Scientific importance of the Fossillagerstätte Bromacker

(Germany, Tambach Formation, Lower Permian)

 

Preamble

 

Our understanding of the evolution of the earliest amniotes during the time span 320 to 270 million years ago on the Pangaea supercontinent is known from only very restricted types of depositional environments, most of which are in North America. The fossil locality Bromacker (Fossillagerstätte Bromacker, Bromacker Quarry) in the Lower Permian Tambach Formation near Tambach-Dietharz, central Germany, has developed during the last 20 years to be the most important and productive fossil locality for Lower Permian, terrestrially adapted tetrapods outside USA. The Bromacker locality produces the best preserved terrestrial vertebrate fossils from the Lower Permian time period (about 290 million years ago).

Significantly, the locality provides the example of strictly terrestrial amniote ecosystem. The diversity of the fossils and the fact that they are all terrestrial animals (no fish or aquatic amphibians have been found in nearly thirty years of excavation) indicates that it represents the only fully documented example of an initial stage in the evolution of the modern terrestrial vertebrate ecosystem; that is, a trophic system or food chain in which herbivorous tetrapods dominated in diversity, abundance, and biomass in comparison to the apex predators, and thus, fulfilled the role as the major source of direct introduction of plant food into the animal food chain. Thus, the herbivores and carnivores coexisted in a natural community as early as the Lower Permian. Therefore, it is possibly the most important localities worldwide for our understanding of the paleontology and ecology of basal amniotes and their near relatives.

 

Location of the Bromacker

 

The Bromacker locality is an active site of paleontological investigations, about 1,5 km north of the small town Tambach-Dietharz and about 20 km south of the town Gotha in the Thuringian Forest in central Germany. Around the area of the Bromacker are found active sandstone quarry of the TRACO Company, remains of former quarries that were active about 50 to 150 years ago and the quarry of our currently fossil site.

 

Excavation and research history of the Bromacker locality

 

The scientific history of the Lower Permian fossil locality Bromacker began about 125 years ago with the fossil collector Heinrich Friedrich Schäfer (1839-1930), who in 1887discovered the first sandstone block with a tetrapod footprint that was used at a construction site in the city of Gotha. It was later realized that the fossil came originally from a sandstone quarry (Bromacker) near Tambach in the Thuringian Forest.

From about 1890 to 1908 Prof. Wilhelm Pabst, curator of the natural scientific collection of the Herzogliches Museum in Gotha became engaged in intensive collecting and description of the first tetrapod footprints from different Lower Permian fossil localities in the Thuringian Forest, especially from the locality Bromacker near Tambach. The Bromacker fossil collection of tetrapod footprints has grown in Gotha to more than 180 superbly preserved specimens (Pabst 1895, 1908, Voigt 2002).

Later in the 1950s to the 1970s Prof. Hermann Schmidt (1892-1978), Göttingen, Prof. Arno Hermann Müller (1916-2004), Jena, and Prof. Hartmut Haubold (*1941), Halle, continued the study of the tetrapod footprints, as well as the invertebrate trace fossils from the Tambach Sandstone (Schmidt 1959, Müller 1954, 1955, Haubold 1971, 1972, 1973a, b).

With the discovery of the first vertebrate bone and additional invertebrate fossils (Conchostraca) at the Bromacker by the geologist Thomas Martens (*1952) in the summer of 1974, he began annual excavations in the fine, clastic, reddish brown siltstones above the Bromacker Sandstone (upper part of the Tambach Sandstone, Martens et al. 2009). From 1975 -1991 he discovered together with his father and various helpers the first skeletal evidence of a protorothyridid, diadectid, trematopid and Seymouria outside of North America. During this time Martens initiated contacts with vertebrate paleontology specialists in the USA and Germany. Prior to the political change (reunification of Germany) he published the results of his discoveries from the Bromacker (Martens 1975, 1980, 1982, 1988, 1989, 1990, Martens, Schneider & Walter 1980, Boy & Martens 1991).

