The Bromacker Biota: Regurgitalites and the Evolution of Opportunistic Predation in Early Terrestrial Ecosystems

 

1. Executive Context: The Permian Terrestrial Revolution

The Early Permian (Cisuralian), approximately 290 million years ago, represents the most critical window into the genesis of fully terrestrial vertebrate ecosystems. It was during this interval that tetrapods definitively transcended their ancestral reliance on semiaquatic margins to colonize the vast, arid continental interiors of Pangaea. The Bromacker locality, situated within the Tambach Formation of Thuringia, Germany, functions as a world-wide unique fossil site that bridges the historical gap between ichnotaxa (trackway evidence) and skeletal remains. Historically, reconstructing precise food web interactions and autecology in these inland environments has been hampered by taphonomic biases; unlike aquatic settings where depositional stasis often preserves biological interactions, terrestrial environments rarely yield direct evidence of trophic hierarchy. However, the 2026 identification of a high-fidelity bromalite has provided an unprecedented "moment locked in time," offering a high-resolution look at the mechanics of Permian predation and the colonization of the continental interior.

2. The Bromacker Locality: A High-Fidelity Paleoecological Archive

The Bromacker sandstone, a key unit of the Tambach Formation, serves as a superior archive for trophic research due to its unique paleogeographic position in the central region of the supercontinent Pangaea. Far removed from the marine-influenced coastlines that characterize much of the Paleozoic record, this upland valley ecosystem was subject to rapid burial events in thin layers of sandstone and mud, which effectively "locked in" ephemeral biological events.

The scientific value of this site is best understood by contrasting it with the broader Permian record:

Feature	Standard Fossil Record	The Bromacker Advantage
Skeletal Integrity	Scattered, isolated, and weathered elements.	Articulated, complete skeletons (e.g., the "Loving Pair").
Ichnological Association	Trackways found in isolation from track-makers.	Direct association of skeletal remains and contemporaneous trackways.
Taphonomic Resolution	Focus on durable body fossils; loss of trace data.	Preservation of bromalites (coprolites and regurgitalites).
Ecological Context	Coastal or semiaquatic fluvial systems.	True upland, water-independent continental interior.

The resolution of the Bromacker data has been significantly enhanced by the 2020–2026 collaborative research initiative involving the Museum für Naturkunde Berlin, the Friedrich-Schiller-University Jena, the Stiftung Schloss Friedenstein Gotha, and the UNESCO Global Geopark Thuringia Inselsberg–Drei Gleichen. This interdisciplinary effort has synthesized field excavation with micro-analytical rigor to transform geological stability into a lens for viewing the most ephemeral of biological events: the specific contents of an apex predator’s last meal.

3. Anatomy of a Discovery: The Oldest Terrestrial Regurgitalite

In 2026, research led by Rebillard et al. identified a walnut-sized (approximately lime-sized) sandstone lump as the oldest terrestrial regurgitalite currently known. While traditional skeletal remains provide a census of a biota, a regurgitalite offers a "photograph of the past," capturing the exact contents of a digestive tract prior to the completion of the metabolic cycle.

To analyze the specimen without compromising its structural integrity—as several constituent bones are less than an inch in length—researchers employed high-resolution micro-CT scanning. This allowed for the digital extraction and 3D modeling of 41 individual bone fragments. Crucially, while 41 fragments were present, the high-fidelity scans allowed the team to definitively attribute 25 of those fragments to specific prey species.

The classification of the specimen as a "regurgitalite" rather than a "coprolite" (fossilized feces) is substantiated by several diagnostic taphonomic signatures:

• Geochemistry: Micro-analytical surveys revealed the absence of a phosphatic matrix in the surrounding sediment. This is a critical indicator; whereas coprolites exhibit high phosphorus concentrations due to the prolonged residence time of mineralized fecal matter, the Bromacker specimen lacks this chemical signature.
• Morphology: The specimen comprises a random, tight grouping of angular, intermingled skeletal fragments. This contrasts with the massive, cylindrical, and regular morphology typical of coprolites formed during passage through the colon.
• Taphonomy: The bone lamellae show a distinct lack of "gastric etching" or acid-induced corrosion. This indicates the material was expelled rapidly—likely as a cohesive pellet—before stomach acids could significantly degrade the skeletal tissue. Furthermore, the alignment of long bones within the mass suggests it was expelled as a singular, unified bolus.

