Pomoria Fedonkin, 1980[1][2] Tribrachidium heraldicum is a tri-radially symmetric fossil animal that lived in the late Ediacaran (Vendian) seas.

[citation needed] The generic name Tribrachidium is derived from combination of the Ancient Greek: τρία (tria, "three") + Latin: brachium ("arm") + diminutive suffix -idium.

The specific name T. heraldicum references the similarity of the pattern of this fossil with the well-known heraldic triskelion design, such as the coat of arms of the Isle of Man.

[11] In a 2015 study, Rahman et al. proposed that Tribrachidium heraldicum used a rare 'gravity settling' mode of suspension feeding based on computational fluid dynamics simulations, which showed that water flow was directed passively by the arms, funneling it towards three depressions (‘apical pits’) where water flow slowed down so that food particles would fall out of suspension.

[16] M. Fedonkin has shown that the fossil of Tribrachidium is an imprint of the upper side of the animal's body, with some elements of its external and internal anatomy.