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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.

The Brechin Lagerstätte of southern Ontario contains an exceptionally diverse and well-preserved Late Ordovician (Katian) crinoid fauna. We describe four genera and eight species of camerate crinoids from the Brechin Lagerstätte, including six new species. Consequently, the total diversity of the fauna now stands at 27 genera and 39 nominal species, thereby making it the most taxonomically diverse Ordovician crinoid fauna known. Taxa described include the diplobathrid Pararchaeocrinus kiddi new species and the monobathrids Glyptocrinus ramulosus Billings, 1856, Periglyptocrinus priscus (Billings, 1857a), Periglyptocrinus astricus new species, Periglyptocrinus kevinbretti new species, Periglyptocrinus mcdonaldi new species, Periglyptocrinus silvosus new species, and Abludoglyptocrinus steinheimerae new species. We summarize the taxonomic composition, diversity, and abundance distribution of all known crinoids from the Brechin Lagerstätte to better characterize the paleoecological structure and complexity of the community. We establish that the fauna is dominated by the subclass Pentacrinoidea, both in terms of abundance and species richness. In addition, we analyze species-level abundance data using Relative Abundance Distribution (RAD) models to evaluate the ecological complexity of the paleocommunity. We found that community structure of the Brechin Lagerstätte is best explained by an ecologically ‘complex’ RAD model, which suggests that species partitioned niches along multiple resource axes and/or the presence of multiple ecological ways of life. These results indicate that the Brechin Lagerstätte is significant not only for being the most taxonomically diverse Katian crinoid assemblage, but also for being an early ecologically complex fauna that developed in the wake of the Great Ordovician Biodiversification Event.UUID: http://zoobank.org/f86582ed-5db6-469E-befe-34b801f9a113

Fossil crinoids are exceptionally suited to deep-time studies of community paleoecology and niche partitioning. By merging ecomorphological trait and phylogenetic data, this Element summarizes niche occupation and community paleoecology of crinoids from the Bromide fauna of Oklahoma (Sandbian, Upper Ordovician). Patterns of community structure and niche evolution are evaluated over a ~5 million-year period through comparison with the Brechin Lagerstätte (Katian, Upper Ordovician). The authors establish filtration fan density, food size selectivity, and body size as major axes defining niche differentiation, and niche occupation is strongly controlled by phylogeny. Ecological strategies were relatively static over the study interval at high taxonomic scales, but niche differentiation and specialization increased in most subclades. Changes in disparity and species richness indicate the transition between the early-middle Paleozoic Crinoid Evolutionary Faunas was already underway by the Katian due to ecological drivers and was not triggered by the Late Ordovician mass extinction.

No abstract available.

Identifying correlates of extinction risk is important for understanding the underlying mechanisms driving differential rates of extinction and variability in the temporal durations of taxa. Increasingly, it is recognized that the effects of multiple, potentially interacting variables and phylogenetic relationships should be incorporated when studying extinction selectivity to account for covariation of traits and shared evolutionary history. Here, I explore a variety of biological and ecological controls on genus longevity in the global fossil record of diplobathrid crinoids by analyzing the combined effects of species richness, habitat preference, body size, filtration fan density, and food size selectivity. I employ a suite of taxic and phylogenetic approaches to (1) quantitatively compare and rank the relative effects of multiple factors on taxonomic longevity and (2) determine how phylogenetic comparative approaches alter interpretations of extinction selectivity.I find controls on diplobathrid genus duration are hierarchically structured, where species richness is the primary predictor of duration, habitat is the secondary predictor, and combinations of ecological and biological traits are tertiary controls. Ecology plays an important but complex role in the generation of crinoid macroevolutionary patterns. Notably, tolerance of environmental heterogeneity promotes increased genus duration across diplobathrid crinoids, and the effects of traits related to feeding ecology vary depending on habitat lithology. Finally, I find accounting for phylogeny does not consistently decrease the significance of correlations between traits and genus duration, as is commonly expected. Instead, the strength of relationships between traits and duration may increase, decrease, or remain statistically similar, and both the magnitude and direction of these shifts are generally unpredictable. However, traits with strong correlations and/or moderately large effect sizes (Cohen'sf2> 0.15) under taxic approaches tend to remain qualitatively unchanged under phylogenetic approaches.