In 1992 Martens was awarded a Museum Specialist Scholar grant by the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania, USA, that paid all of his travel and per diem expenses for 6 months while in the USA to begin a collaborative research program with Dr. David S Berman (Curator, section of Vertebrate Paleontology) to study the Bromacker vertebrate fossils. Beginning in 1993 und until 2010 the Bromacker team, including paleontologists and volunteers from Canada, USA, Slovakia, and Germany, have had 18 very successful summer excavating seasons, each averaging about four weeks.

Important discoveries between 1993 and 2010 were the first completely articulated skeletons of a new species of herbivorous diadectid Diadectes absitus ( first record of genus outside of the USA), a new species and genus of bolosaurid reptile, Eudibamus cursoris, two closely associated skeletons of Seymouria sanjuanensis, locally referred to the “Tambach Lovers” (known otherwise only from the USA), a new genus and species of herbivorous diadectid, Orobates pabsti, the sphenacodontid early mammal-like reptile Dimetrodon teutonis (genus known otherwise only from the USA), two new genera and species of amphibian trematopids, Tambachia trogallas and Rotaryus gothae (members of the family otherwise known from the USA), the dissorophoid, Georgenthalia clavinasica, the varanopid synapsid, Clavifalcatus carnifex, and three skeletons of the oldest known, undescribed new species of herbivorous caseid synapsid. Additionally, Martens in 2008, discovered first fossils in the city of Tambach-Dietharz, the second site in the Tambach Formation to yield vertebrate fossils.

 

Depositional setting of the Bromacker Fossillagerstätte

 

The Tambach Formation, approximately more than 200 m thick, is part of the terrestrial Lower Permian or Upper Rotliegend sequence in the Thuringian Forest, which consists of three units; in ascending order they are the Bielstein Conglomerate, Tambach Sandstone, and Finsterbergen Conglomerate. All three units consist of terrestrial fluvial redbeds (conglomerates, sandstones, silt- and claystones) deposited in a small intramontane basin as part of the Variscan orogeny. According to EBERTH et al. (2000), these units were deposited in an upland, internally drained basin, the Tambach Basin, that had an original aerial extent of about 200-300 km2.

Most of the fossils are concentrated in the Bromacker Sandstone and the Bromacker Horizons in transition between the approximately 100 m thick Tambach Sandstone and the overlaying approximately 50 m thick Finsterbergen Conglomerate of the Tambach Formation. The lower fossil horizon at the Bromacker, the approximately 10 m thick Bromacker Sandstone contains the well-preserved tetrapod footprint fauna (Haubold 1971, 1973b, Voigt et al. 2007) and the majority of the invertebrate trace fossils and plants fossils (Haubold 1973a, Martens 1975, 1982). The overlaying fossil horizon, the approximately 1-6 m thick Bromacker Horizon no.I has yielded in the last 35 years of excavation over 50 complete or nearly complete skeletons of 13 species of a terrestrially adapted vertebrates and more than 6 species of insects and diplopods, as well as a high number of conchostraca (Martens 1983, Martens et al. 2009).

The fossils were deposited near in Tambach Basin center, which was dominated by an extensive area of low relief of sheetflood-derived alluvium with scattered, local, ephemeral lakes and ponds and streams. The climate was tropically warm year round with subseasonal to seasonal cycles of rainfall and drying with freezing during the winter nights (Martens 2007). Stream channels resulting from brief flooding events created the Bromacker Sandstone containing mud cracks and trace fossils. The paleoenvironmental pictures of the Tambach Basin explain the absence to date of fish and aquatic amphibian fossils. The depositional setting also indicates that the Bromacker vertebrate fauna consisted solely of individuals living within the Tambach Basin, and thus represents one of the few, if any, examples of a purely autochthonous Lower Permian vertebrate assemblage.

 

Bromacker vertebrate Fauna

 

The Bromacker locality has long been known for its superb tetrapod trackways (Pabst 1895, 1908; Müller 1954, 1955; Haubold 1971, 1973, 1998, Voigt et al. 2007).

