Mark Williams

Impatiens glandulifera (Himalayan balsam) is a non-native plant species that has become widespread in the UK. Observational records indicate its arrival in the early 19th century as an ornamental plant, but it did not become widespread until the post WWII interval. In this paper, we demonstrate that I . glandulifera leaves a fossil signature in sediment cores from the River Soar in Leicestershire, with ²¹⁰ Pb dating confirming its primary palaeontological record from the 1930s, shortly after it was first recorded in this region, and is more persistent and abundant in core deposits since the 1960s–70s, after which it is known to have proliferated in the wider landscape. Changes in the associated pollen assemblages in the cores suggest that its spread impacts on other plants in the local community. The record of persistent occurrence of I . glandulifera in the cores can be used to correlate Anthropocene deposits between sites along the River Soar and could be aligned with the fossil signature of other non-native pollen, for example common ragweed ( Ambrosia artemisiifolia ) to provide a biostratigraphical tool for identifying and correlating Anthropocene deposits more broadly.

Geological evidence points to icehouse conditions during the Ediacaran Period (635 to 538.8 Ma) both before and during the emergence of animals in the fossil record. However, the temporal and spatial distributions of Ediacaran ice sheets are not well constrained due to uncertainties in palaeogeography, chronostratigraphy, and the depositional settings of candidate glaciogenic deposits. Here, we systematically evaluate the evidence for the depositional ages of candidate Ediacaran glaciogenic deposits and establish the likelihood that each deposit was formed by ice-driven processes using observation-driven weighting criteria. Our analysis supports the existence of discrete mid- and late Ediacaran icehouse intervals (MEIH and LEIH respectively), each followed by greenhouse conditions. Focussing on the older MEIH, we integrate our quality-controlled geological dataset with climate and ice sheet model simulations to characterise glacial conditions during this interval (~593 to 579 Ma), which encompasses the ‘Gaskiers glaciation’. Our results indicate that the MEIH was a Phanerozoic-style icehouse, with latitudinally-constrained and fluctuating ice sheets, marking a break from the preceding Cryogenian snowball Earth motif, and occurring before the first known appearance of animals in the fossil record. By mapping robustly identified glaciogenic deposits onto contrasting middle Ediacaran palaeogeographic reconstructions, we show how these deposits can be used to constrain hypotheses of Ediacaran continental configuration.

Geological evidence points to icehouse conditions during the Ediacaran Period (635 to 538.8 Ma) both before and during the emergence of animals in the fossil record. However, the temporal and spatial distributions of Ediacaran ice sheets are not well constrained due to uncertainties in palaeogeography, chronostratigraphy, and the depositional settings of candidate glaciogenic deposits. Here, we systematically evaluate the evidence for the depositional ages of candidate Ediacaran glaciogenic deposits and establish the likelihood that each deposit was formed by ice-driven processes using observation-driven weighting criteria. Our analysis supports the existence of discrete mid- and late Ediacaran icehouse intervals (MEIH and LEIH respectively), each followed by greenhouse conditions. Focussing on the older MEIH, we integrate our quality-controlled geological dataset with climate and ice sheet model simulations to characterise glacial conditions during this interval (~593 to 579 Ma), which encompasses the ‘Gaskiers glaciation’. Our results indicate that the MEIH was a Phanerozoic-style icehouse, with latitudinally-constrained and fluctuating ice sheets, marking a break from the preceding Cryogenian snowball Earth motif, and occurring before the first known appearance of animals in the fossil record. By mapping robustly identified glaciogenic deposits onto contrasting middle Ediacaran palaeogeographic reconstructions, we show how these deposits can be used to constrain hypotheses of Ediacaran continental configuration.

Geological evidence points to icehouse conditions during the Ediacaran Period (635 to 538.8 Ma) both before and during the emergence of animals in the fossil record. However, the temporal and spatial distributions of Ediacaran ice sheets are not well constrained due to uncertainties in palaeogeography, chronostratigraphy, and the depositional settings of candidate glaciogenic deposits. Here, we systematically evaluate the evidence for the depositional ages of candidate Ediacaran glaciogenic deposits and establish the likelihood that each deposit was formed by ice-driven processes using observation-driven weighting criteria. Our analysis supports the existence of discrete mid- and late Ediacaran icehouse intervals (MEIH and LEIH respectively), each followed by greenhouse conditions. Focussing on the older MEIH, we integrate our quality-controlled geological dataset with climate and ice sheet model simulations to characterise glacial conditions during this interval (~593 to 579 Ma), which encompasses the ‘Gaskiers glaciation’. Our results indicate that the MEIH was a Phanerozoic-style icehouse, with latitudinally-constrained and fluctuating ice sheets, marking a break from the preceding Cryogenian snowball Earth motif, and occurring before the first known appearance of animals in the fossil record. By mapping robustly identified glaciogenic deposits onto contrasting middle Ediacaran palaeogeographic reconstructions, we show how these deposits can be used to constrain hypotheses of Ediacaran continental configuration.

