Two new ootaxa from the late Jurassic: The oldest record of crocodylomorph eggs, from the Lourinhã Formation, Portugal

Abstract

The Late Jurassic Lourinhã Formation is known for its abundant remains of dinosaurs, crocodylomorphs and other vertebrates. Among this record are nine localities that have produced either dinosaur embryos, eggs or eggshell fragments. Herein, we describe and identify the first crocodiloid morphotype eggs and eggshells from the Lourinhã Formation, from five occurrences. One clutch from Cambelas, composed of 13 eggs, eggshell fragments from Casal da Rola and Peralta, one crushed egg and eggshells from Paimogo North, and four crushed eggs as well as eggshell fragments from Paimogo South. We observed and confirmed diagnostic morphological characters for crocodiloid eggshells and which are consistent with a crocodylomorph affinity, such as the ellipsoidal shape, wedge-shaped shell units, triangular extinction under cross-polarized light, and tabular ultrastructure. This material is distinctive enough to propose two new ootaxa within the oofamily Krokolithidae, Suchoolithus portucalensis, oogen. and oosp. nov., for the material from Cambelas, the most complete clutch known for crocodiloid eggs, and Krokolithes dinophilus, oosp. nov., for the remaining material. These are the oldest crocodylomorph eggs known, extending the fossil record for this group to the Late Jurassic. Furthermore, except for the clutch from Cambelas, the material was found with theropod eggs and nests, in the other four occurrences, which seem to suggest some form of biological relationship, still unclear at this point.

Raman Spectroscopy Detects Amorphous Carbon in an Enigmatic Egg From the Upper Cretaceous Wido Volcanics of South Korea

“…Electron backscatter diffraction imaging shows that the calcite grains with horizontal c-axis are present in the inner part of eggshell whereas c-axis align vertically toward the outer surface ( Figure 7A). As seen from the extinction pattern (see PLM observation above), the shell units are usually wedge-like ( Figures 7A-C), a feature also known in modern and fossil crocodyliform eggshells (see Hirsch and Quinn, 1990;Tanaka et al, 2011;Moreno-Azanza et al, 2014aMarzola et al, 2015, Table 3;Srivastava et al, 2015;Jackson and Varricchio, 2016;Russo et al, 2017). One may think that the calcite grains with horizontal c-axis are diagenetic calcites, but the extant crocodyliform eggshells also show calcite with horizontal c-axis to the middle part of the eggshell (see "Comparative Study" below).…”

“…In the fieldwork in 2016, a solitary partial egg had been found in the Wido Volcanics of South Korea where two types of dinosaur egg fossils were reported Kim et al, 2019). The most peculiar microstructural feature of this egg is several parallel dark bands, which is reminiscent of the dark band structure in modern and fossil crocodyliform eggshells (e.g., Marzola et al, 2015;Russo et al, 2017). We hypothesized that the dark bands, which were observed in all eggshells, of this eggshell are attributed to the composition, mainly due to the preserved carbonaceous (probably organic) matter.…”

Upper Jurassic sauropod record in the Lusitanian Basin (Portugal): Geographical and lithostratigraphical distribution

“…Other vertebrate groups have been reported, such as fishes (Sauvage, 1897-98;Kriwet, 2000;Balbino, 2003), amphibians (Wiechmann, 2000), turtles (Sauvage, 1897-98;Bräm, 1973;Antunes et al, 1988;Gassner, 2000;Pérez-García and Ortega, 2011;Pérez-García, 2015); sphenodonts Malafaia et al, 2010a), squamates (Seiffert, 1973;Broschinski, 2000;Caldwell et al, 2015), pterosaurs (Dantas, 1987;Wiechmann and Gloy, 2000), crocodyliforms (Sauvage, 1897-98;Krebs and Schwarz, 2000;Schwarz and Fechner, 2004;Schwarz and Salisbury, 2005;Tennant and Mannion, 2014;Russo et al, 2017), mammals (e.g., Hahn, 1971;Krusat, 1980;Hahn and Hahn, 2000;Krebs, 2000;Martin, 2000;Martin and Nowotny, 2000;Martin, 2005), and possible plesiosaurs (Castanhinha and Mateus, 2007).…”

“…Among them, the turtle record is very significant, including the type material of "Plesiochelys" choffati and Hylaeochelys kappa (Sauvage, 1897-98;Pérez-García et al, 2008;Pérez-García and Ortega, 2013;Pérez-García, 2015). The record of crocodyliforms is also abundant, represented not only by osteological elements, but also by a nest with eggs, found in the Cambelas area (Russo et al 2014a(Russo et al , 2014b(Russo et al , 2017.…”

First record of an amniotic egg from the Romualdo Formation (Lower Cretaceous, Araripe Basin, Brazil)

“…In the radial section of the shell, the basic units individually exhibit the typical crocodylomorph pattern, consisting of polycrystalline units of calcite in the form of compact wedges, with small interstices in its bulbous base ( Figures 4C-D) (e.g. Mikhailov, 1997;Oliveira et al, 2011;Marsola, 2013;Moreno-Azanza et al, 2015;Russo et al, 2017). Since the crystals are not visualized through the entire radial section, a certain limitation was verified when observing these structures.…”