The international scientific Bromacker team has published during last 20 years over 20 peer-reviewed papers in high-profile journals and 24 abstracts presented at international scientific meetings describing the geology of the Tambach Basin and its vertebrate fossils. During this time the team uncovered an area of about 500 m² of the Bromacker Horizon no. I, which is about 5 % of the fossil-bearing horizon (Anderson et al. 2008, Berman & Martens 1993, Berman et al. 1998, 2000a, b, 2001, 2004a, b, Boy & Martens 1991, Martens 1990, Müller et al. 2006, Sumida et al 1998). In addition to publications on new taxa, members of the team have also produced a series of papers describing the ontogeny of Seymouria sanjuanensis (Klembara et al., 2005, 2006, 2007) based on Bromacker specimens. Of the approximately 50 or more partial-to-complete skeletons from the Bromacker, about 80 % were collected since 1993. The Bromacker is the first Paleozoic fossil site where it is possible to associate firmly tracks with their track-making vertebrates (Voigt et al. 2007).

In 2008 the vertebrate fossils were discovered from a new site in the city of Tambach-Dietharz, which indicates we have not fully realized the full fossiliferous potential of the Bromacker area. From this site we recovered a partial skeleton of a diadectid, most likely Diadectes absitus, a common component of the Bromacker fauna, and a new ostodolepid microsaur amphibian, the first ostodolepid to be recorded from outside the USA (Henrici et al. 2009).

The Bromacker vertebrate fauna is unique it lacking an aquatic-to-semi aquatic component, and instead is represented by a high number and variety of herbivores and a low number of apex predators, documenting for the first the existence of an early evolution stage of a modern terrestrial ecosystem. It is derived from a unique, upland terrestrial habitat that includes a variety of small to medium-sized highly terrestrial amphibians, basal amniotes, and reptiles that includes the following taxa:

 

AMPHIBIA (ANAMNIOTA)

LEPOSPONDYLI

MICROSAURIA

Family OSTODOLEPIDAE

Tambaroter carrolli Henrici et al. gen. & sp.

TEMNOSPONDYLI

DISSOROPHOIDEA

Family TREMATOPIDAE

Tambachia trogallas Sumida et al., 1998, n. gen. & sp.

Rotaryus gothae Berman et al., 2011, n. gen. & sp.

Family DISSOROPHIDAE

Undescribed new species

Family Amphibamidae

Georgenthalia clavinasica Anderson et al., 2008, n. gen. & sp.

SEYMOURIAMORPHA

Family Seymouridae

Seymouria sanjuanensis Vaughn, 1966 (Berman & Martens, 1993; Berman et. al., 2000b)          

DIADECTOMORPHA

Family DIADECTIDAE

Diadectes absitus Berman et al., 1997, n. sp.

Orobates pabsti Berman et al., 2003, n. gen. & sp.

REPTILIA (AMNIOTA)

CAPTORHINOMORPHA

Family PROTOROTHYRIDIDAE

Thuringothyris mahlendorffae Boy & Martens, 1991, n. gen. & sp.

PARAREPTILIA

Family BOLOSAURIDAE

Eudibamus cursoris Berman et al., 2000a, n. gen. & sp.

SYNAPSIDA

CASEASAURIA

Family CASEIDAE

Undescribed new species

EUPELYCOSAURIA

Family SPHENACODONTIDAE

Dimetrodon teutonis Berman et al., 2001, n. sp. (Berman et al. 2004)

Family VARANOPSEIDAE

Tambacarnifex unguifalcatus Berman et al., 2014, n. gen. & sp.

 

Table I. Preliminary minimum number of individual counts of Bromacker taxa. Inferred herbivorous, insectivorous, and carnivorous feeding habits indicated by H, I, and C, respectively. Taxa are divided into three size-range categories, small (S), medium (M), and large (L), based on maximum snout-vent lengths (see Table II).

