I found this 4.75 inch long silicified sponge? branch after dissolving a large piece of the Permian (Leonardian) Fort Apache Limestone from the Schnebly Hill Formation east of Payson, Arizona in four gallons of pool acid. Only about five percent of the fossil was exposed.
The outer part is denser than the sometimes nearly hollow interior. One cross section shows two tubular structures with denser edges. No organized patterns suggesting a bryozoa or coral branch are present.
Do you think that this is a piece of a branching sponge?
Top photo: cross section is 1 inch.
@Arizona Chris
Branch is 4.75 inches long.
Bottom photo: cross section is 0.5 inch across.