I don’t know about the big trapezoid, but the little lineated piece certainly looks like vascular plant material. Land plant even. I find these in Middle Devonian shaley limestones, even those whose paleoenvironments had paleodepths below normal wave-base.
@nathan-newell and @sadie-mills I think my interpretation is going to partially hinge on the age (which I know isn’t the best practice but some place to start). While it appears there are ridges in part, they don’t seem continuous. Therefore, I do not interpret this as vasculature. Instead, I think this is a combination of the rock’s texture behind the fossil and the original material drying and shrinking during lithification. If we do interpret this as vasculature, then it might be good to consider the age. When we look at plants younger than Famennian there are two main groups of vascular plants: Lycopodophytina (or the club mosses) and Polypodiopsida (or Monilophyta, ferns and allies). The Lycopodophytina have microphylls (one strand of vasculature) and the Polypodiopsida have macrophylls (multiple or branching strands of vasculature). If we interpret the all of the ridges as vasculature then we rule out the lycopods and are left with the Monilophytes which don’t have parallel veination. This leads me to further believe it’s some sort of macroalgae (seaweed). My interpretation might change if it were 3D.