Quasicalathus agonicollis 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 agonicollis Schmidt & Will sp. nov.

Figs 21-24 , 25-30 , 31 , 65-72 , 73-77

Holotype.

Male in Baltic amber, with specimen label data " SDEI-Amb-002528 ", deposited in Senckenberg Deutsches Entomologisches Institut, Müncheberg, Germany. The original size of the amber piece was 60 × 23 × 7 mm and was separated into three pieces (SDEI Amb-002528 a, b, c) in order to get better micro-CT scanning results. The size of the amber piece bearing the calathine fossil measures approx. 15 × 9 × 4 mm (Fig. 28 ).

Preservation status: A clear piece of amber with the embedded carabid fossil well visible, however, extensive flowlines are present in front of the head and on the right side of the beetle body. Several parts of the beetle body are additionally covered by a white coating so that details of the exoskeleton are not visible using light microscopy; this includes the dorsal surface of head and pronotum, lateral parts of the elytra, right side of the ventral surface (Figs 29 , 30 ). The external surface of the fossilized beetle body yields low (head, thorax) or relatively moderate contrast (elytra, abdomen) during micro-CT scan and therefore, the anterior part of the body could only be coarsely imaged (Fig. 65 ). The aedeagus with median lobe and right paramere is moderately well preserved and could partly be imaged using micro-CT data (Figs 68-72 ); the left paramere provided contrast during CT scan that was too low for reconstruction.

Syninclusions: SDEI-Amb-002528a: seven very tiny insect larva, dust particles; one mite on the carabid fossil near the beetle’s scutellum. SDEI-Amb-002528b: one Myrmicinae ant, three Nematocera flies, stellate hairs, dust particles. SDEI-Amb-002528c: dust particles.

Additional material.

Female in Baltic amber, with specimen label data " GZG BST 16188 " and “K2192” (ex coll. Klebs), deposited in Geoscience Museum, University of Göttingen, Germany. Size of the amber piece approx. 12 × 7 × 4 mm, with seven polished edges (Figs 21 , 22 ); one edge bears the inscription “G644”.

Preservation status: The amber stone is clear in most parts but its surface shows several corrosion cracks (Figs 23 , 24 ); the ventral surface of the fossil is completely covered by a milky coating (Fig. 22 ). The exoskeleton of the fossil is moderately well preserved and could therefore be imaged in most details using micro-CT (Figs 73-75 ), including the gonocoxites (Figs 76 , 77 ).

Syninclusions: Stellate hairs, dust particles.

Remarks.

The specific identity of this second fossil specimen with the holotype of Q. agonicollis sp. nov., given the current state is difficult to substantiate. This is due to the poor preservation state of the holotype specimen. In the specimen GZG 16188, the pattern of head microsculpture is quite differently developed from that what we found in Q. elpis and the below described Q. conservans sp. nov., however, this character state is unknown for the Q. agonicollis sp. nov. holotype. Therefore, our decision to identify GZG 16188 as Q. agonicollis sp. nov. must be considered provisional. It is based on the following four interspecific diagnostic character states that Q. agonicollis sp. nov. holotype and specimen GZG 16188 share: i) body size small, SBL below 7 mm. ii) pronotal laterobasal angles more markedly obtuse; iii) elytral basal margin moderately concave; iv) humerus slightly protruded with humeral angle more markedly obtuse. Therefore, in the description of Q. agonicollis sp. nov. we separate the descriptions of the Q. agonicollis sp. nov. holotype and the specimen GZG 16188.

Description of the holotype.

Measurements see Table 2 .

Standardized body length: 6.7 mm.

Proportions: A3L/HL = 0.45;

EyL/ HW(-) = 0.62;

PW/HW(+) = 1.45;

PW/PL = 1.26;

PW/PWb = 1.17;

PWb/PWa = not available;

EW/PW = 1.60;

EL/EW = 1.55;

EpL/EpW = 1.40;

EL/FL = 2.42;

EL/AedL = 4.07.

Head: Patterns of microsculpture could not be studied. In all other characters as described for the new genus, above.

Prothorax: Pronotal lateral margin more markedly narrowed toward base than in Q. elpis , straight just before laterobasal angles, angles markedly obtuse (Figs 65 , 66 ). Prosternal process with traces of lateral bead evident. In all other characters as described for the new genus, above.

Pterothorax: Elytra with basal margin moderately concave and humerus moderately protruded anteriorly; basal margin forming a more obtuse angle (ca. 125°) with lateral margin (Figs 65 , 66 ). Elytral striae moderately deeply engraved, intervals moderately convex. In all other characters as described for the new genus, above.

Aedeagus: Length of median lobe 1.12 mm. Median lobe terminal lamella almost evenly narrowed from base to apex with side margins almost straight; apex slightly bent ventrally (Fig. 70 ). In all other characters as described for the new genus, above.

Description of specimen GZG 16188.

Measurements see Table 2 .

Standardized body length: 6.9 mm.

Proportions: A3L/HL = 0.44;

EyL/ HW(-) = 0.65;

PW/HW(+) = 1.46;

PW/PL = 1.26;

PW/PWb = 1.12;

PWb/PWa = 1.40;

EW/PW = 1.63;

EL/EW = 1.53;

EpL/EpW = 1.62;

EL/FL = 2.55.

Head: Microsculpture consists of moderately large isodiametric sculpticells (Fig. 24 ). In all other characters as described for the new genus, above.

Prothorax: Pronotal lateral margin almost completely rounded, straight just before laterobasal angles, angles markedly obtuse (Figs 23 , 25 , 73 , 74 ). Prosternal process with traces of an apical bead (Fig. 75 ). In all other characters as described for the new genus, above.

Pterothorax: Elytra with basal margin moderately concave and humerus moderately protruded anteriorly; basal margin forming a more obtuse angle (ca. 125°) with lateral margin (Figs 23 , 73 , 74 ). Elytral striae shallowly engraved, intervals rather flat. In all other characters as described for the new genus, above.

Female genitalia: Length of apical gonocoxite about 0.15 mm; shape see Figs 76 , 77 ; bursa copulatrix is not preserved. In all other characters as described for the new genus, above.

Differential diagnosis.

Quasicalathus agonicollis sp. nov. differs from Q. elpis and Q. conservans sp. nov. by the smaller body (SBL < 7 mm), more obtuse laterobasal angles of the pronotum, less concave elytral basal margin, less projected humeri, a more obtuse humeral angle (> 120°) and relatively smaller aedeagus. Based on specimen GZG 16188, Q. agonicollis sp. nov. differs from Q. elpis and Q. conservans sp. nov. additionally by presence of moderately large isodiametric sculpticells on head disc (small and transverse meshes in Q. elpis and Q. conservans sp. nov.) and (from Q. elpis ) by the smaller apical gonocoxite (unknown in Q. conservans sp. nov.). Due to the uncertainties in the identification of the Q. agonicollis sp. nov. non-type female specimen (see Remarks above), the latter differential characters need confirmation based on additional material. The eyes of the Q. agonicollis sp. nov. holotype and the GZG 16188 specimen are found to be proportionally smaller [EyL/ HW(-) = 0.62 resp. 0.65] than in Q. elpis (0.72) and the Q. conservans sp. nov. holotype (0.72).

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 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 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 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.

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 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).