Two genera of extinct weevils, Sayrevilleus Gratshev & Zherikhin from Cretaceous New Jersey amber and Baltocar Kuschel from Eocene Baltic amber, are recognized as close relatives based on similarities revealed by the use of synchrotron tomography and the availability of new amber inclusions. The subfamily Sayrevilleinae Legalov stat. nov. is characterized by possessing mandibles with an external cutting edge and an inner blunt edge. The subfamily is placed in the family Attelabidae (s.l.), although some characters also suggest a possible relationship with the ‘higher weevils’ comprising Caridae, Brentidae, and Curculionidae. Sayrevilleus is transferred from the tribe Auletini of Rhynchitinae to Sayrevilleinae, and Sayrevilleus grimaldii Gratshev & Zherikhin is redescribed. Baltocar Kuschel is transferred from Caridae to Sayrevilleinae and revised, its type species, Baltocar succinicus (Voss), is redescribed and three new species, Baltocar groehni Riedel sp. nov., Baltocar hoffeinsorum Riedel sp. nov., and Baltocar subnudus Riedel sp. nov. are described based on eight well-preserved inclusions. The genera Orapauletes Legalov and Zherichiniletes Legalov previously assigned to Sayrevilleini are regarded as Curculionoidea incertae sedis. The Sayrevilleinae were distributed over areas of North America and Europe at least since the Late Cretaceous (c. 90 Mya) and were probably relatively diverse until the Eocene (c. 44 Mya). It is speculated that they became extinct through competition with Curculionidae, which used a similar oviposition strategy.

INTRODUCTION

The weevils (Curculionoidea), comprising more than 60 000 described species, are a prime example of an evolutionarily highly successful lineage, and their history and interactions with host plants are of great interest (Anderson, 1995; Farrell, 1998; McKenna et al., 2009). Fossils are critical to providing a temporal context for this success, but their state of preservation is often less than desirable and few informative characters can be recognized (e.g. Arnoldi, 1977). Inclusions in amber are usually devoid of compression artefacts and allow examination of fine details, but often the amber is not clear, the view is obscured by bubbles or cracks, and the specimen may only be observed from one aspect. Synchrotron microtomography (µCT) is a relatively new technique to overcome some of these limitations (Lak et al., 2008; Dunlop et al., 2011; Perreau & Tafforeau, 2011). It is here used to study features in specimens of relatively poor preservation, in particular the holotype of Sayrevilleus grimaldii Gratshev & Zherikhin, a species so far only known from this single inclusion in New Jersey amber.

Baltocar succinicus (Voss) is currently known from only one inclusion in Baltic amber. The species was originally described by Voss (1953) in the extant genus Car Blackburn, then classified as belonging to the family Attelabidae, but Kuschel (1992) later proposed the monotypic genus Baltocar for it and placed it in the family Caridae, which contains three extant genera and which he regarded as the most basal subfamily of Brentidae. Seven additional amber inclusions belonging to Baltocar became available for study recently, three through the courtesy of Carsten Gröhn (Glinde, Germany), two from Christel and Hans Werner Hoffeins (Hamburg, Germany), and one from a dealer. These fossilized weevils agree in generic characters with the holotype of B. succinicus, but more subtle differences show that they represent three additional species. Because of the excellent preservation of the new specimens it is possible to redescribe Baltocar more precisely and to add some characters of phylogenetic significance to its concept.

The Caridae are regarded as a small but enigmatic family of weevils (Oberprieler, in press). Recent phylogenetic classifications place it as the sister group of a clade comprising the families Brentidae and Curculionidae, with the clade Caridae + Brentidae + Curculionidae constituting the sister group of Attelabidae (Marvaldi & Morrone, 2000; Marvaldi et al., 2002, 2009; McKenna et al., 2009). All species of Caridae are associated with conifers, especially Cupressaceae. Although the members of Caridae seem well characterized by a similar habitus, their only convincing apomorphy is the loss of abdominal spiracles of segments VI and VII (Kuschel, 1992, 1995), and the monophyly of the family is therefore so far only weakly supported. The five extant genera occur only in the Southern Hemisphere (Oberprieler, Marvaldi & Anderson, 2007); the discovery of B. succinicus from Baltic amber seemed to indicate a worldwide distribution in the past (Kuschel, 1992).

Based on a poorly preserved fossil weevil, Eccoptarthrus crassipes Arnoldi, from the Upper Jurassic Karatau site in Kazakhstan, Arnoldi (1977) erected a tribe Eccoptarthrini in the extinct nemonychid subfamily Eobelinae. Zherikhin & Gratshev (1995, 1997) later regarded this specimen as being related to extant Caridae and used Eccoptarthridae as the name of the family for reasons of priority. In the generic catalogue of Alonso-Zarazaga & Lyal (1999), the family Eccoptarthridae thus comprises three subfamilies: Eccoptarthrinae, Baissorhynchinae, and Carinae. However, Kuschel (2003) could identify no character shared between Eccoptarthrini and Caridae and again treated Eccoptarthrus as a member of Eobelinae (thus of Nemonychidae). This view was supported by later authors (Oberprieler et al., 2007; McKenna et al., 2009; Bouchard et al., 2011), and Caridae is the currently accepted family group name for Car and its relatives. The taxon Baissorhynchinae was originally described from the Lower Cretaceous deposits of Baissa in Transbaikalia, Russia, as a tribe of the attelabid subfamily Rhynchitinae (Zherikhin, 1993). Kuschel (1983) drew attention to the close general similarity of Baissorhynchus with extant Caridae, but Baissorhynchus apparently possessed a free labrum (Zherikhin, 1993) and therefore again appears to represent the family Nemonychidae. In the shape of its head with the large eyes and in the shape of the rostrum it is similar to Baltocar, but these similarities are weak evidence for a close phylogenetic relationship. Baltocar differs from Baissorhynchus in the structure of the tarsus (the basal two segments in the latter short and broad as in Car, elongate and apically truncate in Baltocar) and the presence of a free labrum in Baissorhynchus. Thus, the Baissorhynchinae need to be placed either amongst the Nemonychidae (because of the free labrum), or amongst the Caridae (based on their general habitus and the tarsal structure).

Besides Caridae, the Rhynchitinae of Attelabidae show most similarities with Baltocar and Sayrevilleus. The Attelabidae are a relatively diverse family of extant weevils mainly associated with angiosperms as host plants. The family is commonly divided into the subfamilies Rhynchitinae and Attelabinae, sometimes classified as separate families. So far there is no robust phylogeny for the family, although morphological and molecular evidence indicates that Rhynchitinae are paraphyletic with respect to the Attelabinae (Riedel, in press). Sayrevilleus is currently regarded as the first record of this family and was used by McKenna et al. (2009) to calibrate a molecular phylogeny of weevils.

MATERIAL AND METHODS

This study is based on examination of the holotypes of S. grimaldii Gratshev & Zherikhin and B. succinicus (Voss) and of seven additional inclusions representing the genus Baltocar. A further similar inclusion in Baltic amber, described as Anchinvolvulus liquidus Voss, could not be located for study. This species was described by Voss (1972) in the family Attelabidae but later transferred by Kuschel (1992) to the Apioninae (Brentidae); the specimen may be misplaced at ZMUC after being returned by Kuschel. Judging from the original description, it appears possible that it belongs to Baltocar, although Kuschel's judgement makes this unlikely.

Type depositories are cited using the following abbreviations: AMNH, American Museum of Natural History, New York, USA; CGCG, Carsten Gröhn collection, Glinde, Germany; GPIH, Geologisch-Paläontologisches Institut der Universität Hamburg, Germany; HCH, Christel & Hans Werner Hoffeins collection, Hamburg, Germany; SDEI, Senckenberg Deutsches Entomologisches Institut, Müncheberg, Germany; SMNK, Staatliches Museum für Naturkunde, Karlsruhe, Germany; ZMUC, Zoological Museum, University of Copenhagen, Denmark.