Geological evidence points to icehouse conditions during the Ediacaran Period (635 to 538.8 Ma) both before and during the emergence of animals in the fossil record. However, the temporal and spatial distributions of Ediacaran ice sheets are not well constrained due to uncertainties in palaeogeography, chronostratigraphy, and the depositional settings of candidate glaciogenic deposits. Here, we systematically evaluate the evidence for the depositional ages of candidate Ediacaran glaciogenic deposits and establish the likelihood that each deposit was formed by ice-driven processes using observation-driven weighting criteria. Our analysis supports the existence of discrete mid- and late Ediacaran icehouse intervals (MEIH and LEIH respectively), each followed by greenhouse conditions. Focussing on the older MEIH, we integrate our quality-controlled geological dataset with climate and ice sheet model simulations to characterise glacial conditions during this interval (~593 to 579 Ma), which encompasses the ‘Gaskiers glaciation’. Our results indicate that the MEIH was a Phanerozoic-style icehouse, with latitudinally-constrained and fluctuating ice sheets, marking a break from the preceding Cryogenian snowball Earth motif, and occurring before the first known appearance of animals in the fossil record. By mapping robustly identified glaciogenic deposits onto contrasting middle Ediacaran palaeogeographic reconstructions, we show how these deposits can be used to constrain hypotheses of Ediacaran continental configuration.

Geological evidence points to icehouse conditions during the Ediacaran Period (635 to 538.8 Ma) both before and during the emergence of animals in the fossil record. However, the temporal and spatial distributions of Ediacaran ice sheets are not well constrained due to uncertainties in palaeogeography, chronostratigraphy, and the depositional settings of candidate glaciogenic deposits. Here, we systematically evaluate the evidence for the depositional ages of candidate Ediacaran glaciogenic deposits and establish the likelihood that each deposit was formed by ice-driven processes using observation-driven weighting criteria. Our analysis supports the existence of discrete mid- and late Ediacaran icehouse intervals (MEIH and LEIH respectively), each followed by greenhouse conditions. Focussing on the older MEIH, we integrate our quality-controlled geological dataset with climate and ice sheet model simulations to characterise glacial conditions during this interval (~593 to 579 Ma), which encompasses the ‘Gaskiers glaciation’. Our results indicate that the MEIH was a Phanerozoic-style icehouse, with latitudinally-constrained and fluctuating ice sheets, marking a break from the preceding Cryogenian snowball Earth motif, and occurring before the first known appearance of animals in the fossil record. By mapping robustly identified glaciogenic deposits onto contrasting middle Ediacaran palaeogeographic reconstructions, we show how these deposits can be used to constrain hypotheses of Ediacaran continental configuration.

Geological evidence points to icehouse conditions during the Ediacaran Period (635 to 538.8 Ma) both before and during the emergence of animals in the fossil record. However, the temporal and spatial distributions of Ediacaran ice sheets are not well constrained due to uncertainties in palaeogeography, chronostratigraphy, and the depositional settings of candidate glaciogenic deposits. Here, we systematically evaluate the evidence for the depositional ages of candidate Ediacaran glaciogenic deposits and establish the likelihood that each deposit was formed by ice-driven processes using observation-driven weighting criteria. Our analysis supports the existence of discrete mid- and late Ediacaran icehouse intervals (MEIH and LEIH respectively), each followed by greenhouse conditions. Focussing on the older MEIH, we integrate our quality-controlled geological dataset with climate and ice sheet model simulations to characterise glacial conditions during this interval (~593 to 579 Ma), which encompasses the ‘Gaskiers glaciation’. Our results indicate that the MEIH was a Phanerozoic-style icehouse, with latitudinally-constrained and fluctuating ice sheets, marking a break from the preceding Cryogenian snowball Earth motif, and occurring before the first known appearance of animals in the fossil record. By mapping robustly identified glaciogenic deposits onto contrasting middle Ediacaran palaeogeographic reconstructions, we show how these deposits can be used to constrain hypotheses of Ediacaran continental configuration.

Chelicerates are a diverse group of terrestrial and aquatic arthropods, yet their origin and early evolution remain debated^1,2,3,4,5,6. Among different hypotheses^7,8,9,10,11, one proposes that the front appendages, known as chelicerae, of chelicerates evolved from the short great appendages (SGAs) of Cambrian megacheirans^{12,13,14,15,16} and that book gills originated from their trunk limbs⁷. Although taxa such as Mollisonia plenovenatrix⁷ and Megachelicerax cousteaui¹⁶ provide important clues to the early evolution of chelicerates, the morphological transition from megacheiran-like appendages to true chelicerae and book gills remains unresolved. Here we use X-ray microtomography to reveal the three-dimensional anatomy of Urokodia aequalis, an early Cambrian euarthropod from the Chengjiang biota of China. Urokodia has a seven-segmented head with a sclerotized hypostome, pincer-like SGAs and biramous trunk appendages with overlapping exite flaps. Its pincer-like SGAs represent a bridge structure between the appearance of multisegmented SGAs and true chelicerae, and its trunk appendages support a megacheiran origin of book gills. Phylogenetic analyses consistently confirm the monophyly of Cheliceromorpha¹⁷, with Urokodia being the earliest-branching upper stem-group chelicerate that links lower stem-group megacheirans to crownward forms such as Mollisonia and Megachelicerax.