Arianny P. Storari

In 2020, a group of Brazilian female paleontologists from various universities and public institutions conducted the study “Brazilian Paleontology Gender Profile,” whose main objective was to assess the current demographic diversity of Brazilian paleontologists and how the role of women has evolved throughout the history of the Brazilian Society of Paleontology. Initially, the project aimed to determine the number of professionals working in Paleontology and their demographic distribution in the country. However, our research expanded, encompassing race, Indigenous representation, LGBTQIAP+ data, parenthood, harassment, and gender violence. The present work presents the first installment of three sets of unpublished data, shedding light on gender issues and how to combat gender discrimination through the proposal of affirmative action policies that could be taken within the Brazilian Society of Paleontology and other scientific associations in South America. Keywords: gender profile, women in science, gender biases.

The Crato Formation (Aptian, Lower Cretaceous) is a fossiliferous deposit of global significance, representing a lacustrine palaeoenvironment which offers insights into aquatic insect taphonomy. Despite its importance, prior studies lacked an actualistic approach. Here, we analyze the preservation of mayflies (Ephemeroptera) and dragonflies (Odonata) from this formation using experimental taphonomy on 253 extant Ephemeroptera and 236 Odonata, alongside 306 fossil specimens. Disarticulation experiments showed that the thorax of modern mayfly larvae disarticulated first, yet Crato Hexagenitidae larvae retained intact thoraces, indicating minimal disturbance and autochthonous deposition. Fossil alate specimens rarely exhibited decay-related wing damage, aligning with short decay times. Dragonfly carcasses exhibited a characteristic leg posture in death, also preserved in Crato fossils, further suggesting minimal transport. Additionally, fossil dragonflies retained labial masks, the first structure to disarticulate experimentally, consistent with parautochthonous assemblages. Mayfly larvae exposed to low salinity during experiments exhibited excessive defecation before death, hinting at possible low salinity conditions in the Crato palaeoenvironment, though preservational challenges obscure confirmation. During experimentation, we also noticed that all carcasses immediately floated under hypersaline conditions, while carcasses immersed in non-hypersaline conditions went through slower decomposition. Thus, we can safely propose with experimental data that microbial biofilms on the surface of the water were acting during carcass sinking in this deposit.

The Crato Formation (Lower Cretaceous, Brazil) is a Konservat-Lagerstätte preserving a great number of exceptionally well-preserved insects. Here, we sought to explore the preservational modes of two abundant aquatic and terrestrial groups of this unit, mayflies and crickets. To better understand how exceptional is their preservation, we also present detailed data on the modes of preservation of mayflies from the renowned Solnhofen limestones (Upper Jurassic, Germany). For the Crato Formation, out of 234 fossil mayflies and crickets, ten specimens were additionally analyzed using scanning electron microscopy coupled to energy dispersive X-ray spectroscopy (SEM-EDS), energy and micro-energy dispersive X-ray fluorescence (EDXRF and µEDXRF), and µRaman spectroscopy. For the Solnhofen limestones, 85 adult mayflies were analyzed, and five of them were subjected to SEM-EDS and µEDXRF analyses. The Crato specimens preserve several external and internal microfeatures. The areas with the highest fidelity of preservation are characterized by smaller and more closely-packed crystals when compared to less-preserved parts. We also recovered microscopic features that suggest the presence of microbial mats during the fossilization process. All the analyzed Crato specimens are preserved by replacement of tissues with iron oxides after pyritization. Sulfur occurs scattered in some regions of the crickets, but is associated with low iron counts, which may indicate the presence of sulfates post-dating pyrite oxidation. Additionally, the orthopterans have calcium phosphate preserving some of their structures. Differing from Crato insects, Solnhofen mayflies are overall poorly preserved as mere imprints, and their micron-scale morphology is obliterated by coarse mineral growth, whereas tissues are obliterated by calcite crystals alone or in combination with globular material. There is an elevated concentration of Si, K, Ca, Ti, Mn, and Fe in comparison to the host rock, which may be related to a yet unknown mineral phase(s). Although the paleoenvironments of the Crato Formation and the Solnhofen limestones are different, there are similarities in the style of preservation of their vertebrates and in some of their paleoenvironmental conditions such as anoxic hypersaline bottom waters and deposition of laminated limestones. However, the same does not apply to the preservation of insects, specifically mayflies, which are poorly preserved in the Solnhofen limestones.