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 Lagerstatte (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 Lagerstatte and the Edwardsville crinoid fauna, a well-studied Mississippian (Visean) paleocommunity, to examine patterns of community change across the Early to Middle Paleozoic Crinoid Macroevolutionary Faunas.

Selectivity of mass extinctions is thought to play a major role in coupling or decoupling of taxonomic, morphological, and ecological diversity, yet these measures have never been jointly evaluated within a single clade over multiple mass extinctions. We investigate extinction selectivity and changes in taxonomic diversity, morphological disparity, and functional ecology over the ~160-million-year evolutionary history of diplobathrid crinoids (Echinodermata), which spans two mass extinctions. Whereas previous studies documented extinction selectivity for crinoids during background extinction, we find no evidence for selectivity during mass extinctions. Despite no evidence for extinction selectivity, disparity remains strongly correlated with richness over extinction events, contradicting expected patterns of disparity given nonselective extinction. Results indicate that (i) disparity and richness can remain coupled across extinctions even when selective extinction does not occur, (ii) simultaneous decreases in taxonomic diversity and disparity are insufficient evidence for extinction selectivity, and (iii) selectivity differs between background and mass extinction regimes.

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 Pentacrinoidea, infraclass Inadunata), including a new disparid species belonging to the Anomalocrinidae (order Homocrinida). In total, the disparids include Anomalocrinus astrictus n. sp.; Cremacrinus guttenbergensis Kolata, 1975; C. inaequalis Billings, 1859; Daedalocrinus bellevillensis Billings, 1883; Eustenocrinus springeri Ulrich, 1925; Iocrinus trentonensis Walcott, 1883; and Isotomocrinus tenuis Billings, 1857b. The hybocrinids include Hybocrinus tumidus Billings, 1857a and Hybocystites problematicus Wetherby, 1880. Previously known from only the holotype, three additional specimens of E. springeri expand our understanding of this unusual crinoid. Nomenclatural acts include: (1) the recommended designation of D. kirki Ulrich, 1925 as a junior synonym of D. bellevillensis is followed; (2) Hybocrinus pristinus Billings, 1858 is designated as a junior synonym of H. tumidus, and previous decisions are followed to retain Hybocystites eldonensis (Parks, 1908) as a junior synonym of H. problematicus; (3) although probably assignable to Anomalocrinus Meek and Worthen, 1865, the aberrant crinoid Glaucocrinus falconeri Parks and Alcock, 1912, and its genus Glaucocrinus Parks and Alcock, 1912, are designated as nomena dubia; (4) Iocrinus similis (Billings, 1857) is also designated as a nomen dubium; and (5) Iocrinus subcrassus torontoensis Fritz, 1925 is designated a junior synonym of I. subcrassus Meek and Worthen, 1865.UUID: http://zoobank.org/90f8580b-ed7e-4405-97b2-73c9069de7f5

Most major crinoid clades first appear in the fossil record during the Ordovician, but the evolutionary origins of many higher taxa remain unresolved. Here, the first camerate crinoids from the Kat...

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 sundayaen. sp.,Archaeocrinus maraensisn. sp.,Priscillacrinus elegansn. gen. n. sp.,Cleiocrinus regius, andCleiocrinus lepidotusn. 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.UUID:http://zoobank.org/e3e268a7-88e5-43cd-84ea-b40df45e8281

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 according to 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 Articulata. Following recommendations proposed in recent revisions, we recognize several new clades, including the Eucamerata Cole 2017, Porocrinoidea Wright 2017, and Eucladida Wright 2017. 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. Last, 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.

