THE CLASSIFICATION OF ANIMALS 



KINGDOM SUBKINGDOM BRANCH 



SUBSERIES 



ANIMALIA— 



METAZOA- 



Mesozoa- 

 Parazoa - 



PHYLUM 

 Protozoa 



- Mesozoa 



- Porifera 



Radiata 

 (radial) 



Bilateria 

 (bilateral) 



Acoelomata _ 



(without body cavity) 



4s 



4! 



Coelenterata 

 Ctenophora 



Platyhelminthes 

 Nemertinea 



Pseudocoelomata 

 (with "false" coelom) 



Schizocoela-- 



Eucoelomata 



(with "true coelom" 



or its remnants) 



Acanthocephala 



Aschelminthes 



Entoprocta 



Ectoprocta 



Phoronidea 



Sipunculoidea 



Echiuroidea 



MoUusca 



Annelida 



Onychophora 



Arthropoda 



Brachiopoda 



Chaetognatha 



Echinodermata 



Hemichordata 



^hordata 



*Some brachiopods are apparently schizocoelous in their mode of coelom formation, but this 

 may be a secondarily derived characteristic. 



Fig. 7.4. Interrelationships among the phyla of animals, based on similarities and differences in 

 broad, general characteristics. 



shall be forthcoming showing its relationship to some other phylum."" In 

 the treatise from which this quotation was taken, Hyman lists 22 phyla; 23 are 

 now commonly recognized (see Fig. 7.2), and an additional new phylum has 

 recently been proposed to contain an aberrant group of animals, the 

 Pogonophora, dredged from ooze on the deep ocean floor. 



Some of these phyla are small in numbers of species, and many consist of 

 animals not easily available and hence relatively unknown except to special- 

 ists. For the purposes of the present chapter, only the larger and better- 

 known phyla need to be considered in any detail. It can then be remembered 

 that the Animal Kingdom includes certain lesser groups, which may also be 

 classified as phyla, although even today authorities differ on many details of 

 classification. For example, the phylum Aschelminthes has been proposed to 

 include several problematical groups classified in different combinations by 

 various authorities; many zoologists do not interpret the evidence for the 

 interrelationships of these forms as justifying their inclusion in a single 

 phylum. 



The list of phyla and their principal subdivisions in Figure 7.2 is inserted 

 for reference and orientation; some minor groups have been omitted. As you 

 proceed, the names of the larger phyla, such as Protozoa, Coelenterata, 

 Arthropoda, and Chordata, as well as of some of their subdivisions, will 

 become familiar. 



"Quoted by permission from L. H. Hyman, The Invertebrates: Protozoa through Ctenophora, 

 copyright 1940 by McGraw-Hill Book Co., Inc., page 32. 



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