Atelestocrinus Baumilleri, N. Sp., A New Early Mississippian (Viséan) Crinoid, and Related Pseudomonocyclic Forms

http://deepblue.lib.umich.edu/bitstream/2027.42/172908/5/Contributions Vol 34 No 13.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/172908/6/Contributions Vol 34 No 13 Lo Res.pd

Parasitism and predation on Paleozoic crinoids.

Biotic interactions are widely recognized as agents of evolution, yet the nature, extent, and implications of many such relationships in the fossil record remain elusive. A classic example is the association between Paleozoic crinoids and platyceratid gastropods, characterized by platyceratid attachment over crinoid anal vents. The traditional interpretation for this interaction is that gastropods fed on crinoid excrement without detriment to crinoids. To test this hypothesis, measurements were collected for two Devonian crinoid species. Results indicated that in both species, snail-infested individuals were significantly smaller than uninfested individuals, falsifying the hypothesis that the crinoid-gastropod relationship was strictly commensal. Smaller size of infested crinoids is interpreted as a consequence of nutrient-stealing by gastropods. Moreover, the absence of platyceratids on the largest crinoids suggests that large size may have conferred immunity from permanent infestation. Several workers have suggested that platyceratid parasitism may have driven the evolution of anti-infestation structures such as anal tubes in fossil crinoids. Anal tubes prevented platyceratids from occupying crinoid anal vents, but they did not prevent infestation: gastropods attached to crinoid tegmina and accessed intercalical nutrients via drilling. Nevertheless, a survey of tubed vs. tubeless crinoids demonstrates significantly lower infestation in tubed crinoids. Drilling tubed crinoids likely was less cost-effective than infesting tubed crinoids. Moreover, phylogenetic analysis of the Compsocrinina suggests that tubes evolved repeatedly in platyceratid-infested clades, failing to reject the hypothesis that tubes evolved in response to platyceratid parasitism. Predation, another purported force of evolutionary change, was studied in a Mississippian LagerstAtten (Le Grand) using arm regeneration frequency. Nine percent of the crinoids contained at least one regenerating arm, with 27% regeneration observed in the most abundant species, Rhodocrinites kirbyi, a significantly higher frequency than observed in other species. Rhodocrinites kirbyi had the longest stalks, and individuals above median cup height (7 mm) displayed nearly 50% regeneration, whereas smaller individuals had only 2% regeneration. These patterns are consistent with a predator that attacks the most apparent prey. Regeneration frequency in fossil crinoids potentially provides a valuable, yet overlooked data source for testing hypotheses pertinent to the role of predation in the evolution of Phanerozoic marine life.Ph.D.Earth SciencesPaleoecologyPaleontologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/124406/2/3138153.pd

Taphonomy as an Indicator of Behavior Among Fossil Crinoids

The dominant faunal elements in shallow Paleozoic oceans, echinoderms are important to understanding these marine ecosystems. Echinoderms (which include such animals as sea stars, crinoids or sea lilies, sea urchins, sand dollars, and sea cucumbers) have left a rich and, for science, extremely useful fossil record. For various reasons, they provide the ideal source for answers to the questions that will help us develop a more complete understanding of global environmental and biodiversity changes. This volume highlights the modern study of fossil echinoderms and is organized into five parts: echinoderm paleoecology, functional morphology, and paleoecology; evolutionary paleoecology; morphology for refined phylogenetic studies; innovative applications of data encoded in echinoderms; and information on new crinoid data sets.https://nsuworks.nova.edu/occ_facbooks/1016/thumbnail.jp

Data from: Predation on feather stars by regular echinoids as evidenced by laboratory and field observations and its paleobiological implications

Among extant crinoids, the feather stars are the most diverse and occupy the greatest bathymetric range, being especially common in reef environments. Feather stars possess a variety of morphological, behavioral and physiological traits that have been hypothesized to be critical to their success, especially in their ability to cope with predation. However, knowledge of their predators is exceptionally scant, consisting primarily of circumstantial evidence of attacks by fishes. In this study the question whether regular echinoids, recently shown to consume stalked crinoids, also consume feather stars is explored. Aquarium observations indicate that regular echinoids find feather stars palatable, including feather stars known to be distasteful to fish, and that regular echinoids can capture and eat live feather stars, including those known to swim. Gut-content analyses of the echinoid Araeosoma fenestratum (Thomson, 1872), which is commonly observed with large populations of the feather star Koehlermetra porrecta (Carpenter, 1888) in video transects from marine canyons off the coast of France, revealed elements of feather stars in the guts of 6 of 13 individuals. The high proportion of crinoid material (up to 90%), and the presence of articulated crinoid skeletal elements in the gut of A. fenestratum, suggest that these echinoids consumed at least some live crinoids, although they may have also ingested some postmortem remains found in the sediment. Additionally, photographic evidence from the northeast Atlantic suggests that another regular echinoid, Cidaris cidaris (Linnaeus, 1758), preys on feather stars. Thus in spite of the broad suite of antipredatory adaptations, feather stars are today subject to predation by regular echinoids and may have been since the Mesozoic, when this group of crinoids first appeared

Data from: Spinosity, regeneration, and targeting among Paleozoic crinoids and their predators

Evolving interactions between predators and prey constitute one of the major adaptive influences on marine animals during the Paleozoic. Crinoids and fish constitute a predator-prey system that may date back to at least the Silurian, as suggested by patterns of crinoid regeneration and spinosity in concert with changes in the predatory fauna. Here we present data on the frequency of breakage and regeneration in the spines of the Middle Devonian camerate Gennaeocrinus and Late Paleozoic cladids, as well as an expanded survey of the prevalence of spinosity and infestation by platyceratid gastropods on crinoid genera during the Paleozoic. Spine regeneration frequency in the measured populations is comparable to arm regeneration frequencies from Mississippian Rhodocrinites and from modern deep-water crinoid populations. The prevalence of spinosity varies by taxon, time, and anatomy among Paleozoic crinoids; notably, spinosity in camerates increased from the Silurian through the Mississippian and decreased sharply during the Pennsylvanian, whereas spines were uncommon in cladids until their late Mississippian diversification. Among camerates, tegmen spinosity is positively correlated with the presence of infesting platyceratids. These results allow us to evaluate several hypotheses for the effects of predation on morphological differences between early, middle, and late Paleozoic crinoid faunas. Our data corroborate the hypothesis that predators targeted epibionts on camerate crinoids and anal sacs on advanced cladids, and suggest that the replacement of shearing predators by crushing predators after the Hangenberg extinction affected the locations of spines in Mississippian camerates

Post-Paleozoic crinoid radiation in response to benthic predation preceded the Mesozoic marine revolution

It has been argued that increases in predation over geological time should result in increases in defensive adaptations in prey taxa. Recent in situ and laboratory observations indicate that cidaroid sea urchins feed on live stalked crinoids, leaving distinct bite marks on their skeletal elements. Similar bite marks on fossil crinoids from Poland strongly suggest that these animals have been subject to echinoid predation since the Triassic. Following their near-demise during the end-Permian extinction, crinoids underwent a major evolutionary radiation during the Middle–Late Triassic that produced distinct morphological and behavioral novelties, particularly motile taxa that contrasted strongly with the predominantly sessile Paleozoic crinoid faunas. We suggest that the appearance and subsequent evolutionary success of motile crinoids were related to benthic predation by post-Paleozoic echinoids with their stronger and more active feeding apparatus and that, in the case of crinoids, the predation-driven Mesozoic marine revolution started earlier than in other groups, perhaps soon after the end-Permian extinction