All specimens were examined with a Leica MZ16 dissecting microscope using either using a Schott KL1500 or a fluorescent desktop light for optimal illumination. Photographs of specimens were taken using AUTOMONTAGE software (Syncroscopy) with a JVC KY70 digital camera adapted to a Leica Z6 Zoom-system. Some amber pieces were photographed using a Canon Eos 1Ds camera (11 megapixels) equipped with a 100 mm macro lens, mounted on a repro-stand. The camera was moved vertically and stacks of about 20 images were taken at different focal levels. The resulting images were processed with COMBINE ZP software. All photographs were improved using Adobe Photoshop CS2. Measurements were taken using the ocular micrometer of the Leica MZ16. The drafts of the line drawings of the mouthparts were prepared with the aid of a camera lucida attached to a Leitz Laborlux microscope at 100 × magnification. These drawings were corrected where necessary with the slightly better image provided by a Leica MZ16 microscope at 115 × magnification. The resulting pencil drawings were scanned and redrawn using COREL DRAW X3 software. Terminology of surface sculpture is based on Harris (1979).

The holotypes of S. grimaldii, Baltocar groehni Riedel sp. nov., and Baltocar hoffeinsorum Riedel sp. nov. were examined by µCT using the TopoTomo beamline of the ANKA National German Synchrotron Facility (KIT, Karlsruhe). The TopoTomo beamline can work either in white beam or in monochromatic mode. The available white beam energy spectrum ranges between 1.5 and 40 kiloelectron volts (keV) (flux at sample position ∼ 10⁶ photons s⁻¹, 5 mm × 10 mm beam size). The microtomographic investigations of the weevils were accomplished by using the white beam spectrum in combination with different attenuators. For every scan, 1500 projections were acquired, covering an angular range of 180°. The sample-transmitted radiation field propagated for a distance of 30 cm before reaching the detector, thus creating both absorption contrast and edge enhancing phase contrast in the projection images. The images were acquired by using an indirect high resolution X-ray imaging detector consisting of a white beam microscope from Optique Peter and a fast active pixel sensor (Photron, fastcam SA 1.1). The Photron fastcam is a 12-bit detector with 1024 × 1024 pixels, each with dimensions of 20 µm × 20 µm. For the first scans, a microscope magnification equal to 11.25 × was used, with an effective pixel size equal to 1.77 µm and a spatial resolution limit of 3.6 µm. The resolution limit R was calculated according to the Rayleigh principle. inline image , where λ is the wavelength emission peak of the lutetium aluminium garnet (LuAG) scintillator integrated in the high resolution microscope. The following X-ray attenuators were used during the scans: 0.2 mm Al and 0.7 mm Be (holotype of B. groehni Riedel sp. nov.), 2 mm Al and 0.7 mm Be (holotype of B. hoffeinsorum Riedel sp. nov.), and 2 mm Si and 0.5 mm Be (holotype of S. grimaldii). For a second scan of the holotype of B. hoffeinsorum Riedel sp. nov., the Photron camera was combined with a 4.5 × microscope magnification, which set an effective pixel size of 4.44 µm and a spatial resolution limit of 9 µm. A 0.5 mm Be attenuator was used during the experiment.

The 2D radiographic projection frames were processed with phase retrieval software (ImageJ plugin ANKAphase; Weitkamp et al., 2011). Volume reconstruction was carried out using reconstruction software developed by ANKA and using the PyHST algorithm of the European Synchrotron Radiation Facility at Grenoble.

The volumes were labelled with the software AVIZO 6.2 using the Magic Wand tool of the segmentation editor. Surface rendering was carried out by applying SurfaceGen modules to the labels. The numbers of polygons (surface triangles) of the resulting SURF files were reduced to 10% of their original values, and the data were saved as Wavefront files (.obj). The 3D objects were imported to the 3D ray tracing software MAXON CINEMA 4D to create the images. The objects were saved as Wavefront files (OBJ) and opened with the software RIGHT HEMISPHERE DEEP EXPLORATION 6. The data were saved as Universal 3D files (.u3d), opened with Adobe ACROBAT 9 PRO Extended, and integrated into PDF files.

The image data are stored at http://www.morphdbase.de under accession numbers A_Riedel_20120415-M-5.1 (B. groehni), A_Riedel_20120415-M-6.1 (S. grimaldi), A_Riedel_20120415-M-7.1 (B. hoffeinsorum, head & thorax) & A_Riedel_20120415-M-8.1 (B. hoffeinsorum, complete specimen).

SayrevilleinaeLegalov, 2003, stat. nov.

Sanyrevilleina [sic]Legalov, 2003: 85; Bouchard et al. 2011: 560.

Sanyrevilleini [sic]Legalov, 2007: 31; 2009: 292; 2010: 93.

Type genus: Sayrevilleus Gratshev & Zherikhin, 2000[stem: Sayreville-].

Sanyrevilleus Legalov, 2003[Incorrect subsequent spelling.]

Comment: Legalov's (2003) original spelling of the family-group name, Sanyrevilleina, was based on the incorrect subsequent spelling Sanyrevilleus of the type species cited, SayrevilleusGratshev & Zherikhin, 2000. The error was perpetuated in his later works as well as in the recent catalogue of beetle family-group names (Bouchard et al., 2011). According to Article 35.4.1 of the International Code of Zoological Nomenclature (1999), family-group names based on incorrect spelling of the type genus must be corrected, hence the correct name of the subtribe is Sayrevilleina and of the subfamily Sayrevilleinae.

Redescription: Eyes large, convex, dorsolateral, protruding, medially separated by less than width of rostrum. Head in lateral aspect subconical (1–10-59–66), continuing into long, curved rostrum. Antennae inserted basally, nongeniculate. In apical 1/4 of rostrum ventrally with one or two pairs of erect, stout setae. Mandibles (1–10, 16–22, 46–48, 59–66) long, lodged in deep sockets, externally dentate; either with three teeth (in Baltocar), or with two blunt teeth (in Sayrevilleus); inner edge evenly convex. Labial palps with three articles. Epistome extended forward at middle (32–45, 46–48), usually with stiff, erect setae. Prothorax with nearly straight sides converging anteriad or subparallel (11–15, 16–22, 32–45); notosternal sutures distinct, closed or open but then margins subparallel (1–10, 23–31, 49–58; compare with figs 29-5-4 F to L in Riedel, in press); at dorsal end of notosternal suture with transverse wrinkle leading to more or less distinct constriction of anterior margin of prothorax. Elytra striate; with scutellary striole (16–22, 23–31) (in Baltocar subnudus Riedel sp. nov. punctation somewhat confused), with distinct humeri, widest in apical third. Legs slender. Tibiae straight, apically each with two spurs. Tarsi long, slender (1–10, 32–45); tarsomere 1 three to four times longer than wide; tarsomere 2 apically truncate; insertion of onychium in centre of tarsomere 3. Claws divaricate, simple. Abdomen. Ventrites at same level, ventrites 1–4 subequal in length, sutures between them distinct; laterally sharply folded dorsad (1–10-32–45). Segment VI with spiracle (Fig. 36).

Details are in the caption following the image — **Figure 1–10**
Open in figure viewer PowerPoint

*Sayrevilleus grimaldii*, holotype: 1, cut amber, in a block of synthetic resin; 2, habitus; left side; 3, habitus; right side; 4, legs; arrows mark simple claws; numbers mark articles of right protarsus; 5, right side of thorax and abdomen; arrow marking side parts of abdominal ventrites; note cracked surface; 6, arrows marking teeth of right mandible; 7–9, volume rendering of synchrotron microtomography of head and thorax; 10, mouthparts: right side; ventrolateral aspect. Abbreviations: Lp, labial palp; Md, mandible; Mxp, maxillary palp; Pr, prementum.

Systematic position: Sayrevilleinae is placed besides Rhynchitinae in the family Attelabidae.

