Based on a single well-preserved specimen from Eocene Baltic amber, Lilioceris groehni sp. n. is described and illustrated using phase-contrast X-ray microtomography. It is the first described species of Criocerinae (Coleoptera: Chrysomelidae) from Baltic amber. A check-list of fossil Criocerinae is provided. Placement of Crioceris pristiana (Germar, 1813) is discussed, this species is removed from Criocerinae and placed in Coleopteraincertae sedis.

Taxonomy, palaeontology, shining leaf beetles, new species, Crioceris pristiana , fossil resin, Tertiary, Eocene

The subfamily Criocerinae (shining leaf beetles) contains ca. 1500 extant species (Schmitt 1996) in 20 genera (Seeno and Wilcox 1982), of which 211 species in 6 genera are recorded from the Palaearctic region (Schmitt 2010). The genus Lilioceris Reitter, 1913 comprises ca. 170 extant species distributed over the temperate, subtropical and tropical regions of the Palaearctis, Orientalis, Aethiopis including Madagascar, and the Australis, and was introduced to North America by man (Monrós 1960, plus records from the Zoological Record up to present as taken from the Index to Organism Names).

Shining leaf beetles are rarely represented in fossil material and especially in Baltic amber (Table 1). Two fossil species from Baltic amber were mistakenly described within Criocerinae. Electrolema baltica Schaufuss, 1892 was described as member of Criocerinae but later transferred to Hispinae (Korschefsky 1939). According to modern classification (Staines 2012), it is placed in Gonophorini Chapuis, 1875 within Cassidinae. Another species, Crioceris pristina (Germar, 1813) originally described as Criocerina (Germar 1813) was mentioned within Criocerinae (e.g. Giebel 1856a, 1856b; Spahr 1981; Santiago-Blay 1994). In our opinion it is not a member of the Criocerinae (see Discussion).

Crioceris sp. and Lema sp. were mentioned from Eocene Baltic amber without detailed species descriptions (Hope 1836; Giebel 1856; Menge 1856; Scudder 1885, 1886, 1891; Handlirsch 1908; Klebs 1910; Bachofen-Echt 1949; Larsson 1978; Spahr 1981; Santiago-Blay 1994; Poinar 1999). In the current paper, the first extinct species of Criocerinae from Baltic amber is described, figured, and compared with extant species using phase-contrast X-ray microtomography.

The specimen is included in an amber piece that was polished by hand and facetted on their sides, allowing improved views of the included specimens. The material examined is deposited in the collection of the Geological-Palaeontological Institute of the University of Hamburg, Germany [GPIH], as part of the collection of Carsten Gröhn.

Observations were made using a Nikon SMZ 745T stereomicroscope. Photographs were taken using a Canon EOS 70D with a 100 mm macro lens, and a Canon EOS 5D with the Canon MP E 65 mm macro lens in a visionary digital bk plus lab system by Dun Inc. The microCT-images were produced by means of an Xradia Micro XCT-200 (Carl Zeiss X-ray Microscopy Inc.), using the 4x object lens units, at 30kV and 4W, with a pixel size of 5.36 µm. Tomography projections were reconstructed using the reconstruction software provided by XRadia. Volume rendering of image stacks was performed by using Amira 5.6.0 (FEI Visualization Science Group, Burlington, USA) using the “Volren” or “Voltex” function.

The specimen of Lilioceris groehni sp. n. appears externally complete. However, the fact that we found no traces of internal structures in the abdomen, especially of an aedeagus, does most probably mean that (1) the specimen was a female, and (2) that it remained openly accessible for scavengers and/or detritivores before it was covered by resin. This could also provide a possible reason for its black appearance as the dead individual might have been exposed to humic acids before being fossilised. If this should be the case, the live animal had most probably a habitus similar to the extant lily beetles. Actually, L. groehni sp. n. is hardly distinguishable from extant Lilioceris-species. In this respect, the new species is quite normal. Hennig (1966) wrote that it is „a long known fact” [„eine altbekannte Tatsache”] that the morphological differences between fossils from Baltic amber and their extant relatives are only minute”.

