The Mastodonte dei Giovi was a special double steam locomotive built specifically for use on the difficult Apennine stretch of the new Turin - Genoa railway line, inaugurated in 1853.

However, an international competition announced by the Semmering railway of Austria had brought other solutions more suitable to increase the uphill haulage capacity of the locomotives of the time.

This solution impressed the brilliant Italian engineer Germain Sommeiller but he considered it would be difficult to negotiate the sharp curves of the Giovi given the long rigid frame.

The name "Mastodonti dei Giovi" was borrowed from that of a large fossil found during the excavation of the tunnel near Busalla.

Two double units, 76 + 77 and 78 + 79 were divided and rebuilt at the Officine Nuove di Torino as separate tank locomotives.