Crinoidea

The site of Bou Nemrou, in the Western Tafilalt (eastern Anti-Atlas, Morocco) is one
of the very few Konservat-Lagerstätten known so far in the world to have yielded
numerous remains of Late Ordovician softbodied fossils associated with an abundant and diverse marine benthic fauna. This locality has also yielded several levels (starfish beds) extremely rich in exquisitely preserved echinoderms. Their remarkable preservation possibly results from the rapid, in situ burial of large, particularly dense, living communities (echinoderm meadows) by storm deposits. The Bou Nemrou starfish beds are dominated by eocrinoids and stylophorans, associated with crinoids, cyclocystoids, edrioasteroids, and ophiuroids. This composition is typical of the cool assemblages of the Mediterranean Province. The Bou Nemrou starfish beds may result from the opportunistic colonisation of the sea-floor by dense populations of echinoderms, during short phases of environmental disturbance.

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.

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 end−Permian mass extinction constituted a major event in the history of crinoids. It led to the demise of the major Paleozoic crinoid groups including cladids, disparids, flexibles and camerates. It is widely accepted that a single lineage, derived from a late Paleozoic cladid ancestor (Ampelocrinidae), survived this mass extinction. Holocrinid crinoids (Holocrinus, Holocrinida) along with recently described genus Baudicrinus (Encrinida), the only crinoid groups known from the Early Triassic, are considered the stem groups for the post−Paleozoic monophyletic subclass Articulata. Here, we report preliminary data on unexpectedly diverse crinoid faunas comprising at least four orders from the Lower Triassic (Induan and Olenekian) of Svalbard, extending their stratigraphic ranges deeper into the early Mesozoic. These findings strongly imply that the recovery of crinoids in the aftermath of the end−Permian extinction began much earlier at higher palaeolatitudes than in the central Tethys.

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 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.

The cyrtocrinids are a group of mostly Mesozoic articulated crinoids, with rare Cenozoic forms and only two extant taxa. A careful analysis of previous studies indicates that the systematic arrangement of cyrtocrinids is very weak and unsatisfactory for several reasons. In particular, most of the original descriptions and diagnosis date from the past century and are logically influenced by a classical typological philosophy. Not being based on phylogeny, the currently accepted groups for cyrtocrinids must be putatively regarded as " artificial ". In addition, an inappropriate use of characters has been used, typically considered as diagnostic in other groups of crinoids but only marginally applicable to cyrtocrinids (the latter differently characterized for several highly distinctive and autapomorphic characters). In order to mitigate these problems and to arrive at the definition of characters and clades based on unambiguous synapomorphies, we present in this paper a preliminary and exploratory phylogenetic analysis based on parsimony of cyrtocrinids. The obtained topology showed how the traditionally recognized groups prove to be highly paraphyletic and polyphyletic, indicating the need for a complete revision of cyrtocrinids taxonomy, based on phylogeny. The gap-weighting method used for codifying morphometric continuous character, has proved to be a powerful tool to obtain well-resolved and consistent cladograms, even with a limited number of characters.

Kimmeridgian (Upper Jurassic) crinoids from southern Poland (5 localities) are described and referred to the following taxa: Isocrinus sp., Isocrinus cingulatus, Isocrinus pendulus, Balanocrinus pentagonalis, Balanocrinus subteres, Millericrinina fam. et sp. indet., Comatulida gen. et. sp. indet., and Palaeocomaster cf. karsensis. Balanocrinids have been recorded from the Kimmeridgian epicratonic succession of central Poland for the first time. Skeletal remains comprise mainly isolated ossicles (columnals, cirrals and brachials) although comatulid thecae are also present. Amongst this material isocrinids and comatulids are dominant while
millericrinids are a minor component. These crinoids lived in shallow-water environments in various ecological
niches. Stalked forms were confined either to hard or firm bottoms (millericrinids and isocrinids). This fauna is
almost identical to the shallow-water Tithonian assemblage from the epicratonic succession of central Poland. It
is, however, very different from the deeper-water Oxfordian assemblage of southern Poland, where cyrtocrinids
dominated, and isocrinids and millericrinids were rare.

—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 cyrtocrinids are a group of mostly Mesozoic articulated crinoids, with rare Cenozoic forms and only two extant taxa. A careful analysis of previous studies indicates that the systematic arrangement of cyrtocrinids is very weak and unsatisfactory for several reasons. In particular, most of the original descriptions and diagnosis date from the past century and are logically influenced by a classical typological philosophy. Not being based on phylogeny, the currently accepted groups for cyrtocrinids must be putatively regarded as “artificial”. In addition, an inappropriate use of characters has been used, typically considered as diagnostic in other groups of crinoids but only marginally applicable to cyrtocrinids (the latter differently characterized for several highly distinctive and autapomorphic characters). In order to mitigate these problems and to arrive at the definition of characters and clades based on unambiguous synapomorphies, we present in this paper a preliminary and ...

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.