The effects of skeletal asymmetry on interpreting biologic variation and taphonomy in the fossil record

Paleobiology ◽  
2018 ◽  
Vol 45 (1) ◽  
pp. 154-166 ◽  
Author(s):  
Brandon P. Hedrick ◽  
Emma R. Schachner ◽  
Gabriel Rivera ◽  
Peter Dodson ◽  
Stephanie E. Pierce
Keyword(s):  
Fossil Record ◽  
Quantitative Data ◽  
Shape Change ◽  
Relative Magnitude ◽  
Shape Variation ◽  
Fossil Taxon ◽  
Asymmetric Component ◽  
Principal Directions ◽  
Skeletal Asymmetry ◽  
Taphonomic Processes

AbstractBiologic asymmetry is present in all bilaterally symmetric organisms as a result of normal developmental instability. However, fossilized organisms, which have undergone distortion due to burial, may have additional asymmetry as a result of taphonomic processes. To investigate this issue, we evaluated the magnitude of shape variation resulting from taphonomy on vertebrate bone using a novel application of fluctuating asymmetry. We quantified the amount of total variance attributed to asymmetry in a taphonomically distorted fossil taxon and compared it with that of three extant taxa. The fossil taxon had an average of 27% higher asymmetry than the extant taxa. In spite of the high amount of taphonomic input, the major axes of shape variation were not greatly altered by removal of the asymmetric component of shape variation. This presents the possibility that either underlying biologic trends drive the principal directions of shape change irrespective of asymmetric taphonomic distortion or that the symmetric taphonomic component is large enough that removing only the asymmetric component is inadequate to restore fossil shape. Our study is the first to present quantitative data on the relative magnitude of taphonomic shape change and presents a new method to further explore how taphonomic processes impact our interpretation of the fossil record.

The structure of cranidial shape variation in three early ptychoparioid trilobite species from the Dyeran-Delamaran (traditional “Lower-Middle” Cambrian) boundary interval of Nevada, U.S.A.

2011 ◽  
Vol 85 (2) ◽  
pp. 179-225 ◽  
Author(s):  
Mark Webster
Keyword(s):  
Growth Pattern ◽  
Shape Change ◽  
Relative Magnitude ◽  
New Combination ◽  
Single Source ◽  
Shape Variation ◽  
Geometric Morphometric ◽  
Middle Cambrian ◽  
Interspecific Differences ◽  
Species Specific

The structure of cranidial shape variation in the early ptychoparioid trilobites Crassifimbra walcotti, Crassifimbra? metalaspis (new combination), and Eokochaspis nodosa is explored using landmark-based geometric morphometric techniques, and is found to be generally similar among the species. Allometry is the strongest single source of cranidial shape variation within each species. The species share several trends in their respective patterns of ontogenetic shape change, but differ in the relative magnitude of these shared trends. Species-specific trends are also present. Each species follows a unique trajectory of ontogenetic shape change. The species exhibit subtle but significant differences in mean cranidial shape even at small size (sagittal length 1.75 mm); the magnitude of interspecific differences becomes larger at larger size (sagittal length 4.2 mm).For conspecific cranidia of a given size, the major pattern of covariance among anatomical parts is essentially identical to the pattern of covariance among those parts during ontogeny. Developmentally determined covariance patterns among cranidial regions might be responsible for ontogenetic shape change and a portion of non-allometric shape intraspecific variation. Interspecific differences in cranidial shape resulted from complex local modifications to growth pattern and cannot be attributed to simple ontogenetic scaling.The new collections permit the first description of non-cranidial sclerites of C. walcotti. A cephalic median organ is documented on C. walcotti, representing the oldest known occurrence of this structure in trilobites.

