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Journal Article

A model of wear in curved mammal teeth: controls on occlusal morphology and the evolution of hypsodonty in lagomorphs Available to Purchase

Andrea R. Bair
Journal: Paleobiology
Published: 01 January 2007
Paleobiology (2007) 33 (1): 53–75.
DOI: https://doi.org/10.1666/06044.1
... for shape differences observed in hypsodont teeth, P4s of the archaic lagomorphs Russellagus and Hesperolagomys , which exhibit pronounced change with wear, and Ondatra lower incisors, which show minimal change with wear. Using this quantification, I generate theoretical curvature morphologies and describe...
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View PDF for article title, A model of wear in curved mammal teeth: controls on occlusal morphology and the evolution of hypsodonty in lagomorphs
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Journal Article

New rodents and lagomorphs from the Upper Miocene Wood Mountain Formation of southern Saskatchewan Free

John E. Storer
Published: 01 August 1970
Canadian Journal of Earth Sciences (1970) 7 (4): 1125–1129.
DOI: https://doi.org/10.1139/e70-106
... russelli , sp. nov.; the heteromyids Perognathus saskatchewanensis , perognathoides kleinfelderi , and Peridiomys borealis , spp. nov.; the entoptychine geomyid Lignimus montis , gen. et sp. nov.; and the ochotonids Hesperolagomys fluviatilis , sp. nov., and Russellagus vonhofi , gen. et sp. nov. All taxa...
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Figure 10. Results of modeled wear compared with observed wear of actual teeth from test samples. A, C, E: graphs comparing numerical values; gray rectangle indicates range of measured values, bounded by the area of tooth occupation (λi represents the test specimen at its initial wear stage, λi + ηi represents the most advanced stage of wear). B, D, F, Illustrations comparing cumulative wear surface produced by modeled wear (left) with worn specimens from test samples (right; pikas only). A, Graph of values of x from modeled wear with measured range of values of the occlusal width for Russellagus P4. B, Cumulative wear surface of Russellagus P4. C, Graph of values of x from modeled wear with measured range of values of the occlusal width for Hesperolagomys P4. D, Cumulative wear surface of Hesperolagomys P4. E, Graph of values of x from modeled wear with measured range of values of the occlusal width for Ondatra lower incisor. F, Cumulative wear surface of Ondatra lower incisor

Figure 10. Results of modeled wear compared with observed wear of actual t... Available to Purchase

Published: 01 January 2007
width for Russellagus P4. B, Cumulative wear surface of Russellagus P4. C, Graph of values of x from modeled wear with measured range of values of the occlusal width for Hesperolagomys P4. D, Cumulative wear surface of Hesperolagomys P4. E, Graph of values of x from modeled wear
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Figure 3. Hybrid tooth curvature morphospace. Theoretical curvature morphologies 1–29 and curvatures of Ondatra, Russellagus, and Hesperolagomys teeth plotted by relative curvature (r2/r1) and relative displacement (d/r1). The light-gray area is the morphospace included in this study. Theoretical morphologies are scaled and the center of the outer circle is located at the appropriate coordinates for each morphology. Three thick gray lines mark mathematical boundaries to morphologies

Figure 3. Hybrid tooth curvature morphospace. Theoretical curvature morpho... Available to Purchase

Published: 01 January 2007
Figure 3. Hybrid tooth curvature morphospace. Theoretical curvature morphologies 1–29 and curvatures of Ondatra , Russellagus , and Hesperolagomys teeth plotted by relative curvature ( r 2 / r 1 ) and relative displacement ( d / r 1 ). The light-gray area is the morphospace included
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Figure 1. Extreme wear-related changes to the occlusal surface of upper cheek teeth of archaic ochotonids. Scale bar, 1 mm. A, Maxilla with P3-M2 of a young individual of Desmatolagus pusillis, showing the crown pattern of upper cheek teeth at the occlusal surface (redrawn from Huang 1987: Fig. 4 [in part]). B, Maxilla with P3–M2 of old individual of D. pusillis, showing great increase in transverse width and loss of crown pattern of upper cheek teeth at the occlusal surface as compared with the specimen in A (redrawn from Huang 1987: Fig. 6 [in part]). Same orientation as in A. C, Isolated P4 of old individual of D. pusillis, illustrating tooth curvature and topographically complex occlusal surface with a “buccal hook” (redrawn from Huang 1987: Fig. 7 [in part]). Posterior view (specimen reversed). D, Wear series of upper P4 of Hesperolagomys n. sp. superimposed on graph of occlusal dimensions versus crown height (modified from Bair 2006: Fig. 1:13). Specimens reversed to compare curvature with C; occlusal view above, anterior view below

Figure 1. Extreme wear-related changes to the occlusal surface of upper ch... Available to Purchase

Published: 01 January 2007
, Isolated P4 of old individual of D. pusillis , illustrating tooth curvature and topographically complex occlusal surface with a “buccal hook” (redrawn from Huang 1987 : Fig. 7 [in part]). Posterior view (specimen reversed). D, Wear series of upper P4 of Hesperolagomys n. sp. superimposed on graph
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Figure 2. Quantification of curvature and other shape parameters in test specimens. A, Test specimen images; posterior view of pika P4s and medial view of incisor oriented with outer tooth curvature to the right, wear facet up. Scale bar, 1 mm. B, Outline drawings; same orientation as in A, scaled with outer circles (radii of curvature) of test specimens having the same value. C, Illustration of curvature parameters r1 (radius of outer circle), r2 (radius of inner circle), and d (displacement between circle centers). A is center of outer circle, B is center of inner circle. Actual tooth area indicated by dark gray; potential tooth area as defined by curvature parameters indicated by light gray. Circles defining curvature are oriented so that d is a horizontal line and teeth lie in right half of circle A. D, Additional shape parameters define the wear surface and tooth crown base, defining the location of the tooth within the larger area defined by the curvature parameters. x is the wear surface (wear facet in the incisor, occlusal surface in the cheek teeth). C is the point marking the intersection of the wear surface with the outer circle (A), D is the point marking the intersection of the wear surface with the inner circle (B), and E is the point marking the intersection of the crown base with the outer circle (A). α is the angle between the wear surface and r1 (angle ACD), known as the “wear angle,” which is below r1 in the incisor and above r1 in the cheek teeth in this orientation. η is an angular measure of crown height (angle CAE), or the angle between r1 and the line AE. The test specimen of Hesperolagomys illustrates the special case when point D does not exist in real space, and the wear surface is approximated by line CF when F is the other intersection of x with the outer circle; dashed portion of line x indicates length that extends beyond that of CD at last intersection of D with circle r2 in real space (see text for further explanation)

Figure 2. Quantification of curvature and other shape parameters in test s... Available to Purchase

Published: 01 January 2007
in the cheek teeth in this orientation. η is an angular measure of crown height (angle CAE ), or the angle between r 1 and the line AE. The test specimen of Hesperolagomys illustrates the special case when point D does not exist in real space, and the wear surface is approximated by line CF when F