1. Introduction
Finding marine or brackish organisms in fossil resin seems a priori unlikely. However, several discoveries in the last 20 years, in the mid-Cretaceous Burmese amber, have demonstrated the possibility for aquatic animals, including marine ones, to be exceptionally preserved in Cenomanian resin (Mao et al., Reference Mao, Liang, Su, Li, Rao, Zhang, Xia, Fu, Cai and Huang2018; Xing et al., Reference Xing, Sames, McKellar, Xi, Bai and Wan2018; Yu et al., Reference Yu, Wang and Jarzembowski2019a, b; Bolotov et al., Reference Bolotov, Aksenova, Vikhrev, Konopleva, Chapurina and Kondakov2021). As far as microorganisms are concerned, Girard et al. (Reference Girard, Schmidt, Saint Martin, Struwe, Perrichot, Saint Martin, Grosheny, Breton and Néraudeau2008) have also described different microfossils included in the mid-Cretaceous Charentese amber, such as foraminifers, radiolarians, amoebae, larval spines of sea urchins, diatoms and demosponges. The gastropod discovered in Charente-Maritime is the first gastropod reported from European Cretaceous amber and is one of the exceptional marine invertebrates discovered there. Gastropods previously discovered in Cretaceous amber come mainly from Cenomanian Burmese amber and are freshwater or terrestrial species (Hirano et al., Reference Hirano, Asato, Yamamoto, Takahashi and Chiba2019; Neubauer et al., Reference Neubauer, Xing and Jochum2019a; Xing et al., Reference Xing, Ross, Stilwell, Fang and McKellar2019; Yu et al., Reference Yu, Wang and Jarzembowski2019a, revised by Neubauer et al., Reference Neubauer, Páll-Gergely, Jochum and Harzhauser2019b; Yu & Neubauer, Reference Yu and Neubauer2021; Yu et al., Reference Yu, Neubauer and Jochum2021; Balashov & Anistratenko, Reference Balashov and Anistratenko2024). Yu et al. (Reference Yu, Wang and Jarzembowski2019a) described two new species of gastropods and identified them as marine Epitoniidae, but, on revision, Neubauer et al. (Reference Neubauer, Páll-Gergely, Jochum and Harzhauser2019b) considered them terrestrial cyclophoroids. However, in association with an ammonite found in mid-Cretaceous Burmese amber, several specimens of gastropods have been attributed to the genus Mathilda (family Mathildae) (Yu et al., Reference Yu, Kelly, Mu, Ross, Kennedy, Broly, Xia, Zhang, Wang and Dilcher2019b). But, it is certainly not a Mathilda and not even a marine gastropod. Mathilda would have a heterostrophic protoconch, while this one’s protoconch is large, normally coiled and has few whorls – clearly a direct developer. This is a terrestrial species, probably Pseudopomatias or another Pupinidae (T. A. Neubauer, personal communication). Finally, the discovery of an Ellobiidae, a supralittoral gastropod, in European Cretaceous amber is an extremely rare occurrence.
2. Material and methods
2.a. Geographical and geological settings
The amber containing the gastropod described herein was collected from the quarry of Archingeay–Les Nouillers (Fig. 1), in the Charente-Maritime region (SW France) (Néraudeau et al., Reference Néraudeau, Perrichot, Dejax, Masure, Nel, Philippe, Moreau, Guillocheau and Guyot2002). The sandy base of the section, which yields lignitic clay with amber (Néraudeau et al., Reference Néraudeau, Perrichot, Dejax, Masure, Nel, Philippe, Moreau, Guillocheau and Guyot2002, fig. 2, facies A1sl), has provided fossil plants (Moreau et al., Reference Moreau, Néraudeau, Philippe and Dépré2017) and a few pyritized brackish oysters (Videt & Platel, Reference Videt and Platel2005). It was dated first as possibly uppermost Albian (100 Ma) based on palynological studies (Néraudeau et al., Reference Néraudeau, Perrichot, Dejax, Masure, Nel, Philippe, Moreau, Guillocheau and Guyot2002; Dejax & Masure, Reference Dejax and Masure2005; Peyrot et al., Reference Peyrot, Jolly and Barron2005), but more likely to be lowermost Cenomanian according to the following works (Batten et al., Reference Batten, Colin and Néraudeau2010; Peyrot et al., Reference Peyrot, Barron, Polette, Batten and Néraudeau2019). Since the first publication about the amber deposit, in 2002 (Néraudeau et al., Reference Néraudeau, Perrichot, Dejax, Masure, Nel, Philippe, Moreau, Guillocheau and Guyot2002), the Lagerstätte of Archingeay–Les Nouillers has provided hundreds of terrestrial arthropod inclusions (mainly insects, but also arachnids and myriapods) and abundant forest microorganisms (fungi), but only a few specimens of organisms linked to aquatic or foreshore environments (Perrichot et al., Reference Perrichot, Néraudeau, Tafforeau and Penney2010). Moreover, a few unpublished coastal isopods have been found, including a specimen associated with a gastropod in the same piece of amber.