 

Bromacker Vertebrate Taxa                                                    minimum number of individuals

 

Tambachia trogallas (trematopid amphibian) (I/C) (M)                                                    1

Rotaryus gothae (trematopid amphibian) (I/C) (M)                                                          1

New, undescribed dissorophid amphibians (I) (S)                                                           2

Seymouria sanjuanensis (seymouriamorph amphibian) (I/C) (M)                                   4

Georgenthalia clavinasica (amphibamid amphibian) (I) (S)                                            1

Diadectes absitus (diadectomorph, reptile) (H) (L)                                                       13

Orobates pabsti (diadectomorph, reptile) (H) (L)                                                            5

Thuringothyris mahlendorffae (captorhinid reptile) (I) (S)                                             10

Eudibamus cursoris (bolosaurid reptile) (H) (S)                                                             2

Dimetrodon teutonis (synapsid reptile) (C) (L)                                                               2

A currently being undescribed new caseid (synapsid reptile) (H) (L)                             4         

Tambacarnifex unguifalcatus (varanopseid, synapsid reptile) (C) (L)                            1                                                        

 

 

Table II. Size categories of Bromacker taxa based on maximum snout-vent lengths.

Small (8-13 cm):

Thuringothyris                           8.0 cm

Eudibamus                               10.5 cm

New dissorophid                      13.0 cm

Georgenthalia                           8.0 cm

Rotaryus                                  13.0 cm

 

Medium (25-35 cm):  

Tambachia                               28.0 cm

Caseid                                     30.0 cm

Seymouria                                35.0 cm

 

Large (50-60 cm):

Orobates                                  53.0 cm

Dimetrodon                               55.0 cm

Diadectes                                 55.0 cm

Clavifalcatus                            50-60 cm

 

Paleoecology of Bromacker locality

 

The Bromacker vertebrate fossil assemblage is strikingly unique in comparison to those of the highly fossiliferous, wide-spread Early Permian deposits of the USA in: 1) the total absence of aquatic and semi-terrestrial forms,

2) the greatly reduced abundance and diversity of primitive basal synapsids (“pelycosaurs”) that fulfilled the role of top predators, and

3) the high abundance and diversity of the herbivorous taxa.

That is, the composition of the vertebrate assemblage of the Bromacker and the relative abundances of its taxa are difficult to reconcile with current knowledge of the well-documented examples of the Early Permian mixed terrestrial-aquatic ecosystem in the USA. The explanation given here for these unique features is that the vertebrate inhabitants of the upland terrestrial setting of the Tambach Basin document a unique Early Permian ecosystem, which we hypothesize represents an initial stage in the development of the modern terrestrial ecosystem, the few possible examples of which are poorly documented.

 

Age of the Fossils

The terrestrial Tambach Formation was deposited as the lower part of the Upper Rotliegend.in the Thuringian Forest Basin representing and indicates an age of the lower part of the Lower Permian (Asselian – Sakmarian). Because of the absence of volcanic rocks and tuff layers in the Tambach Formation a radiometrical date isn´t   possible.

After discovering of the vertebrate fossil Seymouria sanjuanensis at the Bromacker locality the age of the fauna seems to be Wolfcampian as correlated with the type Lower Permian terrestrial stratigraphic section of Texas. In addition, the primitive evolutionary stages of the Bromacker Diadectes, Dimetrodon, and caseid indicates to us that the Bromacker fauna most be equivalent to the oldest known faunal elements of the Lower Permian Wolfcampian age of the Wichita Group in northern Texas.

However, this correlation is still not firm.

On the basis of the recently discovered tetrapods in the nearby town of Tambach-Dietharz, about 1,5 km from the Bromacker Quarry, Martens has determined that the fossiliferous horizon in which they preserved is part of the lowermost Finsterbergen Conglomerate, and thus are slightly younger than those at the Bromacker Quarry (Tambaroter carrolli and a diadectid).

 

Preservation, preparation, and ownership of the Bromacker fossils

 

The vertebrate fossils are extremely well preserved, have a white to bluish grey colored carbonate (calcite, aragonite) appearance, and are three-dimensional preserved with a natural deformation until 50 %. Many of the skeletons are complete and articulated skeletons, some in natural poses, and rarely with soft part impressions. Some taxa are uniquely represented by growth series.

