Breaking the mold: using biomechanical experiments to assess the life orientation of dorsibiconvex brachiopods

Paleobiology ◽  
2015 ◽  
Vol 41 (1) ◽  
pp. 122-133 ◽  
Author(s):  
Kristina M. Barclay ◽  
Chris L. Schneider ◽  
Lindsey R. Leighton
Keyword(s):  
Calcium Carbonate ◽  
North America ◽  
Specific Gravity ◽  
Hydrodynamic Stability ◽  
Anterior Commissure ◽  
High Energy ◽  
Late Devonian ◽  
Ventral Valve ◽  
Life Orientation ◽  
Stable Orientation

AbstractUnderstanding the life orientation of fossil organisms, such as brachiopods, is not only important for understanding the biology of the organism in question, but it also can be used to interpret paleoecological information about the assemblages from which the specimens were derived. The dorsibiconvex brachiopod morphology is particularly common, especially among the Order Atrypida, yet there have been few independent, biomechanical studies to assess the life orientation of these brachiopods. In this study, we assess potential orientations of two end-member morphologies of a dorsibiconvex brachiopod, Pseudoatrypa lineata, from the Mid–Late Devonian of North America by placing realistic models in a flume.Using materials with the specific gravity of calcium carbonate, we modeled two well-preserved Pseudoatrypa lineata from the Waterways Formation (Givetian–Frasnian, Alberta, Canada) to represent the original shell. The hydrodynamic stability of the models was assessed by placing the models in a recirculating flume in one of three initial orientations: (1) anterior commissure upstream, (2) umbo upstream, and (3) lateral (specimen perpendicular to flow), each with the dorsal and ventral valve topmost. The entire process was conducted both on a Plexiglas substrate and on well-sorted, mediumgrained sand. All scenarios were repeated five times for a total of sixty trials per specimen (120 total).Flume trials indicate that neither brachiopod had a true hydrodynamically stable orientation.Reorientations occurred at low velocities (~0.2 m/s), with transport occurring soon after (~0.3 m/s).Assuming that a juvenile, pedunculate, dorsibiconvex brachiopod would initially have been oriented with its ventral valve topmost, our results suggest two outcomes: the brachiopods either (1) were attached via pedicles throughout their lives or (2) lived in quiet, undisturbed waters. Given the abundance of dorsibiconvex brachiopods in observed high-energy environments, our results indicate it is more conservative to assume dorsibiconvex brachiopods retained pedicles throughout their lives.

The life orientation of concavo-convex brachiopods: overturning the paradigm

Paleobiology ◽  
1995 ◽  
Vol 21 (4) ◽  
pp. 520-551 ◽  
Author(s):  
Halard L. Lescinsky
Keyword(s):  
Hydrodynamic Stability ◽  
A Priori ◽  
Mantle Cavity ◽  
Growth Patterns ◽  
Functional Interpretation ◽  
Life Orientation ◽  
Internal Surfaces ◽  
Stable Orientation

Concavo-convex brachiopods are generally assumed to have lived with their convex valves against the sediment. This orientation is based primarily on the a priori assumption that the upturned commissure would prevent fouling of the brachiopods' mantle cavity. Here, I present epibiontic and taphonomic evidence from orthids and nonproductid strophomenids that concavo-convex brachiopods lived in the reverse life orientation, with the convex valve on top.Ten testable epibiontic and taphonomic criteria are proposed to establish the uppermost valve during encrustation and whether epibionts encrusted primarily live or dead hosts. The criteria are evaluated for 11 collections of Ordovician and Devonian nonproductid concavo-convex brachiopods that contain a total of over 500 brachiopods and 4000 epibionts. In all cases, the results support a convex-up orientation and the encrustation of live hosts. Five criteria concern epibiont growth patterns and show that (1) epibionts predominate on convex valves, (2) epibionts are not restricted to shell margins, (3) distinct exposed and cryptic faunas, as predicted theoretically and described in previous studies, exist on convex and concave valves respectively, (4) epibiont colonies were often truncated by the commissures and hinges of live hosts, and (5) growth patterns of some epibionts indicate live hosts. Five taphonomic criteria show that (1) concavo-convex shells have greater epibiont cover than other morphologies, (2) internal surfaces of disarticulated specimens are rarely encrusted, (3) interiors of articulated specimens are rarely mud-filled, (4) standard taphofacies indicators suggest little postmortem exposure, and (5) sedimentological reconstructions suggest rapid burial.Convex-up brachiopods suggest that the Paleozoic mud bottoms they lived on were probably firmer than usually assumed and that a more complex functional interpretation of concavo-convexity is required. Hydrodynamic stability was important to many concavo-convex, plano-convex, and unequally bi-convex brachiopods. Brachiopods with these morphologies probably lived in the more stable orientation on their concave or flat valve. Productid brachiopods, although also concavo-convex, lived convex valve down and are ecologically distinct from earlier concavo-convex taxa. Productids were anchored, semi-infaunally, by spines and were more similar to Mesozoic oysters in orientation and shell function.