This physical evidence transitions the research from a study of taphonomic artifacts to the identification of the specific organisms participating in this 290-million-year-old trophic event.

4. Reconstructing the Meal: Taxonomic Identification of Prey and Predator

Identifying the specific prey species within the regurgitalite is essential for mapping the architecture of the first inland food webs. By comparing the 25 identifiable 3D-scanned fragments to the skeletal archives at the Museum für Naturkunde, Rebillard et al. (2026) identified three distinct prey animals within this single meal:

• Thuringothyris mahlendorffae: A small, lizard-like reptile reaching roughly 3.5 inches in length.
• Eudibamus cursoris: A specialized, 4-inch-long bipedal reptile characterized by high-speed motility.
• Unidentified Diadectid: A limb bone from a juvenile herbivore related to Diadectes. While adult diadectids could reach 2 feet in length, this specimen represents a much smaller individual, highlighting the predator's ability to target the young of larger species.

The predator responsible for this event is narrowed to two primary candidates based on contemporaneous presence in the Bromacker valley: the iconic sail-backed synapsid Dimetrodon teutonis and the monitor-lizard-like Tambacarnifex unguifalcatus. Both were apex synapsids, belonging to the lineage that eventually produced mammals. The diversity of species within this single cluster provides the first verified snapshot of these animals co-occurring in time and space—literally surviving in the same habitat within a window of a few days or even hours.

5. Opportunistic Predation and Trophic Complexity

The presence of three taxonomically distinct species within a single regurgitalite challenges the traditional assumption of strict niche specialization in Permian apex predators. The 2026 Bromacker data provides definitive evidence of opportunistic feeding behavior.

Rather than functioning as specialized hunters, these synapsids were generalists, exploiting whatever terrestrial biomass was available—from the high-motility, fast-moving Eudibamus to the juveniles of the bulky, herbivorous Diadectes. This indicates a complex, non-specialized trophic structure where the predator utilized a high-motility hunting strategy to navigate a variety of ecological niches within the valley.

This "Ecological Filtering" effect underscores a fundamental dichotomy in early land systems: the emergence of high-motility predators versus the diverse, often "low-motility" herbivores they consumed. Related research by Young, Maho, and Reisz (2026) using tooth-mark analysis on juvenile Diadectes skeletons further corroborates these direct trophic interactions. Together, these findings suggest that the ability to target diverse prey was the primary evolutionary driver for the successful colonization of the continental interior.

6. Evolutionary Implications: The Inland Expansion of Tetrapods

The Permian period represents the strategic era when vertebrate life successfully decoupled from "semiaquatic margins" to dominate "inland terrestrial environments." The 2026 findings synthesize a new narrative of synapsid dominance facilitated by their ability to exploit diverse, purely terrestrial prey sources.

While older ecosystems remained tethered to water bodies for primary productivity, the Bromacker ecosystem reveals a food web that is entirely land-based. In the Pangaean interior, where resource patchiness and fluctuating environmental conditions were the norm, the "motility" of predators and the "opportunism" of their feeding strategies were essential. This flexibility allowed synapsids to survive and thrive far from the coast, establishing the foundational structures for modern terrestrial food webs. This "moment locked in time" via a regurgitalite bolus proves that the ability to exploit varied, water-independent niches was the key to the vertebrate conquest of land.

7. Synthesis and Future Directions in Bromalite Research

The 2026 Bromacker findings represent a milestone in paleoecology, validating the oldest terrestrial regurgitalite as a definitive record of opportunistic apex predation. This single specimen has provided more data on predator-prey co-occurrence than decades of isolated skeletal finds, proving the necessity of high-resolution taphonomic analysis.

The future of the field lies in the "inexhaustible" potential of the Bromacker project. As we continue to deploy micro-CT and sophisticated geochemical surveys, the focus will shift toward the identification of "pseudopathologies"—bone abnormalities caused by diagenetic or taphonomic processes that can mimic disease. As recommended by the methodological rigor of Siviero et al. (2026), the application of histological analysis and micro-CT remains the gold standard for distinguishing biological reality from taphonomic artifact. Ultimately, these ancient "moments" bridge the gap between ephemeral biological interactions and the large-scale evolutionary transitions that define the history of life on Earth.