4 Discussion.
The Paederinae is one of the most challenging subfamilies to study (Żyła et al. 2021). However, Bogri et al. 2020 and Żyła et al. 2019, 2021 have made considerable progress in creating a comprehensive, well-supported phylogenetic framework for this hyper-diverse group. The species (Afrinophilina orapa species. nov., Figs. 2, 3, 4 and 7) described in this study has antennae that are concealed under the “shelf”, and a hypomeron with a post-coxal process, which are both diagnostic features for this group (Herman 2010, Bogri et al. 2020, and Żyła et al. 2019, 2021). Unfortunately, the characters which are generally used to separate Paederinae tribes, in particular the maxillary palps, are poorly preserved on the fossil. Therefore, this hinders an accurate and reliable interpretation of the mouthparts.
The specimen has its first pro-tarsal segment (also known as protibial combs) dilated with a setiferous margin as for the Pinophilini (Herman 2010). However, it is seemingly not as dilated in comparison to the examined extant pinophilines housed at the Ditsong National Museum of Natural History (DNMNH) (Pretoria, South Africa). It would be useful to have the rest of the tarsus preserved, because there are other genera assigned to other tribes, for example, Scymbalium Erichson, 1839 and Micrillis Raffray, 1873, that have similar features (Bogri et al. 2020). Other characters which may be important in assisting to place this specimen among the Pinophilini are the elongate procoxae, which are as long as the profemora (Campbell and Peck 1989; Herman 2010; and Shaw et al. 2020); broad, oval, fully exposed trochantin, and presence of a conspicuous second abdominal segment (Campbell and Peck 1989).
The new species is placed in the Pinophilina, rather than the Procirrina, based on the presence of well-preserved pair of paratergites on segments III-VIII (Campbell and Peck 1989; Herman 2010; and Shaw et al. 2020). Characters which may distinguish this new species from all the other Pinophilina is the lack of an emarginate shape of the rear margins of the elytra, broad neck and having two pairs of paratergites on each side of segments III-VI (Herman 2010). It is also interesting to note, however, that two recent matrices of morphological characters (i.e., Bogri et al. 2020; and Żyła et al. 2021), do not include characters like extended procoxae, and fully exposed protrachantin. It is possible that these characters are not useful for distinguishing amongst other tribes of the Paederinae. However, it is equally probable that the characters could be widely variable among the Paederinae genera. The reason behind this is unclear at the moment, and needs further investigation.
The earliest Paederinae are described from the Yixian Formation of China, and were initially assigned as ‘incertae sedis ’ to the genus Mesostaphylinus (Chatzimanolis 2018). These have since been described as M. antiquus , M. elongatus , and M. yixianus Solodovnikov et al., 2013 (Solodovnikov et al. 2013). There are also several described Mesozoic Paederinae such as Apticax solidus and Apticax volans Schomann and Solodovnikov, 2012 known from the Santana/Crato Formation of Brazil (122.46-112.6 Ma) (Chatzimanolis 2018). Many species of Paederinae are described from Cenozoic deposits such as the Florissant Formation of the United States of America, and the Baltic amber of Russia and many other countries, and it is thought that the majority of these have been incorrectly assigned to the genus Lathrobium Gravenhorst, 1802 (Chatzimanolis 2018).
Furthermore, there are other notable Cenozoic taxa belonging to the above-mentioned genus, such as Lathrobium provinciale Goss, 1878 that has been formally described from the Aix-en-Provence of France (11.6-7.2 Ma), and several Lathrobium spp. from Shanwang of China (Chatzimanolis 2018). According to Betz et al. (2018), there are taxa that continue to await description from Burmese amber of Myanmar, Green River Formation of the United States of America, and Kishenehn Formation of the United Stated of America.
Despite studies by Schomann and Solodovnikov (2017); Żyła et al. (2019, 2021); Bogri et al. (2020); and Shaw et al. (2020), more research is still required regarding the classification and phylogeny of Paederinae, before new descriptions can be reliably assigned to existing tribes, subtribes and genera of the subfamily. For example, the genusApticax proposed by Schomann and Solodovnikov, 2012 was formally described from the Santana/Crato Formation, and it was assigned to the Paederinae + Staphylininae lineage; whereas more phylogenetic analysis by Solodovnikov et al. (2013) argued that the genus is missing some of its key features, and could therefore, not be assigned with confidence to any subfamily of the Staphylinidae. A reclassification is required, especially after the latest hypothesis by Cai et al. (2021) that downgraded the Silphidae to a subfamily level within the Staphylinidae.
During the Cretaceous, the Paederinae were found in widely distributed localities (Fig. 8), suggesting a much earlier, common point of origin. They were distributed in several countries, including Brazil, China, Myanmar and Botswana. Finding a paederine fossil at Orapa Diamond Mine in Botswana is not surprising, given that Schomann and Solodovnikov (2012) suggested that the genus Apticax , from the Lower Cretaceous Santana/Crato Formation of Brazil, is possibly, if not conclusively, a paederine. In addition, Solodovnikov et al. (2013) described the genus Mesostaphylinus from the Lower Cretaceous, Yixian Formation of China as “Paederinae, incertae sedis ”. These were later described as M. elongatus , M. yixianus , and M. antiquus .
In addition, there is also M. laiyangensis Zhang, 1988 from Laiyang Formation of China. Solodovnikov et al. (2013) pronounced that the discovery of the Paederinae and Staphylininae linage from the Lower Cretaceous Yixian Formation sets the split between these groups back to the Jurassic. Interestingly, Mesostaphylinus Solodovnikov et al., 2013 shares three characters with Afrinophilina , in a form of an extended procoxae, well-developed segment II of the abdomen, and seemingly dilated protibial combs.
Afrinophilina resembles the Pinophilina based on the shape of the antennae and arrangement of the setae on the protarsi. Perhaps it would be worth reanalysing Mesostaphylinus for affinities with Pinophilina. Shaw et al. (2020) have recently described the first fossil Procirrina, Cretoprocirrus trichotos , from the Burmese amber of Myanmar, and it is therefore to be expected that the sister group of this taxon would have appeared around this time. Afrinophilina orapa is therefore the first fossil paederine belonging to the subtribe Pinophilina from the Cretaceous. It is the first fossil Paederinae from Africa, the second from the Southern Hemisphere. Similarly to other fossil staphylinids that have been described in the past, the new species demonstrates morphological conservatism dating back to the Cretaceous.