﻿Taxonomic revision of the genus Phylacastus Fairmaire (Tenebrionidae, Eurynotina): shortfalls of anatomical nomenclature with notes on aedeagal homology

﻿Abstract The genus Phylacastus Fairmaire (Tenebrionidae, Blaptinae, Platynotini, Eurynotina) is revised. Two new species and one new synonymy are presented along with new diagnoses, descriptions, a distribution map, and key to species. The resulting species of Phylacastus are: P.ancoraliumsp. nov., P.crypticoides Koch (= P.pretoriensis Koch syn. nov.), P.makskacymirowisp. nov., P.rhodesianus Koch, and P.striolatus Fairmaire. Lectotypes are designated for the type species, P.striolatus, to fix the taxonomic status of the species and genus. As a result of examination and subsequent description of P.ancoraliumsp. nov., a brief review and treatment of aedeagal morphology is presented. The nomenclature (“clavae” versus “laciniae”) and phylogenetic occurrence of accessory structures of the paramere-median lobe area within Blaptinae Leach and Adelinina LeConte (Diaperinae, Diaperini) are discussed. New descriptive terminology (i.e., ancora [singular] and ancorae [plural]) is proposed for these aedeagal structures in Blaptinae to clarify their function and resolve past ambiguities. The morphology within representatives of Adelina Dejean, Alphitophagus Stephens, Gnatocerus Thunberg, and Sitophagus Mulsant is also briefly contrasted and outlined.


Introduction
Eurynotina Mulsant & Rey is a subtribe of darkling beetles from Southern Africa within the tribe Platynotini Mulsant & Rey and subfamily Blaptinae Leach (Koch 1954a;Bouchard et al. 2021;Kamiński et al. 2021a). Platynotini are distinguished via the presence of a stridulatory file on the gula (synapomorphy for the tribe; see Koch 1954aKoch , b, 1956. Eurynotina are further diagnosable via their aedeagi, which lack additional "styles", "clavae", or "lacinia" (Antoine 1930;Koch 1954a, b;Lindroth and Palmen 1956) and have a strongly sclerotized medial lobe with reduced basal apophyses (Iwan 2001). Eurynotina has been supported as molecularly distinct by Kamiński et al. (2019Kamiński et al. ( , 2021a; however, the taxa included were not fully sufficient to test the monophyly of the group. This paper is the first of a series dedicated to revising subtribe Eurynotina as a part of the first author's Ph.D. dissertation. Platynotini has received attention from many generations of entomologists (Fairmaire 1897;Gebien 1904Gebien , 1910Reichardt 1936;Español 1945;Koch 1956Koch , 1958Kaszab 1975;Iwan 1995Iwan , 2002Iwan , 2006Endrödy-Younga 2000;Kamiński and Raś 2011;Kamiński 2012, 2014;Kamiński 2013Kamiński , 2015a; however, most contributions concern the subtribe Platynotina Mulsant & Rey. Only a handful of papers concern Eurynotina (Koch 1954a(Koch , b, 1955(Koch , 1956Kamiński 2016). For example, Phylacastus was erected in Opatrini Brullé by Fairmaire (1897) with a single new species (P. striolatus Fairmaire) and remained unstudied for nearly 60 years. In 1954a, Koch described three additional species and assigned the genus to his recently installed subtribe Oncotina Koch, now interpreted as a synonym of Eurynotina (see Kamiński 2016). He hypothesized a relationship between Phylacastus and Eurynotus Kirby through the following characters: horizontally produced prosternal apophysis, median emargination of epistoma, sharp and rectangular posterior angles of pronotum, and closely jointed prothorax and mesothorax. Prior to the study presented here, the only count of Phylacastus specimens was provided by Koch's (1954a) work (34 specimens, 25 of which belonged to one of his new species P. pretoriensis, and two syntypes of P. striolatus).
After queries to several entomological collections (see list in Materials and Methods) we identified new specimens and species of the genus. These materials provided the opportunity to test the taxonomic concepts of Phylacastus and its species. Furthermore, as one of the newly discovered species challenges Koch's (1954a, b) subtribal definition of Eurynotina, male terminalia morphology within subfamily Blaptinae is discussed based on dissected specimens, alongside previous literature (e.g. Koch 1956;Iwan 2001Iwan , 2004. Consequently, new terminology is proposed in light of previous application of the terms "clavae" and "laciniae" in the context of their meaning and priority within Blaptinae. They are also briefly contrasted with representatives of Diaperinae Latreille to better describe function, homology, and resolve some ambiguities.

