Quasicalathus Schmidt & Will, 2022

Schmidt, Joachim, Scholz, Stephan & Will, Kipling, 2022, Character analysis and descriptions of Eocene sphodrine fossils (Coleoptera, Carabidae) using light microscopy, micro-CT scanning, and 3 D imaging, Deutsche Entomologische Zeitschrift 69 (1), pp. 19-44 : 19

Genus Quasicalathus Schmidt & Will gen. nov.

Type species.

Quasicalathus conservans Schmidt & Will, sp. nov., fossil species from the Eocene Rovno amber, herein designated.

Species included.

Three fossil species from Eocene amber deposits of Central Europe:

Quasicalathus agonicollis Schmidt & Will, sp. nov. (Baltic amber).

Quasicalathus conservans Schmidt & Will, sp. nov. (Rovno amber).

Quasicalathus elpis ( Ortuño & Arillo, 2009), new combination (Baltic amber).

Diagnostic characters.

Taxon with characteristics of Calathina and Calathus , respectively, as defined by Lindroth (1956) and Ball and Nègre (1972). The combination of the following character states defines the group:

Head: normal for Calathina, not thickened (Figs 24 , 41 , 81 ); mandibles normal for Calathina, not broadened, not elongated (Figs 2 , 52 ); eye size averaged for Calathina, normally protruded (Figs 24 , 41 ); antennae pubescent from fourth antennomere (Fig. 20 ); mentum tooth simple or slightly truncated at tip, with two fine setae near its base (Figs 52 , 82 ); submentum with two setae each side in normal position, with the internal setae robust and the external setae markedly short and thin (Figs 31 , 52 , 84 ).

Prothorax: pronotal shape subquadrate ( “calathoid” form; Figs 3 , 14 , 34 , 42 , 50 , 58-60 , 63 , 64 , 73 , 78 ), slightly or moderately constricted toward base, with lateral margin straight or slightly concave before base, and with basolateral angles slightly or moderately obtuse (Figs 9 , 14 , 25 , 42 , 50 , 63 , 64 , 74 , 78 ); basolateral angles not protruded posteriorly; basal margin beaded laterally (level of basolateral angles); basolateral seta situated at margin (Figs 9 , 14 , 20 , 25 , 42 , 50 , 66 , 74 ); pronotal disc with sculpticells of microsculpture transverse, very narrow (magnification 80 ×). Prosternum impunctate, smooth, prosternal process with or without apical bead (Figs 37 , 38 , 51 , 75 , 85 ).

Pterothorax: elytra slender, ovate, glabrous, humeral tooth absent; basal bead moderately or markedly concave with humeral angle +/- markedly protruded anteriorly (Figs 9 , 14 , 25 , 34 , 47 , 58 - 61 , 66 , 74 , 78 ); epipleuron without plica (Fig. 53 ); striae slightly to moderately deeply engraved, with punctures evident (Figs 25 , 27 , 58 ); intervals flat to moderately convex; parascutellar seta present (Figs 14 , 66 , 74 ); third interval with a single rather short, thin discal seta situated near the end of the apical elytral 2/3, adjoining second stria (Figs 11 , 12 , 16 , 27 , 29 ; but see comments to the redescription of Q. elpis , below), with surroundings of setigerous puncture not depressed; external intervals without setae; intervals with sculpticells of microsculpture transverse, very narrow, narrower than on pronotum (Fig. 26 ; magnification 100 ×, elytra appearing polished at 40 ×). Metepisternum elongate (Figs 4 , 62 , 83 ). Hindwings fully developed.

Legs: length average for Calathina, neither markedly slender nor particular robust (Figs 4 , 7 , 30 , 36 , 49 , 62 ); male protarsomeres dilated; mesocoxa with a single ridge seta; metacoxa trisetose, with anterior seta large and with the two posterior setae small and thin, one located near external, one near internal margin (Figs 54 , 67 , 86 ; but see comments to the redescription of Q. elpis below); metatrochanter with seta present (but see comments to the redescription of Q. elpis , below); metafemur with two setae on ventral surface, and with dorsoapical setae present; metatibia in male not densely pubescent; tarsi without pubescence or wrinkles on dorsal surface; meso- and metatarsomeres I-IV without external and internal lateral grooves; fifth tarsomeres with a single pair of dorsal setae, and with two pairs of ventral setae; claws pectinate (Fig. 8 ).

