 Mixed twintrons (consisting of introns belonging to different categories) were characterized from the "Euglena gracilis"
rps3 gene in which an internal group II intron is found to interrupt an external group III intron.In "Rhodomonas salina" (="Pyrenomonas salina") twintrons (nested group II/group III introns) were identified where the internal intron lost its splicing capacity, essentially merging with the outer intron forming "one" splicing unit.Recently, two novel twintrons have been uncovered within the fungal mitochondrial genome, one at position mS917 of the "Cryphonectria parasitica" mt-rns gene, where a group ID intron encoding a LAGLIDADG ORF invaded another ORF-less group ID intron.