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Data from: Preservational bias controls the fossil record of pterosaurs
- 负责人：
- DOI：
- doi:10.5061/dryad.td570
- 摘要：
- Pterosaurs, a Mesozoic group of flying archosaurs, have become a focal point for debates pertaining to the impact of sampling biases on our reading of the fossil record, as well as the utility of sampling proxies in palaeo-diversity reconstructions. The completeness of the pterosaur fossil specimens themselves potentially provides additional information that is not captured in existing sampling proxies, and might shed new light on the group's evolutionary history. Here we assess the quality of the pterosaur fossil record via a character completeness metric based on the number of phylogenetic characters that can be scored for all known skeletons of 172 valid species, with averaged completeness values calculated for each geological stage. The fossil record of pterosaurs is observed to be strongly influenced by the occurrence and distribution of Lagerst?tten. Peaks in completeness correlate with Lagerst?tten deposits, and a recovered correlation between completeness and observed diversity is rendered non-significant when Lagerst?tten species are excluded. Intervals previously regarded as potential extinction events are shown to lack Lagerst?tten and exhibit low completeness values: as such, the apparent low diversity in these intervals might be at least partly the result of poor fossil record quality. A positive correlation between temporal patterns in completeness of Cretaceous pterosaurs and birds further demonstrates the prominent role that Lagerst?tten deposits have on the preservation of smaller bodied organisms, contrasting with a lack of correlation with the completeness of large-bodied sauropodomorphs. However, we unexpectedly find a strong correlation between sauropodomorph and pterosaur completeness within the Triassic–Jurassic, but not the Cretaceous, potentially relating to a shared shift in environmental preference and thus preservation style through time. This study highlights the importance of understanding the relationship between various taphonomic controls when correcting for sampling bias, and provides additional evidence for the prominent role of sampling on observed patterns in pterosaur macroevolution.
Data from: Skeletal completeness of the non?avian theropod dinosaur fossil record
- 负责人：
- DOI：
- doi:10.5061/dryad.37c840g
- 摘要：
- Non?avian theropods were a highly successful clade of bipedal, predominantly carnivorous, dinosaurs. Their diversity and macroevolutionary patterns have been the subject of many studies. Changes in fossil specimen completeness through time and space can bias our understanding of macroevolution. Here, we quantify the completeness of 455 non?avian theropod species using the skeletal completeness metric (SCM), which calculates the proportion of a complete skeleton preserved for a specimen. Temporal patterns of theropod skeletal completeness show peaks in the Carnian, Oxfordian–Kimmeridgian and Barremian–Aptian, and lows in the Berriasian and Hauterivian. Lagerst?tten primarily drive the peaks in completeness and observed taxonomic diversity in the Oxfordian–Kimmeridgian and the Barremian–Aptian. Theropods have a significantly lower distribution of completeness scores than contemporary sauropodomorph dinosaurs but change in completeness through time for the two groups shows a significant correlation when conservation Lagerst?tten are excluded, possibly indicating that both records are primarily driven by geology and sampling availability. Our results reveal relatively weak temporal sampling biases acting on the theropod record but relatively strong spatial and environmental biases. Asia has a significantly more complete record than any other continent, the mid northern latitudes have the highest abundance of finds, and most complete theropod skeletons come from lacustrine and aeolian environments. We suggest that these patterns result from historical research focus, modern climate dynamics, and depositional transportation energy plus association with conservation Lagerst?tten, respectively. Furthermore, we find possible ecological biases acting on different theropod subgroups, but body size does not influence theropod completeness on a global scale.
Data from: Evolution of the locomotory system in eels (Teleostei: Elopomorpha)
- 负责人：
- DOI：
- doi:10.5061/dryad.72403
- 摘要：
- Background Living anguilliform eels represent a distinct clade of elongated teleostean fishes inhabiting a wide range of habitats. Locomotion of these fishes is highly influenced by the elongated body shape, the anatomy of the vertebral column, and the corresponding soft tissues represented by the musculotendinous system. Up to now, the evolution of axial elongation in eels has been inferred from living taxa only, whereas the reconstruction of evolutionary patterns and functional ecology in extinct eels still is scarce. Rare but excellently preserved fossil eels from the Late Cretaceous and Cenozoic were investigated here to gain a better understanding of locomotory system evolution in anguilliforms and, consequently, their habitat occupations in deep time. Results The number of vertebrae in correlation with the body length separates extinct and extant anguilliforms. Even if the phylogenetic signal cannot entirely be excluded, the analyses performed here reveal a continuous shortening of the vertebral column with a simultaneous increase in vertebral numbers in conjunction with short lateral tendons throughout the order. These anatomical changes contradict previous hypotheses based on extant eels solely. Conclusions The body curvatures of extant anguilliforms are highly flexible and can be clearly distinguished from extinct species. Anatomical changes of the vertebral column and musculotendinous system through time and between extinct and extant anguilliforms correlate with changes of the body plan and swimming performance and reveal significant shifts in habitat adaptation and thus behaviour. Evolutionary changes in the skeletal system of eels established here also imply that environmental shifts were triggered by abiotic rather than biotic factors (e.g., K/P boundary mass extinction event).