Abdomen: ventrites smooth aside from normal setation; apical ventrite in both sexes with one pair of seta near apical margin (Fig. 53 ).

Female genitalia (Figs 55-57 , 76 , 77 ): basal gonocoxite about two times longer than apical gonocoxite; apical gonocoxite short, sickle-shaped, with one ensiform seta at dorsal and two ensiform setae at external margin, and with sensory pit large, well-developed, with two setae; basal gonocoxite without setae near apical margin; bursa copulatrix not markedly sclerotized.

Male genitalia (Figs 43-46 , 68-72 , 80 , 87-89 ): aedeagus right side ventral in repose; right paramere styloid with distal portion very long and slender, not terminated in a distinct apical hook; left paramere ovoid; median lobe with long apical lamella, without apical disc.

Etymology.

The name of the new subgenus is derived from the Latin conjunction “quasi” (like; as it were) and the name of the ground beetle genus Calathus , and thus refers to the morphological similarity to representatives of this genus.

Recognition and systematic placement within Sphodrini .

Presence of a styloid right paramere (an apomorphic character state within Sphodrini ) differentiates Quasicalathus gen. nov. from Atranopsina and Synuchina. Additionally, Quasicalathus lacks the stridulation organ that is an autapomorphy for Atranopsina ( Casale 1988). Presence of well-developed sensory pit of the apical gonocoxite (plesiomorphic state) differentiates Quasicalathus from Synuchina ( Casale 1988) and Dolichina sensu Sciaky and Facchini (1997), Sciaky and Wrase (1998) and Hovorka (2017b). Aedeagus with right side ventral in repose (right paramere styloid, left paramere ovoid; plesiomorphic state) differentiates Quasicalathus from Pristosiina. The combination of the following characters states places Quasicalathus outside of Sphodrina sensu Casale (1988): Mentum tooth not bifid (plesiomorphic state); antennae pubescent from fourth antennomere (plesiomorphic state); tarsomeres without pubescence and smooth on dorsal surfaces (plesiomorphic state); claws pectinate (symplesiomorph with Sphodrini except Atranopsina, reversed in some Sphodrina); aedeagal median lobe slender with long terminal lamella. The shape of the aedeagal median lobe and its terminal lamella is rather variable within Calathina, Dolichina and Synuchina ( Lindroth 1956, Habu 1978, Casale 1988).

Based on the overall similarity in external and genitalic characters the new, fossil genus Quasicalathus strongly resembles extant species of subtribe Calathina and genus Calathus (see next section). However, as it was comprehensively discussed by Schmidt and Will (2020), monophyly of Calathina is supported by molecular data ( Ruiz et al. 2009, 2010) while Calathus seems to be paraphyletic, and morphological data supporting Calathina monophyly are currently unknown. As a consequence, the definite, evidence-based, placement of fossil Quasicalathus species in this subtribe is currently impossible. What can be stated regarding the systematic placement of this taxon is the following:

Quasicalathus is included in the "P clade" of Ruiz et al. (2009) based on the shared presence of the markedly styloid right paramere, which is most likely an autapomorphy of this clade. Atranopsina and all but one outgroup, Zabrini, are characterized by much shorter parameres. The styloid right paramere shows a pattern of homoplasy across carabids and is considered a separate transformation in Zabrini as this group has not been shown to be the sister group to Sphodrini in relevant phylogenetic analyses (Ruiz et al. 2009, Gomez et al. 2016).

Quasicalathus is not a member of Synuchina, Dolichina or Pristosiina, as each of these sphodrine subtribes is characterized by respective autapomorphic states that are not present in the fossil specimens.

Quasicalathus is not a member of Sphodrina sensu Casale (1988) because each of the genera affiliated to this subtribe is characterized by at least one autapomorphic state that is not present in Quasicalathus (see above).

Given the lack of apparent morphological synapomorphies for subtribe Calathina and the genus Calathus there is currently no evidence that places Quasicalathus within, or as sister of, any one of these clades.

Fossils are basic for understanding the evolutionary history of species groups and fossil specimens are critical for time calibration of phylogenetic hypotheses. Therefore, in order to prevent misleading interpretations-e.g., the incorrect assignment of fossils that lack evidence of their placement-we propose the systematic position of Quasicalathus using a conservative, synapomorphy-based approach. This requires establishing the genus without a certain position within the sphodrine "P clade" of Ruiz et al. (2009), i.e., Sphodrini , informal group P clade, incertae sedis.

