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Career of a globe trotting phycologist.
Get PDFThe attached file is the published version of the article.NHM Repositor
Mouthpart morphology and feeding structures in the palaeocharinid trigonotarbids of the Rhynie chert: insights from comparisons to modern arachnids
Get PDFAbstract: Trigonotarbida, an extinct order of spider‐like arachnids, were significant predators between the late Silurian and early Permian. Characterized by their segmented opisthosoma, clasp‐knife chelicera, and paired book lungs, they played a pivotal role in the formation of Early Devonian terrestrial ecosystems. However, the compression‐fossil or mould preservation of most trigonotarbids has been a limiting factor in understanding their fine morphology. Here, we re‐examine the mouthparts of Palaeocharinus, a trigonotarbid genus from the c. 408 Ma Rhynie chert of Scotland. Rhynie preserves the palaeocharinid trigonotarbids in three dimensions with extraordinary fidelity, offering detailed insights into their anatomy, feeding and hunting behaviours, and phylogenetic position. Here we present the first confocal laser scanning microscopy (CLSM) data for Palaeocharinus using three‐dimensional modelling to reconstruct the morphology of a tiered filtration apparatus, comprising a coarse outer mesh of interlacing plumose setae and a fine inner filter of pinnate setae. Together with the clasp‐knife action of the chelicera and mastication by the cheliceral teeth, Palaeocharinus emerges as a sophisticated terrestrial predator with a feeding mechanism resembling that of extant representatives of Pedipalpi (Amblypygi + Uropygi + Schizomida). Phylogenetic analyses with new and modified mouthpart characters affirm the placement of Trigonotarbida within Pantetrapulmonata (Aranaeae + Pedipalpi). This study provides insights into the evolutionary innovations that facilitated the diversification and proliferation of trigonotarbids in early terrestrial landscapes.Copyright© 2024 The Author(s). Palaeontology published by John Wiley & Sons Ltd on behalf of The Palaeontological Association.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. The attached file is the published version of the article.NHM Repositor
The aqueous alteration of CM chondrites, a review
Get PDFThe CM chondrites are samples of primitive water-rich asteroids formed during the early solar system. They record significant interaction between liquid water and silicate rock, resulting in a mineralogy dominated by hydrated secondary phases. Their similarity to the near-Earth asteroids Bennu and Ryugu – targets of current sample return space missions – makes the analysis of CM chondrites essential to the interpretation of these enigmatic bodies. Here, we review the aqueous alteration history of the CM chondrite group.
Initially, amorphous silicate, metal and sulphides within the matrix were converted into Fe-cronstedtite and tochilinite. Later, the serpentinization of refractory coarse-grained inclusions led to the addition of Mg to the fluid phase. This is reflected in the cation composition of secondary phases which evolved from Fe-rich to Mg-rich. Although most CM meteorites are classified as CM2 chondrites and retain some unaltered anhydrous silicates, a few completely altered CM1s exist (∼4.2% [Meteoritical Bulletin, 2021]).
The extent of aqueous alteration can be quantified through various techniques, all of which trace the progression of secondary mineralization. Early attempts employed petrographic criteria to assign subtypes – most notably the Browning and Rubin scales have been widely adopted. Alternatively, bulk techniques evaluate alteration either by measuring the ratio of phyllosilicate to anhydrous silicate (this can be with X-ray diffraction [XRD] or infrared spectroscopy [IR]) or by measuring the combined H abundance/δD compositions. The degree of aqueous alteration appears to correlate with petrofabric strength (most likely arising due to shock deformation). This indicates that aqueous alteration may have been driven primarily by impact rather than by radiogenic heating. Alteration extent and bulk O-isotope compositions show a complex relationship. Among CM2 chondrites higher initial water contents correspond to more advanced alteration. However, the CM1s have lighter-than-expected bulk compositions. Although further analyses are needed these findings could suggest either differences in alteration conditions or initial isotopic compositions – the latter scenario implies that the CM1 chondrites formed on a separate asteroid from the CM2 chondrites.