Figure 1. Geographical and geological location of the amber deposit of Archingeay–Les Nouillers (white star) where Palaeoellobium decampsi gen. nov., sp. nov. has been discovered. Dark grey areas correspond to Cenomanian outcrops.
2.b. The fossiliferous content of the amber drop including the gastropod
The piece of amber is of milky caramel colour and totally opaque (Fig. 2). Its maximum length measures 35 mm, and its diameter is ca. 23 mm. It also contains a complete specimen and an isolated leg of a Blattodea, a species of Dermaptera, a species of Opiliones, and a coastal isopod.

Figure 2. Piece of amber (maximum length 35 mm) containing Palaeoellobium decampsi gen. nov., sp. nov. Before scanning in microtomography, the hardly fractured amber piece was set in a protective epoxy block for conservation purposes. Scale bar: 10 mm. Photo: P. Tafforeau, ESRF.
The fossiliferous amber sample is housed at the University of Rennes, in the collections of the Geological Institute, with the catalogue number ARC-423.
2.c. The imaging by microtomography
Propagation phase-contrast X-ray synchrotron microtomography (afterwards PPC-SrμCT) was used to image the specimen and its morphological features (Tafforeau et al., Reference Tafforeau, Boistel, Boller, Bravin, Brunet, Chaimanee, Cloetens, Feist, Hoszowska, Jaeger, Kay, Lazzari, Marivaux, Nel, Nemoz, Thibault, Vignaud and Zabler2006). The specimen was scanned following the protocols described in Lak et al. (Reference Lak, Néraudeau, Nel, Cloetens, Perrichot and Tafforeau2008) with a set energy of 30 keV (using a double Si 111 Bragg monochromator) and a 960 mm distance between the camera and the sample. Scan acquisition consisted of 1,999 images over 180 degrees, with 0.7 s of exposure time and 5.06 μ of voxel size. After the scan, the slices were reconstructed using a filtered back-projection algorithm adapted for local tomography applications (PyHST software, ESRF). The later three-dimensional processing was made using VGStudiomax 2.1 software (Volume Graphics, Heidelberg, Germany). Before scanning, the hardly fractured amber piece was set in a protective epoxy block for conservation purposes (Fig. 2).
3. Systematic palaeontology
Class GASTROPODA Cuvier, Reference Cuvier1795
Subclass HETEROBRANCHIA Burmeister, Reference Burmeister1837
Superorder EUPULMONATA Haszprunar & Huber, Reference Haszprunar and Huber1990
Order ELLOBIIDA Van Mol, Reference Van Mol1967
Family ELLOBIIDAE L. Pfeiffer, Reference Pfeiffer1854
Subfamily ELLOBIINAE L. Pfeiffer, Reference Pfeiffer1854
Genus Palaeoellobium gen. nov.
LSID urn:lsid:zoobank.org:act:317DE264-5560-407C-B053-
61DF1EE07E3D.
Type species. Palaeoellobium decampsi sp. nov.
Etymology. A combination of palaiós (in Greek) and Ellobium, type genus of the family Ellobiidae.
Diagnosis. Medium-sized, ovate shell with conical spire. Heterostrophic protoconch. Fine non-lamellar undulating ribs more prominent adapically than abapically; no spiral sculpture. Aperture moderately wide. Columellar callus moderately delimited. Columellar fold obsolete; parietal fold prominent. Outer lip sharp without marked palatal swelling. Umbilical zone puckered.
