# New data on terrestrial gastropods (Gastropoda: Cyclophoroidea) from mid-Cretaceous Burmese amber, with descriptions of two new species in the genus Euthema (Diplommatinidae).

Jean-Michel Bichain, M. Szabó, I. Szenti, Á. Kokavecz, B. Páll-Gergely

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Jean-Michel Bichain, M. Szabó, I. Szenti, Á. Kokavecz, B. Páll-Gergely. New data on terrestrial gastropods (Gastropoda: Cyclophoroidea) from mid-Cretaceous Burmese amber, with descriptions of two new species in the genus Euthema (Diplommatinidae). Zoosystematica Rossica, 2025, 34 (2), pp.336. 10.31610/zsr/2025.34.2.336. hal-05533261

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New material of terrestrial gastropods (Gastropoda: Cyclophoroidea) from mid-Cretaceous
Burmese amber with description of two new species within the genus *Euthema*
(Diplommatinidae)

J.-M. Bichain*, M. Szabó, I. Szenti, Á. Kokavecz & B. Páll-Gergely

Jean-Michel Bichain, Société & Musée d'Histoire naturelle et d'Ethnographie de Colmar, 68000 Colmar, France. Email: jean-michel.bichain@museumcolmar.org
https://orcid.org/0000-0003-3849-9364

Márton Szabó, Hungarian National Museum Public Collection Centre, Hungarian Natural History Museum, Department of Palaeontology and Geology, H-1083 Budapest, Ludovika tér. 2, Hungary. Email: szabo.marton.pisces@gmail.com and ELTE Eötvös Loránd University, Institute of Geography and Earth Sciences, Department of Palaeontology, H-1117 Budapest, Pázmány Péter sétány 1/C, Hungary. e-mail: martonszabo@staff.elte.hu
https://orcid.org/0000-0002-3233-7797

Imre Szenti, Interdisciplinary Excellence Centre, Department of Applied and Environmental Chemistry, University of Szeged, Rerrich Béla tér 1, H-6720, Szeged, Hungary. Email: szenti.imre@szte.hu
https://orcid.org/0000-0002-4602-808X

Ákos Kokavecz, Interdisciplinary Excellence Centre, Department of Applied and Environmental Chemistry, University of Szeged, Rerrich Béla tér 1, H-6720, Szeged, Hungary. Email: kakos@chem.u-szeged.hu
https://orcid.org/0000-0003-0716-9557

Barna Páll-Gergely, Department of Water Management and Natural Ecosystems, Albert Kázmér Faculty of Agricultural and Food Sciences of Széchenyi István University, Vár 2., 9200 Mosonmagyaróvár, Hungary. Email: pallgergely2@gmail.com
https://orcid.org/0000-0002-6167-7221
**Abstract.** Mid-Cretaceous Burmese amber preserves an exceptionally diverse assemblage of operulate landsnails. We describe here two new diplommatinid species: *Euthema convexispira* Bichain et Páll-Gergely, sp. nov. and *Euthema torokzselenszkyi* Páll-Gergely et Szabó, sp. nov. We also illustrate newly discovered specimens of two previously described taxa: *Hirsuticyclus canaliculatus* Yu, 2022, notably revealing a multispiral operculum, and *Cretadiostoma caperatum* Yu, Zhuo et Páll-Gergely, 2023, providing additional data on aperture morphology and whorl proportions. We also report on three specimens that are here tentatively attributed to *Euthema cf. annae* Balashov, 2021 and to the genera *Euthema* and *Pulchraspira*.

**Key words:** Burmese amber, mid-Cretaceous, terrestrial gastropods, Cyclophoridae, Diplommatinidae, Pupinidae, *Euthema convexispira* sp. nov., *Euthema torokzselenszkyi* sp. nov., *Euthema* cf. *annae*, *Hirsuticyclus canaliculatus*, *Cretadiostoma caperatum*, new species.

**ZooBank Article LSID:** to be completed once the MS has been accepted
**Introduction**

The fossil record of terrestrial gastropods remains particularly sparse, especially in the Palaeozoic and Early Mesozoic. Only a limited number of taxa have been documented prior to the Jurassic (Neubauer, 2024). This scarcity hampers the testing of hypotheses about the dynamics of putative terrestrial radiations or events of terrestrialization from non-marine or freshwater ancestors (Jochum et al., 2021; Vermeij & Watson-Zink, 2022).

Burmese amber from the Hukawng Valley (the so-called burmite) in north-eastern Myanmar represents a major exception to the rarity of Mesozoic snail fossils. Indeed, Burmese amber, dated to the earliest Cenomanian (Shi et al., 2012), provides over two thousand taxa ranging from protists to vertebrates (Ross 2025) and is therefore considered the most species-rich amber deposit from the Cretaceous and one of the most diverse from the Mesozoic (Grimaldi & Ross, 2017). Among them, 30 terrestrial (Yu et al., 2018, 2021b; Hirano et al., 2019; Neubauer et al., 2019a, 2019b; Balashov et al., 2020, 2021; Bullis et al., 2020; Yu, 2020; Balashov, 2021a, 2021b; Jochum & Neubauer, 2021; Yu & Neubauer, 2021; Yu, 2021; Bichain et al. 2022; Yu et al. 2023) and three aquatic gastropod species (Bullis et al., 2020; Yu et al., 2021a; Salvador & Yu, 2022; Balashov & Anistratenko, 2024) have been described since 2018.