Key to the species of Sayrevilleinae

1
Forehead (Figs 7, 9) with pair of sulci bordering eyes, median subtrapezoid area elevated. Apical edge of pronotum continued ventrally to form a distinct, rounded extension in front of procoxae (Fig. 8) Sayrevilleus grimaldii
–
Forehead (32–45, 49–58, 59–66) between eyes with deep median furrow; laterally with subtriangular or crescent-shaped callus bordering eye. Pronotum in front of procoxae very short, without rounded extension Baltocar 2
2 (1′)
Body (Figs 49, 54) subglabrous, without distinct pubescence. Elytra (Fig. 51) densely, somewhat irregularly, punctate. Rostrum markedly curved and shorter (0.73 ×) than pronotum Baltocar subnudus sp. nov.
–
Body (Figs 23, 24) densely setose. Elytra (Fig. 29) with regular striae. Rostrum subequal to or longer than pronotum 3
3 (2′)
Disc of pronotum (Fig. 13) coarsely punctate, reticulate; setae somewhat widened, anteriorly scale-like Baltocar succinicus
–
Disc of pronotum (Fig. 37) colliculate, transversely irregularly rugose; setae thin 4
4 (3′)
Pronotum 1.4 × longer than wide; sides subparallel. Tarsi with onychium 1.2 × longer than tarsomere 1 Baltocar groehni sp. nov.
–
Pronotum 1.2 × longer than wide; sides converging from base to apex. Tarsi with onychium shorter than tarsomere 1 Baltocar hoffeinsorum sp. nov.

GenusSayrevilleus Gratshev& Zherikhin

Sayrevilleus Gratshev & Zherikhin, 2000: 244.

Sanyrevilleus Legalov, 2003: 85, 2007: 31; 2009: 292; 2010: 93; Bouchard et al., 2011: 560 [incorrect subsequent spelling].

Type species, by original designation: Sayrevilleus grimaldii Gratshev & Zherikhin, 2000.

Differential diagnosis: Mandible as in Figure 7, weakly exodont with two blunt teeth. Forehead (Figs 7, 9) with pair of sulci bordering eyes, median subtrapezoid area elevated. Apical edge of pronotum (Fig. 8) continued ventrally to form a rounded extension delimited by marked constriction in front of procoxae. Rostrum distinctly shorter than pronotum (0.86 ×).

Notes: The genus Sayrevilleus was described by Gratshev & Zherikhin (2000) based on a single inclusion found in Late Cretaceous New Jersey amber. These authors placed it into the tribe Auletini of Rhynchitinae (Attelabidae) based on its simple tarsal claws and an alleged confused elytral punctation. Although simple claws occur in some species of this tribe, this is an exceptional condition for Auletini as the great majority of species have claws with distinct inner teeth. The striation of the elytra of Sayrevilleus could not be assessed because of preservational artefacts. The characters of this fossil largely agree with those of Baltocar: of special significance are the tarsal structure with simple divaricate claws, a long first tarsomere, an apically subtruncate second tarsomere, and the insertion of the onychium in the centre of tarsomere 3 rather than basally as is the case in other Attelabidae and in Caridae. Additionally, the shape and structure of the head are very similar in Sayrevilleus and Baltocar (compare Figs 7–9 with Figs 61–65) with a sulcate forehead, a character never occurring in Auletini.

Sayrevilleus grimaldii Gratshev& Zherikhin new placement (Figs 1–10; for 3D model of thorax and head see Fig. S1)

Sayrevilleus grimaldii Gratshev & Zherikhin, 2000: 245–246, fig. 1.

Sanyrevilleus grimaldii: Legalov, 2003: 85, 2007: 31; 2009: 292; 2010: 94.

Holotype: Figures 6–7. New Jersey Amber: Late Cretaceous; New Jersey: Middlesex Co., Sayreville, Sunrise Landing, viii.−xi.1993; AMNH no. NJ-89; Gerard R. Case coll. (AMNH). The amber piece (Fig. 1) is cut, polished, and embedded in a thin block of synthetic resin. It can easily be examined laterally; the other thin, unpolished sides obstruct a dorsal, ventral, or apical view by light microscopy. The right side is relatively clear but the left side extensively obscured by minute bubbles. Extensive cracks in the amber obscure the specimen; it is possible that some of these structures derive from a spider web, as suggested by Gratshev & Zherikhin (2000). No dirt or debris are detectable on the surface of the beetle, as noted in the original description. However, the entire surface of the specimen including smooth surfaces (such as the rostrum or the side parts of the abdominal ventrites) has a cracked reticulated structure, resembling dried mud. This artefact probably occurred during carbonization of the specimen. Some characters, such as the fine sculpture and striation of the elytra or a possible crenulation of the tibiae, were destroyed in the process. It is therefore impossible to judge if the elytral punctation is striate or confused, as claimed by Gratshev & Zherikhin (2000). Setae are poorly preserved where visible on the inner edge of the tibiae; it is likely that the specimen was more or less densely setose, but no setae can be clearly seen and distinguished from fissures. The shape of the pronotum is artificially asymmetrical, probably as a result of lateral pressure. The apex of the rostrum (mouthparts) on the left side is damaged, probably cut off during the original preparation. The right foreleg and the right hindleg are missing. The right elytron is slightly lifted.

Redescription: Total length from elytral apex to base of rostrum c. 2.1 mm. Head including rostrum 0.69 mm long. Eyes lateral, large, subrotund, c. 0.19 mm in diameter, protruding, coarsely facetted, the ommatidia distinctly convex. Eyes medially well separated by slightly less than minimum width of rostrum (0.9 ×) dorsally; ventrally more widely separated. Forehead (as in Figs 7, 9) with pair of sulci bordering eyes, median subtrapezoid area elevated. Rostrum subcylindrical, weakly curved, length distinctly shorter than pronotum (in lateral aspect 0.67 mm long); basally with scrobes from antennal insertions to eyes. Mouthparts in apical 0.30 of rostrum. Right mandible (Figs 7, 9–10) elongate, stout, exodont, subapically with two blunt teeth on outer edge; apically pointed. Labial palps with three articles. Maxillary palps with at least three, probably more articles (uncertainty caused by transverse cracks in maxilla, impossible to distinguish from true joints between articles; Fig. 10). Antenna. Length of club 0.18 mm. Insertion dorsolaterally in basal 1/6 of rostrum, 0.11 mm from base; nongeniculate; scape hardly or just reaching anterior margin of eye; article 1 of funicle swollen; article 7 globiform. Antennal club distinct, somewhat loose, about 1.5 × wider than funicle. Terminal article of club 1.5 × longer than wide. Prothorax. Length 0.78 mm; notosternal suture difficult to define on left side, open on right side; apical edge of pronotum continued ventrally to form a rounded extension, delimited by marked constriction in front of procoxa. Procoxa subconical, prominent. Prosternum in front of procoxae short. Prosternellum and hypomeral lobes behind procoxae distinct, not fused. Elytra. Length 1.62 mm; lateral margin above dorsoanterior angle of metanepisternum with indentation. Metanepisternum subparallel, c. 4.6 × longer than wide; abdominal ventrite 1 and metanepisternum broadly joining above metacoxa. Legs. Tibiae straight, slender. Protibia relatively long, 0.62 mm. Mesotibia (0.50 mm) shorter (0.83 ×) than mesofemur (0.60 mm). Metatibia (0.55 mm) shorter (0.85 ×) than metafemur (0.65 mm). Tarsi. Tarsomere 1 of protarsus (Fig. 4) 0.17 mm, c. 3 × longer than wide; tarsomere 2 of protarsus 0.12 mm long, apically subtruncate, weakly concave, not deeply excised; tarsomere 3 of protarsus c. 0.10 mm long, c. 1.3 × longer than wide; onychium of protarsus 0.15 mm long; claws divaricate, simple. Thoracic venter. Mesocoxae separated by posterior process of mesoventrite and anterior process of metaventrite meeting near mesocoxal mid-level. Metaventrite impunctate, midline impressed. Abdomen (Fig. 5). Ventrites at same level; ventrites 1–2 subequal in length, slightly longer than ventrites 3–5; sutures between ventrites distinct; side parts of ventrites opposing elytra folded dorsad.

Note: The preservation of the unique specimen is less than optimal; thus, the description of Sayrevilleus will remain fragmentary until additional specimens become available.

GenusBaltocar Kuschel

Baltocar Kuschel, 1992: 197.

Type species, by original designation: Car succinicus Voss, 1953.

Differential diagnosis: Mandible as in 16–22, 46–48, 59–66, exodont with three teeth on outer edge; inner edge blunt, convex to tip of apical outer tooth. Forehead (32–45, 49–58, 59–66) between eyes with deep median furrow; laterally with subtriangular or crescent-shaped callus bordering eye.

Baltocar succinicus (Voss) (Figs 11–15)

Car succinicus Voss, 1953: 125–126, fig. 4.