Description. As for type species.
Stratigraphic and geographic range. Uppermost Albian to lowermost Cenomanian, Charente-Maritime, SW France.
Included species. Type species only.
Palaeoellobium decampsi gen. nov., sp. nov.
(Fig. 3)

Figure 3. Palaeoellobium decampsi gen. nov., sp. nov. Holotype Arc-423.5, microtomographic reconstruction. (a–b) Dorsal views, (c) profile view, (d) apertural view, (e) apical view and (f) abapical view. Abbreviations: si – subsutural inflection; il – inner lip; pf – parietal fold; cc – columellar callus; cf – columellar fold. Scale bar: 1 mm.
LSID urn:lsid:zoobank.org:act:53B4D03D-BC81-4853-B870-13B2B718ACB6.
Derivation of name. Dedicated to Christian Décamps, the lead singer of the pop music group Ange.
Holotype. Arc-423.5 (Geological Institute of the University of Rennes, France), shell height: 10 mm, greatest width of a shell perpendicular to height: 4.9 mm (Fig. 3). The holotype corresponds to an external imprint of a shell. Within the aperture (Fig. 3d, f), some structures can be seen that could be the remains of soft anatomical parts. However, it is impossible to identify any organs.
Type locality. Archingeay–Les Nouillers area, quarry located in the village of Les Nouillers, Charente-Maritime, SW France.
Type stratum. Uppermost Albian to lowermost Cenomanian.
Shell description. Middle-sized, elongate ovate shells with conical spire; apical angle 47° (based on Fig. 3d). Heterostrophic protoconch, slightly deviated to the right in ventral view. Moderately high spire of eight weakly convex whorls. Suture narrowly incised with narrow subsutural inflexion. Last whorl convex with the convex base, representing 63% of the total height. Axial sculpture displaying approximately 15–20 ribs on the first teleoconch whorls and 25–30 ribs on the penultimate and last whorl. Fine non-lamellar undulating ribs more prominent adapically and tending to fade gradually abapically. Aperture moderately wide, posteriorly angulated, with a faintly incised basal margin and representing 53% of total height. Columellar callus moderately delimited, very weakly thickened callus rim in abapical half of aperture and poorly distinct adapically. Columellar fold obsolete. Parietal fold prominent, equally positioned centrally. Outer lip sharp without marked palatal swelling. Dense growth lines immediately behind the outer lip (Fig 2b). Umbilical zone puckered (Fig. 3f).
Discussion. The shell shape, the aperture and the heterostrophic protoconch of Palaeoellobium decampsi gen. nov., sp. nov. are reminiscent of members of the family Ellobiidae represented by a few Cretaceous genera. Proauricula (Huckriede, Reference Huckriede1967) (type species: Auricula jaccardi, de Loriol & Jaccard, Reference Loriol and Jaccard1865) from the Early Cretaceous of Eurasia differs from Palaeoellobium decampsi gen. nov., sp. nov. by having inflated, rounded teleoconch whorls and a dense network of very low lamellar ribs that do not tend to fade gradually abapically (see Huckriede, Reference Huckriede1967, pl. 16, figs 9-1; Pan & Zhu, Reference Pan and Zhu2007, fig. 4a-b). Zaptychius (Walcott, Reference Walcott1883) (type species: Zaptychius carbonaria, Walcott, Reference Walcott1883; Zaptychinae) is mainly known from the Paleozoic. However, Pan & Zhu, Reference Pan and Zhu2007 (p. 221, fig. 4a–b) described Zaptychius costatus from the Early Cretaceous of North China. This species has a sculpture of finely lamellar and flexuous axial ribs, incised spiral lines and a prominent columellar fold within the aperture. Among the rare Ellobiidae known from the European Late Cretaceous deposits, Palaeoellobium gen. nov. can be compared to two monotypic genera coming from the Santonian of Ajka (Hungary): Leopoldium (Bandel & Riedel, Reference Bandel and Riedel1994) (type species: Auricula balatonica, Tausch, Reference Tausch1886; Ellobiinae) and Auriculinella (Tausch, Reference Tausch1886) (type species: Auriculinella whitei, Tausch, Reference Tausch1886; Ellobiinae). Leopoldium balatonicum (Tausch, Reference Tausch1886) has a junior synonym, Auricula hungarica (Tausch, Reference