This page contains the three-dimensional models of tool forms constructed in Chapter 2 of Evans (2003; Evans and Sanson 2003, Biological Journal of the Linnean Society 78, 173-191).

Abstract
This paper addresses the question of how close mammalian teeth are to ideal functional forms. An ‘ideal’ form is a morphology predicted to be the best functional shape according to information of the relationships between shape and function. Deviations from an ideal form are likely to indicate the presence of developmental or genetic constraints on form. Model tools were constructed to conform to functional principles from engineering and dental studies. The final model shapes are very similar to several mammalian tooth forms (carnassial teeth and tribosphenic-like cusps), suggesting that these tooth forms very closely approach ideal functional forms. Further evidence that these tooth forms are close to ideal comes from the conservation over 140 million years, the independent derivation and/or the occurrence over a size range of several orders of magnitude of these basic tooth forms. One of the main functional shapes derived here is the ‘protoconoid’, a fundamental design for double-bladed tools that fits a large number of functional parameters. This shape occurs in tooth forms such as tribosphenic, dilambdodont and zalambdodont. This study extends our understanding of constraints on tooth shape in terms of geometry (how space influences tooth shape) and function (how teeth divide food).

Additional key words: dentition – functional morphology – tooth modelling – carnassial – protoconoid – VRML reconstruction

3-D Models

A VRML browser is required to view the .wrl files on this page. VRML browser plug-ins for Netscape and Internet Explorer: PC (CosmoPlayer); Mac (Cortona).

Instructions for how to use CosmoPlayer.

The following conventions are used in the models on this page:
     Lower tool: yellow
     Upper tool: blue
     Blade(s): red edge
     Lower tool moves upwards to upper tool, and upper tool remains stationary.
     Movement of lower tool in basic models can be toggled by clicking the lower tool.

Single-bladed Tool Forms
 
 

Three-dimensional model of two basic single-bladed tools in occlusion. The basic single-bladed tool has a single blade with 0º rake, 0º relief, 0º approach angle, and moves vertically. The blade on each tool is represented by the red edge, and each blade occludes with a blade on another tool. Click on the lower tool to toggle movement, illustrating occlusion between the tools. Use 'Viewpoint List' to view from different directions. Full page		Three of the shape parameters are altered: the angle of the leading and trailing surfaces and blade edge arrangement. Each tool can be viewed using the 'Viewpoint List'. A, B, C are Apices A, B and C respectively; LSA, leading surface angle; TSA, trailing surface angle. Full page

Derived single-bladed tool forms
 

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Alistair Evans, May 2003