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Research Article
The first mayfly (Ephemeroptera, Baetidae) from Late Cretaceous amber of North Carolina, USA
expand article infoPavel Sroka‡, Jean-Luc Gattolliat§|
‡ Biology Centre of the Czech Academy of Sciences, Institute of Entomology, České Budějovice, Czech Republic
§ Naturéum-State Museum of Natural Sciences, Lausanne, Switzerland
| University of Lausanne (UNIL), Lausanne, Switzerland

Corresponding author: Pavel Sroka ( pavel.sroka@centrum.cz )

Academic editor: Florian Witzmann
© 2025 Pavel Sroka, Jean-Luc Gattolliat.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Sroka P, Gattolliat J-L (2025) The first mayfly (Ephemeroptera, Baetidae) from Late Cretaceous amber of North Carolina, USA. Fossil Record 28(1): 125-132. https://doi.org/10.3897/fr.28.e143974
ZooBank: urn:lsid:zoobank.org:pub:21CCCB31-D8CD-4DB4-9AE3-1098513570F0
Open Access

Abstract

Nowadays, Baetidae are among the most diverse and widespread mayfly families worldwide. However, fossil records of this family are very scarce, and each newly discovered specimen is of great importance for assessing the evolutionary history of this group. We report a newly discovered Baetidae fossil from the Cretaceous amber of North Carolina (USA), described herein as Petracloeon carolinensis gen. et sp. nov. The analysis of its morphology and a discussion of its possible affinities with already described Baetidae taxa (both fossil and extant) are provided. This represents the first mayfly from the North Carolina amber and the oldest Baetidae from the Americas. This finding also significantly expands the distribution range of Baetidae in the Cretaceous and supports the origin of the family prior to the main continental breakup beginning in the Jurassic.

Key Words

Amber inclusion, fossil, Mesozoic, new genus, new species, small minnow mayflies

Introduction

Despite the fact that the family Baetidae represents a quarter of the world’s mayfly diversity (Gattolliat and Nieto 2009; Sartori and Brittain 2015) and is present on almost all landmasses except Antarctica, New Zealand, and some oceanic islands, its fossil record is extremely limited. The oldest fossil attributable to the family was referred to as “Baetidae sp. 1” from the Early Cretaceous Lebanese amber (129.4–125 Ma) by McCafferty (1997); the preservation of the fossil is insufficient to allow for a detailed description. Additional Baetidae fossils were discovered from the Mesozoic: Poinar (2011) described Vetuformosa buckleyi Poinar, 2011 from the mid-Cretaceous Burmese amber (99.6–93.5 Ma), and Kluge (1997) published a description of Palaeocloeon taimyricum Kluge, 1997 from the Late Cretaceous Taimyr amber (85.8–83.5 Ma). Another species from Burmese amber, Myanmarella rossi Sinitshenkova, 2000, was first assigned to the family Prosopistomatidae, and later transferred to Baetidae by Staniczek et al. (2022). The same authors also mentioned another unnamed Baetidae specimen from Burmese amber in the collection of the Natural History Museum Stuttgart (SMNS).

Two species from the Eocene Baltic amber, namely Baetis gigantea Hagen, 1856 and Baetis grossa Hagen, 1856 represent very dubious taxa, with their attribution to Baetidae not well-supported (Kluge 2004); moreover, the type material is probably lost. The lack of unambiguous Baetidae in Baltic amber is puzzling, since this deposit has been extensively studied since the 19th century. More reliable records of the family came from the Miocene, with Cloeon tzeltal Varela-Hernández, Riquelme & Montiel-Chávez, 2022 described by Varela-Hernández et al. (2022) from Mexican amber (23.03–15–97 Ma). Moreover, there is extensive undescribed material of the genera Americabaetis Kluge, 1992 and Cloeodes Traver, 1938 from the similarly aged Dominican amber (Poinar 2011, fig 9, and other unpublished data). Another fossil species described as Baetidae, Cloeon emmavillensis Riek, 1954, represents a Pliocene compression fossil from Australia. However, it was described based on poorly preserved larvae, and their attribution to Baetidae is uncertain, relying solely on the similar body shape.