Tausch1886) (see Bandel & Riedel, Reference Bandel and Riedel1994), and is devoid of sculpture and displays a prominent columellar fold, lacking in Palaeoellobium decampsi gen. nov., sp. nov. (see Tausch, Reference Tausch1886, pl. 2, fig. 25; Bandel & Riedel, Reference Bandel and Riedel1994, pl. 15, figs 1-2). Auriculinella whitei (Tausch, Reference Tausch1886) bears a very strong axial sculpture appearing on the early teleoconch whorls (see Bandel & Riedel, Reference Bandel and Riedel1994, pl. 15, figs 5-7) and a prominent columellar fold (see Tausch, Reference Tausch1886, pl. 2, fig. 26). Among Cenozoic and present-day taxa, Ellobium (Röding, Reference Röding1798) (type species: Ellobium aurismidae, Linnaeus, Reference Linnaeus1758; Ellobiinae) can display numerous very close-set and low axial ribs often crossed by spiral lines more developed adapically, whereas Palaeoellobium decampsi nov. gen., nov. sp., lacks spiral sculpture and has fewer but prominent ribs. Eoellobium (Harzhauser, Pacaud & Landau, Reference Harzhauser, Pacaud and Landau2023) (type species: Auricula heberti, Vasseur, Reference Vasseur1881; Ellobiinae) has a strong subsutural cord lacking in Palaeoellobium decampsi nov. gen., nov. sp. Its rugose sculpture of close-set and numerous axial ribs crossed by weak spiral threads recalls more that of Zaptychius or some Ellobium than that of Palaeoellobium. In addition, Paleoellobium n. gen. bears sparser ribs appearing earlier during the ontogeny than in Eoellobium. Although their shell shape is very different, species of Zospeum (Bourguignat, Reference Bourguignat1856) (type species: Z. spelaeum, Rossmässler, Reference Rossmässler1839; Carychinae) can have a similarly puckered umbilical zone as well as the densely aligned ribbing behind the apertural lip (Jochum et al., Reference Jochum, Michalik, Inäbnit, Kneubühler, Slapnik, Vrabec, Schilthuizen and Ruthensteiner2024). Myosotella (Monterosato, Reference Monterosato1906) (type species Myosotella myosotis, Draparnaud, Reference Draparnaud1801; Pythinae) is reminiscent of Palaeoellobium gen. nov. in its general size, teleoconch shape and sharp apertural lip with the parietal fold equally positioned centrally. However, Myosotella usually displays a stronger columellar fold with one or two additional parietal folds. Moreover, when Myosotella bears an axial sculpture, it resembles more growing striae than true ribs. They are much weaker, more numerous and more ‘close-set’ than those of Palaeoellobium n. gen. The protoconch of Myosotella is more bulbous or slightly turned more to the left (see Martins, Reference Martins1996, figs 41-60), whereas it is narrower and turned right in Palaeoellobium n. gen. Finally, although this gastropod from the Charente-Maritime amber shares characters with other Ellobiidae, clearly demonstrating its membership to this family, its particular combination of characters associating fine non-lamellar undulating ribs tending to fade abapically, a subsutural inflection, a lack of spiral sculpture and an umbilical zone puckered by growth lines is unique and easily justifies the creation of a new genus.
4. Amber source, ecology of Ellobiidae and palaeoenvironmental discussion
4.a. Amber source and taphonomic considerations
The botanical source of the amber from Archingeay–Les Nouillers is thought to be araucarian (Agathoxylon), based on the analysis of the fossil wood remains (Perrichot, Reference Perrichot2003). However, other conifers of the fossil family Cheirolepidiaceae (Brachyoxylon and Protopodocarpoxylon) could also have contributed to the resin production (Perrichot, Reference Perrichot2003). These different kinds of conifers constituted the coastal forest that produced the fossil resin that embedded the gastropod. The external imprint of the shell, associated with probable imprints of ‘remains of soft parts together with the crack’ linked to the putrefaction gases, suggests that the whole animal was trapped in the amber and not only its shell. The small size of the shell made it easy to transport (dead or alive) during strong winds or floods.
