77 
Thespesius sashatchewanensis falls within the subfamily Hadrosaurinae 
as defined by Lambe 1 e.g 
* ‘Forms large, posterior part of skull variable, supraorbital region flat, fronto-parietal 
region enlarged, nasals extending far forward, anterior nares transversely confluent, nasal 
passage, anteriorly, not enclosed in bone, premaxillae confined to anterior portion, lachrymal 
of moderate size, ischium pointed distally.” 
Generic Characters 
Skull long, narrow posteriorly. Anterior expansion of premaxilla 
recurved so as to roof over a cavity of moderate size. Nasal extending in 
advance of anterior border of narial opening, frontal relatively long and 
contributing to formation of orbital rim, lateral temporal fossa high and 
moderately narrow. Mandible long and slender, anterior caudal vertebrae 
concavo-convex. Femur considerably longer than tibia. 
Specific Characters 
Skull high posteriorly. Premaxillse broadly expanded anteriorly, 
antero-inferiorly thickened and marked with tooth-like projections. Jugal 
long and slender. Quadrate long. Frontal contribution to orbital rim 
slight. Fifty-two vertical rows of teeth in maxilla and forty-four rows 
in dentary. Maxillary teeth with bluntly rounded apices and median 
keel very high in basal portion, edges slightly raised and sparsely studded 
with papillae. Dentary teeth with bluntly pointed apices and smooth 
borders, except for very slight papillations on the anterior ones. Enamel 
faces of dentary teeth slightly more than twice as long as wide, scapula 
long and moderately straight. 
Skull. The left side of the skull is best preserved, all the bones being 
articulated except the predentary, which is missing. The bone is in a 
splendid state of preservation and the sutures can be clearly distinguished. 
Viewed from the side the skull is subtriangular in outline, high posteriorly, 
but gradually decreasing in height anteriorly. The length of the quadrate is 
to the total length of the skull as 1 over 2*33, whereas in T. edmontoni 
the proportion is as 1 over 2-75 and in T. annectens it is as 1 over 2-90. 
Viewed from above the skull is broad in its posterior half, has its 
greatest expansion through the distal ends of the quadrates, is greatly 
constricted in advance of the jugals, and is broadly rounded in front. 
The nasal orifice is a large, well-defined, oval-shaped cavity, as in 
other members of the genus. It lies mainly within the premaxilla, but is 
bounded superiorly and supero-laterally by the nasal, the anterior portion 
of which flanks the upper limb of the premaxilla. 
The orbit is large and subcircular in outline, it is bounded above by 
the prefrontal, frontal, and postorbital; behind by the postorbital and 
ascending process of the jugal; below by the jugal and in front by the 
jugal, lachrymal, and prefrontal. The post-orbital has expanded so far 
forward as to almost exclude the frontal from the orbital rim. 
The infratemporal fossa is proportionately longer than in other mem- 
bers of the genus, due to the excavation of the jugal. It is bounded above 
by the postorbital and squamosal ; behind by the squamosal, quadrate, 
and jugal; below by the jugal, and in front by the jugal and postorbital. 
1 Lambe, L. M.: Geol. Surv., Canada, Mem. 120, p. 68 (1920). 
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