Considering the scarcity of the Baetidae fossil record, each specimen is extremely valuable for inferring the evolutionary history of this highly diverse end ecologically significant group of mayflies. Here, we report the first mayfly fossil attributable to Baetidae from the North Carolina amber (USA), dated to the Late Cretaceous, approximately 83 Ma (Mitra and Mickle 2007). Compared to other Cretaceous amber deposits (e.g., the extensively studied Burmese amber from Northern Myanmar; Ross 2024), fossil inclusions in the amber from North Carolina have received very little attention. Krynicki (2013) reported fossil ants, which were subsequently described by Sosiak et al. (2024). Additionally, Szadziewski et al. (2018) described a phantom crane fly from the family Ptychopteridae (Diptera).

This study represents the first finding of fossil Baetidae from the Cretaceous of the Americas and the earliest record of Baetidae on this continent. We provide a morphological description and an analysis of the possible affinities of the newly discovered specimen to individual lineages within Baetidae.

Material and methods

The female holotype is deposited in the American Museum of Natural History (AMNH) under accession No AMNH NC-VK261. The amber is embedded in a high-end glass conservation epoxy manufactured by Epotek (Epotek 301-2). A syninclusion (AMNH NC-VK262) is represented by a partially preserved specimen of Chironomidae (Diptera). The collecting site (type locality) is located in North Carolina, Wayne Co., near Goldsboro, Neuse River Cut Off, and was collected by V. E. Krynicki. According to Mitra and Mickle (2007), this locality represents an outcrop of the Tar Heel Formation, dated as early Campanian (approximately 83 Ma) based on palynological markers.

The material was examined using Olympus SZX7 and Leica M205 C stereomicroscopes. Photographs were taken using a Canon EOS 1200D digital camera attached to the Leica M205 C stereomicroscope. Original photographs were processed by stacking in Helicon Focus 8.2.2 (Helicon Soft Ltd., Kharkiv, Ukraine) and edited using Adobe Photoshop version CS5 (Adobe Systems Inc., San Jose, USA). The measurements of individual body parts were inferred from photographs taken with a calibration scale.

The wing venation nomenclature follows Kukalová-Peck (1991), and for thoracic structures, we follow Kluge (2004). Morphological abbreviations used throughout the text are as follows: ANi – anteronotal transverse impression; ANp – anteronotal protuberance; C – costa; ce – cercus; CuA – cubitus anterior; CuP – cubitus posterior; ff – forefemur; FSp – furcasternal protuberance; hf – hind femur; hti – hind tibia; IMA – intercalary vein between branches of media anterior; IMP – intercalary vein between branches of media posterior; IRP – intercalary vein between branches of radius posterior; LPs – lateroparapsidal suture; MA – media anterior; mf – middle femur; MLs – median longitudinal suture; MP – media posterior; MPs – medioparapsidal suture; MS – medioscutum; pce – paracercus; PSp – posterior scutal protuberance; RA – radius anterior; RP – radius posterior; ScP – subcosta posterior; SL – scutellum; SLSs – sublateroscutal suture; SSLi – scuto-scutellar impression.

Results

Systematic palaeontology

Class INSECTA Linnaeus, 1758

Subclass PTERYGOTA Lang, 1888

Infraclass HYDROPALAEOPTERA Rohdendorf, 1969

Supraorder EPHEMERIDA Latreille, 1810

Order EPHEMEROPTERA Hyatt & Arms, 1891

Family BAETIDAE Leach, 1815

Petracloeon gen. nov.

https://zoobank.org/8ADDB55B-2E49-43C5-9542-B77731D5CDA3

Type species.

Petracloeon carolinensis gen. et sp. nov.

Diagnosis.

As for the type species.

Etymology.

The new genus is dedicated to Petra Sroková, the wife of PS. Additionally, the holotype represents a specimen preserved in a stone, and “Petra” is derived from a Greek word for “stone”.

Petracloeon carolinensis sp. nov.

https://zoobank.org/558A3CF5-1303-4F53-A066-8191782EACAA
Figs 1–12, 13–20

Diagnosis (female imago).

Small size (body length approximately 1.9 mm); forewing with single marginal intercalary veins poorly expressed (Figs 14, 15); pronounced angle on posterior margin of forewing between CuA and CuP (Figs 15–17); hind wing with small basally positioned costal process (Figs 18, 19); first (most anterior) longitudinal vein of hind wing sigmoidal, second vein bifurcated, with intercalary vein also bifurcated and followed by another simple intercalary vein (Figs 18, 19).

Etymology.

The specific epithet refers to the geographic location of the amber deposit in North Carolina.

Holotype.

AMNH NC-VK261, deposited in AMNH.

Description.

Body length 1.9 mm. Observable from dorsal and ventral aspect (Figs 1, 2). The specimen represents a female (based on compound eyes not distinctly enlarged, forelegs not elongated and no traces of male genitalia).

