Special Volume - Number 13, Sept 2014

Symposium Volume

Conveners

Sandra Val Steven J. Jabo Vicen Carrió

Edited by Emanuel Tschopp & Sandra Val

Additional Scientific Editors Koen Stein, Carla Alexandra Tomás, Ricardo Araújo, Octávio Mateus, Peter Falkingham & Rui Castanhinha

Technical Editors Silvia Costa, Emanuel Tschopp, Femke Holwerda

www.jpaleontologicaltechniques.org ISSN: 1646-5806 Number 13 Sept 2014

PREPARATION OF A TURTLE FOSSIL FROM THE PLIOCENE SITE OF CAMP DELS NINOTS (CALDES DE MALAVELLA, GIRONA, SPAIN)

Souhila Roubach1,2, Bruno Gómez de Soler1,2, Gerard Campeny Vall-Llosera1,2, Juan Ignacio Morales1,2

1- Àrea de Prehistòria, Universitat Rovira i Virgili, Tarragona, Spain 2- IPHES, Institut Català de Paleoecología Humana i Evolució Social, Tarragona, Spain Email: [email protected]

ABSTRACT

In order to handle fossils for study and exhibition, a good state of conservation is paramount. In this work, the conservation operations carried out on a turtle fossil, described as Mauremys leprosa from the Pliocene site of Camp dels Ninots (Caldes de Malavella, Girona, Spain), are reported and documented. Cleaning, consolidation and preparation of the fossil was carried out, both on site and in laboratory. In particular, this work displays the interest of combining traditional conservation techniques with modern procedures such as 3D scanning. It is shown that the combination of 3D scanning and silicon moulding/casting can be extremely useful in order to document and preserve the anatomical connection of the fossils, especially when such fossils are embedded in fragile laminated or cracked sediment.

Keywords: 3D scanning, Camp dels Ninots (site), conservation, Pliocene, preparation methods, turtle fossil

RESUMO [in Portuguese]

No manuseamento de fósseis para estudo e exposição, um bom estado de conservação é crucial. Neste trabalho, as operações de conservação desenvolvidas numa tartaruga fóssil, descrita como Mauremys leprosa da jazida Pliocénica de Camp dels Ninits (Caldes de Malavella, Girona, Spain), são reportadas e documentadas. Limpeza, consolidação e preparação do fóssil foram feitas, tanto na jazida como no laboratório. Em particular, este trabalho mostra o interesse da combinação de técnicas de conservação tradicionais com procedimentos modernos, como a digitalização 3D. É mostrado que a combinação da digitalização 3D e moldagem em silicone pode ser extremamente útil de modo a documentar e preservar a conexão anatómica dos fósseis, especialmente quando esses fósseis se encontram em sedimentos extremamente frágeis ou fracturados.

How to cite this article: Roubach, S., Gomez de Soler, B., Campeny, G.V. and Morales, J.I., 2014. Preparation of a turtle fossil from the Pliocene site of Camp dels Ninots (Caldes de Malavella, Girona, Spain). Journal of Paleontological Techniques, 13: 38-49.

Copyright (c) 2014 by Roubach et al. This work is made available under the terms of the Creative Commons Attribution 3.0 Unported License, http://creativecommons.org/licenses/by-sa/3.0/.

www.jpaleontologicaltechniques.org ISSN: 1646-5806 Roubach et al., 2014: PREPARATION OF TURTLE FOSSIL

INTRODUCTION comprises more than 50 well preserved monogenetic cones and some others with both explosive and non-explosive activity phases Paleontological studies contribute to identify (detailed references available in Gómez de and determine species evolution and Soler et al. 2012). It is a volcano maar-type chronology, as well as the interactions with site, formed by phreatomagmatic explosions. other species and with their environment. These explosions resulted from brief, near- Therefore, good conservation of fossils is surface magma/water interactions occurring crucial for their manipulation and/or exhibition. during the ascent of magma towards the However, specimens are often highly fragile surface which in turn led to violent explosions. when discovered and such fossils often require The presence of groundwater led to the a certain level of maintenance to give them development of a lake inside the crater. The strength and shock resilience. In this work, the sedimentary infill is characterized by typical preparation processes carried out, both in situ vertical stratigraphic succession in maars and in laboratory, on one case of turtle fossil (Pirrung et al., 2003; Lindner et al., 2006). from the Pliocene site of Camp dels Ninots is Syn-/post-eruptive wall rock debris and presented. pyroclastic breccias characterize the bottom The Camp dels Ninots maar site is located in deposits and are followed by a fining-upwards Caldes de Malavella, Girona, NE Spain. Its sequence of lacustrine muds with coarse layers coordinates UTM31N (ETRS89) are 483202 E and final shallow lake deposits (Figure 2). The and 4631454 N (Figure 1A). The Camp dels site has been recently classified as a Konservat- Ninots volcano is a part of the Catalan Volcanic Lagerstätte (Gómez de Soler et al., 2012), and Complex which took place between 14 Ma and the stratigraphy shows a lacustrine 10 Ka in NE Spain (Gómez de Soler et al., sedimentation in a maar, which are ideal 2012). The basaltic monogenetic volcanic zone conditions for the preservation of fossils.