4.b. Ecology of present-day and fossil Ellobiidae
Ellobiidae are pulmonate gastropods typical of the upper and supralittoral zones of the mangroves of tropical regions (Martins, Reference Martins1980, Reference Martins1996; Harzhauser et al., Reference Harzhauser, Pacaud and Landau2023). The various genera of Ellobiinae live in somewhat different habitats. Blauneria (Shuttleworth, Reference Shuttleworth1854) lives buried in the black sediment and under rocks and rotting plant material at the high-tide mark (Marcus & Marcus, Reference Marcus and Marcus1965; Martins, Reference Martins1996). Leucophytia (Winckworth, Reference Winckworth1949) lives closer to the low-tide mark than Blauneria and Ellobium (Martins, Reference Martins1996). In the Azores, it lives under rocks buried in gravel and sometimes in the intertidal zone (Martins, Reference Martins1980). Ellobium is common on the muddy surfaces of Indo-Pacific mangroves, just below the high-tide mark, around roots and decaying wood (Berry et al., Reference Berry, Loog and Thum1967). It is also found on mangrove trunks (Piamklad et al., Reference Piamklad, Tuntiwaranurak and Dumrongrojwattana2014) or between long grass (Raven & Vermeulen, Reference Raven and Vermeulen2007). Ellison et al. (Reference Ellison, Farnsworth and Merkt1999) and Groh (Reference Groh and Poppe2010) discussed Ellobium as a mangrove-associated gastropod genus. They concluded that while a general affinity to the mangrove ecosystem can be stated for the genus, an obligate relationship with mangrove trees is not obvious for most of the species. Harzhauser et al. (Reference Harzhauser, Pacaud and Landau2023) also suggest that the lowest common denominator for the Indo-West-Pacific species of Ellobium in terms of habitat is an occurrence in the saltmarshes above the high-tide line in close vicinity of the mangroves. There are few data on the ecology of fossil Ellobiidae. However, in the Paleogene of the Paris Basin, they are found in coastal marine sediments from the Ypresian onwards (DM personal observations). From the European Early Cretaceous, Huckriede (Reference Huckriede1967: 204) found Proauricula in freshwater and brackish facies. The palaeoenvironment of the Santonian of Aijka coal swamps is well characterized by its gastropod fauna, indicating freshwater and more or less brackish influence (Bandel & Riedel, Reference Bandel and Riedel1994).
4.c. Palaeoenvironmental discussion
The coastal forest of conifers that produced the fossil resin embedding the gastropod does not correspond to the habitat of the ellobiids. Another coastal macroorganism has been found associated with the ellobiid in the same amber piece, a ligiid crustacean, typical of rocky foreshore environments. Thus, the amberiferous forest was probably bordering the foreshore, and some coastal organisms got stuck in resin flow coming from the tree roots or falling from the branches. A few other terrestrial arthropods are also present in the same amber drop and highlight the trapping by the same resin flow of both coastal species from the foreshore and crawling insects from the forest margin. It can be noticed that there is no direct fossil evidence of mangrove trees with coastal angiosperms in Cretaceous times, since typical modern mangrove flora appears to have originated during Paleocene times and was pantropic in the Eocene (Plaziat et al., Reference Plaziat, Cavagnetto, Koeniguer and Baltzer2001). However, other kinds of interfaces between marine biotopes and conifer forests were probably developed on the coastline of Western Europe.
Acknowledgements
The authors want to thank Vincent Perrichot for the entomological information about the amber drop containing the ellobiid, Malvina Lak for her contribution to the discovery on survey and microtomographical imaging of the specimen, Carmen Soriano for her contribution to the new 3D rendering of the specimen and the European Synchrotron Radiation Facility of Grenoble for the technical support of the microtomography, Ninon Robin (University of Rennes) for her technical help, Quentin Wackenheim (MNHN) for the information about ellobiids and Bernard Landau (Naturalis Biodiversity Center, Leiden) for English proofreading the manuscript. The authors are greatly indebted to the reviewers Thomas A. Neubauer (Bayerische Staatssammlung für Paläontologie und Geologie, München, Germany), Adrienne Jochum (Natural History Museum Bern, Switzerland) and the editor for their useful corrections and suggestions improving the original manuscript. This work was supported by the ANR Project AMBRACE (coord. D. Néraudeau).
Competing interests
None.


