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McCoy V.E.,Yale University | Lamsdell J.C.,Yale University | Poschmann M.,Referat Erdgeschichte | Anderson R.P.,Yale University | Briggs D.E.G.,Yale University
Biology Letters | Year: 2015

Pterygotid eurypterids have traditionally been interpreted as active, high-level, visual predators; however, recent studies of the visual system and cheliceral morphology of the pterygotid Acutiramus contradict this interpretation. Here, we report similar analyses of the pterygotids Erettopterus, Jaekelopterus and Pterygotus, and the pterygotid sister taxon Slimonia. Representative species of all these genera have more acute vision than A. cummingsi. The visual systems of Jaekelopterus rhenaniae and Pterygotus anglicus are comparable to that of modern predatory arthropods. All species of Jaekelopterus and Pterygotus have robust crushing chelicerae, morphologically distinct from the weaker slicing chelicerae of Acutiramus. Vision in Erettopterus osiliensis and Slimonia acuminata is more acute than in Acutiramus cummingsi, but not to the same degree as in modern active predators, and the morphology of the chelicerae in these genera suggests a grasping function. The pterygotids evolved with a shift in ecology from generalized feeder to specialized predator. Pterygotid eurypterids share a characteristic morphology but, although some were top predators, their ecology differs radically between genera. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Mahler B.,University of Bonn | Schwermann A.H.,University of Bonn | Wuttke M.,Referat Erdgeschichte | Schultz J.A.,University of Bonn | Martin T.,University of Bonn
Palaeobiodiversity and Palaeoenvironments | Year: 2015

A series of actualistic experiments were conducted to reconstruct probable taphonomic scenarios for a fossil mole specimen from the Enspel locality. Extant Talpa europaea carcasses immersed in water initially floated at the water surface then sank after a few hours or remained floating. Soft tissues started to decompose immediately and concomitantly putrefaction gas was produced and accumulated inside the body. Consequently, the carcasses became bloated, and the submerged ones re-surfaced. Gas formation and decomposition of soft tissues accelerated with increasing temperature, as expected. The skeletons of primarily floating specimens successively disarticulated with ongoing decomposition. In moderately warm water (19 °C) disarticulation began with the phalanges of the feet, while in warmer water (27 °C), disarticulation started with the phalanges of the hands and the lower jaws. Skeletal components of the re-surfaced specimens successively sank until the entire skeleton was disarticulated. Applying these experimental results to a partial skeleton of the Oligocene mole Geotrypus antiquus from Enspel (Germany) suggests that carcass sank whole to the bottom of the lake and did not undergo an extended period of floatation. This interpretation is supported by the following characteristics: (1) upper and lower jaws in occlusion, (2) presence of distal hand elements and the left femur and (3) the positions of the elements of the anterior extremities. After decomposition of most or all soft tissues at the bottom of the lake an underwater current from the right side shifted some bones to the left side of the body axis, while the humeri and the still-articulated skull stayed in their original anatomical position. © 2015, Senckenberg Gesellschaft für Naturforschung and Springer-Verlag Berlin Heidelberg.

Smith K.T.,Senckenberg Institute | Wuttke M.,Referat Erdgeschichte
Palaeobiodiversity and Palaeoenvironments | Year: 2012

Much has been written about the palaeoenvironment of the middle Eocene fossil Lagerstätte of Messel, Germany, and of the taphonomy of the vertebrates found in it, but taphonomic phenomena among the reptiles in this locality are virtually unstudied. The iguanid Geiseltaliellus maarius is the most common lizard species in Messel. We present taphonomic data for this species and analyse it. Specimens of G. maarius can be divided into three preservation classes, one of which is distinguished purely by decompositional phenomena. Most specimens sank quickly to the bottom of Lake Messel after entering it, but one floated for some time prior to emplacement. In theory, overlying pressure should not preclude the accumulation of gases of decay in submerged carcasses. In one specimen, such gases appear to have built up intracoelomically for many weeks, but did not cause the carcass to rise because of overlying water pressure. Eruption of the gases through the oral and cloacal openings, possibly initiated by a coincident turbidity current, scattered the bones of the skull, the pelvic region, and the proximal part of the tail. G. maarius had evolved a form of intervertebral urotomy (pseudoautotomy), which is indicative of arboreal habits. The waxy substance adipocere, formed after breakdown of fat, has been neglected in discussions of taphonomy, but may constitute an important factor in stabilising carcasses and enabling three-dimensional preservation before diagensis. © 2011 Senckenberg, Gesellschaft für Naturforschung and Springer.

More or less complete and articulated skeletons of fossil air-breathing vertebrates with a long neck and tail often exhibit a body posture in which the head and neck are recurved over the back of the animal. Additionally, the tail is typically drawn over the body, while the limbs have a rigid appearance. In palaeontological literature, this "opisthotonic posture" of such fossils still requires a causal interpretation in an etiological context. According to this hypothesis, there is a presumption of a cerebral disorder generating perimortem muscle spasms that are preserved by rapid burial or other sequestration of a skeleton in the fossil record. We re-evaluate this "opisthotonic posture hypothesis" by analysing the non-avian theropods Compsognathus longipes and Juravenator starki from the famous South Franconian plattenkalks of the Upper Jurassic Solnhofen Archipelago. Decay experiments with the extant domestic fowl Gallus gallus L. and analysis of the theropods' constructional morphological constraints reveal that the opisthotonic posture is not a peri- but a postmortem phenomenon. By analysing the timeline of decomposition, it is possible to recognise different stages of decay, depending on the varying decay resistance of soft tissues. Adipocere formation must have blocked further decay until embedding was completed by minimal sedimentation. Analyses of the palaeoenvironment of the basins of the Solnhofen Archipelago show that the conditions of deposition of individual basins cannot be considered to be similar, even inside the same time frame. Therefore, a generalised approach of looking at the depositional setting must be excluded. Assumptions by Faux and Padian (2007) that the accepted palaeoenvironmental reconstruction of the Solnhofen Fossillagerstätte has to be questioned in the light of the opisthotonic posture hypothesis enforce the need for a review of palaeoecological factors of the Franconian Plattenkalks from a taphonomic perspective. © 2012 Senckenberg, Gesellschaft für Naturforschung and Springer.

Smith K.T.,Senckenberg Institute | Wuttke M.,Referat Erdgeschichte
Palaeobiodiversity and Palaeoenvironments | Year: 2015

Ecological interactions in deep time can be elucidated by direct evidence, such as gut contents, from fossil deposits of exceptional preservation (referred to as Konservat-Fossillagerstätten). We have analysed isolated, microvertebrate-containing pellets from the upper Oligocene lake deposit of Enspel, Germany, which are unusually abundant at this location, and identified these, on the basis of content and corrosion pattern, as casts of a bird of prey. The pellets contained the remains of a minimum of one to six prey individuals each. The main prey species were rodents, but other vertebrate prey include cyprinid fishes, frogs and anguimorph lizards. This is the first record of a lizard from Enspel. A seed was also present in one pellet, which possibly was being carried by the co-preserved rodent. It is unlikely that any of the four bird species known from Enspel produced the pellets. One hypothesis to explain their occurrence in the middle of the lake involves subaerial dessication of the pellets in gullies on the crater wall, followed by transport of the then-buoyant pellets by flowing water. © 2015, Senckenberg Gesellschaft für Naturforschung and Springer-Verlag Berlin Heidelberg.

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