Burmapseudomorphus planus gen. et sp. nov. – a Late Cretaceous stem group member of the specialized Pseudomorphini (Carabidae, Coleoptera) from northern Myanmar

Journal Pre-proof Burmapseudomorphus planus gen. et sp. nov. – a Late Cretaceous stem group member of the specialized Pseudomorphini (Carabidae, Coleoptera) from northern Myanmar Rolf Georg Beutel, Zhenhua Liu, Martin Fikáček, Dong Ren, Hong Pang, Adam Ślipiński PII:

S0195-6671(19)30258-7

DOI:

https://doi.org/10.1016/j.cretres.2019.104274

Reference:

YCRES 104274

To appear in:

Cretaceous Research

Received Date: 18 June 2019 Revised Date:

10 October 2019

Accepted Date: 11 October 2019

Please cite this article as: Beutel, R.G., Liu, Z., Fikáček, M., Ren, D., Pang, H., Ślipiński, A., Burmapseudomorphus planus gen. et sp. nov. – a Late Cretaceous stem group member of the specialized Pseudomorphini (Carabidae, Coleoptera) from northern Myanmar, Cretaceous Research, https://doi.org/10.1016/j.cretres.2019.104274. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.

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Burmapseudomorphus planus gen. et sp. nov. – a Late

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Cretaceous stem group member of the specialized

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Pseudomorphini (Carabidae, Coleoptera) from northern

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Myanmar

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Rolf Georg Beutela*, Zhenhua Liub, c, Martin Fikáčekd, Dong Rene, Hong

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Pangb and Adam Ślipińskic

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a

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Jena, Germany, [email protected]

Institut für Zoologie und Evolutionsforschung, Friedrich-Schiller-Universität Jena, 07743

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b

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Yat-sen University, Guangzhou 510275, China

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c

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d

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of Science, Charles University, Viničná 7, CZ-12844 Praha 2, Czech Republic

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e

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Beijing 100048, China

State Key Laboratory of Biocontrol / The Museum of Biology, School of Life Sciences, Sun

CSIRO Canberra, Australia National Museum, Cirkusová 1740, CZ-19100 Praha 9 and Department of Zoology, Faculty

College of Life Sciences, Capital Normal University, Xisanhuanbeilu 105, Haidian District,

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ABSTRACT

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A new adephagan beetle embedded in Burmese amber from northern Myanmar is

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described as Burmapseudomorphus planus gen. et sp. nov. From its broad and flat 1

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habitus, the lack of a pronoto-elytral angle, the short and broad head, the short

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mesoventrite, and the lancet-shaped elongate prosternal process it resembles beetles

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belonging to the aquatic Dytiscoidea. The metacoxal plates are similar to those of

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Noteridae. However, pubescent antennal flagellomeres, an anisochaetous protibial

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antenna cleaner, transversely oriented metepimera, and metacoxae not reaching beyond

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the lateral margin of the metaventrite identify the fossil as an atypical species of

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Carabidae. Externally closed procoxal cavities, lacking of procoxal rests of the

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mesoventrite, a narrow mesepimeron which not reaching the mesocoxal cavity, and

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lobate metepimera indicate a placement in a clade comprising Harpalinae and

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Brachininae. This is supported by analyses of morphological data and a Hennigian

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character evaluation. The short and transverse head, the streamlined body without

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pronoto-elytral angle, and the secondarily elongated prosternal process suggest a

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placement as stem group member of the specialized Pseudomorphini. In contrast to

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species of the crown group of this lineage, a distinct submento-mental suture is present,

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ventral cephalic antennal grooves are missing, and the elytra are not truncated

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posteriorly. The fossil is the first record for Pseudomorphini and documents an origin

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of this specialized group of Carabidae at least dating back to the Cretaceous. A

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superficial similarity with the extant migadopine genus Stichonotus (e.g. broad and

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oval body, apically pointed prosternal process) is the result of convergence.

