[BioC] BiomaRt returns empty set for getBM for celegans miRNA

[Zhu, Lihua (Julie)]

Dear biomaRt developers,

The following getBM function call returns 0 record of miRNAs for c.elegans.
It works fine for human. FYI, the martview website does not display any
miRNA for c.elegans either.

Could you please help? Many thanks!
 
library(biomaRt)
mart=useMart(biomart="ensembl",dataset="celegans_gene_ensembl")
miRNA = getBM(c("ensembl_gene_id", "chromosome_name", "start_position",
            "end_position", "strand", "description", "gene_biotype"),
            filter = c("biotype"), values = "miRNA", mart = mart)

Best regards,

Julie