Quantifying Dental Complexity How, and Why? - Otto Stenberg, MSc. Jernvall Lab, BI University of Helsinki - Studies

Quantifying Dental Complexity
                                   How, and Why?

Otto Stenberg, MSc.
Jernvall Lab, BI
University of Helsinki
otto.stenberg@helsinki.fi
                                                       LSI Guest Lecture
   @PaleoOtto
                                                                   2020

“Teeth are at the direct interface between an organism and its environment”
                                                            ~ Cuozzo et al. (2012)

Tooth shape

 A trait strongly determined by genetics – high heritability

 Mammal teeth have complex surfaces for processing food items

                                        Popular in EvoDevo & Paleontology

Tooth shape - mirroring diet

        Hypercarnivore         Omnivore
           • Few features        • Many features
           • Shearing edges      • Crushing cusps
           • Low complexity      • High complexity

Tooth shape - mirroring diet

        Hypercarnivore                 Omnivore
           • Few features                • Many features
           • Shearing edges              • Crushing cusps
           • Low complexity              • High complexity
           • Reduced # molars

                         …but how to quantify shape?

Measures of shape

Old School:
• Counting and classifying shapes “by hand”
   • Cusp types, locations
   • Edge maps
      → Crown types, combining these two

Measures of shape

     Old School:
     • Counting and classifying shapes “by hand”
        • Cusp types, locations
        • Edge maps
           → Crown types, combining these two

         • Misc. indexes in paleo and
           anthropology

Measurement of the primate tooth,
used in calculating dieatary indexes
(Kay 1975)

Measures of shape

                                       Dental topographic analysis

                                          • Ratio of 3D area vs. 2D are: RFI

3D scans in calculating Relief Index
        (Boyer et al. 2008)

Measures of shape

                                  Dental topographic analysis

                                     • Ratio of 3D area vs. 2D are: RFI

                                     • Through curvature: DNE

Dirichlet Normal Surface Energy
(Bunn et al. 2011)

Measures of shape

                                     Dental topographic analysis

                                        • Ratio of 3D area vs. 2D are: RFI

                                        • Through curvature: DNE

                                        • Orientation Patch Count

                                           → Predicts diet in carnivorans / rodents!

Height maps & OPC of two dietary
categories in Rodentia & Carnivora
(Evans et al. 2007)

Orientation Patch Count

               OPC:
                8

               OPC:
               802

Adaptive radiation of multituberculate
mammals before the extinction of
dinosaurs. (Wilson et al. 2012)           Orientation Patch Count

                                         • Reconstruction of diets in paleoecology

Height maps & OPC of two dietary
categories in Rodentia & Carnivora
        (Evans et al. 2007)

The    Evolution   on    High   Dental
Complexity in the Horse Lineage (Evans
& Janis 2014)                             Orientation Patch Count

                                         • Reconstruction of diets in palaeoecology

                                         • Quantifying dental evolution

Height maps & OPC of two dietary
categories in Rodentia & Carnivora
        (Evans et al. 2007)

Geographic Information System
technology as a morphometric tool for
                                          Orientation Patch Count
quantifying morphological variation in
an ammonoid clade (Knauss &
Yacobucci 2014)
                                         • Reconstruction of diets in palaeoecology

                                         • Quantifying dental evolution

                                         • Other objects…?

Orientation Patch Count

                           • Reconstruction of diets in palaeoecology

                           • Quantifying dental evolution

                           • Other objects…?