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1. Introduction

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The phylogenetic relationships of extant adephagan beetles have been largely clarified in

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recent years, with largely congruent results obtained with morphological (e.g. Beutel and

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Roughley 1988; Beutel, 1997; Beutel et al., 2006; 2013) and molecular data (e.g. Baca et al.,

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2017). In contrast to this, the status and placement of some fossil groups, for instance the

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Triassic Triaplidae or the Jurassic and Cretaceous Coptoclavidae (Ponomarenko, 1977) are

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still uncertain (e.g. Beutel et al., 2013; Ponomarenko and Prokin, 2015). In the present study 2

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we describe an unusual fossil from Cretaceous Burmese amber (Figs. 1, 2), clearly belonging

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to Adephaga but with a seemingly contradictory combination of characters, a mixture of

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features found in aquatic groups as for instance Aspidytidae (Ribera et al., 2002) or Noteridae

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(Belkaceme 1991), and in the terrestrial Carabidae (e.g. Beutel, 1992; Dressler and Beutel

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2010). External characters of the new fossil are scored and included in a comprehensive data

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matrix of Adephaga, mainly based on Beutel et al. (2006), but with a distinctly modified set

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of characters and sampling of ingroup and outgroup taxa. As a very broad taxon sampling in

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Carabidae would be beyond the scope of the present study, the systematic placement of the

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genus is also discussed based on an informal Hennigian approach (Hennig, 1950).

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2. Material and methods

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Material. The single specimen is embedded in Burmese amber, with fully visible dorsal and

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ventral side. The holotype is deposited at the Capital Normal University (CNU). The amber

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was collected from the Hukawng Valley of Kachin State, in northern Myanmar, at the

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northern end of Noije Bum, a village located approximately at N26°150′, E96°340′, 18 km

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southwest of the town of Tanai. The amber is dated as earliest Late Cretaceous (earliest

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Cenomanian), about 98.79 ± 0.62 Ma. This deposit has yielded many well-preserved insect

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fossils (e.g. Chen et al., 2019; Lin et al., 2019; Pohl et al., 2019).

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Additionally, dried specimens of different species of the pseudomorphine genus

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Sphallomorpha Westwood were examined at the Zoologische Staatssammlung München

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(ZSM). Two specimens of Sphallomorpha sp. preserved in ethanol were also dissected. The

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genus was chosen as it is placed as sister to the remaining Pseudomorphini and has preserved

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the maximum number of plesiomorphic features (Baehr, 1992, 1994, 1997). Additionally, a

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specimen of Stichonotus limbatus Sloane (Migadopini) was examined at the Australian

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National Insect Collection (ANIC) at CSIRO Canberra, and external features were

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documented with microphotography. 3

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Microphotography. The piece of amber was temporarily mounted on coverslips using

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glycerine. For overcoming the limited depth of field, stacks of several partially focused

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images were taken in raw format with a Canon EOS 6D digital SLR equipped with a Canon

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MP-E 65 mm macro lens (Canon, Krefeld, Germany) fitted with a StackShot macro rail

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(Cognisys, Traverse City, MI, U.S.A). The specimen was illuminated with two flashlights

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(Yongnuo Photographic Equipment, Shenzhen, China). Lens and the flashlights were

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equipped with polarization filters (cross-polarized light) to reduce reflections and enhance

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colour contrast. The raw images were processed in Adobe Photoshop Lightroom 6 (Adobe

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Systems Incorporated, San Jose, California, U.S.A) and saved as tif images. Zerene stacker

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1.04 (Zerene Systems LLC, Richland, U.S.A.) was used to fuse the images.

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Data set for phylogenetic placement. The character state matrix used to place

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Burmapseudomorphus is mainly based on a data set presented and analyzed in Beutel et al.

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(2006), but with a distinctly modified sampling of characters and ingroup and outgroup taxa.

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The number of aquatic genera was reduced (genera of Gyrinidae, Haliplidae and Noteridae)

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whereas more terminals of Carabidae were added (including for instance Metrius contractus

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Eschscholtz and Stichonotus limbatus), and also Heterogyrus and Batrachomatus as

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presumably basal representatives of Gyrinidae (excl. Spanglerogyrus) and Dytiscidae,

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respectively (e.g. Baca et al., 2017; Beutel et al., 2017, 2019). The data set comprises 84

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character of adults and 66 characters of immature stages, the latter scored as unknown (?) for

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Burmapseudomorphus. Three outgroup terminals were included, Cupedidae (Archostemata),

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Catops and Helophorus (Staphyliniformia, Polyphaga) and 41 ingroup taxa, 13 of them

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belonging to Geadephaga. Cupedidae was entered as chimera as adult characters are best

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documented for Priacma serrata (Baehr 1975; Hörnschemeyer et al., 2002) and larval

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characters for Rhipsideigma and Tenomerga (Beutel and Hörnschemeyer, 2002; Yavorskaya

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et al., 2015). This is justified as the family is doubtlessly monophyletic (e.g., Beutel et al.,

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2008; Hörnschemeyer, 2009). 4

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Drawings. The drawing was done with ink based on one of the microphotographs. Dotted

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lines indicate indistinctly visible structures.

