Davey Wright | University of Oklahoma (original) (raw)
Papers by Davey Wright
Background. The superorder Forcipulatacea is a major clade of sea stars with approximately 400 ex... more Background. The superorder Forcipulatacea is a major clade of sea stars with approximately 400 extant species across three orders (Forcipulatida, Brisingida, Zorocallida). Over the past century, the systematics of Forcipulatacea have undergone multiple revisions by various authors, with some considering numerous families such as Asteriidae, Zoroasteridae, Pedicellasteridae, Stichasteridae, Heliasteridae, Labidiasteridae, and Neomorphasteridae, while others recognized only two families (i.e., Asteriidae and Zoroasteridae). Recent molecular analyses have shown the artificial nature of some of these groupings. Notably, four well-supported clades (Zorocallida, Brisingida, Stichasteridae, and Asteriidae) emerged from a synthesis of morphological and molecular evidence. The majority of extinct forcipulatacean species have been placed in modern families. However, many of these fossil species are in need of revision, especially those species placed within the Asteriidae, the largest of all forcipulatacean families. Methods. In light of recent advancements in forcipulatacean systematics, we comprehensively reassess six well-preserved Jurassic forcipulatacean taxa, including the earliest crown-group members from the Hettangian (∼201.4 Ma), and also describe two new Jurassic genera, Forbesasterias gen. nov. and Marbleaster gen. nov. We assembled the largest and most comprehensive phylogenetic matrix for this group, sampling 42 fossil and extant forcipulatacean species for 120 morphological characters. To infer phylogenetic relationships and construct an evolutionary timeline for the diversification of major clades, we conducted a Bayesian tip-dating analysis incorporating the fossilized birth-death process. A total of 13 fossil species were sampled in our analysis, including six taxonomically revaluated herein, two recently reappraised species from the Jurassic, and five additional species from the Cretaceous and Miocene. Results. Contrary to prior assumptions, our results indicate that none of the Jurassic taxa investigated belong to Asteriidae or any other modern families, and instead represent stem-forcipulatids. Furthermore, our phylogenetic results suggest that Asteriidae likely originated during the late Cretaceous. Our findings highlight a greater How to cite this article Fau M, Wright DF, Ewin TAM, Gale AS, Villier L. 2024. Phylogenetic and taxonomic revisions of Jurassic sea stars support a delayed evolutionary origin of the Asteriidae. PeerJ 12:e18169 http://doi.org/10.7717/peerj.18169 early diversity within the Forcipulatacea than previously presumed, challenging existing perceptions of the evolutionary history of this significant clade of marine invertebrates.
Seawater magnesium (Mg) and calcium (Ca) have undergone secular fluctuations throughout the Phane... more Seawater magnesium (Mg) and calcium (Ca) have undergone secular fluctuations throughout the Phanerozoic, controlling whether the dominant calcium carbonate precipitant is calcite or aragonite + high-Mg calcite. Although these oscillations in seawater Mg/Ca ratios have been implicated as an important control on Phanerozoic diversification of calcifying marine organisms, determining the degree to which Mg/Ca ratios affected different clades requires integration of experimental data with historical patterns of biodiversity from the fossil record. We explore short-term and long-term responses of echinoderms to shifting calcite-aragonite seas by combining experimental and deep-time biodiversity investigations. While experimental results support a strong relationship between Mg/Ca ratios and shortterm echinoderm regeneration rates, patterns of Phanerozoic echinoderm diversification dynamics show no correspondence with Mg/Ca ratios or calcite-aragonite sea transitions. This decoupling between short- and long-term responses of echinoderms to seawater Mg/ Ca ratios suggests echinoderms were relatively unaffected by seawater chemistry throughout their evolutionary history, possibly due to their ability to alter skeletal Mg fractionation and/or adapt to gradual shifts in seawater chemistry. Notably, our results indicate a strict uniformitarian extrapolation of experimental results over geological time scales may not be appropriate for many calcifying marine invertebrates. Instead, the effect of seawater Mg/ Ca ratios should be evaluated for individual clades using both experimental and deep-time biodiversity data in a time series.
Full understanding of diversity dynamics during the Great Ordovician Biodiversification Event (GO... more Full understanding of diversity dynamics during the Great Ordovician Biodiversification Event (GOBE) requires analyses that investigate regional and species-level data and patterns. In this study, we combine bedding-plane scale data on brachiopod species counts and shell size collected from the Simpson Group of Oklahoma, USA, with species-level phylogenetic biogeography for three articulated brachiopod lineages that occurred throughout Laurentia. From these data, we ascertain that the primary influences of brachiopod shell size and diversity in the Simpson Group reflect global drivers, notably temporal position and paleotemperature. Similarly, the primary speciation pattern observed within Hesperorthis, Mimella, and Oepikina is the oscillation in speciation mode between dispersal and vicariance, which reflect the connection and disconnection of geographic areas, respectively. Processes that facilitate cyclical connectivity are global to regional in scale such as oceanographic changes, glacial cycles, or tectonic pulses. Therefore, both regional and continental scale analyses reinforce the importance of global factors in driving diversification during the GOBE.
'Asturicystis' havliceki Fatka & Kordule from the middle Cambrian of Bohemia (Czech Republic) is ... more '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.
Deuterostomes are the major division of animal life which includes sea stars, acorn worms, and hu... more Deuterostomes are the major division of animal life which includes sea stars, acorn worms, and humans, among a wide variety of ecologically and morphologically disparate taxa. However, their early evolution is poorly understood, due in part to their disparity, which makes identifying commonalities difficult, as well as their relatively poor early fossil record. Here, we review the available morphological, palaeontological, developmental, and molecular data to establish a framework for exploring the origins of this important and enigmatic group. Recent fossil discoveries strongly support a vermiform ancestor to the group Hemichordata, and a fusiform active swimmer as ancestor to Chordata. The diverse and anatomically bewildering variety of forms among the early echinoderms show evidence of both bilateral and radial symmetry. We consider four characteristics most critical for understanding the form and function of the last common ancestor to Deuterostomia: Hox gene expression patterns, larval morphology, the capacity for biomineralization, and the morphology of the pharyngeal region. We posit a deuterostome last common ancestor with a similar antero-posterior gene regulatory system to that found in modern acorn worms and cephalochordates, a simple planktonic larval form, which was later elaborated in the ambulacrarian lineage, the ability to secrete calcium minerals in a limited fashion, and a pharyngeal respiratory region composed of simple pores. This animal was likely to be motile in adult form, as opposed to the sessile origins that have been historically suggested. Recent debates regarding deuterostome monophyly as well as the wide array of deuterostome-affiliated problematica further suggest the possibility that those features were not only present in the last common ancestor of Deuterostomia, but potentially in the ur-bilaterian. The morphology and development of the early deuterostomes, therefore, underpin some of the most significant questions in the study of metazoan evolution.