Secondary phases (primarily calcite) act as proxies for the conditions of aqueous alteration and demonstrate that alteration was prograde, with an early period at low temperatures (<70 °C), while later alteration operated at higher temperatures of 100–250 °C. Estimates for the initial water-to-rock ratios (W/R) vary between 0.2–0.7. They are based either on isotopic mass balance or mineral stoichiometry calculations – variability reflects uncertainties in the primordial water and protolith compositions and whether alteration was open or closed system.
Some CM chondrites (<36%) experienced a later episode of post-hydration thermal metamorphism, enduring peak temperatures <900 °C and resulting in a dehydrated mineralogy and depleted volatile element abundances. Heating was likely short-duration and caused by impact events. The presence of CM chondrite material embedded in other meteorites, their prominence among the micrometeorite flux and the link between CMs and rubble-pile C-type near-Earth asteroids (e.g. Bennu and Ryugu) implies that the CM parent body was disrupted, leaving second-generation CM asteroids to supply material to Earth.Copyright © 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). The attached file is the published version of the article.NHM Repositor
Signatures of the post-hydration heating of highly aqueously altered CM carbonaceous chondrites and implications for interpreting asteroid sample returns
Get PDFThe CM carbonaceous chondrites have all been aqueously altered, and some of them were subsequently heated in a parent body environment. Here we have sought to understand the impact of short duration heating on a highly aqueously altered CM through laboratory experiments on Allan Hills (ALH) 83100. Unheated ALH 83100 contains 83 volume per cent serpentine within the fine-grained matrix and altered chondrules. The matrix also hosts grains of calcite and dolomite, which are often intergrown with tochilinite, Fe(Ni) sulphides (pyrrhotite, pentlandite), magnetite and organic matter. Some of the magnetite formed by replacement of Fe(Ni) sulphides that were accreted from the nebula. Laboratory heating to 400 C has caused partial dehydroxylation of serpentine and loss of isotopically light oxygen leading to an increase in bulk d18O and fall in D17O. Tochilinite has decomposed to magnetite, whereas carbonates have remained unaltered. With regards to infrared spectroscopy (4000–400 cm 1; 2.5–25 mm), heating to 400 C has resulted in decreased emissivity (increased reflectance), a sharper and more symmetric OH band at 3684 cm 1 (2.71 mm), a broadening of the SiAO stretching band together with movement of its minimum to longer wavenumbers, and a decreasing depth of the MgAOH band (625 cm 1;16mm). The SiAO bending band is unmodified by mild heating. With heating to 800 C the serpentine has fully dehydroxylated and recrystallized to Fo60/70 olivine. Bulk d18O has further increased and D17O decreased. Troilite and pyrrhotite have formed, and recrystallization of pentlandite has produced Fe,Ni metal. Calcite and dolomite were calcined at 700 C and in their place is an un-named Ca-Fe oxysulphide. Heating changes the structural order of organic matter so that Raman spectroscopy of carbon in the 800 C sample shows an increased (D1 + D4) proportional area parameter. The infrared spectrum of the 800 C sample confirms the abundance of Fe-bearing olivine and is very similar to the spectrum of naturally heated stage IV CM Pecora Escarpment 02010. The temperature-related mineralogical, chemical, isotopic and spectroscopic signatures defined in ALH 83100 will help to track the post-hydration thermal histories of carbonaceous chondrite meteorites, and samples returned from the primitive asteroids Ryugu and Bennu.Copyright © 2020 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/ licenses/by/4.0/). The attached file is the published version of the article.NHM Repositor
First record of Calyptotheca alexandriensis (Cheilostomatida, Lanceoporidae) from Ras Juddi (Pasni) Makran coast, Northern Arabian Sea
Get PDFThe available information regarding bryozoans in coastal areas of Pakistan is limited. This research paper presents the first record of Calyptotheca alexandriensis from Ras Juddi (Pasni) along the Makran coast, and the second record globally of this species. This species was first reported in the Eastern Harbor of Alexandria, Egypt, as a distinctive deep orange erect foliaceous bryozoan and was observed abundantly on various hard substrates, such as rocks, ropes, metal pipes supporting marina piers, and ship hulls. The discovery adds a new record of the family, Lanceoporidae, and genus, Calyptotheca, to the bryozoan fauna of Pakistan, expanding its known distribution to the Northern Arabian Sea. The present specimens were collected during December 2021–October 2022 and subjected to detailed taxonomic analysis using light microscopy and scanning electron microscopy (SEM). This study contributes to the understanding of bryozoan biodiversity in the region and highlights the potential for further discoveries along the unexplored coastal areas of Pakistan.This article is issued under a Creative Commons CC-BY licence. The attached file is the published version of the article.NHM Repositor
