A new trace fossil Macroterebella hoffmanni nov. igen., nov. isp. occurs in Oxfordian and Aptian limestones of Romania, in the Central Dobrogea and the Rarău Mountains, respectively. It is a tubular, branched, and winding burrow (5–14 mm in diameter) displaying a thick wall (0.8–2 mm) with a micropeloidal texture. The Dobrogea burrows contain abundant calcite pseudomorphs after dolomite in the wall. A ferruginous halo occurs around burrows from Rarău. The burrow lumen resulted from burrowing by the tracemaker, most likely a polychaete worm of the family Terebellidae, while the wall is nonconstructional, and its formation was microbially mediated. Terebellids produce mucous-lined burrows, which are attractive for microbial activity which is geochemically important for metal adsorption and mineral nucleation. The micropeloidal texture of the Macroterebella wall is the result of bacterially mediated precipitation and possibly influenced by extracellular polymeric substances (EPS). Some microbes, especially sulphate-reducing bacteria producing extracellular polymeric substances (EPS) are able to mediate the formation of dolomite, and some microbial cells may be nucleation sites for dolomite. The lack of dolomite and the presence of a ferruginous halo around the burrows in the Rarău specimens may reflect different environmental geochemical conditions within these burrows compared with those from Dobrogea. This study confirms that microbes and organic matter in the mucous lining of burrows in a carbonate environment may play an important physicochemical role in the final appearance of trace fossils. Macroterebella nov. igen. can be considered as a trace fossil with a hybrid bioturbation/biosedimentary nature.

The morphology and architectural design of trace fossils are strongly influenced by substrate characteristics, organism anatomy, and burrowing behavior. In this study, we explore the influence of substrate moisture on preservation variants of mole cricket burrows and discuss its correspondence to previously described ichnogenera. Field observations were conducted on clayey and sandy substrates; burrows were described and photographed in situ, and laboratory analyses were performed on collected samples. Mole cricket burrows consist of branched, straight to sinuous tunnels with circular to semicircular cross sections and exhibit distinctive features on the inner walls that are influenced by substrate moisture and texture. Morphotypes were identified based on substrate characteristics, including well-developed pelletized roofs, subtle scratch traces, collapsed roofs, and lateral fringes. Understanding the impact of substrate moisture changes on the preservation and morphology of mole cricket burrows is essential for interpreting trace fossils in paleoenvironmental reconstructions. Besides providing insights into the modes of preservation and substrate conditions of mole cricket burrows, this study also compares their preservation variants with those of Protovirgularia and Sphaerapus.