Pivotal anatomical innovations often seem to appear by chance when viewed through the lens of the... more Pivotal anatomical innovations often seem to appear by chance when viewed through the lens of the fossil record. As a consequence, specific driving forces behind the origination of major organismal clades generally remain speculative. Here, we present a rare exception to this axiom by constraining the appearance of a diverse animal group (the living Ophiuroidea) to a single speciation event rather than hypothetical ancestors. Fossils belonging to a new pair of temporally consecutive species of brittle stars (Ophiopetagno paicei gen. et sp. nov. and Muldaster haakei gen. et sp. nov.) from the Silurian (444-419 Mya) of Sweden reveal a process of miniaturization that temporally coincides with a global extinction and environmental perturbation known as the Mulde Event. The reduction in size from O. paicei to M. haakei forced a structural simplification of the ophiuroid skeleton through ontogenetic retention of juvenile traits, thereby generating the modern brittle star bauplan.
Macroevolutionary inference has historically been treated as a two-step process, involving the in... more Macroevolutionary inference has historically been treated as a two-step process, involving the inference of a phylogenetic tree, and then inference of a macroevolutionary model using that tree. Newer models, such as the fossilized birth-death model, blend the two steps. These methods make more complete use of fossils than the previous generation of Bayesian phylogenetic models. They also involve many more parameters than prior models, including parameters about which empiricists may have little intuition. In this paper, we set forth a framework for fitting complex, hierarchical models.We ultimately fit and use a joint tree and diversification model to estimate a dated phylogeny of the Cincta (Echinodermata), a morphologically distinct group of Cambrian echinoderms that lack the five-fold radial symmetry characteristic of extant members of the phylum. Although the phylogeny of cinctans remains poorly supported in places, we show how models of character change and diversification cont...
Author :-The following queries have arisen during the editing of your manuscript. Please answer b... more Author :-The following queries have arisen during the editing of your manuscript. Please answer by making the requisite corrections directly in the e.proofing tool rather than marking them up on the PDF. This will ensure that your corrections are incorporated accurately and that your paper is published as quickly as possible. Query No. Description Author's Response AQ1 Please check your article carefully, coordinate with any co-authors and enter all final edits clearly in the eproof, remembering to save frequently. Once corrections are submitted, we cannot routinely make further changes to the article. AQ2 Note that the eproof should be amended in only one browser window at any one time; otherwise changes will be overwritten. AQ3 Author surnames have been highlighted. Please check these carefully and adjust if the first name or surname is marked up incorrectly. Note that changes here will affect indexing of your article in public repositories such as PubMed. Also, carefully check the spelling and numbering of all author names and affiliations, and the corresponding email address(es). AQ4 You cannot alter accepted Supplementary Information files except for critical changes to scientific content. If you do resupply any files, please also provide a brief (but complete) list of changes. If these are not considered scientific changes, any altered Supplementary files will not be used, only the originally accepted version will be published.
Journal of Paleontology, 2013
The orthidine brachiopod genera Plaesiomys and Hebertella are significant constituents of Late Or... more The orthidine brachiopod genera Plaesiomys and Hebertella are significant constituents of Late Ordovician benthic marine communities throughout Laurentia. Species-level phylogenetic analyses were conducted on both genera to inform systematic revisions and document evolutionary relationships. Phylogenetic analyses combined discrete and continuous characters, from which character states were determined using a statistical approach, and utilized both cladistic and Bayesian methodologies. Plaesiomys cutterensis, P. idahoensis, and P. occidentalis are herein recognized as distinct species rather than subspecies of P. subquadratus. Similarly, Hebertella montoyensis and H. prestonensis are recognized as distinct species separate from H. occidentalis, and H. richmondensis is recognized as a distinct species rather than a geographical variant of H. alveata. Hebertella subjugata is removed from its tentative synonymy with H. occidentalis and revalidated.The development of species-level evolut...
Elements of Paleontology, 2021
Macroevolutionary inference has historically been treated as a two-step process, involving the in... more Macroevolutionary inference has historically been treated as a two-step process, involving the inference of a tree, and then inference of a macroevolutionary model using that tree. Newer models blend the two steps. These methods make more complete use of fossils than the previous generation of Bayesian phylogenetic models. They also involve many more parameters than prior models, including parameters about which empiricists may have little intuition. In this Element, the authors set forth a framework for fitting complex, hierarchical models. The authors ultimately fit and use a joint tree and diversification model to estimate a dated phylogeny of the Cincta (Echinodermata), a morphologically distinct group of Cambrian echinoderms that lack the fivefold radial symmetry characteristic of extant members of the phylum. Although the phylogeny of cinctans remains poorly supported in places, this Element shows how models of character change and diversification contribute to understanding patterns of phylogenetic relatedness and testing macroevolutionary hypotheses.
Elements of Paleontology, 2021
Recent advances in statistical approaches called phylogenetic comparative methods (PCMs) have pro... more Recent advances in statistical approaches called phylogenetic
comparative methods (PCMs) have provided paleontologists with a
powerful set of analytical tools for investigating evolutionary tempo
and mode in fossil lineages. However, attempts to integrate PCMs with
fossil data often present workers with practical challenges or unfamiliar
literature. In this Element, we present guides to the theory behind and
the application of PCMs with fossil taxa. Based on an empirical dataset
of Paleozoic crinoids, we present example analyses to illustrate
common applications of PCMs to fossil data, including investigating
patterns of correlated trait evolution and macroevolutionary models of
morphological change. We emphasize the importance of accounting
for sources of uncertainty and discuss how to evaluate model fit and
adequacy. Finally, we discuss several promising methods for modeling
heterogeneous evolutionary dynamics with fossil phylogenies.