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Phylogenetic analyses. The data were entered in a character state matrix with Winclada

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(Nixon 1999-2002). Parsimony analyses were carried out with NONA (ratchet, 1000

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replicates) (Goloboff, 1995) and TNT using traditional search (Goloboff et al., 2008). All

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characters had equal weight and were treated as unordered. The Bremer support values were

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calculated with NONA (Goloboff, 1995).

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3. Systematic palaeontology

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Order: Coleoptera Linnaeus, 1758

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Suborder: Adephaga Schellenberg, 1806

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Family: Carabidae Latreille, 1802

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Subfamily: Harpalinae Bonelli, 1810

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Burmapseudomorphus gen. nov., Beutel, Liu, Pang, Fikáček and Ślipiński

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(Figs. 1–2)

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Type species. Burmapseudomorphus planus sp. nov.

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Etymology. The genus name “Burmapseudomorphus” refers to the embedding in Burmese

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amber and the affinity to Pseudmorphini.

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Results of the phylogenetic analysis. The analysis with NONA yielded 6 minimum length

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threes with 408 steps (Ci: 0.54, Ri: 0.83). Seven trees with the same length were obtained

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with TNT. Geadephaga (branch support value [bs] 4) and Carabidae (bs 6) including

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†Burmapseudomorphus were confirmed as monophyletic. †Burmapseudomorphus was

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unambiguously placed as sister to the pseudomorphine genus Sphallomorpha (bs 2), in a

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clade also containing Bembidion Latreille (Trechinae), Pterostichus Bonelli (Harpalinae), and

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Brachinus Weber (Brachininae) (Fig. 3).

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Phylogenetic placement and diagnosis. The genus can be readily placed in Adephaga

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excluding Gyrinidae based on the following features: prosternal process long and projecting

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distinctly beyond procoxae posteriorly, mesoventrite relatively short and not flattened,

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metacoxae medially completely separating 1st visible abdominal sternite, with distinct coxal

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plates, genital appendages not exposed, sternite VII terminal. The dense pubescence on

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antennomeres 5-11, the protibial antenna cleaner, metacoxae not reaching the elytral epipleura

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laterally, and a nearly parallel-sided metepimeron nearly perpendicular to the longitudinal

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body axis are apomorphic features indicating a placement in Carabidae.

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†Burmapseudomorphus planus sp. nov., Beutel, Liu, Pang, Fikáček and Ślipiński

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(Figs 1–2)

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Material examined. Holotype. No. CNU-COL-MA_0142; lowermost Cenomanian, Hukawng

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Valley, northern Myanmar.

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Description. The description of the genus and species is combined. At present it is not

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possible to assess which characters are diagnostic on which taxonomic level.

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Body broad and flat, laterally strongly rounded, without pronoto-elytral angle (Fig. 1).

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Total length 4,63 mm; maximum width at anterior 1/3 of elytra 3,23 mm. Coloration black.

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Surface on dorsal and ventral side very shiny, lacking recognizable vestiture of hairs and

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microsculpture (Fig. 1).

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Exposed part of prognathous and transverse head extremely short, apparently deeply

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retracted into anterior prothorax (Fig. 1A). Well-developed compound eyes in almost

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transverse position, anteriorly directed, adjacent with anterolateral pronotal margin laterally;

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lateral edge of head between mesal margin of compound eye and clypeus short. Long anterior

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supraorbital setae of head capsule present; posterior supraorbital setae absent. Clypeus

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transverse, distinctly separated from frons. Posterodorsal head region with longitudinal

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wrinkles. Gular lines on ventral side distinct, converging in middle region and then diverging

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towards very broad submentum. Mid-gular apodeme not recognizable, probably missing.

