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Cretorabus rasnitsyni sp. n., belonging to the extinct subfamily Protorabinae of Carabidae, was described based on a well-preserved specimen from the Lower Cretaceous Yixian Formation of Yangshuwanzi, Inner Mongolia. The diagnostic characters forCretorabus are revised, and the key to species of the genus was presented. The fossil record of Protorabinae was summarized. Sinocarabus Hong, 1982 and Obesofemoria Hong, 1982 cannot be attributed to Protorabinae.
Protorabinae, Coleoptera, Lower Cretaceous, Inner Mongolia, China
Protorabinae is an extinct subfamily of Carabidae, and differs remarkably from all other carabid beetles in that the metepisterna are extending to the mesocoxal cavities (
The specimen (NIGP152464) was from the Lower Cretaceous Yixian Formation of Yangshuwanzi Village, Bisiyingzi Township, Ningcheng County, Chifeng City, Inner Mongolia. The fossils from Yangshuwanzi are commonly preserved in yellow silty mudstone. The horizon in this locality is equivalent to either the Jianshangou or Dawangzhangzi bed (about 124–122 Ma) of the Yixian Formation (
The specimen was examined dry and under alcohol, using a Nikon SMZ1000 stereomicroscope and drawings were made with the aid of a camera lucida. The photographs were prepared using a digital camera (DXM1200) connected to the above stereomicroscope, and the line drawings were readjusted on photographs using image-editing software (CorelDRAW X4 and Adobe Photoshop CS). In drawings, the broken lines denote the hidden and presumably missing body parts. Body length was measured along the midline from the anterior margin of frons to apex of elytra, and width was measured across the broadest part of elytra. The length of pronotum was measured along the midline; the width was measured across the broadest part of pronotum.
Systematic PaleontologyFamily Carabidae Latreille, 1802
Subfamily Protorabinae Ponomarenko, 1977
Cretorabus capitatus Ponomarenko, 1977; by original designation.
Zaza Formation, Lower Cretaceous; Baissa, Buryatiya, Russia.
Body wide, small or medium-sized. Head large, strongly transverse. Pronotum transverse, widest in anterior or middle portion, constricted behind middle. Mesoventrite longer than mesocoxae. Metepisterna posteriorly tapering. Metacoxal plates tapering strongly in lateral half, extending as a narrow tongue up to lateral margins of metacoxae. Abdomen short, with rounded apex; last ventrite long, its anterior margin two-thirds narrower than base of abdomen. Legs short, femora slightly extending beyond body sides. Elytra smooth or with numerous rows of large punctures.
The genus is different from other genera in the metacoxal plates tapering strongly in lateral half, extending as a narrow tongue up to the lateral margins of metacoxae. Furthermore, it differs from Cordorabus Ponomarenko, 1977 in having the mesoventrite longer than mesocoxae, and abdomen short, with apex rounded; from Ovrabites Ponomarenko, 1977 in possessing the pronotum constricted behind middle, abdomen short, with apex rounded; from Protorabus Ponomarenko, 1977 by the last ventrite much narrower than base of abdomen, and elytra with grooves; from Lithorabus Ponomarenko, 1977 in having the metepisterna posteriorly tapering; from Nebrorabus Ponomarenko, 1989 in possessing the wider body and shorter legs.
Six species: Cretorabus capitatus Ponomarenko, 1977 and Cretorabus latus Ponomarenko, 1977 from the Lower Cretaceous of Baissa; Cretorabus orientalis Ponomarenko, 1989 from the Lower Cretaceous of Khutel Khara of Mongolia; Cretorabus ovalis Ponomarenko, 1989 from the Lower Cretaceous of Bon-Tsagan of Mongolia; Cretorabus sulcatus Ponomarenko, Coram & Jarzembowski, 2005 from the Lower Cretaceous Purbeck Limestone Group of England; and Cretorabus rasnitsyni sp. n. from the Lower Cretaceous Yixian Formation of Inner Mongolia of China.
