Talbragarus Oberprieler & Oberprieler

Oberprieler, Rolf G. & Oberprieler, Stefanie K., 2012, Talbragarus averyi gen. et sp. n., the first Jurassic weevil from the southern hemisphere (Coleoptera: Curculionoidea: Nemonychidae), Zootaxa 3478, pp. 256-266 : 258-260

Genus Talbragarus Oberprieler & Oberprieler , gen. n.

Type species: Talbragarus averyi Oberprieler & Oberprieler , sp. n.

Description. Head short, transverse, sunk into prothorax without distinct temples or neck. Rostrum longer than head + prothorax, thin, evenly cylindrical, slightly downcurved; inserted in lower half of head to form a distinct sinus with head dorsally in profile; sides apparently longitudinally grooved. Eyes anterolateral, subrotund, slightly protruding from surface of head; hind margin close to anterior margin of prothorax. Mouthparts apparently with long maxillary palps. Antennae orthocerous, inserted in about middle of rostral length, reaching to about middle of prothorax in repose; funicles with segments shortly elongate, loose; clubs loosely 3-segmented, segments asymmetrically enlarged, obconical ( Fig. 3 ). Thorax with prothorax shortly subtrapezoidal, dorsally slightly convex, sides medially somewhat expanded and sharply declivous in arc towards base of pronotum ( Figs. 1, 2 , 5, 6 ), pronotum with posterior corners rounded, not fitting closely to elytra, posterior margin grooved or sharply declivous, surface densely coarsely punctate; fore coxal cavities large and contiguous, hind coxal cavities also large, transverse, apparently contiguous; scutellum small, narrow; metanepisterna narrowly triangular. Elytra slightly convex, a little more so at apex, shortly elongate, broad, more or less equally wide in anterior two-thirds, at base together wider than base of prothorax, at apex evenly individually rounded, fully covering abdomen; with distinct scutellary striole and 10 full, coarsely punctate striae but striation laterally somewhat irregular and obscured. Legs poorly preserved; fore femora large, medially slightly inflated, unarmed; surface distinctly corrugate ( Fig. 4 ); tibiae and tarsi not distinctly preserved. Abdomen with five flat, subequal, apparently free ventrites, last ventrite apically broadly rounded.

Etymology. Named after its only known site, the Talbragar Fish Bed; gender masculine.

Taxonomic placement. The distinction between the now generally recognised seven families of extant Curculionoidea ( Kuschel 1995, Oberprieler et al. 2007) is based largely on the conditions of a number of key structures, i.e. the labrum (free or fused with the clypeus), the antennae (orthocerous or gonatocerous), the gular sutures (double or single), the elytral striation (with or without scutellary strioles), the tibial apices (with or without spurs), the abdominal tergites (7th concealed under elytra or exposed as pygidium) and the tarsal claws (simple or appendiculate/bifid). Unfortunately many of these characters preserve poorly in compression fossils. This is the case also with Talbragarus, in which the tip of the rostrum and the legs are not adequately preserved in either of the two known specimens and the only relevant characters in evidence are those of the antennae, elytral striation and coverage of the abdomen. The presence of scutellary strioles excludes a placement of Talbragarus in Caridae , Brentidae and Curculionidae and the absence of a pygidium (the abdominal tergites fully covered by the elytra) excludes one in Anthribidae and Attelabidae ; the pygidium though is not always clearly visible in Attelabidae (e.g., in the Australian species classified in Auletobius Desbrochers ), but their antennae are inserted at the base of the rostrum. Also in the subfamily Oxycoryninae of Belidae are the antennae inserted basally, and the prothorax is often laterally carinate. This leaves only Nemonychidae and the subfamily Belinae of Belidae in contention for placing Talbragarus. The differentiation between these two taxa rests primarily on the condition of the labrum (free in Nemonychidae , fused in all Belidae ) and the presence of a grooming device on the fore tibiae in Belinae ( Kuschel 1995) , but neither of these characters is preserved in Talbragarus. Other differences between the two taxa occur in the length of the antennae (reaching or exceeding the base of the elytra in Belinae but not in Nemonychidae ), the size of the eyes (strongly protruding in Belinae , rarely so in Nemonychidae ), the shape of the antennal clubs (elongate in Belinae , shorter in Nemonychidae ), the fit of the prothorax to the elytra (close in Belinae , loose in Nemonychidae ), the insertion of the rostrum on the head (usually medially in Belinae , generally more ventrally in Nemonychidae ), the shape of the fore femora (short but broadly and evenly inflated in Nemonychidae , elongate and narrower in Belinae ) and the general body shape (elongate and compact in Belinae , shorter and looser in Nemonychidae ). On all of these features Talbragarus fits in Nemonychidae rather than in Belinae , and we therefore assign it to this family.