Revision of genus Phylacastus
Pinned material for morphological examination of Phylacastus and other taxa was borrowed from the following institutional insect collections: MNHN -Muséum national d'Histoire naturelle; Paris, France; and TMNH -Ditsong National Museum of Natural History; Pretoria, South Africa. Additional comparative material for redefining the genus and investigating aedeagal morphology was obtained from: MIIZPAN -Muzeum i Instytut Zoologii, Polska Akademia Nauk; Warsaw, Poland; SANC -South African National Collection of Insects; Pretoria, South Africa. While specimens of Eurynotina are relatively uncommon, the holdings of the aforementioned collections are the most comprehensive for the subtribe, accounting for both the majority of type material, and additional specimens for examination. As a result of specimen loans and contact with collections presented here, all 16 genera and over 90% of the species of Eurynotina are represented by type material and photographs for reference for this project and continued revision of the subtribe.
Original label data for specimens are given in quotation marks and separated by a comma. Morphological terminology follows that of Matthews at al. (2010), with additional specialized terms used for the female terminalia following Kamiński et al. (2022). Dissections were performed following methodology illustrated by Kamiński (2021); specimens were soaked in 10% KOH solution for dissection of genitalia before staining with chlorazol black. Images were taken using a Canon 1000D body with extension rings and a Canon EF 100 mm macro lens, a Nikon D3500 body with adapter for a Nikon SMZ800N microscope, and with a Hitachi S-3400N SEM in MIZ PAS. A species distribution map was produced using QGIS v. 3.16, with vector layers downloaded from the Natural Earth web page (www.naturalearthdata.com). Photographs as well as distribution map figures were edited in Photoshop v. 23.5.1. A table of all localities is presented in Appendix 1.

Male terminalia analysis
Revelation of new structures on the aedeagus of Phylacastus ancoralium sp. nov. necessitated a review of aedeagal morphology to confirm its affiliation. To this end, we performed a historical literature review, and assessed aedeagal terminology and morphology (Antoine 1930;Español 1945;Koch 1954a, b;Lindroth and Palmen 1956;Doyen and Tschinkel 1982;Doyen 1984;Iwan 2001Iwan , 2004Kamiński 2014Kamiński , 2015b. Taxon selection mainly focused on Blaptinae, as various subgroups have historically been defined by the presence or absence of additional structures of the parameres/median lobes (e.g. Platynotina and Eurynotina, Opatrini); however other groups of Tenebrionidae Latreille with structures described as "clavae", "lacinia", "struts", or "styles" were also sampled for morphological study and com-parison. Taxa were also chosen for potential homology and concurrent terminology based on literature descriptions. Taxa Phylacastus Fairmaire, 1897: 116. Koch 1954a1954b: 2;1956: 27;Kamiński 2016: 245. Type species. Phylacastus striolatus Fairmaire; by monotypy. Diagnosis. Within Eurynotina, Phylacastus largely resembles Eurynotus and Capidium Koch. All three have relatively sharp basal pronotal angles, rather than broadly rounded as is the case in the rest of Eurynotina (Kamiński 2016: fig. 2). The only other exception is Oncotus Solier which, while some representatives have basal angles of the pronotum similarly shaped, is separable by prosternal process shape (rounded rather than angular in lateral view (Kamiński 2016), body shape (much rounder/transverse than Phylacastus), tibial morphology (foretibia greatly expanded apically and with a sharp lateral projection; Kamiński 2016), and coloration (species may be bicolored and/or very pale or testaceous in color). Phylacastus can be easily separated from all other subtribal representatives by the presence of (at most) weak tubercles on the apical declivity of the elytra (Figs 1, 2), the form of the prosternal process which is angular rather than rounded in lateral view (Kamiński 2016: fig. 2D), and the pronotum with basal angles present rather than absent/rounded) (Kamiński 2016: fig. 2J).