Baltocar succinicus (Voss), Kuschel, 1992: 197.

Differential diagnosis: Pronotum (Fig. 13) elongate, 1.4 × longer than wide; sides weakly sinuate, subparallel; disc coarsely punctate, reticulate; setae usually raised above integument, somewhat widened, anteriorly scale-like. Tarsi with onychium subequal in length to tarsomere 1.

Holotype: Figures 11–15. The amber piece (Fig. 11) is dull except for one smooth surface close to the specimen. Thus the specimen can only be viewed from one side. A number of cracks and milky occlusions cover large parts of the specimen and further impede observation. A bubble (partly exposed) hangs over the basal left side of the pronotum, the scutellum, and the left elytral humerus.

Redescription: Total length from elytral apex to base of rostrum c. 2.0 mm. Head including rostrum 0.89 mm long. Eyes lateral, large, protruding, coarsely facetted, the ommatidia distinctly convex. Eyes medially well separated by c. 0.7 × minimum width of rostrum. Rostrum subcylindrical, in dorsal view subapically about 1.5 × wider than in front of antennal insertion; weakly curved, length subequal to pronotum (in lateral aspect 0.59 mm); in apical 1/4 ventrally with one erect, stout seta. Mouthparts in apical 0.18 of rostrum. Mandibles fully opened, with three teeth on outer edge each, none on inner edge. Antenna. Total length 0.82 mm, length of club 0.28 mm. Insertion laterally in basal 1/5 of rostrum, 0.096 mm from base; nongeniculate; scape elongate, extending to anterior 1/4 of eye; article 1 of funicle swollen, thicker, and shorter than scape (0.7 ×); article 2 of funicle more slender, c. 2 × longer than wide; articles 3–7 of funicle decreasing in length and slightly increasing in width, article 7 globiform. Antennal club distinct, somewhat loose, about 2 × wider than funicle. Terminal article of club 1.5 × longer than wide. Prothorax (Fig. 13) relatively narrow, length 0.58 mm, apically and basally width subequal, 0.36 mm, maximum width 0.41 mm; side nearly straight; without subapical or sub-basal constriction; pronotum coarsely punctate; vestiture of apicad directed setae coarse, somewhat raised above integument; notosternal suture distinct, closed. Procoxa subconical, prominent. Elytra. Length 1.4 mm; maximal width 0.96 mm; between distinct humeri width 0.80 mm; coarsely striate; erect sensory hairs sparse, short, fine; vestiture partly raised, coarse. Legs. Tibiae straight, slender; protibia (0.50 mm) slightly longer than profemur (0.49 mm); left mesotibia apically with two spurs. Tarsi. Tarsomere 1 of protarsus 0.15 mm, c. 3 × longer than wide; tarsomere 2 of protarsus 0.13 mm long, apically truncate and not deeply excised; tarsomere 3 of protarsus c. 0.10 mm long; onychium of protarsus 0.16 mm long; claws divaricate, simple. Abdomen. Ventrites 1–3 visible, sutures distinct.

Baltocar groehni Riedelsp. nov. (Figs 16–22, for 3D model of thorax and head see Figs S2–S3)

Differential diagnosis: Pronotum (Fig. 21) elongate, 1.4 × longer than wide; sides almost straight, subparallel; disc transversely irregularly rugose, somewhat colliculate; setae long, thin, rather recumbent. Tarsi with onychium 1.2 × longer than tarsomere 1.

Holotype: GPIH 4519, CGCG 4264. (Figs 16–22). Baltic amber, collected at Jantarny near Kaliningrad. The wedge-shaped piece of clear amber (Fig. 22) is cut, polished, and coated. The inclusion can be observed from three sides, the upper side is even. The right side of the elytron and venter are partly missing, as are both antennal clubs. The left side of the abdomen and the legs are largely obscured by fissures. The terminalia are partly extruded and reveal the specimen to be a female.

Description: Total length from elytral apex to base of rostrum c. 2.9 mm. Head including rostrum 1.59 mm long. In lateral aspect subconical, without constriction; subglabrous. Eyes large, protruding, when viewed from anterolateral angle subrotund, 0.25 mm in diameter; coarsely facetted, the ommatidia distinctly convex. Rostrum subcylindrical, apically smooth, in lateral view weakly curved, 1.2 × longer than pronotum (in lateral aspect 1.13 mm); in apical 1/5 ventrally with pair of erect, stout setae. Mouthparts in apical 0.13 of rostrum. Mandibles (Figs 17, 18) fully opened; flat; their axis somewhat slanting ventrad; three teeth on outer edge, none on inner edge; inner edge convex to tip of apical outer tooth, without any additional protrusion near apex; subapical tooth recessed from dorsal cutting edge. Labial palps clearly visible, with three articles (apical 2 clearly visible, basal one only partly visible, but clearly demarcated by stout erect bristle that is usually associated with the basal article). Antenna. Length (without club) 0.94 mm, club missing; insertion sublaterally in basal 1/9 of rostrum, 0.12 mm from base; nongeniculate; scape reaching anterior margin of eye; article 1 of funicle somewhat swollen, equal in length and width to scape, c. 2.5 × longer than wide; article 2 of funicle more slender, c. 3 × longer than wide; articles 2–6 of funicle subequal in length and width, article 7 subovate, c. 1.6 × longer than wide. Prothorax (Fig. 21). Length 0.92 mm, width basally 0.65 mm, apically 0.58 mm, sides nearly straight, subparallel; without subapical or sub-basal constriction; disc transversely irregularly rugose, somewhat colliculate, with fine punctures at insertion of setae; vestiture of subrecumbent setae on dorsum directed apicad, on sides dorsoapicad; in lateral aspect anterior edge slightly sinuate, dorsally weakly concave, above procoxa weakly convex; ventrally short, c. 0.25 mm, in front of procoxa very short, less than half as long as behind it; notosternal suture distinct, closed; seemingly continued by approximately V-shaped wrinkle; its upper branch leading towards shallow constriction in front of procoxa. Procoxa subconical, strongly prominent. Scutellum subquadrate, subglabrous. Elytra. Length 1.70 mm; maximal width in apical 1/4 1.38 mm, between humeri 1.15 mm; clearly striate; erect sensory hairs sparse, short, fine; with vestiture of partly raised setae usually reaching base or middle of following one; setae directed strictly apicad except at humeri where directed dorsad; vestiture evenly distributed, not forming patches; cuticle not concealed; behind scutellum with distinct scutellary striole (Fig. 20); stria 10 joining stria 9 slightly behind level of metacoxa. Epipleuron mesially delimited by ridge; punctate and setose as remainder of elytron. Meso- and metathorax punctate and evenly sparsely setose with subrecumbent setae (only lateral portions visible). Metanepisternum narrowing posteriorly. Legs. Tibiae straight, slender. Protibia (0.87 mm) as long as profemur (0.87 mm); metatibia (0.83 mm) shorter (0.95 ×) than metafemur (0.87 mm). Dorsal edge of meta- and mesotibia crenulate, protibia simple. Right metatibia apically with two spurs; others obscured. Tarsi all of identical length (0.6 mm) and structure. Tarsomere 1 of metatarsus 0.20 mm, c. 3 × longer than wide; tarsomere 2 of metatarsus 0.14 mm, c. 2 × longer than wide, apically truncate and not deeply excised; tarsomere 3 of metatarsus c. 0.13 mm long, about as long as wide; onychium of metatarsus 0.22 mm long, inserted in centre of tarsomere 3, distance of cavity to tarsal edge basally and laterally subequal. Claws divaricate, simple. Abdomen. Ventrites successively decreasing in length; ventrite 5 shorter than 4, but distinct; sutures between ventrites straight; venter sparsely setose with few scattered subrecumbent setae.

Etymological note: This species is named after Carsten Gröhn (Glinde, Germany), an active collector of amber fossils.

Baltocar hoffeinsorum Riedelsp. nov. (23–31, 32–45, 46–48, 59–66, for 3D model of thorax and head see Figs S4–S5)

Differential diagnosis: Pronotum c. 1.2 × longer than wide; sides converging from base to apex; disc colliculate, transversely irregularly rugose, with fine punctures at insertion of setae; setae long, thin, rather recumbent. Tarsi with onychium shorter than tarsomere 1.

