Abstract: A specimen of Curculionidae (Curculioninae) is described as Arariperhinus monnei gen. et sp. nov. The specimen is preserved on a laminated limestone sample of the Crato Formation (Santana Group), Lower Cretaceous (Aptian–Albian), and was collected from a quarry near Nova Olinda, Chapada do Araripe, State of Ceará, Brazil. The genus is placed in the subfamily Curculioninae because of its strongly convex body and relatively slender rostrum, but mainly by its rounded eyes and lack of a prosternal sulcus and tibial spurs. The very prominent eyes in lateral view, a cylindrical rostrum and a straight posterior margin of ventrite II are strong indications that this fossil belongs to the tribe Anthonomini. However, the claws, which would resolve the exact placement of this fossil, are poorly preserved. Arariperhinus monnei gen. et sp. nov. is distinguishable by the combination of several characters and the first record of the family Curculionidae in the Santana Group; it is the oldest record of a member of the subfamily Curculioninae.
T he weevil superfamily Curculionoidea is the largest known group of metazoans, containing about 62 000 described species in 5800 genera. A single family, the Curculionidae, comprises about 51 000 species in 4600 genera (Oberprieler et al. 2007). The large number of species is because of the extreme richness of forms in this group, which has adapted to nearly all biological niches (except the oceans) all over the world, and are important pests or agents for biological control (Zimmerman 1994).
According to Gromov et al. (1993) and Zherikhin inMarvaldi et al. (2002), the oldest record of Curculionidae is Cretulio nucula from the Lower Cretaceous (Upper Albian) of the Ulya River Basin (Ankiskaya Formation) in north-east Siberia. Most of the Lower Cretaceous weevil fossils (from Sierra del Montsec, Spain; Yixian, China; Bon-Tsagan, Mongolia; Khetana, Russia; and Santana, Brazil) are members of the Nemonychidae, with only a few genera and species described (Oberprieler et al. 2007). These authors stated that the earliest true members of the Curculionidae are still-undescribed specimens from the Upper Cretaceous (Turonian) at sites in Orapa (Kuschel et al. 1994) and Kzyl-Zhar in Kazakhstan (Gratshev and Zherikhin 2003). Other, later and incomplete curculionid fossils have been described from Canada (Hylobiites), the USA (Curculionites), and Chile (Dorotheus), but should in general be reassessed according to Oberprieler et al. (2007).
A well-preserved specimen of Curculionidae from the Santana Formation is described here, as belonging to a new genus and species of the subfamily Curculioninae. This represents the first record of the family Curculionidae in the Araripe Basin and the oldest record of the subfamily Curculioninae.
Geological Setting and Palaeoenvironment of the Crato Formation
The Araripe Basin (Text-fig. 1) is situated in the interior of north-eastern Brazil. The basin extends into the states of Piauí, Pernambuco and Ceará, occupying an area of 8000 km2. It is located between 7°05′S, 38°30′W and 7°50′S, 40°50′W. This basin consists of Palaeozoic and Mesozoic sediments, forming one of the inland Mesozoic basins that originated at the time of the break-up of Gondwana and the initial opening of the South Atlantic Ocean (Ponte and Ponte Filho 1996; Dilcher et al. 2005).
The lithostratigraphy of sediments in the Araripe Basin has endured a long history of controversy, and several systems have been proposed (Beurlen 1971; Neumann and Cabrera 1999; Neumann et al. 2003; Martill et al. 2007; Assine 2007). According to the proposals of Neumann and Cabrera (1999) and Neumann et al. (2003), the Santana Group includes all sedimentary postrift sequences of the Araripe Basin, consisting of the Rio Batateira, Crato, Ipubi, Romualdo and Arajara Formations (Text-fig. 2). The Crato Formation consists of horizontal strata of thin laminated plate-like limestones with shales, siltstones, marls and lime–sandstone intercalations. The limestone crops out on the northern flank of the Chapada do Araripe, and the specimen described here was collected from a quarry near Nova Olinda, Ceará. This limestone was deposited under conditions of lacustrine flooding and terrigenous to carbonate sedimentation. Successions of six different lakes have been discovered, in which these limestones were deposited in shallow waters. The large palaeolake may have covered an area of 7500 km2 (50 × 150 km) (Neumann and Cabrera 1999; Neumann et al. 2003; Mohr and Bernardes-de-Oliveira 2004; Dilcher et al. 2005).