These land snails embedded in Burmese amber offer exceptionally preserved shells, with characters such as periostracal hairs (Neubauer et al., 2019b; Yu, 2021), detailed aperture structure (Yu, 2021), and even opercula or soft tissues (Xing et al., 2019; Bullis et al., 2020; Jochum et al., 2021). All are operculate and belong almost exclusively to the superfamily Cyclophoroidea (Cyclophoridae with 8 species, Diplommatinidae with 9 species, Pupinidae with 11 species), a group of over 3,000 extant species that are characteristic of tropical forests and limestone outcrops in East and South Asia. The only exception is *Hydrocena praecursor* T. Yu & Neubauer, 2021, belonging to family Hydrocenidae (see Yu & Neubauer 2021). Based on molecular phylogeny and alternative reinterpretations of fossils for calibration, Hirano et al. (2019) estimate that Cyclophoroidea originated in the mid to late Mesozoic (Jurassic to Cretaceous) and that all extant families of Cyclophoroidea diversified during the late Cretaceous and Paleogene. Consequently, Burmese amber snails provide a rare and exceptional insight into the putative diversification stage of the group.

In this paper, we describe two new species of Diplommatinidae from Kachin amber and illustrate new specimens of *Hirsuticyclus canaliculatus* Yu, 2022 (Cyclophoridae), particularly highlighting the presence of a multispiral operculum, and *Cretadiostoma caperatum* Yu, Zhuo & Páll-Gergely, 2023 (Pupinidae). We also illustrate three specimens that are here attributed to *Euthema cf. annae*
Balashov, 2021 and to the genera *Euthema* and *Pulchraspira*. Additionally, we present a summary table comparing the main morphological characters of all published species of Diplommatinidae found in the amber deposits of northeastern Myanmar. Finally, we discuss the generic position of the hereby introduced new species and their significance for understanding the evolutionary history of the group.

## Material and methods

The amber pieces were legally obtained before June 2017, prior to the political unrest of November 2017 (Haug et al., 2020), from a former amber mine located near Noije Bum Village in the Hukawng Valley (Kachin State, Northern Myanmar). This amber deposit is located on the West Burma block (WBB), a terrane that migrated from the south-east of Gondwana across the Tethys Ocean during the Jurassic and Cretaceous and then collided with Asia in the Paleogene (e.g. Seton et al., 2012; Westerweel et al., 2019). Radiometric data established an early Cenomanian age (98.79 ± 0.62 Ma) for Kachin amber, based on zircons from volcanic clasts found within the amber-bearing sediments (Shi et al., 2012). Ammonites found in the amber-bearing bed and within amber fragments corroborate a late Albian/early Cenomanian age (Yu et al., 2019).

Photographs were taken using a Zeiss Axio Zoom V16 equipped with a colour camera DeltaPix 20MP CMOS EXMOR at the "Geochemistry, ISotopes, Morphometrics and mOlecular ecology" platform (GISMO) of the *Biogéosciences* Laboratory (Université Bourgogne Europe, CNRS, UMR 6282, 21000 Dijon, France). All images are digital microphotography composites obtained from several individual focal planes (ca. 50) stacked automatically using the Mosaic V2.1 software to increase the depth of field.

The shell for samples numbered MHNE.2024.06.01 to MHNE.2024.06.05 was also scanned using X-ray micro-computed tomography (EasyTom S) on the GISMO platform. The scans produced a three-dimensional output with 7 µm voxels under a 110 kV and 90 µA X-ray tube. The scanned CT data were modelled and visualised by the GISMO platform staff using Fiji 1.53e (Schindelin et al., 2012) and Slicer 3D version v5.6.2 software.

X-ray CT measurements for the holotype of *Euthema torokzselenszkyi* sp. nov. (HNHM XY) were performed at the University of Szeged (Hungary), using a Skyscan 2211 (Skyscan, Bruker, Belgium) with a resolution (pixel size) of 1.2 µm. High-resolution images were acquired with a source voltage of 110 kV, a current of 400 µA, and an exposure time of 125 ms. The CT data were reconstructed using beam-hardening correction, post-alignment, and ring artifact correction, as implemented in the NRecon reconstruction software (Skyscan, Bruker, Belgium). For 3D
visualization, CT-Vox 3D Micro-CT Volume Rendering software (Skyscan, Bruker, Belgium) was
used.

The amber pieces numbered MHNE.2024.06.01 to MHNE.2024.06.05 were housed in the mollusc
collection of the Museum of Natural History and Ethnography in Colmar (MHNEC), France. The
amber pieces numbered HNHM PAL 2025.24.1. to HNHM PAL 2024.25.1. were housed in the
invertebrate paleontological collection of the Hungarian National Museum Public Collection
Centre, Hungarian Natural History Museum in Budapest (HNHM), Hungary.

**Results**

Class **Gastropoda** Cuvier, 1795

Subclass **Caenogastropoda** Cox, 1960

Order **Architaenioglossa** Haller, 1892

Superfamily **Cyclophoroidea** Gray, 1847

Family **Cyclophoridae** Gray, 1847

Genus *Hirsuticyclus* Neubauer, Xing et Jochum, 2019

**Type species.** †*Hirsuticyclus electrum* Neubauer, Xing et Jochum, 2019, by original designation.

**Distribution.** Only known from Kachin amber. Cenomanian (mid-Cretaceous), ca. 99 Ma.

† *Hirsuticyclus canaliculatus* Yu, 2022

*Hirsuticyclus canaliculatus* Yu, 2022: 4, figs 2–3.

Figs 1–2

**Type material.** Holotype (NIGP176247) and 2 paratypes (NIGP176248, NIGP176249) housed at
the Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese
Academy of Sciences (NIGPAS) (figures in the original description were examined).

**Type locality and horizon.** Noije Bum Village, Tanaing Township, Myitkyina District, Kachin State, northern Myanmar (26°15′N, 96°33′E); unnamed horizon, mid-Cretaceous, upper Albian-lower Cenomanian.
**Material examined.** A single shell and operculum preserved in an elongated ovoid amber piece measuring 22 mm (length) × 9.5 mm (width) × 4 mm (depth) (Fig. 1A–D), deposited at the Museum of Natural History and Ethnography in Colmar, France (MHNEC) and registered under the collection number MHNE.2024.06.03. Small peripheral part of the shell and operculum were destroyed during the polishing of the amber piece, allowing these structures to be observed in cross-section.