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Ventral cephalic antennal groove absent (Figs 1, 2)

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Labrum exposed, transverse, with six long setae inserted close to slightly convex

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anterior margin; lateral setae longer than mesal ones. Anterolateral antennal insertion between

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posterolateral clypeal margin and anterior margin of compound eyes not visible from above

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(Fig. 1A). insertion area not visible from above. Antennae filiform, thin, distinctly reaching

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beyond posterior margin of pronotum posteriorly; composed of 11 segments; scapus wider

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than other segments, slightly curved; pedicellus about half as long as scapus and shorter than

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flagellomeres, with oblique distal edge; flagellomeres very slender, with sparse vestiture of

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medium length setae (ca. 0.03 mm); dense pubescent present on flagellomeres 5-11; apical

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antennomere spindle-shaped. Mandible scarcely protruding beyond anterior labral margin,

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with robust basal part and slender, mesally directed and apically pointed distal tooth. Scrobal

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seta not recognizable, very likely absent. Maxillary palps composed of four segments;

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palpomeres elongate and slightly wider than antennal flagellomeres; penultimate palpomere

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with very distinct white articulatory membrane at apical region; apical palpomere slightly 7

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wider and longer than other segments, spindle-shaped. Submentum not separated from gula,

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short and very broad, separated from mentum by distinct transverse suture. Mentum also

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broad, with two moderately convex lobes. Prementum not clearly visible. Three-segmented

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labial palps distinctly shorter than maxillary palps; basal palpomere very thin and curved;

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second segment long, slightly curved, widening distally; apical palpomere spindle-shaped,

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about as large as apical maxillary palpomere.

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Prothorax transverse, strongly rounded laterally, much wider posteriorly than

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anteriorly. Anterior pronotal corners almost adjacent with lateral margin of compound eyes,

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enclosing posterior head region; slightly convex anterior pronotal margin with thin bead;

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posterolateral pronotal edges distinctly protruding, with sharp apex; posterolateral margin

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fitting with elytral shoulder region. Posterolateral pronotal setae absent. Hypomeron broad,

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concave, distinctly widening posteriorly. Distinct but flat bead along lateral pronotal margin,

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slightly widening posteriorly. Exposed propleuron separated from prosternum by oblique

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slightly rounded suture. Anterior margin of prosternum nearly straight, with narrow bead.

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Prosternal process strongly developed, lancet-shaped, projecting far beyond hind margin of

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prothorax; pointed apical part almost reaches anteromedian process of metaventrite. Procoxal

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cavity round, externally closed, with mesally directed fairly narrow hypomeral process in

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contact with lateral process of proximal part of prosternal process, the latter with distinct

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punctures and a metallic sheen. Protrochantin not recognizable. Procoxae globular, very likely

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with ventral condyle articulating with dorsal surface of prosternal process. Protrochanter

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moderately sized, triangular, with narrow basal part and oblique articulation with femur.

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Profemur largest part of foreleg, appearing somewhat inflated in middle region; anterior edge

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distinctly convex, posterior edge nearly straight. Protibia almost as long as femur but less

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wide, nearly cylindrical, slightly widening distally; lateral edge with several spines;

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anisochaetous antenna cleaner present distad subapical pair of spines; apical part of tibia with

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mesal spur and several lateral spines. Protarsus five-segmented; with distinct spines;

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tarsomeres not dilated and without hairy soles; basal segment longest, subcylindrical, slightly

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widening distally; tarsomeres 2 and three short, narrow basally, distinctly widening distally;

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tarsomeres 4 and 5 short and very thin; paired claws equal.

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Mesothorax including elytral shoulder regions about as large as prothorax.

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Mesoventrite about as long as presternum, without paired procoxal rests; short and flat

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horizontal posteromedian part overlapped by apical part of anteromedian process of

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metaventrite; main part of mesoventrite steeply ascending above posterior part of prosternal

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process; hexagonal groove and anterior horizontal part of mesoventrite absent. Mesepimeron

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separated from mesocoxal cavity, ending at anterolateral edge of metaventrite; narrow

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mesally, slightly widening laterally. Mesotrochantinus not visible. Mesocoxae globular like

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procoxae, of similar size; mesally overlapped by flat posteromedian portion of mesoventrite,

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probably with ventral articulation. Mesotrochanter similar to protrochanter. Mesofemur

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longer than profemur and less widened in middle region. Mesotibia with very distinct spines

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ventrally and laterally, long paired apical spurs, and additional short apical spines. Mesotarsus

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longer than protarsus, with very slender tarsomeres 1-5; spines present on tarsomeres 1-4.

