Research ArticlePALEONTOLOGY

Biomechanical simulations reveal a trade-off between adaptation to glacial climate and dietary niche versatility in European cave bears

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Science Advances  01 Apr 2020:
Vol. 6, no. 14, eaay9462
DOI: 10.1126/sciadv.aay9462
  • Fig. 1 Paranasal sinus anatomy and assembled phylogeny for all living bear species and cave bears.

    The phylogeny (i.e., tree topology, branch lengths, and divergence times) is taken from (24). The 3D model of the paranasal sinus (within the box) belongs to U. arctos. 1, maxillary sinus; 2, nasomaxillary sinus; 3, rostro-frontal sinus; 4, mediolateral frontal sinus; 5, caudo-sagittal frontal sinus; 6, ethmoid-lateral sinus; 7, palatine-sphenoid sinus. Sinus anatomy is based on (40). Ma, million years.

  • Fig. 2 Biomechanical settings for FEAs using the 3D model of U. ingressus as an example.

    (A) Model of U. ingressus skull showing the disposition of the sinuses in the frontal dome (left) and its topographical relationship with the brain. (B) Centers of gravity (black circles) of mandible muscle insertion areas. Centers of gravity are represented by black circles. (C) Simulation of loading muscle forces used in biomechanical simulations and obtained with the BONELOAD script in MATLAB. (D) Muscle attachments of the skull used in the biomechanical simulations and the nodal restraint (red points) used for each biting scenario. C, canine; P, premolar; M, molar; i.t.m., internal pterygoid muscle (green); m.m., masseter muscle group (dark pink); t.m., temporalis muscle group (dark blue); t.m.j., temporo-mandibular joint; m.s., mandibular symphysis.

  • Fig. 3 Results of FEAs.

    (A) Bivariate plot of the maximum differences in ME (m∆ME) and SE (m∆SEa) across the tooth loci simulations for each species obtained from models with sinuses. (B) Bivariate plot of the maximum differences in ME (m∆ME) and SE (m∆SEa) across the tooth loci simulations for each species obtained from models without sinuses. Ame, A. melanoleuca; Hml, H. malayanus; Mur, M. ursinus; Tor, T. ornatus; Uam, U. americanus; Uarc, U. arctos; Uere, U. eremus; Uing, U. ingressus; Ulad, U. spelaeus ladinicus; Uspe, U. spelaeus spelaeus; Uthi, U. thibetanus.

  • Fig. 4 Contour plots of von Mises stress distribution obtained from FEAs on each cranial model with sinuses.

    All models are obtained from each biting scenario for the right working side. (A) Cranial models of living bears. (B) Cranial models of cave bears. Only two chewing scenarios (canine and second upper molar) are shown for clarity.

  • Fig. 5 Contour plots of von Mises stress distribution obtained from FEAs on each cranial model without sinuses.

    All models are obtained from FEAs of each chewing scenario for the right working side. (A) Cranial models of living bears. (B) Cranial models of cave bears. Only two chewing scenarios (canine and second upper molar) are shown for clarity.

  • Fig. 6 Biomechanical effects of the paranasal sinuses.

    (A) Traitgram of the im∆SEa (see text for details). Green branches represent those species in which the sinuses are advantageous, and those in blue represent those that the sinuses are disadvantageous. (B) Phylomorphospace of the bivariate plot depicted from the im∆SEa against the relativized sinus volume to skull volume. In all cases, black circles represent extinct taxa, and gray circles represent living taxa. The virtual models of the sinuses analyzed are indicated in dark pink.

Supplementary Materials

  • Supplementary Materials

    Biomechanical simulations reveal a trade-off between adaptation to glacial climate and dietary niche versatility in European cave bears

    Alejandro Pérez-Ramos, Z. Jack Tseng, Aurora Grandal-D’Anglade, Gernot Rabeder, Francisco J. Pastor, Borja Figueirido

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    • Supplementary Methods
    • Supplementary Results
    • Fig. S1
    • Tables S1 to S9

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