Publications by category
Journal articles
Howard RJ, Giacomelli M, Lozano-Fernandez J, Edgecombe GD, Fleming JF, Kristensen RM, Ma X, Olesen J, Sørensen MV, Thomsen PF, et al (2022). The Ediacaran origin of Ecdysozoa: integrating fossil and phylogenomic data.
Journal of the Geological Society,
179(4).
Abstract:
The Ediacaran origin of Ecdysozoa: integrating fossil and phylogenomic data
. Ecdysozoans (Phyla Arthropoda, Kinorhyncha, Loricifera, Nematoda, Nematomorpha, Onychophora, Priapulida, Tardigrada) are invertebrates bearing a tough, periodically moulted cuticle that predisposes them to exceptional preservation. Ecdysozoans dominate the oldest exceptionally preserved bilaterian animal biotas in the early to mid-Cambrian (
. c.
. 520–508â€
Ma), with possible trace fossils in the latest Ediacaran (<556â€
Ma). The fossil record of Ecdysozoa is among the best understood of major animal clades and is believed to document their origins and evolutionary history well. Strikingly, however, molecular clock analyses have implied a considerably deeper Precambrian origin for Ecdysozoa, much older than their earliest fossils. Here, using an improved set of fossil calibrations, we performed Bayesian analyses to estimate an evolutionary time-tree for Ecdysozoa, sampling all eight phyla for the first time. Our results recover Scalidophora as the sister group to Nematoida + Panarthropoda (= Cryptovermes nov.) and suggest that the Ediacaran divergence of Ecdysozoa occurred at least 23â€
myr before the first potential ecdysozoan trace fossils. This finding is impervious to the use of all plausible phylogenies, fossil prior distributions, evolutionary rate models and matrix partitioning strategies. Arthropods exhibit more precision and less incongruence between fossil- and clock-based estimates of clade ages than other ecdysozoan phyla.
.
.
. Supplementary material:
. Full methodologies used and an appendix of fossil calibration points are available at
. https://doi.org/10.6084/m9.figshare.c.5811381
.
.
. Thematic collection:
. This article is part of the Advances in the Cambrian Explosion collection available at:
. https://www.lyellcollection.org/cc/advances-cambrian-explosion
.
Abstract.
Howard RJ, Puttick MN, Edgecombe GD, Lozano-Fernandez J (2020). Arachnid monophyly: Morphological, palaeontological and molecular support for a single terrestrialization within Chelicerata.
ARTHROPOD STRUCTURE & DEVELOPMENT,
59 Author URL.
Howard R, Edgecombe G, David L, Davide P, Lozano-Fernandez J (2019). Exploring the evolution and terrestrialization of scorpions (Arachnida: Scorpiones) with rocks and clocks. Organisms Diversity and Evolution, 19, 71-86.
Publications by year
2022
Howard R (2022). The Deep Evolution of Ecdysozoa.
Abstract:
The Deep Evolution of Ecdysozoa
Ecdysozoa (moulting animals) comprises the protostome Phyla Arthropoda, Kinorhyncha, Loricifera, Nematoda, Nematomorpha, Onychophora, Priapulida and Tardigrada, but our precise understanding of the phylogenetic relationships between these is disputed. Ecdysozoa is an extremely ancient clade that originated in the oceans, and ecdysozoans remain major components of modern marine and terrestrial ecosystems, including the most diverse and abundant of all animal Phyla (Arthropoda and Nematoda respectively). In this thesis, I explore the phylogenetic relationships and divergence times of fossil and extant ecdysozoans in order to address several outstanding issues in the early evolutionary history and palaeobiology of Ecdysozoa, employing data from fossils and molecular sequences.
First, the phylogenetic relationships of the eight ecdysozoan phyla was tested using Bayesian models from a molecular matrix containing newly sequenced taxa from Nematomorpha, Priapulida and Tardigrada. Analyses retrieved a monophyletic Scalidophora (Kinorhyncha, Loricifera and Priapulida) which in turn is sister-group to a clade comprising Nematoida (Nematoda and Nematomorpha) and Panarthropoda (Arthropoda, Onychophora and Tardigrada) – this is named Cryptovermes nov. An improved set of fossil calibrations was compiled and used to infer the divergence times of ecdysozoans under a range of alternative parameters. Crown-group Ecdysozoa diverged in the Ediacaran Period between 636 – 578 Ma, at least 23 million years before the oldest potential fossil evidence of ecdysozoans in the late Ediacaran (
Abstract.
Howard RJ, Giacomelli M, Lozano-Fernandez J, Edgecombe GD, Fleming JF, Kristensen RM, Ma X, Olesen J, Sørensen MV, Thomsen PF, et al (2022). The Ediacaran origin of Ecdysozoa: integrating fossil and phylogenomic data.
Journal of the Geological Society,
179(4).
Abstract:
The Ediacaran origin of Ecdysozoa: integrating fossil and phylogenomic data
. Ecdysozoans (Phyla Arthropoda, Kinorhyncha, Loricifera, Nematoda, Nematomorpha, Onychophora, Priapulida, Tardigrada) are invertebrates bearing a tough, periodically moulted cuticle that predisposes them to exceptional preservation. Ecdysozoans dominate the oldest exceptionally preserved bilaterian animal biotas in the early to mid-Cambrian (
. c.
. 520–508â€
Ma), with possible trace fossils in the latest Ediacaran (<556â€
Ma). The fossil record of Ecdysozoa is among the best understood of major animal clades and is believed to document their origins and evolutionary history well. Strikingly, however, molecular clock analyses have implied a considerably deeper Precambrian origin for Ecdysozoa, much older than their earliest fossils. Here, using an improved set of fossil calibrations, we performed Bayesian analyses to estimate an evolutionary time-tree for Ecdysozoa, sampling all eight phyla for the first time. Our results recover Scalidophora as the sister group to Nematoida + Panarthropoda (= Cryptovermes nov.) and suggest that the Ediacaran divergence of Ecdysozoa occurred at least 23â€
myr before the first potential ecdysozoan trace fossils. This finding is impervious to the use of all plausible phylogenies, fossil prior distributions, evolutionary rate models and matrix partitioning strategies. Arthropods exhibit more precision and less incongruence between fossil- and clock-based estimates of clade ages than other ecdysozoan phyla.
.
.
. Supplementary material:
. Full methodologies used and an appendix of fossil calibration points are available at
. https://doi.org/10.6084/m9.figshare.c.5811381
.
.
. Thematic collection:
. This article is part of the Advances in the Cambrian Explosion collection available at:
. https://www.lyellcollection.org/cc/advances-cambrian-explosion
.
Abstract.
2020
Howard RJ, Puttick MN, Edgecombe GD, Lozano-Fernandez J (2020). Arachnid monophyly: Morphological, palaeontological and molecular support for a single terrestrialization within Chelicerata.
ARTHROPOD STRUCTURE & DEVELOPMENT,
59 Author URL.
2019
Howard R, Edgecombe G, David L, Davide P, Lozano-Fernandez J (2019). Exploring the evolution and terrestrialization of scorpions (Arachnida: Scorpiones) with rocks and clocks. Organisms Diversity and Evolution, 19, 71-86.
