UC Davis IDAV Publications

Title Possibilities and limitations of three dimensional retrodeformation of a trilobite and plesiosaur vertebrae

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Authors Motani, Ryosuke Amenta, Nina Wiley, David F.

Publication Date 2005

Peer reviewed

eScholarship.org Powered by the California Digital Library University of California Nortfr American Pafeontofogy Convention DalhousieUniversity, Halifax, NovaScotia CANADA June lg-25,2005

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NAPC 2OO5 PaleoBios MUSEUMOF PALEONTOLOGY UNIVERSITYOF CALIFORNIA,BERKELEY

Volume25, Supplement to number2 ISSN0031-0298 June20, 2005 NAPC2005- PaoeaeunloAaslRncls 88

the question arisesas to whether or not there symmetrical pairs of landmarks to calculate the were potentially new life modes available for three-bythree symmetric matrix that represents opportunisticmicrobes. The answeris yes, and the linear strains. Assumptionswere madethat: in particularit appearsthat calcium carbonate (1) the original animal was bilaterally number exoskeletonsof bryozoans,if not other symmetricalon average;(2) a sufficient (3) invertebrates,provided substrateopportunities. of landmarks are available; and the Other invertebrateswith similar exoskeletons deformation was linear. The results exposed could serve as alternative substrates. The difficulties causedby the violation of the three advantagesare increasingsurface areas for assumptions.First, animalscan be very incrustingand providing a variety of substrates asymmetrical:it is necessaryto identiff the more abovethe sediment-waterinterface. Our symmetricalparts of the animal and limit the preliminary studies show that the bryozoan datacollection to theseareas. Second,the exoskeletonsupport a gardenofmicroflora that number of landmark pairs neededto find the includesfilaments, diatoms, coccoliths, bacilli matrix can be quite large. The theoretical and cocci morphotypes,and extensivedeposits minimum is five pairs,but many more are of biofilm. The microbesfossilize in a similar neededbecause ofthe inherentredundancy manner to those found on the surfacesof rocks amongpairs. In the caseof the trilobite, eleven there and other sediments.The fossilizedforms pairs turnedout to be insufficient. Third, much indicatethe presenceof the following ions: Ca' are too many alternativesolutions without nearly Mg, Fe,Al, with lesserlevels of K and P. differencein symmetryscores. Therefore, Microbialroles have changed, and as the Earth symmetricalreconstruction of the originalanimal evolves,opportunistic microbes will adapt. with incorrectlengthiwidth/height ratios could easily misleadresearchers. With care,however, POSSIBILITIESAND LIMITATIONS OF it was possibleto retrodeformall the specimens. THREE DIMENSIONAL The methodwill be madeavailable in a software RETRODEFORMATIONOF A TRILOBITE package,including a 3D landmarkeditor which AND PLESIOSAURVERTEBRAE canalso be usedfor morphometricstudies.

OF MOTANI, Ryosuker;Amenta, Nina:: WileY, THE EARLY EVOLUTIONARY HISTORY Davids THE EUREPTILIA (AMNIOTA, REPTILIA)

rUniversityof California,Davis, Geology Dept, MUELLER, Johannesr One ShieldsAvenue, Davis, California,956l6, 2Dept. rDept. USA; ComputerSciences, UC Davis, of Biology, University of Toronto at 3lnstitute Davis, Caiifornia, 95616,USA; for Mississauga,3359 Mississar.rga Rd. N., Data Analysis and Visualization,UC Davis, Mississauga,ON, L5L lC6, Canada Davis,California, 95616, USA Besidesthe Synapsidaand the Parareptilia,the Three-dimensionalfossils have often been Eureptiliaform the third major cladeof the as deformedduring preservation' Such defonnatton Amniota and includepopular animals such usually causespronounced asymmetry, which dinosaurs,birds, crocodiles,or snakes.Their could bias the outcomeof morphometricstudies. early evolutionaryhistory, however,is only It is thereforedesirable to removethe distortions poorly understood.Early eureptilescan be probably by a geologicaldeformation model' This subdividedinto the Captorhinidae,the process,called retrodeformation,has been paraphyleticProtorothyrididae, and the basal practicedtwo-dimensionally by previous diapsidclade Araeoscelidia. A problem of this workers.We exploredthe possibrlitiesof classificationis that it is mainly basedon very few expandingthe model to threedimensions. cladisticanalyses that incltrdedonly a We usedone individual of the trilobite Phacops eureptilianrepresentatives. Thus, we are only rana and I I cervicalvertebrae ofthe poorly informed aboutthe more detailed we elasmosauridplesiosaur Thalassomedon relationshipsof basaleureptiles, and do indeed haningtonifor our study. All specimens currentlynot know ifprotorothyridids are if all apparentlyhad simple distortion,i.e., closerto diapsidsthan to captorhinids,or homogeneouscompression and,/or expansion that the taxa designatedas eureptilesdo evenbelong can be modeledby a linear transformation.We to this clade.Recent research on the early the collectedcoordinate data from the laterally Eureptiliaincluded the new descriptionof