Holotype: Collected at Jantarny (Palmnicken) near Kaliningrad; when collected with blue earth sediment sticking to the amber. HCH 240-2 to be deposited in SDEI. (Figs 23–31). The amber is neatly cut around the inclusion and embedded in GTS polyester resin of Vosschemie, a material with a diffraction index very close to that of amber (Hoffeins, 2001) (Fig. 30). The inclusion can be observed from six sides. No occlusions or cracks are present. The folded legs somewhat obscure the ventral surface. The abdomen protrudes ventrad; tergite VII is visible and opened. Judging from the shape of sternite VIII, the specimen is probably a male.

Paratypes: Baltic amber, collected at Jantarny near Kaliningrad. GPIH 4517, CGCG 1127. (Figs 32–39). The small piece of clear amber (Fig. 32) is polished and coated. The inclusion can be clearly observed from both sides and in dorsal view. The right body side is partly covered (along the elytral suture and anteriad to the head) with a thin layer of a material that may be mould. The abdomen is protruded ventrad; the left side of tergite VII is visible, the greater part of which is concealed by the tips of the protruding wings. Judging from the shape and the length of the rostrum (1.12 × longer than pronotum), the specimen is probably a male (paratype 1).

GPIH 4518, CGCG 1125. (Figs 40–45). The small piece of clear amber (Fig. 40) is polished and coated. The inclusion can be observed from six sides but observation suffers in some aspects from optical distortions. The right side of the body and the ventral surface of head and parts of the legs are obscured by milky occlusions. The head is dislocated, hanging vertically down from the body. The right elytron is somewhat uplifted. The abdomen is protruded ventrad. The right protarsus is cut off. Judging from the shape and the length of the rostrum (1.41 × longer than pronotum), the specimen is probably a female.

SMNK-E-Col-50. The small piece of clear amber is polished and contains besides the weevil also a small cockroach. The inclusion is best observed from a lateral aspect and from the front. No occlusions or cracks are present. Judging from the shape and the length of the rostrum (1.12 × longer than pronotum), the specimen is probably a male (paratype 2).

Description of holotype: (Data referring to male paratype 1/paratype 2 are given in parentheses.) Total length from elytral apex to base of rostrum c. 2.7 mm (c. 2.7/3.0 mm). Head including rostrum 1.20 mm (1.25/1.6 mm) long. In lateral aspect subconical, without constriction; subglabrous; ventrally weakly rugose, midline somewhat impressed, basally with simple gular suture. Eyes (Figs 25, 26) large, protruding, when viewed from anterodorsolateral angle subrotund, 0.22 mm (0.22/0.24 mm) in diameter; coarsely facetted, ommatidia distinctly convex. Eyes medially well separated by slightly less than minimum width of rostrum (0.9 ×) dorsally; ventrally more widely separated. Forehead (as in Fig. 42) between eyes with deep median furrow; laterally with crescent-shaped callus bordering eye; this callus with sparse long setae; behind eye with row of punctures, surface subglabrous, almost smooth but with weak wrinkles and with few short setae; in posterior half (where usually inside prothorax) with transverse striation. Rostrum in lateral view subcylindrical, apically at mouthparts swollen; weakly curved, almost straight (Figs 25, 26), slightly [1.02 × (1.12/1.12 ×)] longer than pronotum; in lateral aspect 0.75 mm (0.85/1.12 mm) long; surface subglabrous, with shallow punctures; dorsally between antennal insertions simple, without swelling but medially with shallow furrow; at antennal insertion simple, without cavity; in apical 0.27 ventrally with pair of erect stout setae; one similar pair of such setae slightly more apicad immediately behind insertions of maxillae (Fig. 46). Mouthparts (Figs 46–48) in apical 0.20 of rostrum. Epistome extended tongue-like, on each side with three stiff stout erect setae, medially with incision and with one more pair of stout setae pointing apicad. Mandibles fully opened, three teeth on outer edge; second tooth below cavity on dorsal surface; inner edge convex to tip of apical outer tooth, without any additional protrusion near apex; mandible lodged in deep socket, only slightly projecting beyond rostral apex. Maxillary palp on dorsal surface of galea, relatively short, with three articles. Galea relatively large, ventrally covering maxillary palp. Lacinia indistinct, presumably fused to galea. Labial palp with three articles; basal article with stiff anteriad curving seta. Labium without distinct ligula (if present, it is indistinct). Antenna. Total length 1.08 mm (1.08/1.20 mm), length of club 0.32 mm (0.34/0.35 mm). Insertion sublaterally in basal 1/10 (1/8, 1/9) of rostrum, 0.07 mm (0.10/0.10 mm) from base, dorsally above lateral midline; nongeniculate; scape reaching anterior margin of eye; article 1 of funicle somewhat swollen, subequal in length and width to scape; article 2 of funicle more slender, c. 4 × (c. 3/4 ×) longer than wide; articles 3–7 of funicle decreasing in length, width subequal, article 7 subovate, c. 1.5 × (c. 1.6/1.6 ×) longer than wide. Antennal club distinct, somewhat loose, about 2 × wider than funicle; relatively sparsely setose, coverage of long setae not concealing reticulate surface; articles of club with subapical fringe of long setae; terminal article of club 2.0 × (2.0/2.0 ×) longer than wide. Prothorax. Length 0.76 mm (0.76/1.00 mm), width basally 0.59 mm (0.61/0.73 mm), apically 0.45 mm (0.49/0.57 mm), converging with nearly straight sides; without subapical or sub-basal constriction; disc (Fig. 37) colliculate, transversely irregularly rugose, with fine punctures at insertion of setae; vestiture of recumbent setae on dorsum directed apicad, on sides dorsoapicad; in lateral aspect anterior edge slightly sinuate, dorsally convex, above procoxa with shallow constriction; ventrally short, 0.25 mm (0.28/0.35 mm), in front of procoxa very short, less than half as long as behind it; notosternal suture distinct, closed but not fused, straight, directed vertically, in line with axis of procoxa; seemingly continued by approximately V-shaped wrinkle; its upper branch leading towards shallow constriction in front of procoxa. Procoxa subconical, strongly prominent. Scutellum subtrapezoid, subglabrous. Elytra. Length 1.68 mm (1.74/2.20 mm); maximal width in apical third 1.10 mm (1.08/? mm), between humeri 0.94 mm (0.98/1.26 mm); with ten regular stria and a distinct scutellary striole consisting of c. five punctures; punctures of striae coarse; erect sensory hairs sparse, short, fine; with vestiture of subrecumbent setae; usually seta reaching base or middle of following one; setae directed strictly apicad except at humeri where directed dorsad; vestiture evenly distributed, without forming patches; cuticle not concealed; stria 10 joining stria 9 above metacoxa (Fig. 24). Epipleuron mesially delimited by ridge; punctate and setose as remainder of elytron. Meso- and metathorax punctate and evenly sparsely setose with subrecumbent setae. Mesocoxal cavities laterally narrowly closed by process of mesoventrite meeting metaventrite. Mesonepisternum somewhat extended ventrad. Mesocoxae medially narrowly separated. Metanepisternum with dorsoanterior process fitting into indentation of elytral margin (Fig. 31); posteriorly narrowing, in front of metacoxa its width c. 0.11 × (0.11) its total length; posteriorly extending over metacoxa, joining abdominal ventrite 1, separating metacoxa from elytral margin. Metaventrite convex. Legs. Tibiae straight, slender. Protibia (0.78 mm) (0.85/0.93 mm) long, 1.18 × (1.23/1.15 ×) longer than profemur (0.66 mm) (0.69/0.81 mm); mesotibia (0.60 mm) (0.68/0.85 mm) shorter (0.91 ×) than (equal to/equal to) mesofemur (0.66 mm) (0.68/0.85 mm); metatibia (0.66 mm) (0.66/0.78 mm) shorter (0.92 ×) (0.90/0.95 ×) than metafemur (0.72 mm) (0.73/0.82 mm). Dorsal edge of meta- and mesotibia crenulate, protibia simple. Left protibia and left mesotibia apically with two spurs; others obscured (right protibia and right metatibia apically with two spurs; others obscured). Tarsi. Length and structure of protarsus, mesotarsus and metatarsus identical; length c. 0.52 mm (0.52/0.65 mm) each. Tarsomere 1 of protarsus 0.22 mm (0.24/0.23 mm) long, c. 3 × (4/3 ×) longer than wide; tarsomere 2 of protarsus 0.12 mm (0.15/0.20 mm) long, c. 2.0 × (c. 2.5/2.8 ×) longer than wide, apically truncate and not deeply excised; tarsomere 3 of protarsus c. 0.10 mm (0.12/0.16 mm) long, c. 1.3 × (1.3/1.6 ×) longer than wide; onychium of protarsus 0.20 mm (0.17/0.22 mm) long; insertion of onychium in centre of tarsomere 3, distance of cavity to tarsal edge basally and laterally subequal. Claws divaricate, simple. Abdomen. Abdominal ventrite 1 with concave margin bordering metacoxa, laterally wider than ventrite 2; at level of femoral articulation slightly shorter; following ventrites successively decreasing in length; ventrite 5 shorter than 4, apically rounded, base truncate; sutures between ventrites straight; venter sparsely setose with erect long setae. Side parts of ventrites opposing elytra sharply folded dorsad, vertical to ventral surface; relatively high (23–31, 32–45). [Abdominal segment VI with spiracle (Fig. 36).] Tergite VII basally with wing-folding patch, apically punctate and setose; probably fully covered by elytra if abdomen is not protruded. Sternite VIII partly visible on left side, subtriangular and laterally almost reaching tergite VIII.