Ontogeny in the steinmanellines (Bivalvia: Trigoniida): an intra- and interspecific appraisal using the Early Cretaceous faunas from the Neuquén Basin as a case study

Paleobiology ◽  
2021 ◽  
pp. 1-23
Author(s):  
Pablo S. Milla Carmona ◽  
Dario G. Lazo ◽  
Ignacio M. Soto
Keyword(s):  
Trajectory Analysis ◽  
Sedentary Lifestyle ◽  
Shape Change ◽  
Shell Shape ◽  
Shape Variation ◽  
Ontogenetic Changes ◽  
Ontogenetic Trajectories ◽  
Higher Genus ◽  
Gradual Decay

Abstract Despite the paleontological relevance and paleobiological interest of trigoniid bivalves, our knowledge of their ontogeny—an aspect of crucial evolutionary importance—remains limited. Here, we assess the intra- and interspecific ontogenetic variations exhibited by the genus Steinmanella Crickmay (Myophorellidae: Steinmanellinae) during the early Valanginian–late Hauterivian of Argentina and explore some of their implications. The (ontogenetic) allometric trajectories of seven species recognized for this interval were estimated from longitudinal data using 3D geometric morphometrics, segmented regressions, and model selection tools, and then compared using trajectory analysis and allometric spaces. Our results show that within-species shell shape variation describes biphasic ontogenetic trajectories, decoupled from ontogenetic changes shown by sculpture, with a gradual decay in magnitude as ontogeny progresses. The modes of change characterizing each phase (crescentic growth and anteroposterior elongation, respectively) are conserved across species, thus representing a feature of Steinmanella ontogeny; its evolutionary origin is inferred to be a consequence of the rate modification and allometric repatterning of the ancestral ontogeny. Among species, trajectories are more variable during early ontogenetic stages, becoming increasingly conservative at later stages. Trajectories’ general orientation allows recognition of two stratigraphically consecutive groups of species, hinting at a potentially higher genus-level diversity in the studied interval. In terms of functional morphology, juveniles had a morphology more suited for active burrowing than adults, whose features are associated with a sedentary lifestyle. The characteristic disparity of trigoniids could be related to the existence of an ontogenetic period of greater shell malleability betrayed by the presence of crescentic shape change.

scholarly journals Unravelling the hybrid vigor in domestic equids: the effect of hybridization on bone shape variation and covariation

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Pauline Hanot ◽  
Anthony Herrel ◽  
Claude Guintard ◽  
Raphaël Cornette
Keyword(s):  
First Generation ◽  
Shape Change ◽  
Morphological Integration ◽  
Hybrid Vigor ◽  
F1 Hybrids ◽  
Shape Variation ◽  
Locomotor System ◽  
Domestic Horses ◽  
Functional Mechanisms ◽  
Underlying Processes

Abstract Background Hybridization has been widely practiced in plant and animal breeding as a means to enhance the quality and fitness of the organisms. In domestic equids, this hybrid vigor takes the form of improved physical and physiological characteristics, notably for strength or endurance. Because the offspring of horse and donkey is generally sterile, this widely recognized vigor is expressed in the first generation (F1). However, in the absence of recombination between the two parental genomes, F1 hybrids can be expected to be phenotypically intermediate between their parents which could potentially restrict the possibilities of an increase in overall fitness. In this study, we examine the morphology of the main limb bones of domestic horses, donkeys and their hybrids to investigate the phenotypic impact of hybridization on the locomotor system. We explore bone shape variation and covariation to gain insights into the morphological and functional expressions of the hybrid vigor commonly described in domestic equids. Results Our data reveal the occurrence of transgressive effects on several bones in the F1 generation. The patterns of morphological integration further demonstrate that the developmental processes producing covariation are not disrupted by hybridization, contrary to functional ones. Conclusions These results suggest that an increase in overall fitness could be related to more flexibility in shape change in hybrids, except for the main forelimb long bones of which the morphology is strongly driven by muscle interactions. More broadly, this study illustrates the interest of investigating not only bone shape variation but also underlying processes, in order to contribute to better understanding how developmental and functional mechanisms are affected by hybridization.