Figure 1: Location of Camp dels Ninots site in Spain and north east Catalunya (A) and map of the Can Argilera sector (B).

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Ninots site (Gomez-Merino et al., 2009), as well as consolidation tests of macroflora (fossil leaves), preserved as impressions in lacustrine clays (López-Polín et al., 2009). Turtles from the Camp dels Ninots site are freshwater reptiles (Mauremys leprosa). The species distribution consists of the Iberian Peninsula and the Maghreb Region of north- west Africa (Fritz et al., 2006). M. leprosa of Camp dels Ninots constitute one of the oldest record in Europe of these species (Gómez de Soler et al., 2012).

MATERIAL AND METHODS

The turtle fossil (CN’10-Pit7/8-Niv11-M18-nº2) was discovered at level 11 of the Can Argilera sector (Figure 1B), during the 2010 excavation campaign. The units covering the fossil were greenish laminated clays with sandstones (Figure 2). The turtle fossil appeared complete and in anatomical connection, with the posterior and anterior phalanges located outside the body. Such spatial disposition is a rare occurrence, since in most recovered fossils the phalanges are retracted inside the shell. This fossil is therefore very interesting to document precisely the anatomy of this species. However, Figure 2: Detailed stratigraphy of the Camp dels Ninots site bones presented splits, cracks, and were friable (adapted from Gómez de Soler et al., 2012). in some parts (particularly when the bone and sediment were dry). It is noteworthy as well that most of the fossils were flattened because of diagenetic processes. As such, the turtle A large range of skeletons (mammals, fossil was in need of an in-depth preparation in amphibians, freshwater fishes, and reptiles) situ and in the laboratory later on. have been recovered, most of them articulated (for more details, please see: Gómez de Soler et al., 2012; Jiménez-Moreno et al., 2013; In situ treatments Campeny et al., 2012, 2013; Gómez de Soler et al., 2014). In terms of flora, both pollen and Excavation, cleaning and consolidation macroscopic remains have been found. The When the fossil appeared, the general surface landscape is characterized by forested was delimited with a small trowel and a brush. vegetation (featuring a forest ratio between Then, the bones were excavated superficially 57% and 97 %, based on pollen analysis; from sediment and cleaned using wooden Jiménez-Moreno et al., 2013). The correlation and/or metallic instruments (like scalpels, awls, of paleomagnetic and pollen results with the etc.). The fragile bones were consolidated with referred paleontological data gives the Camp Paraloid B72 at 5 to 10% in acetone (applied dels Ninots site a date ranging from 3.3 to 3.1 with a syringe). Ma (with the sedimentary sequence deposited in 200 kyr) (Gómez de Soler et al., 2012; Extraction Jiménez-Moreno et al., 2013). Previous For storage and preparation purposes, the published works report the conservation and fossil was extracted in its sediment block with a storage of a bovid skull from the Camp dels polyurethane support. The surface to extract

40 ● Journal of Paleontological Techniques Roubach et al., 2014: PREPARATION OF TURTLE FOSSIL was demarcated with a trowel, and then (Figure 3). When the chemical reaction was covered with aluminium foil. Then, a cardboard finished and the polyurethane cold, the block support was constructed in order to contain the was extracted and turned upside down. The sediment block and polyurethane. The sediment of the underside was then also polyurethane (polyol and isocyanate) was covered with polyurethane. mixed and poured inside the cardboard support

Figure 3: Turtle fossil (CN’10-Pit7/8-Niv11-M18-nº2). A) preservation state in situ; B-F) extraction process featuring fossil protection (B-C), cardboard container fabrication (D) and polyurethane pouring (E-F).

