I had a whole collection of these black and white Seguso animals which I recently sold off, so I'll fill you in on them as best I can, though Javier also has a nice collection and may add a bit more later on.
There appear to be two variations of these, the earlier ones which date from the 1960's have applied "black" facial features, nose, ears etc, and are always unsigned apart from the labels. There is a later variation that lack the applied facial features and from the pictures it appears that yours may well fall into this category and these date from the 1980's, possibly running into the early 1990's, and some have acid studio marks.
There was also a smaller range of animals made in red and black and all of these I've had have a shinier outward finish, though with applied features and all have the labels and are unsigned.
They are usually described as marbled pasta glass.
I would list it under the Murano section making sure you include Archimede Seguso in your title.
Hope all this helps