contained in the file modules.txt. 

FIGURE 7 shows the degree distribution of the NHCD for different times. 

Table I lists the different known functional modules of the NHCD and the respective citations to the literature. The complete collected data is listed in the datafile: links.txt. This file includes the links between the cell types, their time of appearance in days after fecundation ( T$_{a}$ ), and the known functional module they belong to. The references to the publications reporting each link appear in the table. Data on the structure of individual communities were obtained from the specialized literature. Some functional communities are: germ layer and extraembryonic tissue [1, 2, 4, 5], digestive system [1, 5], pharyngeal system [3, 5, 6], cloacal system [5], neural system [1, 6], eye [5, 6], primitive oral cavity [5], nose [5], skeletal system [3, 16], skeletal muscular system [1, 6, 17], hematopoietic system [18], urogenital system [19, 20], cardiovascular system [5, 6], mesothelium [21], respiratory [22], neural crest [5, 23–25], adenohypophysis [26], ear [6, 27], and integumentary system [5, 6, 28]. 

