Fig 1.
Fossil sectioning and experimental set up.
(A) Depiction of the fossil sectioning process. The solid lines indicate cuts made to remove the end caps and dashed lines indicate cuts made to section the fossil into thirds. (B) Schematic of the dissolution experiment closed reaction vessel.
Table 1.
Pre- and post-dissolution masses, total mass loss, percentage mass loss, and dissolution rate per day for all fossils at each pH tested.
Table 2.
Paired T-test results of mass loss.
Table 3.
Changes in water chemistry from pre- to post-dissolution samples.
Table 4.
Changes in fossil chemistry from pre- to post-dissolution samples.
Table 5.
Paired T-test results of changes in phosphorus (P) and calcium (Ca) concentrations for aqueous solutions and fossils.
Fig 2.
XRD diffractogram patterns for all F1 samples.
(A) Stacked diffractograms for all F1 samples. The area highlighted in gray (23–39 degrees) is shown in greater detail in B. (B) Detailed view of the F1 diffractogram pattern from 23–39 degrees.
Fig 3.
Bar graph of fossil mineralogical composition.
Mineralogical composition of pre- and post-dissolution fossils based on XRD analyses. (A) F1 samples; (B) F2 samples; (C) F3 samples.
Table 6.
Crystallite size and structural order of detected apatite phases calculated using the Sherrer equation.
Fig 4.
F1 pre-dissolution, pH 6, pH 5, and pH 4 thin sections of cortical and trabecular bone.
Degree of dissolution exhibited in trabecular (A-H) and cortical (I-P) bone thin sections of Fossil 1 (F1) viewed under plane polarized light (PPL) and cross polarized light (XPL). (A) Pre-dissolution PPL image of trabecular bone with relatively intact trabeculae (red arrow) and osteocytes (blue arrow). (B) At pH 6, trabecular bone exhibited with the lowest degree of damage to histologic structures, with increased damange under exposure to (C) pH 5. Degradation of secondary mineral infilling (purple arrow) in a marrow space is present as large cracks and breaks in the mineral, observed in the left of the image. (D) F1 dissolved at pH 4 PPL image of trabecular bone. The trabeculae show a high degree of degradation, evident by small (10’s of μm-sized) bone fragments toward the center of the image (area surrounded by a dashed line). XPL images of trabecular bone (E) pre-dissolution, (F) after exposure to pH 6 solution, and (G) dissolved at pH 5, and (H) dissolved at pH 4. (I)Pre-dissolution PPL image of cortical bone with relatively intact histologic structures. (J) F1 dissolved at pH 6 PPL image of cortical bone with the lowest degree of damage to histologic structures. Dissolution can be observed at the margin of the fossil to the right of the image. (K) After exposure to pH 5 solutions, cortical bone exhibited increased degradation. (L) F1 dissolved at pH 4 PPL image of cortical bone with highest degree of degradation to histologic structures. XPL images of cortical bone (M) pre-dissolution, (N) after exposure to pH 6 solution, (O) dissolved at pH 5, and (P) dissolved at pH 4. Abbreviations: R, resin; cal, calcite.
Table 7.
Interpretation of elemental relationships between fossil and solution samples, based on data presented in Tables 3 and 4, a,b,c.
Fig 5.
Interpreted effects of dissolution on fossil bone surface area.
Cross-sectional schematic diagram demonstrating surface area increases as secondary mineral infilling is dissolved. Phase 1 depicts a fossil with the pore spaces infilled completely by secondary mineral growth. This phase represents the pre-dissolution samples. Phase 2 represents partial dissolution of secondary minerals. Dissolution has not penetrated through the fossil, but dissolution of mineral infilling has created voids that increase pore space, effectively increasing surface area of exposed bone. Phase 3 represents complete dissolution of secondary minerals, and the maximum surface area of the fossil has been attained. Phase 4 is when surface area starts to decrease as pore spaces coalesce.