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Thomas R. Holtz Jr.


Vertebrate Paleontologist
Principal Lecturer


Megalosaurus bucklandii, the first non-bird dinosaur recognized by Science. July 2016.

"There is nothing like geology; the pleasure of the first day's partridge shooting or first day's hunting cannot be compared to finding a fine group of fossil bones, which tell their story of former times with almost a living tongue." Charles Darwin, letter to his sister Catherine, 1834

Pedal (foot) claw of the latest Cretaceous oviraptorosaur Anzu. July 2013, near Ekalaka, MT

Department of Geology
8000 Regents Drive
University of Maryland
College Park, MD 20742

Faculty Director, Science & Global Change Program College Park Scholars
Faculty Director, former Earth, Life & Time Program College Park Scholars
2019 Provost's Excellence Award for Professional Track Faculty in Teaching

Adjunct Faculty, Behavior, Ecology, Evolution, Systematics Program
Research Associate, Department of Paleobiology, National Museum of Natural History, Smithsonian Institution
Member, Scientific Council, Maryland Science Center

Email: tholtz@umd.edu
Phone: (301) 405-4084 or (301) 405-6965
Fax (Geology): (301) 314-9661
Geology Office: 1225B Chemistry Building
Scholars Office: 1216 Centreville Hall
Mailing Address:

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Training Jurassic World raptors, Chris Pratt-style. June 2015

Current CV

Research Interests

Education

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Felis catus, with Homo sapiens for scale. July 2017.
Courses Taught at UMCP
Societies