**Additional description.** The newly found shell is also low turbinate to almost discoidal, consisting of 4.5-5 whorls (Fig. 1B). The shell is up to 10.5 mm in diameter, the last whorl being about 1/4 of the maximum diameter. The protoconch appears tiny, smooth and slightly rounded (Fig. 1C). The teleoconch bears raised spiral keels, broadly blunt, deeply incised and almost evenly distributed over the surface of the shell (Fig. 1B, 1E–F). The keels are separated by deep concavities less than one keel wide. A peri-umbilical keel is also present which is higher, wider and rounder than all the other keels and which joins the basal part of the peristome (Figs 1E–G, 2A). There are about 10 keels between the suture and the peri-umbilical keel (Fig. 2B), and 5-6 keels inside the umbilicus (Fig. 2C). Contrary to the original description (Yu 2022), very fine and regular growth lines are visible on this new specimen, especially at the end of the body whorl near the aperture (Fig. 1F). The umbilicus is round, very large, up to 4.8 mm in diameter, about 1/2.3 of the shell width (Fig. 1E). The aperture is elliptical or round, clearly inclined to the columellar axis and up to 2.7 mm in diameter. The peristome appears to be enlarged and reflected, especially in its basal part, where the peristome joins the peri-umbilical keel. There is also a widened fold near the suture and the beginnings of a canal as described by Yu (2022). The lower part of the apertural lip is greatly enlarged, with a channel on the lower part of the peristome (Fig. 1G) as described by Yu (2022). However, the channel of our specimen is more strongly developed than those in the original description. The operculum (Fig. 1G–1H.) is a sub-circular disc up to 2.3 mm in diameter, thick, multispiral with about 6 lamellae, the largest are indented and acuminate at their periphery (Fig. 1H). It is probably horny (proteinaceous), and not calcareous. The nucleus is central, protuberant and bulged.

**Remarks.** This specimen is very close to the two paratypes (NIGPI176248 and NIGP176249) illustrated by Yu (2022: Figs. 3c, 3g and 3i), especially with regard to the very prominent periumbilical keel, which joins the peristome at where the basal canal is formed.
As some traits of the operculum are used to define genera in existing groups (e.g. Kobelt 1902; Egorov, 2009; Sutcharit et al., 2014; Tongkerd et al., 2023), this specimen may provide important insights to the systematics of Cyclophoridae in Burmese amber.

Family Diplommatinidae L. Pfeiffer, 1856

Genus *Euthema* Yu, Wang et Pan, 2018

*Euthema* Yu, Wang et Pan, 2018: 255.

*Paleodiplommatina* Bullis, Herhold, Czekanski-Moir, Grimaldi et Rundell, 2020: 5. (Type species: *Paleodiplommatina spelomphalos* Bullis, Herhold, Czekanski-Moir, Grimaldi et Rundell, 2020 [as for genus], by original designation); synonymized by Balashov (2021a).

*Xenostoma* Bullis, Herhold, Czekanski-Moir, Grimaldi et Rundell, 2020: 6. (Type species:

*Xenostoma lophopleura* Bullis, Herhold, Czekanski-Moir, Grimaldi et Rundell, 2020 [as for genus], by original designation); synonymized by Balashov (2021a).

**Type species.** †*Euthema naggsi* Yu, Wang et Pan, 2018, by original designation.

**Distribution.** Only known from Kachin amber. Cenomanian (mid-Cretaceous), ca. 99 Ma. At present, the genus *Euthema* is represented in the Hkamti amber of northern Myanmar (Albian, Early Cretaceous) by a single described species, †*Euthema myanmarica* Balashov, 2021.

† *Euthema cf. annae* Balashov, 2021

*Euthema annae* Balashov, 2021a: 2, figs 1a-1d
Fig. 3

**Type material.** Holotype and paratype, in a single piece of amber (SIZK GT 7174), are housed in the collections of terrestrial molluscs of the I.I. Schmalhausen Institute of Zoology of National Academy of Sciences of Ukraine (Kyiv).

**Type locality and horizon.** Hukawng Valley (Kachin, northern Myanmar); lowermost Cenomanian (mid-Cretaceous), ca. 99–98 Ma.

**Material examined.** A shell preserved in an ovoid amber piece measuring 24 mm (length) × 15 mm (width) × 5 mm (depth) (Fig. 3A), deposited at the Museum of Natural History and Ethnography in Colmar, France (MHNEC) and registered under the collection number MHNE.2024.06.01.
**Horizon of material examined.** Amber mine in the Hukawng Valley, near Noije Bum Village (Kachin State, Myanmar); unnamed horizon, mid-Cretaceous, lower Cenomanian (98.8 ± 0.6 Ma).

**Description.** Shell dextral, cylindrical in shape, consisting of about 6 whorls (Figs. 3B–3C). Protoconch conical, consisting of about 1-2 smooth whorls. Teleoconch whorls rounded, third whorl slightly shouldered (Fig. 3C); penultimate and last whorl (with the exception of the last half whorl) slightly angled; last half whorl slightly compressed. Surface ornamented by prominent ribs, approximately 30 ribs on the ventral side of the last whorl. Umbilicus open, occupies ca. one third of shell width. Aperture up to 0.67 mm high, slightly inclined to the columellar axis, sub-circular to elliptical, weakly heart-shaped, flattened at the top and angular at the junction with the last whorl. Inner peristome slightly protruding, outer peristome thickened, enlarged and reflected. The two free lateral margins of the peristome are curved in an S-shape (Fig. 3D). The last whorl behind the aperture is clearly constricted, with a temporary reduction in diameter before returning to a size similar to its pre-constriction width. This latter region probably indicates the position of the operculum when the animal was retracted to the shell.

