Nitmarvirus NSV1 Thaspiviridae is a family of incertae sedis spindle-shaped viruses.

[1] Thaspiviridae are known to infect mesophilic ammonia-oxidizing archaea of the genus Nitrosopumilus.

Its morphology is very similar to that of the members of the families Fuselloviridae and Halspiviridae, which infect hyperthermophilic and hyperhalophilic archaea, respectively.

[2] Its genome is linear dsDNA of length 27–29 kbp, with 176 bp terminal inverted repeats.

The virus also encodes a proliferating cell nuclear antigen which is also likely to be involved in viral genome replication.