Integrating phylogeny-based approaches with the fossil record
provides a rigorous, quantitative perspective on understanding key
patterns in the history of life.
Time calibrated trees are challenging to estimate for many extinct groups of species due to the i... more Time calibrated trees are challenging to estimate for many extinct groups of species due to the incompleteness of the rock and fossil records. Additionally, the precise age of a sample is typically not known as it may have occurred at any time during the time interval spanned by the rock layer. Bayesian phylogenetic approaches provide a coherent framework for incorporating multiple sources of evidence and uncertainty. In this study, we simulate datasets with characteristics typical of Palaeozoic marine invertebrates, in terms of character and taxon sampling. We use these datasets to examine the impact of different age handling methods on estimated topologies and divergence times obtained using the fossilized birth-death process. Our results reiterate the importance of modeling fossil age uncertainty, although we find that the relative impact of fossil age uncertainty depends on both fossil taxon sampling and character sampling. Sampling the fossil ages as part of the inference gives topology and divergence time estimates that are as good as those obtained by fixing ages to the truth, whereas fixing fossil ages to incorrect values results in higher error and lower coverage. The relative effect increases with increased fossil and character sampling. Modeling fossil age uncertainty is thus critical, as fixing incorrect fossil ages will negate the benefits of improved fossil and character sampling.
Despite their importance for understanding phy-logeny, character evolution and classification, we... more Despite their importance for understanding phy-logeny, character evolution and classification, well-constrained homology relationships for posterior plating in crinoids have only recently been attempted. Here, we re-evaluate posterior plate homologies in all major crinoid lineages using development, fossil ontogenies and phylogenetic evidence. Based on these lines of evidence, we change terminology for some posterior plates to correct misnomers and make recommendations for updated terminology of others to better reflect homology. Among pentacrinoids (disparids, hybocri-nids, eucladids, flexibles and articulates) the relative position of posterior interray plates, not their topology, reflects homology. From proximal to distal, pentacrinoid posterior plates are the radianal, anal X and right sac plate, regardless of the total number of plates in the adult calyx. Camerate posterior plating contrasts with pentacrinoids, but insufficient data are available to resolve homology relationships between these two clades. More examples of early post-larval ontogeny are needed in camerates and other Palaeozoic crinoids.
Upper Ordovician (Katian) strata of the Lake Simcoe region of Ontario record a spectacularly dive... more Upper Ordovician (Katian) strata of the Lake Simcoe region of Ontario record a spectacularly diverse and abundant echinoderm fauna known as the Brechin Lagerstätte. Despite recognition as the most taxonomically diverse Katian crinoid paleocommunity, the Brechin Lagerstätte has received relatively little taxonomic study since Frank Springer published his classic monograph on the "Kirkfield fauna" in 1911. Using a new collection of exceptionally preserved material, we evaluate all dicyclic inadunate crinoids occurring in the Brechin Lagerstätte, which is predominantly comprised of cladids (Eucladida and Flexibilia). We document 15 species across 11 genera, including descriptions of two new genera and four new species. New taxa include Konieckicrinus bre-chinensis n. gen. n. sp., K. josephi n. gen. n. sp., Simcoecrinus mahalaki n. gen. n. sp., and Dendrocrinus simcoensis n. sp. Although cladids are not commonly considered major components of the Early Paleozoic Crinoid Macroevolutionary Fauna, which is traditionally conceived as dominated by disparids and diplobathrid camerates, they are the most diverse major lineage of crinoids occurring in the Brechin Lagerstätte. This unexpected result highlights the important roles of specimen-based taxonomy and systematic revisions in the study of large-scale diversity patterns. UUID: http://zoobank.org/09dda7c2-f2c5-4411-93be-3587ab1652ab
Palaeogeography, Palaeoclimatology, Palaeoecology, 2019
Integrating phylogenetic biology with paleoecology can provide a valuable context for understandi... more Integrating phylogenetic biology with paleoecology can provide a valuable context for understanding patterns of community structure and niche partitioning in ancient ecosystems. However, the lack of robust phylogenies for many fossil taxa precludes studies of this nature, particularly among marine invertebrates. Fossil Crinoidea (Echinodermata) comprise an ideal model system for phylogenetic community paleoecology for three reasons: (1) they preserve anatomical features that directly relate to feeding ecology, (2) assemblages of well-preserved specimens represent “ecological snapshots” in time, and (3) recent advances in resolving the crinoid tree of life have produced high-resolution phylogenies for Ordovician lineages. Here, we apply multivariate and phylogenetic comparative methods to investigate patterns of paleocommunity structure, niche partitioning, and ecomorphospace occupation in one of the earliest known complex crinoid paleocommunities, the Brechin Lagerstätte (Upper Ordovician, Katian). Results indicate niche differences among species were determined primarily by characters related to filtration fan morphology. Filtration fan density and body size distributions support phylogenetic niche conservatism, but traits related to the size of the feeding area are more labile and exhibit greater divergence than expected among closely related species. Finally, we compare changes in the shape and phylogenetic structure of niche distributions between the Brechin Lagerstätte and the Edwardsville crinoid fauna, a well-studied Mississippian (Viséan) paleocommunity, to examine patterns of community change across the Early to Middle Paleozoic Crinoid Macroevolutionary Faunas.
—The Brechin Lagerstätte (Katian, Ordovician) from the Lake Simcoe region of Ontario, Canada cont... more —The Brechin Lagerstätte (Katian, Ordovician) from the Lake Simcoe region of Ontario, Canada contains a diverse array of echinoderms. Here, we describe seven disparid and two hybocrinid crinoids (subclass Pentacrino-idea, infraclass Inadunata), including a new disparid species belonging to the Anomalocrinidae (order Homocrinida). In total, the disparids include Anomalocrinus astrictus n. sp.
