[1][2][3] This genus is known in the fossil records from the latest Miocene to the Quaternary (age range: from 5.332 to 1.806 million years ago).

[2][3] Hemisyntrachelus cortesii lived about three million years ago (from 3.6 to 2.588 mya).

[3] Its fossil skeleton reaches a length of about 3 metres (9.8 ft) and it has been found only in La Torrazza, Italy.

This species shows intermediate characters between the bottlenose dolphin and the killer whale.

Fossils have been found only in Orciano, which is in a Piacenzian coastal claystone in Italy.