Trilobite evolutionary rates constrain the duration of the Cambrian explosion

Published on Mar 5, 2019in Proceedings of the National Academy of Sciences of the United States of America9.58
· DOI :10.1073/pnas.1819366116
John R. Paterson23
Estimated H-index: 23
(UNE: University of New England (United States)),
Gregory D. Edgecombe43
Estimated H-index: 43
(Natural History Museum),
Michael S. Y. Lee (Flinders University)
Trilobites are often considered exemplary for understanding the Cambrian explosion of animal life, due to their unsurpassed diversity and abundance. These biomineralized arthropods appear abruptly in the fossil record with an established diversity, phylogenetic disparity, and provincialism at the beginning of Cambrian Series 2 (∼521 Ma), suggesting a protracted but cryptic earlier history that possibly extends into the Precambrian. However, recent analyses indicate elevated rates of phenotypic and genomic evolution for arthropods during the early Cambrian, thereby shortening the phylogenetic fuse. Furthermore, comparatively little research has been devoted to understanding the duration of the Cambrian explosion, after which normal Phanerozoic evolutionary rates were established. We test these hypotheses by applying Bayesian tip-dating methods to a comprehensive dataset of Cambrian trilobites. We show that trilobites have a Cambrian origin, as supported by the trace fossil record and molecular clocks. Surprisingly, they exhibit constant evolutionary rates across the entire Cambrian, for all aspects of the preserved phenotype: discrete, meristic, and continuous morphological traits. Our data therefore provide robust, quantitative evidence that by the time the typical Cambrian fossil record begins (∼521 Ma), the Cambrian explosion had already largely concluded. This suggests that a modern-style marine biosphere had rapidly emerged during the latest Ediacaran and earliest Cambrian (∼20 million years), followed by broad-scale evolutionary stasis throughout the remainder of the Cambrian.
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  • References (33)
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Published on 2018in Evolution3.57
Graham E. Budd32
Estimated H-index: 32
(Uppsala University),
Richard P. Mann17
Estimated H-index: 17
(University of Leeds)
Survivorship biases can generate remarkable apparent rate heterogeneities through time in otherwise homogeneous birth‐death models of phylogenies. They are a potential explanation for many striking patterns seen in the fossil record and molecular phylogenies. One such bias is the “push of the past”: clades that survived a substantial length of time are likely to have experienced a high rate of early diversification. This creates the illusion of a secular rate slow‐down through time that is, rath...
Published on Jul 1, 2018in Journal of the Geological Society3.30
Chuan Yang5
Estimated H-index: 5
(CAS: Chinese Academy of Sciences),
Estimated H-index: 78
(CAS: Chinese Academy of Sciences)
+ 2 AuthorsJunyuan Chen (CAS: Chinese Academy of Sciences)
The Cambrian Chengjiang biota of South China provides compelling fossil evidence for the rapid appearance of metazoan phyla in Earth history (the ‘Cambrian explosion’). However, the timing of the Chengjiang biota is poorly constrained owing to lack of datable rock materials within the Maotianshan Shale that yields the fossils. Here we integrate secondary ion mass spectrometry (SIMS) and chemical ablation isotope dilution thermal ionization mass spectrometry (CA-ID-TIMS) U–Pb analyses of detrital...
Allison C. Daley14
Estimated H-index: 14
(University of Oxford),
Jonathan B. Antcliffe15
Estimated H-index: 15
(University of Oxford)
+ 1 AuthorsStephen Pates4
Estimated H-index: 4
(University of Oxford)
Euarthropoda is one of the best-preserved fossil animal groups and has been the most diverse animal phylum for over 500 million years. Fossil Konservat-Lagerstatten, such as Burgess Shale-type deposits (BSTs), show the evolution of the euarthropod stem lineage during the Cambrian from 518 million years ago (Ma). The stem lineage includes nonbiomineralized groups, such as Radiodonta (e.g., Anomalocaris ) that provide insight into the step-by-step construction of euarthropod morphology, including ...
Published on May 1, 2018in Biological Reviews10.29
Russell D. C. Bicknell5
Estimated H-index: 5
(UNE: University of New England (Australia)),
John R. Paterson23
Estimated H-index: 23
(UNE: University of New England (Australia))
The Cambrian Explosion is arguably the most extreme example of a biological radiation preserved in the fossil record, and studies of Cambrian Lagerstatten have facilitated the exploration of many facets of this key evolutionary event. As predation was a major ecological driver behind the Explosion – particularly the radiation of biomineralising metazoans – the evidence for shell crushing (durophagy), drilling and puncturing predation in the Cambrian (and possibly the Ediacaran) is considered. Ex...
Published on Jan 1, 2018in Virus Evolution
Marc A. Suchard61
Estimated H-index: 61
(UCLA: University of California, Los Angeles),
Philippe Lemey51
Estimated H-index: 51
(Katholieke Universiteit Leuven)
+ 3 AuthorsAndrew Rambaut5
Estimated H-index: 5
(Edin.: University of Edinburgh)
Published on Jan 1, 2018in Systematic Biology10.27
Joëlle Barido-Sottani3
Estimated H-index: 3
(Swiss Institute of Bioinformatics),
Veronika Boskova6
Estimated H-index: 6
(Swiss Institute of Bioinformatics)
+ 12 AuthorsChi Zhang8
Estimated H-index: 8
(Swiss Institute of Bioinformatics)
Published on Sep 1, 2017in Earth-Science Reviews9.53
Xingliang Zhang2
Estimated H-index: 2
(Northwest University (United States)),
Per Ahlberg24
Estimated H-index: 24
(Lund University)
+ 10 AuthorsT. V. Pegel4
Estimated H-index: 4
Formal subdivision of the Cambrian System into four series and ten stages is in progress. The base of Cambrian Stage 3 (provisional), which is conterminous with the base of Cambrian Series 2 (provisional), is expected to be placed at a horizon close to the first appearance of trilobites, which marks the onset of the largest phase of the Cambrian explosion. Conceptually, an ideal boundary position would be marked by a significant and globally recognizable bioevent that divides the lower part of t...
