The nervous and circulatory systems of a Cretaceous crinoid: preservation, palaeobiology and evolutionary significance

Featherstars, comatulid crinoids that shed their stalk during their ontogeny, are the most species‐rich lineage of modern crinoids and the only ones present in shallow water today. Although they are of considerable palaeontological interest as a ‘success story’ of the Mesozoic Marine Revolution, their fossil record is relatively species‐poor and fragmentary. New Spanish fossils of the Cretaceous featherstar Decameros ricordeanus preserve the shape and configuration of nervous and circulatory anatomy in the form of infilled cavities, which we reconstruct from CT scans. The circulatory system of D. ricordeanus was relatively extensive and complex, implying a pattern of coelomic fluid flow that is unique among crinoids, and the peripheral parts of the nervous system include linkages both to the circulatory system and to the surface of the body. A phylogenetic analysis (the first to include both living and fossil featherstars and which includes characters from internal anatomy) recovers D. ricordeanus among the lineage of featherstars that includes Himerometroidea, Tropiometra and ‘Antedonoidea’, among others. D. ricordeanus is larger than almost any modern featherstar, and its elaborate coelomic morphology appears to be a consequence of positive allometry. All featherstars with coelomic diverticula are shown to belong to a single comatulid subclade, and this feature may constitute a synapomorphy of that group. Some preservation of cavities corresponding to soft tissue is probably not exceptional in fossil crinoids, providing an opportunity to study the diversity and evolution of extinct anatomical systems typically only preserved in Lagerstätten.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154347/1/pala12452.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154347/2/pala12452_am.pd

Large euarthropod carapaces from a high latitude Cambrian (Drumian) deposit in Spain

Deposits preserving non-biomineralized tissues and animals provide an unrivalled opportunity to study the evolution and radiation of early animal life. Numerous sites of Cambrian age are known from North America (Laurentia) and South China (East Gondwana), which provide a high resolution picture of the fauna at low latitudes. By contrast, our knowledge of Cambrian animals from higher latitudes is relatively poor. This patchiness in our knowledge of animal life during the radiation of animals in the Cambrian period limits our ability to understand and detect palaeogeographic trends and does not provide a full appreciation of animal diversity at this time. Here we report a new middle Cambrian (Drumian) site preserving lightly sclerotized euarthropod carapaces, sponges and palaeoscolecids near the village of Mesones de Isuela in the Iberian Chains (Spain). We describe three bivalved euarthropod carapace morphs, two comparable to those described from the only other high latitude Drumian deposit, the Jince Formation (Czechia), and one distinct from previous discoveries. These new findings highlight the importance of high latitude Gondwana Konservat Lagerstatten for understanding the palaeogeographical aspect of the radiation of early animals and suggest that bivalved euarthropods at high latitudes were larger than those at lower latitudes during the Cambrian

Deciphering The Early Evolution of Echinoderms with Cambrian Fossils

Echinoderms are a major group of invertebrate deuterostomes that have been an important component of marine ecosystems throughout the Phanerozoic. Their fossil record extends back to the Cambrian, when several disparate groups appear in different palaeocontinents at about the same time. Many of these early forms exhibit character combinations that differ radically from extant taxa, and thus their anatomy and phylogeny have long been controversial. Deciphering the earliest evolution of echinoderms therefore requires a detailed understanding of the morphology of Cambrian fossils, as well as the selection of an appropriate root and the identification of homologies for use in phylogenetic analysis. Based on the sister‐group relationships and ontogeny of modern species and new fossil discoveries, we now know that the first echinoderms were bilaterally symmetrical, represented in the fossil record by Ctenoimbricata and some early ctenocystoids. The next branch in echinoderm phylogeny is represented by the asymmetrical cinctans and solutes, with an echinoderm‐type ambulacral system originating in the more crownward of these groups (solutes). The first radial echinoderms are the helicoplacoids, which possess a triradial body plan with three ambulacra radiating from a lateral mouth. Helicocystoids represent the first pentaradial echinoderms and have the mouth facing upwards with five radiating recumbent ambulacra. Pentaradial echinoderms diversified rapidly from the beginning of their history, and the most significant differences between groups are recorded in the construction of the oral area and ambulacra, as well as the nature of their feeding appendages. Taken together, this provides a clear narrative of the early evolution of the echinoderm body plan

A shallow-water cyrtocrinid crinoid (Articulata) from the upper Albian of the Western Pyrenees, North Spain