**Measurements.** SH (shell height): ca. 2 mm, SW (shell width): ca. 0.75 mm.

**Remarks.** The examined specimen shows a close overall resemblance to *Euthema annae* Balashov, 2021 (described by Balashov 2021a) in shell size, general outline and sculpture. However, *E. annae* seems to have a narrower umbilicus, more ribs on the penultimate whorl and does not seem to have the constriction of the last whorl just behind the aperture (Table 1). The last whorl of this new specimen is not conspicuously narrower than the penultimate whorl, but it is in case of *E. annae*. A reliable comparison between the two forms is currently hampered by the limited number of available views and the absence of comparable orientations in the published figures. The specimen illustrated here is documented only in lateral view, whereas *E. annae* was illustrated primarily in frontal and apertural views (Balashov, 2021a), preventing a precise assessment of several potentially diagnostic characters, including the width of the umbilicus, the relative proportions of the last and penultimate whorls, and the degree of constriction of the last whorl. Moreover, the number of ribs, the constriction of the penultimate whorl, and the general morphology of the aperture appear broadly similar in both forms based on the available illustrations. Given the limited knowledge of intraspecific variability in *Euthema* species from Burmese amber, these characters cannot presently be considered sufficient to justify the description of a new species.
The absence of non-destructive imaging data (e.g. X-ray computed tomography) for the present specimen further limits the assessment of potentially informative internal characters. Additional material, including specimens documented in comparable orientations and preferably analysed using tomographic techniques, will be necessary to evaluate whether the observed shell morphology falls within the variability of *Euthema annae* or represents a distinct taxon. Pending such data, we conservatively assign the present specimen to *Euthema cf. annae*.

† *Euthema convexispira Bichain et Páll-Gergely, sp. nov.*

Fig. 4

**Holotype.** A shell preserved in a rectangular amber piece measuring 15 mm (length) × 13 mm (width) × 5 mm (depth) (Fig. 4A–D), deposited at the Museum of Natural History and Ethnography in Colmar, France (MHNEC) and registered under the collection number MHNE.2024.06.05.

**Type locality and horizon.** Amber mine in the Hukawng Valley, near Noije Bum Village (Kachin State, Myanmar); unnamed horizon, mid-Cretaceous, lower Cenomanian (98.8 ± 0.6 Ma, see Shi et al. 2012).

**Diagnosis.** Shell dextral, elongated cylindrical; consisting of ca. 6.5 convex whorls separated by a deep suture; aperture circular; shell surface covered with regularly, narrowly spaced radial ribs over the entire teleoconch; no spiral striation; aperture reaches the middle of penultimate whorl; last whorl slightly constricted; no periumbilical keel.

**Description.** Shell dextral, very small, cylindrical in shape, consisting of about 6.5 whorls (Fig. 4B). Protoconch smooth and bulged with about 1-2 whorls. Teleoconch whorls wider than high, periphery rounded and distinctly convex. Sutures slightly oblique, distinct and deeply impressed. Penultimate whorl regularly coiled, larger and higher than the last whorl. Last whorl slightly constricted (Fig.4, F, G). Sculpture of regularly, narrowly spaced radial ribs on entire teleoconch, no spiral striation. About 35 and 40 ribs on the ventral side of the penultimate and last whorl, respectively. Aperture almost round, up to 0.6 mm high, inner peristome slightly protruding, peristome circular, continuous (Fig. 4G); outer peristome sharp, perpendicular to surface of last whorl; boundary between the two peristomes is clearly visible. Aperture (i.e. the parietal part of the peristome) reaches ca. the centre of the last whorl. Umbilicus open, occupies ca. one quarter of shell width.
**Measurements.** SH (shell height): ca. 1.86 mm; SW (shell width): ca. 1.0 mm.

**Etymology.** From Latin *convexus* (convex, round) and *spira* (spiral, whorl), referring to the very convex whorl's periphery of the new species.

**Differential diagnosis.** The shell of *Euthema convexispira* sp. nov. is quite similar in size and general shape to that of *Euthema truncatellina* Balashov, Perkovsky & Vasilenko, 2020, with which it shares convex whorls separated by deep sutures (Table 1). However, in *E. truncatellina*, the diameter of the third whorl is wider than all the others, the aperture (=parietal part of the peristome) reaches the suture, and the umbilicus is narrower. *Euthema annae* has a much narrower last whorl compared to the penultimate whorl (Table 1). *Euthema dilatata* is also cylindrical, but its height is much smaller compared to its width than in the new species (Table 1).

† *Euthema torokzselenszkyi* Páll-Gergely et Szabó, sp. nov.

Fig. 5

**Holotype.** A shell preserved in an ovoid amber piece measuring 12 mm (length) × 11 mm (width) (Fig. 5A–C), deposited at the Hungarian Natural History Museum and registered under the collection number HNHM PAL 2025.24.1.

**Type locality and horizon.** Amber mine in the Hukawng Valley (Kachin State, Myanmar); unnamed horizon, mid-Cretaceous, lower Cenomanian (98.8 ± 0.6 Ma, see Shi et al., 2012).

**Diagnosis.** The combination of the cylindrical shell, the rather weak ribs, a moderately expanded peristome, an aperture reaching the middle of body whorl, and the narrow, funnel-shaped umbilicus distinguishes this species from its congeners.

