A novel paramyxovirus in the genus Rubulavirus, named Tioman virus (TiV), was isolated in 1999 from a number of pooled urine samples of Island Flying Foxes (Pteropus hypomelanus) during the search for the reservoir host of Nipah virus. TiV is antigenically related to Menangle virus (MenV) that was isolated in Australia in 1997 during disease outbreak in pigs. Sequence analysis of the full length genome indicated that TiV is a novel member of the genus Rubulavirus within the subfamily Paramyxovirinae, family Paramyxoviridae. However, there are several features of TiV which make it unique among known paramyxoviruses and rubulaviruses in particular: (1) TiV, like MenV, uses the nucleotide G as a transcriptional initiation site, rather than the A residue used by all other known paramyxoviruses; (2) TiV uses C as the +1 residue for all intergenic regions, a feature not seen for rubulaviruses but common for all other members within the subfamily Paramyxovirinae; (3) Although the attachment protein of TiV has structural features that are conserved in other rubulaviruses, it manifests no overall sequence homology with members of the genus, lacks the sialic acid-binding motif N-R-K-S-C-S and has only two out of the six highly conserved residues known to be important for the catalytic activity of neuraminidase.