The cyrtocrinid crinoid Proholopus holopiformis (Remeš, 1902) is described from the upper Albian succession that may be included in the Albeniz unit to the east of Iruñea-Pamplona (Navarre, Western Pyrenees, Spain). Although based on partially disarticulated material, this taxon preserve calyx, stem, attachment structure, and brachial plates from the arms. Proholopus holopiformis was previously described from the Upper Jurassic-Lower Cretaceous of the Czech Republic and Lower Cretaceous of France and Crimea, thus the occurrence from Spain represents the youngest of the species. This allows a better characterization of the family Proholopodidae that was originally described based on calyx morphology only and expands its distribution to the upper Albian. Proholopus holopiformis inhabited the fore-reef areas of coral-sponge bioconstructions. Based on coral types, crinoids are thought to have dwelled near the euphotic-oligophotic zones transition and, thus, thrive in shallow depths. Most specimens have bite marks compatible with cidaroid predation. This represents one of the youngest occurrences of cyrtocrinids inhabiting shallow marine environments before their migration to the deep sea due to the ongoing Mesozoic Marine Revolution

Phylogenetic position of Bohemiacinctus gen. nov. (Echinodermata, Cincta) from the Cambrian of Bohemia: implications for macroevolution and the role of taxon sampling in palaeobiological systematics

‘Asturicystis’ havliceki Fatka & Kordule from the middle Cambrian of Bohemia (Czech Republic) is re-described based on its type material. Several features, including the extension of the food grooves and presence of ventral swellings suggest that ‘A.’ havliceki does not belong to Asturicystis, and is placed in the new genus Bohemiacinctus. To ascertain the phylogenetic position of Bohemiacinctus havliceki, we conducted Bayesian fossil tip-dating and parsimony-based phylogenetic analyses of 24 species spanning all major groups of cinctan higher taxa. Results show a high degree of congruence between tree topologies recovered by both tip-dated and parsimony-based analyses. Both methods indicate B. havliceki is phylogenetically distant from Asturicystis and is most likely to be an early representative of the family Sucocystidae. Overall, our phylogeny is broadly similar to previous estimates of cinctan relationships, including a more conventional phylogenetic position of controversial taxa such as Protocinctus. These results point to the sensitivity of small clades such as cinctans to taxon sampling effects, and highlights the importance of taxonomy and accurate morphological character descriptions in phylogenetic analyses of fossil taxa

Palaeoebiological implications of cuticle morphology, microstructure and formation in modern and fossil Daira (Decapoda, Brachyura, Dairoidea)

The origin and function of peculiar mushroom-shaped cuticular structures in some decapod crustaceans remains unknown. This ornamentation has appeared several times in widely disparate clades (in podotreme and heterotreme crabs, and pagurids). These structures are analysed in the modern genus Daira and compared with fossil material from the Eocene of Huesca and the Miocene of Alicante and Mallorca. A morphological and petrographic study is carried out using conventional microscopy and Scanning Electron Microscopy to understand the microstructure in modern and fossil representatives. This provides a clear view of the mushroom-like structures that cover the carapace of Daira and the distribution of the different layers of the exoskeleton. The results reveal a complex morphology, which involves all layers of the cuticle, with changes in the thickness of the exocuticle in different areas, and the presence of conical structures that especially affect the outer layers. These convolutions form a network of channels connected to the outside by pores. Finally, possible anti-predatory functions of these complex structures are proposed

Redox regulation of Salicylic acid biosynthesis by S-nitrosylation

A general outcome of plant-pathogen interactions is the oxidative and nitrosative burst, characterized for the accumulation of reactive oxygen and nitrogen species (ROS and RNA) which coordinate signalling cascades. Among RNS, Nitric oxide (NO) stands as a key signalling molecule in different physiological processes including plant immunity. An established mechanism for the transfer of NO bioactivity is S-nitrosylation (SNO), the reversible binding of a NO molecule to the thiol group of a susceptible cysteine, allowing specific proteins to respond to changes in the cellular REDOX state. The first genetic evidence about the role of NO in plant immunity was noted in Arabidopsis thaliana plants carrying a loss-of-function mutation of the S-nitrosoglutathione (GSNO) reductase 1 (GSNOR1) gene. This mutation resulted in increased total cellular S-nitrosylation and compromised basal, non-host and R-gene mediated immunity, and impaired synthesis and accumulation of the immune activator salicylic acid (SA). SA plays a pivotal role in the regulation of basal and systemic resistance. It is mainly produced by the activity of the enzyme Isochorismate Synthase 1 (ICS1) in response to pathogens. To date, significant progress has been achieved in understanding the mechanisms by which S-nitrosylation regulates SA signalling. However, the molecular mechanisms by which NO regulates SA biosynthesis remains elusive. To investigate if NO mediates transcriptional or posttranscriptional regulation over ICS1 expression we generated the reporter line ICS1::GUS. Our data suggest that ICS1 is subjected to transcriptional repression by S-nitrosylation. In agreement with previous observations about inhibition of the DNA-binding of SARD1 to the ICS1 promoter upon S-nitrosylation of SARD1 at Cysteine 438. We observed a significant reduction in the binding affinity of recombinant wild type (WT) SARD1 but not in SARD1 with a Cystein 438 to Serine mutation. To expand this observations and investigate the biological relevance of S-nitrosylation of Cys438 we generated transgenic lines expressing a C-terminal HA and Nano luciferase SARD1 and SARD1C438S fusion proteins. We showed that SARD1 can be S-nitrosylated in vivo. We did not observe any difference in local immunity against Pseudomonas syringae infection between the WT and C438S lines. Interestingly, the SARD1C438S lines showed impaired activation of systemic acquired resistance (SAR) compared to the WT. In addition, we observed that SARD1 protein level follows a circadian rhythm after SA treatment, which was impaired in the C438S mutant, suggesting that S-nitrosylation of SARD1 is necessary for optimal activation of SAR. It is possible that S-nitrosylation of SARD1 coordinates protein-protein interactions between SARD1 and other SAR activators. We developed a strategy to express and purify recombinant SARD1 for structural studies. Solving the three-dimensional structure of SARD1 can foster our understanding on the molecular interactions behind the regulation of SARD1. Finally, we designed a forward mutant screening to search for second-site mutations that can suppress the gsnor1 phenotype, which we speculate could be related with a novel mechanism for GSNO-turnover or NO metabolism. Collectively, our work can contribute to integrate NO cues in the regulation of SA biosynthesis and suggests a role for S-nitrosylation of SARD1 in systemic immunity