Neumann et al. (2003) suggested, based on palaeobotanical and palaeogeographic data, that the Crato lacustrine system evolved under a tropical–subtropical, warm palaeoclimatic regime, probably characterized by seasonal precipitation and alternating wet and dry cycles. The presence of abundant Classopollis pollen and members of Cheirolepidiaceae (Coniferales) in these sediments has been suggested as indicating a dry regional climate. Nevertheless, the palaeoenvironment suggested by Martill et al. (2007) is lagoonal, with stagnant, anoxic and hypersaline bottom waters. Based on palynomorphs and ostracods, Hashimoto et al. (1987), Arai et al. (1989, 2001) and Coimbra et al. (2002) considered that the Rio da Batateira and the Crato Formation belong to the lower Alagoas stage (Upper Aptian) (Text-fig. 2).
The fossil content of the Crato Formation comprises a large variety of insects (300 species, 100 families and 18 orders described), arachnids, crustaceans, molluscs and ichnofossils (made by invertebrates) (Grimaldi and Engel 2005; Martins Neto 2005). The most common vertebrates are fish (represented primarily by Dastilbe crandelli and Cladocyclus), anurans, turtles, crocodilians, lizards, feathers and pterosaurs. Plant material is common and includes pteridophytes, gymnosperms, angiosperms and their palynomorphs (Maisey 1991; Kellner and Tomida 2000; Dilcher et al. 2005). The Araripe Basin (Crato Formation), which is considered the largest and most diverse of about 25 known Gondwanan insect localities, preserves a diverse autochthonous fauna of aquatic insects, chiefly Ephemeroptera (adults and nymphs), some Odonata, Hemiptera and other terrestrial groups from nearby vegetated areas, such as Orthoptera, Hymenoptera (Grimaldi and Engel 2005), and a member of Belinae (Coleoptera, Curculionoidea, Belidae) that was probably associated with gymnosperms (Coniferales) (Santos et al. 2007).
Material and Methods
The fossil material is preserved three dimensionally, and mainly iron minerals replaced the original tissues.
Mechanical preparation, using various sizes of thin brushes (numbers 0 and 000), was employed to remove the matrix from around the fossil. Then, the specimen was studied under an optical binocular microscope and photographed with an EOS 350 D and macro 100-mm lens. Drawings were made with the aid of a drawing tube mounted on a MZ 7.5 stereomicroscope and measurements with a Moticam (1.3 MP) attached to a (K 400).
The measurements (in mm) of the specimen were made in lateral view. The acronyms for measurements used in the text are as follows: TL = total length, from the middle of the eyes to the elytral apex; HB = greatest height of the body at metathorax level; RL = length of the rostrum, from the rostral apex to the anterior margin of the eyes; MLO = maximum lateral width of the eye; and PL = prothorax length. The terminology used for adult structures primarily follows Lawrence and Britton (1994) and Santos et al. (2007).
Repository. The specimen (MN 8199-I) is housed in the insect collection of the Departamento de Geologia e Paleontologia of the Museu Nacional, Universidade Federal do Rio de Janeiro (MN/UFRJ).
INSECTA Linnaeus, 1758 Order COLEOPTERA Linnaeus, 1758 Suborder POLYPHAGA Emery, 1886 Superfamily CURCULIONOIDEA Latreille, 1802 Family CURCULIONIDAE Latreille, 1802 Subfamily CURCULIONINAE Latreille, 1802 Tribe? ANTHONOMINI C. G. Thomson, 1859
Genus ARARIPERHINUS gen. nov.
Derivation of name. The generic epithet combines Araripe and the Greek ‘rhinos’ meaning nose, snout and beak. Gender masculine.
Type and only species. Arariperhinus monnei sp. nov.
Diagnosis. One tubercle on the inner margin of each eye (Text-figs 3, 4); rostrum slightly longer than prothorax length; mesocoxae, metasternum and metepisternum with dense, moderately coarse punctures.
Remarks. The genus is placed in the subfamily Curculioninae by its strongly convex body and relatively slender rostrum, but mainly by its rounded eyes and lack of the prosternal sulcus and tibial spurs. Arariperhinus gen. nov. is placed in the tribe Anthonomini with some reservations, because it is impossible to observe characters of the claws (i.e. were they free and appendiculate), which are poorly preserved. Arariperhinus monnei has eyes that are very prominent in profile (eyes not prominent in Derelomini), the rostrum is cylindrical (variable in Derelomini), and the posterior margin of ventrite II is straight (curved at the sides in Tychiini).
