Is guano the new umbilica?
Extraneous detail: I think it was always guano that the umbilica was living in — as some kind of parasite.
*Your* umbilicus, of course, is the 'cord' that once attached you, by the navel, to a placenta inside your mum. Unless you are a lizard person, but we won't go into that. It's not a body part found in any bird or reptile. SV calling whatever-it-was an umbilica was a mistake.
"I'm pretty sure ["umbilica"] a sort of organism, like a parasite, not actual feces. Parazoa is an animal sub-kingdom."
— clonedclone,
In Zyconnic's MO1 forum thread 'Guide to Pickables'
The pickable 'umbilica' from MO1 was (according to the Lore) classed as one of the Parazoa. Those are animals-- sort of. Nearly.
"[A] taxon with sub-kingdom category that is located at the base of the phylogenetic tree of the animal kingdom."
— Wikipedia
Translation: As 'animals' go, this one still lives in Mother Nature's basement.
Sponges (in our wordl) are (at least sometimes) classed as Parazoa, though not all Parazoa are sponges. By nature, they could look like almost anything, or, like 'almost nothing' —
"...the most primitive forms, characterized by not having proper tissues or that, in any case, these tissues are only partially differentiated. ...lack muscles, nerves and internal organs, which in many cases resembles a cell colony rather than a multicellular organism itself."
—
https://en.wikipedia.org/wiki/Parazoa
— so it makes a kind of sense that the skin they take on in Mortal games is just 'bird scat'.