Ecology of clypeasteroids

Nebelsick, James H.

doi:10.1016/b978-0-12-819570-3.00018-4

Cited by 12 publications

(11 citation statements)

References 137 publications

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“…Within the diversity of irregulars, sand dollars are the most easily recognized (figure 1). The clade includes greatly flattened forms that live in high-energy sandy environments where they feed using a unique mechanism for selecting and transporting organic particles to the mouth, where these are crushed using well-developed jaws [25,26]. Sand dollars (Scutelloida) were long thought to be most closely related to sea biscuits (Clypeasteroida) given a wealth of shared morphological characters [19,25].…”

Section: Introductionmentioning

confidence: 99%

“…Although current molecular topologies already imply ghost ranges for scutelloids and clypeasteroids that necessarily extend beyond the Cretaceous-Paleogene (K-Pg) boundary, the phylogenetic position of apatopygids could impose even earlier ages on these lineages (figure 1). Constraining these divergences is necessary to understand the timing of origin of the sand dollars, one of the most specialized lineages of echinoids [24][25][26][27]. Resolving some phylogenetic relationships within scutelloids has also been complicated by their recurrent miniaturization and associated loss of morphological features (figure 1; [25,31,32]).…”

Section: Introductionmentioning

confidence: 99%

“…1). Constraining these divergences is necessary to understand the timing of origin of the sand dollars, one of the most specialized lineages of echinoids [24][25][26][27]. Resolving some phylogenetic relationships within scutelloids has also been complicated by their recurrent miniaturization and associated loss of morphological features (Fig.…”

Section: Introductionmentioning

confidence: 99%

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Phylogenomic analyses of echinoid diversification prompt a re-evaluation of their fossil record

Koch

Thompson

Hatch

et al. 2021

Preprint

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Echinoids are key components of modern marine ecosystems. Despite a remarkable fossil record, the emergence of their crown group is documented by few specimens of unclear affinities, rendering their early history uncertain. The origin of sand dollars, one of its most distinctive clades, is also unclear due to an unstable phylogenetic context. We employ seventeen novel genomes and transcriptomes to build a dataset with a near-complete sampling of major lineages and use it to revise the phylogeny and divergence times of echinoids. We introduce the concept of a chronospace - a multidimensional representation of node ages - and use it to explore the effects of using alternative gene samples, models of molecular evolution, and clock priors. We find the choice of clock model to have the strongest impact on divergence times, while gene sampling and the use of site-heterogeneous models show little effects. Crown group echinoids originated in the Permian and diversified rapidly in the Triassic. We clarify the relationships among sand dollars and their close relatives, showing that Apatopygus represents a relict lineage with a deep Jurassic origin. Sand dollars are confidently dated to the Cretaceous, implying ghost ranges spanning approximately 50 million years, a remarkable discrepancy with their fossil record.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Phylogenomic analyses of echinoid diversification prompt a re-evaluation of their fossil record

Koch

Thompson

Hatch

et al. 2021

Preprint

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“…Among irregular echinoids, clypeasteroids have the most extensive stereomic interlocking across plate boundaries and also possess internal supports, represented by different structural solutions, such as pillars in Clypeaster and buttresses in Echinocyamus, which conjoin the oral and aboral sides, leading to a high preservation of tests even in high energy settings (Kier 1977;Seilacher, 1979;Nebelsick and Kroh, 2002;Mitchell et al, 2006;Belaústegui et al, 2012;Nebelsick, 2013, 2017;Grun et al, 2018a,b;Nebelsick, 2020).…”

Section: Introduction Skeletal Architecture Ecology and Preservationmentioning

confidence: 99%

Tracking biases in the regular echinoid fossil record: The case of Paracentrotus lividus in recent and fossil shallow-water, high-energy environments

