The Vertebrate Fauna of the Lower Keuper Albertibank (Erfurt Formation, Middle Triassic) in the Vicinity of Schwäbisch Hall (Baden-Württemberg, Germany)
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Palaeodiversity 4: 223–243; Stuttgart 30 December 2011. 223 The vertebrate fauna of the Lower Keuper Albertibank (Erfurt Formation, Middle Triassic) in the vicinity of Schwäbisch Hall (Baden-Württemberg, Germany) HANS HAGDORN & RAOUL J. MUTTER Abstract In the vicinity of Schwäbisch Hall, the Lower Keuper (Ladinian) Albertibank is characterized by a small-scale lateral facies change and a distinctive fauna composed of ostracods, fi shes, and lower tetrapods, comprising the remarkably abundant polzbergiid actinopterygian Serrolepis suevicus, small unidentifi ed species of ?Redfi eldii- formes and Saurichthyidae, the small brackish water shark Lonchidion, two dipnoans, a large coelacanthiform, the temnospondyl amphibians Mastodonsaurus and Gerrothorax, a small nothosaur, and the “rauisuchian” Batra- chotomus. Facies and fauna give evidence of an occasionally dry falling lacustrine environment. The dentition of Serrolepis is indicative of a specialized durophagous diet, presumably on ostracods. K e y w o r d s : Lower Keuper, Albertibank, Ladinian, Southwest Germany, vertebrate fauna, durophagous diet. Zusammenfassung Die Albertibank des Unterkeupers (Ladinium) im Raum Schwäbisch Hall ist durch kleinräumlichen lateralen Fazieswechsel und eine Fauna von Ostrakoden, Fischen und niederen Tetrapoden gekennzeichnet. Besonders häu- fi g ist der polzbergiide Actinopterygier Serrolepis suevicus, seltener sind unbestimmte kleine Arten der ?Redfi eldii- formes und der Saurichthyidae, der Brackwasserhai Lonchidion, zwei Dipnoer-Arten, ein großer Coelacanthiforme, die temnospondylen Amphibien Mastodonsaurus und Gerrothorax, ein kleiner Nothosaurier und der „Rauisuchier“ Batrachotomus. Fazies und Fauna lassen auf ein gelegentlich trockenfallendes lakustrines Habitat schließen. Die Bezahnung von Serrolepis legt eine spezialisierte durophage Ernährung, vermutlich von Ostrakoden nahe. Contents 1. Introduction .........................................................................................................................................................223 2. Geological background .......................................................................................................................................227 2.1. Stratigraphy and depositional environment ..............................................................................................227 2.2. Lithofacies and fossil distribution of the Serrolepisbank .........................................................................228 3. The Serrolepisbank Fauna ..................................................................................................................................228 3.1. Material and methods ................................................................................................................................228 3.2. Invertebrates ..............................................................................................................................................228 3.3. Vertebrates .................................................................................................................................................228 4. Palaeoecology ......................................................................................................................................................237 4.1. Palaeoecology of the Serrolepisbank .........................................................................................................237 4.2. Comparable habitats from the Germanic Triassic ....................................................................................239 4.3. Palaeoecological signature of “Serrolepis lakes” ......................................................................................240 5. References ...........................................................................................................................................................240 1. Introduction processes after their deposition (NITSCH 2005). The sand- stones, containing heavy minerals of Cadomian age (PAUL In the Germanic Triassic, the Lower Keuper or Letten- et al. 2008), prograded from Scandinavia´s Caledonian keuper (‘Lettenkohle’ of the older literature) occupies a Mountains over the entire Central European Basin as far transitional position between the marine limestones of the southward as the German-Swiss border area along the Upper Muschelkalk and the predominantly terrestrial sed- upper reaches of River Rhine. Their channel systems may iments of the Middle Keuper. The Lettenkeuper is charac- incise into older deposits as deep as the top of the Upper terized by a small scale cyclical change of (1) sandstones Muschelkalk. While the 40–60 m thick fl uvio-lacustrine and claystones with limnic-fl uviolacustrine and deltaic- facies dominates the northern and central parts of the Ger- palustrine fl oras and faunas; (2) carbonates and claystones manic Basin, the Lower Keuper becomes increasingly car- with brackish or marine faunas. In Southwest Germany bonate-dominated and thins out to less than 20 m towards these carbonate beds may contain gypsum nodules or even Southwest Germany and Switzerland (NITSCH 2005, relics of halite crystals, indicating evaporitic- pedogene ETZOLD & SCHWEIZER 2005). 