Fig 1.
Map of sampled locations.
Fig 2.
Phylogenetic framework for this study.
Log10-transformed AILD was mapped on the time tree using a gradient from blue (low values) to red (high values).
Fig 3.
Overview of histology of bears exemplified with Ursus spelaeus s.l. MB. Ma. 10881 (A) and Ursus arctos MNHN 1904–244 (B). The thin-sections of the medial part of the femoral midshaft are shown in cross-polarised light with lambda compensator. White arrows indicate LAGs, H = Haversian tissue, FLC = fibrolamellar complex, PF = parallel-fibered bone (mainly), SO = secondary osteon, WO = woven-fibered bone (mainly). (Scale bars: 2 mm).
Fig 4.
Ontogenetic change of bone histology in the medial part of the femur midshaft of Ursus spelaeus s.l. and Ursus arctos (pictures under cross-polarized light with lambda compensator).
White arrows indicate LAGs. Juvenile Ursus spelaeus s.l. PZO 5136 (Scale bar: 0.5 mm), subadult Ursus spelaeus s.l. MB.Ma.10881 (MfN) (Scale bar: 2 mm), adult Ursus spelaeus s.l. PEC 1183 (AUTH) (Scale bar: 2 mm), senile Ursus spelaeus s.l. LAC 6277b (AUTH) (Scale bar: 2 mm), juvenile Ursus arctos SMNH 2016–5132 (Scale bar: 1 mm), subadult Ursus arctos SMNH 2016–5131 (Scale bar: 2 mm), adult Ursus arctos SMNH 2016–5025 (Scale bar: 2 mm), senile Ursus arctos MNHN 1904–244 (Scale bar: 2 mm). Note that lamellar bone in the outer cortex of adult and senile specimens is indicated as OCL. H = Haversian tissue, FLC = fibrolamellar complex, L = lamellar bone, SO = secondary osteon, WO = woven-fibered bone (mainly).
Fig 5.
Histology of the medial part of the femoral midshaft of Melursus ursinus (MNHN 1879–307).
The thin-section is shown in cross-polarised light with lambda compensator. White arrows indicate LAGs, OCL = outer circumferential layer (mostly formed by lamellar bone), PF = parallel-fibered bone, WO = woven-fibered bone. Note the woven-fibered bone within the OCL. (Scale bars: 2 mm).
Fig 6.
Histology of the posterior part of the femoral midshaft of Ursus spelaeus (MB. Ma. 10886).
The thin-section is shown in cross-polarised light with lambda compensator. Note the dense Haversian tissue, comprised of several generations of secondary osteons, which extends to the outer cortex (Scale bar: 2 mm).
Fig 7.
Comparison of the growth zones between Ursus spelaeus, Ursus americanus, and Ursus arctos (pictures under cross-polarized light with lambda compensator).
White arrows indicate LAGs. Note that inner part of the growth zone exhibits more WO bone whereas the external part exhibits more PF bone. WO = woven-fibered bone, PF = parallel-fibered bone. (Scale bars: 0.5 mm).
Fig 8.
Averaged inter-LAG distance (AILD) correlation to body size and altitude.
Scatter plot of: a) AILD of different bear species compared to their femoral latero-medial diameterat midshaft (LMD) as a proxy for body size (open circle not included in phylogenetic analyses), b) AILD of different cave bear localities compared to their LMD, c) AILD of different cave bear localities compared to the altitude of the locality, d) AILD/LMD-residuals compared to the altitude of the locality (results of OLS regression in the left box, results of Kendall’s tau in the right box).
Table 1.
Correlation of averaged inter-LAG distance (AILD) to body size and altitude in ursids, as given by PGLS (λ = 0) and OLS regressions and Kendall’s tau analyses.
Table 2.
Relationship of averaged inter-LAG distance (AILD) to body size (LMD) in Ursus spelaeus s.s. (incl. U. s. eremus and U. s. ladinicus) and U. ingressus using OLS regressions and Kendall’s tau.
Femoral latero-medial diameter at midshaft (LMD) was used as a proxy for body size.
Table 3.
Influence of cave bear haplotypes on their growth.
Comparison based on OLS regressions for the two different cave bear haplotypes U.spelaeus (incl. U. s. eremus and U. s. ladinicus) and U. ingressus with femoral latero-medial diameter at midshaft (LMD) as a covariate, including or excluding its interaction with the category of haplotype (upper panel and lower panel, respectively).