Capidium can be separated from Phylacastus most reliably via the structure of the prosternal process and abdominal ventrite V (prosternal process rounded and not produced in Capidium, angular and produced in Phylacastus (Kamiński 2016), and subapical sulcus absent in Capidium (present in Phylacastus); additionally, although Capidium also is defined by angular basal angles of the pronotum (Kamiński 2016), the angles are usually more produced. Finally, the elytral sculpturing and tuberculation of representatives of Capidium (when present) are stronger than in Phylacastus.
Genus redescription. Length 4-8 mm. Shining to dull; colored tenebrous; reddish to dark brown/black. Head: epistoma with well-defined median notch. Transition between clypeus and frons gradual and smooth along lateral edge, or with slight depression. Coarsely punctate, punctures large and closely spaced, separated by ≤ 1 feature diameter. Mentum with enlarged, ventrally projecting middle portion parallel-sided to slightly narrowing apically with reduced/slightly hidden lateral wings. Gula with stridulatory file. Eye constricted in middle and reniform, with strong to weakly impressed sulcus situated around posterior perimeter of dorsal lobe. Antennae with 11 antennomeres, terminal members forming weak club. Prothorax: pronotum base straight, with basal angles roundly produced. Without lateral depression or flattening along margins. Hypomeron at most only finely sculptured and finely punctured, dull to shining. Prosternal process angulate in lateral view, weakly produced or rounded at apex, with clear sulcus running perimeter, projecting at most only weakly toward midcoxae. Pterothorax: scutellar shield small and transversely triangular. Elytra not costate, with or without shallow or weakly defined punctate striae. Intervals punctate, without microtubercles; weak to well-defined tubercles (when present) only on apical declivity. Interval X terminating before reaching elytra base. Epipleura without microtubercules, broad basally, narrowing apically. Apterous. Abdomen: punctate. Ventrite V with sulcus running parallel to apical perimeter. Legs: femora slightly curved and expanded toward apex. Tibiae dorsoventrally compressed. Meso-and metatibia slightly curved. Foretibia dilated triangularly toward apex with coarse spines underneath. Male terminalia: tegmen bipartite with or without ancorae (small ancorae present in one species); basal portion membranous ventrally; dorsally with small, triangular membranous field at base of apical portion. Parameres fused dorsally at base, apical opening (in dorsal view) small or broad (Fig. 4). In lateral view, parameres flattened toward apex, with or without slight curvature. Female terminalia: paraprocts nearly as long or slightly longer than coxites I-IV, coxite IV reflected dorsally with gonostyli present (Fig. 5); bursa copulatrix divided into two sections by median constriction (bilobate) or not (Fig. 6), with or without additional "accessory pouch" situated near to spermatheca and accessory glands.
Key to the species of the genus Phylacastus Diagnosis. Phylacastus ancoralium is highly modified compared with its congeners. In addition to its wide geographic separation from other species (Lesotho), it can be separated from all other species of Phylacastus via the elytra (with extremely weak to absent elytral striae), prosternum (weakly produced between forecoxae, rather than projecting more strongly beyond (Fig. 3E)), aedeagus with ancorae on the ventral surface of the parameres (Fig. 4G), and ovipositor relatively short compared to other species (ratio of ovipositor coxites I-IV to paraprocts nearly 1:1, rather than more distinctly < 1:1) (Fig. 5).
Etymology. This species is named for the ancorae of the male aedeagus, which in Blaptinae are hypothesized to anchor the male genitalia during copulation. To date, this is the only species within the subtribe Eurynotina with ancorae.
