Hybocrinid and disparid crinoids from the Middle Ordovician (Galena Group, Dunleith Formation) of northern Iowa and southern Minnesota

Four hybocrinid and disparid crinoids from the Middle Ordovician Dunleith Formation (Galena Group) of northern Iowa and southern Minnesota are described: Hybocrinus conicus Billings, Ohiocrinus levorsoni n. sp., Caleidocrinus (Huxleyocrinus) gerki n. sp., and Ectenocrinus simplex (Hall). The first three taxa are rare. Ectenocrinus simplex is an abundant and protean form ranging from the Shermanian to the Maysville and from the Appalachians to the Midcontinent. One Middle Ordovician specimen from the Dunleith is a complete small adult with stem and a lichenocrinid holdfast. The column was largely upright with the crown located about 25 cm above the seafloor. The Middle Ordovician crinoids differ somewhat from the later Cincinnatian material where only young E. simplex exhibit lichenocrinid holdfasts. Older crinoids became detached and were eleutherozoic well before the column was 25 cm long. Thus, the Cincinnatian individuals lost the attachment device earlier during ontogeny than their ancestors in the Middle Ordovician. Unlike most associated crinoids, E. simplex formed a roughly conical filtration net. The arms of E. simplex are extensively branched. Ten main arms bear unbranched ramules on alternate brachials, and the arm structure converges on the pinnulate pattern. Narrow food grooves and short covering plates are present. Analogies with living crinoids indicate that small food particles were caught by small and close-spaced tube-feet. The formation of new plates and ramules at the arm tips increases the size of the food-gathering system throughout ontogeny. The food-gathering capacity comprises the number of food-catching tube-feet times the width of the food grooves, and it measures the number and size of food particles that can be caught. Both size and capacity of the food-gathering system are positively allometric compared to crown volume and the amount of tissue that must be nourished. This is mainly caused by the addition of new ramules at the arm tips, which generates an exponentially increasing plate supply rate. Examination of numerous specimens from various geographic and stratigraphic horizons with multivariate statistics shows that the species was homogeneous throughout its range aside from the differences in living habits mentioned above.

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Eoparisocrinid crinoids from the Middle Ordovician (Galena Group) of northern Iowa and southern Minnesota

Journal of Paleontology ◽

10.1017/s0022336000034673 ◽

1995 ◽

Vol 69 (2) ◽

pp. 351-366 ◽

Cited By ~ 21

Author(s):

James C. Brower

Keyword(s):

Growth Rates ◽

Growth Curves ◽

Groove Width ◽

Stem Length ◽

Middle Ordovician ◽

Crown Volume ◽

Food Particles ◽

Food Groove ◽

Branch Density ◽

Tube Feet

Two species of eoparisocrinid crinoids from the Middle Ordovician Galena Group of northern Iowa and southern Minnesota are described, namely Eoparisocrinus crossmani n. sp. and E. grandei n. sp. The post-larval development of Eoparisocrinus crossmani is examined. Crinoid arms grow by addition of new plates at their distal tips in conjunction with calcite deposition on old plates. New branches appear where axillary plates are initiated. Consequently, the growth rates for number of brachials and length of food-gathering system compared to crown volume are much faster than if the animals were isometric. The number of food particles collected is related to the number of food-catching tube-feet, which can be estimated if the length of the arms and height of the covering plates are known. The size of the largest food item is constrained by the food groove width. Thus, food-gathering capacity is the number of food-catching tube-feet multiplied by food groove width. The food-gathering capacity increases more rapidly than if the animal grew isometrically, and the ratio of food-gathering capacity: crown volume only declines slightly over the known growth range. All Ordovician cladid crinoids examined follow nearly identical ontogenetic trajectories. The ecological niche of a stalked crinoid is related to four basic parameters: stem length, food groove width, tube-foot spacing, and branch density. Stem length limits the highest elevation above the seafloor. The column of E. crossmani becomes longer during ontogeny due to the formation of new columnals and height growth of old ones. Consequently, individuals gradually “move up” until the adult elevation of about 50 mm is reached. The growth rates of stem length relative to crown size are slow in the youngest and mature animals but rapid in juveniles. The food grooves become wider throughout growth so that older crinoids ate larger food particles than younger ones. The food groove width increases less rapidly than if the shape were constant, because distal plates and branches are more narrow and have more slender food grooves than proximal plates. Growth curves for food groove width versus stem length and elevation were generated for E. crossmani and other crinoids that commonly occur in the same beds. Together, elevation and food particle size define the main dimensions of the niche. The various taxa are more or less separated by different food groove widths at most comparable elevations. This pattern minimizes ecological overlap and probably competition between the different species. The tube-foot spacing of E. crossmani is constant regardless of size, which suggests that it employed the same type of feeding mechanism throughout post-larval ontogeny. The arm branches of adults gradually become less densely spaced relative to the area of water filtered than in juveniles.