ORCID: 0000-0002-2906-4900

Recent Publications

  • Dececchi, T.A., K.S. Kim, M.G. Lockley, H.C.E. Larsson,T.R. Holtz, Jr., J.O. Farlow & M. Pittman. 2024. Theropod trackways as indirect evidence of pre-avian aerial behavior. Proceedings of the National Academy of Sciences 121: e2413810121. doi: 10.1073/pnas.2413810121
  • Caspar, K.R., C. Gutiérrez-Ibáñez, O.C. Bertrand, T. Carr, J.A.D. Colbourne, A. Erb, H. George, T.R. Holtz, Jr., D. Naish, D.R. Wylie & G.R. Hulburt. 2024. How smart was T. rex? Testing claims of exceptional cognition in dinosaurs and the application of neuron count estimates in palaeontological research. The Anatomical Record 307: 3685-3716. doi: 10.1002/ar.25459
  • Surring, L.A., M.E. Burns, E. Snively, D.E. Barta, T.R. Holtz, Jr., A.P. Russell, L.M. Witmer & P.J. Currie. 2022. Consilient evidence affirms expansive stabilizing ligaments in the tyrannosaurid foot. Vertebrate Anatomy Morphology Palaeontology 10: 49-64. doi: 10.18435/vamp29387
  • Carr, T.D., J.G. Napoli, S.L. Brusatte, T.R. Holtz, Jr., D.W.E. Hone, T.E. Williamson & L.E. Zanno. 2022. Insufficient evidence for multiple species of Tyrannosaurus in the latest Cretaceous of North America: a comment on "The Tyrant Lizard King, Queen and Emperor: multiple lines of morphological and stratigraphic evidence support subtle evolution and probable speciation within the North American genus Tyrannosaurus Evolutionary Biology (2022). doi: 10.1007/s11692-022-09573-1
  • Hone, D.W.E. & T.R. Holtz, Jr. 2022. Comment on: Aquatic adaptation in the skull of carnivorous dinosaurs (Theropoda: Spinosauridae) and the evolution of aquatic habits in spinosaurids. 93: 275-284. Cretaceous Research 134: 104152. doi: 10.1016/j.cretres.2019.05.010
  • Holtz, T.R., Jr. 2021. Theropod guild structure and the tyrannosaurid niche assimilation hypothesis: implications for predatory dinosaur macroecology and ontogeny in later Late Cretaceous Asiamerica. Canadian Journal of Earth Sciences 58: 778-795. doi: 10.1139/cjes-2020-0174 [A non-formatted Open Access version of the final paper and its supplementary data is available here]
  • Hone, D.W.E., and T.R. Holtz, Jr. 2021. Evaluating the ecology of Spinosaurus: shoreline generalist of aquatic pursuit specialist? Palaeontologia Electronica 24(1): a03. doi: 10.26879/1110
  • Dececchi, T.A., A.M. Mloszewska, T.R. Holtz, Jr., M.B. Habib, and H.C.E. Larsson. 2020. The fast and the frugal: divergent locomotor strategies drive limb lengthening in theropod dinosaurs. PLoS ONE 15(5): e0223698. doi: 10.1371/journal.pone.0223698
  • Naish, D., A. Cau, T.R. Holtz, Jr., M. Fabbri, and J.A. Gauthier. 2020. Theropoda O.C. Marsh 1881 [D. Naish, A. Cau, T.R. Holtz, Jr., M. Fabbri, and J.A. Gauthier], converted clade name. Pp. 1235-1246. In K. de Queiroz, P.D. Cantino, and J.A. Gauthier (eds.), Phylonyms: A Companion to the PhyloCode. CRC Press.
  • Snively, E., H. O'Brien, D.M. Henderson, H. Mallison, L. Surring, M.E. Burns, T.R. Holtz, Jr., A.P. Russell, L.M. Witmer, P.J. Currie, S.A. Hartman & J.R. Cotton. 2019. Lower rotational inertia and larger leg muscles indicate more rapid turns in tyrannosaurids than in other large theropods. PeerJ 7: e6432. doi: 10.7717/peerj.6432
  • Holtz, T.R., Jr. 2018. Evolution: New branches on the alvarezsaur tree. Current Biology 28: R941-R943.
  • Holtz, T.R., Jr. 2017. Nomenclature: Share names for dinosaur divisions. Nature 545: 30.
  • Hone, D.W.E. & T.R. Holtz, Jr. 2017. A century of spinosaurs - a review and revision of the Spinosauridae with comments on their ecology. Acta Geologica Sinica 91: 1120-1132. doi: 10.1111/1755-6724.13328
