June 25th 2013, zoologists in The Netherlands were alerted by a report of a dead bottle-nosed dolphin (Tursiops truncatus) washed ashore in an inland estuary just south of Rotterdam. This dolphin is a very rare species in The Netherlands, even in the nearby open sea. Photographs, posted on www.waarneming.nl (now removed, but reproduced here), indeed show a dead mammal-like creature. But was it a dolphin? Experts later concluded it was to small to be Tursiops truncatus and identified it as a harbour porpoise (Phocoena phocoena), still a rare find in inland waters.
Staff members of the Natural History Museum Rotterdam could not relocate the mammal and considered it ‘lost for science’.
The next day, locals found the cadaver [pictured below] and (probably) correctly identified it as a dead dog.
Thanks to Jo Polak, for reporting the dead dolphin, and later identifying it as a dog. Also thanks to www.waarneming.nl for updating the identification into ‘unknown mammal‘ because (dead) dogs can not be entered into their database.
BONUS: Kompanje, E.J.O. (2001) – Review of strandings and catches of Tursiops truncatus (Mammalia: Cetacea, Odontoceti) in the Netherlands between 1754 and 2000 – Deinsea 8: 169-224