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...

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 family Actinocrinitidae was a significant contributor to the global biodiversity peak of crinoids that occurred during the Mississippian and is referred to as the “Age of Crinoids.” Although the actinocrinitids are a major component of that high diversity, they are also a source of much taxonomic confusion. Previously, generic concepts were not applied equally between Europe and North America creating disparity in the definition of genera. In this contribution, all genera are defined objectively by discrete characters, and the generic assignments of all species are reevaluated. Twenty genera are described. A total of 206 species were evaluated of which 56 species and one taxon in open nomenclature are reassigned to different genera, 21 species are designated asnomina dubia, and three species and one genus are nowincertae sedis.A phylogenetic hypothesis is presented for the relationships of the genera of Actinocrinitidae genera based on a parsimony-based analysis and plotted against stratigraphic ranges. Although groupings were revealed in this analysis, the Actinocrinitidae cannot be readily subdivided into subfamilies. Rapid diversification occurred during the Tournaisian following the Hangenberg Extinction of probable fish predators. The late Devonian (Famennian) occurrence of the highly derived generaAbactinocrinusandPhysetocrinussuggests there is a more extensive, but undocumented, evolutionary history for the Actinocrinitidae during the Devonian.

The Nunn Member (early Osagean) of the Lake Valley Formation of New Mexico is known for its abundance and diversity of crinoids. Although crinoids were first reported in the late 1800s, no comprehensive study of the crinoids has been conducted and a complete list of the crinoid taxa does not exist. All subclasses of crinoids occur in the Lake Valley, but the camerates are by far the dominant group. Study of the Macurda collection from the University of Michigan, the Laudon collection from the University of New Mexico, and new collections provided more than 7000 specimens, 4,500 of which were identifiable camerates. Sixty-one species of camerates are recognized in the Nunn Member, including five new species: Blairocrinus macurdai, Iotacrinus novamexicanus, Agaricocrinus alamogordoensis, Uperocrinus kuesi, and Collicrinus laudoni. This camerate fauna is very similar to that of the lower Burlington Limestone of the Mississippi Valley. An update of the crinoid taxa in the Lake Valley Formation allows for a better understanding of the temporal and geographic relationships of crinoid faunas across North American during the Early Mississippian when camerates were at their global diversity maximum. The majority of the camerates come from the western New Mexico outcrops where the Nunn Member is thicker and the marine shelf was shallower, but several also occur in association with the deep-water Waulsortian mounds.

The Actinocrinitidae were among the most abundant crinoids worldwide during the Lower Mississippian. Recent systematic revisions of the family allow a revised genus- and species-level understanding of these crinoids globally and a more precise means by which to understand the temporal and facies distribution of genera and species in this important Mississippian family. Two genera with a total of five species of Actinocrinitidae (and five additional forms left in open nomenclature) are recognized from the Fort Payne Formation, including Actinocrinites jugosus (Hall, 1859), Actinocrinites spp. indeterminate, Thinocrinus gibsoni (Miller and Gurley, 1893), Thinocrinus lowei (Hall, 1858), Thinocrinus probolos (Ausich and Kammer, 1991), Thinocrinus akanthos new species, Thinocrinus sp. aff. T. gibsoni, Thinocrinus spp. indeterminate, and two taxa recognized as only Actinocrinitidae genus and species indeterminate. Actinocrinites tripus Ehlers and Kesling, 1963 is recognized as a junior synonym of Thinocrinus gibsoni. Thinocrinus, rather than Actinocrinites as previously thought, is the dominant Fort Payne Formation actinocrinitid. Fort Payne Formation carbonate buildup facies (wackestone buildups and crinoidal packstone buildups) each have characteristic species of Thinocrinus. Actinocrinites is relatively rare in the Fort Payne Formation, but occurs preferentially in crinoidal packstone buildups.