Guidraco possessed approximately 82 teeth in its 38 cm (14.9 in) long skull. Both the mandible and upper jaw (consisting of maxillae, premaxillae, and nasals) were of equal length but the upper jaw contained 23 teeth on each side whereas the mandible contained 18 teeth per side. The first teeth in each row are held almost horizontal and, as the teeth are followed caudally in the mouth, they begin to curve more and point toward the open mouth; up in the mandible and down in the upper jaw. The mandible's rostral teeth are slightly larger than their counterparts in the upper jaw and for the most part the teeth are of similar sizes caudally. These forward most teeth come together, or occlude, in such a way that they form a basket of teeth and mouth which would have been very well suited to grasping fish and other "slippery" meals. The initial description makes mention of this dietary inference as well and leans heavily on the idea that this would have been the preferred diet of Guidraco.