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Bonebed of Lamerden (Germany) As Palaeoenvironment Indicators in the Germanic Basin

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Bonebed of Lamerden (Germany) As Palaeoenvironment Indicators in the Germanic Basin Open Geosci. 2015; 7:755–782 Research Article Open Access Cajus G. Diedrich * The vertebrates from the Lower Ladinian (Middle Triassic) bonebed of Lamerden (Germany) as palaeoenvironment indicators in the Germanic Basin DOI 10.1515/geo-2015-0062 sis; palaeoenvironment; palaeobiogeography; Germanic Basin; Central Europe Received January 28, 2013; accepted May 21, 2015 Abstract: A marine/limnic vertebrate fauna is described from the enodis/posseckeri Bonebed mixed in a bivalve shell-rich bioclastic carbonate rudstone at the eastern 1 Introduction coastal margin of the Rhenish Massif mainland at Lamer- den (Germany) within the western Germanic Basin (Cen- Middle Triassic vertebrate skeleton or bone localities and tral Europe). The condensation layer is of Fassanian (La- bonebed layers are known from all over the “Pangaean dinian, Middle Triassic) in age. The vertebrate biodiver- Globe”, especially Northern America, Europe, and China sity includes ve dierent shark, and several actinoptery- (Figure 1A) [e.g. [1–7]]. In north-western Germany, a higher gian sh species represented by teeth and scales. Abun- density of vertebrate sites (Figure 1B) is the result of dant isolated bones from a small- and a large-sized pachy- many active limestone quarries which expose bonebeds th pleurosaur Neusticosaurus species, which can be com- within dierent layers since the 19 century. The old- posed as incomplete skeletons, originate from dense pop- est described historical sites are in southern Germany ulations of dierent individual age stages. Important fa- near Bayreuth (Bavaria) and became famous with the cies indicator reptiles are from the thalattosaur Blezin- world-wide rst sauropterygian monograph published by geria ichthyospondyla which postcranial skeleton is re- Hermann von Meyer [8]. Those localities are known to- constructed hypothetically using additional postcranial day to contain several bonebed layers in the Illyrian- bones from similar aged various German localities. The Fassanian limestone series which were recently revised vertebrate biodiversity of the enodis/posseckeri bonebed in their stratigraphy, facies and vertebrate biodiversity for of Lamerden reect a limnic/uvial freshwater inuenced several still open old quarries [7]. After the rst historic fauna (amphibians/terrestrial and marine reptiles) with wave of Triassic reptile discoveries in southern Germany, dominance of normal saline marine inuences. Macro- the few younger “Muschelkalk/Keuper-Grenzbonebeds” algae meadow adapted placodont reptiles are absent in (= Boundary Bonebeds, Fassanian/Longobardian bound- Lamerden, as well as open marine-adapted ichthyosaurs, ary) became famous in more recent times. Those bonebeds supporting a lagoon with fresh water inuence position at contain single tooth and bone remains of a mixed ma- the Rhenish Massif mainland coast. In those contempo- rine/brackish/limnic vertebrate fauna which was never ex- ranous brackish lagoons, which seem to be isochronous cavated systematically (no square meter documentation) to northern Tethys lagoons of the Kalschieferzone at the at several southern German quarrys, such as in the most Monte San Giorgio (Switzerland/Italy), small pachypleu- famous locality Crailsheim [1–3]. Systematically excavated rosaurs were abundant prey in both regions for reptile bonebeds have been started to be analysed from dier- predators, especially large paraxial swimming alligator ent “Upper Muschelkalk” levels of northern Germany more habitus-like Paranothosaurus, which even contain stom- recently. At Bissendorf, the compressus Bonebed of the ach contents of pachypleurosaurs. Ilyrian-Fassanian boundary [9] is also important for the fa- cies/vertebrate fauna comparisons presented herein. The Keywords: Bonebed; vertebrate biodiversity; facies; Lon- pulcher/atavus Bonebed with its historical larger collec- gobardian (Middle Triassic); vertebrate taphocoeno- tions from Bad Sulza (central Germany) was also restudied *Corresponding Author: Cajus G. Diedrich : PaleoLogic, Private Research Institute, Zdice, Czech Republic, website: www.paleologic.eu, E-mail: [email protected] © 2015 C.J. Diedrich, published by De Gruyter Open. