Marcello Toninelli made his debut in comics with 'Dante', a comic strip he wrote and drew for the Roman underground comic Off Side. Through Bonvi, he subsequently drew for Edifumetto for a while, after which he went to work in Gianni Bono's studio, Gestudio, making 'Sexi Operette'. He specialized in erotic comics and contributed to Luciano Secchi's magazine Adamo, and drew 'Sonny Sold' and 'I Tre Ragazzi di Sonter'.
In 1982, he began a collaboration with Bonelli, and worked on the 'Zagor' series. He then founded his own publishing house, L'Editrice 50, and published Fox Trot, Prova d'Autore, Marshall Miki and Fritto Misto. The publishing house closed in 1987. In 1990, Toninelli began a second firm, Ned 50, and launched the fanzine Fumo di Chine.
For Il Giornalino, Toninelli created series like 'Prof. Van Der Groot' and 'Agenzia Scacciamostri'. He scripted the miniseries 'Dark' for Granata Press, as well as 'Gordon Link' and 'Lazarus Ledd'. He revived 'Dante' in the mid-1990s through his own Ned 50 label for Il Giornalino, and created 'Shanna Shokk' for Star Comics. He also created parodies on 'Omero' and 'Enea'.