Burrows are crucial for the survival of vertebrates, providing shelter from unfavourable climate and predators, but also forming a safe space for feeding, breeding, hibernation, or aestivation. Nevertheless, the origin and early evolution of fossoriality is scarcely investigated. The early Permian Bromacker locality (Tambach Formation, Germany) is worldwide known for its exceptional vertebrate skeletal and footprint record. Nevertheless, vertebrate burrows were only briefly reported so far. New excavations in the frame of the BMBF-funded Bromacker project (2020-2025) yielded an unexpectedly large amount of potential vertebrate burrows of different size and morphology. Large-sized (about 30-40 cm wide), low-dipping burrows ending in oval chambers with dense concentrations of broad scratch traces at the bottom and at the sides, were found in high concentrations in fine-grained and cross-stratified sandstone layers. Some of the burrow infills contain tetrapod remains, including Diadectes, Orobates, and Martensius. Somewhat smaller (about 12 cm wide), long, low-dipping burrows ending in pentagonal chambers, characterise the fluvial sandstones at the bottom and at the top of the succession. Furthermore, small (about 5 cm wide), low-dipping burrows displaying branching, thin scratch traces and large quadrangular chambers, were found in the cross-stratified sandstone at the top of the succession. A further type of small (about 3-5 cm wide), simply built burrows, vertical or slightly dipping, characterise the laminated mudstone facies. This exceptional abundance and diversity of potential vertebrate burrows makes the Bromacker locality a key area for studying the early evolution of fossoriality, likely linked to survival strategies during early Permian global warming.

Recent excavations at the early Permian Bromacker locality (Thuringian Forest, Germany) yielded body and trace fossil finds that shed new light on diadectid track-trackmaker correlation. A partially articulated skeleton assigned to Diadectes absitus includes a pes – which was absent in the type material of this species – and, in contrast to the expected similarity to North American Diadectes and the track type Ichniotherium cottae, the foot proportions of D. absitus are in better agreement with co-occurring Ichniotheirum sphaerodactylum tracks. Furthermore, despite the differences in bone proportions, the ratio of trunk length (distance between shoulder and hip joints measured along the vertebral column) to foot size was similar in both species, D. absitus and O. pabsti. To infer the likely sequence of footfalls that defines the gait pattern of the track producer, the skeletal proportions of D. absitus and O. pabsti were put in relationship to the footprint proportions and trackway pattern of I. sphaerodactylum. Based on a large sample of I. sphaerodactylum trackways from the Tambach Formation and assuming different degrees of lateral trunk bending and of flesh cover for fitting the autopodia into the footprints, we find that the skeletal proportions of both possible producers support a lateral sequence walk or even a pace gait instead of a common walking trot (the latter was assumed in previous models of O. pabsti as the producer of I. sphaerodactylum). According to our results, the type of gait should be taken into account as a critical variable in future models of diadectid walk.

Fossoriality is common among land vertebrates and offers many ecological advantages. Evidence for burrowing lifestyles dates back to the Paleozoic era, but large tetrapod burrows are rare, and their producers remain largely unknown. One of the oldest known large vertebrate burrows (up to ~70 cm wide) comes from the Cisuralian Bromacker locality in Thuringia, central Germany. Recent excavations at the Bromacker site have uncovered new material of this trace fossil, previously informally named “Megatambichnus”, including ramps, horizontal tunnels, and terminal chambers. These structures display distinct scratch traces, often in sets of five. Such features allow for a confident classification of the trace fossils as tetrapod burrows. Here, we take advantage of the unique simultaneous occurrence of trace fossils and exceptional preserved skeletons at the Bromacker locality to correlate potential producers with the “Megatambichnus” burrows. For that, we introduce a new method comparing burrow dimensions with the body sizes and proportions of fossil taxa from the same locality. In addition, we investigate the potential fossorial adaptations of the taxa that fit the burrow dimensions, based on osteological features observed in modern fossorial tetrapods. Our results show that diadectids, such as Orobates pabsti and Diadectes absitus, and caseids, such as Martensius bromackerensis, match the burrow dimensions and show skeletal traits consistent with a fossorial lifestyle, making them reliable tracemaker candidates. Further morphometric analyses of the trace fossils and skeletons, combined with biomechanical and histological approaches, will be conducted to more precisely identify the producer.