**Description.** Shell dextral, almost cylindrical in shape, but the last whorl is slightly narrower than the penultimate one; entire shell consisting of ca. 6 whorls (Fig. 5D). Protoconch rather domed, consisting of about 1 smooth and round whorl (Fig. 5H). The shell reaches nearly its maximal diameter after 2 whorls. Teleoconch whorls rounded (Fig. 5D–G). Penultimate whorl is the widest, last whorl slightly narrower. No obvious constriction visible on the last whorl; just above the aperture, the last whorl shows a small crack, which may be artefact or a weak constriction. Surface ornamented by rather straight, fine, low ribs, ca. 40 on a half whorl.
Aperture as high as wide, up to 0.6 mm high; subcircular in shape and reaches ca. half of the
penultimate whorl in standard apertural view (Fig. 5D). Peristome normally developed, inner
peristome blunt, slightly protruding, outer peristome expanded, and boundary between the two
peristomes clearly visible. There is a low denticle-like structure at the meeting point of the
columellar and parietal regions, this seems to continue inside the shell as a gradually widening
lamella (see also Remarks). Umbilicus open, funnel-shaped, with a very weak, blunt periumbilical
angulation (Fig. 5I).

**Measurements.** SH (shell height): 2.14 mm, SW (shell width): 1.04 mm.

**Etymology.** The name honours Tamás Török-Zselenszky (1974–), Hungarian musician, writer and poet, good friend of author MSz.

**Differential diagnosis.** The most similar species is *E. myanmarica* Balashov, 2021 (described in Balashov, 2021b), which is known from the older Hkamti amber. That species has a slightly more slender shell shape, stronger ribs, and the outer peristome is expanded, but not reflected (Table 1).

**Remarks.** *Euthema torokzselenszkyi* sp. nov. can be distinguished from *Euthema myanmarica*

Balashov, 2021 by a combination of stratigraphic and morphological characters, which support its
recognition as a distinct species.

The two taxa are separated by a significant temporal gap. *E. myanmarica* was described from
Hkamti amber, which is dated to around 110 million years ago (Ma) (Albian), whereas *E.
torokzselenszkyi* sp. nov. originates from Hukawng (Kachin) amber, which is dated to the lower
Cenomanian stage (98.8 ± 0.6 Ma). This temporal separation of approximately 10 million years is
significant within a lineage otherwise known for its morphological conservatism and is consistent
with the two taxa having evolved independently.

Morphologically, *E. myanmarica* is characterised by a strong and well-developed periumbilical keel
extending along the last whorl, explicitly highlighted as one of its most diagnostic features
(Balashov, 2021b: table 1, remarks). In contrast, *E. torokzselenszkyi* lacks such a pronounced
structure. The umbilical region of the new species shows, at most, a very weak and blunt angulation
which cannot be compared in terms of strength, extent or sharpness to the periumbilical keel
described and illustrated for *E. myanmarica*.

The two species also differ in rib density and morphology. *Euthema torokzselenszkyi* sp. nov.
exhibits relatively fine, low ribs, with approximately 40 ribs on a half whorl, whereas *E.*
*myanmarica* shows fewer, more robust ribs (ca. 25 on the apertural half of the penultimate whorl), as documented in the original description and comparative table (Balashov, 2021b).

A further clear distinction concerns apertural armature. *Euthema torokzselenszkyi* sp. nov. has a low, denticle-like structure at the junction of the columellar and parietal regions that continues internally as a lamella-like structure, as revealed by microCT imaging. No comparable denticle or internal lamella has been reported or illustrated for *E. myanmarica*, whose aperture was described as lacking any visible internal structures. The lamella-like structure inside the last whorl (Fig. 5J–M) may represent the first inner lamella reported in diplommatinids found in Burmese amber and emphasizes the importance of CT imaging. It is questionable whether this structure is homologous with the columellar lamellae of other Diplommatinidae (see e.g. Neubert & Bouchet, 2015; Nurinsiyah & Hausdorf, 2017), which usually ends in the aperture on the lower part of the columella, not as high as in this specimen. At the moment, we cannot exclude the possibility that this lamella represents a preservational artefact, but the inner part of the shell is not broken, so it is probably not a part of the inner shell.

Finally, the apertural morphology differs between the two taxa. The aperture of *E. torokzselenszkyi* sp. nov. is more markedly trumpet-like, with a more strongly expanded and partially reflected outer peristome. In contrast, the apertural expansion of *E. myanmarica* is less pronounced, giving the aperture a proportionally less flared appearance.

Taken together, these differences (combining a substantial stratigraphic separation with consistent distinctions in umbilical morphology, rib density, apertural dentition, and overall apertural shape) support the interpretation of *Euthema torokzselenszkyi* sp. nov. as a distinct species from *Euthema myanmarica* Balashov, 2021.

† *Euthema* sp.

Fig. 6

**Material examined.** A shell preserved in an ovoid amber piece measuring 13.5 mm (length) × 9.5 mm (width) × 2.5 mm (depth) (Figs. 6A–D), deposited at the Museum of Natural History and Ethnography in Colmar, France (MHNE) and registered under the collection number MHNE.2024.06.04.

**Type locality and horizon.** Amber mine in the Hukawng Valley, near Noije Bum Village (Kachin State, Myanmar); unnamed horizon, mid-Cretaceous, lower Cenomanian (98.8 ± 0.6 Ma).
**Description.** Shell dextral, almost cylindrical in shape, consisting of about 5-6 whorls (Fig. 6B). Protoconch low conical, consisting of about 1-2 smooth and round whorls. The first whorls are irregularly tightly coiled and much narrower than the third and subsequent whorls. Teleoconch whorls rounded, last whorl shouldered and flattened in the middle (Fig. 6C-F). Penultimate whorl regularly coiled, slightly narrower or as high as the last whorl. Last whorl not constricted. Surface ornamented by almost S-shaped and prominent ribs, separated by concave and flat spaces of varying width. About 40 and 32 ribs on the ventral side of the penultimate and last whorl, respectively. Umbilicus open, shallow and narrow, with a periumbilical keel (Fig. 6C). Aperture as high as wide, up to 0.60 mm high; subcircular in shape; free part of peristome thin, not thickened, rounded and slightly enlarged basally; columellar lip almost straight and reflected on the umbilicus.