  • Brusatte, S.L., T.D. Carr, T.E. Williamson, T.R. Holtz, Jr., D.W.E. Hone & S. A. Williams. 2016. Dentary groove morphology does not distinguish 'Nanotyrannus' as a valid taxon of tyrannosauroid dinosaur. Comment on: "Distribution of the dentary groove of theropod dinosaurs: Implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988". Cretaceous Research 65: 232-237. doi: 10.1016/j.cretres.2016.02.007
  • Plotnick, R.E., J.M. Theodor & T.R. Holtz, Jr. 2015. Jurassic Pork: What could a Jewish Time Traveler eat? Evolution: Education and Outreach 8:17. doi: 10.1186/s12052-015-0047-2
  • Holtz, T.R., Jr. 2014. Palaeontology: Mystery of the horrible hands solved. Nature 515: 203-205. doi:10.1038/nature13930
  • Farlow, J.O., T.R. Holtz, Jr., T.H. Worthy & R.E. Chapman. 2013. Feet of the fierce (and not so fierce): pedal proportions in large theropods, other non-avian dinosaurs, and large ground birds. Pp. 88-132, in J.M. Parrish, R.E. Molar, P.J. Currie, and E.B. Koppelhus (eds.) Tyrannosaurid Paleobiology. Indiana University Press.
  • Brett-Surman, M.K., T.R. Holtz, Jr. & J.O. Farlow (eds.) 2012. The Complete Dinosaur. 2nd Edition. Indiana University Press. 1112 pp.
  • Holtz, T.R., Jr. 2012. Dinosaur hunters of the Southern Continents. Pp. 107-118, in M.K. Brett-Surman, T.R. Holtz, Jr. & J.O. Farlow (eds.) 2012. The Complete Dinosaur. 2nd Edition. Indiana University Press.
  • Holtz, T.R., Jr. & M.K. Brett-Surman. 2012. The osteology of dinosaurs. Pp. 135-149, in M.K. Brett-Surman, T.R. Holtz, Jr. & J.O. Farlow (eds.) 2012. The Complete Dinosaur. 2nd Edition. Indiana University Press.
  • Holtz, T.R., Jr. & M.K. Brett-Surman. 2012. The taxonomy and systematics of the dinosaurs. Pp. 209-223, in M.K. Brett-Surman, T.R. Holtz, Jr. & J.O. Farlow (eds.) 2012. The Complete Dinosaur. 2nd Edition. Indiana University Press.
  • Holtz, T.R., Jr. 2012. Theropods. Pp. 346-378, in M.K. Brett-Surman, T.R. Holtz, Jr. & J.O. Farlow (eds.) 2012. The Complete Dinosaur. 2nd Edition. Indiana University Press.
  • Holtz, T.R., Jr. 2008. A critical re-appraisal of the obligate scavenging hypothesis for Tyrannosaurus rex and other tyrant dinosaurs. Pp. 370-396, in P. Larson and K. Carpenter (eds.), Tyrannosaurus rex: The Tyrant King. Indiana University Press.
  • France, C.A.M., P.M. Zelanko, A.J. Kaufman & T.R. Holtz. 2007. Carbon and nitrogen isotopic analysis of Pleistocene mammals from the Saltville Quarry (Virginia, USA): Implications for trophic relationships. Palaeogeography, Palaeoclimatology, Palaeoecology 249: 271-282.
  • Holtz, T.R., Jr. 2006. Palaeontology: A Jurassic tyrant is crowned. Nature 439: 665-666.
  • Holtz, T.R., Jr. & H. Osmólska. 2004. Saurischia. Pp. 21-24, in D.B. Weishampel, P. Dodson and H. Osmólska (eds.), The Dinosauria. Second Edition. University of California Press.
  • Holtz, T.R., Jr., R.E. Molnar & P.J. Currie. 2004. Basal Tetanurae. Pp. 71-110, in D.B. Weishampel, P. Dodson and H. Osmólska (eds.), The Dinosauria. Second Edition. University of California Press.
  • Holtz, T.R., Jr. 2004. Tyrannosauroidea. Pp. 111-136, in D.B. Weishampel, P. Dodson and H. Osmólska (eds.), The Dinosauria. Second Edition. University of California Press.
  • Holtz, T.R., Jr., R.E. Chapman & M.C. Lamanna. 2004. Mesozoic biogeography of Dinosauria, Pp. 627-642 in D.B. Weishampel, P. Dodson and H. Osmólska (eds.), The Dinosauria. Second Edition. University of California Press.
  • Holtz, T.R., Jr. 2003. Dinosaur predation: evidence and ecomorphology. Pp. 325-340, in P.H. Kelley, M. Kowalewski and T.A Hansen (eds.), Predator-Prey Interactions in the Fossil Record, Topics in Geobiology Vol. 20. Kluwer Press.
  • Farlow, J.O. & T.R. Holtz, Jr. 2002. The fossil record of predation in dinosaurs. Pp. 251-266, in M. Kowalewski & P.H. Kelley (eds.), The Fossil Record of Predation. The Paleontological Society Papers 8.