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Paired claws equal. Elytra complete, not truncated posteriorly; with shiny and concave

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epipleura, broad anteriorly and narrowing posteriorly, posteriorly reaching border between

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abdominal sternites VI and VII. Dorsal surface also shiny, without microsculpture; long seta

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inserted at shoulder region and at border between abdominal sternites III and IV close to

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lateral margin; seven very distinctly impressed longitudinal striae without punctures present;

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striae 1 and 2 and 5 and 6 confluent anteriorly; striae 2 and 7 end at posterior 1/3 of elytra, 4

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and 5 confluent posteriorly.

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Metathorax including metacoxae slightly shorter than ventrites of prothorax and

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mesothorax combined. Metaventrite not shortened, with semicircular anterior concavities

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forming part of mesocoxal cavities; distinct bead present anteriorly and laterally; middle

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portion distinctly raised but rounded in cross section, not forming flat platform; anteromedian

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process distinct, bordered by very distinct raised bead; slightly narrowing anteriorly, with

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almost truncate apex but anterolateral corners rounded; reaching beyond middle region of

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mesocoxae and overlapping with posteriormost part of mesoventrite. Median ridge 9

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(discrimen) absent on preepisternal anterior part of ventrite. Transverse ridge complete,

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slightly curved. Katepisternum completely divided by median ridge, strongly narrowing

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laterally. Metanepisternum large, roughly trapezoid, with distinct bead along anterior part of

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lateral edge; not reaching mesocoxal cavity. Metepimeron exposed, nearly at right angle to

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longitudinal body axis, parallel-sided; posterior lobe indistinct but present, slightly

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overlapping anterior edge of abdominal sternite II. Metatrochantin not exposed. Metacoxae as

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broad as metaventrite, completely dividing first visible abdominal sternite medially; anterior

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margin oblique, slightly curved, distinctly separated from katepisternum; lateral edge

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distinctly separated from elytral epipleura; middle portion slightly raised, with well-developed

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triangular metacoxal plates, posterolaterally forming an angle of approximately 60° but with

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rounded apex; nearly straight lateral edges of plates slightly converging anteriorly, almost

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reaching anterior metacoxal edge, only anteriormost part slightly curved outwards; entirely

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flat lateral portion of metacoxae convex along posterior and lateral margin. Metatrochanter

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about twice as large as pro- and mesotrochanter. Metafemur very similar to mesofemur in

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shape and size. Metatibia cylindrical, longer that mesotibia, with armature of very distinct

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spines and long paired apical spurs. Metatarsus distinctly longer than mesotarsus and very

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slender; tarsomere 1 strongly elongated; paire claws very similar to those of forelegs and

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middle legs. Hind wings not exposed.

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Abdomen with large shiny plate formed by sternites II-IV. Border between sternites II

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and III visible but sclerites firmly connected. Border between sternites III and IV indistinct

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but recognizable. Sternites V-VII combined about as long as distance from their anterior

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margin to hind margin of metacoxal plates. Sternites V and VI transverse, distinctly

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separated. Terminal sternite VII evenly rounded posteriorly. Exposed genital structures not

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present.

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Comment: Ovoid whitish objects at the left foreleg and ventral cervical region are probably

265

mites.

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267 268

5. Discussion

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The species described here seemingly displays a mosaic pattern of dytiscoid and carabid

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features. The placement in Adephaga is clearly indicated by the metacoxae completely

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dividing the first visible abdominal sternite and the firm connection of the anterior ventrites of

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the abdomen. No structural affinities with Gyrinidae and Haliplidae are recognizable, except

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for the strongly shortened head, which superficially resembles conditions found in the former

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family (e.g. Beutel et al., 2017). The presence of distinct metacoxal plates, the very short

275

mesoventrite, and the absence of exposed gonocoxosterna and exposed genital structures

276

exclude it from Gyrinidae (e.g. Larsén, 1966; Beutel et al., 2018). The shape and moderate

277

size of the metacoxae and the shape of the prosternal process excludes a close relationship

278

with Haliplidae (e.g. v. Vondel, 2016).

279

With its broad and flat habitus, the very short and broad head, the completely lacking

280

pronoto-elytral angle, its relatively short mesoventrite, and its lancet-shaped and elongate

281

prosternal process it resembles beetles belonging to Dytiscoidea (e.g. Belkaceme, 1991).

