Posterior HoxD cluster architecture of the caecilian. The homologous region of the human is drawn for comparison. The exons of the genes are characterized by black boxes above the cluster (pseudogene in grey); arrows indicate the direction of transcription. The triangles below the cluster represent conserved non-coding regions (putative cis-regulatory elements in blue, potential ncRNA genes in orange) identified by the tracker program, bars and rectangles below the clusters denote repeats. Interspersed repeats identified by Censor are colored dark grey, other repeats, i.e. inverted and direct repeats that are not a part of known transposable elements, are light grey. All distances are drawn to scale.