Macroolithus sp.
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publication ID |
https://doi.org/ 10.4202/app.00497.2018 |
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persistent identifier |
https://treatment.plazi.org/id/03ADF467-FFDC-FF93-DC08-F8D2FC25F5F0 |
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treatment provided by |
Felipe |
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scientific name |
Macroolithus sp. |
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Figs. 1, 3 View Fig .
Material.— Five egg clutches (HGM-41H-V0074, DM-2014-P0154; PFMM-0014002972, PFMM-0014004392, PFMM-0014003019) from the Late Cretaceous , Nanxiong Group of Dayu County, Ganzhou, Jiangxi, China
Description.—All eggs in the five clutches (HGM-41HV0074, DM-2014-P0154; PFMM-0014002972, PFMM-0014004392, PFMM-0014003019) display elongate egg shape and linearituberculate surfacial ornamentaions ( Fig. 2 View Fig ). Eggs are arranged in three or four rings ( Fig. 2 View Fig ). While the length and width of the eggs in the inner rings are not measurable, the eggs in the outermost ring of the five studied clutches present similar gross mophology (length: 152–197 mm and width: 58–86 mm). The eggshell thickness of the studied egg clutches varies from 1.0– 1.5 mm ( Fig. 3 View Fig ). In some eggs, a layer of secondary calcite is observed on the calcitic egshell layer (see Fig. 3B, D–F View Fig ). The secondary calcite layer is distinguishable based on its different extinction pattern from the eggshell layer under the polarzied microscope, thus indicating a lack of diagenetic replacement in the eggshell layer that may lead to overestimation of shell thickness. The ML thickness varies from 0.2–0.3 mm and the CL thickness ranges from 0.8–1.0 mm; therefore, the CL:ML ratio is from 2:1–3.4:1. The ML/CL boundary is apprant and wavy.
Remarks.—The elongate egg shape presented by the studied egg indicates the assignment to Elongatoolithidae ( Zhao 1975) , which is laid by oviraptorosaurians as evidenced by several reports of oviraptorosaurian embryo-containing eggs ( Cheng et al. 2008; Wang et al. 2016; Pu et al. 2017). The oofamily Elongatoolithidae contains Elongatoolithus , Macroolithus , Macroelongatoolithus , Nanhsiungoolithus, Heishannoolithus , Paraelongatoolithus , Undulatoolithus , and Megafusoolithus . Based on the egg length (152–197 mm; Fig. 2 View Fig ), Macroelongatoolithus and Megafusoolithus (usually more than 400 mm; Table3; Zhao et al. 2015) are excluded.The eggshell thickness of the studied egg (1.3–1.5 mm; Fig. 3 View Fig ) is significantly greater than that of Elongatoolithus (usually less than 1.2 mm; Table 3; Wang et al. 2016), Nanhsiungoolithus ( Zhao, 1975) , Paraelongatoolithus (0.5–0.8 mm; Table 3; Wang et al. 2010) and Undulatoolithus (0.75–1.46 mm; Table 3; Wang et al. 2013a). Although Heishanoolithus eggs present similar eggshell thickness (1.2–1.5 mm; Table 3; Zhao and Zhao 1999), the studied eggs display distinctive eggshell surface ornamentation (linearituberculate), thus further constraining the studied egg clutches to Macroolithus . While the wavy ML/CL boundary present in the studied egg clutches is indicative of Macroolithus yaotunensis ( Fig. 3 View Fig ), we do not assign the clutches to a specific ootaxon because of ootaxonomic ambiguity. Moreover, despite the report of an Heyuannia huangi embryo inside a Macroolithus yaotunensis egg ( Cheng et al. 2008), Macroolithus eggs could possibly pertain to any similar sized oviraptorid dinosaur because many elongatoolithid eggs are microstructurally similar to each other. We therefore refer to all studied eggs simply as “oviraptorid eggs.”
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