282

However, aside from the general body shape and transverse head (e.g. Dressler and Beutel,

283

2010), no structural features suggest aquatic habits. Swimming hairs, for instance, are entirely

284

lacking. Moreover, several features clearly suggest a placement in Carabidae. This includes

285

the antennal pubescence, which is missing in all aquatic groups, the correlated presence of a

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protibial antenna cleaner, metacoxae only as wide as the metaventrite, and exposed and nearly

11

287

parallel-sided metepimera. The last two character states are apomorphies of Carabidae

288

(Beutel, 1992), clearly excluding the fossil from the aquatic groups.

289

The middle region of the metacoxae is very similar to what is found in Noteridae

290

(Belkaceme, 1991), together with Meruidae the sistergroup of the remaining Dytiscoidea (e.g.

291

Beutel et al., 2013). However, similar triangular metacoxal plates also occur in

292

Pseudomorphini. The parsimony analyses of the character set places Burmapseudomorphus as

293

sister group of the pseudomorphine genus Sphallomorpha in a clade also containing

294

Bembidion (Trechinae), Pterostichus (Harpalinae), and Brachinus (Brachininae). The entire

295

carabid subunit is characterized by a number of thoracic character transformations

296

(apomorphies), such as the external closure of the procoxal cavities, the loss of paired

297

procoxal rests and the hexagonal groove of the mesoventrite, narrow mesepimera not reaching

298

the mesocoxal cavity, and a lobate metepimeron (Beutel, 1992). The last feature is indistinct

299

in Burmapseudomorphus, but a posterior lobe is still recognizable and slightly overlapping

300

with the anterior edge of abdominal sternite II. The fossil is superficially similar to species of

301

the migadopine genus Stichonotus, which also has a broadly ovoid body without pronoto-

302

elytral angle and an apically pointed prosternal process. However, in contrast to

303

Burmapseudomorphus and Harpalinae, the mesepimeron of Migadopini reaches the

304

mesocoxal cavity and the metepimeron is concealed and completely lacks a posterior lobe

305

(Beutel, 1992: fig. 15; Johns 2010). Moreover, the mesepimeron is distinctly broader and the

306

short apical part of the prosternal process does scarcely reach beyond the hind margin of the

307

procoxae. 12

308

A close affinity with Pseudomorphini, a specialized subgroup of Harpalinae (Ober and

309

Maddison, 2008), is suggested by different features. The short and transverse head, deeply

310

retracted into the prothorax, and the evenly rounded, stream-lined body with a laterally

311

rounded posteriorly widening pronotum are unusual apomorphic features in Carabidae.

312

Likewise, a long and apically converging prosternal process and externally closed procoxal

313

cavities is a very unusual combination in this family (Beutel, 1992). The prosternal process

314

varies in pseudomorphines from elongate to absent, but the elongate condition found in

315

Sphallomorpha and the other genera with the exception of Paussotropus (Baehr, 1997; Arndt

316

et al., 2016) is obviously plesiomorphic in the tribe. Another potential synapomorphy is the

317

triangular shape of the metacoxal plates, with converging almost straight lateral margins, a

318

condition that evolved independently in Noteridae (Beutel and Roughley, 1987; Belkaceme

319

1991). An additional diagnostic and supposedly derived feature is the shape of the mandible.

320

It is usually elongate and more or less strongly protruding in Carabidae (e.g. Dressler and

321

Beutel, 2010), even in Omophron with its distinctly shortened and compact head. In contrast,

322

the mandible of Burmapseudomorphus and Sphallomorpha is rather compact with a strongly

323

curved, relatively slender apical part, and scarcely protruding beyond the anterior labral

324

margin.

325

Despite of a number of features shared with Pseudomorphini, Burmapseudomorphus

326

obviously does not belong to the crown group of this tribe. In contrast to extant species (e.g.

327

Baehr, 1992, 1994, 1997) the fossil lacks ventral cephalic antennal groups, the submentum

328

and mentum are distinctly separated, and the elytra are not truncated posteriorly. 13

329

Consequently,

330

Pseudomorphini.

Burmapseudomorphus

should

be

assigned

to

the

stemgroup

of

331

Considering the evidence presented here and the results of the analyses, an

332

interpretation as an early representative of a specialized subgroup of Harpalinae (Ober and

333

Maddison 2008) appears solid. The broad and flat habitus suggests a possible preference for

334

narrow spaces under bark, as it is also typical for extant pseudomorphines (Fig. 3E–F). The

335

feeding habits cannot be clarified with the available material. Ants as a food source may have

336

played a role like in extant pseudomorphines, but there is no direct evidence for this. This

337

first fossil record for Pseudomorphini (stem group) documents an early origin of a group of

338

Carabidae with an unusual morphology and highly specialized life habits.

