The nemotoda is probably one of the biggest phylums located in the world. It is estimated to have over 28,000 – 30,000 described species within it, and 1,000,000 species in total– both extinct and living. They are known for being located in a variety of ecosystems – most of which include marine sea, warm tropical lands, under earth soils, and high elevation mountain ranges. However, where they most flourish is in extreme environments, such as ocean trenches and deserts. Most of the reason scientists believe that there are over 1,000,000 species because nematodes mainly live on the ocean floor. Most nematoads have muscles surrounding their body cavities that assist in their movement across any surface.
The relationships of the nematodes and their close relatives among the protozomian Metoza are unresolved. Traditionally, they were held to be a lineage of their own, but in the 1990s it was proposed that they form a clade together with molting animals such as arthopods. This group has been named. However, the monophly of the Echoydsa was never unequivocally accepted: while most researchers consider at least the placement of arthropods as close relatives of annelids— with which they were formerly united — to be unwarranted, the presumed close relationships of the nematodes and relatives with the arthropods has been a major point of contention
The relationships of the nematodes and their close relatives among the protozomian Metoza are unresolved. Traditionally, they were held to be a lineage of their own, but in the 1990s it was proposed that they form a clade together with molting animals such as arthopods. This group has been named. However, the monophly of the Echoydsa was never unequivocally accepted: while most researchers consider at least the placement of arthropods as close relatives of annelids— with which they were formerly united — to be unwarranted, the presumed close relationships of the nematodes and relatives with the arthropods has been a major point of contention