Treatments in laboratory (Figure 4A). The sediment was excavated until the extents of the fossil were exposed (Figure Excavation and cleaning 4B). Some of the bones presented cracks and The preparation started on the upper part of splits and were fragile (the superior and inferior the fossil, by the removal of the polyurethane parts of the fossil, and the cranium). Hence,

41 ● Journal of Paleontological Techniques Roubach et al., 2014: PREPARATION OF TURTLE FOSSIL the cleaning was carried out carefully with thin with acetone: a cotton swab was soaked in metallic and wooden awls, needles, and acetone and was applied to the bone surface brushes. The bones were subsequently cleaned with a circular movement (Figure 4C).

Figure 4: Preparation process of the superior part. Excavation (A-B) and cleaning (C), followed by consolidation (D).

Consolidation treatments laminations and cracks became larger with During the drying process, the cracked, fragile, time, affecteding the stability and anatomical and friable bones were consolidated with connection of the small bones (particularly the Paraloid B72 at 5 to 15% in acetone (applied phalanges located outside the body). Therefore, with a syringe) (Figure 4D). The fractured in order to control the sediment alteration, bones were also joined with the same consolidation tests were carried out by injecting consolidant using higher concentration (50 % different consolidants into the sediment cracks up to 80%). In order to account for the fragility (e.g. Beva 371 in 372 solvent). However, these of the fossil, consolidation and cleaning were tests were not fully conclusive and require applied simultaneously. further investigation. The alternative solution During the preparation of the superior part, a found to temporarily keep the small bones serious problem was encountered: the articulated during the preparation process of sediment altered when drying and presented the fossil was to use paste filler (Modostuc) to horizontal lamination and cracks. The replace the sediment between the small bones.

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Figure 5: 3D scan; A-B): superior part; C): inferior part.

3D scan Silicon mould Due to the lack of a satisfying permanent and However, 3D scanning with the current reversible procedure which would maintain the technology lacks some precision compared to articulation of the specimen, it was decided to moulds in the angled regions of the fossil (e.g. dislocate the bone phalanges after the phalanges and between the cranium and the preparation process. Hence, for the first time at carapace). In order to record this the Camp dels Ninots site, a 3D scan was morphological information, a silicon mould was carried out in order to document the original also made using a two part poured mould with state of the fossil before the separation of the plaster jacket (mother mould) method (Smith small bones (phalanges). A Breuckmann and Latimer, 1989; David and Desclaux, 1992). smartSCAN 3D-HE mounted with a 250mm FOV First, the plaster jacket had to be was used to create a 3D model of the turtle manufactured. Protected by a plastic film, the fossil, and the obtained mesh was processed fossil was covered with plasticine in order to using Breuckmann Optocat 2012R2 and follow the fossil shape without flattening it too Geomagic Studio 2013 software packages. The much on the bone. Two posts of plasticine were data points acquired were more than 3.5 million constructed in the top part and joined by triangles for each surface of the fossil, plasticine bands, and small keys were also corresponding to a resolution of 4729 constructed around the fossil. To avoid the points/cm2/cm, equivalent to ca. 0.14 mm coating of plaster in plasticine, a layer of spacing between points. It is noteworthy that Vaseline was applied with brush. Then, a the resolution is reduced in (Figures 5A, 5B) for mixture of plaster-water was applied to form visualization purposes. the jacket. Once the plaster got dry, the support, plasticine and plastic film were

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Figure 6: Silicon mould fabrication and preparation process for the fossil superior part. removed from the fossil. The turtle fossil was cleaning and consolidation was applied, using protected by a separator spray (Molykote). The the same instruments (metallic and wood awls, jacket was put again on the fossil and the needles, brush) and products (acetone, silicone (Silastic 3481/curetting agent 81- 5%) Paraloid B72 at 5, 10 and 80 % in acetone) poured slowly inside the plaster jacket through as for the superior part (Figure 7). one of the two holes formed by the plasticine When the preparation of the inferior part of the posts (Figure 6). fossil turtle was finished, the 3D scan Once the silicon dried, the mould was turned (Figure 5C) and silicon mould of this part over and the inferior side of the turtle fossil (Figure 8) were carried out using the methods excavated. The same process of excavation, applied for the superior part.

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Figure 7: Preparation process of the inferior part: excavation (A-B), cleaning (C-D), and consolidation (E-F).

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Figure 8: Silicon mould and preparation process of the inferior part.