A Lower Jurassic heteroporid bryozoan and associated biota, Turnagain Lake, British Columbia

1981 ◽  
Vol 18 (3) ◽  
pp. 457-468 ◽  
Author(s):  
C. M. Henderson ◽  
D. G. Perry
Keyword(s):  
British Columbia ◽  
North America ◽  
Green Alga ◽  
Marine Environment ◽  
High Energy ◽  
Lower Jurassic ◽  
Early Jurassic ◽  
Associated Fauna ◽  
North Central ◽  
Commensal Relationship

Late Early Jurassic heteroporid bryozoa occur in arenaceous carbonates near Turnagain Lake, north-central British Columbia. The occurrence of Heteropora tipperi n. sp. marks the first documentation of Early Jurassic cyclostome bryozoa in North America. The associated fauna, comprising the ammonite Harpoceras, the foraminifer Reinholdella, and the pelecypod Weyla, establish the age as Early Toarcian. Other associated biota include an endolithic green alga(e), which is demonstrated to have a commensal relationship with H. tipperi n. sp. Sedimentologic and biotic data from the host strata point to a shallow, temperate, high-energy, normal marine environment.

Revision of Tenticospirifer Tien, 1938, and similar spiriferid brachiopod genera from the Late Devonian (Frasnian) of Eurasia, North America, and Australia

2000 ◽  
Vol 74 (3) ◽  
pp. 444-463 ◽  
Author(s):  
Xueping Ma ◽  
Jed Day
Keyword(s):  
North America ◽  
Sea Level ◽  
South China ◽  
North American ◽  
Type Species ◽  
Western Europe ◽  
Late Devonian ◽  
Carbonate Platforms ◽  
The North ◽  
New Family

The cyrtospiriferid brachiopod genus Tenticospirifer Tien, 1938, is revised based on restudy of the type species from the Frasnian (Late Devonian) of the Russian Platform. As revised the genus includes cyrtospiriferid species with pyramidal ventral valves, catacline ventral interareas, a narrow delthyrium, few sinal plications, and lack a median dorsal septum and pseudodeltidium. All species retained in the genus are of Givetian and Frasnian age. All Famennian age species described from South China and North America are rejected from the genus. It appears that Tenticospirifer evolved during the early Givetian in western Europe and remained endemic to that region during the remainder of the Givetian. Successive migrations of Tenticospirifer from eastern Laurussia to North America, then to South China and possibly Australia, coincided with middle and late Frasnian eustatic sea level rises, respectively. The North American species Spirifera cyrtinaformis Hall and Whitfield, 1872, and related species identified as Tenticospirifer by North American workers, are reassigned to Conispirifer Lyashenko, 1985. Its immigration to and widespread dispersal in carbonate platforms of western Laurussia, northern Gondwana and tropical island arcs (?) coincided with a major late Frasnian eustatic sea level rise. The new family Conispiriferidae is proposed with Conispirifer Lyashenko, 1985, selected as the type genus. The new family also includes the new genus Pyramidaspirifer with Platyrachella alta Fenton and Fenton, 1924, proposed as the type species. The affinity of the new family remains uncertain pending restudy of key genera currently included in the Superfamily Cyrtospiriferoidea. Available data from the Devonian brachiopod literature indicate that species of Pyramidaspirifer are restricted to late Frasnian deposits of central and western North America.