About 90 % of the fossils were mechanical prepared during the past 20 years by Amy Henrici of the Carnegie Museum of Natural History, whereas about 10 % was done at the Museum der Natur Gotha with financial support from the DFG-projects. Proper preparation of the fossils requires long periods of time, but it is relatively easy, because of the rock matrix is easy to remove due to a thin surface coating of a soft, green reduced matrix.

About 40 % of the Bromacker fossils are property of Stiftung Schloss Friedenstein Gotha, Museum der Natur (majority of tetrapod footprint and invertebrate fossils). All fossils, discovered after 1992 belong to the state of Thuringia, but incorporation into the paleontological collections of the Museum der Natur Gotha (Thuringian law for preservation of sites of historic interest 1992, 2004).

 

Future projects (2018 – 2022)

 

1. Field work for the next seasons will involve continued excavation of the Bromacker Horizon no.1 at the Bromacker Quarry by the international Bromacker team, with the goals of expanding preliminary data documenting the uniqueness of the Bromacker vertebrate fauna and to find more complete skeletons of several taxa that are still poorly represented, most importantly the varanopid “pelycosaur” known by only a single, postcranial skeleton (future project with Museum of Natural Science Berlin).

2. On the basis of discovery of the new fossil horizon (Bromacker Horizon no. II) that is traceable by core drilling in the top of the Bromacker Quarry as well as in the center of Tambach-Dietharz, an international team plans to explore this horizon throughout the Tambach-Dietharz – Finsterbergen area in the coming years.

 

Scientific cooperation partners of the Bromacker project 1978 to 2017

* = long-time active cooperation Partners

 

Jason S. Anderson                   University of Calgary, Faculty of Veterinary Medicine in Calgary, Kanada (vertebrate paleontologist, terrestrial amphibians) cooperation 2006-2008

Dr. David S Berman*                Carnegie Museum of Natural History, Pittsburgh, PA, USA (vertebrate paleontologist, vertebrates, tetrapodes) cooperation since 1992

Prof. Jürgen Boy                      Universität Mainz, Germany (vertebrate paleontologist, aquatic amphibians) cooperation 1985-1991

Dr: Andrej Čerňanský*               Comenius University, Bratislava, Slovakia Republic (zoologist, vertebrate paleontologist, aquatic amphibians and amniotes) cooperation 2000-2010

Dr. John Nyakatura                   Friedrich Schiller Universität Jena, Institut für Spezielle Zoologie und Evolutionsbiologie, Germany (biologist, the locomotor systems of recent and  fossil vertebrates) cooperation 2010-2014

Dr. Knuth Hahne                       Deutsches GeoforschungsZentrum Potsdam (GFZ) (geologist, geochemistry of the sediments) cooperation 2007-2010

Prof. Dr. Hartmut Haubold*       Universität Halle-Wittenberg, Germany (vertebrate paleontologist, tetrapod footprints) cooperation since 1996

Amy C. Henrici*                        Carnegie Museum of Natural History, Pittsburgh, PA, USA (preparator, vertebrate paleontologist, terrestrial tetrapods) cooperation since 1992

Dr. Horst Kämpf*                      Deutsches GeoforschungsZentrum Potsdam GFZ (geologist, variety of interests) cooperation 2001-2010

Richard A. Kissel                      University of Toronto, Canada (vertebrate paleontologist, diadectomorphs as part of his PhD dissertation) cooperation 1997-2002

Dr. Jozef Klembara*                 Comenius University, Bratislava, Slovakia Republic (zoologist, vertebrate paleontologist, aquatic amphibians) cooperation 2000-2010

Dr. Thomas Martens*                Museum der Natur, Stiftung Schloss Friedenstein Gotha, Germany, paleontologist, invertebrates, trace fossils of vertebrates and invertebrates, inorganic sediment marks, excavation management Bromacker 1978-2010

Dr. Johannes Müller                  Museum für Naturkunde, Berlin, Germany (vertebrate paleontologist, amniotes) cooperation 2002-2006, cooperation 2006