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Camerate crinoids from the Middle Ordovician (Galena Group, Dunleith Formation) of northern Iowa and southern Minnesota

Journal of Paleontology ◽

10.1017/s0022336000025932 ◽

1994 ◽

Vol 68 (3) ◽

pp. 570-599 ◽

Cited By ~ 30

Author(s):

James C. Brower

Keyword(s):

New York ◽

Root Morphology ◽

Stem Length ◽

Middle Ordovician ◽

Developmental Trends ◽

Crown Volume ◽

Substrate Level ◽

Food Particles ◽

Tube Feet

Five species of camerate crinoids from the Middle Ordovician Dunleith Formation (Galena Group) of northern Iowa and southern Minnesota are described:Cleiocrinus regiusBillings,Cotylacrinna sandran. gen. and n. sp.,Euptychocrinus skopaiosn. gen. and n. sp.,Abludoglyptocrinus charltoni(Kolata), andEopatelliocrinus ornatus(Billings) n. comb.Archaeocrinus desideratusBillings is assigned toCotylacrinna, andGlyptocrinus fimbriatusShumard andPtychocrinus longibrachialisBrower are placed inEuptychocrinus.The geographical affinities of the Iowa and Minnesota crinoids lie with adjacent localities in the northern midcontinent and the Appalachian province of Canada and New York. Preservation of various specimens implies thatEuptychocrinus skopaios, Abludoglyptocrinus charltoni, andEopatelliocrinus ornatusutilized parabolic arm fans.Cotylacrinna sandrais a specialized rhodocrinitid which is perhaps the largest completely known Ordovician crinoid with a stem length of over 91 cm and a total volume of about 45,740 mm3. The root morphology indicates an upright column and this animal towered above the associated echinoderms, which ranged from the substrate level to a maximum of 25 cm above the seafloor.Euptychocrinus skopaiosis marked by dwarfed morphology compared to the closely alliedE. fimbriatus, and it exhibits accelerated development of fixed brachs, number of brachials in and length of the arms, and closely spaced pinnules. The dwarfism is interpreted as a specialization for small size and adults ofE. skopaioswere only located about five or six cm above the substrate. New brachials and pinnules form at the distal arm tips ofE. skopaiosthroughout ontogeny. Consequently, the length of and the number of plates in the food-gathering system are positively allometric relative to the crown volume. Food gathering capacity equals the number of food-catching tube feet times width of the food grooves and it is also augmented more rapidly than expected for an isometric crinoid. Although distantly related to euptychocrinids, most other Dunleith camerates, namelyAbludoglyptocrinus charltoni, Eopatelliocrinus ornatus, andCotylacrinna sandra, follow the same developmental trends of the food-gathering system observed inEuptychocrinus skopaios.Comparison of the pinnulate camerates and three species of ramulate cladids and a disparid from the Dunleith reveals some striking contrasts. At equivalent crown volumes, the camerates are characterized by more numerous arm branches in the form of pinnules, more narrow food grooves, more closely spaced tube feet, and longer food-gathering systems with more plates and greater capacity. The Dunleith camerates were adapted for catching smaller food particles using more numerous and more closely spaced tube feet located on more extensively branched filtration nets than the associated cladids and disparid. The differences can be attributed to taxonomy and presumably phylogeny, that is camerates versus cladids and disparids, and/or morphology in the presence of pinnules versus ramules.

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Cupulocrinid crinoids from the Middle Ordovician (Galena Group, Dunleith Formation) of northern Iowa and southern Minnesota

Journal of Paleontology ◽

10.1017/s0022336000033515 ◽

1992 ◽

Vol 66 (1) ◽

pp. 99-128 ◽

Cited By ~ 32

Author(s):

James C. Brower

Keyword(s):