Presumably female paratype (GPIH 4518, CGCG 1125) same as description of males except: total length from elytral apex to base of rostrum c. 2.9 mm. Head including rostrum 1.62 mm long; except rostrum 0.38 mm long. Figures 40–45. Rostrum in lateral view (Fig. 43) weakly curved, 1.41 × longer than pronotum (in dorsal aspect 1.06 mm); in dorsal view slightly widening from base to apex, subapically about 1.3 × wider than in front of antennal insertion; dorsal surface in basal 2/3 with sparse shallow punctures; epistome (Fig. 44) extended at middle, of subtrapezoid shape, medially and sublaterally this extension with shallow constrictions; from base to antennal insertion dorsally flattened, medially with furrow. Antenna. Total length 1.40 mm, length of club 0.31 mm. Insertion sublaterally in basal 1/9 of rostrum, 0.12 mm from base; article 2 of funicle more slender, c. 2.4 × longer than wide; article 7 subovate, c. 1.8 × longer than wide. Prothorax. Length 0.75 mm, width basally 0.70 mm, apically 0.52 mm, distinctly converging with nearly straight side; ventrally short, 0.24 mm. Elytra. Length 1.84 mm; width between humeri 1.00 mm; inferolateral fold apicad from flange of elytron present. Legs. Protibia (1.03 mm) 1.22 × longer than profemur (0.84 mm); mesotibia (0.81 mm) as long as mesofemur (0.81 mm); metatibia (0.84 mm) shorter (0.95 ×) than metafemur (0.88 mm). Tarsi. Length of protarsus 0.81 mm, mesotarsus and metatarsus 0.75 mm long. Tarsomere 1 of protarsus 0.31 mm long, c. 3.4 × longer than wide; tarsomere 2 of protarsus 0.17 mm long, c. 1.9 × longer than wide, apically truncate and not deeply excised; tarsomere 3 of protarsus c. 0.12 mm long, c. 1.1 × longer than wide; onychium of protarsus 0.23 mm long. Abdomen. Sutures between ventrites in lateral aspect straight, in ventral aspect sutures appearing increasingly convex from base to apex.

Etymological note: This species is named after Christel and Hans Werner Hoffeins (Hamburg, Germany), a couple with a great interest in the study of fossil Diptera. They provided the holotype of the described species and helped in its excellent preparation.

Notes: Besides the characters of the pronotum given in the differential diagnosis, B. hoffeinsorum Riedel sp. nov. and B. succinicus (Voss) also differ distinctly in body size (B. succinicus: 2.0 mm; B. hoffeinsorum Riedel sp. nov.: 2.7–2.9 mm), the length of the rostrum (B. succinicus: 0.98 × as long as pronotum; B. hoffeinsorum Riedel sp. nov.: 1.02–1.41 × longer than pronotum), and the shape of the antenna (B. succinicus: terminal article of antennal club 1.5 × longer than wide; B. hoffeinsorum Riedel sp. nov.: antenna more slender, terminal article of club 2.0 × longer than wide). As these characters are often subject to sexual dimorphism in extant weevils and because the gender of the holotype of B. succinicus is unclear, I refrain from using these characters as diagnostic. The other characters given in the diagnosis (sculpture and vestiture of pronotum; length of onychia) are independent of sexual dimorphism in extant weevils and therefore require the specimens to be treated as four distinct species of Baltocar based on the available material.

Baltocar subnudus Riedelsp. nov. (Figs 49–58)

Differential diagnosis: Body subglabrous, without or with indistinct pubescence. Rostrum relatively short and markedly curved. Elytra densely, somewhat irregularly punctate. Tarsi with onychium 0.7–1.1 × longer than tarsomere 1.

Holotype: Collected at Jantarny (Palmnicken) near Kaliningrad. HCH 884 to be deposited in SDEI. (Figs 49–53). The amber is neatly cut around the inclusion and embedded in GTS polyester resin of Vosschemie, a material with a diffraction index very close to amber (Hoffeins, 2001) (Fig. 56). The inclusion can be observed from six sides, but is tilted to the left, complicating some measurements. A crest of cracks exists around the specimen. Judging from the slightly projecting rim of tergite VIII, the specimen is probably a male.

Paratypes: Baltic amber, collected at Jantarny near Kaliningrad. CGCG 7977. (Figs 54–55, 57–58). The small piece of clear amber (Fig. 57) is polished and coated. The inclusion is tilted to the side and can be observed from the dorsolateral and ventrolateral aspects. There is a crack along the median plane. The specimen is a female with the ovipositor protruded.