The adult holotype of the fossil mayfly Astraeoptera cretacica Brandão et al. 2021 from the Cretaceous Crato Formation, Brazil, is reviewed and attributed to a new family Astraeopteridae fam. nov. Based on alate specimens, we also describe further new representatives of Astraeopteridae fam. nov., namely Astraeoptera vitrea sp. nov. and Astraeoptera oligovenata sp. nov., as well as the new genus and species Eosophobia acuta gen. et sp. nov. A subsequent character analysis of the new material suggests systematic affinities of Astraeopteridae fam. nov. with those extant families of Siphlonuroidea distributed in the Southern Hemisphere. These newly described fossil Siphlonuroidea from the Cretaceous of Brazil thus add to the biogeography and systematics of mayflies.

The systematics of all known extant and fossil taxa of the mayfly family Baetiscidae is reviewed. Previously described fossil Baetiscidae are critically reviewed and their systematic position is re-evaluated. Added herein is the description of Balticobaetisca bispinatasp. nov., a new fossil mayfly from Eocene Baltic Amber. Also described for the first time is the putative adult of Protobaetisca bechlyi Staniczek, 2007 from the Cretaceous Crato Formation of Brazil. Based on external morphological characters of nymphs and adults, we present the first integrated cladistic analysis of both fossil and extant Baetiscidae, which revealed the monophyly of the respective fossil and extant genera and their phylogenetic splitting sequence as Cretomitarcys + (Protobaetisca + (Balticobaetisca + Baetisca)).

Among mayflies, the Hexagenitidae is the most common family of the Cretaceous, including in the world-renowned Crato Formation (Aptian) of northeastern Brazil. However, most of the Crato mayfly fauna was described based on nymphs, which, due to their ontogenetic development, may present numerous continuous characters. As a consequence, many unclear taxa have been described, and their taxonomic position needs to be re-evaluated. We here present a checklist and revision of some previously described species from the Crato Formation and the description of new specimens. We propose a new species, Protoligoneuria heloisae sp. nov., based on a previously described adult erroneously referred to within Oligoneuriidae. Further adult specimens of Hexagenitidae are here described in detail, presenting new morphological data and variations that were, up to now, unknown for Hexagenitidae of the Crato Formation. Lastly, we briefly discuss the genus Cratohexagenites. Our new findings further add to the taxonomical and morphological diversity of the adult mayfly fauna of the Crato Formation.

Mass mortality events are unusual in the Crato Formation. Although mayflies’ accumulations have been previously reported from that unit, they lacked crucial stratigraphic data. Here we provide the first taphonomic analysis of a mayfly mass mortality event, from a layer 285 cm from the top of the Formation, with 40 larvae, and an overview of the general biological community structure of a three meters deep excavated profile. The only other autochthonous taxon observed in the mayfly mortality layer was the gonorynchiform fish Dastilbe. The larvae and fishes were smaller than usual in the layer 285 cm, suggesting that they lived in a shallow water column. Their excellent preservation and a lack of preferential orientation in the samples suggest an absence of significant transport. All mayflies belong to the Hexagenitidae, whose larvae lived in quiet waters. We also recovered allochthonous taxa in that layer indicative of drier weather conditions. Adjacent layers presented crystals and pseudomorphs of halite, suggesting drought and high salinity. In other layers, Dastilbe juveniles were often found in mass mortality events, associated with a richer biota. Our findings support the hypothesis that the Crato Formation’s palaeolake probably experienced seasonal high evaporation, caused by the hot climate tending to aridity, affecting the few autochthonous fauna that managed to live in this setting.

The Crato Formation (Araripe Basin) preserves one of the most diverse entomofaunas of the Cretaceous. Among the groups of insects, mayflies stand out in abundance, but among them oligoneuriids are especially rare. A newly discovered adult oligoneuriid from this unit is here described as Incogemina nubila gen. et sp. nov. and new subfamily Incogemininae. A phylogenetic analysis recovered the new taxon as the sister group to the species-rich and cosmopolitan Oligoneuriinae. The paratype of Colocrus indivicum, described as an "oligoneuriid" from the same unit, is here reviewed and considered as belonging to the family Hexagenitidae. The biogeographical and taxonomic implications of this discovery and the phylogenetic position of Incogemina nubila are discussed. Incogemina bridge an important morphological gap between the Oligoneuriinae and the extant Chromarcys. Also, it demonstrates that the divergence between Oligoneuriinae and Incogemininae probably occurred in South America.