Pseudocoelomates are animals that possess a body cavity called a pseudocoelom, which is not completely lined by mesodermal tissue. This cavity is located between the endoderm and the mesoderm, allowing for the development of organs and providing space for the movement of fluids. Examples of pseudocoelomates include nematodes (roundworms) and rotifers. The pseudocoelom serves various functions, such as facilitating nutrient transport and providing structural support. Unlike true coelomates, which have a fully developed coelom lined by mesoderm, pseudocoelomates have a simpler body plan. This characteristic is significant in the classification of animals within the animal kingdom.