The Upper Ordovician (lower Katian) Bobcaygeon and Verulam formations from the Lake Simcoe region... more The Upper Ordovician (lower Katian) Bobcaygeon and Verulam formations from the Lake Simcoe region of Ontario contain a highly diverse echinoderm assemblage that is herein recognized as a Konservat-Lagerstätte. Although fossil crinoids have long been recognized from these formations, the fauna has not received a comprehensive taxonomic evaluation since Springer's classic 1911 monograph. Recent extensive collection and preparation of new material from the Bobcaygeon and Verulam formations near Brechin, Ontario recovered numerous exceptionally preserved crinoid specimens with arms, stems, and attachment structures intact. The Brechin Lagerstätte is the most taxonomically diverse Katian crinoid fauna, with more than 20 crinoid genera represented in this collection. Here, all dicyclic crinoids belonging to subclass Camerata from the Brechin Lagerstätte are evaluated. The following four genera and seven species are described from the fauna, including one new genus and four new species: Reteocrinus stellaris, Reteocrinus alveolatus, Archaeocrinus sundayae n. sp., Archaeocrinus maraensis n. sp., Priscillacrinus elegans n. gen. n. sp., Cleiocrinus regius, and Cleiocrinus lepidotus n. sp. The exceptional preservation of this collection provides an opportunity to describe more fully the morphologic and ontogenetic details of known Ordovician crinoid taxa, to conduct a taxonomic re-evaluation of many species, to describe new taxa, and to provide a framework for subsequent studies of crinoid community paleoecology.
To better understand the patterns and processes shaping large-scale phenotypic diversification, I... more To better understand the patterns and processes shaping large-scale phenotypic diversification, I integrate palaeobiological and phylogenetic perspectives to investigate a ~200-million-year radiation using a global sample of Palaeozoic crinoid echinoderms. Results indicate the early history of crinoid diversification is characterized by early burst dynamics with decelerating morphologic rates. However, in contrast with expectation for a single "early burst" model, morphospace continued to expand following a slowdown in rates. In addition, I find evidence for an isolated peak in morphologic rates occurring late in the clade's history. This episode of elevated rates is not associated with increased disparity, morphologic novelty, or the radiation of a single subclade. Instead, this episode of elevated rates involved multiple subclade radiations driven by environmental change toward a pre-existing adaptive optimum. The decoupling of morphologic disparity with rates of change suggests phenotypic rates are primarily shaped by ecologic factors rather than the origination of morphologic novelty alone. These results suggest phenotypic diversification is far more complex than models commonly assumed in comparative biology. Furthermore, palaeontological disparity patterns are not a reliable proxy for rates after an initial diversifying phase. These issues highlight the need for continued synthesis between fossil and phylogenetic approaches to macroevolution.
This study documents previously unknown tax-onomic and morphological diversity among early Palaeo... more This study documents previously unknown tax-onomic and morphological diversity among early Palaeozoic crinoids. Based on highly complete, well preserved crown material, we describe two new genera from the Ordovician and Silurian of the Baltic region (Estonia) that provide insight into two major features of the geological history of crinoids: the early evolution of the flexible clade during the Great Ordovician Biodiversification Event (GOBE), and their diversification history surrounding the end-Ordovician mass extinction. The unexpected occurrence of a highly derived sagenocrinid, Tintinnabulicrinus estoniensis gen. et. sp. nov., from Upper Ordovician (lower Katian) rocks of the Baltic palaeocontinent provides high-resolution temporal , taxonomic and palaeobiogeographical constraints on the origin and early evolution of the Flexibilia. The Silurian (lower Rhuddanian, Llandovery) Paerticrinus arvosus gen. et sp. nov. is the oldest known Silurian crinoid from Baltica and thus provides the earliest Baltic record of crinoids following the aftermath of the end-Ordovician mass extinction. A Bayesian 'fossil tip-dating' analysis implementing the fossilized birth–death process and a relaxed morphological clock model suggests that flexibles evolved c. 3 million years prior to their oldest fossil record, potentially involving an ancestor–descendant relationship (via 'budding' cladogenesis or anagenesis) with the paraphyletic cladid Cupulocrinus. The sagenocrinid subclade rapidly diverged from 'tax-ocrinid' grade crinoids during the final stages of the GOBE, culminating in maximal diversity among Ordovician crinoid faunas on a global scale. Remarkably, diversification patterns indicate little taxonomic turnover among flexibles across the Late Ordovician mass extinction. However, the elimination of closely related clades may have helped pave the way for their subsequent Silurian diversification and increased ecological role in post-Ordovician Palaeozoic marine communities. This study highlights the significance of studies reporting faunas from undersampled palaeogeo-graphical regions for clade-based phylogenetic studies and improving estimates of global biodiversity through geological time.
A major goal of biological classification is to provide a system that conveys phylogenetic relati... more A major goal of biological classification is to provide a system that conveys phylogenetic relationships while facilitating lucid communication among researchers. Phylogenetic taxonomy is a useful framework for defining clades and delineating their taxonomic content based on well-supported phylogenetic hypotheses. The Crinoidea (Echinodermata) is one of the five major clades of living echinoderms and has a rich fossil record spanning nearly a half billion years. Using principles of phylogenetic taxonomy and recent phylogenetic analyses, we provide the first phylogeny-based definition for the Clade Crinoidea and its constituent subclades. A series of stem- and node-based definitions are provided for all major taxa traditionally recognized within the Crinoidea, including the Camerata, Disparida, Hybocrinida, Cladida, Flexibilia, and the Articulata. Following recommendations proposed in recent revisions, we recognize several new clades, including the Eucamerata Cole (this issue), Porocrinoidea Wright (this issue), and Eucladida Wright (this issue). In addition, recent phylogenetic analyses support the resurrection of two names previously abandoned in the crinoid taxonomic literature: the Pentacrinoidea Jaekel, 1918 and Inadunata Wachsmuth and Springer, 1885. Lastly, a phylogenetic perspective is used to inform a comprehensive revision of the traditional rank-based classification. Although an attempt was made to minimize changes to the rank-based system, numerous changes were necessary in some cases to achieve monophyly. These phylogeny-based classifications provide a useful template for paleontologists, biologists, and non-experts alike to better explore evolutionary patterns and processes with fossil and living crinoids.