| 1 | Body small or medium-sized (length < 10 mm) | 3 |
| – | Body large ( > 13 mm) | 2 |
| 2 | Metacoxae 1.8 times as wide as long | Cretorabus latus Ponomarenko, 1977 |
| – | Metacoxae 2.5 times as wide as long | Cretorabus ovalis Ponomarenko, 1989 |
| 3 | Body small (length 3.7 mm); elytra with punctate furrows | Cretorabus sulcatus Ponomarenko, Coram & Jarzembowski, 2005 |
| – | Body medium-sized; elytra smooth | 4 |
| 4 | Prosternal process narrow, 0.4 times as wide as procoxae, slightly longer than procoxae; metacoxae 1.5 times as wide as long | Cretorabus capitatus Ponomarenko, 1977 |
| – | Prosternal process almost as wide as procoxae, much longer than procoxae; metacoxae 2.5 times as wide as long | 5 |
| 5 | Metaventrite twice as wide as long; metacoxal plates with emargination in lateral part of posterior margin | Cretorabus orientalis Ponomarenko, 1989 |
| – | Metaventrite 3 times as wide as long; metacoxal plates with lateral part of posterior margin not emarginate | Cretorabus rasnitsyni sp. n. |
urn:lsid:zoobank.org:act:4416C789-0065-4CCC-9279-5F1419A1D481
http://species-id.net/wiki/Cretorabus_rasnitsyni
Figs 1 –5NIGP152464, male, a well-preserved beetle in ventral aspect. Yixian Formation, Lower Cretaceous; a fossil locality (41°25'N, 118°57'E) near Yangshuwanzi Village, Bisiyingzi Township, Ningcheng County, Chifeng City, Inner Mongolia, China. Deposited in the Nanjing Institute of Geology and Palaeontology (NIGP), Chinese Academy of Sciences.
Body medium-sized. Pronotum 1.8 times as wide as long. Prosternal process almost as wide as procoxae, much longer than procoxae. Metaventrite 3 times as wide as long. Metacoxae 1.8 times as wide as long. Metacoxal plates with lateral part of posterior margin not emarginate.
Head and pronotum strongly transverse. Length of head (including mandibles) slightly shorter than occiput width. Head capsule narrowing anteriorly from base. Eyes shorter than temples. Gular plate 1.5 times as long as wide, widened anteriorly. Antennae inserted at anterior margin of eyes; scape dilated; pedicellum slightly shorter than scape; first flagellomere slightly longer than scape. Mandibles large, slightly incurved, asymmetrical, with retinaculum small. Maxillary palps 4-segmented, conspicuously longer than mandibles; palpomere 4 with apical margin subtruncate.
Cretorabus rasnitsyni sp. n., photomicrograph of holotype NIGP152464 1 dry 2 under alcohol. Scale bar represents 1 mm.
Pronotum 1.8 times as wide as long, widest nearly in the middle; pronotal angles pointed, concealing the base of head dorsally. Propleura narrow. Prosternum before procoxae 1.4 times longer than procoxae. Prosternal process wide, 1.4 times as long as procoxae. Mesoventrite transverse, with subtriangular depression for reception of prosternal process. Mesepisternum almost rectangular, transverse. Mesepimeron short, extending to mesocoxal cavities, slightly widened laterally. Metaventrite short, 3 times as wide as long; its anterior margin half as long as the posterior. Metepisterna subtriangular, gradually widened anteriorly, its length 1.5 times width at anterior margin. Metacoxae oblique, slightly projecting over abdomen, 3 times as wide as long. Metacoxal plates slightly longer than coxae. Abdomen a little longer than meso- and metathorax combined, widened from base to apex of second visible sternite, then narrowing. Parameres rather long, with penis slightly projecting.
Profemur and protibia widened apically, almost equal in length. Tarsal segments widened apically; tarsomeres 1 almost as long as tarsomeres 2; tarsomeres 2 slightly longer than tarsomeres 3. Mesofemur and mesotibia almost equal in length. Mesotibia widened apically, 1.2 times as long as protibia. Metatrochanters one-third as long as metafemora. Metatibiae 1.1 times as long as metafemora, slightly widened apically; its outer side possibly with pits.
Cretorabus rasnitsyni sp. n., drawings of holotype NIGP152464 3 without legs 4 with legs.
Cretorabus rasnitsyni sp. n., drawing of mouthparts of holotype NIGP152464.
Body length 7.8 mm, width 4.0 mm. Head length (including mandibles) 1.9 mm, occiput width 2.6 mm; mandible length 0.8 mm. Pronotum: length 1.8 mm, maximal width 3.2 mm. Abdomen: length 3.3 mm. Fore legs: femur length 1.5 mm; tibia length 1.5 mm. Middle legs: femur length 1.7 mm; tibia length 1.7 mm. Hind legs: femur length 2.0 mm; tibia length 2.3 mm.
Specific epithet is devoted to Alexander P. Rasnitsyn, an outstanding Russian palaeoentomologist.
