Sinodrepanus schoenfeldi, Montanaro, 2024

Montanaro, Giulio, 2024, New or poorly known species of Sinodrepanus Simonis, 1985 (Coleoptera: Scarabaeidae: Oniticellini), with the first identification key for the genus, Zootaxa 5537 (4), pp. 577-595 : 590-591

Indian Sinodrepanus : an overlooked diversity?

Due to their morphological similarity, Sinodrepanus exsul ( Sharp, 1875) , S. falsus ( Sharp, 1875) and S. schoenfeldi new species have been largely mixed up by previous authors, leading to an intricate and not yet resolved distributional and taxonomic history. This section deals mainly with distribution of the three species, with a special focus on Indian records.

Sinodrepanus falsus and S. exsul were described by Sharp (1875) in the genus Oniticellus , from Laos and Thailand, respectively. Subsequently, Arrow (1931) moved Oniticellus exsul to Drepanocerus and recorded as such the specimen from India (Assam) which is now the holotype of S. schoenfeldi new species. Later, Janssens (1953: 37) erroneously synonymized Drepanocerus exsul with Drepanocerus falsus , and added a new record from Laos (Paklay) which was later attributed to the true S. falsus by Montanaro (2021). Balthasar (1963) reported the same distributional data as Janssens (1953). Biswas & Chatterjee (1985) recorded D. falsus from the Indian state of Arunachal Pradesh (Namdapha, Hornbill, human faeces, 15.iv.1981, S. Biswas legit 3 specimens). Kabakov & Napolov (1999) recorded S. falsus from Vietnam, listing S. excul [sic!] as a synonym. Notably, the Russian authors also mentioned a putatively new Vietnamese species and another unidentified one, whose identity—as far as I know—was never assessed. Sewak (2003) reported D. falsus from Assam and Arunachal Pradesh, probably following previous works. Judging from his bibliography, Sewak (2003) was not aware of the synonymy established by Janssens (1953) and continued to consider the two species as separate. It is not clear, though, why he listed D. exsul under the synonyms of D. falsus —perhaps following acritically Biswas & Chatterjee (1985). Also, Sewak (2003) overlooked the paper in which Simonis (1985) described the genus Sinodrepanus for Drepanocerus falsus and allies. For this reason, he kept using the old genus name, Drepanocerus , also in subsequent works ( Sewak 2004, 2006, 2009a, 2009b, 2009c). In any case, Sewak (2003) cited also D. exsul from Assam and added two new Indian records: Meghalaya and—on the opposite side of the country— Gujarat states. Subsequently, Sewak (2004) provided more precise Gujarat localities: Jamnagar (Kalavad, 8.iii.1986), Surendranagar (Chotila, 13.iii.1986) and Junagarh (Gir forest, 13.viii.1988; R.N. Bhargava, Trapas, 11.ix.1990). Sewak (2006) cited D. falsus again from Assam and provided a more precise locality from Arunachal Pradesh (Tawang, Namet village, 23.ix.1997, R. Sewak legit 2 exs.). In the same paper, the author listed D. exsul as a synonym of S. falsus . Later, Sewak (2009a, 2009b, 2009c) added other records of D. exsul from western India: again Gujarat (Junagarh, Patan, Porbander, Rajkot, Surendranagar), and Rajasthan. Afterwards, Kabakov & Shokhin (2014) recorded for the first time S. falsus from China (Sichuan). In their checklist of Indian dung beetles, Mittal & Jain (2015) cited Sinodrepanus falsus from Alwar and Sawaimadhopur (Rajasthan)—perhaps taking the data from other published sources, which in such case I was unable to find. Mittal & Jain (2015) probably (yet not explicitly) considered S. exsul a mere synonym of S. falsus , given they quoted under the latter species Gujarat localities ascribed in literature to S. exsul . Lastly, Montanaro (2021) confirmed that S. falsus and S. exsul are definitely distinct species and verified some records from China, Laos and Thailand.

Disentangling in detail this mixture of distributional information and taxonomic misunderstandings is hard. While some of these records have been checked, one intriguing question remains: how many species of Sinodrepanus are there in India? What seems clear is that Sewak, judging from his work ( Sewak 2003, 2006, 2004, 2009a, 2009b, 2009c), recognized two separate species. Indeed, he personally collected “ S. falsus ” at least in Arunachal Pradesh and “ S. exsul ” in Gujarat. Now, it is likely that the records from Arunachal Pradesh and Assam (including that by Biswas & Chatterjee (1985)), have to be referred to S. schoenfeldi new species, whose type series includes specimens collected exactly in that region of northeastern India, on the foothills of Himalaya (see Fig. 4). On the other hand, the records from western India (Gujarat and Rajasthan) seem quite far away from the known range of S. falsus , S. exsul and S. schoenfeldi new species ( Fig. 4). Most importantly, Gujarat and Rajasthan are extensively covered by arid or semi-arid ecosystems that differ significantly from the much more humid ecosystems of northeastern India and Southeast Asia in which the three abovementioned species are found ( Singh & Chaturvedi 2017). Therefore, it would not be surprising to discover that the specimens from western India represent, in fact, an undescribed taxon. I was unable to find any specimen from that area, therefore the enigma is postponed to when somebody will be able to examine some relevant material. Lastly, the record from Meghalaya ( Sewak 2003) is rather obscure. Sewak identified it as “ S. exsul ”, like the specimens he found in Gujarat, albeit the two Indian states are very far away, with Meghalaya being much closer to the type locality of S. schoenfeldi new species.