Figures 1–12. 

Petracloeon carolinensis gen. et sp. nov., body structures. 1. Habitus, dorsal view; 2. Habitus, ventral view; 3. Head, dorsal view; 4. Thorax, dorsal view; 5. Thorax, dorsal view with main sclerites and sutures marked; 6. Base of left foretibia, dorsal view (tibio-patellar suture marked with arrows); 7. Base of left hind tibia, dorsal view (tibio-patellar suture marked with arrows); 8. Distal end of abdomen, dorsal view; 9. Tarsus of left hind leg, base of first tarsomere (fused with tibia) marked with arrow; 10. Tarsus of left hind leg with individual tarsomeres marked by numbers, base of first tarsomere (fused with tibia) marked with arrow; 11. Thorax, ventral view; 12. Thorax, ventral view with marked position of furcasternal protuberances; ANi – anteronotal transverse impression; ANp – anteronotal protuberance; ce – cercus; ff – forefemur; FSp – furcasternal protuberance; hf – hind femur; hti – hind tibia; LPs – lateroparapsidal suture; mf – middle femur; MLs – median longitudinal suture; MPs – medioparapsidal suture; MS – medioscutum; pce – paracercus; PSp – posterior scutal protuberance; SL – scutellum; SLSs – sublateroscutal suture; SSLi – scuto-scutellar impression.

Head : length 0.25 mm, width 0.45 mm. Compound eyes not divided (Fig. 3), diameter 0.21 mm. Distance between compound eyes approximately equal to eye diameter. Three fully developed ocelli of same size. Antennae filiform, 0.55 mm long (approximately 2 × head length), scapus slightly shorter than pedicellus, antennal flagellum 0.43 mm long.

Thorax : thoracic terga and sutures mostly visible from dorsal view (Figs 4, 5). Mesonotal suture (MNs) absent. Sublateroscutal suture (SLSs) present. Thoracic sterna partially visible from ventral view (Figs 11, 12). Furcasternal protuberances widely separated. All legs of same general arrangement, with femora of similar size, 0.4 mm long and tibio-patellar suture present (Figs 6, 7). Foreleg with tibia and tarsus combined 0.6 mm long (delimitation of basal tarsal segments not clearly visible). Claws of all legs dissimilar (first oval and blunt, second hooked and pointed). Individual tarsal segments best observable in left hind leg (Figs 9, 10). Hind tarsus four-segmented, 0.20 mm long, first basal segment fused with tibia, three segments movable. Length of first and second segment combined 0.11 mm (exact location of articulation between first and second segment obscured), third and fourth segment approximately equal in length, and each 0.06 mm long. Both forewings preserved (Figs 1, 2, 13, 15–17), right forewing folded over, left forewing with apical portion missing and slightly distorted anterior margin distally (Figs 16, 17). Forewing 2 mm long (approximately equal to body length), 0.85 mm wide, with pronounced angle on posterior margin between CuA and CuP. Pterostigma of right forewing with three simple faintly visible crossveins. In remaining sectors of forewing, very scarce crossveins. MA2 free, not connected with MA1. CuP curved backwards near its base. Cubital field of forewing with intercalary veins, not connected to CuA. Single free marginal intercalary veins on posterior margin present, inconspicuous, well-distinguishable only in median sector of left forewing (Figs 14, 15, 17). Right hind wing poorly visible, folded alongside body. Left hind wing well visible (Figs 13, 18–20), 0.63 mm long, 0.29 mm wide (approximately 0.3 × forewing length). Small acute costal process positioned basally. Three principal longitudinal veins; first anterior vein sigmoidal, approaching costal margin distally from costal process. Second longitudinal vein bifurcated; intercalary vein positioned between its branches also distally bifurcated and followed by another simple intercalary vein (Figs 18, 19). Bifurcations in this wing sector possibly originating from fusions of basal portions of originally separate veins. Third, most posterior principal longitudinal vein simple, reaching posterior wing margin. Further two separate short veins located more posteriorly (Figs 19, 20). Single crossvein visible in costal field, in approximately 1/3 of wing length (Figs 19, 20).

Figures 13–20. 