Prof. Robert R. Reisz*              University of Toronto, Canada (vertebrate paleontologist, amniotes, Eupelycosauria) cooperation since 1996

Prof. Dr. Jörg Schneider           Bergakademie Freiberg, GDR (paleontologist, insects) cooperation 1979-1981

Prof. Stuart S. Sumida*            California State University, San Bernardino, CA, USA (vertebrate paleontologist, terrestrial amphibians, amniotes) cooperation since 1992

Dr. Sebastian Voigt                  Technische Universität und Bergakademie Freiberg, Germany (paleontologist, tetrapod footprints) cooperation 1999-2007

Dr. Harald Walther                    Bergakademie Freiberg, GDR (Paläontologe, trace fossils) cooperation 1979-1981

Dr. Ralf  Werneburg                  Naturhistorisches Museum, Schleusingen, Germany (vertebrate paleontologist, aquatic amphibians) cooperation 2006

 

Financial support for the Bromacker project (1990-2016)

 

DFG (German Science Foundation) project:                  MA 1472/1-2                 (1998-2001)

DFG project                                                                    MA 1472/3-4                 (2004-2007)

DFG project                                                                    MA 1472/5-1                 (2008-2009)

Graham Netting Fund, Carnegie Museum, Pittsburgh, USA                                (1993-1999)

Preparation work at the Carnegie Museum, Pittsburgh, USA                              (1992-2016)

National Geographic Society, USA                                                                  (1994-2003)

NATO grant, USA                                                                                            (1995-1998)

O´Neil Field Fund, Carnegie Museum, Pittsburgh, USA                                     (1995-1998)

City administration Gotha                                                                                (1978-2003)

Stiftung Schloss Friedenstein Gotha                                                                (2004-2010)

„Museumslöwen“club to support the Museum der Natur Gotha                           (2006-2010)

US-Konsulate Leipzig                                                                                      (2005-2010)

Thüringer Landesamt für Archäologische Denkmalpflege, Weimar                     (1996)

Rotary Club Gotha                                                                                          (2002-2010)

Volunteers                                                                                                      (1990-2010)

 

Public educational and media outreach of the Bromacker Project

​

The annual excavations of Bromacker Quarry by our research team has since 1993 received a great amount public attention through popular articles in local, national, international news papers and television reports. For more than four weeks each year more than 500 tourists, mostly families with kids, have visited the Bromacker Quarry.

Popular, semi-scientific, and scientific articles about the Bromacker research have been published in paleontology books, journals, and student textbooks. Pictures of Bromacker fossil have been used for book covers: Michael Benton, Vertebrate Paleontology, third edition, 2005 and Michel Laurin, Systématique, paléontologie et biologie évolutive moderne, 2008. Several TV stations have reported on our successes, in discovering skeletons that are referred to by the popular name “Ursaurier” (=primary saurian).

Exhibitions in the Museum der Natur Gotha have explored the importance of the Bromacker project in demonstrating a global distribution pattern of many of its vertebrates and providing irrefutable evidence that during the Early Permian North America and Western Europe were a continuous land mass. This has been done with long-term exhibits such as „Ursaurier zwischen Thüringer Wald und Rocky Mountains“(1997-2010) and short-term exhibits that explain the Bromacker project and displayed many of its fossils. Undoubtedly the most popular of the Bromacker fossils exhibit has been the two complete, articulated skeletons of Seymouria sanjuanensis preserved cheek-to-cheek that were given the popular name “the Tambach Lovers” by visitors to the Museum der Natur. Currently, Carnegie Museum of Natural History in Pittsburgh has a display of casts of the most important Bromacker vertebrates, which has been on display for several years.

 

 

Dr. Thomas Martens                 Dr. David S Berman and Amy C. Henrici           Prof. Stuart S. Sumida

Pfarrgasse 53                           Carnegie Museum of Natural History                 California State Univ.

Drei Gleichen                            Dep. Vertebrate Paleontology                            San Bernardino

Germany                                   Pittsburgh,USA                                                   USA 

 

July 2017