Increasingly, paleontologists are able to exploit technology to aid in visualizing extinct life. For example, three-dimensional (3D) computed tomography (CT) techniques have been applied to determine the external form of embedded fossils (Torres 1999), as well as to develop a digitally rendered endocast model of a Tyrannosaurus rex (Brochu 2000). Models of conodonts have also been generated by applying Virtual Reality Markup Language (VRML) to predict the geometry of bedding plane arrangements (MacRae 1995). Finally, a combination of QuickTime VR and scanning electron microscopic methods have been utilized to image microfossils (Lyons et al. 1998). Three-dimensional modeling is not new to the field of paleontology though.
Alcide d'Orbigny in 1826 (d'Orbigny 1843) made some of the first 3D models of fist-sized reproductions of microscopic foraminifera. However, the most famous early models were certainly the life-size interpretations of Iguanodon, Hylaeosaurus, Megalosaurus, Plesiosaurus and Ichthyosaurus sculpted by Benjamin Hawkins in 1853 for the International Exhibition. After the exhibition closed the dinosaur models were subsequently moved to Sydenham Park in South London (Spalding 1993).
Traditionally, if a fossil important to the paleontological community is discovered, the resultant research publication is usually accompanied by appropriate illustrations. If this work is built upon, other researchers will either have the specimen sent to their institution or will visit the institution where the specimen is archived to examine the specimen. Although traditional modelling techniques (e.g., plaster or fiberglass casting) will undoubtedly remain popular and relevant for some time to come, there are real advantages in using digital methodologies for research purposes. The benefit of utilizing a digital model versus the actual fossil, or a traditional reproduction, is the potential to share and carry out research on fossils with colleagues over great distances quickly and cheaply with no danger to the original material. Shape analysis, as well as soft and hard tissue reconstruction can all be done easily within the digital realm. Hard copies of the digital model can also be produced using rapid prototyping machines (mechanical devices used to turn 3D computer-generated designs into production prototypes). These instruments permit the production of highly accurate models with a level of detail and accuracy far exceeding those typical of traditional casts (Beraldin et al. 1997).
Other uses of high-resolution 3D laser scanners, as applied to fossil material, include the ability to provide external surfaces (e.g., biomedical application such as imaging and reconstruction of brains. Wallace 1999) and creation of a collection of digital reconstructions that would allow for a comparison of surface structures across similar species.
Three-dimensional laser scanners have been in limited use since their development by the National Research Council of Canada in 1981. However, it is only within the last three years that these scanners have become more prevalent and accessible to researchers and engineers through commercial development of the technology. As high-resolution (<100µm) laser scanners become commercially available, they represent a unique opportunity to image fossil material. Three-dimensional laser scanners have already been applied in such diverse applications as documenting archaeological artifacts from The Canadian Museum of Civilization (Rioux 1994), documenting archaeological digs (Boulanger et al. 1998), using reverse engineering (a process by which an object is scanned in three dimensions and then reconstructed physically with either rapid prototyping machines or automated lathes (Godin et al.1996), and determining the authenticity of artwork (Baribeau et al. 1992).
Work by other paleontological researchers has used less sophisticated 3D scanning technology, including low-resolution (>500µm) point scanners to produce an animated Triceratops sp. in locomotion studies (Andersen et al. 1999). Even lower-resolution laser scanners have been used in modeling the morphology of a variety of vertebrate fossil material (Chapman 1997). To the best of our knowledge, though, high-resolution laser scanners have not been applied to paleontological research.
In this article we present and explore a new technique for the 3D modeling of macrofossil material from a mosasaur. This technique utilizes a high-resolution 3D laser scanner to capture a series of positional coordinates (x, y, z).
Mosasaurs are an extinct group of marine reptiles that were most diverse and abundant through the latter half of the Cretaceous, and like other groups of marine reptiles became extinct at the K-T boundary (Russell 1967). They reached immense sizes, up to 10 meters in length, and are well-known from many recovered specimens, but relatively few juveniles have been found (Caldwell 1996). From braincase material of a mosasaur in the collections of the Canadian Museum of Nature, the basisphenoid-basioccipital (#51259) of a juvenile Tylosaurus sp. was completely imaged by the 3D laser scanning technique at a resolution of 100 µm. The basisphenoid-basioccipital is located at the base of the skull and is one of several bones that form the braincase in vertebrates. These bones support and protect the brain.
Although paleontologists often depend heavily on the physical features when interpreting specimens, several questions must be answered if this technique is to prove viable in providing accurate digital models fit for paleontological study. Thus, primary aims of this paper are to determine whether a digital model scanned at 100 µm is accurate enough for paleontological study and whether available compression methods used to make such models more easily accessible with desk-top computers reduce the scientific value of the digital model by obscuring or even deleting important features.