Article XXXI. — THE SKULL OF CREOSAURUS. 

 By Henry ^''airfield Osborn. 



The skull of the Jurassic Carnivorous Dinosaur Creosaurus 

 is represented by two specimens, from the Bone Cabin Quarry, 

 in the American Museum Collection, Nos. 600 and 666, which 

 supplement each other admirably and give a very complete 

 knowledge of all except the palatal region. The side and 

 back view of No. 600 is presented in figures i and 2, 



The chief features are: (i) the presence of three preorbital 

 fenestrse, (2) the great elongation of the facial region, (3) the 

 abbreviation of the temporal region, (4) the wide extensiori 

 of the parietals on the occiput, (5) the deep depression of the 

 quadrate and its rounded articular connection superiorly with 

 the squamosal. 



Proportions. — The skull is relatively high and narrow, the 

 chief measurements being as follows : 



No. 600. No. 666. 



Length, occipital condyles to premaxillae 810 mm. S85 mm. 



Depth, parietal crest to distal extremitj' of 



qtiadrate 415 43° 



Width of occiput across parietals 230 



Vertical measurement of quadrate 205 235 



Openings. — The openings are placed as follows: (i) the 

 paired narial openings, of elongate oval form, at the sides of 

 the snout, bounded by the premaxillae, nasals, and maxillae; 

 (2) the greatly abbreviated supratemporal fenestra; (3) the 

 deeply extended latero-temporal fenestra (the post-temporal 

 fenestra is entirely closed, and there is no pineal opening); 

 (4) there is a slit-like foramen between the quadrate and 

 quadratojugal ; (5) the orbital openings are deeply vertical; 

 (6) the preorbital fenestra, /', is by far the largest vacuity in 

 the skuh, and is bounded by the maxillaries, prefrontals, and 

 jugals; (7) a much smaller second preorbital fenestra, /", is 

 bounded entirely by the maxillaries; (8) the third preorbital 

 fenestra, /'", lies between the premaxillaries and maxillaries, 

 and is very small. 



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