**Measurements.** SH (shell eight): ca. 1.75 mm, SW (shell width): ca. 1.05 mm.

**Remarks.** The shape of the aperture and the absence of a clearly developed peristome suggest that this is the shell of a subadult specimen. This makes attribution to any of the species described within the genus *Euthema* difficult, although it seems that based on shell shape alone, this specimen may represent an unknown species.

Genus †*Pulchraspira* T. Yu, Salvador et Jarzembowski, 2021

*Pulchraspira* T. Yu, Salvador et Jarzembowski, 2021: 5.

**Type species:** †*Pulchraspira teneristoma* T. Yu, Salvador et Jarzembowski, 2021, by original designation.

**Distribution.** Only known from Kachin amber. Cenomanian (mid-Cretaceous), ca. 99 Ma.

† *Pulchraspira* sp.

Fig. 7

**Material examined.** A shell (Fig. 7) preserved in an amber piece deposited at the Hungarian Natural History Museum and registered under the collection number HNHM PAL 2024.25.1.

**Locality and horizon.** Amber mine in the Hukawng Valley, near Noije Bum Village (Kachin State, Myanmar); unnamed horizon, mid-Cretaceous, lower Cenomanian (98.8 ± 0.6 Ma).

**Measurements.** SH (shell eight): 3.26 mm, SW (shell width): ca. 1.24 mm.
**Remarks.** *Pulchraspira teneristoma* T. Yu, Salvador et Jarzembowski, 2021 is characterized by strongly expanded outer peristome (Table 1) and peculiarly shaped whorls that are described as "strongly stepped and compressed" (Yu et al., 2021). The whorls bear a blunt carina, and the lower part of the whorls is flattened, resulting in a spiralling funnel. It seems that in the original description the holotype (Yu et al., 2021: fig. 2A–F) has whorls of such shape, and only the last ca. half whorl is rounded. One of the paratypes (Yu et al., 2021: fig. 2G–H) is similar to the holotype, while it seems that the other holotype (Yu et al., 2021: fig. 2I–K) has the last whorl rounded. In our specimen, approximately the last one and half whorl is rounded, which may mean that although it extends the morphological variability of *Pulchraspira teneristoma*, but it is not a species of its own. Neubauer et al. (2019) moved two species, originally described as *Epitonium* (*Epitonium*) zhuoi Yu, Wang & Jarzembowski, 2019 and *Epitonium* (*Papyriscala*) lyui Yu, Wang & Jarzembowski, 2019, to the genus *Pseudopomatias* based on similarity of extant members of that genus (see Páll-Gergely et al., 2015). We note that small those two *Pseudopomatias* species and *Pulchraspira teneristoma* share the conical, strongly ribbed shell and the ca. 4 mm size, based on which, they may belong to Pupinidae as well as Diplommatinidae.

Family **Pupinidae** L. Pfeiffer, 1853

Genus †*Cretadiostoma* Yu, Zhuo et Páll-Gergely, 2023

**Type species.** †*Cretadiostoma caperatum* Yu, Zhuo et Páll-Gergely, 2023, by original designation.

**Distribution.** Only known from Kachin amber. Cenomanian (mid-Cretaceous), ca. 99 Ma.

† *Cretadiostoma caperatum* Yu, Zhuo et Páll-Gergely, 2023

Fig. 8

**Type material.** Holotype (NIGP179878) and 4 paratypes (NIGP179877, NIGP179879, NIGP179880, NIGP179881) housed at the Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS) and 1 paratype (BXAM-BA-WN-001) housed at the Beijing Xiaochong Amber Museum.

**Type locality and horizon.** Noije Bum Village, Tanaing Township, Myitkyina District, Kachin State, northern Myanmar (26°15′N, 96°33′E); unnamed horizon, mid-Cretaceous, upper Albiane lower Cenomanian.
**Material examined.** A single shell preserved in an ovoid amber piece measuring 27 mm (length) × 16.5 mm (width) × 6 mm (depth) (Fig. 8A), deposited at the Museum of Natural History and Ethnography in Colmar, France (MHNEC) and registered under the collection number MHNE.2024.06.02.

**Additional description.** The newly found shell is also high-spired, cylindrical with domed apex, about 3.25 times higher than wide, consisting of about 7-7.5 whorls (Fig. 8B-C). The shell reaches up to 7.8 mm in high and 2.4 mm in diameter. The protoconch appears smooth (Fig. 8F). The third whorl is also the widest, while the shell diameter decreases slightly towards the aperture. The first whorls are practically smooth; ribbing begins near the adapical suture of the antepenultimate. Penultimate and last whorls are rather irregularly, more or less finely ribbed with stronger ribs around the umbilicus forming a pseudo-keel (Fig. 8D). There are about 22 growth lines on the penultimate whorl (aperture front view), i.e. 10 growth lines/mm, and about 32 on the last part of the body whorl, i.e. 13 growth lines/mm (aperture side view). The last part of the body whorl is detached from the penultimate whorl. The last whorl just above the aperture present has a slight, inconspicuous central groove in its upper part (Fig. 8D-E). The aperture is rounded and slightly inclined to the columellar axis (Fig. 8E) and reaches up to 1.9 mm in high, and 1.9 mm in diameter. The outer and inner peristome are distinct, separated by about 0.5 mm; outer peristome thinner, slightly reflected, its parietal part touching the penultimate whorl (Fig. 8E); inner peristome thicker and more reflected, (Fig. 8E); umbilicus narrow.

**Remarks.** This new specimen appears to be both more cylindrical and more corpulent than the other six published specimens of *Cretadiostoma caperatum* (see Yu et al., 2023), but the last whorls are here also clearly narrower towards the aperture according to the species diagnostic characters. The aperture appears to be less, but distinctly, detached from the penultimate whorl, with the inner and outer peristomes closer together. This divergent aperture morphology is either due to an intra-specific polymorphism or possibly a sub-adult individual but is in accordance with the original description of the species.