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License. The article is published with open access at www.degruyter.com. Unauthenticated Download Date | 2/2/16 9:56 PM 756 Ë C.J. Diedrich [10], and is compared to the new site presented herein, the tooth/scale over all excavation areas. One square metre enodis/posseckeri Bonebed from the central German site was mapped during each excavation campaign, which is Lamerden (Figure 1B). All the above mentioned bonebed quite well representative of the complete excavated area. localities are important for the understanding of verte- This bonebed does not show any clear scour trough, tidal brate assemblages in dierent facies, bathymetry and channel or ripple mark oriented concentrations or any salinity conditions which nally are useful for palaeoenvi- sorting. Statistical tests (= NISP) at two other squares (cf. ronmental reconstructions (palaeobiogeographical maps) Figure 3A), all chosen far from each others and during each and understanding of the palaeobiology of marine reptile excavation campaign, gave similar vertebrate (especially palaeopopulations of the Germanic Basin in Central Eu- sh remain) amounts. rope [cf. [7, 9]]. All bonebeds of the Germanic Basin are de- veloped in several dierent biostratigraphic (mostly at se- 2.2 Taphonomy of reptiles and amphibians quence boundaries, ceratite biozone boundaries) and geo- graphical (coastal reconstructions) positions and dierent The reptiles were mapped on surfaces of 4 and 160 square facies types [7, 9, 10], to which Lamerden contribute to a metres each (Figures 3-4). The problem of synsedimentary third type, besides the “shallow full marine/normal saline erosion by tempestitic channels overprinted the amount of bonebeds” of Bad Sulza, Bissendorf and Bayreuth. Finally nds in some areas (Figure 3A), which were not chosen for a discussion about Blezingeria can be added with very rare the sh/small reptile remain statistics. The large surface bone material from Lamerden and other sites of Germany. mapping (Figure 4) was similar chosen for an area, where the overlaying tempestite limestone bed did not reach and eroded into the bonebed. In some areas, the marls be- 2 Material and methods neath the bonebed were bioturbated by crustacean ich- nites of the type Thalassinoides (Figure 3A), which also in- 2.1 Excavations in Lamerden uenced the bonebed layers in some areas (cf. Figure 3). In total, 2,036 vertebrate remains, including teeth, scales and The lithostratigraphy, carbonate sedimentology and bones, were excavated, prepared and inventoried (Table 1). macro-invertebrate assemblage were studied for the A statistics about the bone element presence/absence Lamerden section to separate small-scale sequences for analysing a possible current or general taphonomic and to understand the palaeoenvironment development sorting is problematic, because the partly weathered change within the high order transgressive-regressive se- bonebed did not allow a sieving to obtain the small cranial quence (Figure 2). Furthermore, several ceratites have and appendicular bones or teeth, especially of the small been collected from the outcrop walls, which allow pre- pachypleurosaurs. Therefore, all amphibian and reptile senting an updated high resolution biostratigraphy (Fig- material (teeth, bones) larger then 3 mm was selective used ure 2). for the bone taphonomy analyses which allow subdividing Three bonebed excavation campaigns, each about four stages of bone fragmentation (Figure 5D): 1. None - four-weeks long, were performed in the active quarry bones show no breakage nor edge polishing, 2. Low - bones Lamerden (Kalksteinwerk Lamerden of the Fischer GMBH are rarely broken (mostly ribs and at bone elements) and and CoKG) in 2003, 2005 and 2006. The bonebed was have sometimes rounded corners, 3. Medium - fragmenta- excavated systematically on large surfaces, in total of tion and rounded corners is more common, 4. High - the about 600 square metres, representing the largest Ger- bones are all incomplete, fragmented, and after this even man bonebed excavation in Upper Muschelkalk bonebeds. rounded at the margins, joints are missing, and mainly In 2003, four square metres (Figure 3), and in 2005 (160 most stable and thick bone parts remained. square metres, Figure 4), were mapped for the vertebrate The “composite experiment” of most abundant pachy- taphonomy and vertebrate biodiversity analyses (NISP = pleurosaur reptile bones (Figure 5D) reects the pres- bone per species). Any surface mappings sadly did not re- ence/absence of the entire body bone elements (except the sult in palaeocurrent information (also due to short bone smallest ones as result of excavation technique or preser- elements only – no complete ribs e.g.). A further detailed vation) and dominance of the larger bone material. This mapping of nds was not performed again in 2006, also to is similar to large Paranothosaurus, and Blezingeria re- rescue as much as possible larger bone material for the ver- mains, but dierent from the more fragmentary material of tebrate biodiversity analyses. The large amount of sh re- Nothosaurus, Simosaurus and especially Pistosaurus (Fig- mains, especially selachian teeth and less of actinoptery- ure 5D), which latter had longer transport durations or dis- gian teeth and scales, did not allow the mapping
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