224 PALAEODIVERSITY 4, 2011 Based on nine minor cycles that can be interpreted as suevicus DAMES, 1888 that gave reason for the present orbital 100 ka and 400 ka cycles, a duration of approxi- investigation. Recently, the genus Serrolepis has regained mately 1.2 Ma has been estimated for the Lower Keuper attention upon the location of the type material in the col- by MENNING et al. (2005) and NITSCH (2005). Assuming lection of the Humboldt Museum für Naturkunde in Ber- eight cycles, KOZUR & BACHMANN (2008) estimate a dura- lin by LOMBARDO & TINTORI (2004). Additional new fi nds tion of 0.8 Ma. The Lower Keuper is of early late Ladinian of articulated material are described in detail elsewhere (Longobardian) age. It was deposited under a dry, subtrop- (MUTTER & HAGDORN, in prep.). The present paper intends ical climate, with monsoonal winds bringing periodic pre- to give an overview of facies and fauna of the Albertibank cipitation from the Western Tethys (PARRISH 1999). around Schwäbisch Hall, to compare it to nearby outcrops, The Lower Keuper of the Hohenlohe and Schwäbisch and to reconstruct the palaeoecological position of Ser- Hall Counties (Northeast Baden-Württemberg) is famous rolepis in this depositional environment. for its vertebrate Lagerstätten that yielded diverse reptile, As a common and abundant faunal element, Serrole- amphibian, and fi sh faunas, among them Mastodonsau- pis must have played an important role in the food chain rus, the largest amphibian ever found, or Batrachoto- of certain Lower Keuper water bodies. Its characteristic mus, the best known rauisuchian reptile (SCHOCH 2006). deep scales with strongly serrated posterior edges were However, it was the small polzbergiid fi sh Serrolepis collected for the fi rst time by QUENSTEDT during fi eld work Fig. 1. Geological sketch map of the vicinity of Schwäbisch Hall (northeast Baden-Württemberg) with position of Albertibank out- crops. Kastenhof (1), Scheuermann Quarry (2), Hirsch Quarry (3), Taubenhof Quarry (4), Michelbach-Leitenäcker (5), Wilhelms- glück Quarry (6). For locality data see appendix 1. HAGDORN & MUTTER, VERTEBRATE FAUNA OF THE LOWER KEUPER ALBERTIBANK 225 Fig. 2. Lithostratigraphic units of the Lower Keuper in northern Baden-Württemberg with major Serrolepis occurences. Modifi ed after BRUNNER & BRUDER (1981). 226 PALAEODIVERSITY 4, 2011 Fig. 3. Lower Keuper outcrops in the vicinity of Schwäbisch Hall. – a. Abandoned Scheuermann Quarry with Lower Keuper overly- ing Upper Muschelkalk limestones. The Hauptsandstein in inter-channel facies. b. Serrolepisbank in the Scheuermann Quarry with halite voids indicating pedogene processes. c. Lower Keuper at Wilhelmsglück with Hauptsandstein (HS), Albertibank (AB, approx. thickness 1 m) with two carbonate beds, the upper one being the Serrolepisbank (S), Sandige Pfl anzenschiefer (SP) with coaly marls at base, and Anthrakonitbank (A) with marine bivalves (Hoernesia socialis). HAGDORN & MUTTER, VERTEBRATE FAUNA OF THE LOWER KEUPER ALBERTIBANK 227 for the ‘Geognostische Spezialkarte von Württemberg’ Scheuermann and Hirsch quarries in Schwäbisch Hall- (geological map of Württemberg) in 1874 and 1879 in sev- Steinbach that make up one large outcrop today (Fig. 3). For eral quarries around Schwäbisch Hall (QUENSTEDT 1880; a combined section see ZELLER (1907) and BRUNNER (1973: Fig. 1). In this area, the fi nely grained, greenish Lower fi g. 21). The majority of the new material under description Keuper Sandstone was quarried in many pits. During the has been collected from fallen blocks in these quarries, 19th century the quarrying activities increased, especially which are nowadays protected as a natural reserve area. along the valley of River Bibers (HAGDORN 1990). There, claystone and some carbonate beds overlying the working Institutional abbreviations stone were removed and put aside on dumps that became MHI Muschelkalkmuseum Hagdorn Ingelfi ngen famous for their abundant vertebrate fossils, especially for SMNS Staatliches Museum für Naturkunde Stuttgart large dipnoan (ceratodont) tooth plates. The most fossilif- Acknowledgements erous locality, which yielded also temnospondyl bones and We thank RONALD BÖTTCHER (Stuttgart) for assistance with rauisuchian teeth, was the Kastenhof Quarry at the Läm- specimens in his