Sutures, the fibrous joints between bones, play important roles in the growth and mechanics of vertebrate skulls. Depending on their required mechanical function, sutures display different collagen fiber orientations and bone morphologies (e.g., abutting, interdigitated, beveled). Although in most mammals beveled sutures overlap only at the edges of skull bones, in cetaceans (whales, dolphins, and porpoises) bone overlap is so extensive that some sutures cover nearly the entire surface of the underlying bone. For example, the maxilla may overlap all but a narrow rim of the frontal bone. This extensive overlap, in conjunction with shortened maxillo-occipital distance, is commonly referred to as skull telescoping. The function(s) of skull telescoping are unknown but widely speculated, and include: relocating the nares to form a blowhole, aiding in echolocation, anchoring muscles of the nasal passage and blowhole, and counterbalancing the elongate rostrum. Despite widespread discussion of possible functions, the histological structure of overlapping cetacean sutures has received little attention. To inform investigations of functional hypotheses, we examined the maxillo-frontal suture in neonatal and adult bottlenose dolphins (Tursiops truncatus) using CT, microCT, and histological methods. In the neonates, the beveled interface was smooth and sutural fibers were oriented parallel to the bone margins, but in the adult, the maxilla and frontal were interlocked with rugose interdigitation of the bones and a complex arrangement of collagen fibers. This adult morphology suggests this suture forms a strong joint that resists complex mechanical loading.