Recognition with respect to Calathina.

The overall similarity of Quasicalathus gen. n. with species of the genus Calathus makes it necessary to provide a detailed differential diagnosis of the new genus. Recently, Schmidt and Will (2020) presented an overview to the diagnostic characters of the currently accepted genera and subgenera placed within Calathina, and respectively Calathus , sensu Hovorka (2017a). The Eocene Quasicalathus differs from all calathine species groups by presence of a single elytral discal seta (but see Remarks section to the redescription of Calathus elpis , below). All but one Calathina are characterized by presence of at least two elytral discal setae, while the elytra of Tachalus Ball & Nègre lacks discal setae. Quasicalathus additionally differs from all calathine taxa, with the exception of Bedelinus Ragusa, by having a simple mentum tooth (entire instead of bifid), and trisetose metacoxa. Quasicalathus differs from all but the Himalayan Spinocalathus Schmidt by narrow transverse sculpticells of elytral microsculpture (nearly isodiametric in other Calathina). A slightly transverse pattern of elytral microsculpture is developed in some species of Denticalathus Schmidt, however, species of this group differ by pubescent third antennomere in addition to other characters mentioned above and below. Bedelinus and Spinocalathus differ from Quasicalathus additionally by removal of the pronotal laterobasal pronotal seta from the lateral margin, plus presence of lateral grooves on metatarsomeres I-IV. Quasicalathus differs from Spinocalathus by the short metepisterneum, and from Bedelinus and most Spinocalathus by presence of an apical hook on the right paramere. Quasicalathus shares meso- and metatarsomeres I-IV without external and internal lateral grooves with Iberocalathus Toribio, Lindrothius Kurnakov, some species of Calathus s. str., Denticalathus , and Neocalathus Ball & Nègre. However, species of these groups differ by presence of an apical hook on the aedeagal right paramere ( Lindrothius , Calathus s. str., Denticalathus , Neocalathus ) and by a markedly sclerotized spermatheca plus presence of a single ensiform seta along the external margin of the apical gonocoxite ( Iberocalathus ).

Here we hypothesize that i) presence of a single elytral discal seta and ii) presence of narrow transverse sculpticells of elytral microsculpture are synapomorphies of Quasicalathus gen. n.; the similarly developed pattern of elytral microsculpture in Spinocalathus and some Denticalathus are hypothesized as homoplasious as these groups share more derived patterns in some morphological features (e.g., bifid mentum tooth, bisetose metacoxa) together with other Calathina groups.

Figures

Figures 18 - 24. Quasicalathus, light microscopic images of Q. elpis Ortuno & Arillo, 2009 (18 - 20.) and Q. agonicollis sp. nov. (21 - 24.). 18. General view of the amber piece " MAIG 76 " (only that part of the large amber piece bearing the Quasicalathus fossil is shown; the fossil is widely covered by milky coating); 19. General view of the two fragments of specimen " GZG 16185 "; the left one bears only the negative imprint of the left elytra on the inclusion wall; 20. Right anterior part of body of specimen " GZG 16185 " showing part of head, pronotum and humerus; 21, 22. General view of the amber piece " GZG 16188 " (21. With fossil in dorsal view; 22. In ventral view); 23. Anterior part of specimen " GZG 16188 "; 24. Head of specimen " GZG 16188 ". Abbreviations: a 1 - a 6 - antennomeres 1 - 6; as - anterior supraorbital seta; bs - pronotal laterobasal seta; ms - pronotal lateral seta; ps - posterior supraorbital seta.

Figures 39 - 46. Quasicalathus elpis (Ortuno and Arillo 2009), volume rendering of specimen " Groehn 7814 " using different grey scales of the Amira software. 39. Dorsal aspect; 40. Lateral aspect. The displaced aedeagus (highlighted by red colour) was separated by the segmentation function of Amira software in Figures 39 and 40; 41. Head (the arrows point to the insertions of the supraorbital setae); 42. Pronotum (the arrows point to the insertions of the lateral setae); 43 - 46. Remains of the aedeagus in right lateral aspect (43.); Left lateral aspect (44.); Left lateral aspect (45.); Dorsal aspect (46.). The distal margins of the styloid apophysis of the right paramere in Fig. 43 and the lobate apophysis of the left paramere in Fig. 45 are highlighted by red dotted lines. Abbreviations: bb - basal bulb of aedeagal median lobe; os - distal ostium; pml - left paramere; pmr - right paramere; tl - terminal lamella of median lobe.

