OSTEOLOGY OF CARNIVOROUS DINOSAURS. 



23 



part of the quadratojugal is 143 mm. the greatest diameter dorso-ventrally is 

 135 mm. 



Quadrate (q.). — The quadrate from the right side of skull No. 4734, U.S.N.M., 

 is perfectly preserved and since it was found detached from the posterior part of the 

 skull I am able to describe this element in detail. This bone is relatively short 

 having a greatest length dorso-ventrally of 192 mm., with an irregularly rounded 

 articular proximal end for articulation with the squamosal. The distal end is 

 widely expanded transversely with a smooth articulating surface that is. bisected 

 diagonally by a broad concave depression that divides this end into two elongate, 

 obtusely rounded articular surfaces that fit closely into the cotyloid depressions of 

 the lower mandible. The articulating surfaces of this end of the quadrate extend 

 well up on the anterior and posterior aspects, being separated from the nonarticular 

 part of these surfaces by a low but well defined undulating ridge. 



Externally the quadrate is suturally united with the quadratojugal. The 

 suture between the two bones beginning 31 mm. below the upper extremity is visible 

 from a lateral aspect but just 

 above the quadrate foramen it 

 passes to the posterior view. 

 As in Ceratosaurus and Tyran- 

 nosaurus the external boundary 

 of the quadrate foramen is 

 formed by the inner surface of 

 the quadratojugal. The pos- 

 terior view presents a deep de- 

 pression that slopes forward in 

 all directions toward the quad- 

 rate foramen. A widely 

 rounded groove runs diagonally 

 downward from the inner sur- 

 face of the quadrate to the 

 quadrate foramen. Imme- 

 diately above this groove on the median posterior side a pointed spurlike projection 

 extends posteriorly. On the anterior inner side the quadrate sends anteriorly a thin 

 triangular sheet of bone that meets the pterygoids in the articulated skull by 

 squamous suture. The lower border of this forward projection turns inward at right 

 angles forming a narrow shelf that extends back and joins with the heavier shaft of 

 the quadrate. The greatest transverse width of the distal end is 89 mm., the 

 greatest diameter of the proximal end is 27 mm. 



Squamosal (sq.). — The right squamosal of skull No. 4734, U.S.N.M., was found 

 articulated, the left one being detached. These elements show the squamosal to be 

 an irregular-shaped element, with a deep, cupped surface on the lower posterior 

 side for the reception of the upper articular end of the quadrate. Forward of this 

 articulation a wide but thin process descends to meet the quadratojugal, its lower 

 end uniting by squamous union on the inner side of the upper end of the quadra- 

 tojugal. Posterior to the quadrate articulation the squamosal contracts to an 

 obtusely pointed process external to which a heavy descending process is directed 



Fig. 13.— Right tugal, quadratojugal, and quadrate, op Antrodemus 

 valens leldy. no. 4734, u.s.n.m. 1 nat. size. viewed from the in- 

 ternal side, j, jugal) 0, lower boundary of the orbit; qj, quadra- 

 TOJUGAL; q, QUADRATE. 