Genus-level revision of the Alycaeidae (Gastropoda, Cyclophoroidea), with an annotated species catalogue
Get PDF412 species-group names (including 11 replacement names), and 14 genus-group names of the Alycaeidae have been introduced to date. Type materials of 85% (336) of the known species and subspecies were examined, a further 5% (19) of the taxa were studied using available non-type material, and for another 6% (22) the original descriptions were sufficiently detailed to evaluate their taxonomic status. Only 3% of the taxa (12) could not be examined. Special attention was paid to the sculpture of the embryonic whorls and the sutural tube-microtunnel system in order to provide a novel classification for this group.
In this study 363 taxa (320 species or 43 subspecies) are accepted within the family Alycaeidae. Of these, 22 have been described by the lead author and his coauthors in previous publications. In addition, there are 18 species that were formerly classified in Cycloryx and now belong to Pincerna due to its synonymy with Cycloryx. Among the remaining 323 species, 209 (65%) are transferred here to another genus, whilst 114 (35%) have remained in their original genus.
Seven genera are accepted. While some questions (e.g., the distinction between Pincerna and Alycaeus) remained unanswered, this revision made three main achievements: (1) The Dicharax species were identified based on the absence of spiral striation on the entire shell; (2) the Metalycaeus species were identified based on the spiral striation of the protoconch; (3) and Stomacosmethis was separated from Alycaeus based on the extremely short sutural tube.
Five nominal species are being synonymised with other species, and eight species are now treated as subspecies. The following replacement names are proposed: Dioryx urnula niosiensis Páll-Gergely, nom. nov. for Alycaeus urnula var. daflaensis Godwin-Austen, 1914; Dioryx urnula rotundus Páll-Gergely, nom. nov. for Alycaeus urnula var. globosus Godwin-Austen, 1914; Pincerna crenilabris juttingae Páll-Gergely, nom. nov. for Alycaeus crenilabris laevis van Benthem Jutting, 1959; Pincerna crenilabris korintjiensis Páll-Gergely, nom. nov. for Alycaeus crenilabris latecostatus van Benthem Jutting, 1959; Dicharax conicus jatingaensis Páll-Gergely, nom. nov. for Alycaeus conicus var. nanus Godwin-Austen, 1914; Metalycaeus godwinausteni Páll-Gergely, nom. nov. for Alycaeus neglectus Godwin-Austen, 1914; and finally Metalycaeus suhajdai Páll-Gergely, nom. nov. for Alycaeus varius Godwin-Austen, 1914.Copyright Barna Páll-Gergely et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published version of the article.NHM Repositor
The genome sequence of the club-tailed millipede, Cylindroiulus punctatus (Leach, 1816)
Get PDFWe present a genome assembly from a female specimen of Cylindroiulus punctatus (club-tailed millipede; Arthropoda; Diplopoda; Julida; Julidae). The genome sequence has a total length of 354.09 megabases. Most of the assembly (92.9%) is scaffolded into 7 chromosomal pseudomolecules. The mitochondrial genome has also been assembled, with a length of 18.98 kilobases.Copyright: © 2025 Edgecombe GD et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The attached file is the published version of the article.NHM Repositor
The morphological, chromosomal and molecular illumination of the dramatic diversity of the stripe-backed shrews, Sorex cylindricauda species complex (Eulipotyphla: Soricidae)
Get PDFAbstract: The taxonomy of the stripe-backed shrew complex (Sorex cylindricauda species group), distributed in mountains of western China, appears challenging due to remarkable variation in morphological traits and relatively recent times of diversification. According to classical points of view only two or three species of the stripe-backed shrews can be distinguished. However, previous molecular reconstructions revealed at least 14 genetic lineages including a number of undescribed cryptic species. In the current study we revise the taxonomic status of large-sized stripe-backed shrews occurring in high mountain areas in south Gansu, north-western Sichuan and western Qinghai that were previously treated as S. aff. cylindricauda or S. sinalis. The available molecular data place them in