Fig. 4. Petrographic thin sections of avian and non-avian theropod eggshells from the Upper Cretaceous. A. Styloolithus sabathi oogen. et oosp. nov. (ZPAL MgOv-II-6); horizontal lines at the left side of A1 mark, from bottom to top, the boundaries between the mammillary, second (possible squamatic zone), and third (possible external zone) layers. A2, same as A1, but in polarized light. A3, thin section 9-6 highlighting the same three structural layers as in A1, including the mammillary layer (ML), second layer (2L), and third layer (3L). DL represents the outer diagenetic layer. A4, thin section 9-5, showing properly proportioned ML and 2L, but a loss of the 3L. B. Protoceratopsidovum sincerum Mikhailov, 1994 (PIN 3143/121), horizontal line at left marks the boundary between the mammillary layer and palisade layer. C. Gobioolithus minor Mikhailov, 1996a (ZPAL MgOv-III/11b), horizontal lines at left mark, from bottom to top, the boundaries between the mammillary layer, squamatic zone, and an outer ... : Published as part of Varricchio, David J. & Barta, Daniel E., 2015, Revisiting Sabath's "Larger Avian Eggs" from the Gobi Cretaceous, pp. 11-25 in Acta Palaeontologica Polonica 60 (1) on page 15, DOI: 10.4202/app.00085.2014, http://zenodo.org/record/13282396 ...