Fig. 4 in Rediscovery of an internal organ in heart urchins (Echinoidea: Spatangoida): morphology and evolution of the intestinal caecum

Fig. 4 Homology of selected accessory structures associated with the digestive tract of heart urchins (Echinoidea: Spatangoida). a Dissected specimen of Brisaster latifrons (left) and schematic drawing of the general digestive tract morphology found within all species of the genera Brisaster and Tripylaster, as well as some species of the genus Abatus (right). b Dissected specimen of Heterobrissus niasicus (left) and