Description. Body strongly convex and sclerotized, tiny and dark; height at metathorax level slightly more than 1/3 of total length. Cephalic capsule evidently spherical; surface finely and densely punctuate; interstice microsculptured; rounded eyes, maximum width (MLO = 0.23) subequal to 1/6 length of rostrum; frons with two stout and prominent tubercles on inner margin of eyes (Text-figs 3A, C, 4A, C), rounded on top and microsculptured; rostrum slender and as long as prothorax, evenly curved from base to apex; basal length (lateral view) subequal to maximum width of eye; probably with antennal insertion near apex; elongate and incomplete scape of antennae (probably in resting position); length of scape 1/3 of rostral length; antennae lacking pedicel, funicle and club. Prothorax (Text-figs 3A, 4A): slightly shorter than rostrum, and 2/3 length of elytron; sides of pronotum apparently as wide as elytra base; proepimeron as metasternum, with similar punctures; globose and prominent procoxae. Elytron (Text-figs 3A, D, 4A): strongly convex, moderately elongated, 3.6 times as long as prothorax; humeri feebly prominent, lacking end of epipleuron and somewhat rounded; dorsum (at least at base), with interstriae feebly prominent and striae with coarse punctures; elytral apex somewhat rounded; mesepimeron vertical, strongly narrowed to ventral sides; mesocoxae, metasternum, and metepisternum (Text-figs 3D, 4A, B) with dense, moderately coarse punctures; mesocoxae oblong, anteriorly impressed, little prominent, shallowly punctate; metasternum with anterior margin indistinct, moderately deep punctures, elevated interstice and granulate at sides; longitudinal disc strongly impressed; metepisternum elongate, longitudinally impressed with coarser and confluent punctures; metacoxae transverse and large, as wide as metasternum; lateral regions terminate beneath metepisternal apex, not reaching elytral margin. Abdomen (Text-figs 3A, D, 4A) with ventrite I slightly longer than II and apparently tuberculated and almost impressed near disc; surface of ventrites I and II with punctuate-corrugate aspect and with microsculptures; ventrite III shorter than II; ventrite IV slightly shorter than III; ventrite V and pygidium covered by elytral apex; femora and tibiae (Text-figs 3A, 4A) apparently unarmed; profemur apparently narrower and longer than meso- and metafemora; mesofemora microsculptured, lacking mesotibiae and metatarsus; metafemora impressed at inner side, apical half indicated and incomplete; metatibiae impressed at proximal half; apical half thickened apically; metatarsus I elongate, fragmented, with impression of claws.
Previous fossil records of Anthonomini are known only from the tertiary: Anthonomus Germar, 1817 (Miocene and Oligocene, Argentina and USA); Coccotorus Le Conte, 1876 (Miocene, USA) and Cremastorhynchus Scudder, 1893 (Miocene, USA). Consequently, A.monnei may be the oldest occurrence of the Anthonomini in the fossil record. Curculionoidea dominate in the Santana Group (10 specimens) (Zherikhin and Gratshev 2004). Arariperhinus monnei is the first record of the subfamily Curculioninae, representing the most derived lineage of the Curculionoidea, in the Santana Group. Anthonomini are often referred to as ‘flower weevils’, because their larvae develop predominantly in plant reproductive organs, such as flowers, fruits and seeds (Oberprieler et al. 2007). Furthermore, the presence of angiosperms becomes a noticeable part of the Earth’s vegetation during the Lower Cretaceous, including the Crato palaeoflora (Dilcher 2000; Bernardes-de-Oliveira et al. 2007). This suggests that A. monnei (Curculioninae) was probably associated with early flowering plants in the Crato Formation. The new curculionid specimen found in the Crato Formation reveals the importance of this fossiliferous deposit for insect–plant coevolution studies. This oldest record of a member of the Curculionidae (probably Anthonomini) supports the proposal that the Araripe Basin could have been one of the locations of early angiosperm diversification.
Additionally, an interaction with the group of more derived angiosperms in the Crato Formation may have occurred, although in the palaeoflora of the Araripe Basin, only monocotyledons are recorded (Bernardes-de-Oliveira et al. 2006). On the other hand, a fossil of a flowering plant Endressinia brasiliana of the Magnolialean group was found. According to phylogenetic studies, its members are apparently more derived than those belonging to the grade Choranthaceae (Mohr and Bernardes-de-Oliveira 2004). At the end of the Cretaceous in the Southern Hemisphere, the floras of lower latitudes exhibit a high diversity of flowering plants, as opposed to the higher latitudes (Mohr and Bernardes-de-Oliveira 2004). The angiosperms constitute a small but significant part of the flora of the Crato Formation, i.e. three to five per cent of the total number of fossil plants, while the number of angiosperm taxa may be up to 25 per cent of the total taxonomic diversity (Mohr and Friis 2000). Palaeogeographic studies suggest that the earliest lineages of angiosperms arose in the arid belt of the planet, where the Crato Formation is located (Equatorial Arid province) (Dilcher 2000; Bernardes-de-Oliveira et al. 2006).
Acknowledgements. The authors thank Dr Sergio A. Vanin (Museu de Zoologia da Universidade de São Paulo) and Dr Paulo M. Brito (Universidade do Estado do Rio de Janeiro) for their thoughts and suggestions, Helder de Paula Silva (MN/UFRJ) for his assistance in preparation of the fossil and Clayton Portela for the final illustration.