Unknow skull found in aquarium

[Neutronman]

Who knows of what kind of animal this skull is ?
I whas very wondered to find this in my aquarium, i dont know how it came in.
A mistery to me, specialy because of the strange shape of the skull, i mean that spike.
I think that this spike or horn must be located close to a nostral, its a peace of a skull.
The littele fragment is the lower part of the skull, where the spine whas.

Just klik the link for the foto's

http://www.aquaforum.nl/cgi-bin/ultimatebb.cgi/topic/65/1360.html?

[Neutronman]

The horn, spike, angle, spike could also be located by the ear, i think.
Please help.
I live in Holland, and this animal does not live here for sure.