Bromalites — fossilised digested remains — are of high scientific value as they offer insights into the behavioural ecology and physiology of extinct organisms, including evidence of predator-prey interactions. These remains can be preserved either internally within body fossils (e.g., oralites, gastrolites, cololites) or externally, as separate entities (e.g., coprolites, regurgitalites). They are exceptionally rare, especially from Palaeozoic terrestrial deposits. The early Permian Bromacker locality in central Germany (Tambach Formation) yields outstanding fossilised vertebrate traces associated with skeletal remains. Here, we describe the first two bromalites from the Bromacker locality, identified as a regurgitalite (fossilised vomit) and a coprolite (fossilised faeces). Elemental mapping reveals differences of phosphorous concentration between the two bromalites, allowing a clear distinction between coprolitic and regurgitated remains. While the coprolite contains cranial and post-cranial elements of the small trematopid temnospondyl Rotaryus gothae, the regurgitalite preserves skeletal remains assignable to at least four different taxa: Eudibamus cursoris, Thuringothyris mahlendorffae, a diadectid and a dissorophoid. Based on their size and content, we hypothesise that these bromalites were most likely produced by a terrestrial apex predator, such as the sphenacodontid Dimetrodon teutonis or the varanopid Tambacarnifex unguifalcatus, previously recorded from the Bromacker locality. These findings provide new insights into the behavioural ecology and trophic structure of the Bromacker ecosystem and of terrestrial tetrapod ecosystems in general.

A wealth of studies show that the paleoecosystem recovered from the early Permian Bromacker locality of central Germany was unique and differed from coeval North American (NA) fossil assemblages. The latter mostly represented lowland environments with perennial rivers and tetrapod communities of aquatic to terrestrial taxa dominated by large carnivores. On the contrary, Bromacker paleoclimate was highly seasonal with ephemeral water bodies. Its tetrapod fauna was exclusively terrestrial, with abundant herbivores, but scarce and small predators.

Environmental conditions are expected to impact the growth strategies and lifestyle adaptations of tetrapods. However, this has rarely been reported for early Permian tetrapod communities. Here we investigate, for the first time, the long bone histology of the six largest tetrapod species recovered from Bromacker (i.e. Seymouria sanjuanensis, Diadectes absitus, Orobates pabsti, Dimetrodon teutonis, Martensius bromackerensis, Tambacarnifex unguifalcatus), with the aim to infer their life history traits and compare them to NA relatives.

Preliminary observations reveal that most specimens found at Bromacker consist in subadult to adult individuals, with few young juveniles. Unlike all other investigated species, Bromacker diadectids exhibit highly remodeled long bone cortices; a feature potentially related to fossorial adaptations. D. teutonis shows nearly avascular and thin bone walls, differing from the well vascularized and thicker cortices of its diminutive NA counterpart, D. natalis. Overall, Bromacker species show relatively slower growth rate than their NA relatives. Local environmental conditions might explain these contrasting growth strategies.

Trematopids are a monophyletic group of Permo-Carboniferous dissorophoid temnospondyls from North America and Europe. These anamniotes were well adapted for a terrestrial lifestyle, but most species are only known from a single specimen. The scarcity of well-preserved fossils, combined with anatomical variation among taxa, poses significant challenges for resolving trematopid taxonomy and relationships. This study re-evaluates Rotaryus gothae, a trematopid from the lower Permian Bromacker locality in central Germany, using computed tomography (CT) and 3D digital segmentation. This detailed examination revealed previously obscured anatomical features and led to the identification of novel characters. Notable findings include the presence of an internarial fenestra and new insights into the mandibular and palatal anatomy, including new information on the dentition. Furthermore, a comprehensive set of postcranial elements was uncovered, including a previously unknown, nearly complete and articulated right hindlimb. These discoveries provide valuable new insights into the locomotor morphology and functional anatomy of Rotaryus gothae. Bayesian and parsimony analyses were conducted using two matrices, respectively. The results support the trematopid identification ofRotaryus, but it acts as a wildcard taxon with varying phylogenetic positions depending on dataset and method used. Furthermore, the broader relationships within Olsoniformes remain unresolved. This new data has led to a better anatomical understanding of Rotaryus but also highlights the difficulties posed by limited specimen availability and high morphological variability. This study underscores the necessity of re-evaluating early tetrapods with modern tools to refine unresolved phylogenetic questions and provide a foundation for future investigations.