Casting applied on the replica surface to complete the Subsequently, a cast was made with an acrylic process (Figure 9). resin (Acrystal prima 100pp+ Acrystal basic 250pp). The replica was painted using a DISCUSSION mixture of natural pigment with alcohol and retouch varnish. In order to obtain a color The preparation of the turtle fossil in situ was similar to the sediment, white, black, yellow carried out in order to give it resistance for and blue natural pigment were mixed; for the extraction, transport, and for manipulation fossil bones color, a brown natural pigment was (especially when it is turned upside down). used. A layer of retouch varnish was also Polyurethane protects and gives resistance to

46 ● Journal of Paleontological Techniques Roubach et al., 2014: PREPARATION OF TURTLE FOSSIL the fossils during transport and short time adhesive at the same time minimizes the storage; this method of extraction also allows number of products applied, leading to a better maintaining the sediment humidity, leading to control on the paleontological preparation much easier laboratory work. process. Paraloid gives good results in the We used Paraloid B72 for all preparation bones preservation, and the good preparation processes because of its stability and efficiency of the fossils allows manipulating them for both (Howie, 1984; Horie, 1987; Johnson, 2001). study and exhibition. The use of one product as consolidant and

Figure 9: Cast process. A-B) resin preparation; obtained replica during (C) and after (D) painting.

With laminate materials such as the sediment during the preparation. The main advantage of found in the Camp dels Ninots site, it is very 3D scanning is that it is a non destructive difficult to keep the bones articulated. Another technique, which can be applied even on very way could be to use the so-called Transfer fragile materials. It is also relatively fast, easy method (Schaal, 2005). It consists in the to use, can be used in situ (portable preparation of one side of the fossil, which is apparatus), and does not require physical then covered with artificial resin. After storage space. Its main drawbacks are the lack hardening of this artificial substrate, the other of precision especially in the angled parts of the side of the specimen is prepared. However, the fossil, and the high price of the apparatus. On reversibility would be sacrificed in that case. the other hand, Silicon molding is a more Without a reversible procedure to maintain established technique and is more precise than articulation, it was decided to dislocate the 3D scanning under its current form. However, it small bone extremities. That decision led to the is a much slower and potentially dangerous use of the 3D scanning technique to document technique on fragile fossils such as the one the original features of the fossil before and considered in this work. It requires the use of

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products to fix and consolidate the fossil articulation of the fossils are documented and beforehand. The combined use of 3D scanning preserved. The importance and the and silicon moulding allows obtaining a good preservation state of the fossil are leading to trade-off, since the original state of the fossil is the choice of the conservation actions. Hence, captured by 3D scanning. Regarding final the interventions carried out on the turtle fossil storage, the turtle fossil and the replica are allow applying different conservation methods packed in plastic boxes inside polyethylene for the same specimen and featuring a greater support (Ethafoam). This material exhibits a versatility: the fossils preparation can be tuned certain number of advantages such as stability, depending on their preservation state and on cleanliness, compactness, and ease of use. the final goal of their study. The result is two Digital files are stored on a server in .ply and duplications of the specimen; one digital, and .stl format (note: this file is also provided with one physical. The former is safe, and easily this manuscript and has been optimized for stored, albeit with lower resolution, while the web viewing at 63p/cm2/cm, equivalent to ca. latter risks damage or disarticulation of the 0.14 mm spacing between points). specimen, but provides a higher fidelity cast and physical record.

CONCLUSIONS ACKNOWLEDGMENTS

In this work, the conservation operations We would like to thank the land owners for carried out on a turtle fossil, described as their permission to work in the area, as well as Mauremys leprosa from the Pliocene site of all those who have participated in the Camp dels Ninots (Caldes de Malavella, Girona, fieldwork. The Camp dels Ninots project has Spain), are reported and documented. benefited from contributions from the Town Cleaning, consolidation, and preparation of the Council of Caldes de Malavella and the fossil were carried out both on site and in the Departament de Cultura i Mitjans de laboratory. The fossil was cleaned with small Comunicació de la Generalitat de Catalunya. and thin instruments, and then consolidated We would like to thank also the Agencia with paraloid B72 at 5% up to 15% in acetone. Española de Cooperación International y With the laminated sediment found in the Desarrollo MAEC/AECID for the financial Camp dels Ninots site, it is very difficult to support of S. Roubach’s PhD studies. J.I. keep the bones articulated during the Morales, beneficiary of a predoctoral research preparation process. Silicon moulding requires fellowship (FI) from the AGAUR of Generalitat the use of products to fix and consolidate the de Catalunya (FI-DGR 2013), is also fossil beforehand, and these should be acknowledged. The authors also received reversible. Moulding is also potentially support from projects CGL2012-38358, dangerous with fragile fossils. Therefore, 3D CGL2012-38434-C03-03, and SGR2009-324 of scanning was carried out on the fossil material the Ministerio de Economía y Competividad of in combination with silicon molding for both the Spain and Generalitat de Catalunya. superior and the inferior part. That way, the

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