Agglutinated foraminifera—a group of predominantly marine Rhizarian protists—are recorded from the Ediacaran, although their origin might be rooted in the Cryogenian based on the molecular clock assumptions and evidence of agglutinated tests of uncertain affinities from post-Sturtian carbonates of Namibia and Mongolia. The present endeavour has been triggered by the finding of Sigmoilopsis schlumbergeri (Silvestri, 1904) (Miliolida: Hauerinidae) along the KwaZulu-Natal Bight (SW Indian Ocean); the tests of this foraminifera are found to be disproportionally enriched with rutile when compared to the surrounding sediment. From as early as Ediacaran, agglutinated foraminifera are known to selectively incorporate a broad array of particles into their tests. Among such inclusions, fairly common are grains of heavy minerals, viz. various aluminosilicates, anatase, ilmenite, magnetite, pseudobrookite, pyrite, pyrrhotite, rutile, titanite, titanomagnetite and zircon. Amidst them, titanium-bearing minerals are of particular curiosity, since TiO₂ exhibits cytotoxicity through oxidative stress at lowered pH, which is observed in some intracellular compartments and pericellular space of calcifying protists. It has been suggested that agglutinated foraminifera may enrich theirs test with heavy minerals to boost up their specific weight and, hence, their stability in the sediment, yet this assumption does not explain molecular mechanisms involved in such behaviour. Based on literature data, we hypothesize that Ti⁴⁺ ions, or other reactive titanium species (RTS), may be involved in a series of biochemical processes that lead to the increased intracellular pool of Ca²⁺ and phosphorylation, which in turn facilitate polymerization of actin, formation of reticulopodia, and biomineralization. Adverse effects of RTS are alleviated by an elevated intracellular pH during calcification in foraminifera and by deployment of metallothioneins for detoxification. Inclusion of titanomagnetite in the Ediacaran Palaeopascichnus linearis (Fedonkin, 1976) may support our idea that RTS might have played a certain role in the evolution of biomineralization in foraminifera.