Niche Differentiation ◽

Upper Ordovician ◽

Average Width ◽

Positive Allometry ◽

Middle Ordovician ◽

Surrogate Variable ◽

Crown Volume ◽

Food Particles ◽

Anal Sac ◽

Food Groove

Two cupulocrinids,Cupulocrinus crossmanin. sp. andPraecupulocrinus conjugans(Billings) n. gen., are known from the Middle Ordovician (Galena Group, Dunleith Formation) of northern Iowa and southern Minnesota. Various morphologic and ontogenetic features demonstrate thatPraecupulocrinusis more primitive thanCupulocrinus. The two species commonly occur together. In addition, both taxa coexisted at similar levels with stem lengths ranging from about 1.5 cm in juveniles to 15 cm in adults. Relatively complete growth sequences illustrate growth and variation and show how two related crinoids subdivided feeding niches. The crown volume provides a satisfactory surrogate variable for the size of the animal. The food-gathering system of the cupulocrinids is mainly augmented by the addition of new plates at the ends of the arms. The number of plates in the arms and the arm length exhibit positive allometry relative to crown volume, largely due to development of new branches at the arm tips. The food-gathering capacity equals the number of food-catching tube-feet multiplied by the average width of the food grooves. Food-gathering capacity is also positively allometric with respect to crown volume and the amount of tissue that must be supplied with food. Consequently, the ratio of food-gathering capacity:crown volume is either constant or declines slightly with increasing size and age. The food groove width increases throughout ontogeny so adult crinoids ate larger food particles than juveniles.Praecupulocrinus conjugans(Billings) n. gen. has more narrow food grooves thanCupulocrinus crossmanin. sp. of comparable size and age, which suggests niche differentiation based on food-particle size. The arm and tube-foot geometry indicates that both cupulocrinids utilized the same type of suspension feeding.The morphology of the anal sac and the lack of “patelloid” processes in the arms indicate thatCupulocrinus sepulchrumRamsbottom from the Upper Ordovician of Scotland belongs toDendrocrinus.

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Ontogeny and functional morphology of Eoparisocrinus crossmani, a cladid crinoid from the Middle Ordovician

The Paleontological Society Special Publications ◽

10.1017/s2475262200005992 ◽

1992 ◽

Vol 6 ◽

pp. 39-39

Author(s):

James C. Brower

Keyword(s):

Functional Morphology ◽

Growth Rates ◽

Feeding Habits ◽

Groove Width ◽

Stem Length ◽

Food Particle ◽

Crown Volume ◽

Food Particles ◽

Food Groove ◽

Tube Feet

A post-larval development sequence of complete specimens of Eoparisocrinus crossmani provides a unique opportunity to examine growth and functional morphology. Food particles are caught by the tube-feet in the arms which must provide enough material to nourish a volume of tissue. Tissue volume is assumed to be proportional to crown volume. Ignoring the stem is justified inasmuch as most soft parts are housed in the crown. Crinoid arms grow by terminal addition of new plates at their distal tips in conjunction with calcite deposition on old plates. New branches appear where axillary plates are initiated. Consequently, the growth rates for number of brachials and length of food-gathering system compared to crown volume are much faster than if the data were isometric. The number of food particles collected is related to the number of food-catching tube-feet which can be estimated if the length of the arms and height of the covering plates are known. The size of the largest food item is constrained by the food groove width. Thus, food-gathering capacity is defined as the number of food-catching tube-feet multiplied by food groove width. Food-gathering capacity is the product of two linear dimensions so the expected exponent for food-gathering capacity and crown volume comprises 0.67. The computed exponent is significantly larger than the isometric value so the food-gathering capacity increases much more rapidly than if E. crossmani retained the same shape at all ages, and the ratio of food-gathering capacity:crown volume only declines slightly over the known growth range. Student's t tests indicate that all Ordovician inadunate crinoids examined follow nearly identical ontogenetic trajectories. Conversely, Ordovician camerates are characterized by larger food gathering capacities at equivalent crown volumes. This suggests that the feeding habits of Ordovician inadunates and camerates were quite different.The ecological niche of a stalked crinoid is at least partially categorized by three parameters. Stem length limits the highest elevation above the seafloor. The column of E. crossmani becomes longer during ontogeny due to the formation of new columnals and height growth of old ones. Consequently, individuals gradually “move up” through various levels until the adult elevation of about 50 mm is reached. The growth rates of stem length relative to crown size are slow in the youngest and mature animals but quite rapid in juveniles. The food groove width defines the size of the largest food particle that can be trapped and transported down the arms to the mouth. The exponents for the average food groove width versus cup height or crown volume are slightly less than the corresponding isometric values. The food groove width is augmented less rapidly than if the shape were constant, because distal plates and branches are more narrow and have more slender food grooves than proximal plates. Growth curves for food groove width versus stem length and elevation were generated for E. crossmani and its common associates. Together, elevation and food particle size define the main dimensions of the niche. The various taxa are more or less separated by different food groove widths at most comparable elevations with two exceptions. One deals with adults of Eoparisocrinus crossmani and juveniles of Cupulocrinus crossmani which sometimes occur together. This overlap would have been of short duration if the juveniles were growing rapidly. The youngest crinoids of all species probably intergraded. This pattern minimizes ecological overlap and probably competition between the different species. Tube-foot spacing is correlated with feeding habits and environment. The tube-foot spacing of E. crossmani is constant regardless of size which suggests that it employed the same type of feeding mechanism throughout post-larval ontogeny.

