The geometry of morphospaces: lessons from the classic Raup shell coiling model

2016 ◽  
Vol 92 (2) ◽  
pp. 1142-1155 ◽  
Author(s):  
Sylvain Gerber
Keyword(s):  
Shell Coiling

scholarly journals Further twists in gastropod shell evolution

2008 ◽  
Vol 4 (2) ◽  
pp. 179-182 ◽  
Author(s):  
Reuben Clements ◽  
Thor-Seng Liew ◽  
Jaap Jan Vermeulen ◽  
Menno Schilthuizen
Keyword(s):  
Evolutionary Biology ◽  
Logarithmic Spiral ◽  
Spiral Growth ◽  
Evolutionary Perspective ◽  
Gastropod Shell ◽  
Form And Function ◽  
Evolutionary Origins ◽  
Taxonomic Groups ◽  
And Function ◽  
Shell Coiling

The manner in which a gastropod shell coils has long intrigued laypersons and scientists alike. In evolutionary biology, gastropod shells are among the best-studied palaeontological and neontological objects. A gastropod shell generally exhibits logarithmic spiral growth, right-handedness and coils tightly around a single axis. Atypical shell-coiling patterns (e.g. sinistroid growth, uncoiled whorls and multiple coiling axes), however, continue to be uncovered in nature. Here, we report another coiling strategy that is not only puzzling from an evolutionary perspective, but also hitherto unknown among shelled gastropods. The terrestrial gastropod Opisthostoma vermiculum sp. nov. generates a shell with: (i) four discernable coiling axes, (ii) body whorls that thrice detach and twice reattach to preceding whorls without any reference support, and (iii) detached whorls that coil around three secondary axes in addition to their primary teleoconch axis. As the coiling strategies of individuals were found to be generally consistent throughout, this species appears to possess an unorthodox but rigorously defined set of developmental instructions. Although the evolutionary origins of O. vermiculum and its shell's functional significance can be elucidated only once fossil intermediates and live individuals are found, its bewildering morphology suggests that we still lack an understanding of relationships between form and function in certain taxonomic groups.

PATTERNS AND PROCESSES IN MORPHOSPACE: GEOMETRIC MORPHOMETRICS OF THREE-DIMENSIONAL OBJECTS

2016 ◽  
Vol 22 ◽  
pp. 71-99 ◽  
Author(s):  
P. David Polly ◽  
Gary J. Motz
Keyword(s):  
Geometric Morphometrics ◽  
Three Dimensional ◽  
Shape Space ◽  
Multivariate Methods ◽  
Morphometric Data ◽  
Three Dimensional Objects ◽  
Mathematical Properties ◽  
Patterns And Processes ◽  
The Relationship ◽  
Shell Coiling

AbstractFocusing on geometric morphometrics (GMM), we review methods for acquiring morphometric data from 3-D objects (including fossils), algorithms for producing shape variables and morphospaces, the mathematical properties of shape space, especially how they relate to morphogenetic and evolutionary factors, and issues posed by working with fossil objects. We use the Raupian shell-coiling equations to illustrate the complexity of the relationship between such factors and GMM morphospaces. The complexity of these issues re-emphasize what are arguably the two most important recommendations for GMM studies: 1) always use multivariate methods and all of the morphospace axes in an analysis; and 2) always anticipate the possibility that the factors of interest can have complex, nonlinear relationships with shape.

Abnormalities as natural experiments: a morphogenetic model for coiling regulation in planispiral ammonites

Paleobiology ◽  
2002 ◽  
Vol 28 (1) ◽  
pp. 127-138 ◽  
Author(s):  
Antonio G. Checa ◽  
Takashi Okamoto ◽  
Helmut Keupp
Keyword(s):  
Theoretical Model ◽  
Biological System ◽  
Vertical Plane ◽  
Vertical Direction ◽  
Normal Growth ◽  
Growth Direction ◽  
Natural Experiments ◽  
Growth Path ◽  
Lateral Deviation ◽  
Shell Coiling