scholarly journals The aerodynamics of jumping rope

2011 ◽  
Vol 468 (2139) ◽  
pp. 720-730 ◽  
Author(s):  
Jeffrey M. Aristoff ◽  
Howard A. Stone
Keyword(s):  
Shape Change ◽  
Nonlinear Differential Equations ◽  
Reynolds Numbers ◽  
Relative Magnitude ◽  
Relative Reduction ◽  
Centrifugal Forces ◽  
Dimensionless Groups ◽  
Out Of Plane ◽  
High Reynolds ◽  
Jump Rope

We consider the influence of aerodynamic forces on the shape of a whirling filament that is held at both ends, i.e. a jump rope. At high Reynolds numbers, the rope curls out of the plane and towards the axis of rotation—a feature we demonstrate via experiment. We derive a pair of coupled nonlinear differential equations that characterize the steady-state shape of the rope, and the resulting eigenvalue problem is solved numerically. The solution depends on two dimensionless groups: the ratio between the length of the rope and the distance between its ends, and the relative magnitude of the aerodynamic to centrifugal forces. As the latter ratio is progressively increased, the tension in the rope and the out-of-plane deflection increases, until eventually the rope reaches a limiting shape. Finally, we show that the airflow-induced shape change leads to a relative reduction in drag and has implications for successful skipping.

The morphology of the terminal phalanges in Permo-Carboniferous synapsids: an evolutionary perspective

2007 ◽  
Vol 44 (2) ◽  
pp. 267-274 ◽  
Author(s):  
Hillary C Maddin ◽  
Robert R Reisz
Keyword(s):  
Fossil Record ◽  
Feeding Behaviour ◽  
Shape Change ◽  
Morphological Features ◽  
Evolutionary Perspective ◽  
Crown Group ◽  
Clear Trend ◽  
Informative Signal ◽  
Size And Shape ◽  
And Function

Morphological features of the terminal phalanges of extinct tetrapods can be used to infer whether or not keratinous claws were present even though these structures are not preserved in the fossil record. Such features as dense vascularization grooves and foramina, and a general claw-like morphology, are present in some of the earliest fully terrestrial tetrapods, the Permo-Carboniferous synapsids. Early synapsids are represented by a rich fossil record that preserves the detailed anatomy of the terminal phalanges and allows for an examination of the early evolution of these structures in a well-resolved phylogenetic context. The pattern of change in the morphology of the terminal phalanges of five basal synapsids, Cotylorhynchus romeri, Varanops sp., Edaphosaurus boanerges, Haptodus garnettensis, and Dimetrodon limbatus, reveals a clear trend from a broad, flat, and spatulate morphology in the basal taxa to a tall, narrow, and curved structure. This trend in overall shape change does not reflect changes in feeding behaviour. The size and shape of the flexor tubercle appears to be a factor of size and function, rather than possessing a phylogenetically informative signal. The osteological features used to infer the presence of a keratinous sheath in the synapsids are also observed in the non-amniote taxon Diadectes absitus. This indicates that claws were not an amniote innovation and that they instead originated somewhere outside the crown group Amniota.

scholarly journals Computational Shape Models Characterize Shape Change of the Left Atrium in Atrial Fibrillation

2014 ◽  
Vol 8s1 ◽  
pp. CMC.S15710 ◽  
Author(s):  
Joshua Cates ◽  
Erik Bieging ◽  
Alan Morris ◽  
Gregory Gardner ◽  
Nazem Akoum ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Left Atrium ◽  
Shape Change ◽  
Three Dimensional ◽  
Shape Variation ◽  
Mr Images ◽  
Significant Group ◽  
Empirical Observation ◽  
Shape Models ◽  
Statistical Shape

Shape change of the left atrium (LA) and LA appendage in atrial fibrillation (AF) patients is hypothesized to be linked to AF pathology and to play a role in thrombogenesis; however, many aspects of shape variation in the heart are poorly understood. To date, studies of the LA shape in AF have been limited to empirical observation and summary metrics, such as volume and its likeness to a sphere. This paper describes a more comprehensive approach to the study of the LA shape through the use of computationally derived statistical shape models. We describe practical approaches that we have developed to extract shape parameters automatically from the three-dimensional MR images of the patient. From these images and our techniques, we can produce a more comprehensive description of LA geometric variability than that has been previously possible. We present the methodology and results from two examples of specific analyses using shape models: (1) we describe statistically significant group differences between the normal control and AF patient populations ( n = 137) and (2) we describe characteristic shapes of the LA appendage that are associated with the risk of thrombogenesis determined by transesophageal echocardiography ( n = 203).