Cambrian cinctan echinoderms shed light on feeding in the ancestral deuterostome

Reconstructing the feeding mode of the latest common ancestor of deuterostomes is key to elucidating the early evolution of feeding in chordates and allied phyla; however, it is debated whether the ancestral deuterostome was a tentaculate feeder or a pharyngeal filter feeder. To address this, we evaluated the hydrodynamics of feeding in a group of fossil stem-group echinoderms (cinctans) using computational fluid dynamics. We simulated water flow past three-dimensional digital models of a Cambrian fossil cinctan in a range of possible life positions, adopting both passive tentacular feeding and active pharyngeal filter feeding. The results demonstrate that an orientation with the mouth facing downstream of the current was optimal for drag and lift reduction. Moreover, they show that there was almost no flow to the mouth and associated marginal groove under simulations of passive feeding, whereas considerable flow towards the animal was observed for active feeding, which would have enhanced the transport of suspended particles to the mouth. This strongly suggests that cinctans were active pharyngeal filter feeders, like modern enteropneust hemichordates and urochordates, indicating that the ancestral deuterostome employed a similar feeding strategy

Filling the early Eocene gap of paguroids (Decapoda, Anomura): a new highly diversified fauna from the Spanish Pyrenees (Serraduy Formation, Graus-Tremp Basin)

A highly diversified fauna of hermit crabs associated with reef environments from the Serraduy Formation (lower Eocene) in the southern Pyrenees (Huesca, Spain) is described. Other European Eocene outcrops have yielded paguroids associated with a single environment; however, the studied association represents one of the highest paguroid diversities in a single Eocene outcrop worldwide. The new material increases the diversity of known fossil paguroids, including eight species from which six are new: Clibanarius isabenaensis n. sp., Parapetrochirus serratus n. sp., Dardanus balaitus n. sp., ?Petrochirus sp., Eocalcinus veteris n. sp., ?Pagurus sp., Paguristes perlatus n. sp., and Anisopagurus primigenius n. sp. We erected a new combination for Paguristes sossanensis De Angeli and Caporiondo, 2009 and Paguristes cecconi De Angeli and Caporiondo, 2017 and transfer them to the genus Clibanarius. This association contains the oldest record of the genera Eocalcinus and Anisopagurus. Our data demonstrate that paguroids were diverse by the early Eocene in coral-reef environments and fill an important gap between the poorly known Paleocene assemblages and the more diverse mid- to late Eocene ones

A highly diverse dromioid crab assemblage (Decapoda, Brachyura) associated with pinnacle reefs in the lower Eocene of Spain

A highly diverse fauna of dromioid brachyurans from the Serraduy Formation (lower Eocene) in the western Pyrenees (Huesca, Spain) is described and illustrated. Recorded taxa are Mclaynotopus longispinosus new genus new species, Torodromia elongata n. gen. n. sp., Basidromilites glaessneri n. gen. n. sp., ?Basidromilites sp., Sierradromia gladiator n. gen. n. sp., Kromtitis isabenensis n. sp., and ?Basinotopus sp. Other European outcrops have yielded dromioids in association with specific environments, likely coral and sponge reef and siliciclastic soft bottoms; but the present material constitutes the most diverse dromioid assemblage from the lower Eocene worldwide. These dromioids co-occurred with a rich invertebrate fauna and lived near coral–algal reef mounds. Sedimentological data suggest that most of the fauna accumulated in fore reef settings as a result of storm activity. The present material greatly increases the diversity of known dromioid crabs associated with Eocene reef environments.UUID: http://zoobank.org/aed8cafa-7c64-4e70-bd45-9f357fc37a2