thaspiviridae thaspiviridae thaspiviridae is a family of spindle-shaped viruses that is not assigned to any higher taxonomic ranks. the family contains a single genus, nitmarvirus, which contains a single species, nitmarvirus nsv1. thaspiviridae tem image of virions of nitrosopumilus spindle-shaped virus 1 (nitmarvirus nsv1). virus classification (unranked): virus realm: incertae sedis kingdom: incertae sedis phylum: incertae sedis class: incertae sedis order: incertae sedis family: thaspiviridae subtaxa genus: nitmarvirus species: nitmarvirus nsv1 members of the family thaspiviridae have linear dsdna genomes of 27 to 29 kbp and are the first viruses known to infect mesophilic ammonia-oxidizing archaea of the phylum thaumarchaeota. the virion of nitrosopumilus spindle-shaped virus 1 (nsv1) is 64±3 nm in diameter and 112±6 nm in length with a short tail at one pole. the spindle-shape morphology of the virion is very similar to those of members of the families fuselloviridae and halspiviridae, which infect hyperthermophilic and hyperhalophilic archaea, respectively.