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ARTICLE Enhancing bonebed mapping with GIS technology using the Danek Bonebed (Upper Cretaceous Horseshoe Canyon Formation, Edmonton, Alberta, Canada) as a case study1 Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by University of Alberta on 12/15/14 For personal use only.
Katherine Bramble, Michael E. Burns, and Philip J. Currie
Abstract: The Danek Bonebed is a monodominant Edmontosaurus bonebed preserving predominantly disarticulated material from the Upper Campanian Horseshoe Canyon Formation within the city limits of Edmonton, Alberta, Canada. To date, at least six dinosaur taxa have been identified at the site: Albertosaurus sarcophagus, Chasmosaurinae indet., Dromaeosauridae indet., Edmontosaurus regalis, Ornithomimidae indet., and Troodontidae indet. This bonebed has been used as a case study for creating a digital, searchable bonebed map using a geographic information system (GIS) platform. The original quarry maps produced on site are refined when digitized with new anatomical information gathered during preparation of collected specimens. Each specimen is labeled with the known specimen identification, quarry coordinates, and catalogue number. Creating a digital map of the bonebed allows easier interpretation of data and the ability to share maps to compare specific elements within the bonebed. Résumé : Le lit a` ossements de Danek est un lit a` ossements monodominant a` Edmontosaurus dans lequel est principalement préservé du matériel désarticulé provenant de la Formation de Horseshoe Canyon du Campanien supérieur, a` l’intérieur des limites de la ville d’Edmonton (Alberta, Canada). À ce jour, pas moins de six taxons de dinosaures ont été identifiés en cet endroit, dont Albertosaurus sarcophagus, Chasmosaurinae indet., Dromaeosauridae indet., Edmontosaurus regalis, Ornithomimidae indet. et Troodontidae indet. Ce lit a` ossements a été utilisé comme étude de cas pour l’élaboration d’une carte numérique consultable d’un lit a` ossements, sur une plateforme de système d’information géographique (SIG). Durant la numérisation des cartes originales des carrières produites sur place, les nouveaux renseignements anatomiques obtenus durant la préparation de spécimens recueillis y sont intégrés. Chaque spécimen est doté d’une étiquette en indiquant l’identification connue, les coordonnées dans la carrière et le numéro dans le catalogue. La création d’une carte numérique du lit a` ossements facilite l’interprétation des données et le partage de cartes afin de comparer des éléments précis au sein du lit a` ossements. [Traduit par le Rédaction]
Introduction Bonebeds provide invaluable data for vertebrate paleontologists as they have the potential to generate significant sample sizes that can contribute information on behaviour, palaeoecology, and paleocommunity structure (Brinkman et al. 2007). A generalized definition of a bonebed is a site that contains an unusually dense concentration of bones representing more than one individual; it may have one or more lithologies (Behrensmeyer 2007). One important aspect of working in bonebeds is documenting the spatial distribution of elements within the assemblage. Digitizing a bonebed map can provide a powerful tool for researchers by allowing more information to be linked to it, such as specimen catalogue information, size ranges, and distribution of taxa represented in the bonebed (Eberth et al. 2007). This linking of data provides a faster facilitation of information and the ease of pulling all available data together with just a click of a button. Digitization also offers the ability to use tools for measuring the length and width of elements, as well as the orientation along the horizontal axis. The Danek Bonebed, located within the city limits of Edmonton, Alberta, Canada (Fig. 1), is a monodominant Edmontosaurus
bonebed preserving predominantly disarticulated material from the Upper Campanian (Upper Cretaceous) Horseshoe Canyon Formation. It was first excavated by the Royal Tyrrell Museum of Palaeontology during the summer of 1989, and again in 1991 (Bell et al. 2010). The University of Alberta Laboratory for Vertebrate Palaeontology reopened the bonebed in 2006 as a teaching site for palaeontology students enrolled in Palaeontology Field School (PALEO400). The university expanded the original quarry and opened two more in the same bonebed. To date, it has produced at least six different dinosaur taxa, and over 600 specimens have been collected and catalogued from this site. The site is assumed to represent a mass mortality event, such as a storm or flood, followed by heavy scavenging and then burial from a fast-moving debris flow (Bell et al. 2010). This bonebed is being used as a case study for the process of digitizing bonebed maps with the pros and cons of using geographic information system (GIS) technology being tested. It will aid in determining the usefulness of converting a regular handdrawn bonebed map into a digital, searchable platform. GIS technology is used in other fields for studies such as environmental analyses (Theophanides et al. 2014), ecological risk assessments (Malekmohammadi and Rahimi Blouchi 2014), predictive habitat
Received 19 June 2014. Accepted 3 July 2014. Paper handled by Associate Editor Andrew Farke. K. Bramble, M.E. Burns, and P.J. Currie. Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada. Corresponding author: Katherine Bramble (e-mail:
[email protected]). 1This article is part of a Special Issue entitled “The Danek Edmontosaurus Bonebed: new insights on the systematics, biogeography, and palaeoecology of Late Cretaceous dinosaur communities”. Can. J. Earth Sci. 51: 987–991 (2014) dx.doi.org/10.1139/cjes-2014-0056
Published at www.nrcresearchpress.com/cjes on 15 December 2014.