a separate species-level lineage of the stripe-backed shrew complex. Our morphological analysis indicate that shrews of this lineage are distinct from the two other large-sized Chinese species, S. cylindricauda and S. sinalis, based on both cranial and external traits. Therefore, we here describe it as a species new to science, the karyotype of which is characterized by 2n = 26 with an additional B chromosome and NFa = 44. Our molecular phylogenetic analysis demonstrates multiple instances of mitonuclear discordance among lineages within the S. cylindricauda complex, which is likely a result of mtDNA introgression, thus highlighting the important role of reticulation events in the evolution of the group.Copyright Anna A. Bannikova et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published version of the article.NHM Repositor
Binocular vision and foraging in ducks, geese and swans (Anatidae)
Get PDFWide variation in visual field configuration across avian species is hypothesized to be driven primarily by foraging ecology and predator detection. While some studies of selected taxa have identified relationships between foraging ecology and binocular field characteristics in particular species, few have accounted for the relevance of shared ancestry. We conducted a large-scale, comparative analysis across 39 Anatidae species to investigate the relationship between the foraging ecology traits of diet or behaviour and binocular field parameters, while controlling for phylogeny. We used phylogenetic models to examine correlations between traits and binocular field characteristics, using unidimensional and morphometric approaches. We found that foraging behaviour influenced three parameters of binocular field size: maximum binocular field width, vertical binocular field extent, and angular separation between the eye-bill projection and the direction of maximum binocular field width. Foraging behaviour and body mass each influenced two descriptors of binocular field shape. Phylogenetic relatedness had minimal influence on binocular field size and shape, apart from vertical binocular field extent. Binocular field differences are associated with specific foraging behaviours, as related to the perceptual challenges of obtaining different food items from aquatic and terrestrial environments.Copyright © 2023 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution
License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original
author and source are credited. The attached file is the published version of the article.NHM Repositor
Experts’ opinions on threats to Leach’s Storm-Petrels ( Hydrobates leucorhous ) across their global range
Get PDFSeabirds are declining globally, though the threats they face differ among and within species and populations. Following substantial population declines at several breeding colonies, Leach’s Storm-Petrel (Hydrobates leucorhous) was uplisted from Least Concern to Vulnerable by the International Union for Conservation of Nature (IUCN) in 2016. Reasons for these declines are unclear, and it is important to identify threats the species faces across its global breeding range to guide research directions and inform conservation efforts. We solicited feedback from 37 Leach’s Storm-Petrel scientific experts from eight countries on the importance of different threats facing the species on land and at sea. Perceived threats to extant colonies varied spatially, with a consensus within regions for main threats. Most researchers agreed that the main threats at or near colonies are avian and mammalian predators and onshore light attraction. At-sea threats have been less studied and were harder to identify and rank, but include offshore lights and structures, spatial shifts in prey, and contaminants. Climate change was not listed specifically because of its multifaceted repercussions, but several perceived threats are linked to climate change. Globally, introduction of mammalian predators is an overarching driver of seabird colony decline or extirpation; thus biosecurity must be considered an important measure for the conservation of storm-petrels. In addition, filling knowledge gaps and implementing a series of regionally relevant and targeted strategies that lead to small but cumulative conservation successes may be the best approach for this species.Copyright © by the author(s). Published here under license by The Resilience Alliance. This article is under a Creative Commons Attribution 4.0 International License. You may share and adapt the work provided the original author and source are credited, you indicate whether any changes were made, and you include a link to the license. ACE-ECO-2022-2370.pdf. The attached file is the published version of the article.NHM Repositor