Exceptional examples of planispiral ammonites that were infested by epizoans during life display alterations of their normal coiling. Most commonly, the epizoan(s) settled on the venter of the ammonite and constituted an obstacle for the whorl tube grown one whorl later; this caused lateral deviation of the whorl tube and tilting of the ammonoid because of changes in the hydrostatic condition; from here on, the whorl tube periodically crossed the venter of the preceding whorl, thereby producing a zigzag coiling pattern. Some epizoans, which were particularly centered on the midventer, provoked detachment between whorls. In a few cases, lateral placement of the epizoan did not directly obstruct the normal growth path of the ammonite but induced a trochospiral coiling pattern. Both the zigzag and the trochospiral pattern were created when the ammonite tried to maintain the growth direction within the vertical plane at the same time as whorls remained in contact along a differentiated dorsal epithelium. The aperture reacted to changes in growth direction, to maintain also a permanent angle with the vertical direction. Growth direction, then, was a major morphogenetic parameter in ammonites, because it contained the necessary instructions for correct shell coiling. The model based on the observation of fabricational defects has been tested by a theoretical model by which the different situations so far observed are simulated and in which the parameters are the morphogenetic instructions inferred to have been present in the biological system.

scholarly journals Dollo's law and the re–evolution of shell coiling

2003 ◽  
Vol 270 (1533) ◽  
pp. 2551-2555 ◽  
Author(s):  
R. Collin ◽  
R. Cipriani
Keyword(s):  
Dollo’S Law ◽  
Shell Coiling

Going round the twist—an empirical analysis of shell coiling in helicospiral gastropods

Paleobiology ◽  
2021 ◽  
pp. 1-18
Author(s):  
Katie S. Collins ◽  
Roman Klapaukh ◽  
James S. Crampton ◽  
Michael F. Gazley ◽  
C. Ian Schipper ◽  
...  
Keyword(s):  
Shape Change ◽  
Implicit Assumption ◽  
Translation Rate ◽  
Shell Form ◽  
Geologic Time ◽  
Morphological Model ◽  
Best Fit ◽  
External Form ◽  
Shell Coiling

Abstract The logarithmic helicospiral has been the most widely accepted model of regularly coiled molluscan form since it was proposed by Moseley and popularized by Thompson and Raup. It is based on an explicit assumption that shells are isometric and grow exponentially, and an implicit assumption that the external form of the shell follows the internal shape, which implies that the parameters of the spiral could be reconstructed from the external whorl profile. In this contribution, we show that these assumptions fail on all 25 gastropod species we examine. Using a dataset of 176 fossil and modern gastropod shells, we construct an empirical morphospace of coiling using the parameters of whorl expansion rate, translation rate, and rate of increasing distance from coiling axis, plus rate of aperture shape change, from their best-fit models. We present a case study of change in shell form through geologic time in the austral family Struthiolariidae to demonstrate the utility of our approach for evolutionary paleobiology. We fit various functions to the shell-coiling parameters to demonstrate that the best morphological model is not the same for each parameter. We present a set of R routines that will calculate helicospiral parameters from sagittal sections through coiled shells and allow workers to compare models and choose appropriate sets of parameters for their own datasets. Shell-form parameters in the Struthiolariidae highlight a hitherto neglected hypothesis of relationship between Antarctic Perissodonta and the enigmatic Australian genus Tylospira that fits the biogeographic and stratigraphic distribution of both genera.

Shell Coiling in Gastropods: Analysis by Stereographic Projection

Palaios ◽  
1989 ◽  
Vol 4 (4) ◽  
pp. 374 ◽  
Author(s):  
Spafford C. Ackerly
Keyword(s):  
Stereographic Projection ◽  
Shell Coiling

Snail shell coiling (re-)evolution and the evo-devo revolution

2006 ◽  
Vol 44 (1) ◽  
pp. 1-7 ◽  
Author(s):  
S. Urdy ◽  
R. Chirat
Keyword(s):  
Snail Shell ◽  
Evo Devo ◽  
Shell Coiling

scholarly journals Opposite shell-coiling morphs of the tropical land snailAmphidromus martensishow no spatial-scale effects

Ecography ◽  
2006 ◽  
Vol 29 (4) ◽  
pp. 477-486 ◽  
Author(s):  
Paul G. Craze ◽  
Berjaya bin Elahan ◽  
Menno Schilthuizen
Keyword(s):  
Spatial Scale ◽  
Scale Effects ◽  
Shell Coiling
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