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Fig. 1. Locality map of the Danek Bonebed in Edmonton, Alberta, Canada. The white dot on the inset map of Canada represents the location of Edmonton.
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distribution models (Guisan and Zimmermann 2000), and quantifying the impact of human activity on the distribution of diseases or illnesses around the world (Hay et al. 2004). Another application of GIS technology is to document damage to bones (Parkinson et al. 2014). Here, Parkinson et al. (2014) use the GIS spatial analyst component to study bone modifications and their distribution throughout individual bones, with the idea of using this technology to study when carnivores might have accessed the carcasses within the fossil assemblage. This map will use GIS technology in yet another new and innovative way to provide an easy way to share bonebed information.
with new anatomical information after preparation of the collected specimens. The maps created in the field up to the 2013 field season were scanned and uploaded into Adobe Illustrator CS4 14.0.0, where they were oriented and placed according to their relative positions within the quarry. The scanned, hand-drawn specimens were then traced onto the computer using a tablet. The completed digital map was exported to a DWG file and uploaded into ArcMap 10.1 where it was exported into a shape file. This created multiple new files, from which the polyline file was selected and exported from multipart to singlepart using the ArcToolbox. A new field was then created for the polyline file attributes table, labeled UID (unique identifier). A comma separated values (csv) file was created as a master list and merged with the map, which included all of the available data for each element as well as a UID, with the latter being used to tag the information to the correct element. In total, 1702 elements had been found in the bonebed and mapped, but only approximately 600 were collected by the university as many were small fragments. Each element was tagged with its identification and familial assignment, but only the elements collected were tagged with their catalogue number and quarry coordinates. Within the map, elements representing different dinosaur families are colour coordinated to give a visual representation of their distribution. In this version, ceratopsid elements are represented with purple, hadrosaurid elements are blue, ornithomimid elements are grey, dromaeosaurid elements are orange, troodontid elements are black, and tyrannosaurid elements are red. The length, width, and orientation of 405 long bones were measured using the minimum bounding geometry tool within ArcMap 10.1. The csv master list file was set up to identify which elements were to be used by labeling the incomplete or short bones as a 0 and the long or complete bones as a 1 in a separate column. A table with all elements used in this study, including the lengths of 405 long bones obtained using the minimum bounding geometry tool, can be found in the supplementary data2. The digital map is also available within the supplementary data along with a guide for how to use some of the relevant tools in ArcMap 10.1.
Institutional abbreviations
Description
TMP, Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta, Canada; UALVP, University of Alberta Laboratory for Vertebrate Paleontology, Edmonton, Alberta, Canada.
Visual representation The digitized map allows for many ways to look at the data, depending on what information is uploaded into the map. Each element was tagged with its catalogue number, identification, familial assignment, and quarry coordinates, and more information can be added, such as depth of the fossil within the bonebed, strike and dip, whether or not elements have bite marks, etc. This data can then be used to visually express information about the bonebed. In this case study, elements are organized based on their familial assignment, where each family represents a separate layer and is characterized by a different colour. Each layer can be turned on or off if one would like to see only specific layers. For example, only tyrannosaur and dromaeosaur elements can be seen if the ceratopsid, hadrosaurid, ornithomimid, and troodontid layers are turned off. These layers can be based on any category of information within the csv file. Another example would be if the depth of elements within the bonebed is recorded, then the layers could also be chosen to visually represent vertical segregation.
Methods and materials To begin this project, an inventory was made of the collected Danek Bonebed material with specimens from the TMP and UALVP collections. Some of the UALVP material has yet to be found within the collection, or it is in the collection but missing the specimen and quarry information. For the specimens missing quarry coordinates it was not possible to identify them on the map. The bonebed map (Fig. 2) is organized in a two-dimensional grid with the letters A–P signifying 1 m intervals in one direction, and 1–65 signifying 1 m intervals in the perpendicular direction. Elements are mapped relative to a baseline along a heading of 140°– 320° from True North. The baseline cable corresponds to the line running lengthwise on the quarry map. A grid box is moved along the baseline within these intervals to produce the drawings of individual 1 m square sections. The grid box is subdivided into 10 cm2 gradations. As fossils are uncovered, their location and orientation are noted on 1/10th scale paper maps matching their distribution within the grid. The quarry maps are further refined
2
Available tools Using GIS software to create digital bonebed maps opens up the availability of tools that can be used with the map. In this study,
Supplementary data are available with the article through the journal Web site at http://nrcresearchpress.com/doi/suppl/10.1139/cjes-2014-0056. Published by NRC Research Press
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Fig. 2. Map of the Danek Bonebed. Top: an overview of the size and shape of the Danek Bonebed as of the 2013 field season. The line running lengthwise represents the baseline along a heading of 140°–320° from True North. Quarries are labeled with roman numerals. The black rectangle in Quarry II is enlarged and shown in the bottom image, where each square is 1 m2. Within the GIS software, fossils are colour coded by family.
