Lateral view of the skull of MVZ 43325. Although the relationship is poorly supported, the hoatzin shares a few osteological characters with seriamas that are observable in the skull, including the caudal fusion of the vomers, pneumatic foramina on the dorsal and caudal surfaces of the otic process on the quadrate, and pneumatic foramina on the lateral sides of the corpus of the premaxilla (Mayr and Clarke, 2003).