Background. The superorder Forcipulatacea is a major clade of sea stars with approximately 400 ex... more Background. The superorder Forcipulatacea is a major clade of sea stars with approximately 400 extant species across three orders (Forcipulatida, Brisingida, Zorocallida). Over the past century, the systematics of Forcipulatacea have undergone multiple revisions by various authors, with some considering numerous families such as Asteriidae, Zoroasteridae, Pedicellasteridae, Stichasteridae, Heliasteridae, Labidiasteridae, and Neomorphasteridae, while others recognized only two families (i.e., Asteriidae and Zoroasteridae). Recent molecular analyses have shown the artificial nature of some of these groupings. Notably, four well-supported clades (Zorocallida, Brisingida, Stichasteridae, and Asteriidae) emerged from a synthesis of morphological and molecular evidence. The majority of extinct forcipulatacean species have been placed in modern families. However, many of these fossil species are in need of revision, especially those species placed within the Asteriidae, the largest of all forcipulatacean families. Methods. In light of recent advancements in forcipulatacean systematics, we comprehensively reassess six well-preserved Jurassic forcipulatacean taxa, including the earliest crown-group members from the Hettangian (∼201.4 Ma), and also describe two new Jurassic genera, Forbesasterias gen. nov. and Marbleaster gen. nov. We assembled the largest and most comprehensive phylogenetic matrix for this group, sampling 42 fossil and extant forcipulatacean species for 120 morphological characters. To infer phylogenetic relationships and construct an evolutionary timeline for the diversification of major clades, we conducted a Bayesian tip-dating analysis incorporating the fossilized birth-death process. A total of 13 fossil species were sampled in our analysis, including six taxonomically revaluated herein, two recently reappraised species from the Jurassic, and five additional species from the Cretaceous and Miocene. Results. Contrary to prior assumptions, our results indicate that none of the Jurassic taxa investigated belong to Asteriidae or any other modern families, and instead represent stem-forcipulatids. Furthermore, our phylogenetic results suggest that Asteriidae likely originated during the late Cretaceous. Our findings highlight a greater How to cite this article Fau M, Wright DF, Ewin TAM, Gale AS, Villier L. 2024. Phylogenetic and taxonomic revisions of Jurassic sea stars support a delayed evolutionary origin of the Asteriidae. PeerJ 12:e18169 http://doi.org/10.7717/peerj.18169 early diversity within the Forcipulatacea than previously presumed, challenging existing perceptions of the evolutionary history of this significant clade of marine invertebrates.
Seawater magnesium (Mg) and calcium (Ca) have undergone secular fluctuations throughout the Phane... more Seawater magnesium (Mg) and calcium (Ca) have undergone secular fluctuations throughout the Phanerozoic, controlling whether the dominant calcium carbonate precipitant is calcite or aragonite + high-Mg calcite. Although these oscillations in seawater Mg/Ca ratios have been implicated as an important control on Phanerozoic diversification of calcifying marine organisms, determining the degree to which Mg/Ca ratios affected different clades requires integration of experimental data with historical patterns of biodiversity from the fossil record. We explore short-term and long-term responses of echinoderms to shifting calcite-aragonite seas by combining experimental and deep-time biodiversity investigations. While experimental results support a strong relationship between Mg/Ca ratios and shortterm echinoderm regeneration rates, patterns of Phanerozoic echinoderm diversification dynamics show no correspondence with Mg/Ca ratios or calcite-aragonite sea transitions. This decoupling between short- and long-term responses of echinoderms to seawater Mg/ Ca ratios suggests echinoderms were relatively unaffected by seawater chemistry throughout their evolutionary history, possibly due to their ability to alter skeletal Mg fractionation and/or adapt to gradual shifts in seawater chemistry. Notably, our results indicate a strict uniformitarian extrapolation of experimental results over geological time scales may not be appropriate for many calcifying marine invertebrates. Instead, the effect of seawater Mg/ Ca ratios should be evaluated for individual clades using both experimental and deep-time biodiversity data in a time series.
Full understanding of diversity dynamics during the Great Ordovician Biodiversification Event (GO... more Full understanding of diversity dynamics during the Great Ordovician Biodiversification Event (GOBE) requires analyses that investigate regional and species-level data and patterns. In this study, we combine bedding-plane scale data on brachiopod species counts and shell size collected from the Simpson Group of Oklahoma, USA, with species-level phylogenetic biogeography for three articulated brachiopod lineages that occurred throughout Laurentia. From these data, we ascertain that the primary influences of brachiopod shell size and diversity in the Simpson Group reflect global drivers, notably temporal position and paleotemperature. Similarly, the primary speciation pattern observed within Hesperorthis, Mimella, and Oepikina is the oscillation in speciation mode between dispersal and vicariance, which reflect the connection and disconnection of geographic areas, respectively. Processes that facilitate cyclical connectivity are global to regional in scale such as oceanographic changes, glacial cycles, or tectonic pulses. Therefore, both regional and continental scale analyses reinforce the importance of global factors in driving diversification during the GOBE.
'Asturicystis' havliceki Fatka & Kordule from the middle Cambrian of Bohemia (Czech Republic) is ... more '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.
Deuterostomes are the major division of animal life which includes sea stars, acorn worms, and hu... more Deuterostomes are the major division of animal life which includes sea stars, acorn worms, and humans, among a wide variety of ecologically and morphologically disparate taxa. However, their early evolution is poorly understood, due in part to their disparity, which makes identifying commonalities difficult, as well as their relatively poor early fossil record. Here, we review the available morphological, palaeontological, developmental, and molecular data to establish a framework for exploring the origins of this important and enigmatic group. Recent fossil discoveries strongly support a vermiform ancestor to the group Hemichordata, and a fusiform active swimmer as ancestor to Chordata. The diverse and anatomically bewildering variety of forms among the early echinoderms show evidence of both bilateral and radial symmetry. We consider four characteristics most critical for understanding the form and function of the last common ancestor to Deuterostomia: Hox gene expression patterns, larval morphology, the capacity for biomineralization, and the morphology of the pharyngeal region. We posit a deuterostome last common ancestor with a similar antero-posterior gene regulatory system to that found in modern acorn worms and cephalochordates, a simple planktonic larval form, which was later elaborated in the ambulacrarian lineage, the ability to secrete calcium minerals in a limited fashion, and a pharyngeal respiratory region composed of simple pores. This animal was likely to be motile in adult form, as opposed to the sessile origins that have been historically suggested. Recent debates regarding deuterostome monophyly as well as the wide array of deuterostome-affiliated problematica further suggest the possibility that those features were not only present in the last common ancestor of Deuterostomia, but potentially in the ur-bilaterian. The morphology and development of the early deuterostomes, therefore, underpin some of the most significant questions in the study of metazoan evolution.