Within Nemonychidae , three extant subfamilies and one extinct are recognised ( Kuschel 1995, Oberprieler et al. 2007, Kuschel & Leschen 2011). The extant subfamily Cimberidinae differs from the other three by having nonstriate elytra, but these others are difficult to recognise in inadequately preserved fossils as the differences between them concern, among other more obscure characters, the presence of mesonotal stridulatory files and appendiculate claws ( Rhinorhynchinae ), bifid claws ( Nemonychinae ) and simple claws ( Eobelinae ) ( Kuschel & Leschen 2011). As neither the mesonotum nor any claws are preserved in the two specimens of Talbragarus, the genus cannot be unequivocally assigned to any subfamily of Nemonychidae . The only one occurring in Australia is Rhinorhynchinae , whereas Nemonychinae and also the extinct Eobelinae are to date only known from the northern hemisphere. In its short head and small, anterior eyes Talbragarus resembles the Australian rhinorhynchine genera Basiliogeus Kuschel and Basiliorhinus Kuschel (see figures in Zimmerman 1991, Kuschel & Leschen 2011) as well as the fossil described as Cratomacer immersus Zherikhin & Gratshev from the Lower Cretaceous of Santana in Brazil (see figure in Zherikhin & Gratshev 2004), which is also placed in Rhinorhynchinae ( Kuschel & Leschen 2011). Slight corrugations of the femoral surface as visible in the fossil under low-angle incident light are also evident in a number of extant Rhinorhynchinae under similar lighting conditions. In its apparently enlarged fore femora, however, Talbragarus is also similar to the Eobelinae described from the Upper Jurassic of Karatau as Ampliceps dentitibia Arnoldi , Ampliceps furcitibia Arnoldi , Archaeorrhynchus tenuicornis Martynov , Eobelus acutirostris Arnoldi, Probelopsis acutiapex Arnoldi and Scelocamptus curvipes Arnoldi (see figures in Martynov 1926, Arnoldi 1977), but this character also occurs conspicuously in the extant Australian Zimmiellus Kuschel and New-Caledonian Idiomacer Kuschel (see figures in Kuschel & Leschen 2011), thus does not facilitate an assignment of Talbragarus to either Rhinorhynchinae or Eobelinae . It is furthermore uncertain whether Eobelinae and Rhinorhynchinae were differentiated in the late Jurassic or are even properly distinct from each other, given that the condition of the tarsal claws is not clear or known in many eobeline fossils (and a variable character in weevils in any case) and that the presence or absence of mesonotal files is not established in Eobelinae and these files are absent in some Rhinorhynchinae (see Kuschel & Leschen 2011).

Figures

FIGURES 1 – 4. Talbragus averyi gen. et sp. n., holotype. 1. part (AM F. 137581); 2. counterpart (AM F. 137582); 3. left antennal club of part, magnified; 4. left fore femur of part, magnified.

FIGURES 5 – 6. Talbragus averyi gen. et sp. n., holotype; 5. part (AM F. 137581); 6. counterpart (AM F. 137582).