Petracloeon carolinensis gen. et sp. nov., wing venation. 13. Wings on left side, ventral view, inserted rectangles depict position of detailed figures; 14. Detail of posterior margin of left forewing (short intercalary veins marked with arrows); 15. Generalized forewing venation based on observation of both forewings (sharp angle on posterior margin marked with arrow); 16. Right forewing venation as preserved in the fossil (veins of costal, subcostal and radial sectors are colour coded for clarity); 17. Left forewing venation as preserved in the fossil (veins of costal, subcostal and radial sectors are colour coded for clarity); 18. Left hind wing, ventral view, inserted rectangle depicts position of detailed figure; 19. Left hind wing with marked venation pattern, ventral view; 20. Detail of basal portion of left hind wing, dorsal view (short veins on posterior margin marked with black arrows, crossvein on anterior margin marked with white arrows); C – costa; CuA – cubitus anterior; CuP – cubitus posterior; IMA – intercalary vein between branches of media anterior; IMP – intercalary vein between branches of media posterior; IRP – intercalary vein between branches of radius posterior; MA – media anterior; MP – media posterior; RA – radius anterior; RP – radius posterior; ScP – subcosta posterior.

Abdomen : no colour pattern preserved on terga or sterna, distal part of abdomen damaged (Fig. 8). Cerci covered with short hair-like setae. Length of cerci unknown, only basal portions (approximately 2 mm long) preserved. Paracercus vestigial (Fig. 8).

Discussion

Attribution of Petracloeon carolinensis gen. et sp. nov.

Some of the characters we use to establish its attribution within Ephemeroptera were postulated as diagnostic for the taxon Baetoidea sensu Staniczek (1997), also known as Tetramerotarsata sensu Kluge (1997). This group was originally proposed based on morphological characters and included the families Siphlaenigmatidae and Baetidae. However, recent reconstructions suggest that Tetramerotarsata is not monophyletic (Ogden et al. 2009, 2019). According to Ogden et al. (2009), internal anatomy and molecular characters indicate that the similarities between Baetidae and Siphlaenigmatidae may be due to convergent evolution rather than homology.

Nevertheless, the morphological characters defining Tetramerotarsata according to Kluge (1997) are well-recognizable in the fossil material, and we use them for convenience, although they do not define a single, common monophyletic group, as they represent shared apomorphic characters evolved independently by two distant mayfly families. Two such characters concerning the pattern of thoracic sutures are recognizable in P. carolinensis gen. et sp. nov., namely the absence of the mesonotal suture and the presence of the sublateroscutal suture (Figs 4, 5). Wing venation characters of Tetramerotarsata include a forewing CuP curved backward near its base and a cubital field of the forewing with intercalary veins, not connected to CuA, both well-visible in P. carolinensis gen. et sp. nov. (Figs 15–17). Another character defining Tetramerotarsata is the 4-segmented tarsi with three movable segments, and the basal tarsal segment fused with the tibia. In P. carolinensis gen. et sp. nov., the same arrangement of the tarsus can be observed, best visible in the hind leg (Figs 9, 10).

We attribute P. carolinensis gen. et sp. nov. to the family Baetidae based on several diagnostic characters not shared by Siphlaenigmatidae: In the forewing, the MA2 vein is free, not connected with MA1 (Figs 15–17). This character separates Baetidae not only from Siphlaenigmatidae, but from all other mayfly families, which exhibit the MA bifurcated into MA1 and MA2 (Kluge 1997, 2004; Poinar 2011). Furthermore, single free marginal intercalary veins are present in the forewing of P. carolinensis gen. et sp. nov., well-distinguishable in the median sector of the left forewing (Figs 14, 15, 17). Such marginal intercalary veins (single or double) are typical for Baetidae (Kluge 1997, 2004). Another character supporting the attribution to Baetidae is the small hind wing with reduced venation and a small costal process situated basally. Hind wing reduction occurs several times independently within Ephemeroptera; besides Baetidae, this character is also common in Leptophlebiidae (e.g., Dominguez et al. 2006). The shape and general arrangement (size and position of the costal process) of the hind wing as present in P. carolinensis gen. et sp. nov. are typical for Baetidae. The presence of a vestigial paracercus (Fig. 8) is also consistent with the placement in Baetidae, although the paracercus is also reduced to varying degrees in other families (Kluge 1997, 2004).