Pivotal anatomical innovations often seem to appear by chance when viewed through the lens of the... more Pivotal anatomical innovations often seem to appear by chance when viewed through the lens of the fossil record. As a consequence, specific driving forces behind the origination of major organismal clades generally remain speculative. Here, we present a rare exception to this axiom by constraining the appearance of a diverse animal group (the living Ophiuroidea) to a single speciation event rather than hypothetical ancestors. Fossils belonging to a new pair of temporally consecutive species of brittle stars (Ophiopetagno paicei gen. et sp. nov. and Muldaster haakei gen. et sp. nov.) from the Silurian (444-419 Mya) of Sweden reveal a process of miniaturization that temporally coincides with a global extinction and environmental perturbation known as the Mulde Event. The reduction in size from O. paicei to M. haakei forced a structural simplification of the ophiuroid skeleton through ontogenetic retention of juvenile traits, thereby generating the modern brittle star bauplan.
Macroevolutionary inference has historically been treated as a two-step process, involving the in... more Macroevolutionary inference has historically been treated as a two-step process, involving the inference of a phylogenetic tree, and then inference of a macroevolutionary model using that tree. Newer models, such as the fossilized birth-death model, blend the two steps. These methods make more complete use of fossils than the previous generation of Bayesian phylogenetic models. They also involve many more parameters than prior models, including parameters about which empiricists may have little intuition. In this paper, we set forth a framework for fitting complex, hierarchical models.We ultimately fit and use a joint tree and diversification model to estimate a dated phylogeny of the Cincta (Echinodermata), a morphologically distinct group of Cambrian echinoderms that lack the five-fold radial symmetry characteristic of extant members of the phylum. Although the phylogeny of cinctans remains poorly supported in places, we show how models of character change and diversification cont...
Author :-The following queries have arisen during the editing of your manuscript. Please answer b... more Author :-The following queries have arisen during the editing of your manuscript. Please answer by making the requisite corrections directly in the e.proofing tool rather than marking them up on the PDF. This will ensure that your corrections are incorporated accurately and that your paper is published as quickly as possible. Query No. Description Author's Response AQ1 Please check your article carefully, coordinate with any co-authors and enter all final edits clearly in the eproof, remembering to save frequently. Once corrections are submitted, we cannot routinely make further changes to the article. AQ2 Note that the eproof should be amended in only one browser window at any one time; otherwise changes will be overwritten. AQ3 Author surnames have been highlighted. Please check these carefully and adjust if the first name or surname is marked up incorrectly. Note that changes here will affect indexing of your article in public repositories such as PubMed. Also, carefully check the spelling and numbering of all author names and affiliations, and the corresponding email address(es). AQ4 You cannot alter accepted Supplementary Information files except for critical changes to scientific content. If you do resupply any files, please also provide a brief (but complete) list of changes. If these are not considered scientific changes, any altered Supplementary files will not be used, only the originally accepted version will be published.
Journal of Paleontology, 2013
The orthidine brachiopod genera Plaesiomys and Hebertella are significant constituents of Late Or... more The orthidine brachiopod genera Plaesiomys and Hebertella are significant constituents of Late Ordovician benthic marine communities throughout Laurentia. Species-level phylogenetic analyses were conducted on both genera to inform systematic revisions and document evolutionary relationships. Phylogenetic analyses combined discrete and continuous characters, from which character states were determined using a statistical approach, and utilized both cladistic and Bayesian methodologies. Plaesiomys cutterensis, P. idahoensis, and P. occidentalis are herein recognized as distinct species rather than subspecies of P. subquadratus. Similarly, Hebertella montoyensis and H. prestonensis are recognized as distinct species separate from H. occidentalis, and H. richmondensis is recognized as a distinct species rather than a geographical variant of H. alveata. Hebertella subjugata is removed from its tentative synonymy with H. occidentalis and revalidated.The development of species-level evolut...
Elements of Paleontology, 2021
Macroevolutionary inference has historically been treated as a two-step process, involving the in... more Macroevolutionary inference has historically been treated as a two-step process, involving the inference of a tree, and then inference of a macroevolutionary model using that tree. Newer models blend the two steps. These methods make more complete use of fossils than the previous generation of Bayesian phylogenetic models. They also involve many more parameters than prior models, including parameters about which empiricists may have little intuition. In this Element, the authors set forth a framework for fitting complex, hierarchical models. The authors ultimately fit and use a joint tree and diversification model to estimate a dated phylogeny of the Cincta (Echinodermata), a morphologically distinct group of Cambrian echinoderms that lack the fivefold radial symmetry characteristic of extant members of the phylum. Although the phylogeny of cinctans remains poorly supported in places, this Element shows how models of character change and diversification contribute to understanding patterns of phylogenetic relatedness and testing macroevolutionary hypotheses.
Elements of Paleontology, 2021
Recent advances in statistical approaches called phylogenetic comparative methods (PCMs) have pro... more Recent advances in statistical approaches called phylogenetic
comparative methods (PCMs) have provided paleontologists with a
powerful set of analytical tools for investigating evolutionary tempo
and mode in fossil lineages. However, attempts to integrate PCMs with
fossil data often present workers with practical challenges or unfamiliar
literature. In this Element, we present guides to the theory behind and
the application of PCMs with fossil taxa. Based on an empirical dataset
of Paleozoic crinoids, we present example analyses to illustrate
common applications of PCMs to fossil data, including investigating
patterns of correlated trait evolution and macroevolutionary models of
morphological change. We emphasize the importance of accounting
for sources of uncertainty and discuss how to evaluate model fit and
adequacy. Finally, we discuss several promising methods for modeling
heterogeneous evolutionary dynamics with fossil phylogenies.
