Ceratognathini gen. et sp. indet. 2, 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/1C2BBF0D-23CC-59BD-B193-C88B171DB1B8 |
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treatment provided by |
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scientific name |
Ceratognathini gen. et sp. indet. 2 |
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Ceratognathini gen. et sp. indet. 2 View in CoL
Figs 1E View Figure 1 , 13 View Figure 13
Material examined.
1 ex. (sex undertemined), a nearly complete adult preserved in a flattened semicircular yellowish amber, approximately 16.7 mm × 6.6 mm × 2.5 mm in size (Fig. 1E View Figure 1 ); specimen accession number SEHU-0000121208, housed in HUM. Although the specimen appears well-preserved (only slightly modified) with nearly a complete body, the left metatarsomeres beyond the second segment were lost (Fig. 13C View Figure 13 ). More importantly, a thin air layer on the ventral surface of the body makes it difficult to observe the ventral body parts, such as the abdomen and antennae.
Locality and horizon.
Hukawng Valley (26°20'N, 96°36'E), Kachin State, northern Myanmar; unnamed horizon, mid-Cretaceous, Upper Albian to Lower Cenomanian.
Description.
Details of ventral side not uniformly observable. Body (Fig. 13A, B View Figure 13 ) small, narrowly elongate, subparallel sided, 2.72 mm long (measured from anterior margin of head to apex of elytra). Color uniformly dark brown. Dorsal surface somewhat modified, probably due to the fossilization process, seemingly densely punctured, without neither apparent setae nor modified scales. Head (Fig. 13A-D View Figure 13 ) small, transverse, 0.60 mm wide across eyes; vertex flattened. Compound eye (Fig. 13A-D View Figure 13 , ey) large, entire, not divided by ocular canthus. Antennae and mouthparts not visible. Pronotum (Fig. 13A, D View Figure 13 ) moderately transverse oval, with arcuate and very weakly crenulate lateral margins, 0.92 mm wide and 0.70 mm long (along midline). Elytra (Fig. 13A, C, E View Figure 13 ) complete, narrowly elongate, nearly subparallel-sided, with left elytron 1.87 mm long (measured from pronotal posterior end to apex of elytron) and 0.45 mm wide; outer margins, particularly those of posterolateral ones, narrowly explanate. Legs (Fig. 13A-C, F, G View Figure 13 ) relatively short, slender. Protibia (Fig. 13A, B, F View Figure 13 ) slender, flattened, only weakly curved, gradually slightly widened towards apex, 0.60 mm (left) in length, with one large apical spur (see Fig. 13F View Figure 13 , as); external margin armed with three strong teeth in apical half, i.e., apical tooth (at) and mid-dorsal teeth 1-2 (mdt1 - 2) (sensu Holloway 2007: fig. 1), with 5 short and subcontiguous tooth-like spines before mid-dorsal tooth 1, 3 between mid-dorsal tooth 1 and mid-dorsal tooth 2, and finally 4 between apical tooth and mid-dorsal tooth 2 (Fig. 13F View Figure 13 , arrow). All tarsi (Fig. 13A-C, F, G View Figure 13 ) 5-segmented, each slender and rather long. Arolium (Fig. 13F, G View Figure 13 , ra, sa) developed, with rather long rod, bearing 2 bristles on its apex. Abdomen not well visible. Genitalia not visible.
Systematic placement and comparison.
An accurate definitive assessment of the systematic position of this fossil is difficult; there is no clear view of the ventral side due to a thin whitish air layer, which makes several important features unobservable, such as the abdominal segmentation, details of the antennae, and prosternal process (Fig. 13B View Figure 13 ). Nevertheless, its putative placement in the lucanid tribe Ceratognathini is supported by the protibial structures, namely the protibial edges have a peculiar arrangement of spine-like teeth (Fig. 13F View Figure 13 ). Overall, the other features, including the general habitus, head, pronotum, and 5-5-5 tarsal formula, generally agree well with the ceratognathins, particularly the extinct ones described above. Unlike Oncelytris , there is no distinct tubercles found on the elytra (see Li Y-D et al. 2023). Based on the structures of the protibial edges, this specimen cannot be assigned to Cretognathus gen. nov., " Ceratognathini gen. et sp. indet. 1," or any extant ceratognathin genus. However, this taxonomic consideration as a lucanid is provisional; further visualization and verification is needed for a definitive assignment.
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