Two fossil subfamilies have been described within Baetidae from the Cretaceous of Asia, namely Vetuformosinae (Poinar 2011) from Burmese amber and Palaeocloeoninae (Kluge 1997) from Taimyr amber. The former subfamily has since been synonymized with Palaeocloeoninae by Staniczek et al. (2022). Palaeocloeoninae is characterized by male eyes that are not separated into dorsal and ventral portions (Kluge 1997). Since the holotype of P. carolinensis gen. et sp. nov. is a female without enlarged eyes, it is not possible to verify this character. Among other characters of Palaeocloeoninae, contiguous furcasternal protuberances on the mesothorax are typical of this subfamily (Kluge 1997, fig. 11; Staniczek et al. 2022, fig. S2). In P. carolinensis gen. et sp. nov., the arrangement of the furcasternal protuberances more closely resembles that of extant Baetidae, with the furcasternal protuberances widely separated and the metathoracic nerve ganglion situated between them (Figs 11, 12). Palaeocloeoninae is also characterized by the absence of a tibio-patellar suture on the forelegs, which is present in P. carolinensis gen. et sp. nov. (Fig. 6). Finally, the females of Palaeocloeoninae are reported to exhibit very long antennal flagella, more than three times the head length in some species (Poinar 2011; Staniczek et al. 2022). In P. carolinensis gen. et sp. nov., the antennal flagella are much shorter, approximately 2 × head length (Fig. 3), which is a proportion commonly found in Baetidae. Based on all the character states mentioned above, we do not assign P. carolinensis gen. et sp. nov. to Palaeocloeoninae.

The higher classification of remaining Baetidae has been the subject of many revisions. The traditional division into two subfamilies, Baetinae and Cloeoninae, is considered too simplistic and does not correspond with the actual phylogeny of the family (Gattolliat et al. 2008; Cruz et al. 2021). Despite not being accepted by all and not based on phylogenetic reconstructions, the non-ranking systematics of Baetidae developed by N. Kluge in various papers remains the most comprehensive and the only available global systematics of the family (Kluge 2011, 2016, 2020, 2022; Kluge and Novikova 2011, 2016). The first main division within the clade Turbanoculata (corresponding to Baetidae excluding Palaeocloeoninae) is based on the presence or absence of the tibio-patellar suture on the forelegs at the larval, subimaginal and imaginal stages of females: in the plesiomorphon Protopatellata, this suture is absent in forelegs of all stages, while it is considered secondarily restored in females at all stages in Anteropatellata (Kluge 2011; Kluge and Novikova 2016). In P. carolinensis gen. et sp. nov., the tibio-patellar suture is present in all legs (Figs 6, 7), suggesting its attribution to Anteropatellata. The group Anteropatellata is subsequently divided into Cloeon/fg1 (or Cloeonini sensu Kluge 2016) and Baetovectata (Baetis/fg6) (Kluge 2016; Kluge and Novikova 2011). Imagos and subimagos of Cloeonini have either no hind wings or hind wings that are slender, generally with two (rarely three) simple longitudinal veins. These veins are neither bifurcated nor partially fused, and they never have additional forked veins in between. Thus, based on the hind wings, we can exclude the attribution of P. carolinensis gen. et sp. nov. to Cloeonini.

The group Baetovectata is primarily recognized by the presence of double intercalary veins on the forewings (Kluge and Novikova 2011), although there are noticeable exceptions, such as Cloeodes/g1 (including the genera Centroptella, Chopralla, and Bungona) and a few species of Callibaetis (Dominguez et al. 2006; Kluge 2017). Other autapomorphies characterizing this clade concern the shape of the gonovectes of the penis and the position of the gonostylus under the larval cuticle (Kluge and Novikova 2011); however, neither of these characters can be verified in a female imago. Consequently, P. carolinensis gen. et sp. nov. cannot belong to Cloeon/fg1, but its assignment to Baetovectata remains possible.

The main clade within Baetovectata is Baetungulata (or Baetis/fg7) (Kluge and Novikova 2011). All imagos of Baetungulata have forewings with double intercalary veins; therefore, P. carolinensis gen. et sp. nov. cannot belong to Baetungulata but may be part of Baetovectata without Baetungulata. Within Baetovectata excluding Baetungulata, some genera feature species with single intercalary veins. In Cloeodes and related genera (see Salles et al. 2016 for a complete review of the concerned genera) the hind wing is always slender with two or three simple longitudinal veins; these veins are never partially fused or bifurcated (Dominguez et al. 2006; Salles et al. 2016). The genus Callibaetis has forewings with double intercalary veins, but a few species exhibit single intercalary veins. Nevertheless, all such species of Callibaetis have hind wings with numerous crossveins, a feature that is very uncommon within Baetidae, and completely differs from P. carolinensis gen. et sp. nov.