Integrating phylogeny-based approaches with the fossil record
provides a rigorous, quantitative perspective on understanding key
patterns in the history of life.
Time calibrated trees are challenging to estimate for many extinct groups of species due to the i... more Time calibrated trees are challenging to estimate for many extinct groups of species due to the incompleteness of the rock and fossil records. Additionally, the precise age of a sample is typically not known as it may have occurred at any time during the time interval spanned by the rock layer. Bayesian phylogenetic approaches provide a coherent framework for incorporating multiple sources of evidence and uncertainty. In this study, we simulate datasets with characteristics typical of Palaeozoic marine invertebrates, in terms of character and taxon sampling. We use these datasets to examine the impact of different age handling methods on estimated topologies and divergence times obtained using the fossilized birth-death process. Our results reiterate the importance of modeling fossil age uncertainty, although we find that the relative impact of fossil age uncertainty depends on both fossil taxon sampling and character sampling. Sampling the fossil ages as part of the inference gives topology and divergence time estimates that are as good as those obtained by fixing ages to the truth, whereas fixing fossil ages to incorrect values results in higher error and lower coverage. The relative effect increases with increased fossil and character sampling. Modeling fossil age uncertainty is thus critical, as fixing incorrect fossil ages will negate the benefits of improved fossil and character sampling.
Despite their importance for understanding phy-logeny, character evolution and classification, we... more Despite their importance for understanding phy-logeny, character evolution and classification, well-constrained homology relationships for posterior plating in crinoids have only recently been attempted. Here, we re-evaluate posterior plate homologies in all major crinoid lineages using development, fossil ontogenies and phylogenetic evidence. Based on these lines of evidence, we change terminology for some posterior plates to correct misnomers and make recommendations for updated terminology of others to better reflect homology. Among pentacrinoids (disparids, hybocri-nids, eucladids, flexibles and articulates) the relative position of posterior interray plates, not their topology, reflects homology. From proximal to distal, pentacrinoid posterior plates are the radianal, anal X and right sac plate, regardless of the total number of plates in the adult calyx. Camerate posterior plating contrasts with pentacrinoids, but insufficient data are available to resolve homology relationships between these two clades. More examples of early post-larval ontogeny are needed in camerates and other Palaeozoic crinoids.
Upper Ordovician (Katian) strata of the Lake Simcoe region of Ontario record a spectacularly dive... more Upper Ordovician (Katian) strata of the Lake Simcoe region of Ontario record a spectacularly diverse and abundant echinoderm fauna known as the Brechin Lagerstätte. Despite recognition as the most taxonomically diverse Katian crinoid paleocommunity, the Brechin Lagerstätte has received relatively little taxonomic study since Frank Springer published his classic monograph on the "Kirkfield fauna" in 1911. Using a new collection of exceptionally preserved material, we evaluate all dicyclic inadunate crinoids occurring in the Brechin Lagerstätte, which is predominantly comprised of cladids (Eucladida and Flexibilia). We document 15 species across 11 genera, including descriptions of two new genera and four new species. New taxa include Konieckicrinus bre-chinensis n. gen. n. sp., K. josephi n. gen. n. sp., Simcoecrinus mahalaki n. gen. n. sp., and Dendrocrinus simcoensis n. sp. Although cladids are not commonly considered major components of the Early Paleozoic Crinoid Macroevolutionary Fauna, which is traditionally conceived as dominated by disparids and diplobathrid camerates, they are the most diverse major lineage of crinoids occurring in the Brechin Lagerstätte. This unexpected result highlights the important roles of specimen-based taxonomy and systematic revisions in the study of large-scale diversity patterns. UUID: http://zoobank.org/09dda7c2-f2c5-4411-93be-3587ab1652ab
Palaeogeography, Palaeoclimatology, Palaeoecology, 2019
Integrating phylogenetic biology with paleoecology can provide a valuable context for understandi... more Integrating phylogenetic biology with paleoecology can provide a valuable context for understanding patterns of community structure and niche partitioning in ancient ecosystems. However, the lack of robust phylogenies for many fossil taxa precludes studies of this nature, particularly among marine invertebrates. Fossil Crinoidea (Echinodermata) comprise an ideal model system for phylogenetic community paleoecology for three reasons: (1) they preserve anatomical features that directly relate to feeding ecology, (2) assemblages of well-preserved specimens represent “ecological snapshots” in time, and (3) recent advances in resolving the crinoid tree of life have produced high-resolution phylogenies for Ordovician lineages. Here, we apply multivariate and phylogenetic comparative methods to investigate patterns of paleocommunity structure, niche partitioning, and ecomorphospace occupation in one of the earliest known complex crinoid paleocommunities, the Brechin Lagerstätte (Upper Ordovician, Katian). Results indicate niche differences among species were determined primarily by characters related to filtration fan morphology. Filtration fan density and body size distributions support phylogenetic niche conservatism, but traits related to the size of the feeding area are more labile and exhibit greater divergence than expected among closely related species. Finally, we compare changes in the shape and phylogenetic structure of niche distributions between the Brechin Lagerstätte and the Edwardsville crinoid fauna, a well-studied Mississippian (Viséan) paleocommunity, to examine patterns of community change across the Early to Middle Paleozoic Crinoid Macroevolutionary Faunas.
—The Brechin Lagerstätte (Katian, Ordovician) from the Lake Simcoe region of Ontario, Canada cont... more —The Brechin Lagerstätte (Katian, Ordovician) from the Lake Simcoe region of Ontario, Canada contains a diverse array of echinoderms. Here, we describe seven disparid and two hybocrinid crinoids (subclass Pentacrino-idea, infraclass Inadunata), including a new disparid species belonging to the Anomalocrinidae (order Homocrinida). In total, the disparids include Anomalocrinus astrictus n. sp.
