Tyrannosaurids were the apex predators of Late Cretaceous Laurasia and their status as dominant carnivores has garnered considerable interest since their discovery, both in the popular and scientific realms. As a result, they are well studied and much is known of their anatomy, diversity, growth, and evolution. In contrast, little is known of the earliest stages of tyrannosaurid development. Tyrannosaurid eggs and embryos remain elusive, and juvenile specimens — although known — are rare. Perinatal tyrannosaurid bones and teeth from the Campanian–Maastrichtian of western North America provide the first window into this critical period of the life of a tyrannosaurid. An embryonic dentary (cf. Daspletosaurus) from the Two Medicine Formation of Montana, measuring just 3 cm long, already exhibits distinctive tyrannosaurine characters like a “chin” and a deep Meckelian groove, and reveals the earliest stages of tooth development. When considered together with a remarkably large embryonic ungual from the Horseshoe Canyon Formation of Alberta, minimum hatchling size of tyrannosaurids can be roughly estimated. A perinatal premaxillary tooth from the Horseshoe Canyon Formation likely pertains to Albertosaurus sarcophagus and it shows small denticles on the carinae. This tooth shows that the hallmark characters that distinguish tyrannosaurids from other theropods were present early in life and raises questions about the ontogenetic variability of serrations in premaxillary teeth. Sedimentary and taphonomic similarities in the sites that produced the embryonic bones provide clues to the nesting habits of tyrannosaurids and may help to refine the prospecting search image in the continued quest to discover baby tyrannosaurids.
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Research Article|
January 25, 2021
Baby tyrannosaurid bones and teeth from the Late Cretaceous of western North America1
Gregory F. Funston;
a
School of GeoSciences, University of Edinburgh, Edinburgh EH9 3FE, UK.b
Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada.Corresponding author: Gregory F. Funston (email: [email protected]).
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Mark J. Powers;
Mark J. Powers
b
Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada.
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S. Amber Whitebone;
S. Amber Whitebone
c
Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada.
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Stephen L. Brusatte;
Stephen L. Brusatte
a
School of GeoSciences, University of Edinburgh, Edinburgh EH9 3FE, UK.
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John B. Scannella;
John B. Scannella
d
Museum of the Rockies, Montana State University, Bozeman, Montana 59717, USA.
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John R. Horner;
John R. Horner
e
Honors Program, Chapman University, Orange, California 92866, USA.
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Philip J. Currie
Philip J. Currie
b
Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada.
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a
School of GeoSciences, University of Edinburgh, Edinburgh EH9 3FE, UK.b
Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada.
Mark J. Powers
b
Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada.
S. Amber Whitebone
c
Department of Biological Sciences, University of Calgary, Calgary, AB T2N 1N4, Canada.
Stephen L. Brusatte
a
School of GeoSciences, University of Edinburgh, Edinburgh EH9 3FE, UK.
John B. Scannella
d
Museum of the Rockies, Montana State University, Bozeman, Montana 59717, USA.
John R. Horner
e
Honors Program, Chapman University, Orange, California 92866, USA.
Philip J. Currie
b
Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada.Corresponding author: Gregory F. Funston (email: [email protected]).
Publisher: Canadian Science Publishing
Received:
11 Sep 2020
Accepted:
17 Nov 2020
First Online:
16 Sep 2021
Online ISSN: 1480-3313
Print ISSN: 0008-4077
Published by NRC Research Press
Canadian Journal of Earth Sciences (2021) 58 (9): 756–777.
Article history
Received:
11 Sep 2020
Accepted:
17 Nov 2020
First Online:
16 Sep 2021
Citation
Gregory F. Funston, Mark J. Powers, S. Amber Whitebone, Stephen L. Brusatte, John B. Scannella, John R. Horner, Philip J. Currie; Baby tyrannosaurid bones and teeth from the Late Cretaceous of western North America1. Canadian Journal of Earth Sciences 2021;; 58 (9): 756–777. doi: https://doi.org/10.1139/cjes-2020-0169
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Index Terms/Descriptors
- Alberta
- Archosauria
- behavior
- Canada
- Chordata
- Coelurosauria
- computed tomography data
- Cretaceous
- Diapsida
- dinosaurs
- Drumheller Alberta
- embryos
- Horseshoe Canyon Formation
- jaws
- Mesozoic
- Montana
- morphology
- regression analysis
- Reptilia
- Saurischia
- size
- statistical analysis
- teeth
- Teton County Montana
- Tetrapoda
- Theropoda
- three-dimensional models
- Two Medicine Formation
- Tyrannosauridae
- United States
- Upper Cretaceous
- Vertebrata
- Western Canada
- X-ray data
- Choteau Montana
- Albertosaurus sarcophagus
- Morrin Alberta
- Daspletosaurus horneri
Latitude & Longitude
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