Phasmister parallelus Caterino and Yamamoto, 2023

Caterino, Michael S. & Yamamoto, Shûhei, 2023, New Onthophiline Fossil Species (Coleoptera: Histeridae: Onthophilinae) from Mid-Cretaceous Burmese Amber, The Coleopterists Bulletin 77 (3), pp. 432-438 : 435-437

Phasmister parallelus Caterino and Yamamoto , new species zoobank.org/ urn:lsid:zoobank.org:act:FD8814F7-CC2C-454F-BD7E-9C7726DDEC83 ( Figs. 2 , 3C )

carinae extending further anteriad, meeting posterior corners of this pentagon, rather than meeting the median carina before the middle. Details visible in this specimen, not fully described in P. cristatus , include: labrum short, rounded, separated from epistoma by distinct suture; mandible (left) weakly excavate on outer surface, with outer margin strongly angulate to acute apical tooth; maxillary palp 4-segmented, basal palpomere barely visible, third palpomere shorter than second, apical palpomere about twice as long as penultimate, rather bulbous at base, narrowed to weakly obliquely truncate apex; antennal scape curved, pedicel nearly as wide as scape, about twice as long as succeeding segment; antennomeres 3–8 (funicle) gradually decreasing in width; antennal club oval, only slightly

Type Material. Holotype specimen, of unknown sex (SEHU-0000121203); deposited in HUM. Type locality: Northern Myanmar: Kachin State, Hukawng Valley, Noije Bum Hill. The holotype is embedded in a small, rather flattened, more-or-less rectangular, yellowish transparent amber piece (6.1 × 3.8 × 1.9 mm). The right mesotarsus is partially lost due to over-polishing, but all mesotarsomeres are preserved.

Diagnostic Description. Full body length, in situ: 1.24 mm (apex of pronotum to posterior end of abdomen); body (pronotum + elytra) length: 1.18 mm; maximum (humeral) width: 0.89 mm; pronotal length: 0.45 mm; pronotal width: 0.75 mm. This species shares many of the generic level characters described for Phasmister (Caterino 2021) : body subquadrate, weakly compressed; elytra with every second interstria strongly raised to form a carina; humeral elytral angles expanded; pronotum with raised lateral and anterior margins, depressed in anterior corners, with various carinae on disc; pronotal disc strongly punctate; posterior pronotal margin sinuate, produced posteriad in front of small scutellar shield; frons with dorsal and lateral 436 margins raised; antennal insertions open anteriorly; distinct, with paired and widely separate median antennal club with distinct, transverse, annulate carinae, joined only near the base, while both sutures; prosternum with lateral slots for passage of preceding species have a single median carina the antennal funicle; hypomeral antennal depression divergent only near the anterior margin. In open beneath. It differs from its congeners in the tibial characters in particular, P. parallelus ap- following specific characters: body thicker, more pears more plesiomorphic, with the slender tibiae convex, elytral surface more gradually descending of P. cristatus and P. hkamticus constituting (in lateral aspect) to apices; prothorax less strongly apomorphic states. transverse, length/width ratio slightly greater; paired Synclusions. There is a partial fragment of an median pronotal carinae divergent at basal fourth, arthropod leg located close to the holotype. subparallel to apex; curved paramedial pronotal carinae weaker; lateral longitudinal pronotal carinae Carinumerus intricatus Caterino and well developed, curving mediad near middle; Yamamoto, new species anterior corners of pronotum curved more inward, zoobank.org/urn:lsid:zoobank.org:act:

less strongly explanate; sublateral elytral carina

0E01A568-570D-465B-A7FA-3C666F043847 (between stria 1 and inner subhumeral stria) more ( Figs. 4 , 5C ) evenly curved from base to apex, only weakly sinuate; tibiae, especially protibia, broader, with angu- Type Material. Holotype specimen, of unknown late lateral margin, less elongate, apical process sex (SEHU-0000121204); deposited in HUM. Type weak; tarsi similarly shorter; protarsal groove along locality: Northern Myanmar: Kachin State, Hukawng mid-axis of protibia, rather than along outer margin. Valley, Noije Bum Hill. The holotype is embedded Derivation of Specific Name. The name parallelus in a small, narrowly elongate-ovoid, yellowish transis an adjective referring to the paired pronotal carinae, parent amber piece (11.5 × 4.2 × 2.3 mm). which are parallel along much of their lengths. Diagnosis. Full body length, in situ: 1.27 mm Remarks. The body shape and tibial shape dif- (apex of pronotum to posterior end of abdomen); ferences of P. parallelus from the previously de- body (pronotum + elytra) length: 1.17 mm; maxiscribed species are detailed above. The pronotal mum (humeral) width: 1.19 mm; pronotal length: carinae ( Fig. 3C ) of P. parallelus are also quite 0.42 mm; pronotal width: 0.89 mm. Similar in most

Remarks. While all Carinumerus species are very similar, the pronotal carinae of the three species are distinct. In C. yingae there are several more-or-less parallel carinae on each side, including two subparallel median ridges that extend two-thirds the length of the pronotum; in C. maddisoni there are no median ridges at all, with only one short and one longer lateral carina; and in C. intricatus there appears to be a single median ridge, dividing and diverging anteriorly. The elytral strial punctures of C. intricatus appear to be somewhat smaller than those of C. yingae , while those of C. maddisoni are larger and somewhat elongated along the striae. Other views of the species are not consistently wellpreserved enough to assess clear differences. Among the available fossils of the genus, the metathoracic leg of the C. intricatus holotype is particularly clear, revealing short spines along the outer margin, a series of fine setae along the inner margin, two small but distinct apical spurs, and an inwardly pointing apical process. The basal four metatarsomeres (as with all the others) have a single pair of distinct setae at their apices.

Syninclusions. There are no other Arthropoda inclusions.

respects to its two known congeners ( C. yingae and C. maddisoni ), with all elytral interstriae evenly carinate, expanded humeral angles, and raised frontal margins. Species-level differences of C. intricatus are subtle, and somewhat difficult to observe in the fossil, with the pronotal disc obscured by an airfilled fracture. The pronotum bears a single median ridge (or possibly very approximate, parallel median ridges) that diverge near the anterior margin; distinct submedian carinae converge toward the anterior arms of the median pronotal ridge near the anterior pronotal margin; the elytral strial punctures are small.

Derivation of Specific Name. The species name intricatus is a participle referring to the intricate pattern of pronotal carinae that distinguish it.

Figures

Fig. 2. Habitus images of Phasmister parallelus, new species. A) Dorsal, B) Ventral, C) Lateral, D) Dorsolateral, E) Anterior, F) Posterior. All scale bars 0.5 mm.

Fig. 3. Comparison of pronota of Phasmister spp. A) P. cristatus, B) P. hkamticus, new species, C) P. parallellus, new species.

Fig. 4. Habitus images of Carinumerus intricatus, new species. A) Dorsal, B) Ventral, C) Lateral, D) Anterodorsal. All scale bars 0.5 mm.

Fig. 5. Comparison of pronota of Carinumerus spp. A) C. maddisoni, new species, B) C. yingae, C) C. intricatus, new species.