Thelaziidae is a family of spirurian nematodes, which form the mid-sized lineage of the superfamily Thelazioidea. Like all nematodes, they have neither a circulatory nor a respiratory system.
They number 7 genera or so, with a few dozen species all together. Mostly parasites of birds, a few have also been found in other vertebrates.[1]
The subfamily Oxyspirurinae is monotypic, as are several little-known genera in the Thelaziinae; these all might not be valid. All together, the systematic layout of this family is liable to change and cannot be considered more than tentative.
Subfamily Oxyspirurinae Skrjabin, 1916
Subfamily Thelaziinae Skrjabin, 1915