Figures 81 - 89. Quasicalathus conservans sp. nov., volume rendering of the holotype. 81. Head, dorsal aspect (the arrows point to the insertions of the supraorbital setae); 82. Head, ventral aspect; 83. Left external part of metathorax, ventral view; 84. Submentum (the arrows point to the insertions of the four lateral setae); 85. Posterior part of prosternum and procoxae; 86. Posterior part of metasternum and metacoxae; 87 - 89. Preserved remains of the aedeagus (87. Right lateral aspect; 88. Dorsal aspect; 89. Left lateral aspect). Abbreviations: bb - basal bulb of aedeagal median lobe; ce - compound eye; cxp - metacoxal plate; eph - partly evaginated lobes of endophallus; gu - gula; mem - metepimeron; mes - metepisternum; mtt - mentum tooth; mv - metaventrite; pcx - procoxa; pmr - preserved distal part of right paramere of aedeagal median lobe; psp - prosternal process; sc - scutellum; sps - setae of sensory pit; tl - terminal lamella of aedeagal median lobe.

Figures 1 - 5. Quasicalathus elpis (Ortuno and Arillo 2009), light microscopic images of specimens " Groehn 4879 " (1 - 3.) and " Groehn 7814 " (4, 5.). 1, 5. General view of the amber pieces; 2. Ventral side of head (the white arrow points to the mentum tooth; note that the mentum is somewhat detached from the head capsule); 3. Pronotum and anterior part of elytra showing the markedly concave basal margin and projected humeri; 4. Right lateral view of body.

Figures 52 - 57. Quasicalathus elpis (Ortuno and Arillo 2009), volume rendering of specimen " Groehn 7889 ". 52. Head, ventral aspect (the arrows point to the insertions of the setae near base of mentum tooth and on submentum); 53. Abdomen, left lateral aspect (the arrows point to the insertions of the setae on ventrites IV, V, and VI); 54. Metacoxal area (the arrows point to the insertions of the coxal setae); 55. Apical gonocoxites, ventral aspect; 56. Apical gonocoxites, dorsal aspect; 57. Gonocoxites and remains of the bursa copulatrix (the latter was highlighted by red colour using the segmentation function of Amira software). Abbreviations: at - apical tooth of retinacle; kes - metathoracic katepisternum; cx - metacoxa; cxp - metacoxal plate; des - dorsal ensiform setae; ep - elytral epipleuron; fm - metafemur; gu - gula; mdl - left mandible; gx 1 - basal gonocoxite; gx 2 - apical gonocoxite; mdr - right mandible; mo - molar; mt - mentum; sp - sensory pit; tr - metatrochanter; ves - ventral ensiform setae; v 3, v 4, v 5, v 6 - ventritres III, IV, V, VI.

Figures 31 - 33. Quasicalathus, light microscopic images of the holotypes of Q. agonicollis sp. nov. (31.) and Q. conservans sp. nov. (32, 33.). 31. Ventral side of head showing chaetotaxy of mentum; 32. General view of the amber piece with fossil in dorsal view; 32. Left lateral view. Abbreviations: ce - compound eye; el - elytron; ems - external seta of submentum; gu - gula; ims - internal seta of submentum; msf - mesofemur; mt - mentum; mtf - metafemur; prf - profemur; pt - pronotum.

Figures 13 - 17. Quasicalathus elpis (Ortuno and Arillo 2009), light microscopic images of specimens " CCHH 952 " (13 - 15.) and " OSAC 269 " (16, 17.). 13. Dorsal view of body; 14. Pronotum and anterior part of elytra showing the markedly concave basal margin and projected humeri (the white arrows point the insertion pores of the parascutellary setae); 15, 17. General view of the amber pieces; 16. Posterior part of left elytron (the white arrow points to the insertion of the discal seta).

Figures 34 - 38. Quasicalathus elpis (Ortuno and Arillo 2009), volume rendering of specimens " Groehn 4879 " (34 - 37.) and " Groehn 7814 " (38.). 34. Dorsal aspect; 35. Right lateral aspect; 36. Ventral aspect; 37, 38. Prosternum and basal portions of prolegs. Abbreviations: cx - procoxa; fm - profemur; psp - prosternal process; tr - protrochanter.

