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Crocodylomorph eggs and eggshells are known as old as the Late Jurassic and are frequent components of most multiootaxic eggshell assemblages. Classified within the oofamily Krokolithidae, thei histo- and ultrastructures are conservative throughout geological time, characterised by inverted-trapezoid-shaped shell units that grow from highly spaced basal knobs and present a diagnostic tabular ultrastructure. Here, we report 327 eggshell fragments from a new fossil site from the Maastrichtian of the Southern Pyrenees, Veracruz 1, and erect a new oogenus and oospecies, Pachykrokolithus excavatum oogen. et oosp. nov. characterised by crocodyloid morphotype and a prominent rugosocavate ornamentation. Eggshells from the slightly older locality of Blasi 2b, previously reported as aff. Krokolithidae, are also assigned to this new ootaxon. Different crocodylomorph taxa coexisted during the Late Cretaceous of the Tremp Basin, hindering the attribution of Pachykrokolithus excavatum oogen. et oosp. nov. to a single clade. Nevertheless, allodaposuchid eusuchians were dominant in this ecosystem, and are the most probable producers of Pachykrokolithus excavatum oogen. et oosp. nov. eggs. [ABSTRACT FROM AUTHOR]

Hundreds of megaloolithid eggshells have been found at the Costa de la Coma site (Tremp Fm, South-Central Pyrenees, Spain), the microstructural features (spherulitic eggshell units, thickness, ornamentation and pore system) of which agree with theMegaloolithusoogenus diagnosis. Comparisons with other megaloolithids from the Tremp Basin, southern France and South America, however, showed that these eggshells share many features with the South American oospeciesMegaloolithus patagonicus. A cladistic analysis of the qualitative eggshell features of the main dinosaur taxa was performed. The results grouped the Costa de la Coma eggshells withMegaloolithus patagonicus, forming a clade separated from other megaloolithids, and revealed a polytomy of megaloolithids (associated with sauropods) and spheroolithids (associated with hadrosaurs). The finding ofMegaloolithuscf.patagonicusin the Tremp Fm agrees with skeletal evidence provided by four indeterminate titanosaur forms from the Formation's late Cretaceous deposits. OtherMegaloolithusoospecies of the Tremp Fm may belong to hadrosaurs, the skeletal remains of which are also abundant in the Tremp Basin. [ABSTRACT FROM AUTHOR]

The Upper Cretaceous outcrops of the Pyrenees yield one of the most extensive and continuous records of paleoological remains anywhere in the world. Most of eggs and eggshells have been referred to the oofamily Megaloolithidae. In this study, we present a revision of eggshell fragments from the Blasi 2 locality, lattermost Maastrichtian in age, previously assigned to aff. Megaloolithidae. The presence of a blocky extinction pattern and basal knobs supports a crocodilian affinity of these materials. We classify them as Krokolithidae indet. Three structural layers can be recognised in the Blasi 2 eggshells, a feature that is shared with other recent eggshells (e.g.Crocodylus porosusandCrocodylus niloticus) and fossil crocodylomorph eggshells (Krokolitheswilsoni), which were previously described as single layered. The new proposed affinity of the Blasi 2 eggshells reduces the Megaloolithidae oodiversity of the last few million years of the Cretaceous in the Pyrenees to only two valid ootaxa,MegaloolithusmamillareandMegaloolithusbaghensis. The lack of more complete material precludes the erection of new ootaxa based on the Blasi 2 material. [ABSTRACT FROM PUBLISHER]

