Fig. 5 Occurrence of the intestinal caecum in heart urchins (Echinoidea: Spatangoida). a An intestinal caecum is found only in the Schizasteridae (Spatangoida: Paleopneustina). b Distribution of the intestinal caecum among schizasterids. Both phylogenetic trees show the results of an analysis based on morphological characters (Stockley et al. 2005). The three genera mentioned as incertae sedis were not part of the cited phylogenetic study. Black-framed box genus analyzed in the present study, black square hypothetical evolutionary event, black star intestinal caecum present in all species analyzed, black-framed star intestinal caecum present only in some of the analyzed species, cross fossil taxon, R! loss of structure

Published as part of Ziegler, Alexander, 2014, Rediscovery of an internal organ in heart urchins (Echinoidea: Spatangoida): morphology and evolution of the intestinal caecum, pp. 383-395 in Organisms Diversity & Evolution (New York, N.Y.) 14 (4) on page 392, DOI: 10.1007/s13127-014-0178-2, http://zenodo.org/record/13171877