What on Earth is this?
OK, It does not look like a fungus. just going by the single close up photo - I'm pretty sure it is an abandoned bumblebee nest (or that of some similar social insect).  These bees often nest out of sight under logs or under the ground. Below is a link that may help you with a positive identification. I hope this provides at least a hint. Maybe you can fill in the blanks from your knowledge of your local fauna in Portugal.

http://www.bumblebee.org/lifeCcolDev.htm