Cretognathus minutissimus, Yamamoto, 2023
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publication ID |
https://dx.doi.org/10.3897/evolsyst.7.104597 |
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publication LSID |
lsid:zoobank.org:pub:921F39DA-40BB-4796-8E36-2194D1E9A138 |
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persistent identifier |
https://treatment.plazi.org/id/A12A7EF3-8BE0-4BB2-9F23-130C6B7F9313 |
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taxon LSID |
lsid:zoobank.org:act:A12A7EF3-8BE0-4BB2-9F23-130C6B7F9313 |
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treatment provided by |
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scientific name |
Cretognathus minutissimus |
| status |
sp. nov. |
Cretognathus minutissimus sp. nov.
Figs 1C View Figure 1 , 6 View Figure 6 , 7 View Figure 7 , 8 View Figure 8 , 9 View Figure 9 , 10 View Figure 10
Material examined.
Holotype (sex undertemined), a complete adult preserved in a large, very flat, oval yellowish amber, approximately 24.5 mm × 14.4 mm × 1.9 mm in size (Fig. 1C View Figure 1 ); specimen accession number SEHU-0000121206, housed in HUM. The holotype specimen is well preserved, but pigmentation inside the amber makes detailed observation and photography difficult, particularly of the ventral side. Furthermore, the ventral surface of the holotype is very dark; therefore, it is difficult to observe and photograph.
Diagnosis.
As for the genus (vide supra).
Description.
Body (Fig. 6 View Figure 6 ) very small, moderately elongate oval, 2.80 mm long (measured from apex of clypeus to apex of elytra), 1.28 mm wide, rather flattened dorsoventrally. Color uniformly dark brown; antennae and mouthparts slightly paler. Dorsum (Figs 6A View Figure 6 , 8 View Figure 8 ) glabrous, lacking modified scales; pronotum and elytra with dense, large punctures.
Head (Fig. 7A-C View Figure 7 ) relatively small, transverse, shorter than half pronotal length but wider than half pronotal width, 0.44 mm long (measured from apex of clypeus to anterior margin of pronotum) and 0.76 mm wide across eyes (Fig. 7A, C View Figure 7 ); ventral side not well visible; vertex (Fig. 7A View Figure 7 ) even, smooth, only weakly punctate, without a pair of tubercles; preocular margins (Fig. 7A, C View Figure 7 , pom) small, arcuate, not enlarged anterolaterally. Compound eye (Fig. 7 View Figure 7 , ey) relatively large, entire, not divided by ocular canthus. Antenna (Fig. 7A, B, D View Figure 7 , a1-10) 10-segmented, non-geniculate, with three-segmented relatively strong club, 0.55 mm long (right antenna); antennomere 1 (scape) long, slender, rather strongly curved, approximately 4.7 times longer than wide, sparsely bearing three very long and thin bristles and much shorter seta, without ground setae; antennomere 2 (pedicel) small, conical, somewhat transverse, attached to tip of scape; antennomere 3 elongate, about 1.9 times longer than wide; antennomeres 4-6 short, each wider than length, successively moderately widened; antennomere 7 shorter than preceding antennomere, but distinctly transverse; antennomeres 8-10 forming relatively large club, strongly asymmetrical, each not coherent. Mandibles (Fig. 7A-C View Figure 7 , md) mostly not visible dorsally, very small, inconspicuous, much shorter than head, moderately curved, dorsoventrally flattened, with acute, sharply pointed apex. Clypeus with broadly rounded anterior margin. Maxillary palpus (Fig. 7A-C View Figure 7 , mp3-4) 4-segmented, moderately long, slender; palpomere 2 small; palpomere 3 elongate, about half length as terminal palpomere, weakly curved; palpomere 4 very long, slender, gently arcuate, slightly wider than preceding palpomere. Labial palpus (Fig. 7B View Figure 7 , lp3) probably three-segmented, rather short; palpomere 3 long, fusiform.
Pronotum (Figs 6A View Figure 6 , 8A-D View Figure 8 ) transverse, widest in middle, 1.21 mm wide and 0.87 mm long (along midline), without basolateral constriction; lateral margin gently arcuate, smooth, with very narrow gutter along whole margins (Fig. 8D View Figure 8 , pg); surface simple and even, but densely strongly punctate; anterior corners slightly produced with acute angles, whereas those of posterior ones right-angled. Procoxal cavity externally closed behind. Prosternum short, biconcaved, seemingly strongly transverse; prosternal process between procoxae very narrow, laminate, resulting in subcontiguous procoxae (Fig. 10A View Figure 10 , arrow). Scuteller shield (Fig. 8A-C View Figure 8 , sc) small, semicircular; surface even, entirely covered with rather dense, deep punctation.