Data from: Does exceptional preservation distort our view of disparity in the fossil record?
- 负责人：
- DOI：
- doi:10.5061/dryad.2b6n12q
- 摘要：
- How much of evolutionary history is lost because of the unevenness of the fossil record? Lagerst?tten, sites of exceptional fossil preservation, provide remarkable, yet distorting insights into past life. When examining macroevolutionary trends in the fossil record, they can generate an uneven sampling signal for taxonomic diversity; by comparison, their effect on morphological variety (disparity) is poorly understood. We show here that lagerst?tten impact the disparity of ichthyosaurs, Mesozoic marine reptiles, by preserving higher diversity and more complete specimens. Elsewhere in the fossil record, undersampled diversity and more fragmentary specimens produce spurious results. We identify a novel effect, that a taxon moves towards the centroid of a Generalised Euclidean dataset as its proportion of missing data increases. We term this effect ‘centroid slippage’, as a disparity-based analogue of phylogenetic stemward slippage. Our results suggest that uneven sampling presents profound issues for our view of disparity in the fossil record, but that this is also dependent on the methodology used, especially true with widely used Generalised Euclidean distances. Mitigation of missing cladistic data is possible by phylogenetic gap filling, and heterogeneous effects of lagerst?tten on disparity may be accounted for by understanding the factors affecting their spatiotemporal distribution.
Data from: Diversity and palaeoecology of the enigmatic genus Knebelia (Eucrustacea, Decapoda, Eryonidae) from Upper Jurassic plattenkalks in southern Germany
- 负责人：
- DOI：
- doi:10.5061/dryad.72mn4
- 摘要：
- For a long time, the genus Knebelia Van Straelen, 1922 has comprised two species of eryonid lobster, K. bilobata (Münster, 1839) and K. schuberti (Meyer, 1836), both recorded exclusively from Late Jurassic Lagerst?tten in southern Germany. Recently, the latter has been suggested to represent a juvenile individual of Cycleryon propinquus (Schlotheim, 1822). A re-examination of the type and new material has led to our rejection of that interpretation and confirmation of assignment of this species to Knebelia. Two specimens, both possessing short frontal lobes, from plattenkalks at Nusplingen (late Kimmeridgian) and at Solnhofen (early Tithonian), respectively, are here assigned to a new species, K. totoroi sp. nov. This new species and a review of K. bilobata have furnished new insights into the origin and function of the frontal lobes, which are expansions articulated to the front of the carapace. They probably functioned as rudders facilitating ‘tail-flip swimming’ as observed in the paddle-like antennae of extant scyllarids (Eucrustacea, Decapoda, Scyllaridae). The rudder-like lobes identified in Knebelia may therefore represent a case of convergent evolution.
Data from: Decaying of Artemia salina in clay colloids: 14-month experimental formation of subfossils
- 负责人：
- DOI：
- doi:10.5061/dryad.qj728
- 摘要：
- The mechanism that guides the formation of exceptionally preserved fossils with soft tissues variously displayed is a paramount challenge to paleontology. The key question for exceptional preservation is the nature of the slowdown of decay and acceleration of soft tissue mineralization. Here we report the experimental formation of subfossils of the brine shrimp Artemia salina (Crustacea, Branchiopoda), which were produced during 14 months of aging in a kaolinite clay sediment. EDS/SEM elemental analyses showed that the subfossils were preserved as thin clay-organic replicas that displayed fine anatomical details. Decomposition in the clay-colloidal solution established highly heterogeneous acidic conditions, with the lowest pH typically found in the vicinity of the buried organisms, and visually manifested in patchy coloration of the sediment. Elevated acidity is likely what ultimately slowed the decay. An acidic environment increases the rate of clay destruction and, consequently, the diffusion rate decline. As a result, the acidic products quickly accumulate around a buried body; this in turn inhibits bacterial proliferation, accelerates the acidic hydrolysis of clay and, accordingly, the release of tanning and mineralizing agents. The subfossils remained stable under experimental high pressure and temperature. These model subfossils exhibit features that are typical of some Lagerst?tten fossils preserved in fine-grained sediments.
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