Gain and loss of carcinoembryonic antigen related cell adhesion molecule (CEACAM) family features in mammals during evolution. The phylogenetic and taxonomic relationship of selected mammalian species is shown schematically. Major radiation events with estimated radiation times in million years (Myr) are indicated . The appearance of various features during radiation is marked by coloured dots. Linear and circular arrows indicate the absence or presence of an inversion event between the two main CEACAM1-like gene loci (see Figure 3 for details). V, B (boxed) indicate that CEACAM1 serves as bacterial (B) or viral (V) pathogen receptor in the marked lineage. Question marks in the pregnancy-specific glycoproteins dots indicate that the assignment to this CEACAM1-like group is still unclear due to a lack of expression data. For abbreviation of species names see Table 1.