                           • Anything, really!
Pokemon #006 - Charizard

Orientation Patch Count

Challenges:

• Trouble differentiating specific dietary
 categories: insectivory, frugivory & folivory

• GIS can be cumbersome & is its own
 “ecosystem” apart from other modern 3D
 work
        → Barrier of entry

Morphoviewer                              .ply
                                           .stl

• Open-Source Javascript application

• By Johann Muszynski; GitHub

• Based on surface normal orientation

• Input filetypes .ply or .stl

• Runs in Firefox / Chrome

• Option for patch size threshold        OPC
                                        values,
                                         maps

I.   Acquire 3D scans

II. Process scans using
    developed protocol

III. Measure with Morphoviewer

IV. Crunch the numbers

PREDICTED DIET
Carnivore                      Omnivore                           Herbivore

 Cheetah    Sloth         Brown Am. Black Polar                    Panda
   111       477           1104   1302    1314                      2199

             OPC; no mesh simplification & no patch size filter
                                                                       Not to scale!

PREDICTED DIET
ore                     Herbivore

Black Polar               Panda                                    Cave
02    1314                 2199                                    3922

              OPC; no mesh simplification & no patch size filter
                                                                     Not to scale!

The Polar Bear Enigma

Why the high complexity?

   • Ghost of Evolution

      • Slowly simplifying?

      • Evolutionary dead end?

      • Relaxed selection?

               (Lahti et al. 2009)

So what else can you do with OPC?

Questions?

Thanks to:
Academy Prof. Jukka Jernvall

Docent Jacqueline Moustakas Verho

Dr. Eline Lorenzen, &

the Copenhagen Museum of Natural History

Dr. Björn Kröger & LUOMUS

Everyone at Jernvall EvoDevo lab

Johan Muszynski

                                           + The brave folks who originally collected the
                                                             specimens

Cited sources
Boyer, D. M. (2008). Relief index of second       Knauss, M.J. and Yacobucci, M.M., 2014.
mandibular molars is a correlate of diet          Geographic Information Systems technology
among prosimian primates and other                as a morphometric tool for quantifying
euarchontan mammals. Journal of Human             morphological variation in an ammonoid
Evolution, 55(6), 1118–1137.                      clade. Palaeontologia Electronica, 17(1),
                                                  pp.1-27.
Bunn, J.M., Boyer, D.M., Lipman, Y., St. Clair,
E.M., Jernvall, J. and Daubechies, I., 2011.      Polly, P. D. (2007). Development with a bite.
Comparing Dirichlet normal surface energy of      Nature, 449(7161), 413–414.
tooth crowns, a new technique of molar            https://doi.org/10.1038/449413a
shape quantification for dietary inference,
with previous methods in isolation and in         Saarnisalo, O. (2019). Temporal effects of
combination. American Journal of Physical         ectodysplasin signalling on tooth patterning
Anthropology, 145(2), pp.247-261.                 (University of Helsinki). Retrieved from
                                                  https://helda.helsinki.fi/handle/10138/305338
Cuozzo, F.P., Ungar, P.S. and Sauther, M.L.,
2012. Primate dental ecology: How teeth           Wilson, G. P., Evans, A. R., Corfe, I. J., Smits, P.
respond to the environment. American              D., Fortelius, M., & Jernvall, J. (2012). Adaptive
journal of physical anthropology, 148(2),         radiation of multituberculate mammals
pp.159-162.                                       before the extinction of dinosaurs. Nature,
                                                  483(7390), 457–460.
Evans, A. R., & Janis, C. M. (2014). The
Evolution of High Dental Complexity in the        Winer, J. N., Arzi, B., Leale, D. M., Kass, P. H., &
Horse Lineage. Annales Zoologici Fennici,         Verstraete, F. J. M. (2016). Dental and
51(1–2), 73–79.                                   Temporomandibular Joint Pathology of the
                                                  Polar Bear (Ursus maritimus). Journal of
Kay, R.F., 1975. The functional adaptations of    Comparative Pathology, 155(2–3), 231–241.
primate molar teeth. American Journal of          https://doi.org/10.1016/J.JCPA.2016.07.004
Physical Anthropology, 43(2), pp.195-215.

Kavanagh, K.D., Evans, A.R. and Jernvall, J.,
2007. Predicting evolutionary patterns of
mammalian teeth from development. Nature,
449(7161), p.427.

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