The Upper Ordovician (lower Katian) Bobcaygeon and Verulam formations from the Lake Simcoe region... more The Upper Ordovician (lower Katian) Bobcaygeon and Verulam formations from the Lake Simcoe region of Ontario contain a highly diverse echinoderm assemblage that is herein recognized as a Konservat-Lagerstätte. Although fossil crinoids have long been recognized from these formations, the fauna has not received a comprehensive taxonomic evaluation since Springer's classic 1911 monograph. Recent extensive collection and preparation of new material from the Bobcaygeon and Verulam formations near Brechin, Ontario recovered numerous exceptionally preserved crinoid specimens with arms, stems, and attachment structures intact. The Brechin Lagerstätte is the most taxonomically diverse Katian crinoid fauna, with more than 20 crinoid genera represented in this collection. Here, all dicyclic crinoids belonging to subclass Camerata from the Brechin Lagerstätte are evaluated. The following four genera and seven species are described from the fauna, including one new genus and four new species: Reteocrinus stellaris, Reteocrinus alveolatus, Archaeocrinus sundayae n. sp., Archaeocrinus maraensis n. sp., Priscillacrinus elegans n. gen. n. sp., Cleiocrinus regius, and Cleiocrinus lepidotus n. sp. The exceptional preservation of this collection provides an opportunity to describe more fully the morphologic and ontogenetic details of known Ordovician crinoid taxa, to conduct a taxonomic re-evaluation of many species, to describe new taxa, and to provide a framework for subsequent studies of crinoid community paleoecology.
To better understand the patterns and processes shaping large-scale phenotypic diversification, I... more To better understand the patterns and processes shaping large-scale phenotypic diversification, I integrate palaeobiological and phylogenetic perspectives to investigate a ~200-million-year radiation using a global sample of Palaeozoic crinoid echinoderms. Results indicate the early history of crinoid diversification is characterized by early burst dynamics with decelerating morphologic rates. However, in contrast with expectation for a single "early burst" model, morphospace continued to expand following a slowdown in rates. In addition, I find evidence for an isolated peak in morphologic rates occurring late in the clade's history. This episode of elevated rates is not associated with increased disparity, morphologic novelty, or the radiation of a single subclade. Instead, this episode of elevated rates involved multiple subclade radiations driven by environmental change toward a pre-existing adaptive optimum. The decoupling of morphologic disparity with rates of change suggests phenotypic rates are primarily shaped by ecologic factors rather than the origination of morphologic novelty alone. These results suggest phenotypic diversification is far more complex than models commonly assumed in comparative biology. Furthermore, palaeontological disparity patterns are not a reliable proxy for rates after an initial diversifying phase. These issues highlight the need for continued synthesis between fossil and phylogenetic approaches to macroevolution.
This study documents previously unknown tax-onomic and morphological diversity among early Palaeo... more This study documents previously unknown tax-onomic and morphological diversity among early Palaeozoic crinoids. Based on highly complete, well preserved crown material, we describe two new genera from the Ordovician and Silurian of the Baltic region (Estonia) that provide insight into two major features of the geological history of crinoids: the early evolution of the flexible clade during the Great Ordovician Biodiversification Event (GOBE), and their diversification history surrounding the end-Ordovician mass extinction. The unexpected occurrence of a highly derived sagenocrinid, Tintinnabulicrinus estoniensis gen. et. sp. nov., from Upper Ordovician (lower Katian) rocks of the Baltic palaeocontinent provides high-resolution temporal , taxonomic and palaeobiogeographical constraints on the origin and early evolution of the Flexibilia. The Silurian (lower Rhuddanian, Llandovery) Paerticrinus arvosus gen. et sp. nov. is the oldest known Silurian crinoid from Baltica and thus provides the earliest Baltic record of crinoids following the aftermath of the end-Ordovician mass extinction. A Bayesian 'fossil tip-dating' analysis implementing the fossilized birth–death process and a relaxed morphological clock model suggests that flexibles evolved c. 3 million years prior to their oldest fossil record, potentially involving an ancestor–descendant relationship (via 'budding' cladogenesis or anagenesis) with the paraphyletic cladid Cupulocrinus. The sagenocrinid subclade rapidly diverged from 'tax-ocrinid' grade crinoids during the final stages of the GOBE, culminating in maximal diversity among Ordovician crinoid faunas on a global scale. Remarkably, diversification patterns indicate little taxonomic turnover among flexibles across the Late Ordovician mass extinction. However, the elimination of closely related clades may have helped pave the way for their subsequent Silurian diversification and increased ecological role in post-Ordovician Palaeozoic marine communities. This study highlights the significance of studies reporting faunas from undersampled palaeogeo-graphical regions for clade-based phylogenetic studies and improving estimates of global biodiversity through geological time.
A major goal of biological classification is to provide a system that conveys phylogenetic relati... more A major goal of biological classification is to provide a system that conveys phylogenetic relationships while facilitating lucid communication among researchers. Phylogenetic taxonomy is a useful framework for defining clades and delineating their taxonomic content based on well-supported phylogenetic hypotheses. The Crinoidea (Echinodermata) is one of the five major clades of living echinoderms and has a rich fossil record spanning nearly a half billion years. Using principles of phylogenetic taxonomy and recent phylogenetic analyses, we provide the first phylogeny-based definition for the Clade Crinoidea and its constituent subclades. A series of stem- and node-based definitions are provided for all major taxa traditionally recognized within the Crinoidea, including the Camerata, Disparida, Hybocrinida, Cladida, Flexibilia, and the Articulata. Following recommendations proposed in recent revisions, we recognize several new clades, including the Eucamerata Cole (this issue), Porocrinoidea Wright (this issue), and Eucladida Wright (this issue). In addition, recent phylogenetic analyses support the resurrection of two names previously abandoned in the crinoid taxonomic literature: the Pentacrinoidea Jaekel, 1918 and Inadunata Wachsmuth and Springer, 1885. Lastly, a phylogenetic perspective is used to inform a comprehensive revision of the traditional rank-based classification. Although an attempt was made to minimize changes to the rank-based system, numerous changes were necessary in some cases to achieve monophyly. These phylogeny-based classifications provide a useful template for paleontologists, biologists, and non-experts alike to better explore evolutionary patterns and processes with fossil and living crinoids.
Blog I wrote on fossils and phylogenetics (not peer reviewed).