The (front bone of the upper jaw) had a rugose texture, likely developing a rhamphotheca (horny beak). The was rather short and low, giving form to the (hole in the skull behind the nostril opening), and had a pronounced antorbital fossa (depression) which was strongly demarcated by two long ridge-like structures on the external surface of the maxilla, a unique trait to Beibeilong. The bones of Beibeilong were fused around the naris (nostril) openings and had several nutrient foramina (blood vessel attachments) on their external surface. The had an open-crescentic shape that contributed to the anterior border of the orbit (eye socket). A small depression on the top border of the posterior process (bony projection or extension) of the lacrimal allowed the frontal bone to overlap, which was unique to Beibeilong. The was rather domed with formed the upper border of the orbit as well as part of the skull roof. The ("cheek" bone) was a long and rather thin bone making contact with the maxilla and lacrimal, as in most oviraptorosaurs, and gave shape to the lower border of the orbit. The , being the last bone in contribute to the orbit, was a short, slender, and curved element that extended between the frontal and top process of the jugal. The was tall and nearly triangular bone that is joined by the jugal. Behind the quadratojugal was the , a squared bone of great importance for the motion of the lower jaw. The of Beibeilong was relatively short and deep with proportions similar to that of other caenagnathids (such as Gigantoraptor or Microvenator), and had an overall plate/shovel-like tip with a downturned sharp edge. The posterior end of the dentary formed the external (circular hole in the lower jaw). The (bone that joined the dentary at its upper edge) had a fairly curved top border and formed a relatively low (bony projection that extends upwards from the upper border of the surangular). It was connected to the top border of the dentary through an articular depression. The (bone located just below the surangular) developed a convex crest-like articulation for the quadrate, which is mostly common in oviraptorids. In particular, the articular bone of Beibeilong extended backwards into a retroarticular process that had a characteristic concave posterior facet. Postcranial skeleton The centra of some had large pleurocoels (air-filled hollow depressions) on their lateral sides. The cervical neural arches (upper, and