An NPIRTS is a perfect isosceles right triangled square (perfect IRTS) which is a subdivision of an imperfect IRTS. The lowest order of an NPIRTS which does not have an unbroken main diagonal is 16. Every NPIRTS below order 16 is a subdivision of SPIIRTS 2:1TA.
The NPIRTS catalogues are available as pdfs from this page.
The fact that every NPIRTS has a subdivided triangle is not recorded as a property. The properties below may precede "order:side" in a tiling's title:
Jasper D. Skinner found many NPIRTSs before this catalogue was built by Geoffrey H. Morley. Only the two lowest order NPIRTSs are attributed to discoverers:
J. Douglas and E.P. Starke (D&S, United States) (7:10PA only)
Arthur H. Stone (AHS, United States, 1916-2000) (7:7PA only)