A very specialized plant life grows in the waters of the mangrove swamp. It must be able to withstand inundation by muddy fresh water at times of flood, and by salt water at high tides. It must also be able to grow in the shifting muds brought down by the rivers. The mangroves can do this, securing their roots in the mud banks to anchor the sediments and build them up into permanent parts of the landscape. The roots often protrude above the level of mud and water to help the plant to breathe, there being little oxygen in the mud of the swamp.In the water there are many other varieties of plants, and these are consumed by a number of different animals. The largest is the glub, a member of the adaptable hypsilophodonts. It is similar in appearance to the watergulp of the tropical river swamps of the Amazon River in South America, also evolved from a running basal neornithischian (in that case, a thescelosaur). The resemblance is a case of parallel evolution, in which two related creatures have developed along the similar lines in response to similar environmental conditions. The evolution took place independently, on opposite sides of the world. In the glub, the process has gone even further than in the watergulp. The whole body of the glub, all 2 meters (6 feet) of it, has become a swimming organ. Sinuous, lateral movements of its body and tail, aided by the tall fin down the back, drive the animal forward through the water. It steers itself by its forelimbs. The hind limbs have totally atrophied.