Anna Lindström

Early Cambrian record of failed durophagy and shell repair in an epibenthic mollusc

Predation is arguably one of the main driving forces of early metazoan evolution, yet the fossil record of predation during the Ediacaran–Early Cambrian transition is relatively poor. Here, we present direct evidence of failed durophagous (shell-breaking) predation and subsequent shell repair in the Early Cambrian (Botoman) epibenthic mollusc Marocella from the Mernmerna Formation and Oraparinna Shale in the Flinders Ranges, South Australia. This record pushes back the first appearance of durophagy on molluscs by approximately 40 Myr.

Late Palaeozoic foliage from China displays affinities to Cycadales rather than to Bennettitales necessitating a re-evaluation of the Palaeozoic Pterophyllum species

The epidermal anatomy of Pseudoctenis samchokense is described revealing non-bennettitalean characters of these leaves from the Permo-Carboniferous of China (and Korea). The specimens were originally described as Pterophyllum samchokense suggesting a bennettitalean affinity. They can no longer be considered bennettitalean since their cuticles lack the distinctive brachyparacytic stomata of that clade. Pterophyllum was originally erected as a morphogenus for segmented leaves from the Mesozoic and has subsequently been clearly assigned to the Bennettitales. The segmented leaves from the Permo-Carboniferous of Shanxi and Hebei, China described herein require a new ordinal and generic assignment since the non-bennettitalean cuticular characters documented reinforce the uncertainties in attribution of any foliage older than Late Triassic to the Bennettitales. Based on leaf-architecture and epidermal anatomical characters, the specimens are at best assigned to the cycadalean genus Pseudoctenis. This genus was formerly known only from Mesozoic rocks. Consequently, the specimens are highly significant, as they are among the oldest known vegetative remains of cycads. Re-evaluation of the affinities of all specimens assigned to Pterophyllum from Palaeozoic rocks is thus essential. Based on a review of other Permian—Carboniferous fossil leaves assigned to Pterophyllum, we conclude that none yet reveals definitive bennettitalean characters.

Managing troubles-talk in the renegotiation of a loan contract:

This study focuses on troubles-tellings in calls to the Swedish Board for Student Support, where the caller wants to negotiate the repayment contract of a student loan. The study relates to research on the organization of troubles-tellings in institutional interaction, and the overall question of how talk about money is a delicate matter that is shaped by moral concerns. The data consist of 94 calls in which the caller proposes either a reduction or a temporal suspension of repayment. The analysis shows that troubles-tellings are launched to account for past failures to adhere to the contracted payment schedule. These tellings are met with minimal responses, which in turn engender a shift towards solutions that resonate with the institutional agenda. The study explores the resources recruited by the participants to deal with a potentially stigmatic situation by formulating the troubles as merely temporary and projecting a future situation where payments are made on time.

Shell repair and mode of life of Praenatica gregaria (Gastropoda) from the Devonian of Bohemia (Czech Republic)

Shell repair and mode of life of Praenatica gregaria (Gastropoda) from the Devonian of Bohemia (Czech Republic)

Shell breakage in two pleurotomarioid gastropods from the Upper Carboniferous of Texas, and its relation to shell morphology

Abstract Shells of two widespread Palaeozoic pleurotomarioid gastropods from North America, Worthenia tabulata (Conrad, 1835) and Glabrocingulum grayvillense (Norwood & Pratten, 1855), were scanned for evidence of shell breakage in the form of injuries repaired during the snails life. Such injuries can result from a variety of agents but failed predation is normally believed to be the most common cause. Characteristic of these gastropods and other pleurotomarioids is the open slit in the aperture margin, which generates a selenizone. The length of the slit is often thought to influence the strength of the shell in the aperture area and through this, the frequency of shell repair. However, the large difference in shell repair frequency observed between Worthenia and Glabrocingulum cannot be attributed to the length of the slit alone. Apparently, Worthenia was much better suited to withstand attack than Glabrocingulum because of its shorter slit and general shell morphology. A higher spire and the relatively prominent angulations in the aperture seem to limit the extent of fractures effectively. The slit and the selenizone strongly influence the shape and location of shell injuires. The observed patterns show a remarkable similarity with repaired injuries in extant pleurotomarioids.