Distribution. Lesotho.   Notes. Koch described both Phylacastus crypticoides and P. pretoriensis (1954a), differentiating them from the already described P. striolatus and his additional species P. rhodesianus based on the following: P. pretoriensis with a basal pronotal margin that 1 Some collecting events are likely erroneous in their coordinates (24.40°S, 24.42°E and 23.49°S, 20.17°E). These localities should be represented in northeastern South Africa (circa 24.40°S, 28.42°E); however, the coordinates as written on the labels refer to far-off localities in Botswana. As such, while the labels are recorded here, these points are omitted from the species' range map. is reduced medially, and P. crypticoides with a cariniform structure of the mentum and a more apically positioned sulcus on abdominal ventrite V. Upon investigation here, the margination of the pronotal base, while variable, appears to be consistently present in all species with no uniform reduction in restricted populations or collection events examined here. The sulcus of abdominal ventrite V is also consistent between specimens of both of Koch's species. Furthermore, P. crypticoides and P. pretoriensis specimens compared with his type material bear the carina attributed to P. crypticoides. As such, we have decided here to synonymize the two species under P. crypticoides. Redescription. Length 6-7 mm. Head: punctures separated by < 1 diameter. Mentum broad, lateral wings concealed, midportion with thin, distinct medial carina. Prothorax: pronotum punctate, punctures closely spaced, separated by ≤ 1 diameter. Hypomeron lightly wrinkled to rugose. Prosternal process produced between forecoxae (Fig. 3D). Pterothorax: elytra width about equal to pronotal width. Elytral striae, intervals punctate; striae clearly impressed. Interval punctures closely spaced (≤1 diameter), slightly smaller than strial punctures. Elytral tubercles absent; apical declivity with at most weak bumps or callosities (Figs 1C, 2E, F). Abdomen: ventrite V sulcus narrowly separated from apical border. Terminalia: male: parameres tapering apically, fused basally with narrow opening at apex exposing median lobe. Female: ovipositor slightly elongate (ratio of ovipositor coxites I-IV to paraprocts < 1:1). Bursa copulatrix not bilobate, accessory gland present near-to spermatheca, accessory pouch absent.

Phylacastus crypticoides Koch
Distribution. South Africa.  Diagnosis. As of this revision, this is the smallest species of the genus (4-6 mm). In addition to its size, this species is further defined by the presence of well-defined tubercles on the apical declivity of the elytra-a trait shared only by P. rhodesianus, which is larger and can be further differentiated by 1) punctures on elytral intervals (more numerous and dense in P. rhodesianus); 2) the shape of the mentum is broad, not tapered, further concealing the lateral wings in P. rhodesianus (Fig. 3C), tapers apically, exposing lateral wings in P. makskacymirowi (Fig. 3B); 3) aedeagus with a wide space between parameres, exposing large portion of median lobe in P. rhodesianus (Fig. 4C), narrow exposing only the tip of the median lobe in P. makskacymirowi (Fig. 4D).

Phylacastus striolatus
Distribution. South Africa. Note. While Fairmaire did not specify the number of specimens he examined in his original description, he did make mention of the collector (E. Simon) and locality, making specimens of his syntype series identifiable. Two specimens from MNHN are here designated as the lectotypes to fix the taxonomic status of the species.

Revision of genus Phylacastus
Overall, there were relatively few specimens available for study (n = 45), which may represent restricted ranges or collecting bias, although the collections we sampled represent older historical collections of their range. Despite the number of specimens, we borrowed and examined all of the type material, as well as additional representatives of all species. As of this revision, many of the traits that Koch (1954a) used to diagnose Phylacastus are still supported; however, some characters (e.g. the joining of the pronotum and elytra and the dilated male protarsi) were difficult to reliably confirm in the material gathered for this study. We interpret Koch's (1954a) species P. crypticoides and P. pretoriensis as synonymous, as the traits used to differentiate them (mentum with sharp median carina in P. crypticoides and lack of basal pronotal margination in P. pretoriensis) were actually congruent between Koch's type material for both species in the case of the mentum, and inconsistent throughout all the available material in the case of the pronotal margins. As to Koch's (1954a) asserted relationship between Phylacastus and Eurynotus, additional phylogenetic study using morphological and/ or molecular data will be required (Lumen and Kaminski in prep.). Currently, as of this revision their affiliation is not rejected-both genera have angled basal margins of the pronotum, angular prosternal processes, and tubercles on the apical declivity of the elytra (though often reduced in Phylacastus). The ovipositor of Phylacastus is only diagnostic for one species (P. ancoralium), and the genus appears to be overall congruent with other representatives of the subtribe (e.g. Oncotus), while also differing from Eurynotus, which has extremely long paraprocts (Iwan 2000;Banaszkiewicz 2006). There is some variation in the construction of the internal female anatomy of Phylacastus. In particular, P. striolatus and P. rhodesianus have a bursa copulatrix which is divided into two "lobes" by a median constriction (Fig. 6A), and there is an additional pouch situated near the spermatheca and accessory glands in P. striolatus and P. ancoralium (Fig. 6A, C). While the function of these structures is unclear at present, there may be similar structures in other representatives of the subtribe (e.g. Eurynotus capensis (Fabricius) appears to have a similarly divided bursa copulatrix; Tschinkel 1978: fig. 1), which may be helpful for diagnosing groups or for phylogenetic inference. Additionally, there were some accessory structures on the aedeagi of P. ancoralium and P. makskacymirowi. Namely, the former possesses structures historically referred to as "lacinia" or "clavae", and P. makskacymirowi has small, preapical sutures or grooves on the ventral side of the parameres. While the case of P. ancoralium is discussed in the below section, it is possible that the structures in P. makskacymirowi offer additional flexibility in the parameres.