Mancosu

Nebelsick

2020

Palaeontol Electron

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The poor fossil record of regular echinoids is commonly attributed to the fact that they preferentially live as epibenthic grazers on hard rocky substrates in nearshore environments with high energy conditions, where the preservation potential of their tests is generally low. In addition, they commonly occur in the fossil record as fragmented material that hampers identification to low taxonomic level. Herein, a comparative analysis of fossil and recent remains of the regular sea urchin Paracentrotus lividus has been conducted, in order to evaluate the source of taphonomic and taxonomic biases affecting regular echinoid remains. Echinoid remnants are recognized in great abundance both in the Upper Pleistocene marine deposit of Is Mesas and recent littoral environments of Sa Mesa Longa, both in Sardinia (Italy). They were rigorously categorized and analysed with respect to relative abundance, biostratinomic signatures and constructional detail of the skeleton using scanning electron microscopy. Paracentrotus remnants mainly consist of test fragments, isolated plates and fragmented spines. Plates of the apical system and elements of the jaw apparatus were also found. Echinoid remnants in the Pleistocene deposit reflect those in recent environment, with respect to relative abundance and biostratinomic features, and are useful tools for paleoenvironmental and paleoecological reconstruction, even in shallow-water, highenergy environments. The abundance of large test fragments of Paracentrotus lividus both in the Pleistocene record and recent environments is due to a relatively robust test and stereomic interlocking. Difference in relative abundance of echinoid remains and their distribution in sediment fractions (> 2 mm and 1-2 mm) are due to different sampling methods, but also indicate the different preservation potential among various test elements. Herein, the identification of echinoid remains at a low taxonomic level can be assessed even at a very-coarse sand-size fraction (1-2 mm). This study demonstrates that regular echinoid fragments can be identified to a low taxonomic level when very MANCOSU & NEBELSICK: TAPHONOMY REGULAR ECHINOIDS 2 specific characters are preserved, and their analysis may help to minimize the taxonomic bias affecting the regular echinoid fossil record.

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“…2018), which ultimately gave rise to body plans as distinct as those of sand dollars and heart urchins. Irregulars also display a wide range of feeding strategies including bulk and selective deposit feeding, suspension feeding, microphagy, and selective predation (Schultz 2017; Nebelsick 2020; Ziegler et al. 2020 and references therein).…”

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confidence: 99%

Exploring adaptive landscapes across deep time: A case study using echinoid body size

Koch

2021

Evolution

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Adaptive landscapes are a common way of conceptualizing the phenotypic evolution of lineages across deep time. Although multiple approaches exist to implement this concept into operational models of trait evolution, inferring adaptive landscapes from comparative datasets remains challenging. Here, I explore the macroevolutionary dynamics of echinoid body size using data from over 5000 specimens and a phylogenetic framework incorporating a dense fossil sampling and spanning approximately 270 million years. Furthermore, I implement a novel approach of exploring alternative parameterizations of adaptive landscapes that succeeds in finding simpler, yet better‐fitting models. Echinoid body size has been constrained to evolve within a single adaptive optimum for much of the clade's history. However, most of the morphological disparity of echinoids was generated by multiple regime shifts that drove the repeated evolution of miniaturized and gigantic forms. Events of body size innovation occurred predominantly in the Late Cretaceous and were followed by a drastic slowdown following the Cretaceous‐Paleogene mass extinction. The discovery of these patterns is contingent upon directly sampling fossil taxa. The macroevolution of echinoid body size is therefore characterized by a late increase in disparity (likely linked to an expansion of ecospace), generated by active processes driving lineages toward extreme morphologies.

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Ecology of clypeasteroids

Cited by 12 publications

References 137 publications

Phylogenomic analyses of echinoid diversification prompt a re-evaluation of their fossil record

Phylogenomic analyses of echinoid diversification prompt a re-evaluation of their fossil record

Tracking biases in the regular echinoid fossil record: The case of Paracentrotus lividus in recent and fossil shallow-water, high-energy environments

Exploring adaptive landscapes across deep time: A case study using echinoid body size

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