Description of holotype: (Data referring to female paratype are given in parentheses.) Total length from elytral apex to base of rostrum c. 2.5 mm (2.3 mm). Head including rostrum 1.03 mm (0.88 mm) long. Eyes large, protruding, subrotund, 0.22 mm (0.18 mm) in diameter; coarsely facetted, the individual ommatidia distinctly convex. Eyes dorsally well separated by about minimum width of rostrum. Forehead between eyes with deep median furrow (appearing flat); laterally with subtriangular callus bordering eye; this callus with few punctures, without setae (apparently without such callus); behind eye punctate, posteriorly with transverse striation. Rostrum in lateral view subcylindrical, markedly curved, shorter (0.73 ×) than pronotum (1.1 × longer than pronotum); in lateral aspect 0.55 mm (0.55 mm) long; surface subglabrous, with sparse minute punctures. Mouthparts in apical 0.24 (0.22) of rostrum. Epistome medially with incision, without visible setae. Mandibles opened, thin, three teeth on outer edge; second tooth below cavity on dorsal surface; inner edge evenly convex to tip of apical outer tooth; mandible lodged in deep socket, distinctly projecting beyond rostral apex. Antenna. Total length 0.81 mm (0.91 mm), length of club 0.26 mm (0.33 mm). Insertion sublaterally in basal 1/6 of rostrum; nongeniculate; scape reaching anterior margin of eye; article 1 of funicle somewhat swollen, shorter (0.7 ×) than (subequal to) scape; article 2 of funicle more slender, c. 3.5 × longer than wide; articles 3–7 of funicle decreasing in length, width subequal, article 7 subovate, c. 1.3 × longer than wide. Antennal club distinct, somewhat loose, about 2 × (3 ×) as wide as funicle; sparsely setose; terminal article of club 1.8 × (2.0 ×) longer than wide. Prothorax. Length 0.81 mm (0.50 mm), width basally 0.63 mm, apically 0.55 mm; without subapical or sub-basal constriction; disc coriaceous with interspersed minute punctures, nude; ventrally short, 0.26 mm, in front of procoxa very short, less than half as long as behind it; notosternal suture open, straight, directed vertically, approximately in line with axis of procoxa; seemingly continued by approximately V-shaped wrinkle; its upper branch leading towards shallow constriction in front of procoxa. Procoxa subconical, strongly prominent. Scutellum subtrapezoid, subglabrous. Elytra. Length 1.76 mm (1.76 mm); maximal width in apical third 1.28 mm (1.14 mm), between humeri 0.94 mm (0.90 mm); punctures coarse, interspaces between them about as wide as their diameter, partly arranged in rows, but pattern of striae largely obscured by interspersed punctures; with hardly visible sparse vestiture of subrecumbent thin setae (striae and intervals each with c. one row of recumbent setae). Epipleuron mesially delimited by ridge; posteriorly weakly irregularly sculptured, anteriorly glabrous. Meso- and metathorax subglabrous, laterally punctate, metathorax anteriorly with row of punctures. Mesocoxal cavities laterally open, process of mesoventrite not meeting metaventrite. Metanepisternum with dorsoanterior process fitting into indentation of elytral margin; posteriorly narrowing, in front of metacoxa its width c. 0.11 × its total length; posteriorly extending over metacoxa, and overlapping abdominal ventrite 1, separating metacoxa from elytral margin. Metaventrite convex, in posterior half midline impressed. Legs. Tibiae straight, slender. Protibia (0.72 mm) (0.78 mm) 1.26 × (1.30 ×) longer than profemur (0.57 mm) (0.60 mm); mesotibia (0.62 mm) (0.70 mm) 1.19 × (1.11 ×) longer than mesofemur (0.52 mm) (0.63 mm); metatibia (0.61 mm) (0.61 mm) shorter (0.86 ×) (1.07 × longer) than metafemur (0.71 mm) (0.57). Tibial crenulation not visible, possibly indistinct (without tibial crenulation). Tibial spurs not visible, possibly indistinct. Tarsi. Length and structure of protarsus, mesotarsus, and metatarsus identical; length c. 0.55 mm each. Tarsomere 1 of protarsus 0.20 mm (0.20 mm) long, c. 3 × longer than wide; tarsomere 2 of protarsus 0.14 mm (0.12 mm) long, c. 3.0 × longer than wide, apically truncate and not deeply excised; tarsomere 3 of protarsus c. 0.11 mm (0.09 mm), c. 1.3 × longer than wide; onychium of protarsus 0.21 mm (0.13 mm) long; insertion of onychium in centre of tarsomere 3, distance of cavity to tarsal edge basally and laterally subequal. Claws divaricate, simple. Abdomen. Abdominal ventrite 1 with concave margin bordering metacoxa, laterally subequal to ventrite 2, at level of femoral articulation shorter (0.75 ×); following ventrites successively decreasing in length; ventrites 1–3 subglabrous, ventrites 4 and 5 more densely punctate; segment VIII somewhat projecting, but largely concealed by cracks in the amber.

Notes: The male holotype and the female paratype agree in general body form: the curved shape of the short rostrum, and the sparse to nearly absent pubescence. The different lengths of the tarsal onychium and the structure of the forehead could indicate that they represent distinct species; however, the cracks in the amber enclosing the paratype preclude an unequivocal description of its forehead, and the different lengths of the onychium may be a sexually dimorphic character. Additional data would be needed to clarify the specific status of the paratype.

DISCUSSION

The use of synchrotron microtomography in taxonomic practice

The potential of µCT has been demonstrated before, but in taxonomic practice circumstances differ from unique experiments designed to show the capabilities of this technique (Lak et al., 2008; Perreau & Tafforeau, 2011). The examination of holotypes of previously described species is especially difficult. First, specimens of such excellent preservation as examined by Perreau & Tafforeau (2011) will remain an exception. None of the inclusions available for this study had internal structures such as genitalia preserved. On the contrary, even the external cuticle of many specimens was degraded and covered by a fine network of cracks. The presence of such artificial sutures creates problems in the reconstruction as they interfere with natural structures of the specimen. This was the case with the holotype of S. grimaldii, the only known specimen. It is possible to ‘repair’ such artefacts by manual segmentation, but the risk of introducing inaccuracies is substantial even if care is taken and a lot of time is invested. The fastest and most convenient way to visualize the 3D structure of the specimen is a simple greyscale-based volume rendering or a surface model; the latter has the advantage that it can be embedded into PDF documents. However, it is not always easy to identify the greyscales that define the specimen as, owing to Fresnel diffraction, phase contrast imaging results in white-black fringes in the images (Betz et al., 2007). Moreover, amber inclusions often consist of the remains of the inclusion and the negative imprint, which are represented by different greyscales. Thus, it can be tricky to define the parameters that guarantee the best 3D visualization. Occlusions of debris present an additional challenge. If they are separated from the specimen, they can be removed easily during postprocessing, but debris or bubbles in direct contact with the specimen are more difficult and time-consuming to remove. There is a great responsibility not to deteriorate the condition of valuable type-material, usually borrowed from museums. X-rays can cause amber to darken, and this effect should first be tested with a blank piece of amber of the same type. Furthermore, resins used to embed amber pieces often have a different absorption and may suffer heat damage during the scan.

These efforts and risks not withstanding, the ability to visualize a virtual specimen from all angles and without reflections or occlusions is of great value in taxonomy. Character states used in the description and classification of a specimen may be corrected and additional characters may be detected. For instance, in Sayrevilleus the notosternal sutures, an important character in family classification, were deemed to be closed when examined by light-microscopy, but the µCT scan revealed them to be open instead. Moreover, the resulting ‘virtual specimen’ can be made widely accessible to the scientific community, a clear benefit especially in the case of type specimens that may become lost or degraded in storage over time. At present, the biggest obstacle to using synchrotron microtomography more routinely in taxonomy is the limitation of beam-time. Long waiting periods are usually involved and borrowed specimens (in our case the type of B. succinicus) may need to be returned to their owner before a µCT scan can be recorded.

Phylogenetic position of Sayrevilleinae

The majority of external morphological characters used in weevil systematics exhibits a high degree of homoplasy. In the extant fauna this problem can be alleviated by the addition of internal characters, characters from other life stages (such as larvae), and/or molecular data. Such additional character sets are unavailable for fossils, both inclusions in amber and sedimentary impressions. As regards the phylogenetic position of the Sayrevilleinae, this problem is exacerbated by the absence of a robust phylogeny of the Attelabidae. The two commonly accepted subfamilies, Rhynchitinae and Attelabinae, exhibit several different character states, but it remains unclear whether both are monophyletic and sister groups or whether Rhynchitinae are paraphyletic with respect to Attelabinae. The unequivocal apomorphies of Attelabidae presently all relate to internal and preimaginal characters (Riedel, in press). Given these uncertainties and the limited data from the fossils at hand, a proper phylogenetic analysis including the extinct genera is likely to produce highly unstable results and to suggest a certainty of relationships that is not warranted at the moment. Therefore, the placement of Sayrevilleinae is here based only on a summary of the available character evidence.

The weight of current evidence supports the placement of Sayrevilleinae in the family Attelabidae. Their peculiar mouthparts can be readily derived from a rhynchitine type, and the structure of the head, specifically the position of the antennal insertions and scrobes and the anteriorly produced, lobed epistome, and the crenulate edges of the middle and hind tibiae (all three characters of unknown polarity), support such a relationship. Furthermore the presence of a scutellary striole (although a plesiomorphic feature in weevils) is compatible with this placement. The loss of a cutting internal mandibular edge and a possibly correlated modification of the maxillae may represent apomorphic characters of Sayrevilleinae. The open condition of the notosternal sutures of B. subnudus sp. nov. presents a further agreement with Attelabidae, although most specimens of Baltocar have closed sutures, the condition in higher weevils. The condition in Sayrevilleus is hard to interpret because the pronotum of the specimen is strongly distorted and the open notosternal suture on one side may be artificial. The structure of the tarsi is less consistent with a placement in Attelabidae: simple divaricate claws, an onychium inserted in the centre of the third tarsomere, and a long slender first tarsomere are never found in Attelabidae, but rather resemble early Curculionidae. Finally, two characters related to the locking of the elytra into a resting position show states typical of the Caridae+Brentidae+Curculionidae clade: (1) the dorsoapical angle of the metanepisternum cutting into the lateral elytral margin, and (2) the abdominal ventrites laterally sharply folded dorsad and their glabrous side parts fitting tightly against the elytra.

