Abstract.-Knowledge of phylogenetic relationships among species is fundamental to understanding basic patterns in evolution and underpins nearly all research programs in biology and paleontology. However, most methods of phylogenetic inference typically used by paleontologists do not accommodate the idiosyncrasies of fossil data and therefore do not take full advantage of the information provided by the fossil record. The advent of Bayesian 'tip-dating' approaches to phylogeny estimation is especially promising for paleosystematists because time-stamped comparative data can be combined with probabilistic models tailored to accommodate the study of fossil taxa. Under a Bayesian framework, the recently developed fossilized birth-death (FBD) process provides a more realistic tree prior model for paleontological data that accounts for macroevolutionary dynamics, preservation, and sampling when inferring phylogenetic trees containing fossils. In addition, the FBD tree prior allows for the possibility of sampling ancestral morphotaxa. Although paleontologists are increasingly embracing probabilistic phylogenetic methods, these recent developments have not previously been applied to the deep-time invertebrate fossil record. Here, I examine phylogenetic relationships among Ordovician through Devonian crinoids using a Bayesian tip-dating approach. Results support several clades recognized in previous analyses sampling only Ordovician taxa, but also reveal instances where phylogenetic affinities are more complex and extensive revisions are necessary, particularly among the Cladida. The name Porocrinoidea is proposed for a well-supported clade of Ordovician 'cyathocrine' cladids and hybocrinids. The Eucladida is proposed as a clade name for the sister group of the Flexibilia herein comprised of cladids variously considered 'cyathocrines,' 'dendrocrines,' and/or 'poteriocrines' by other authors.

Phylogenetic relationships among early crinoids are evaluated by maximizing parsimonious-informative characters that are unordered and unweighted. Primarily Tremadocian-Darriwilian (Early-Middle Ordovician) taxa are analysed. Stratigraphic congruence metrics support the best phylogenetic hypothesis derived using parsimony methods. This study confirms the traditionally recognized lineages of Palaeozoic crinoids and provides new information on the branching order of evolving lineages. Camerates are basal crinoids with progressively more tipward groups (from an Ordovician perspective) being protocrinoids, cladids (paraphyletic), hybocrinids and disparids. The Protocrinoida should be maintained, but the Aethocrinida should be placed within the Cladida. The results of this study identify phylogenetic structure amongst the major early crinoid lineages and delineate the relative positions of crinoid higher taxa along a tree. Each valid higher taxon discussed herein requires a comprehensive treatment to delimit within-lineage phylogenetic relationships.Key words: Echinodermata, Ordovician, phylogenetic methods, stratigraphic congruence.C R I N O I D S are regarded as the most primitive of the five living echinoderm classes (asteroids, crinoids, echinoids, holothurians and ophiuroids), but the phylogenetic position of crinoids amongst Palaeozoic echinoderms has been widely debated. The oldest known crinoids are from the early Tremadocian (Ordovician) (Guensburg and Sprinkle 2001, 2003, 2009 Guensburg 2010); and as part of the Great Ordovician Biodiversification Event (GOBE), they diversified to become the dominant stalked echinoderm clade by the early Late Ordovician (Sandbian). Crinoids became progressively more dominant amongst stalked echinoderms in most marine settings through the remainder of the Palaeozoic and were instrumental in establishment of the structure of Palaeozoic epifaunal suspension-feeding communities (Ausich and Bottjer 1982; Bottjer and Ausich 1987).However, a consensus has been difficult to reach concerning the phylogenetic position of crinoids amongst Ordovician clades and the early diversification of the Crinoidea. At the heart of this issue is a fundamental question of echinoderm phylogeny as a whole. Are stalked echinoderms a clade or a grade of echinoderm evolution? In this contribution, we adopt results from echinoderm universal elemental homology studies that have demonstrated that crinoids are nested within clades of other stalked echinoderms (Sumrall 2008(Sumrall , 2010 Sumrall and Waters 2012; Kammer et al. 2013; Sumrall 2014). With stalked echinoderms, including crinoids, recognized as a clade (the Pelmatozoa Leuckart, 1848), phylogenetic relationships of early crinoid evolution are examined.Various hypotheses for the origin and early evolution of crinoids have relied on the supposition that specific characters had special significance in identifying ancestordescendant relationships (e.g. ambulacral floor plates or lintels), that a priori interpretations of morphological tr...

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.

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.

No abstract

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 contribute to understanding patterns of phylogenetic relatedness and testing macroevolutionary hypotheses. Finally our new analysis raises interesting questions about how incorporating age information is expected to affect a phylogeny, and provides a framework for future systematic and macroevolutionary studies of cinctan echinoderms.

No abstract

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