Lost in plain sight for 160 years - Frank Haes’ forgotten Thylacine

ABSTRACT Until recently, the 1864 Haes photograph was believed to be the only known surviving image of a living Thylacine (Thylacinus cynocephalus) from the 19th century. This image is preserved as both a stereo view and lantern slide. In April 2025, a collector of historic photographs of London Zoo noticed a mystery mammal in the background of a stereo view from Haes second series taken in 1865. The image was that of a two toed sloth (Bradypus didactylus) taken in front of the kangaroo sheds where the Thylacine was housed at the Regents Park Zoo (London). On examination, the head of a Thylacine can be clearly seen entering the frame behind the sloth, yet this remarkable discovery had gone unnoticed in plain sight for 160 years. The image is reproduced here and the provenance and identity of the Thylacine photographed discussed.