**Discussion**

To date, 38 species of molluscs have been described from Burmese amber, including 32 species of land snails and the two diplommatinid species described in this article (*Euthema convexispira* sp.
nov. and *Euthema torokzselenszkyi* sp. nov.). Of the Cyclophoridea, Pupinidae and Diplommatinidae are currently documented as the most diverse families, *with respectively* 11 and 12 species. The former comprises seven genera, while the latter comprises only two.

Although 80% of mollusc species from Burmese amber (31 out of 37 species) were described between 2019 and 2021, fewer new terrestrial snail species have been described in more recent years (Ross, 2024, 2025). However, given the short observation period involved and the very limited number of specialists currently working on Burmese amber land snails, such temporal fluctuations in description rates must be interpreted with caution and do not allow any inference regarding the completeness of species sampling or the underlying diversity.

On the contrary, there is still considerable potential for the discovery of additional terrestrial gastropod taxa. Molluscs are estimated to occur at a rate of approximately one specimen per 500 inclusions in Burmese amber, and at least 200 amber pieces containing gastropods have been reported from private collections (Balashov, 2021a), whereas current knowledge is based on only a limited number of specimens from public collections. These observations strongly suggest that the known fossil record of land snails from Burmese amber remains heavily under sampled.

The new specimens published here suggest that continued exploration of Burmese amber is likely to reveal both new species and additional material of already described taxa. In the former case, new species may exhibit novel morphological traits, such as the putative inner lamella observed in the diplommatinid species described herein. It is unclear whether this structure is homologous to the columellar lamellae observed in other Diplommatinidae, and this will require additional material for confirmation. In the latter case, new specimens of known species may provide valuable complementary morphological information. An example of this is the exceptionally well-preserved multispiral operculum documented here for the cyclophorid *Hirsuticyclus canaliculatus* Yu, 2022.

Such opercular characters are of particular interest, as they play an important role in generic diagnoses within the family Cyclophoridae.

We emphasise the importance of computed tomography imaging for species descriptions, particularly for minute shells. In addition to three-dimensional reconstruction, this technique allows access to internal characters that are otherwise inaccessible, providing crucial data for taxonomic assessments and for improving our understanding of the evolutionary history of terrestrial gastropods preserved in Burmese amber.

## Acknowledgements

The authors thank the MorphOptics domain of the GISMO technological platform (Biogéosciences lab, Université Bourgogne Europe, CNRS, UMR 6282, 21000 Dijon, France), and in particular
Lauriane Poloni, Jérôme Thomas and Emmanuel Fara for their great help with photographs and CT-scans. This work was supported by infrastructures and equipments acquired through the VirtuNat project funded by the "Contrat de projets État-Région" (CPER) 2021-2027 and through the e-Col+ project (Equipex+) funded by the "Programme d'Investissements d'Avenir – France 2030" (ANR 21 ESRE 0053).
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**Legend of the figures**

**Fig. 1.** New material of *Hirsuticyclus canaliculatus* Yu, 2022 from the mid-Cretaceous Burmese amber (MHNE.2024.06.03). **A**, amber piece with the embedded shell (apical view); **B**, apical view of the shell showing the apex and spiral keels; **C**, close-up of square C in B showing the protoconch; **D**, amber piece with the embedded shell (umbilical view); **E**, umbilical view of the shell showing umbilicus and operculum; **F**, close-up of square F in B showing the upper surface of the aperture with growth lines and spiral keels; **G**, close-up of the square G in E showing umbilicus, operculum, basal channel (dotted white lines) and periumbilical keel; **H**, Close-up of the square H in E showing operculum, indented and acuminate edge of lamellae and nucleus. **bc** – basal channel; **ed** – acuminate edge; **gl** – growth lines; **la** – lamellae; **nu** – nucleus; **op** – operculum; **pk** – periumbilical keel; **sp** – spiral keels; **um** – umbilicus. Scale bars: 3 mm (A, D), 2 mm (B, E), 1 mm (C, F, G), 250 µm (H).

**Fig. 2.** New material of *Hirsuticyclus canaliculatus* Yu, 2022 from the mid-Cretaceous Burmese amber (MHNE.2024.06.03), 3D shell reconstruction. **A**, umbilicus; **B**, peristome; **C**, subapical view of the shell. Scale bar: 2 mm.

**Fig. 3.** Shell of *Euthema* cf. *annae* Balashov, 2021 from the mid-Cretaceous Burmese amber (MHNE.2024.06.01). **A**, amber piece with the embedded shell; **B**, lateral view of the shell showing the umbilicus; **C**, lateral view of the shell showing the free edge of the peristome; **D**, lateral view of the shell with close up of the last whorl, the arrow indicates the narrowing just behind the aperture. Scale bars: 3 mm (A), 250 µm (B, C), 150 µm (D).

**Fig. 4.** Holotype of *Euthema convexispira* Bichain et Páll-Gergely, sp. nov. from the mid-Cretaceous Burmese amber (MHNE.2024.06.05). **A**, amber piece with the embedded shell (apertural view); **B**, apertural view of the shell, the arrow indicates possible presence of soft parts of the animal in the first whorls; **C**, view of the aperture and the last whorl (white arrows indicate inner peristome); **D**, amber piece with the embedded shell (abapertural view); **E**, abapertural view of the shell; **F**, abapertural view of the last and penultimate whorl; **G**, 3D shell reconstruction. Scale bars: 2.5 mm (A, D), 250 µm (B, E, G), 150 µm (C, F).

**Fig. 5.** Holotype of *Euthema torokzselenszkyi* Páll-Gergely et Szabó, sp. nov. from the mid-Cretaceous Burmese amber (HNHM PAL 2025.24.1.). **A**, amber piece with the embedded shell
(apertural view); **B–C**, photographs of the shell; **D–M**: microphotography views; **D–I**, standard views of the shell; **J**, aperture of the holotype; **K–M**, inner lamella. Red arrow indicates the ending of the lamella, white arrow indicates the lamella itself. Scale bars: 2.5 mm (A), 500 µm (B, C), 1 mm (D–H), 250 µm (J–M).