Figures 47 - 51. Quasicalathus elpis (Ortuno and Arillo 2009), volume rendering of specimen " Groehn 7889 ". 47. Dorsal aspect; 48. Left lateral aspect; 49. Ventral aspect; 50. Pronotum (the arrows point to the insertions of the lateral setae); 51. Prosternum (for better view the prolegs are partly removed using the clipping plane function of Amira software. Abbreviations: cx - procoxa; psp - prosternal process; tr - protrochanter.

Figures 58 - 60. Quasicalathus elpis (Ortuno and Arillo 2009), volume rendering of the dorsal aspects of specimens " Groehn 7962 " (58.), " CCHH 952 " (59.), and " OSAC 265 " (60.).

Figures 61 - 64. Quasicalathus elpis (Ortuno and Arillo 2009), volume rendering of specimens " MAIG 76 " (61 - 63.) and " GZG 16185 " (64.); 61. Dorsal aspect; 62. Right lateral aspect; 63, 64. Pronotum (the pronotal outline on left side is highlighted by dotted line in Fig. 64).

Figures 73 - 77. Quasicalathus agonicollis sp. nov., volume rendering of specimen " GZG 16188 ". 73. Dorsal aspect; 74. Basal portion of pronotum and anterior part of elytra (right side of body; the arrows point to the insertions of the pronotal basolateral seta and the parascutellar seta); 75. Prosternum with basal portion of prolegs; 76. Left apical gonocoxite, ventral aspect; 77. Gonocoxites, ventral aspect. Abbreviations: cx - procoxa; des - dorsal ensiform setae; fm - profemur; gx 1 - basal gonocoxite; gx 2 - apical gonocoxite; hm - humerus; pst - prosternum; sc - scutellum; sps - setae of sensory pit; tr - protrochanter; ves - ventral ensiform setae.

Figures 78 - 80. Quasicalathus conservans sp. nov., volume rendering of the holotype using different grey scales of the Amira software. 78. Dorsal aspect; 79. Left lateral aspect (aed - aedeagus); 80. Ventral aspect; the aedeagus (highlighted by red colour) was separated by the segmentation function of Amira software.

Figures 6 - 12. Quasicalathus elpis (Ortuno and Arillo 2009), light microscopic images of specimens " Groehn 7889 " (6 - 8.) and " Groehn 7962 " (9 - 12.). 6, 10. General view of the amber pieces (in Fig. 6, only the part of the large amber piece bearing the Quasicalathus fossil is shown); 7. Ventral side of body; 8. Left mesotarsi iv + v; 9. Pronotum and anterior part of elytra, left side of body; 11, 12. Medial part of left elytron (Fig. 12 shows the enlarged part of the elytron marked by the white frame in Fig. 11; the white arrow points to the insertion of the discal seta). Abbreviations: bs - insertion of the pronotal laterobasal seta; hm - humerus; I-VIII - elytral intervals 1 - 8.

Figures 25 - 30. Quasicalathus agonicollis sp. nov., light microscopic images of specimen " GZG 16188 " (25 - 26.) and the holotype (28 - 30.). 25. Posterior part of pronotum and anterior part of elytra, right side; 26. Anterior part of fifth interval of left elytra showing microsculpture; 27. Posterior part of elytra (the arrows point to the insertions of the discal setae); 28. General view of the amber piece; 29. Right dorsal view of beetle body (the arrow points to the insertion of the discal seta on left elytron); 30. Left ventral view. Abbreviations: bs - insertion of the pronotal laterobasal seta; hm - humerus; m - mite (syninclusion).

Figures 65 - 72. Quasicalathus agonicollis sp. nov., volume rendering of the holotype using different grey scales of the Amira software. 65. Dorsal aspect (the negative imprint of the fossil on the inclusion wall is shown); 66. Basal portion of pronotum and anterior part of elytra (positive of the fossilized beetle is shown; the arrows point to the insertions of the pronotal basolateral setae and the parascutellar setae); 67. Metacoxa (the arrows point to the insertions of the three coxal setae each side); 68 - 71. Aedeagus in dorsal aspect (68.), Right lateral aspect (69.), Ventral aspect (70.), Left lateral aspect (71.); The remains of the parameres are coloured (red: left paramere; green: right paramere); 72. left lateral aspect of beetle body; the aedeagus (highlighted by red colour) was separated by the segmentation function of Amira software. Abbreviations: bb - basal bulb of aedeagal median lobe; hm - humerus; os - distal ostium of median lobe; sc - scutellum; tl - terminal lamella of median lobe.