the minimum bounding geometry tool was used to extract the length, width, and orientation of each element. These measurements are possible when the map is properly scaled. In this case study, the information extracted from the minimum bounding geometry tool was used to create rose diagrams. These measurements and orientations were retrieved within a few short moments, which saved time from measuring each individual element on the map by hand. This type of map can also help users locate specific elements within the bonebed by searching for the catalogue number, or for all elements of one kind by using a term such as femur, or any other term within the csv file by using the select by attributes function (Fig. 3). Individual elements may also be clicked on using
the identify features option. This opens a box containing the information collected for the individual element. Geographical or geological base maps may also be added below the bonebed map if they are available at such a fine scale, which was not the case for this study. Here we have a blank background in place of a base map. ArcGIS maps also have the potential to be made available online to share with other users. When uploaded to ArcGIS Online, a link is created to share the map. Viewers may click on the fossils within the online map to show their information; however, the ability to use tools and hide layers is greatly restricted. The online platform allows the potential to compare selected information from different bonebeds. Published by NRC Research Press
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Fig. 3. An example of results if identity = femur is entered into the select by attributes search box. The bolded black elements represent the items within this view labeled as a femur within the csv file.
Discussion This method of using GIS is unusual compared to how it is normally used in the biological sciences, but it works as a great platform to begin manipulating information from a bonebed map. The level of functionality of a GIS map will depend on the information collected in the field and in the preparation laboratory. Any information in the field that is available for each element should be collected, including depth, strike and dip measurements, and quarry coordinates. The extra information collected gives more choices for how to visually segregate the elements in the bonebed. As learned during this case study, it is recommended that in the csv master list the column containing a fossil’s identification only include the minimum information. For example, it should just say whether it is a femur, humerus, metacarpal, etc. If additional information is available, such as whether is it a left, right, juvenile, or fragment, it should be written in a separate column. This will allow the elements to be easily found using the same or similar standard query language (SQL) statement across GIS platforms when searching via select by attributes. The benefit for this type of mapping is that it permits an easy, visual representation of the data. The ability to visually separate bonebed elements based on any criteria of information that has been collected makes the map versatile and easily used in different studies. Digital mapping on this platform also enables all known information for each element to be seen at the click of a button. The tools found within the GIS software can provide ways to measure patterns of association within the bonebed. Finally, using GIS for bonebed maps can give the opportunity to share the maps. However, using this software for bonebed mapping is not without its disadvantages. As with any software package, there is always the chance for the version used to become too outdated and unable to be opened in a newer version. Also, if the map is of an active bonebed, then the map and csv file will need to be kept up-to-date after each field season and revised with the final anatomical shape and size after the fossils have been fully prepared, which could be time consuming. This digital map of the Danek Bonebed aids studies on the bonebed because it makes overall orientation of fossils and distribution of taxa easy to visualize, quantify, and analyze. Maps have
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already been useful for taphonomic studies on other Albertan dinosaur bonebeds (Eberth and Currie 2005, 2010; Ralrick and Tanke 2008), but a searchable, digitized bonebed map can aid researchers even further. By allowing for more information to be linked to the map it provides a more flexible research tool than traditional print maps. This digitization project has also highlighted areas in need of refinement: data collection, cataloguing practices, and updating bonebed maps. Some specimens within the UALVP collections are missing associated data, which makes it impossible to link specimens drawn on the map with those in the collection. As for updating bonebed maps, it has become apparent that maps should be refined to reflect actual measurements, as the drawings made in the field are not always reliable after elements have been prepared. Some measurements taken using the minimum bounding geometry tool in ArcGIS are several centimetres off of the actual measurements due to slightly inaccurate drawings. It is clear that more durable data collection procedures are needed. Future work will include adding almost 100 fossils collected by TMP from Quarry I to the map (the original boundaries of the TMP quarry and map have only been partially defined by recent excavation, and the plaster jackets still need to be prepared), as well as keeping it up-to-date with new fossils and information. Future work will also include looking into more tools that may be available to use for bonebed studies within the GIS software, as well as finding other methods of creating layers within the map to allow for more efficient manipulation of the data.
Acknowledgements The authors would like to thank Charlene Nielsen for the instruction and assistance with ArcMap 10.1 and Brandon Strilisky for providing access to specimens at TMP. Many thanks also to all the students and volunteers who have excavated the Danek Bonebed and prepared its fossils over the years. F Fanti, an anonymous reviewer, and the editors provided helpful reviews that greatly improved this manuscript. The first author received funding from the University of Alberta’s Undergraduate Research Initiative.
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