Long-term clade-wide shifts in trilobite segment number and allocation during the Palaeozoic

Hopkins, Melanie J.; To, Rebecca

doi:10.1098/rspb.2022.1765

Cited by 3 publications

(2 citation statements)

References 43 publications

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“…In spite of Proetidae being the longest lived, most diverse trilobite family (1,927 species, Adrain, 2011), there is less debate about familial affinity for proetid trilobites than for many other groups (Paterson, 2020;Hopkins and To, 2022). In fact, "a proetid is a proetid is a proetid" has become a mantra among the three of us (MH, PW, KJ), a view which implies that the family had relatively low morphological disparity.…”

Section: Were Permian Trilobites Morphologically "Boring?"mentioning

confidence: 99%

Permian trilobites and the applicability of the “living fossil” concept to extinct clades

2023

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Some taxa occupy our imaginations as “living fossils” because they were known from the fossil record before being discovered alive today. Other taxa are considered “living fossils” because modern relatives bear a strong morphological resemblance to fossil relatives, or because they occupy a contracted geographic range or have less diversity now than in the past, or because they represent phylogenetic diversity that requires conservation. A characterizing feature of living fossils–and thus an implicit assumption of all criteria–is that the “living fossil” of interest is extant. However, the general research questions that “living fossils” inspire–Why do rates of evolution vary across organisms, across traits, and across time? Why do some clades decline in diversity over extended periods?–may be applied to any clade, including completely extinct clades. We propose that there is nothing special about “now” when it comes to pursuing these questions and that it is unnecessarily limiting to restrict research programs to clades for which an extant member meets some conception of the “living fossil” moniker. To this end, we investigate the extent to which Permian trilobites might resemble “living fossils,” albeit from the perspective of 253 million years ago, when the last trilobites were still alive. We do so by comparing the taxonomic diversity, geographic range, and morphological disparity of trilobites living in the Permian to earlier time periods. We find that Permian trilobites meet most definitions of living fossils, although our assessment of morphological change and character retention depend on taxonomic scale.

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Section: Were Permian Trilobites Morphologically "Boring?"mentioning

confidence: 99%

Permian trilobites and the applicability of the “living fossil” concept to extinct clades

2023

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“…Yet, the number of organisms in the deep‐sea ecosystem was very huge [1] . Arthropods have been recognized as the largest phylum in the animal kingdom, usually with exoskeleton and segmented body, including shrimp, crab, spider, centipede, etc [2,3] . In recent years, studies on the secondary metabolites from arthropods have emerged endlessly.…”

Section: Introductionmentioning

confidence: 99%

Chemical Constituents of the Deep‐sea Gammarid Shrimp‐Derived Fungus Penicillium citrinum XIA‐16

Yu,

Li,

Zhang

et al. 2023

Chemistry & Biodiversity

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One new alkaloid, (S)‐2‐acetamido‐4‐(2‐(methylamino)phenyl)‐4‐oxobutanoic acid (1), was isolated from the deep‐sea‐derived Penicillium citrinum XIA‐16, together with 25 known compounds including ten polyketones (2‐11), eight alkaloids (12‐19), six steroids (20‐25), and a fatty acid (26). Their planar and relative structures were determined by an analysis of 1D and 2D nuclear magnetic resonance (NMR) as well as high resolution electrospray ionization mass spectroscopy (HRESIMS) data. The absolute configuration of 1 was determined by comparison of the experimental and calculated electronic circular dichroism (ECD) spectra. Penicitrinol B (6) significantly inhibited RSL3‐induced ferroptosis (EC50 = 2.0 μM) by reducing lipid peroxidation and heme oxygenase 1 (HMOX1) expression. Under the concentration of 10 μM, penicitrinol A (7) was able to inhibit cuproptosis with the cell viabilities of 68.2 % compared to the negative control (copper and elesclomol) with the cell viabilities of 14.8 %.

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Long-term clade-wide shifts in trilobite segment number and allocation during the Palaeozoic

Hopkins

2022

Proc. R. Soc. B.

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Arthropods are characterized by having an exoskeleton, paired jointed appendages and segmented body. The number and shape of those segments vary dramatically and unravelling the evolution of segmentation is fundamental to our understanding of arthropod diversification. Because trilobites added segments to the body post-hatching which were expressed and preserved in biomineralized exoskeletal sclerites, their fossil record provides an excellent system for understanding the early evolution of segmentation in arthropods. Over the last 200 years, palaeontologists have hypothesized trends in segment number and allocation in the trilobite body, but they have never been rigorously tested. We tabulated the number of segments in the post-cephalic body for over 1500 species, selected to maximize taxonomic, geographical and temporal representation. Analysis reveals long-term shifts in segment number and allocation over the 250-million-year evolutionary history of the clade. For most of the Palaeozoic, the median number of segments in the body did not change. Instead, the total range decreased over time and there was long-term increase in the proportion of segments allocated to the fused terminal sclerite relative to the articulated thoracic region. There was also increased conservation of thoracic segment number within families. Neither taxonomic turnover nor trends in functionally relevant defensive behaviour sufficiently explain these patterns.

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Long-term clade-wide shifts in trilobite segment number and allocation during the Palaeozoic

Cited by 3 publications

References 43 publications

Permian trilobites and the applicability of the “living fossil” concept to extinct clades

Permian trilobites and the applicability of the “living fossil” concept to extinct clades

Chemical Constituents of the Deep‐sea Gammarid Shrimp‐Derived Fungus Penicillium citrinum XIA‐16

Long-term clade-wide shifts in trilobite segment number and allocation during the Palaeozoic

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