Embryonic staging tables provide a standard of developmental stages that can be used by individual investigators and provide approximate time points for the study of developmental phenomena. Surprisingly, despite the presence of a plethora of studies on the chicken skull and its role as a model species in developmental research, a staging table of the development of the chicken skull remains lacking. A detailed photographic staging table of the osseous portion of the chicken skull is thus presented here based on cleared and stained HH stages spanning HH 35 (first appearance of skull ossification) to the final stage before hatching (HH 45). This table documents the development of most of the cranial elements in the skull from the start of ossification until the element takes its final shape. The table shows that the elements of the lower jaw and ventral side of the skull begin ossifying before the skull roof and that most elements take roughly 5 days to reach their final shape, whereas others take up to 9 days (e.g., the frontal). The obtained results lead to several hypotheses about chicken skull development and provide a timeframe for future studies on chicken skull development.

Sutures are fibrous joints that occur between bone elements in vertebrate skulls, where they play a variety of roles including facilitating skull growth and function. In addition, a variety of studies examining sutures from diverse perspectives in many taxa have enabled the determination of anatomical homologs. Surprisingly, one important aspect of sutures—histology—remains unknown in the key model organism of the chicken. To fill this gap in our knowledge, we generated histological sections of six different cranial sutures across a range of developmental stages in embryonic chicken. Despite having a skull that is largely co‐ossified or fused as an adult, we found that the types, components, and ontogeny of sutures in chicken skulls are very similar to sutures in other vertebrates. We did, however, find a new transient stage in the ontogeny of sutures between endochondral bone elements, in which one element has ossified and one was still cartilaginous. Moreover, to better understand the morphogenetic events at the onset of suture formation, we compared the developmental histology of six sutures with that of the space between the two ossification centers of the frontal—a location expected to be void of suture structures. We found that the mesenchymal cells in sutures condense and form a middle vascular layer. This was not found to be the case in the space between the two ossifications of the frontal, where instead only osteoid occurs.