Zootaxa, Fossil Carabids from Baltic Amber

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Fossil carabids from Baltic amber – I – A new species of the genus Calathus Bonelli, 1810 (Coleoptera: Carabidae: Pterostichinae)

VICENTE M. ORTUÑO1,3 & ANTONIO ARILLO2 1Departamento de Zoología y Antropología Física. Facultad de Biología. Universidad de Alcalá. E-28871 Alcalá de Henares. Madrid. Spain 2Departamento de Zoología y Antropología Física. Facultad de Biología. Universidad Complutense. E-28040 Madrid. Spain 3Corresponding autor. E-mail: [email protected]

Abstract

In this paper a new species of fossil ground-beetle, Calathus elpis n. sp. (Coleoptera, Carabidae) preserved in a piece of Baltic amber (Eocene) is described. A comparison with extant fauna is made, and paleobiology of the species is studied.

Key words: Arthropoda, Hexapoda, taxonomy, palaeoentomology

Introduction

Carabids (ground beetles) probably originated in the Mesozic. Oldest fossils have appeared in the Triassic of Virginia (USA) (Grimaldi & Engel 2005). At present they are widely distributed being present in all continents but Antarctica. The family Carabidae is a speciose group with more than 34000 described species (Lorenz 2005). Although amber carabid fossils are known from the Tertiary only a small number of species have been described, three of them from Baltic amber: Yablokov-Khnzoryan (1960) described Dyschiriomimus stackelbergi (Scaritinae), Abdullah (1969) described Dromius bakeri (Lebiinae) and Erwin (1971) described Tarsitachys bilobus (Trechinae). There are some other descriptions in classic literature (XIX century) but they must be regarded with caution as they were never redescribed and type material is lost; for a complete list see Larsson (1978). Oldest lineages of carabids seem to be tropical (Erwin 1985). However, in the Cenozoic, modern lineages appeared and produced most of present diversity. The specimen studied in this paper belongs to this modern radiation. Several tribes are included in the subfamily Platyninae. One of them, Sphodrini, has a Holarctic distribution (Jeannel 1942). Its diagnosis is mainly based on genitalic features to separate it from related tribes (Lindroth 1956; Casale 1988; Machado 1992). However its systematics is controversial and some authors consider it as a tribe while others prefer to consider it as a subtribe. In this paper we follow Hovorka & Sciaky (2003) who consider it as a tribe divided in six subtribes, being Calathina the most widely distributed (Casale 1988: 933). Calathina includes the genus Calathus Bonelli, 1810 with 129 Palearctic species (Hovorka & Sciaky 2003) and 22 Nearctic species (20 endemic and 2 introduced) (Ball & Nègre, 1972). Its distribution is mainly Holarctic but some species have invaded Ethiopic and Oriental regions (Schatzmayr 1937).

Accepted by J. Serrano: 1 Sept. 2009; published: 24 Sept. 2009 55 TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited.

Results

Order Coleoptera Linnaeus, 1758

Suborder Adephaga Clairville 1806

Family Carabidae Latreille, 1802

Subfamily Platyninae Bonelli, 1810

Tribe Sphodrini Laporte, 1834

Subtribe Calathina Laporte, 1834

Calathus Bonelli, 1810

Calathus elpis n. sp. (Figs. 1–3)

Description. Holotype: 1 female preserved in a piece of Baltic amber (16 mm x 5 mm / diameter x width) (Eocene) deposited in the Álava Museum of Natural Sciences (Vitoria, Spain) MCNA-13638 (the genitalia and other soft tissues are not preserved but the specimen is a female as protarsi are not swollen). Length (from head to elytra apex): 7.5 mm. Color brown-reddish (Fig. 1b and 1c). Disk of elytron depigmented at its posterior part (probably due to taphonomic processes) (Fig. 1b and 1d). Head (Fig. 1b, 1c, 1d, and 3a): Large and convex compound eyes. Long and oblique tempora. Two supraocular setae, being the posterior one at the level of posterior edge of eyes. Two setae on the clypeus. Rectangular labrum with six antero-marginal setae. Mandibles without setae on the lateral sulcus. Slender antennae with eleven antennomeres, pubescent from 4th to 11th (the 4th one lacking pubescence in its basal third part). Antennomeres bearing a crown of distal setae except the first one (with only one long seta) and the second one (shorter than the rest and without setae). Mentum tooth not visible. Maxillary and labial palps typical of Calathus. Pronotum (Fig. 1b and 1d) quadrangular, not transverse. Anterior margin slightly concave, being its anterior angles protuding but round shaped. Basal margin straight. Lateral margins curved, with its maximum width at the level of the anterior marginal setae. Posterior angles obtuse and blunt. Lateral channel barely evident being wider at its base. Basal fossae not very deep. Prosternum (Fig. 1c and 2a) with acuminate linguiform intercoxal apophysis. Intercoxal apophysis of mesosternum (Fig. 1c and 2c) W-shaped, that of metasternum (Fig. 1c and 2d) subtriangular. Long metaepisternum (Fig. 2b). All thoracic esternal pieces with smooth tegument. Elytra (Fig. 1b and 1d) lateral margins are subparallel, sharped towards the apex. Epipleura not crossed. Rounded shoulders, without humeral teeth. All the striae are visible, from the base to the apex. Striae from 1st to 7th clearly stippled, 8th one sulciform. Lateral umbilicate serie (Fig. 1d) is continuous, with 15 setigerous pores over the 8th striae. Interstriae flat and with micropunctures. Discal setae (Fig. 1d) barely visible due to the presence of a whitish veil partially covering the dorsum of the specimen; one seta visible in the third interval, adjacent to striae 2, two setae adjacent to striae 5 and one seta close to the apex, over the 7th striae. One apical seta is preserved over the right elytrum. Both elytra are not equal in length (Fig. 1d) so striae 1st to 4th make up different anastomosis on each elytrum: setae 1–4, 2–3 on the left elytrum and setae 1–2, 3–4 on the right elytrum. This kind of light malformations are quite frequent on recent carabidofauna. Wings well developed.