Elytra (Figs 6A View Figure 6 , 8B, E View Figure 8 , 9C, D View Figure 9 ) complete, narrowly elongate, nearly subparallel-sided in anterior four-fifths, with left elytron 1.71 mm long (measured from pronotal posterior end to apex of elytron) and 0.66 mm wide; lateral margins narrowly explanate, each with inconspicuous epipleural gutter (see Yamamoto 2021) (Fig. 8B, E View Figure 8 9C, D, epg); surface smooth without tubercles, but densely covered with deep dense punctures uniformly, seemingly not forming evident longitudinal rows (Fig. 8B View Figure 8 ). Mesocoxal cavities narrowly separated (see Fig. 10B View Figure 10 ). Metaventrite (Fig. 10B-D View Figure 10 , mtv) transverse, much longer than mesoventrite; surface generally somewhat densely punctured, with deep and prominent discrimen (median longitudinal sulcus; see Fig. 10D View Figure 10 , arrow).
Legs (Figs 6 View Figure 6 , 9 View Figure 9 , 10 View Figure 10 ) short, rather thick, robust (except very slender protarsi). Protibia (Figs 6 View Figure 6 , 9A, B View Figure 9 ) robust, flattened, weakly curved, gradually widened apically, with one large apical spur; external edge armed with three strong teeth in apical half, i.e., one large, curved, and slender apical tooth (at), one large, curved, and slender mid-dorsal tooth 2 (mdt2), and one smaller, inconspicuous mid-dorsal tooth 1 (mdt1) (sensu Holloway 2007: fig. 1), with 16 short, acute, and subequal-sized tooth-like spines (8 subcontiguous ones before mdt1, 4 subcontiguous ones between mdt1 and mdt2, and 4 subcontiguous ones between mdt2 and at, see arrows on Fig. 9A, B View Figure 9 for the latter condition). Procoxa widely transverse. Mesotibia with a few small mid-dorsal spines at apical two-fifths (Fig. 9C View Figure 9 , mds), with paired prominent apical spurs (Fig. 9C, E, F View Figure 9 , as). Metacoxae (Fig. 10C, D View Figure 10 , mtc) transverse, subcontiguous. Metatibia (Fig. 9D View Figure 9 ) thick and robust, only slightly longer than metatarsus, with a few small mid-dorsal spines located at slightly beyond middle apically (Fig. 9D View Figure 9 ) and paired prominent apical spurs (Fig. 9D, G, H View Figure 9 , as). All tarsi 5-segmented, each extremely slender and long (protarsi) or thick and rather short (meso- and metatarsi); tarsomere 1 longer than tarsomere 2, tarsomeres 2-4 subequal in length, tarsomere 5 longest, as long as (protarsi) or slightly shorter (meso- and metatarsi) than tarsomeres 2-4 combined (Fig. 9 View Figure 9 ). Pretarsal claw (Fig. 9 View Figure 9 , cl) relatively short, simple, moderately curved, moderately (protarsi) or slightly (meso- and metatarsi) shorter than tarsomeres 3 and 4 combined. Arolium (Fig. 9 View Figure 9 ) well-developed, with elongate rod (Fig. 9 View Figure 9 , ra), bearing 2 long bristles on its apex (Fig. 9 View Figure 9 , sa).
Abdomen (Figs 6B View Figure 6 , 10C, D View Figure 10 ) with 5 visible ventrites (v1 - 5); central part rather swelled above; each ventrite strongly transverse; ventrites 2-4, at least, each armed with a row of large villiform teeth along posterior margin; ventrite 5 with apical margin only feebly emarginate (similar condition of the male of Mitophyllus figured in Holloway 1998: fig. 19).
Genitalia not visible.
Etymology.
The specific name " minutissimus " is a Latin adjective meaning 'extremely small’, in reference to its very small body size for the Lucanidae family.
Locality and horizon.
Hukawng Valley (26°20'N, 96°36'E), Kachin State, northern Myanmar; unnamed horizon, mid-Cretaceous, Upper Albian to Lower Cenomanian.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.