339 340

Conclusions

341

Structural features of the newly described fossil indicate that it belongs to the stemgroup of

342

the specialized carabid tribe Pseudomorphini. It shows that the group originated in the Late

343

Cretaceous (or earlier).

344 345 346 347

Acknowledgments

348

The microphotographs were taken by PD Dr. Hans Pohl (Institut für Zoologie und

349

Evolutionsforschung, FSU Jena) who also contributed the section on the procedures in 14

350

Material and methods. This gratefully acknowledged. We are very grateful to Dave Maddison

351

(Oregon State University) for very carefully checking the entire study and very helpful

352

suggestions, and also for helpful comments made by an anonymous reviewer and the editor

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Eduardo Koutsoukos. We are also grateful for financial support by the Deutsche

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Forschungsgemeinschaft DFG (BE 1789/11-1). Dong Ren was supported by grants from the

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National Natural Science Foundation of China (grants 31730087), Program for Changjiang

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Scholars and Innovative Research Team in University (IRT-17R75) and Project of Highlevel

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Teachers in Beijing Municipal Universities (IDHT20180518). Further support came from

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National Digital Museum of Animal Specimens in National Specimen Information

359

Infrastructure, supported by The Ministry of Science and Technology of the People’s

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Republic of China (Hong Pang, No. 2005DKA21402) and from Open Project of the State Key

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Laboratory of Biocontrol (Adam Slipinski, Grant No. 2018-04).

362 363 364

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FIGURE CAPTIONS

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Figure. 1. Burmapseudomorphus planus gen et sp. nov., Holotype, CNU-COL-MA-0142; A,

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habitus, dorsum; B, habitus, venter. Scale bar = 1 mm.

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Figure 2. Burmapseudomorphus planus gen et sp. nov., Holotype, CNU-COL-MA-0142; line

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drawing, venter. Abbreviations: aes2/3 – mes-/metanepisternum, ant – antenna, antcl –

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protibial antenna cleaner, ce – compound eyes, cx/3 – pro-/metacoxa, cx3pl – metacoxal

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plate, elep – elytral epipleura, ep2/3 – mes-/metepimeron, fe1 –profemur, hypr – hypomeral

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process, hy – hypomeron, lbr – labrum, md – mandible, mt – mentum, mxp – palpus

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maxillaris, pccl –closure of procoxal cavity, pl – palpus labialis, pl1 – propleura, pstpr –

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prosternal process, smt – submentum, st1 – prosternum, stII-III - abdominal sternites II-III,

490

stVII abdominal sternite VII, ta2/3 – meso-/metatarsus, ti1/2/3 – pro-/meso-/metatibia, tr3 –

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metatochanter, V3 - metaventrite.

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Figure. 3. Phylogenetic position of Burmapseudomorphus gen. nov. and examples of modern

495

representatives of its supposed sister group (Pseudomorphini). Squares on the tree indicate

496

unique (black) or non-unique synapomorphies of the particular clades (character number on

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the top and state number on the bottom corresponds to the Character list in Supplementary

498

File 1). For complete tree see Supplementary Files 2 and 3. Habitus images: A:

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Burmapseudomorphus planus gen. et sp. nov.; B: Sphallomorpha amabilis (Castelnau); C:

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Adelotopus multipunctatus Baehr; D: Cryptocephalomorpha genieri Baehr; E–G:

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Sphallomorpha laevis (Laporte de Castelnau) (E: dorsally, F: laterally, G: ventral view of the

502

head). 21

503 504 505 506

APPENDICES – Supplementary material

507 508

Supplementum 1: Burmapseudomorphus-Supplementum.doc, List of characters

509 510

Supplementum 2: Burmapseudomorphus.winc, character state matrix

511 512

Supplementum 3: Phylogeny of Adephaga and systematic position of Burmapseudomorphus

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gen. nov. Squares on the tree indicate unique (black) or non-unique synapomorphies of the

514

particular clades (character number on the top and state number on the bottom corresponds to

515

the Character list in Supplementary File 1).

516 517

22

518 519 520 521 522

23

523 524

24

-

New adephagan species Burmapseudomorphus planus discovered in Burmese amber

-

With its oval shape and flat body it resembles members of aquatic groups

-

Phylogenetic analysis places it in the stemgroup of the specialized carabid Pseudomorphini