Abstract
As a result of several years of screen-washing activity, a remarkable assemblage of eggshell fragments has been recovered from the Late Cretaceous vertebrate locality of Iharkut, Hungary. Detailed investigation of the assemblage by multiple visualization techniques (scanning electron microscopy, polarizing light microscopy, X-ray micro-computed tomography), quantitative morphometric analyses, and micro X-ray fluorescence spectrometry revealed a diverse composition of five different eggshell morphotypes (MT I–MT V) and three subcategories within the second morphotype (MT II/a, b, c), with MT I being by far the most abundant (83%) in the assemblage. MT I, MT III, and MT V represent theropod dinosaurian eggshells, whereas MT II and MT IV show characteristics of crocodilian and squamate eggshells, respectively. Hence, despite their fragmentary nature, these eggshells represent the first clear evidence that various sauropsid taxa had nesting sites near the ancient fluvial system of Iharkut. Besides the implied...
Highlights
The exceptional Santonian beds of the Upper Cretaceous Csehbánya Formation at the Iharkút vertebrate locality (Bakony Mountains, northwestern Hungary) have yielded a rich and diverse assemblage of vertebrate and plant remains during the last 15 years of excavations (Ősi et al 2012a; Csiki-Sava et al 2015), in which traditional collecting techniques were augmented by screen-washing of the most productive, bone-bearing layers
Whereas more than 2,000 eggshell fragments were recovered from 48 kg of coarse-grained sediment from Unit 1 of SZ-6, only five fragments were found in 2 kg of residue of the screen-washed layers of SZ-7–8
More than 99% of the classifiable eggshell fragments could be grouped into three different morphotypes with very different relative abundances and a considerable diversity in ornamentation within two of the three groups (Fig. 3)
Summary
The exceptional Santonian beds of the Upper Cretaceous Csehbánya Formation at the Iharkút vertebrate locality (Bakony Mountains, northwestern Hungary) have yielded a rich and diverse assemblage of vertebrate and plant remains during the last 15 years of excavations (Ősi et al 2012a; Csiki-Sava et al 2015), in which traditional collecting techniques were augmented by screen-washing of the most productive, bone-bearing layers. The investigated stratigraphic unit of the Csehbánya Formation, which had been exposed by open-pit bauxite mining activity in the area of Iharkút (Fig. 1A), is made up of a cyclic alternation of sandstone and variegated siltstone and clay layers with sporadic intercalation of thin coal seams. This sedimentological setting implies that the exposed layers were deposited by an anastomosing fluvial system in a topographically low-level, wet, alluvial plain environment (Botfalvai et al 2016). Palynological data imply a Late Santonian age for this sequence (Bodor and Baranyi 2012)
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