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FIGURE 1. Calathus elpis n. sp. Photographs: a. piece of amber; b. dorsal view; c. ventral view. Drawing: d. specimen in dorsal view (scale: 2 mm).

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FIGURE 2. Calathus elpis n. sp. camera lucida drawings. a. prosternal coxae; b. metaepisternum; c. mesosternal coxae; d. metasternal coxae. (scale: 0.5 mm).

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FIGURE 3. Calathus elpis n. sp. camera lucida drawings. a. right antennomeres; b. right prothoracic tibia and tarsus; c. right mesothoracic tibia and tarsus; d. right metathoracic tarsus; e. onychium in ventral view. (scale: 0.5 mm).

Legs moderately long and gracile (Fig. 1b, 1c and 1d). Spherical prothoracic (Fig. 1d and 2a), conical mesothoracic (Fig. 1d and 2c) and transverse metathoracic (aliform) coxae (Fig. 1d and 2d). Protibial cleaner organ with internal notch and two guide setae (Fig. 3b). Mesotibial cleaner organ (Fig. 3c) similar to comb model (sensu Ortuño 1988). Tarsi smooth, long and dorsally glabrous (Fig. 3b, 3c and 3d); onychium ventrally setose with tarsal claws pectinate (Fig. 3b, 3c and 3e). Etymology: Specific epithet is after Elpis (<λπίς), who was in the Greek mythology the personification of hope that remained in the Pandora’s box to help people to bear the misfortunes. Elpis (Esperanza in Spanish) is after our colleague, the anthropologist Dra. Esperanza Gutiérrez Redomero. State of preservation. Although the specimen is slightly damaged, the state of preservation is quite good, so morphological and taxonomic studies are possible. Most of soft tissues are digested, being the tegument

A FOSSIL CALATHUS FROM BALTIC AMBER Zootaxa 2239 © 2009 Magnolia Press · 59 TERMS OF USE This pdf is provided by Magnolia Press for private/research use. Commercial sale or deposition in a public library or website is prohibited. quite transparent. Dorsal side of the fossil is partially covered by a withish coat (Fig. 1b and 1d) but most of diagnostic characters of the genus are visible. Abdominal sternites are partially destroyed (Fig. 1c) allowing to observe the folded wings under the elytra. Left prothoracic leg is not complete; only the coxa, the trochanter and the base of the femur are preserved (Fig. 1c). Left mesothoracic leg has lost the tarsi and most part of the tibia (Fig. 1b, 1c and 1d). Right metathoracic leg has lost the tarsi (Fig. 1c). Left antenna is incomplete, only preserved up to the 4th antennomere (Fig. 1b, 1c and 1d).

