? Or, to put this a different way, are the elements in Tianyulong, coelurosaurs, and/or pterosaur pycnofibres homologous? Towards this end, dinosaur fossils in lacustrine or lagoonal deposits of the Late Triassic and Early Jurassic are greatly to be desired!
5. What advice would you give to students about research?
So many important things to suggest here…
One: Read the older literature! Just because a work wasn’t published since 2000 doesn’t mean that it doesn’t have great observations.
Two: Don’t be afraid to be wrong. Science is all about reducing the error bars over time, so don’t expect the first paper in a field to be the last word!
Three: Always keep in mind: if you were wrong, how would you know it? In other words, be clear as to what your hypotheses really are.
and a big one:
Four: Read outside your field! Be aware of research done in other disciplines, from functional anatomy to sedimentology and stratigraphy to ecology and so forth. Don’t get pigeon-holed into a single particular topic.
Dave Hone's Archosaur Musings 
“Read the older literature! Just because a work wasn’t published since 2000 doesn’t mean that it doesn’t have great observations.” <– THIS.
And also just because it was published recently / in a ‘good’ journal, doesn’t mean it isn’t wrong.
Big thanks to both you and Dr. Holtz! Great article. I thought this series would be good and I was right.
Question for Dr. Holtz: Do you think tyrannosaurs were active predators or obligate scavengers? I’m aware active predators usually scavenge whenever they get the opportunity, so “predation plus scavenging” falls under “predation” to me. Along with “bully smaller predators and steal kills.”
Tom wrote an entire paper basically saying that T. rex was most likely both predator and scavenger as indeed are almost all modern carnivores. I assume his position’s not changed in the last couple of years so I feel safe answering for him. 😉
Dr. Holtz, thank so very much for providing new information to questions about research and other topics students should read about, I will keep your advice in mind.
I would agree with you the feathers in dinosaurs are some of the most important discoveries in recent years. So with the discovery of Yutyrannus, do you think Tyrannosaurus rex and other large theropods should be restored with feathers? Or do think there is still not enough evidence to support a possible plummed t-rex?
Sorry for the delay in replying. In answer to the scavenger/hunter issue: yes, I stand by my 2008 analysis.
As for plumage: in my opinion, the case is extraordinarily strong for plumage of some sort on even a full grown T. rex. We don’t have–and are unlikely to get–direct physical evidence for this, as no one has yet discovered extremely fine-grained lake deposits like those in which Yutyrannus was preserved from the Hell Creek or other latest Maastrichtian western North American units (i.e., the places Tyrannosaurus lived). So far the types of skin impressions from Hell Creek dinosaurs that have been described are from sediments too coarse to record the presence of feathers, so they do not represent evidence against them.
The question, however, is to what degree were big T. rex feathered. One could argue for a very sparse covering (like the hair on a modern elephant), or limited to certain regions (a mane or crest or the like). But on the flip side, Yutyrannus seems to have been fairly shaggy at 1/6th T. rex size, and giant ground sloths like Megatherium and Eremotherium got by as shaggy animals in tropical environments. So a shaggy Tyrannosaurus is certainly an acceptable hypothesis.