**Fig. 6.** Shell of *Euthema* sp. from the mid-Cretaceous Burmese amber (MHNE.2024.06.04). **A**, amber piece with the embedded shell (apertural view); **B**, apertural view of the shell; **C**, close up of the aperture and the last whorl; **D**, amber piece with the embedded shell (abapertural view); **E**, abapertural view of the shell; **F**, Close up of the dorsal side of the last whorl. Scale bars: 2.5 mm (A, D), 250 µm (B, E), 100 µm (C, F).

**Fig. 7.** Shell of *Pulchraspira* sp. from the mid-Cretaceous Burmese amber (HNHM PAL 2024.25.1.). **A–B**, embedded shell in the amber piece. Scale bar: 500 µm (A, B),

**Fig. 8.** New material of *Cretadiostoma caperatum* Yu, Zhuo & Páll-Gergely, 2023 from the mid-Cretaceous Burmese amber (MHNE.2024.06.02). **A**, amber piece with the embedded shell (subapertural and lateral views left and right respectively); **B**, apical view of the shell; **C**, lateral view of the shell showing the free edge of the aperture; **D**, close up of the aperture showing the double peristome; **E**, close up of the lateral view of last whorl showing the outer and the inner peristome; **F**, close up of the protoconch; **E**, 3D shell reconstruction. *ipe* – inner peristome; *ope* – outer peristome. Scale bars: 4 mm (A), 1.2 mm (B, C, E), 500 µm (D, E), 200 µm (F).
<figure><img src="image_2.png" /><figcaption>Fig. 1</figcaption></figure>
<figure><img src="image_3.png" /><figcaption>Fig. 2</figcaption></figure>
<figure><img src="image_4.png" /><figcaption>Fig. 3</figcaption></figure>
<figure><img src="image_5.png" /><figcaption>Fig. 4</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>Fig. 5</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>Fig. 6</figcaption></figure>
<figure><img src="image_8.png" /><figcaption>Fig. 7</figcaption></figure>
<figure><img src="image_9.png" /><figcaption>Fig. 8</figcaption></figure>
<caption>**Table 1.** A comparison of distinguishing characters in genera *Euthema* and *Pulchraspira* modified after Balashov (2021b).</caption>

H – shell height; D – shell diameter; W – number of whorls; R – Ribs on the apertural half of penultimate whorl; C – Constriction; P – penultimate whorl coiling tightly; U – Umbilicus; PK – Periumbilical keel.

<table><thead><tr><th>Species</th><th>H</th><th>D</th><th>W</th><th>Whorl convexity</th><th>Aperture shape</th><th>R</th><th>C</th><th>P</th><th>U</th><th>PK</th></tr></thead><tbody><tr><td>Euthema annae</td><td>2</td><td>1</td><td>6</td><td>weak</td><td>almost heart-shaped</td><td>40</td><td>strong</td><td>yes</td><td>narrow</td><td>weak</td></tr><tr><td>Euthema dilatata (juvenile)</td><td>1.45</td><td>0.93</td><td>5</td><td>moderate</td><td>circular</td><td>30</td><td>moderate</td><td>yes</td><td>narrow</td><td>none</td></tr><tr><td>Euthema hesoana</td><td>2</td><td>1</td><td>5-6</td><td>?</td><td>oval</td><td>20</td><td>strong</td><td>yes</td><td>wide</td><td>very strong</td></tr><tr><td>Euthema lophopleura</td><td>2.25</td><td>1.25</td><td>6.5</td><td>strong</td><td>oval, oblique</td><td>20</td><td>moderate</td><td>yes?</td><td>narrow</td><td>none or weak</td></tr><tr><td>Euthema myanmarica</td><td>2</td><td>0.9</td><td>6</td><td>moderate</td><td>oval</td><td>25</td><td>weak</td><td>no</td><td>wide</td><td>strong</td></tr><tr><td>Euthema naggsi</td><td>2.1</td><td>1.1</td><td>6</td><td>strong</td><td>oval</td><td>28</td><td>moderate</td><td>yes</td><td>narrow</td><td>none</td></tr><tr><td>Euthema truncatellina</td><td>1.7</td><td>0.9</td><td>6.5</td><td>moderate</td><td>circular</td><td>35</td><td>weak</td><td>no</td><td>narrow</td><td>none</td></tr><tr><td>Euthema spelomphalos</td><td>3.25</td><td>1.5</td><td>6-7</td><td>weak</td><td>oval</td><td>20</td><td>weak</td><td>no?</td><td>wide</td><td>weak</td></tr><tr><td>Euthema convexispira sp. nov.</td><td>1.86</td><td>1.0</td><td>6.5</td><td>strong</td><td>circular</td><td>35-40</td><td>weak</td><td>no</td><td>wide</td><td>none</td></tr><tr><td>Euthema cf. annae (additional material)</td><td>2</td><td>0.75</td><td>6</td><td>moderate</td><td>almost heart-shaped</td><td>30</td><td>strong</td><td>yes</td><td>wide</td><td>None or weak</td></tr><tr><td>Euthema torokzselenszkyi sp. nov.</td><td>2.14</td><td>1.04</td><td>6</td><td>strong</td><td>sub-circular with a denticule</td><td>40</td><td>weak</td><td>no</td><td>wide</td><td>blunt</td></tr><tr><td>Pulchraspira teneristoma</td><td>3-3.9</td><td>1.1-1.9</td><td>5-6</td><td>strong</td><td>Circular with large, expanded peristome</td><td>~20</td><td>yes</td><td>?</td><td>narrow</td><td>none</td></tr></tbody></table>