1 Introduction.
The Paederinae is one of the hyper-diverse subfamilies of the
Staphylinidae with 225 (1 extinct) genera, and approximately 7 584 (35
extinct) species (Bogri et al. 2020). This subfamily remains largely
unexplored, both phylogenetically and taxonomically (Schomann and
Solodovnikov 2017), and is known as one of the most challenging
subfamilies to study (Żyła et al. 2021). This is due to the shortage of
phylogenies undertaken. In addition, its phylogeny-based tribal and
sub-tribal classification schemes still need an extensive revision,
while many genera await proper delimitation (Bogri et al. 2020). The
challenge is exacerbated by its high species richness, diversity and
abundance, and having few experts studying this group (Żyła et al.
2021). Recently, more researchers are studying the subfamilies of the
Staphylinidae.
The Paederinae was divided into four tribes, namely: Pinophilini,
Paederini, Cylindroxystini and Lathrobiini (Schomann and Solodovnikov
2017). Recently, Żyła et al. (2021) conducted the most comprehensive
phylogenetic analysis of the Paederinae, based on multiple genetic loci,
incorporating the broadest sampling of the taxa. The study reduced the
Paederinae into three monophyletic tribes, namely the Pinophilini and
Paederini which are sister groups of one another, and which together are
the sister group of the Lathrobiini. In the study, the Cylindroxystini
were subsequently demoted to a group within the Lathrobiini (Żyła et al.
2021). Furthermore, according to Żyła et al. (2021), the sister clades
of the Paederinae are either the Euasthetinae or Staphylininae. However,
most phylogenetic studies (e.g., Grebennikov and Newton 2009;
Solodovnikov et al. 2013; and McKenna et al. 2015) found that the
Paederinae and Staphylininae are sister groups. Surprisingly, the
relationship between Paederinae and Staphylininae only found weak
support in a recent study by Lü et al. (2020).
The split between Paederinae and Staphylininae is estimated to have
occurred during the Late Jurassic (156.6 Ma), using mitogenomic
sequencing (Hernando and Andujar 2021). More recently, this notion has
been supported by Lü et al. (2020), who analysed four nuclear and two
mitochondrial gene sequences, and estimated that the two subfamilies
originated between 147.58 and 160.41 million years ago, respectively.
The Mesozoic fossil record of the
Paederinae is restricted to the Cretaceous (Table 1). So far, none have
been recorded between the Triassic and Jurassic ages. Schomann and
Solodovnikov (2012) assigned the genus Apticax and A.
solidus from the Nova Olinda Member of the Crato/Santana Formation in
north-eastern Brazil to the Staphylininae + Paederinae lineage, but
disclosed that the small number of diagnostic features do not allow for
a definite placement in any of the 33 subfamilies of the Staphylinidae.
Solodovnikov et al. (2013) described Mesostaphylinus elongatus ,M. yixianus , and M. antiquus from the Early Cretaceous
deposit, Yixian Formation of China, based on phylogenetic analysis of
both extinct and extant taxa. These were placed “incertae
sedis ” within the Paederinae, due to lack of diagnostic features. Żyła
et al. (2019) described two inclusions from the Cretaceous Burmese amber
of Myanmar, Diminudon schomannae and D. kachinensis(Lathrobiini), by a combination of morphological and molecular datasets.
Shaw et al. (2020) described the earliest record of the Pinophilini,Cretoprocirrus trichotos from Burmese amber of Myanmar. Bogri et
al. (2018) described Dysanabatium kechrimparense , D.
aenaum , D. damgaardi , and D. johannesi from the Baltic
amber of Russia, to address a connection between co-occurrence of
thermophilic and temperate insect taxa and Eocene climate change. In
addition, Bogri et al. (2020) described Micrillus electrus andScymbalium phaethoni from the Baltic amber of Russia, based on
diagnostic morphological character matrices of both genera.
In total, the fossil record of the Paederinae encompasses 40 species
from 12 genera: Achenium Curtis 1826, Apticax Schomann and
Solodovnikov 2012, Cretoprocirrus Shaw et al. 2020,Diminudon Żyła et al. 2019, Dysanabatium Bernhauer 1915,Lathrobium Gravenhorst 1802, Lithocharis Dejean 1833,Miolithocharis Wickham 1913, Medon Stephens 1833,Mesostaphylinus Zhang 1988, Orsunius Assing 2011 andPaederus Lin et al. 2018; ranging from Cretaceous to Miocene.
This summary is given by Żyła et al. (2019), with an addition ofCretoprocirrus (Shaw et al. 2020). Notably, all the Cenozoic
fossils have been assigned to the tribe Lathrobiini (Żyła et al. 2019).
Table 1: Species list of the Paederinae (Coleoptera:
Staphylinidae). Updated from Żyła et al. (2019).