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Neck mobility, Grazing habits, and intraspecific combat behaviour in the Giant Pleistocene horned Turtle Meiolania Platyceps
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
2015 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Meiolania platyceps is the stratigraphically youngest, and osteologically best-known members of the enigmatic Paleogene-Holocene testudinatan clade Meiolaniidae. This study generated digital reconstructions of intervertebral mobility using the complete cervical series of M. platyceps as a functional model for inferring feeding habits in giant meiolaniid taxa. A combined photogrammetric and CT data approach was used to compile surface meshes for each individual vertebra, which were then scaled, articulated, and animated to visualise maximal movement through segments radiating from the dorsoventral and mediolateral planes. The results show that M. platyceps was incapable of any kind of neck retraction, which is not surprising given the massive skull and prong-like squamosal horns. In addition, impeded dorsal flexibility via the vertebral processes and projecting anterior margin of the carapace suggests that browsing would have been difficult. Indeed, the neck of M. platyceps was best capable of downward mobility allowing the skull to tilt forward. This presumably brought the muzzle into a grazing position and allowed the animal to feed upon low growing herbaceous vegetation, ferns and palm fruits. Because of the insularity and the skull configuration of this aberrant turtle, an intraspecific combat behaviour has also been suggested in the reconstruction of the lifestyle of M. platyceps

Abstract [sv]

Meiolania platyceps, en stor behornad sköldpadda som levde under Pleistocen, är en av de yngsta och osteologiskt mest välkända medlemmarna av den enigmatiska Paleogen-Holocena gruppen av testudinata sköldpaddor, dit familjen Meiolaniidae hör. Genom att digitalt rekonstruera exemplarets kompletta nacke, inklusive samtliga halsryggens kotor, kunde artens matvanor såväl som dess potentiella stridsbeteende mellan individer inom arten beskrivas. De individuella kotorna fogades samman genom att kombinera fotogrammetri med CT-data, och efter att ha justerat deras respektive storlekar samt artikulerat dem kunde kotornas maximala rörelsevidd animeras såväl dorsoventralt som mediolateralt. Den mjukvaran som användes för detta var framförallt 3D Studio Max, dock i mindre utsträckning även Agisoft Photoscan Geomagic. Resultatet från de 3D-modeller som genererats i denna undersökning stöder hypotesen att M. platyceps saknade förmågan att dra in dess huvud och hals i skalet, vilket inte är helt överraskande med tanke på dess massiva skalle och utstickande squamosala horn. Skillnaden i hur nacken böjs ventralt jämfört med dorsalt tyder dock på att denna sköldpaddas betningstekniker varit desto mer utvecklade, särskilt eftersom vegetationen under denna tid bestod till största delen av palmer. Skallens position och konfiguration hos detta märkliga djur ger ytterligare information om artens beteende, och det verkar som att intraspecifika slagsmål kan ha förekommit hos M. platyceps

Abstract [fr]

Meiolania platyceps est l’un des derniers et mieux connus membre de l’énigmatique clade des Meiolaniidae de la période du Paléogène-Holocène. Notre étude fut de générer des reconstructions digitales de la mobilité intervertébrale en utilisant la série complète de cervicales de M. platyceps en tant que modèle fonctionnel afin d’inférer le comportement alimentaires du taxon des meiolanides. Une combinaison de données photogrammétriques et de scannes fut utilisée afin de compiler des surfaces en 3D pour chaque vertèbre, mises à l’échelle, articulées et animées afin de visualiser les mouvements optimaux selon les plans dorsoventral et mediolateral. Les résultats montrent nettement que M. platyceps était incapable de rétracter son cou, ce qui n’est pas surprenant considérant sa tête massive et ses impressionnantes cornes. Qui plus est, la flexibilité dorsale, entravée par les apophyses vertébrales et la marge antérieure de la carapace, suggère que le « browsing » aurait été difficile. En effet, le cou de M. platyceps était mieux à même d’une mobilité ventrale permettant au crâne de basculer vers l'avant. Ce qui aurait entraîné le museau dans une position de « grazing » et aurait permis à l’animal de se nourrir de végétation herbacée, de fougères et de fruits de palmiers. En raison de l'insularité et de la configuration du crâne de cette tortue aberrante, un comportement de combat intraspécifique a également été suggéré dans la reconstruction de la vie de M. platyceps

Place, publisher, year, edition, pages
2015. , 72 p.
Series
Examensarbete vid Institutionen för geovetenskaper, ISSN 1650-6553 ; 305
Keyword [en]
Testudinata, neck retraction, cervical vertebrae, Photogrammetry, 3D modelling
Keyword [fr]
Testudinata, rétraction du cou, vertèbres cervicales, Photogrammétrie, Modélisation 3D
Keyword [sv]
Testudinata, hals indragning, halskotor, fotogrammetri, 3D-modellering
National Category
Other Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:uu:diva-243223OAI: oai:DiVA.org:uu-243223DiVA: diva2:787557
Educational program
Master Programme in Earth Science
Presentation
2014-06-04, Department of Earth Sciences Palaeobiology Villavägen 16 SE-752 36, Uppsala, 14:36 (English)
Supervisors
Examiners
Available from: 2015-02-12 Created: 2015-02-05 Last updated: 2015-02-12Bibliographically approved

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