Abstract: The isotopic compositions (δ13C and δ18O) of dinosaur eggshells have been widely used in palaeoenvironmental studies, although the geochemical signatures of eggshells are not usually contrasted with other proxies. In this work, the isotopic signatures of eggshells from a large Maastrichtian succession from the Tremp Formation (Southern Pyrenees, Spain) are compared to those of carbonate pedogenic nodules occurring in the same levels. The isotopic signatures of eggshells vary according to the stratigraphic unit and geographical location. A group of samples from several localities corresponding to eggshells without significant diagenetic imprints has isotopic values differing from the associated nodules; The Late Cretaceous isotopic composition record from the Tremp Fm. is consistent that is, the eggshells have distinct primary signatures preserved. However, the eggshells from another locality, which exhibit neomorphed textures, display isotopic signatures similar to the associated pedogenic carbonate, which suggests a diagenetic isotopic signature and confirms alteration in the eggshells. Both microscopic and geochemical data suggest that an early meteoric diagenesis (pedogenesis) is responsible for the secondary signatures. The δ13C values in the carbonate pedogenic nodules indicate a carbon isotopic composition typical of C3 plants, although the slight difference in δ13C between the palaeosol carbonate of coeval successions may be due to slightly different palaeoenvironmental conditions. The small discrepancy in the δ13C calculated for C3 plants, from carbonate nodules and from eggshells may be because the palaeosol carbonate gives the isotopic composition of the vegetation grown at a local site whereas the δ13C from eggshells is a proxy for the ingested food in the area in which the dinosaurs lived. The oxygen isotopic compositions from palaeosol carbonate nodules have been used for calculation of the air temperature, and we may conclude that the mean air temperature in the studied area during the Late Cretaceous was approximately 21°C. The use of this temperature gives rational results in the calculation of the oxygen isotopic composition of palaeosol carbonate by means of the isotopic composition of the eggshell carbonate. Additionally, a relatively continuous isotopic record of nodules shows an overall vertical trend towards negative δ13C values and a high relative and steady δ18O content throughout the Maastrichtian. The K/Pg boundary was recorded by a negative excursion in δ13C in the carbonate nodules. [Copyright &y& Elsevier]

Abstract: The Coll de Nargó area (Lleida Province, south-central Pyrenees) has yielded thousands of dinosaur eggs distributed in more than 30 levels across 370 m of Upper Cretaceous Tremp Formation deposits. Two stratigraphic units yielding dinosaur eggshells, eggs and clutches, can be distinguished. Multiple eggshells were collected from up to 75 different in situ clutches, located in consecutive stratigraphical levels throughout the Mas de Pinyes section. Four different oospecies have been recognized: Megaloolithus aureliensis, Megaloolithus siruguei, Megaloolithus cf. baghensis and Cairanoolithus cf. roussetensis. In absence of typical biochronological markers, fossil eggshells may have potential as a tool for dating. Based on these ootaxa, three oozones can be established along the stratigraphic section. The lower assemblage is composed by M. aureliensis, M. siruguei and Cairanoolithus cf. roussetensis; the middle one consists only of M. siruguei, while the upper oozone is characterized by M. cf. baghensis. Results suggest that the age of Coll de Nargó rocks ranges from the latest Campanian to the beginning of the Late Maastrichtian. Also reported is the first evidence of the oogenus Cairanoolithus outside of France, where it was regarded as an endemic ootaxon. The Coll de Nargó area is considered to be one of the most important dinosaur nesting areas in Europe recurrently used by several dinosaurs during a long time span. Finally, the presence of fossilized eggshell membrane in several specimens from Coll de Nargó contributes to understanding the taphonomic process of megaloolithid eggs in this area. [Copyright &y& Elsevier]