  • Holtz, T.R., Jr. 2002. Chasing Tyrannosaurus and Deinonychus around the Tree of Life: classifying dinosaurs. Pp. 31-38, in J.G. Scotchmoor, D.A. Springer, B.H. Breithaupt & A.F. Fiorillo (eds.), Dinosaurs: The Science Behind the Stories, Society of Vertebrate Paleontology, Paleontological Society & American Geological Institute.
  • Holtz, T.R., Jr. 2001. Arctometatarsalia revisited: the problem of homplasy in reconstructing theropod phylogeny. Pp. 99-122, in J. Gauthier and L.F. Gall (eds. ), New Perspectives on the Origin and Early Evolution of Birds: Proceedings of the International Symposium in Honor of John H. Ostrom. Yale Univ. Press.
  • Holtz, T.R., Jr. 2001. The phylogeny and taxonomy of the Tyrannosauridae. Pp. 64-83, in D.H. Tanke and K. Carpenter (eds.), Mesozoic Vertebrate Life: New Research Inspired by the Paleontology of Philip J. Currie. Indiana Univ. Press.
  • Farlow, J.O., S. M. Gatesy, T.R. Holtz, Jr., J.R. Hutchinson & J.M. Robinson. 2000. Theropod locomotion. American Zoologist 40:640-663.
  • Holtz, T.R., Jr. 2000. Classification and evolution of dinosaur groups. Pp. 140-168, in G.S. Paul (ed.), The Scientific American Book of Dinosaurs. St. Martin's Press.
  • Holtz, T.R., Jr. 2000. Theropod paleobiology: more than just bird origins. Gaia 15: 1-3.
  • Holtz, T.R., Jr. 2000. A new phylogeny of the carnivorous dinosaurs. Gaia 15: 5-61.
  • Holtz, T.R., Jr., D.L. Brinkman & C.L. Chandler. 2000. Denticle morphometrics and a possibly omnivorous feeding habit for the theropod dinosaur Troodon. Gaia 15: 159-166.
  • Padian, K., J.R. Hutchinson & T.R. Holtz, Jr. 1999. Phylogenetic definitions and nomenclature of the major taxonomic categories of the carnivorous Dinosauria (Theropoda). Journal of Vertebrate Paleontology 19: 69-80.
  • Holtz, T.R., Jr. 1998. Spinosaurs as crocodile mimics. Science 282: 1276-1277.
  • Holtz, T.R., Jr. 1997. Dinosaur hunters of the Southern Continents. Pp. 43-51, in J.O. Farlow & M.K. Brett-Surman (eds.), The Complete Dinosaur. Indiana Univ. Press.
  • Holtz, T.R., Jr. & M.K. Brett-Surman. 1997. The osteology of the dinosaurs. Pp. 78-91, in J.O. Farlow & M.K. Brett-Surman (eds.), The Complete Dinosaur. Indiana Univ. Press.
  • Holtz, T.R., Jr. & M.K. Brett-Surman. 1997. The taxonomy and systematics of the dinosaurs. Pp. 92-106, in J.O. Farlow & M.K. Brett-Surman (eds.), The Complete Dinosaur. Indiana Univ. Press.
  • Holtz, T.R., Jr. 1996. Phylogenetic taxonomy of the Coelurosauria (Dinosauria: Theropoda). Journal of Paleontology 70: 536-538.
  • Holtz, T.R., Jr. 1995. The arctometatarsalian pes, an unusual structure of the metatarsus of Cretaceous Theropoda (Dinosauria: Saurischia). Journal of Vertebrate Paleontology 14: 480-519.
  • Holtz, T.R., Jr. 1994. The phylogenetic position of the Tyrannosauridae: implications for theropod systematics. Journal of Paleontology 68: 1100-1117.

    Web-based Publications

    Phylogenetic Databases


    Holtz, T.R., Jr. (illustrations by L. Rey). 2007. Dinosaurs: The Most Complete Up-To-Date Encyclopedia for Dinosaur Lovers of All Ages. Random House, 428 pp. Supplementary information (including chapter updates) available at http://www.geol.umd.edu/~tholtz/dinoappendix/.

    Some Links

  • Wikipedia entry, and EvoWiki, too!
  • "Bizarre Dinosaurs: What's Wrong With This Picture? An Audio Critique", audio commentary by me on National Geographic's review of some of their historic dinosaur art
  • An interview with me on Robot Butt

    For Fun

  • Tom Holtz's science fictional appearances:
  • Parry and Carney, Friends for Life, a dinosaur-based webcomic by former UMd student (and veteran of my first Honors Seminar), Mike Keesey
  • Charley Parker's Dinosaur Cartoons

    Last modified: 22 October 2024

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    Chelonoidis-selfie. June 2011.