Published on Jan 1, 2017in BioEssays4.40
Françoise S. Howe7
Estimated H-index: 7
(University of Oxford),
Harry Fischl5
Estimated H-index: 5
(University of Oxford)
+ 1 AuthorsJane Mellor37
Estimated H-index: 37
(University of Oxford)
Tri-methylation of lysine 4 on histone H3 (H3K4me3) is a near-universal chromatin modification at the transcription start site of active genes in eukaryotes from yeast to man and its levels reflect the amount of transcription. Because of this association, H3K4me3 is often described as an ‘activating’ histone modification and assumed to have an instructive role in the transcription of genes, but the field is lacking a conserved mechanism to support this view. The overwhelming finding from genome-...
Published on Jan 1, 2017in BioEssays4.40
John A. Cunningham13
Estimated H-index: 13
Alexander G. Liu19
Estimated H-index: 19
(UoB: University of Bristol)
+ 1 AuthorsPhilip C. J. Donoghue52
Estimated H-index: 52
(UoB: University of Bristol)
The evolutionary emergence of animals is one of the most significant episodes in the history of life, but its timing remains poorly constrained. Molecular clocks estimate that animals originated and began diversifying over 100 million years before the first definitive metazoan fossil evidence in the Cambrian. However, closer inspection reveals that clock estimates and the fossil record are less divergent than is often claimed. Modern clock analyses do not predict the presence of the crown-repres...
Published on Aug 24, 2016in Systematic Biology10.27
Alexandra Gavryushkina4
Estimated H-index: 4
(University of Auckland),
Tracy A. Heath4
Estimated H-index: 4
(Iowa State University)
+ 3 AuthorsAlexei J. Drummond57
Estimated H-index: 57
(University of Auckland)
The total evidence approach to divergence-time dating uses molecular and morphological data of extant and fossil species to infer phylogenetic relationships, species divergence times, and macroevolutionary parameters in a single coherent framework. Current model-based implementations of this approach lack an appropriate model for the tree describing the diversification and fossilisation process which can result in erroneous conclusions. We address this shortcoming by providing a total evidence m...
Cited By3
Published on Sep 11, 2019in Evolution & Development1.82
David Jablonski59
Estimated H-index: 59
(U of C: University of Chicago)
Published on Sep 1, 2019in Nature43.07
Cédric Aria (CAS: Chinese Academy of Sciences), Jean-Bernard Caron23
Estimated H-index: 23
(U of T: University of Toronto)
The chelicerates are a ubiquitous and speciose group of animals that has a considerable ecological effect on modern terrestrial ecosystems—notably as predators of insects and also, for instance, as decomposers1. The fossil record shows that chelicerates diversified early in the marine ecosystems of the Palaeozoic era, by at least the Ordovician period2. However, the timing of chelicerate origins and the type of body plan that characterized the earliest members of this group have remained controv...
Published on Aug 28, 2019
Björn Kröger7
Estimated H-index: 7
(AMNH: American Museum of Natural History),
Franziska Franeck1
Estimated H-index: 1
(AMNH: American Museum of Natural History),
Christian M. Ø. Rasmussen14
Estimated H-index: 14
(UCPH: University of Copenhagen)
The early Palaeozoic Era records the initial biodiversification of the Phanerozoic. The increase in biodiversity involved drastic changes in taxon longevity, and in rates of origination and extinct...
Published on Jul 10, 2019
Deng Wang (Northwest University (United States)), Jean Vannier30
Estimated H-index: 30
(UCBL: Claude Bernard University Lyon 1)
+ 6 AuthorsJian Han27
Estimated H-index: 27
(Northwest University (United States))
With millions of extant species, ecdysozoans (Scalidophora, Nematoida and Panarthropoda) constitute a major portion of present-day biodiversity. All ecdysozoans secrete an exoskeletal cuticle which must be moulted periodically and replaced by a larger one. Although moulting (ecdysis) has been recognized in early Palaeozoic panarthropods such as trilobites and basal groups such as anomalocaridids and lobopodians, the fossil record lacks clear evidence of ecdysis in early scalidophorans, largely b...
Published on Jun 12, 2019in Journal of Systematic Palaeontology2.31
James D. Holmes3
Estimated H-index: 3
(University of Adelaide),
John R. Paterson23
Estimated H-index: 23
(UNE: University of New England (Australia)),
Diego C. García-Bellido16
Estimated H-index: 16
(South Australian Museum)
The trilobite Redlichia Cossmann, 1902 is an abundant element of the lower Cambrian (Series 2, Stage 4) Emu Bay Shale (EBS) Konservat-Lagerstatte on Kangaroo Island, South Australia. Well-preserved, fully articulated specimens from this deposit are known to reach lengths of up to 25 cm, representing one of the largest known Cambrian trilobites. Until now, all Redlichia specimens from the EBS have been referred to Redlichia takooensis Lu, 1950, a species originally described from South China. Pre...
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