The subclass Camerata (Crinoidea, Echinodermata) is a major group of Paleozoic crinoids that represents an early divergence in the evolutionary history and morphologic diversification of class Crinoidea, yet phylogenetic relationships among early camerates remain unresolved. This study conducted a series of quantitative phylogenetic analyses using parsimony methods to infer relationships of all well-preserved Ordovician camerate genera (52 taxa), establish the branching sequence of early camerates, and test the monophyly of traditionally recognized higher taxa, including orders Monobathrida and Diplobathrida. The first phylogenetic analysis identified a suitable outroup for rooting the Ordovician camerate tree and assessed affinities of the atypical dicyclic family Reteocrinidae. The second analysis inferred the phylogeny of all well-preserved Ordovician camerate genera. Inferred phylogenies confirm: (1) the Tremadocian genera Cnemecrinus and Eknomocrinus are sister to the Camerata; (2) as historically defined, orders Monobathrida and Diplobathrida do not represent monophyletic groups; (3) with minimal revision, Monobathrida and Diplobathrida can be re-diagnosed to represent monophyletic clades; (4) family Reteocrinidae is more closely related to camerates than to other crinoid groups currently recognized at the subclass level; and (5) several genera in subclass Camerata represent stem taxa that cannot be classified as either true monobathrids or true diplobathrids. The clade containing Monobathrida and Diplobathrida, as recognized herein, is termed Eucamerata to distinguish its constituent taxa from more basally positioned taxa, termed stem eucamerates. The results of this study provide a phylogenetic framework for revising camerate classification, elucidating patterns of morphologic evolution, and informing outgroup selection for future phylogenetic analyses of post-Ordovician camerates.

A diverse crinoid fauna is described from the Upper Ordovician (Katian) Fombuena Formation from the eastern Iberian Chains of Spain. New crinoids include the diplobathrid camerates Fombuenacrinus nodulus n. gen. n. sp., Goyacrinus gutierrezi n. gen. n. sp., Dalicrinus hammanni n. gen. n. sp., and Ambonacrinus decorus n. gen. n. sp.; the monobathrid camerate Eopatelliocrinus hispaniensis n. sp.; and the cladid Picassocrinus villasi n. gen. n. sp. A new occurrence of Heviacrinus melendezi Gil Cid, Domínguez Alonso, and Silván Pobes, 1996 is also documented from the Castillejo Formation (Darriwilian, Middle Ordovician) from the eastern Iberian Chains of Spain. The Fombuena Formation comprises a Gondwanan crinoid assemblage from a high paleolatitude and has the highest crinoid diversity of any currently known Katian Gondwanan fauna. This assemblage is compared to other Katian age faunas around the globe, and its paleobiogeographic implications are discussed., School of Earth Sciences, The Ohio State University, Estados Unidos, Natural History Museum of Denmark, University of Copenhagen, Dinamarca, Unidad de Zaragoza, Instituto Geológico y Minero de España, España, Department of Paleobiology, National Museum of Natural History, Estados Unidos

A period of reduced reefal abundance and size occurred around the time of the Silurian–Devonian boundary, between the middle Silurian and Middle Devonian reef building peaks. In southeastern Laurentia, stromatoporoid and coral reefs became especially rare during this time, and very few buildups have been reported from the region. This paper reports on the sedimentological, faunal, and paleoenvironmental characteristics of a newly discovered latest Silurian stromatoporoid-dominated buildup in the Keyser Limestone of the Virginia Appalachians. The buildup is classified as a parabiostrome, because over 95 % of the stromatoporoids in the buildup have been disturbed. Based on qualitative and statistical comparisons of facies characteristics, the buildup most likely formed from a stromatoporoid-tabulate buildup that was repeatedly damaged by high-energy events. Multivariate analyses of point count data reveal a decrease in stromatoporoids and an increase in tabulate corals and matrix moving vertically upward through the buildup, indicating changes in faunal composition as the buildup grew. The results of this study provide unique insight into reef development in one of the oldest Silurian reefal buildups from the central Appalachian Basin during a time interval when reefal buildups were poorly represented.