An Early Cretaceous (Berriasian) fossil-bearing locality from the Rocky Mountains of Alberta, yielding the oldest dinosaur skeletal remains from western Canada

2020 ◽  
Vol 57 (4) ◽  
pp. 542-552 ◽  
Author(s):  
Ramon S. Nagesan ◽  
James A. Campbell ◽  
Jason D. Pardo ◽  
Kendra I. Lennie ◽  
Matthew J. Vavrek ◽  
...  
Keyword(s):  
North America ◽  
Early Cretaceous ◽  
Depositional Environment ◽  
Upper Cretaceous ◽  
Upper Jurassic ◽  
High Energy ◽  
Western Canada ◽  
Western North America ◽  
Terrestrial Vertebrate ◽  
Overlying Strata

Western North America preserves iconic dinosaur faunas from the Upper Jurassic and Upper Cretaceous, but this record is interrupted by an approximately 20 Myr gap with essentially no terrestrial vertebrate fossil localities. This poorly sampled interval is nonetheless important because it is thought to include a possible mass extinction, the origin of orogenic controls on dinosaur spatial distribution, and the origin of important Upper Cretaceous dinosaur taxa. Therefore, dinosaur-bearing rocks from this interval are of particular interest to vertebrate palaeontologists. In this study, we report on one such locality from Highwood Pass, Alberta. This locality has yielded a multitaxic assemblage, with the most diagnostic material identified so far including ankylosaurian osteoderms and a turtle plastron element. The fossil horizon lies within the upper part of the Pocaterra Creek Member of the Cadomin Formation (Blairmore Group). The fossils are assigned as Berriasian (earliest Cretaceous) in age, based on previous palynomorph analyses of the Pocaterra Creek Member and underlying and overlying strata. The fossils lie within numerous cross-bedded sandstone beds separated by pebble lenses. These sediments are indicative of a relatively high-energy depositional environment, and the distribution of these fossils over multiple beds indicates that they accumulated over multiple events, possibly flash floods. The fossils exhibit a range of surface weathering, having intact to heavily weathered cortices. The presence of definitive dinosaur material from near the Jurassic–Cretaceous boundary of Alberta establishes the oldest record of dinosaur body fossils in western Canada and provides a unique opportunity to study the Early Cretaceous dinosaur faunas of western North America.

A tetrapod fauna from within the Devonian Antarctic Circle

Science ◽  
2018 ◽  
Vol 360 (6393) ◽  
pp. 1120-1124 ◽  
Author(s):  
Robert Gess ◽  
Per Erik Ahlberg
Keyword(s):  
South Africa ◽  
North America ◽  
Late Devonian ◽  
Body Fossil ◽  
The Antarctic

Until now, all known fossils of tetrapods (limbed vertebrates with digits) and near-tetrapods (such asElpistostege,Tiktaalik, andPanderichthys) from the Devonian period have come from localities in tropical to subtropical paleolatitudes. Most are from Laurussia, a continent incorporating Europe, Greenland, and North America, with only one body fossil and one footprint locality from Australia representing the southern supercontinent Gondwana. Here we describe two previously unknown tetrapods from the Late Devonian (late Famennian) Gondwana locality of Waterloo Farm in South Africa, then located within the Antarctic Circle, which demonstrate that Devonian tetrapods were not restricted to warm environments and suggest that they may have been global in distribution.

A Study of Recrystallization Texture Formation in Cold Rolled Iron Sheets with X-Ray Diffraction Techniques

1970 ◽  
Vol 14 ◽  
pp. 214-230 ◽  
Author(s):  
M. Matsuo ◽  
S. Hayami ◽  
S. Nagashima
Keyword(s):  
Cold Rolling ◽  
Recrystallization Texture ◽  
High Energy ◽  
Orientation Dependence ◽  
Primary Recrystallization ◽  
Texture Formation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Stable Orientation ◽  
Rotational Orientation

AbstractThe possibility that primary recrystallization textures are influenced by local inhomogeneities of deformation induced in the regions of grain boundaries has been confirmed by comparing the cold rolling and the annealing textures of polycrystalline pure irons which were different in the grain size prior to cold rolling. Analyses were made for the effects of deformation on crystals, namely storage of lattice strain and orientation spread, with application of X-ray diffraction techniques, in order to elucidate the role of in homogeneities of deformation on recrystallization texture formation. Apparent correspondence was found between the orientation dependence of stored strain energy and the textural change on recrystallization. This is a scribed to oriented nucleation in high energy blocks, in the case of originally large-grain material in which the effects of inhomogeneities of deformation are small. But discrepancies arise on this basis in originally small - grain material in which the effects of inhomogeneities of deformation are thought to be considerable. The discrepancy is inferred to arise as an effect of local inhomogeneities of deformation, from the change in the trend of rotational orientation spreads from, a stable orientation and the extent of development of potential nuclei of recrystallization at high energy blocks in the orientation spreads. The change is considered to give rise to the variation in amount of microstrain distribution, which is expressed in recovery characteristics of lattice strains and in the dependence of microstrains on the column length as analyzed by following the procedure of Warren-Averbach.