Santiago-Blay (1994) mistakenly listed two fossil species as members of Criocerinae: Lema pervetusta Cockerell, 1921 and Lema pulchella Förster, 1891. Lema pervetusta was described from Bridgerian lacustrine shale (Eocene, 50.3–48.6 Ma) of the Green River Formation of Colorado, USA (Cockerell 1921), but according to Linsley (1942) this species belongs to the longhorn beetle genus Clytus Laicharting, 1784 (Cerambycidae). Lema pulchella was described from Oligocene lacustrine (33.9–28.4 Ma) of Riedisheim, Mulhouse, France (Förster 1891), but according to Théobald (1937) it belongs to the weevil genus Phyllobius Germar, 1824 (Curculionidae).

Few Quaternary sub-fossil records contain specimens of the extant species: Lema cyanella (Linnaeus, 1758) from La Taphanel, Massif Central, France (Ponel and Coope 1990); Lema trilinea White, 1981 from late Quaternary Kaetan Cave, Colorado Plateau, Colorado, USA (Elias and Van Devender 1992); and Oulema obscura (Stephens, 1831) from the Holocene of Belarus (Nazarov 1984). These records are not mentioned in the current list (Table 1). None of the records of “Criocerinae”, “Crioceris sp.”, or “Lema sp:” from Baltic amber listed in Table 1 can be assigned to a certain species of shining leaf beetles.

Germar (1813) described Criocerina pristina from Baltic amber. Later this species was mentioned as Crioceris pristina (Germar, 1813) within Criocerinae (e.g. Giebel 1856a, 1856b; Spahr 1981; Santiago-Blay 1994). The correct subfamily and family placement of Crioceris pristina is doubtful in our opinion. According to the original description (Germar 1813: 14), this fossil species has antennae with a club (similar as in members of the genus Anobium) ["... Die Fühler von etwas mehr als halber Körperlänge, roth, and der Spitze dunkler, das erste Glied kurz und dick, vor den Augen auf der Stirn eingesezt, das folgende Glied klein, kugelförmig, die nun folgenden sechs Glieder sehr klein und dicht zusammengedrängt, dass sie als blosse Ringe erscheinen, die drey lezten Glieder lang und dicker, fast wie beyAnobiumgebaut, sie machen zusammen zwei Drittheil der ganzen Fühlerlänge aus ..."]. In addition, Germar gave the length of this specimen as 1¹/₈ lines = 2.54 mm. This would be an extremely low value for a species of Lilioceris. All extant species are described as being longer than 5 mm. Germar mentioned that his Criocerina pristina resembled „Crioceris testacea Fabr.”, of which he said it were six times larger – i.e. ca. 1.5 cm. The species Fabricius described as Crioceris testacea (Fabricius 1787: 87/88) is currently listed under Aulacophora indica (Gmelin, 1790), Galerucinae (Mohamedsaid 2009), and its lectotype is depicted in Lee and Beenen (2015, Figs 42 & 43). We conclude that „Crioceris pristina” is actually not a criocerine beetle nor a member of the family Chrysomelidae. Instead, we suggest that it should be better placed as Coleopteraincertae sedis. This conclusion leaves Lilioceris groehni sp. n. as the first beetle species from Baltic amber that we can classify with certainty as a member of the ColeopteraChrysomelidaeCriocerinae.

The authors are grateful to Carsten Gröhn (Glinde, Germany) for the loan of interesting fossil material, to Vitalii I. Alekseev (Kaliningrad, Russia) for valuable suggestions and constructive advice, to Peter Michalik (Greifswald, Germany) for invaluable help with macro-imaging and the microCT-analysis, and the German Science Foundation (DFG) for financial support (INST 292/119-1 FUGG, INST 292/120-1 FUGG).