The skeleton of an Arnoux’s Beaked Whale (Berardius arnuxii) with a Gray’s Beaked Whale (Mesoplodon grayi — then “australis”) for comparison; the last image is a cleaner version from Beddard. Points of interest for the Giant Beaked Whale include the relatively small head, long neck with with only the first three vertebrae fused, low vertebral spines, and elongate lumbar vertebrae. Beddard remarkably stated the “proportions are curiously suggestive of some of the extinct aquatic Mosasaurians, as well as of some of the Dinosaurs”, although to me, this species looks like a toned-down Basilosaurus.
Beddard also mentioned the teeth being erectile and kept in cartilaginous sacs (?!?!). I haven’t seen this fact mentioned recently, so has it been disproven or is it really true and just poorly-known?
Flower W. (1872) On the recent Ziphoid whales, with a description of the skeleton of Berardius arnouxi. Trans R Soc Lond 8 203–234.
Beddard, F. (1900) A Book of Whales.