scholarly journals Procesos tafonómicos en una encrinita regional pensilvánica (Atokano), Sonora, México

2017 ◽  
Vol 65 (1-1) ◽  
pp. 147
Author(s):  
Catalina Gómez-Espinosa ◽  
Blanca Estela Buitrón-Sánchez
Keyword(s):  
North America ◽  
Debris Flow ◽  
Fossil Record ◽  
High Energy ◽  
Marine Communities ◽  
Storm Wave ◽  
Energy Environment ◽  
Taphonomic Processes

Taphonomic processes in a Pennsylvanian regional encrinite (Atokano), Sonora, Mexico. Crinoids have an extensive fossil record and were a major component in Paleozoic marine communities; encrinites are common crinoid accumulations where specimens are totally disarticulated from the Ordovician to the Jurassic. In Sonora, Mexico, the crinoid skeleton was altered during diagenesis and replaced by silica. The corrasion was high; the incrustation low and there is evidence of dissolution and compaction. This is a sedimentological type accumulation in a high energy environment of allochthonous organism transported in a debris flow, deposited below the storm wave base in an outer ramp. Our results can be correlated with regional encrinites prevalent in the Pennsylvanian cyclothems of North America. Rev. Biol. Trop. 65(Suppl. 1): S147-S159. Epub 2017 November 01. 

scholarly journals Impact of climate and hydrochemistry on shape variation – a case study on Neotropical cytheroidean Ostracoda

2017 ◽  
Author(s):  
Claudia Wrozyna ◽  
Thomas A. Neubauer ◽  
Juliane Meyer ◽  
Maria Ines F. Ramos ◽  
Werner E. Piller
Keyword(s):  
Least Squares ◽  
Shape Change ◽  
Morphological Variability ◽  
Morphological Characteristics ◽  
Generalized Least Squares ◽  
Structural Features ◽  
Shape Variation ◽  
Valve Morphology ◽  
Temperature Seasonality ◽  
The Impact

Abstract. How environmental change affects a species’ phenotype is crucial not only for taxonomy and biodiversity assessments but also for their application as (paleo-)ecological indicators. Previous investigations addressing the impact of climate and hydrochemical regime on ostracod valve morphology have yielded quite contrasting results. Frequently identified ecological factors influencing carapace shape are salinity, cation and sulphate concentrations and alkalinity. Here, we present a thorough approach integrating data from carapace outline and surface details of the ubiquitous Neotropical cytheroidean ostracod species Cytheridella ilosvayi, as well as several climatic and hydrochemical variables, in order to investigate a potential link between morphology and environmental conditions. A previous study lately demonstrated considerable biogeographical variation in valve morphology among Floridian, Mexican and Brazilian populations of this species. We hypothesize that the climatic differences between the regions it inhabits and associated differences in hydrochemical regimes have influenced valve morphology and eventually led to biogeographically distinctive groups. Generalized least-squares Procrustes Analyses based on outline and structural features were applied to left and right valves of adult females and males. The analyses identified relative carapace length and shape symmetry as most important morphological characteristics representing shape change across all datasets. Two-block partial least-squares analyses and multiple regressions indicate strong relationships between morphological and environmental variables, specifically with temperature seasonality, annual precipitation and chloride and sulphate concentrations. We hypothesize that increased temperature seasonality slowed down growth rates during colder months, potentially triggering the development of shortened valves with well-developed brood pouches. Differences in chloride and sulphate concentrations, related to fluctuations in precipitation, are considered to affect valve development via controlling osmoregulation and carapace calcification. These factors represent hitherto unknown drivers for ostracod ecophenotypy and emphasise that environmental predictors for morphological variability are not consistent across non-marine ostracods.

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