Superficially, Sayrevilleinae show some resemblance to Caridae, but the presence of a spiracle on segment VI and of a scutellary striole preclude a placement in this family. Therefore, at present they are best accommodated in the family Attelabidae, although the conflicting evidence of some characters suggest that the Sayrevilleinae may be a distinct lineage branching off after the Attelabidae, possibly the sister group of Caridae + Brentidae + Curculionidae. At present, our conception of what the representatives of this stem lineage looked like is filled with uncertainties. It may well be the case that it possessed externally dentate mandibles (present in Attelabidae, but also in Car Blackburn; Zimmerman, 1994) and crenulate tibiae (present in Attelabidae, but also in several Belidae and in Carodes Zimmerman; Zimmerman, 1994). If these characters were lost in the great majority of modern weevils, they may appear to be typical of attelabids, whereas in fact they are plesiomorphies.

Fossil record of Sayrevilleinae

So far, four species of Baltocar can be identified based on eight inclusions of the genus in Baltic amber. Considering the few specimens available, the diversity within the group may have been relatively high. In the samples of amber available for this study, the number of Baltocar inclusions equals that of Rhynchitinae, a group that today numbers more than 1500 species. It thus appears that Baltocar may have flourished in the ancient amber forests dominated by conifers (Weitschat & Wichard, 2002) but then became extinct. Baltic amber is about 44 Myr in age (Kosmowska-Ceranowicz & Müller, 1985; Ritzkowski, 1997), whereas the New Jersey amber of Sayrevilleus is from the Late Cretaceous Turonian period (94–89 Mya), about twice as old. In spite of this considerable gap in both space and time between the two genera, they are morphologically remarkably similar. During the Late Cretaceous, North America and the Baltic area were much closer, with Greenland in a more southern position and thus perhaps having served as a stepping stone between the two (Scotese, 2002).

The genera Orapauletes Legalov and Zherichiniletes Legalov were listed by Legalov (2009, 2010) as Sanyrevilleini [sic]. However, the preservation of these fossils is too poor to allow an assignment to a family let alone to a genus or species. Both were so considered by their discoverers (Zherikhin, 1993; Kuschel, Oberprieler & Rayner, 1994) and therefore not described. Legalov (2007, 2009) proposed a name based on insufficient characters and without seeing the original specimens. To avoid further confusion, Orapauletes Legalov and Zherichiniletes Legalov should be regarded as Curculionoidea incertae sedis.

Biology

Anderson (1995) suggested that the rostrum was a key innovation for the success of Curculionoidea. Its main function is that of an ovipositor, used to prepare the oviposition site and to allow eggs to be deposited deeply into plant substrates. At the initial stage of weevil evolution rather loose substrates were used, such as male strobili of conifers by Nemonychidae, whose larvae are relatively mobile and whose females do not generally use their rostrum to prepare an oviposition site (Anderson, 1995). A true ‘oviposition-rostrum’ is found in Belidae, Caridae, Brentidae, and Curculionidae (Oberprieler et al., 2007). The rostrum is subrotund in cross-section and in the first three families the antennae are usually inserted basally whereas they are geniculate in most Curculionidae, and thus suitable to be inserted deeply into the substrate with their full length. This is necessary during oviposition of cones or fruits with a thick protective layer. Based on the structure of their rostrum Sayrevilleinae belonged to this oviposition type, unlike most Attelabidae, which develop in wilting plant parts.

The mandibles of Baltocar are extraordinary: their inner edge is evenly convex and blunt, whereas the external edge has three sharp teeth suitable for cutting. Although exodont mandibles do occur in other weevils such as Car and most notably Rhynchitinae, the inner edge is usually concave and well capable of some cutting action. A mandible typical of Rhynchitinae is apically T-shaped, with a concave inner edge and an inner tooth opposing an outer tooth at the apex. In Baltocar, the inner edge of the mandible is evenly convex. With such a construction it seems unlikely that food intake was the primary purpose, if it was possible at all. The main function was probably to drill holes for oviposition. However, a very similar construction of mouthparts is found in the extant subtribe Meriphina (Eugnomini, Curculionidae). This group comprises the genera Meriphus Erichson, Myossita Pascoe, and Orpha Pascoe, all confined to the Australian region (Alonso-Zarazaga & Lyal, 1999). The structure of their mouthparts appears very similar to Baltocar, including an apicad produced epistome possessing stiff setae (Marshall, 1937). Meriphus appears to feed on open flowers although its mandibles may be adapted for sawing into bark under which the eggs are laid (R. Oberprieler, pers. comm.). The genus Myossita breeds in hard Banksia infructescences (May, 1994). A closer study of the biology and functional morphology of Meriphina may give us a good idea of how the Sayrevilleinae fed and developed.

Until the Eocene the Sayrevilleinae seemed to be as numerous and diverse as the Rhynchitinae, a subfamily that is still successful today. This may be explained by the competition of the more advanced Curculionidae that diversified at the time. Their rostrum with geniculate antennae is even more efficient as an oviposition tool (Oberprieler et al., 2007). Whereas Sayrevilleinae and Curculionidae were probably competing for similar resources, Rhynchitinae and Attelabinae managed to survive by occupying other ecological niches. Their strategy of oviposition by cutting and rolling angiosperm shoots, fruits or leaves seems sufficiently different from their closest relatives. The phenomenal success of the Curculionidae may have caused the demise of the Sayrevilleinae.

ACKNOWLEDGEMENTS

We thank C. Gröhn (Glinde) for the loan of amber weevils that triggered this study, C and H. W. Hoffeins (Hamburg, Germany) for additional specimens of excellent preservation, Prof. M. Wanat (Wroclaw) for drawing our attention to them, Prof. W. Weitschat (GPIMH, Hamburg) for the loan of the holotype of B. succinicus and to Prof. D. Grimaldi (AMNH, New York) for the loan of the holotype of S. grimaldii. The help of Dr L. Vilhelmsen (ZMUC, Copenhagen) in our attempts to locate the holotype of Anchinvolvulus liquidus is gratefully acknowledged. Dr M. Alonso-Zarazaga (Madrid) gave some advice on nomenclature and Dr R. Oberprieler (Canberra) provided important information and stimulation throughout the preparation of this manuscript. Both he and Dr R. Anderson (Ottawa) suggested many helpful improvements on earlier drafts. Last, but not least, we thank S. Scharf for performing the segmentation of one µCT scan. Beam-time at ANKA and the support of Prof. T. Baumbach are also gratefully acknowledged.

Supporting Information

Figure S1. 3D model of Sayrevilleus grimaldii, holotype; head and thorax. Click on the image for interactive 3D view (Adobe Reader 8.1 or higher required).

Figure S2. 3D model of Baltocar groehni Riedel sp. nov., holotype; head. Click on the image for interactive 3D view (Adobe Reader 8.1 or higher required).

Figure S3. Segmented 3D model of Baltocar groehni Riedel sp. nov., holotype; head. Click on the image for interactive 3D view (Adobe Reader 8.1 or higher required).

Figure S4. 3D model of Baltocar hoffeinsorum Riedel sp. nov., holotype; head and thorax. Click on the image for interactive 3D view (Adobe Reader 8.1 or higher required).

Figure S5. 3D model of Baltocar hoffeinsorum Riedel sp. nov., holotype. Click on the image for interactive 3D view (Adobe Reader 8.1 or higher required).

Filename	Description
ZOJ_825_sm_FigS1.pdf9.9 MB	Supporting info item
ZOJ_825_sm_FigS2.pdf4.7 MB	Supporting info item
ZOJ_825_sm_FigS3.pdf4.2 MB	Supporting info item
ZOJ_825_sm_FigS4.pdf9.5 MB	Supporting info item
ZOJ_825_sm_FigS5.pdf2.7 MB	Supporting info item

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Citing Literature

Volume165, Issue4

August 2012

Pages 773-794

Sayrevilleinae Legalov, a newly recognised subfamily of fossil weevils (Coleoptera, Curculionoidea, Attelabidae) and the use of synchrotron microtomography to examine inclusions in amber

Abstract

INTRODUCTION