The shape and venation of the hind wings are therefore crucial for distinguishing P. carolinensis gen. et sp. nov. from existing genera of Baetidae. Regarding this character, only a few genera within Baetungulata present some similarities: Andesiops spp. from South America, Moribaetis salvini (Eaton, 1885) from Central America, and Diphetor devinctus (Traver, 1935) from North America, which have bifurcated longitudinal veins with intercalary veins. However, like other Baetungulata, they differ from P. carolinensis gen. et sp. nov. by the presence of double intercalary veins on the forewings (Needham et al. 1935; Waltz and McCafferty 1987; Lugo-Ortiz and McCafferty 1999; Nieto 2004).

The general shape of the forewing in P. carolinensis gen. et sp. nov., especially the pronounced angle on the posterior margin of the wing between the veins CuA and CuP (Fig. 15, arrow), is rather uncommon in Baetidae, as this portion of the forewing margin is rounded in all extant genera. The presence of a similar angle is more common in other mayfly families (e.g., Siphlonuriidae, Isonychiidae, Leptophlebiidae); thus, it may represent the plesiomorphic state of the character.

Based on the analysis of the morphological characters presented above, we designate the specimen AMNH NC-VK261 as a new genus and species within Baetidae, as it cannot be confidently associated with any of the extant genera. The wing venation pattern suggests an affinity with the clade Baetovectata excluding Baetungulata (sensu Kluge and Novikova 2011). However, the general shape of the forewing suggests a more basal position within the Baetidae lineage. Knowledge about the male imago could provide crucial insights to confirm the precise taxonomic position of this genus within Baetidae. A detailed study of the male imago’s genitalia and turbinate eyes may help resolve uncertainties and establish a clearer understanding of its phylogenetic relationships.

Since the character states of the genitalia in P. carolinensis gen. et sp. nov. are unknown and the affinity to Baetovectata remains a possibility, we refrain from establishing any new higher taxon above genus level for the present.

Biogeography

The family Baetidae is currently distributed almost worldwide across all significant landmasses, except for Antarctica and New Zealand (Gattolliat and Nieto 2009). The family exhibits the greatest diversity and the highest levels of generic endemism in tropical regions (Barber-James et al. 2008). Edmunds et al. (1976) hypothesized that the primary centre of evolution of Baetidae was South America, whereas Barber-James et al. (2008) considered the family would have had a Pangean origin. As pointed out by Gattolliat and Nieto (2009), understanding the historical biogeography of Baetidae relies on a comprehensive phylogeny of the family, which is still lacking.

From the sparse fossil records of Baetidae, it is clear that they were already diversified during the Cretaceous. Baetidae from the mid-Cretaceous Burmese amber (Poinar 2011) likely originated from either Asia or the former Gondwana, being transported northward on a landmass known as the West Burma Block (Poinar 2018). In either case, the nearly contemporaneous occurrences in the Taimyr amber from Northern Asia (Kluge 1997) and in North America, as evidenced by the material described herein, suggest a nearly global distribution of this family as early as the Cretaceous. Although transoceanic dispersal has occurred in mayflies (proven, e.g., between Madagascar and continental Africa in both directions, see Monaghan et al. 2005), it likely played only a minor role in shaping their current distribution, considering their short adult lifespan and dependence on freshwater habitats. Thus, it seems reasonable to assume that the origin of Baetidae predates the main continental breakup starting in the Jurassic. This assumption aligns with the latest phylogeny of Ephemeroptera (Ogden et al. 2009), where this family was recovered as one of the basal lineages.

Conclusion

We provide the first evidence that the mayfly family Baetidae (one of the most diverse mayfly taxa worldwide) was present in North America as early as the Cretaceous. The newly discovered fossil mayfly, described herein as Petracloeon carolinensis gen. et sp. nov., enhances our understanding of Baetidae phylogeny, as it represents the oldest known occurrence of the clade Turbanoculata, which encompasses all extant Baetidae taxa. Our study may also draw scientists’ attention to the understudied inclusions in Cretaceous North Carolina amber.

Acknowledgements

We are grateful to David Grimaldi and Agnieszka Pierwola (both from the American Museum of Natural History, New York, USA) for allowing us to study the material and for their assistance during PS’s visit to the AMNH. We thank both reviewers, Arnold H. Staniczek and Roman J. Godunko, for their very helpful remarks, which improved the manuscript. PS also acknowledges support from the Grant Agency of the Czech Republic (No. 24-11498S). The study was further supported by institutional support from the Institute of Entomology, Biology Centre of the Czech Academy of Sciences (RVO: 60077344).

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