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The Histology and Activities of the Tube-Feet of Antedon Bifida

Journal of Cell Science ◽

10.1242/jcs.s3-101.54.105 ◽

1960 ◽

Vol s3-101 (54) ◽

pp. 105-117

Author(s):

DAVID NICHOLS

Keyword(s):

Hydrostatic Pressure ◽

Basic Structure ◽

Vascular Canal ◽

Food Particles ◽

Tube Feet

The histology of the tube-feet and adjacent parts of the water-vascular canal of the crinoid Antedon bifida is described. The tube-feet possess the same basic structure as other, better-known tube-feet; here, however, they are adapted to collect food particles. They shoot out mucus by means of special muscle-operated glands and bend rapidly inwards to waft the mucus with entrapped particles into the food-grooves. The protraction of the tube-feet is probably brought about by a mechanism very similar to the ampulla system, of other extensile tube-feet, but here the contraction of restricted portions of the water-vascular canal provides the necessary hydrostatic pressure.

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The application of filtration theory to food gathering in Ordovician crinoids

Journal of Paleontology ◽

10.1666/05-034.1 ◽

2007 ◽

Vol 81 (6) ◽

pp. 1284-1300 ◽

Cited By ~ 13

Author(s):

James C. Brower

Keyword(s):

Behavioral Changes ◽

Filtration Theory ◽

Upper Ordovician ◽

Nutrient Contents ◽

Particle Distributions ◽

Wide Range ◽

Ecological Patterns ◽

Food Particles ◽

Mean Size ◽

Tube Feet

Food gathering of some adult Upper Ordovician crinoids was modeled by means of filtration theory. The arm-branching patterns of the 13 species examined range from nonpinnulate isotomous arms to uniserial and biserial arms with numerous pinnules. Most taxa are roughly equivalent with respect to ambient current velocities and the nutrient contents needed from seawater. Two species with extensively branched arms have markedly higher nutritional requirements at any one ambient current velocity. The results are somewhat correlated with environment in the form of differential current velocities, water flow patterns, and food abundance and composition. The data are generally compatible with filtration theory and the environmental distributions of many Ordovician and other Paleozoic crinoids, and they reveal that Upper Ordovician crinoids had at least partially developed the ecological patterns seen in later Paleozoic crinoids. Various morphological, physiological, and behavioral changes can be employed by crinoids to alter their nutritional balance. The size distributions of food particles that are caught by the crinoids are modeled. These food particle distributions for the Ordovician fossils resemble those of modern crinoids. Relative to the population of food items, the distributions of particles that are trapped are shifted towards larger items because the crinoid filtration nets are more efficient at catching larger particles. Crinoids with relatively open filtration nets and large food-catching tube feet are generalized and feed on a wide range of food particles of a relatively large mean size. The more specialized taxa with extensively branched arms bearing small and closely packed food-catching tube feet are restricted to a more narrow range of smaller food particles.

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An edrioasteroid from the Silurian Herefordshire Lagerstätte of England reveals the nature of the water vascular system in an extinct echinoderm

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2017.1189 ◽

2017 ◽

Vol 284 (1862) ◽

pp. 20171189 ◽

Cited By ~ 5

Author(s):

Derek E. G. Briggs ◽

Derek J. Siveter ◽

David J. Siveter ◽

Mark D. Sutton ◽

Imran A. Rahman

Keyword(s):

New Genus ◽

Vascular System ◽

Evolutionary Development ◽

New Genus And Species ◽

Inner Surface ◽

Food Particles ◽

Oral Surface ◽

Extinct Group ◽

Oral Area ◽

Tube Feet

Echinoderms are unique in having a water vascular system with tube feet, which perform a variety of functions in living forms. Here, we report the first example of preserved tube feet in an extinct group of echinoderms. The material, from the Silurian Herefordshire Lagerstätte, UK, is assigned to a new genus and species of rhenopyrgid edrioasteroid, Heropyrgus disterminus . The tube feet attach to the inner surface of compound interradial plates and form two sets, an upper and a lower, an arrangement never reported previously in an extant or extinct echinoderm. Cover plates are absent and floor plates are separated creating a large permanent entrance to the interior of the oral area. The tube feet may have captured food particles that entered the oral area and/or enhanced respiration. The pentameral symmetry of the oral surface transitions to eight columns in which the plates are vertically offset resulting in a spiral appearance. This change in symmetry may reflect flexibility in the evolutionary development of the axial and extraxial zones in early echinoderm evolution.

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