Yprezethinus grimaldii, PARKER, 2022

PARKER, JOSEPH, 2022, Transitional morphology and Afrotropical affinity of a bythinoplectine rove beetle from the early Eocene of India (Coleoptera: Staphylinidae: Pselaphinae), Palaeoentomology 5 (5), pp. 452-460 : 456-457

Yprezethinus grimaldii sp. nov.

urn:lsid:zoobank.org:act:6657B0A8-4BF3-4A3A-88DD-F943C01A9967

Holotype. Sex unknown. Label data: “ AMBER: INDIA: Gujarat / Tadkeshwar lignite mine / Cambay Form. (Paleo-Eocene) / 21°21.400′N, 73°4.532′E / I/7-12/09 Grimaldi & Nascimbene / No. Tad-130”

“Tad-130: / 1 Coleoptera : Scydmaenidae ?”

Specimen in AMNH.

Etymology. The specific name honors entomologist Dr David Grimaldi—friend, mentor, colleague and collaborator—on his 65 th birthday, and in recognition of his wide-ranging contributions to the study of fossilized insects (including pioneering the investigation of Cambay amber).

Diagnosis. As for genus.

Type locality and horizon. Cambay amber preserving Yprezethinus was collected from outcrops inside lignite mines in Gujarat state, western India, Tadkeshwar (21°21.400′N, 73°4.532′E). The horizon is estimated to be Early Ypresian (ca. 54.5 Ma; see Smith et al., 2016) .

Description. Body length: ~ 0.8 mm ( Fig. 1A ). Body largely glabrous, with smooth, shiny integument. Body color of Tad-130 dark, almost black; antennae also dark, brown-black; other appendages somewhat dark reddish brown.

Head

Head length ~ 0.13 mm ( Fig. 1A ); estimated width across eyes ~ 0.18 mm. Frontal rostrum medially sulcate. Head constrictedsharplybehindeyes,narrowingtoocciput.Gular region of head strongly convex to occipital constriction. Eye with approximately 10 facets. Antennomere 1 partially obscured but appears to be cylindrical-conical, and longer than wide, similar in width to antennomere 2. Antennomere 2 spherical, ~1.3× wider than antennomere 1. Antennomeres 3–9 subequal in width but varied in length and shape ( Fig. 1C ). Antennomeres 3–6 subequal in length, twice as wide as long; antennomere 1 transverse obconical with distinct pedicel, 4–6 transverse cylindrical with concealed pedicels. Antennomeres 7–9 subequal in length, 1.5× as wide as long; antennomere 7 roundedcylindrical, 8 and 9 weakly obconical. Ovoid club formed by antennomeres 10 and 11 ( Fig. 1C ); club at maximum width 3× wider than antennomeres 3–9. Antennomere 11 approximately 1.5× as long as 10. Segments of antennal club, especially antennomere 11, decorated in long, dense sensory setae (preceding antennal segments without discernable setation) ( Fig. 1C ). Estimated length of antenna 0.19 mm. Maxillary palpi ( Fig. 1B ) with short palpomere 1 and enlarged, clavate palpomere 2. Palpomere 3 broadly triangular in lateral view, twice as long as wide and approximately two thirds palpomere 2 length, with narrow, elongate, apically globose tubercle emerging dorsally at ~2/5 palpomere length ( Fig. 1B, D ). Palpomere 4 rounded-conical in shape, ~0.5× palpomere 3 length, dorsally bearing narrow, elongate, apically globose tubercle similar to that emerging from palpomere 3 ( Fig. 1B, D ). Apex of palpomere 4 bearing prominent 5th apical pseudosegment ( Fig. 1B ). Estimated length of extended maxillary palpus 0.18 mm. Mandibles prominent, narrow, sickle-shaped, apparently raptorial ( Fig. 1B ).

Thorax

Pronotum with rounded margins, widest in apical half. Pronotum 0.14 mm long, approximate width at widest point 0.2 mm.

Abdomen

Ventral abdomen length along midline 0.29 mm ( Fig. 1A ). Width at widest point (along apical margin of tergite IV) 0.27 mm. Tergites and sternites largely glabrous, but basal sulcus of sternite IV with apparent patch of dense, short (possibly squamous) setae.

Legs

Femora and tibiae of all legs thickened in apical half; lacking cuticular modifications. Tibiae apically setose on ventral face, most prominent on protibia. Tarsi ventrally with sparse, long mechanosensory setae. Lengths of leg segments: profemur 0.18 mm, protibia 0.13 mm, protarsus 0.07 mm, mesofemur 0.16 mm, mesotibia 0.14 mm, mesotarsus 0.06 mm, metafemur 0.16 mm, metatibia 0.16 mm, metatarsus 0.07 mm.

Elytra

Elytral length along margin 0.23 mm ( Fig. 1A ). Elytra apparently glabrous.

Figures

FIGURE 1. Yprezethinus grimaldii Holotype AMNH Tad-130. A, Habitus with visible abdominal sternites labelled. B, Head and pronotum with segments of maxillary palpomeres numbered (MP2–MP4). Bythinoplectina-type lateral excavation, eye, apical pseudosegment of maxillary palp (APs) and mandible (Md) indicated. C, Right antenna with antennomeres numbered. Note the club formed from tightly appressed, hemisphere-shaped antennomeres 10 and 11. D, Close-up view of apically globose tubercles of maxillary palpomeres 3 and 4. E, Proximal leg articulation, showing conically projecting metacoxa (MC), short metatrochanter (MT) and femur (F). F, Right metatarsus (F) with bythinoplectine-type enlarged third tarsomere spanning distance between arrowheads, and minute first visible tarsomere.