Male terminalia analyses
Our discovery of accessory structures on the parameres of P. ancoralium (Fig. 4G) raise questions not only on the phylogenetic placement of the species, but on the concept of Eurynotina and the way such structures have been defined historically in Tenebrionidae (e.g. Koch 1954aKoch , b, 1955Koch , 1956Iwan 2001Iwan , 2002Iwan , 2004. The revelation of these structures highlights the necessity of investigating Eurynotina, as well as other enigmatic and poorly understood groups. One such subtribe, Helopinina Lacordaire (Pedinini Eschscholtz), is morphologically similar to Eurynotina, despite molecular evidence separating them (Kamiński et al 2021a, b;Fig. 8). In the case of Helopinina, there is also a marked reduction in accessory structures (similar to Eurynotina), though they can be differentiated in other ways (e.g. scale-like setation, non-reduced or elongate basal apophyses, basal versus apical tegmen length ratio, lack of stridulatory gula). A literary review revealed a myriad of terms used to refer to accessory structures associated with the median lobe, parameres, and tegmen (Antoine 1930;Español 1945;Doyen and Tschinkel 1982;Doyen 1984;Iwan 2001Iwan , 2002Iwan , 2004Kamiński et al. 2019). Terms which have garnered the most use historically and recently are "clavae" and "lacinia." Unfortunately, they have not been used uniformly, nor explicitly/formally defined in a way that is easily traceable or consistent. In fact, the two most used terms appear to follow authorship in North America ("clavae"-see Doyen and Tschinkel 1982;Doyen 1984;Aalbu et al. 2012;Johnston 2019) versus elsewhere ("lacinia"-see Español 1945;Iwan 2001). Thus far, the terms appear to have been used in an effort to qualitatively describe their shape. However, "clavae" is misleading in this regard and is much more widely used to refer to antennae (e.g. clava in Hymenoptera, Yoder et al. 2010). Additionally, while lacinia may adequately describe the form in some taxa, it misses the mark in others (e.g. Anomalipus spp.) and overlaps with much more widely used anatomical features (lacinia of the maxillary mouthparts of insects; Lawrence et al. 2011). Iwan (2004 gave a definition using the term lacinia (accessory spike-or hook-like structures which connect the median lobe with the inflexed alae of the apical piece), while also outlining their potential function (a means for the male to anchor itself internally during copulation as they extend/ evert)-as well as the change in aedeagal function in groups which lacked them, such as Eurynotina (switching from lateral movement of "lacini" to a dorsoventral motion with a sclerotized median lobe and flexible parameres).
The aforementioned accessory structures to the median lobe and parameres have been recorded in two subfamilies and appear to be uncommon within Tenebrionidae. The first subfamily, Blaptinae, has several tribes (Amphidorini LeConte, Dendarini Mulsant & Rey, Pedinini, and Platynotini), and the second, Diaperinae, has one subtribe (Adelinina LeConte) that seem to have evolved variations of this characteristic morphology (Doyen 1984;Kamiński 2015b;Johnston 2019;Kamiński et al. 2021a). As a result of their unique and varied appearance, "clavae" or "lacinia" have been used to diagnose many tribes and subtribes (see Koch 1958;Doyen 1984;Iwan 2001); though in the case of some subtribes there are representatives that stand out contrastingly with their cohort as either having these structures (e.g. Phylacastus ancoralium,unusual in Eurynotina;Fig. 4G) or lacking them (e.g. Anomalipus heraldicus Gerstaecker and Anchophthalmus spp. of Platynotina or Amatodes Dejean (Fig. 9A), Ametrocera Fåhraeus, and Oncopteryx Gebien of Helopinina).