Gigantocharinus szatmaryi, a new trigonotarbid arachnid from the Late Devonian of North America (Chelicerata, Arachnida, Trigonotarbida)

2000 ◽  
Vol 74 (1) ◽  
pp. 25-31 ◽  
Author(s):  
William A. Shear
Keyword(s):  
North America ◽  
Middle Devonian ◽  
New Genus ◽  
Upper Devonian ◽  
Late Carboniferous ◽  
Late Devonian ◽  
New Genus And Species ◽  
Significant Time ◽  
The Family ◽  
Time Gap

A new trigonotarbid arachnid, Gigantocharinus szatmaryi new genus and species, is described from Upper Devonian (Late Famennian) sediments in Pennsylvania. Devonian trigonotarbids were known before from only a single North American locality and several European ones. The new trigonotarbid occurs in what had previously been a significant time gap between the faunas of the Middle Devonian and the late Carboniferous. Gigantocharinus szatmaryi is assigned with some hesitation to the family Palaeocharinidae.

scholarly journals Time Course of Postischemic Intracellular Alkalosis Reflects the Duration of Ischemia

1990 ◽  
Vol 10 (6) ◽  
pp. 860-865 ◽  
Author(s):  
Michael Chopp ◽  
Hua Chen ◽  
Ana M. Q. Vande Linde ◽  
Eileen Brown ◽  
K. M. A. Welch
Keyword(s):  
Specific Gravity ◽  
Brain Tissue ◽  
Cerebral Edema ◽  
Time Course ◽  
High Energy ◽  
Resonance Spectroscopy ◽  
Ph Profile ◽  
Tissue Ph ◽  
Tissue Edema

We investigated the long-term (up to 1 week) relationships between the duration of cerebral ischemia and postischemic energy metabolic profile, pH, and tissue edema in the rat. Ten rats each were subjected to 8 or 12 min of forebrain ischemia induced by bicarotid occlusion concurrent with systemic hypotension, and the results were compared with those of 10 sham-operated rat controls. In vivo 31P nuclear magnetic resonance spectroscopy was performed prior to ischemia and at intervals up to 168 h after ischemia. Cerebral edema (measured by specific gravity) was assessed prior to ischemia and at 24, 72, and 168 h after ischemia. The data revealed significant differences in the brain tissue pH profile over time between the ischemic groups (p < 0.03). The 12-min ischemic animals exhibited brain tissue alkalosis (pH = 7.27 ± 0.12) at 24 h compared with both sham (pH = 7.09 ± 0.08) at 24 h and preischemic (pH = 7.06 ± 0.04) pH values. The pH remained alkalotic (pH = 7.23 ± 0.15) through the 48-h time period. In contrast, in the 8-min group, the onset of alkalosis was delayed until 48 h after ischemia (pH = 7.24 ± 0.15), and pH remained alkalotic for only 24 h. No difference in high-energy phosphate metabolism was detected between groups. A different time dependence of tissue pH and specific gravity changes after 12 min of ischemia was detected. The present study suggests that the duration of an ischemic event marks the time of onset of brain tissue alkalosis and its duration and that cerebral edema alone cannot explain the pH changes.

Russian Devonian brachiopod genera Cyrtinoides and Komiella in North America

1993 ◽  
Vol 67 (6) ◽  
pp. 952-958 ◽  
Author(s):  
J. G. Johnson ◽  
R. B. Blodgett
Keyword(s):  
New Species ◽  
North America ◽  
Carbonate Platform ◽  
Southern Urals ◽  
Late Devonian ◽  
Western North America ◽  
The Southern Urals ◽  
New Family ◽  
Marine Migration ◽  
Subjective Synonym

The Middle Devonian brachiopod genus Cyrtinoides, described from the southern Urals, is a senior subjective synonym of Mucroclipeus, previously known only from eastern and western North America. The Middle and Late Devonian cyrtinid brachiopod genus Komiella, previously known only from the Timan Range of eastern Europe, is identified from west-central Alaska and Nevada. A new family Komiellidae is proposed. New species are Komiella gilberti, K. magnasulca, and K. stenoparva. Known species of both genera occupy carbonate platform foreslope facies or shelf basins, allowing open marine migration via peripheral biofacies.

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