Discussion

Following Casale (1988) this specimen belongs to the tribe Sphodrini according to the pectinate claws. There is not a wide consensus about the systematics of the genus Calathus probably because the plasticity of the genus (Lindroth 1956; Ball & Nègre 1972), what makes quite difficult the diagnosis of the different evolutionary lineages (Machado 1992). The division of the genus into subgenera is, in our point a view, largely based on subjective criteria rather than on accurate data (see Ruiz & Serrano 2006). These subgenera are thus of poor utility to place fossils and for this reason we preferred not to assign the new species to an extant or new subgenera. Calathus elpis n. sp. shows the classic morphology of a poorly modified Calathus, being most of its features plesiomorphic. For example, metepisternae are long denoting well developed wings, an ancestral feature of Sphodrini and related tribes. Due to its morphology and the small size, C. elpis n. sp. could be an ancestor of the “C. mollis group”, although setation formula of the elytral disk is different in the fossil. Migration of setae from the 3rd interstriae towards the 2nd striae is a feature present in Calathus circumseptus Germar, 1824 but C. elpis n. sp. has developed setae close to the 5th striae, that absent in C. circumseptus. The presence of setae in more than one stria (or interstria) on each elytrum is a common feature among species of the subgenus Calathus s.str. The macropterous C. elpis n. sp. possibly lived in both open and forested habitats as shown by extant species of the subgenus Neocalathus, which are mainly dimorphic and have a wide distribution area. Some Calathus taxa climb occasionally over trees and shrubs and show a gregarious behaviour during winter so they can be considered occasional inhabitants of the subcorticicolous environment (Machado 1992; Larochelle & Larivière 2003). However no Calathus can be strictly considered as a corticicolous species and thus the presence of C. elpis n. sp. in Baltic amber does not necessarily indicate its preference for forested habitats.

Aknowledgements

This study is a contribution of the project CGL2008-00550/BTE: "The Cretaceous amber of Spain: a multidisciplinary study" of the Spanish Ministry of Science and Innovation.

References

Abdullah, M. (1969) Dromius bakeri, a new species of the Lebiini from the Klebs collection of the Baltic amber (Coleoptera, Carabidae) Deutsche Entomologische Zeitschrift, 16, 399–403. Ball, G.E. & Nègre, J. (1972) The taxonomy of the Nearctic species of the genus Calathus Bonelli (Coleoptera: Carabidae: Agonini). Transactions of the American Entomological Society, 98, 412–533. Casale, A. (1988) Revisione degli Sphodrina (Coleoptera, Carabidae, Sphodrini). Monografie 5. Museo Regionale di Scienze Naturali, Torino, 1024 pp. Erwin, T.L. (1971) Fossil Tachyne beetles from Mexican and Baltic amber with notes on a new synonymy of an extant group (Coleoptera, Carabidae). Entomologica Scandinavica, 2, 233–236.

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Erwin, T.L. (1985) The taxon pulse: a general pattern of lineage radiation and extinction among carabid beetles. In: Ball, G. E. (Ed.), Taxonomy, phylogeny and zoogeography of beetles and ants. W. Junk, Dordrecht, pp. 437–472. Grimaldi, D.A. & Engel, M.S. (2005) Evolution of the Insects. Cambridge University Press, New York, 755 pp. Hovorka, O. & Sciaky, R. (2003) Carabidae: Harpalinae: Sphodrini: Calathina. In: Löbl, I. & Smetana, A. (Eds.), Catalogue of Palaearctic Coleoptera, Vol. 1., Apollo Books, Stenstrup, pp. 524–529. Jeannel, R. (1942) Coléoptères Carabiques (deuxiéme partie). Faune de France, 40. Lechevalier, Paris, pp. 573–1173. Larochelle, A. & Larivière, M.C. (2003) A Natural History of the Ground–Beetles (Coleoptera: Carabidae) of America north of Mexico. Pensoft Publishers, Sofia, 583 pp. Larsson, S.G. (1978) Baltic amber – a paleobiological study. In: Lyneborg, L. (Ed.), Entomonograph Vol. 1., Scandinavian Science Press Ltd., Klampenborg, 192 pp. Lindroth, C. (1956) A revision of the genus Synuchus Gyllenhal (Coleoptera: Carabidae) in the widest sense, with notes on Pristosia Motschulsky (Eucalathus Bates) and Calathus Bonelli. Transactions of the Royal Entomology Society of London, 108, 485–576. Lorenz, W. (2005) A Systematic List of Extant Ground Beetles of the World (Coleoptera "Geadephaga": Trachypachidae and Carabidae, incl. Paussinae, Cicindelinae, Rhysodinae). Second edition, Edited by author, Tutzing, 528 pp. Machado, A. (1992) Monografía de los carábidos de las islas Canarias (Insecta, Coleoptera). Instituto de Estudios Canarios, La Laguna, 734 pp. Ortuño, V.M. (1988) Importancia de los caracteres tibiales en la sistemática de Harpalidae (Col. Caraboidea). Actas del III Congreso Ibérico de Entomología, Granada, pp. 263–270. Ruiz, C. & Serrano, J. (2006) Molecular phylogeny and systematics of Calathus Bonelli (Coleoptera: Carabidae: Sphodrini) based on mitochondrial cox1–cox2 sequences. Entomologica Fennica, 17, 214–220. Schatzmayr, A. (1937) I Calathus d’Europa. Pubblicazioni del Museo Entomologico “Pietro Rossi”, Udine, 2, 1–50. Yablokov-Khnzoryan, S.M. (1960) New Coleoptera from Baltic amber. Paleontologicheskii zhurnal, 1960(3), 90–101. [In Russian]