Chubutophis

Chubutophis is an extinct genus of boid snakes from the Eocene-aged Sarmiento Formation in Chubut Province, Argentina. It is known from a partial set of vertebrae suggesting a juvenile individual. The type species is C. grandis.

Size
According to Adriana Albino, the describing researcher,

"Considering that this material is from a young specimen, its size is extraordinary and it is estimated that the adult would have reached greater dimensions than those observed in the largest snakes known up to the present, including Madtsoia and Gigantophis"