This specimens can be undoubtedly attributed to Cretorabus by the following characters: the pronotum constricted behind middle; mesoventrite longer than mesocoxae; metacoxal plates tapering strongly in lateral half, extending as a narrow tongue up to the lateral margins of metacoxae; and abdomen short, with rounded apex. The species mostly resemblesCretorabus orientalis in having the prosternal process much longer than procoxae, and metacoxae 2.5 times as wide as long, but differs from the latter in possessing the metacoxal plates with the lateral part of the margin not emarginate. Furthermore, it is different from Cretorabus capitatus in having the comparatively wider prosternal process and metacoxae.
Fossil record of Protorabinae.
| Taxon | Occurrence |
|---|---|
| Lithorabus incertus Ponomarenko, 1977 | Lower Jurassic of Issyk-Kul, Kirghizia |
| Protorabus planus Ponomarenko, 1977 | Upper Jurassic of Karatau, Kazakhstan |
| Protorabus magnus Ponomarenko, 1977 | Upper Jurassic of Karatau, Kazakhstan |
| Protorabus nigrimonticola Ponomarenko, 1977 | Upper Jurassic of Karatau, Kazakhstan |
| Protorabus kobdoensis Ponomarenko, 1986 | Lower Cretaceous of Myangad, Mongolia |
| Protorabus crassus Ponomarenko, 1989 | Lower Cretaceous of Shiviya, Transbaikalia |
| Protorabus tsaganensis Ponomarenko, 1989 | Lower Cretaceous of Bon-Tsagan, Mongolia |
| Ovrabites ovalis Ponomarenko, 1977 | Upper Jurassic of Karatau, Kazakhstan |
| Ovrabites jurassicus Ponomarenko, 1977 | Upper Jurassic of Karatau, Kazakhstan |
| Ovrabites incertus Ponomarenko, 1993 | Lower Cretaceous of Khetana, Russian Far East |
| Cordorabus notatus Ponomarenko, 1977 | Upper Jurassic of Karatau, Kazakhstan |
| Cretorabus antennatus Ponomarenko, 1977 | Upper Jurassic of Karatau, Kazakhstan |
| Cretorabus minimus Ponomarenko, 1977 | Upper Jurassic of Karatau, Kazakhstan |
| Cretorabus vittatus Ponomarenko, 1980 | Lower Cretaceous of Manlay, Mongolia |
| Cretorabus striatus Ponomarenko, 1986 | Lower Cretaceous of Gurban-Ereney, Mongolia |
| Cretorabus capitatus Ponomarenko, 1977 | Lower Cretaceous of Baissa, Transbaikalia |
| Cretorabus latus Ponomarenko, 1977 | Lower Cretaceous of Baissa, Transbaikalia |
| Cretorabus orientalis Ponomarenko, 1989 | Lower Cretaceous of Khutel Khara, Mongolia |
| Cretorabus ovalis Ponomarenko, 1989 | Lower Cretaceous of Bon-Tsagan, Mongolia |
| Cretorabus sulcatus Ponomarenko, Coram & Jarzembowski, 2005 | Lower Cretaceous of Dorset, England |
| Cretorabus rasnitsyni sp. n. | Lower Cretaceous of Inner Mongolia, China |
| Nebrorabus baculum Ponomarenko, 1989 | Lower Cretaceous of Chernyshevsk, Transbaikalia |
| Nebrorabus capitatus Ponomarenko, 1989 | Lower Cretaceous of Baley, Transbaikalia |
| Nebrorabus nebrioides Ponomarenko, 1989 | Lower Cretaceous of Bon-Tsagan, Mongolia |
| Nebrorabus ?elongatus (Ponomarenko, 1986) | Lower Cretaceous of Myangad, Mongolia |
| Nebrorabus tumoculus (Ren, 1995) | Lower Cretaceous of Lushangfen, China |
| Aethocarabus levigata Ren, 1995 | Lower Cretaceous of Lushangfen, China |
| Penecupes rapax Ren, 1995 | Lower Cretaceous of Lushangfen, China |
BW thanks to the staff members of the palaeoentomological laboratory of the Palaeontological Institute (Russian Academy of Sciences) for their help during his visit in Moscow (2010). Many thanks go to Alexander Ponomarenko and Alexander Kirejtshuk for reviewing the manuscript and providing constructive suggestions, Lin Jih-Pai for checking English language of the manuscript, and Dmitry Shcherbakov for his helpful editorial comments. This research was supported by the National Natural Science Foundation of China (Grant Nos. 40872015, 41002006, J0930006), Major Basic Research Program of China (Grant No. 2006CB806400).