Dedicated to summarizing the facts regarding origins
& Nature Photo Galleries
 User:J. Spencer [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0
(http://creativecommons.org/licenses/by-sa/3.0/) or CC BY 2.5 (https://creativecommons.org/licenses/by/2.5)], from Wikimedia Commons
 Thescelosaurus: DinoChecker dinosaur archive, http://www.dinochecker.com/dinosaurs/THESCELOSAURUS
 Clint A. Boyd [CC BY 4.0
 D. Gordon E. Robertson [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]
 Thescelosaurus, Prehistoric Wildlife, http//www.prehistoric-wildlife.com/species/t/thescelosaurus.html
 Tim Evanson from
Washington, D.C., United States of America [CC BY-SA 2.0 (https://creative commons.org/licenses/by-sa/2.0)], via Wikimedia Commons
Rocky Mountain Dinosaur Resource Center, Woodland Park, Colorado
Photo by J. Spenser 
Copyright 2019 All rights
Thescelosauruses were bipedal ornithopods with stout legs, short arms and long tails
to counterbalance their bodies. Their tails were about half as long as the animals overall length. Each leg had four
toes and each arm five very small fingers. Their chest and abdomen were broad and bulky.
Left: Skull of NCSM 15728 in right lateral view. (A) diagram highlighting the contacts between the bones
on the right side of skull; (B) illustration of right side of skull; (C) photograph of right side of skull. In (A) and (B), grey regions
indicate the presence of matrix on the specimen. Abbreviations: an, angular; asor, accessory supraorbital; bo, basioccipital; de,
dentary; eo, fused opisthotic/exoccipital; fr, frontal; ju, jugal; la, lacrimal; mx, maxilla; na, nasal; pd, predentary; pf, prefrontal;
pm, premaxilla; po, postorbital; pop, paroccipital process; qj, quadratojugal; qu, quadrate; sor, supraorbital; sq, squamosal; su,
surangular. Scale bars equal 10 cm.
Right: Skull of NCSM 15728 in left lateral view. (A) diagram highlighting the contacts between
the bones on the left side of skull; (B) illustration of left side of skull; (C) photograph of left side of skull. In (A) and (B),
grey regions indicate the presence of matrix on the specimen. Abbreviations: an, angular; bo, basioccipital; de, dentary; eo, fused
opisthotic/exoccipital; fr, frontal; ju, jugal; la, lacrimal; mx, maxilla; na, nasal; par, parietal; pd, predentary; pf, prefrontal;
pl, palatine; pm, premaxilla; po, postorbital; pop, paroccipital process; pro, prootic; ps, parasphenoid; pt, pterygoid; qu, quadrate;
so, supraoccipital; sp, sclerotic plate; sq, squamosal; st, stapes; su, surangular. Scale bars equal 10 cm.
Canadian Museum of Nature, Ottawa, Ontario, Canada
Cast of NMC 8537, type specimen of T. edmontonensis (T. sp. per Boyd et al., 
Photo by D. Gordon E. Robertson 
Clint A. Boyd 
1989 Fd. Hell Creek Formation, Carter Co., Montana, USA
Found in the same micro-site as 1990 and 1991
max. Specimen's lateral processes 2.85" tip to tip
Premaxillary Tooth (fossil)
Considerable tip wear with some fine ridges still on base of crown.
2009 Fd. Hell Creek Formation,
Toe Ungual (cast)
2024 Fd. Hell Creek Formation, Harding Co., South Dakota, USA
1.35" long, 0.7" width max.
Mandible Body Portion (fossil)
Longitudinal section showing spacing of teeth sockets
1990 Fd. Hell Creek Formation,
Carter Co., Montana, USA
1.5" long, 0.6" high max.
1991 Fd. Hell Creek Formation,
Carter Co., Montana, USA
0.9" long, 0.8" width max.
Museum of the Rockies, Bozeman, Montana, USA
Photo by Tim Evanson 
Heads of Thescelosauruses were unusually long and tapered down from the back of the
skull to the end of the snout which was tipped with a beak on the upper maxilla for snipping food. Teeth were very small
for this animal's size. Six pairs of premaxillary teeth were present with no corresponding teeth on the lower jaw (mandible).
These teeth were pointed and had a bulb shape towards the jaw. Between the premaxillary teeth and the maxillary teeth was
a gap. The maxillary teeth consisted of about twenty sets and they and the corresponding teeth on
the lower jaw were leaf shaped with fine ridges and very similar to those of Pachycephalosaurus. Thescelosauruses are
generally thought to be herbivores because of their leaf-shaped teeth that are ideal for slicing up soft
vegetation although they may have had a more varied diet. They had long bony rods over their eyes. 
Thescelosaurus upper legs were longer than their lower legs. By this it has been interpreted that they were slow
runners.  If they were slow runners, then how they avoided the various predators found in the same stratum such as Tyrannosaurus
Rex is uncertain. Shorter legs may provide some advantage over longer legs running up steep slopes as river banks or mountains. Also,
it has been suggested that they avoided predators by swimming to the other side of rivers.
Based on the limited number of Thescelosaurus fossils available to date, their overall length by most references varied from about
8 to 13 feet. Another source indicates to 15 feet.  Variations in adult sizes may be due to sexual dimorphism and/or perhaps adult
age differences as most if not all reptiles today have the potential for growth their whole lives.
One specimen known as Willy was thought by some to have a four chambered heart. based on some material found in the
chest area of its fossil skeleton. This lent weight to the question whether dinosaurs were cold-blooded or warm-blooded
animals as birds and mammals are warm-blooded and have four chambered hearts. Later extensive testing showed that this material
was only hardened sand that was probably washed in. 
There currently three generally
recognized species of Thescelosauruses: T. neglectus, T garbanii, and T. assiniboiensis.  Also, Bugenasaura, a former
named genus, has been been found to be a synonym for Thescelosaurus.
Thescelosaurus' fossils have been been found in Alberta and Saskatchewan, Canada; and Montana, Wyoming, South Dakota, and
Colorado, USA. 
Fd. Dawson Co., Montana
In popular culture it is not uncommon to see Thescelosauruses depicted as having feathers. There is
no evidence so far to support this assumption (guess).