Fig 1.
Schematic and simplified paleogeography of the central-eastern Southern Alps during the Late Cretaceous superimposed on present-day geography and indication of the site of finding of IGVR 9105.
1. Shallow-water carbonate platform deposits (Friuli Platform). 2 Slope-resedimented deposits of the Friuli Platform (“Fadalto Limestone”). 3. Basinal pelagic limestones (Scaglia Rossa and equivalent deposits). Modified after [44,57]. Map modified and reprinted from [57] under a CC BY license, with permission from Rivista Italiana di Paleontologia e Stratigrafia, original copyright year 2013.
Fig 2.
Scaglia Rossa “lastame” slab preserving the protostegid IGVR 9105.
Scale bar 30 cm.
Fig 3.
Anatomical interpretation of IGVR 91051.
A) Anatomical drawing with color-based differentiation of skeletal regions. B) Detail of left humerus. C) Detail of right humerus. Abbreviations: ac, acromion; co, coracoid; dt, dentary; epi, epiplastron; f, femur; fi, fibula; h, humerus; hyo, hyoplastron; hyp, hypoplastron; il, ilium; int, intermedium; isc, ischium; p.p, peripheral plate; pu, pubis; r, rib head; ral, radiale; sc, scapula; spy, suprapygal; ta, tarsal; ti, tibia; ul, ulna; ulr, ulnare; xip, xiphiplastron. Scale bars: 10 cm.
Fig 4.
Gastrolith locations and compositions.
A) Designation and distribution of the ten preserved gastroliths on IGVR 91051 and of the other materials foreign to the skeleton. B) SEM-EDS spectra of G3 highlighting its siliceous composition. C) SEM-EDS spectra of G2 highlighting its carbonatic composition. Abbreviations: brc., brachiopod; crn, crinoid element.
Fig 5.
Preservational and taphonomic details of IGVR 91051.
A) Anterior left region of the skeleton under UVA-B-C light showcasing the lack of fluorescence-response of the glue near the gastroliths. B) Detail of costal and peripheral carapace elements under ultraviolet light. C) Photogrammetry 3D depth map of the anterior portion of the specimen. Gastroliths indicated with magenta arrows. Scale bars: A) 5 cm; B) 10 cm; C) 30 cm.
Fig 6.
Close-ups of the preserved gastroliths within IGVR 9105.
A) G1. B) G2. C) G3. D) G4. E) G5. F) From the left G6 and G7. G) G8. H) G9. I) G10. Scale bars: A,C,E,F,H 2) cm; B,G,I) 1 cm.
Table 1.
Summary of gastroliths characterization in IGVR 91051.
Fig 7.
A) Stones preserved within the trunk of chelonioid IGVR 19501 were significantly more circular than abiotically dispersed allochthonous clasts from the same formation (SAA), as were bona fide gastroliths from other species. B-D) Bona fide gastroliths were also significantly smaller than abiotically dispersed SAA clasts, which had significantly higher variance in size than both the stones preserved within IGVR 19501 and the bona fide gastroliths. Single asterisks (*) indicate significant among-group test results (ANOVA and Levene’s test p < 0.05), whereas double asterisks (**) indicate that the designated group differs significantly from the set of SAA clasts (pairwise post hoc Tukey tests, p < 0.05).
Fig 8.
Surface etching patterns on carbonatic pebbles.
A) Surface pits and cracks on G3. B) Surface pitting of G4. C) Experimentally etched pebble before (i) and after a month (ii) of treatment. Scale bars 5 mm.
Fig 9.
Extant chelonioid gastroliths.
A) 28 carbonatic elements extracted from the gut contents of Chelonia mydas sample #23 retrieved from the Republic of the Seychelles. B) 6 carbonatic elements extracted from the gut contents of Chelonia mydas sample #10 retrieved from the Republic of the Seychelles. C) Radiograph of a 20-year-old female Eretmochelys imbricata from the Red Sea with gravel in the colon (image courtesy of Efrat Weizman Kohavi, Israeli Sea Turtle Rescue Center). Scale bars: A,B) 2 cm.
Table 2.
Gastrolith distribution in the surveyed Seychelles dataset.
Gastroliths (coralline rock fragments) were found in the majority of guts from gravid female green sea turtles (Chelonia mydas) but not in non-breeding female or male individuals in a study of green turtles legally harvested in the Republic of Seychelles in 1982–1983.