A new type of small, ovoid dinosaur egg, Sankofa pyrenaica oogen. nov. oosp. nov., with a prismatic type eggshell is described from upper Cretaceous (upper Campanian-Maastrichtian) deposits of the Montsec area, South Pyrenean Central Unit, Lleida, Catalonia, Spain. This egg type was sub-vertically laid in only two rich monospecific sites of a single stratigraphic layer from coastal deposits of the Aren Formation, interpreted as an emerged beach ridge of a barrier island - lagoon depositional system. The size and shape of these eggs with their asymmetric poles are roughly similar to modern hen eggs, which is unusual in the Cretaceous fossil egg record. Its phylogenetic position clusters with bird and Troodontid eggs. A morphospace analysis of egg shapes shows the similarity of the new egg to a Campanian fossil bird egg from Argentina, both being intermediate between modern-bird eggs and extinct nonavian theropod eggs. However, the eggshell microstructure of Sankofa pyrenaica differs from that of bird eggs in its incipient squamatic texture. It has a peculiar pattern of interlocking small crystals in the middle of the palisade layer, instead of the thick squamatic structure commonly present in modern avian eggshells. This new egg type is attributed to a small theropod, probably with a single oviduct like birds and whose mosaic distribution of features is a combination between that of birds and nonavian theropods. This enhances the arguments supporting the close phylogenetic relationships between both groups. [ABSTRACT FROM AUTHOR]

Abstract: The Late Cretaceous deposits of the continental Tremp Formation in the Vallcebre Syncline (South-eastern Pyrenees) provide an extensive egg record of dinosaurs. The parataxonomical study and analysis of multiple eggshell samples, the precise stratigraphical control of several sections and the time calibration of the abundant egg levels enable the establishment of a robust oospecies succession. The successive occurrence of three megaloolithid oospecies (Megaloolithus siruguei–Megaloolithus mamillare–Megaloolithus sp.) in the Early and Late Maastrichtian is well correlated with the magnetic polarity time scale throughout the chron 31. The replacement of Megaloolithus siruguei with Megaloolithus mamillare occurs around the reversal of chrons 31r–31n. A comparison with oospecies successions from Arc basin localities (France) allows the age calibration for such oospecies replacement to be confirmed. This age refinement implies that some of the stated boundaries for the proposed oospecies assemblages may change and that an in-depth revision of the age and magnetic calibration of some south European egg localities is required. [Copyright &y& Elsevier]

Abstract: Eggshell fragments of ratite type (Ornitholithus, oofamily Elongatoolithidae)–attributed to giant birds–are described from Upper Paleocene deposits in the Pyrenean–Provence region. We study the porosity of a rich Ornitholithus sample from Claret-4 locality (Tremp Fm, Lleida, Spain), closely related to the global warming event which took place at the Paleocene–Eocene boundary (PETM), in order to infer relations between egg conductance, nesting habits and palaeoenviromental conditions. An egg mass of around 3 kg is inferred for the large Ornitholithus eggs, in agreement with the values previously estimated by Touraine [Touraine, F., 1960. Oeufs d´Oiseaux de très grande taille dans l´Eocène inférieur de Provence, pp. 783–789], but lower than those obtained by Dughi and Sirugue [Dughi, R., Sirugue, F., 1962. Distribution verticale des oeufs d´oiseaux fósiles de l´Eocène de Basse–Provence. Bull. Soc. Geol. Fr. 7, 69–78]; O. arquatus group, 8.7 kg). Porosity observed in Ornitholithus eggshells is extremely reduced in comparison to bird eggs and even much more reduced in relation to theropod dinosaurs. Pore number is similar to that of bird eggs but most Ornitholithus pores are exceedingly small (micropores), thus pore radius and total pore area is much lower than in recent birds. Moreover, Ornitholithus micropores lack connectivity between them, thus decreasing functional pore area and permeability. The function of micropores could be related to weight spare, favorable hatching and/or thermal isolation. Ornitholithus eggshells are the most compact of all bird or theropod eggshells studied so far. Consequently, calculated water vapor conductance values in Ornitholithus eggs are in average 8 times lower than that for recent birds. The relation between egg conductance and nesting environment shown in recent birds suggests, in the case of Ornitholithus, an open and extremely dry nest environment. Anomalous compact Ornitholithus eggshells could help to keep eggs'' inner relatively-constant temperature and humidity, in the extremely warm and dry palaeoenvironment inferred for the Pyrenean region at the Paleocene Eocene Thermal Maximum. [Copyright &y& Elsevier]