Quasicalathus conservans 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

Quasicalathus conservans Schmidt & Will sp. nov.

Material studied.

Male in Rovno amber, with specimen label data " SDEI-Amb-002529 ", deposited in the Senckenberg Deutsches Entomologisches Institut, Müncheberg, Germany. Size of the amber piece 20 × 10 × 8.5 mm.

Preservation status: The amber is clear but pervaded by numerous small air bubbles and extensive flowlines attached to the embedded fossil that is therefore only partly visible using light microscopy (Figs 32 , 33 ). The exoskeleton of the fossil, including most parts of the aedeagus, is well preserved and, therefore, important diagnostic characters could be reconstructed using micro-CT (Figs 78 - 89 ).

Syninclusions: One stellate hair, few tiny dust particles.

Description.

Measurements see Table 2 .

Standardized body length: 7.3 mm.

Proportions: A3L/HL = 0.44;

EyL/ HW(-) = 0.72;

PW/HW(+) = 1.40;

PW/PL = 1.27;

PW/PWb = 1.11;

PWb/PWa = 1.46;

EW/PW = 1.64;

EL/EW = 1.51;

EpL/EpW = 1.43;

EL/FL = 2.58;

EL/AedL = 3.64.

Head: As described in Q. elpis .

Prothorax: Pronotal lateral margin moderately narrowed toward base, slightly concave before laterobasal angles, angles slightly obtuse (Fig. 78 ). Prosternal process with traces of a lateral bead (Fig. 85 ). In all other characters as described for the new genus, above.

Pterothorax: Elytra with basal margin markedly concave and humerus markedly protruded anteriorly; basal margin forming a slightly obtuse angle (ca. 115°) with the lateral margin (Fig. 78 ). Elytral striae moderately deeply engraved, intervals moderately convex. In all other characters as described for the new genus, above.

Aedeagus: Length of median lobe about 1.33 mm; median lobe terminal lamella moderately long, almost evenly narrowed from base to apex (Fig. 88 ); terminal lamella almost straight, with tip very slightly bent ventrally (Figs 87 , 89 ). In all other characters as described for the new genus, above.

Differential diagnosis.

In external characters, Q. conservans sp. nov. appears identical to Q. elpis , however, it can be distinguished by the male genitalia. The new species differs by the proportionally larger aedeagus (EL/AedL = 3.64 instead of 4.05 in Q. elpis ) and by the shape of the median lobe terminal lamella that is nearly evenly narrowed toward the apex if viewed in dorsal aspect and almost straight if viewed laterally (Figs 43 , 44 versus 87, 89). Quasicalathus conservans sp. nov. differs from the above-described Q. agonicollis sp. nov. by larger body (SBL> 7 mm), less obtuse laterobasal pronotal angles, the more markedly concave elytral basal margin, more markedly projected humeri, the less obtuse humeral angle (<120°), and by the larger aedeagus.

Remarks.

Quasicalathus conservans sp. nov. and Q. elpis are, based on current knowledge, indistinguishable in their external characters but differ clearly in the shape and proportions of the male genitalia. Ball and Nègre (1972) and Schmidt (2018) detailed a similar situation found among many species pairs of Mexican and Himalayan Calathus that can only be separated by features of the male genitalia. We hypothesize that Q. elpis and Q. conservans sp. nov. were most likely allopatric species, distributed in geographically separated parts of the Eocene amber forests of northern Europe. Under this hypothesis, Q. elpis was endemic to the more western part of the Eocene forest and was thus fossilized in Baltic amber, while Q. conservans sp. nov. was endemic to the more eastern part of the area and therefore fossilized in Rovno amber. This assumption is consistent with the faunistic data showing that beetle fossils of Baltic and Rovno amber deposits have only few species in common (less than 13%; Matalin et al. 2021).

Figures

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 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 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 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.