 Based on morphological characteristics, cyanophages are placed into the families Myoviridae, Podoviridaeand Siphoviridae, and although not formally recognized by the International Committee on Taxonomy of Viruses, historically cyanophages have been further classified into as a Cyanomyovirus, Cyanopodovirus or Cyanostylovirus based on which of the three families in which they are grouped.The type species for Cyanomyovirus of the family "Myoviridae" is Cyanophage AS-1, which was isolated from a waste stabilization pond, and was also the first genus recognized.The tails have been observed as either contractile or noncontractile with lengths of 20 to 244 nm, widths of 15 to 23 nm, and a shrinking range of 93 nm.