Coelom with Dermal Tissue

One of the primary ways zoologists group animals has to do with the presence or absence of a coelom and how it is formed.

The coelom (pronounced "see-lome") is a fluid filled cavity formed within the mesoderm. Coeloms developed in triploblasts but were subsquently lost in several lineages. Loss of coelom is correlated with reduction in body size. Coeloms are absent in diploblastic animals such as cnidarians.

Functionally, a coelom can absorb shock or provide a hydrostatic skeleton. It also allows organs to grow independently of the body wall, this can be seen in the earthworm. In mammals, the coelom forms the peritoneal, pleural, and pericardial cavities. Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... The lungs are surrounded by two membranes, the pleurae. ... There are two Pericardial sinuses: transverse and oblique. ...

The presence or absence of a coelom was previously believed to be important for the classification of animal phyla. Recent molecular phylogenies have suggested this character is not as informative as previously believed (and is possibly wrong). In biological taxonomy, a phylum (Greek plural: phyla) is a taxon in the rank below kingdom and above class. ...

==See also==fWWWWWWWW

• abdominal cavity