Cretomophron Rosova, Prokop & Beutel, 2023

Rosova, Katerina, Prokop, Jakub, Hammel, Joerg U. & Beutel, Rolf G., 2023, The earliest evidence of Omophroninae (Coleoptera: Carabidae) from mid-Cretaceous Kachin amber and the description of a larva of a new genus, Arthropod Systematics & amp; Phylogeny 81, pp. 689-704 : 689

† Cretomophron Rosova, Prokop & Beutel gen. nov.

Type species.

† Cretomophron mutilus Rosova, Prokop & Beutel, gen. et sp. nov. - sp. nov. by original designation and monotypy. - Included species. Type species only.

Diagnosis (larva).

The specimen described here differs from larvae of all holometabolan groups outside of Coleoptera and from Archostemata by the presence of distinctly developed urogomphi on abdominal tergite IX (Figs 1B , 4 ). It can be distinguished from all carabid groups outside of Omophroninae by a pronouncedly wedge-shaped head, antennae directed upwards (Fig. 3B ), and a laterally oriented terminal 4th antennomere (Figs 2A , 5A ). The prothorax appears proportionally larger than in other carabid larvae, but this is a gradual modification only. Additional unusual diagnostic features are the large triangular nasale (Figs 1A , 5A ), antennae with the 2nd antennomere markedly elongated, legs with a very short tibia and long setae UN1, UN2 on claws (Fig. 2D ), and abdominal segment VI with numerous setae collected in transverse rows (Figs 1A , 2B , 4 ), and large trochanters with distal projections (Figs 3B, C ). Posterior tentorial grooves not shifted to the posterior margin of the ventral head capsule distinguish it from larvae of Omophron (Figs 2A , 5B ).

Etymology.

The generic epithet combines ‘creto-’ (Latin for chalky as in Cretaceous), referring to the geological period, and ‘omophron’, the single extant genus of Omophroninae .

Figures

Figure 1. † Cretomophron mutilus Rosova, Prokop & Beutel, gen. et sp. nov.: A detail of head and mouthparts, dorsal view; B habitus, dorsal view; C abdominal segment VI, dorsal view. Scale bars: (A) 0.1 mm, (B) 0.8 mm, (C) 0.2 mm. Abbreviations: an - antenna, ga - galea, lc - lacinia, nas - nasale, pl - labial palpus, pmx - maxillary palpus, ste - stemmata.

Figure 2. † Cretomophron mutilus Rosova, Prokop & Beutel, gen. et sp. nov.: A head and mouthparts, ventral view; B mesothoracic leg, ventral view; C volume render of prothoracic leg from the segmented SRµCT data, lateral view; D detail of the pretarsus of the metathoracic leg. Scale bars: (A, B) 0.2 mm, (C) 0.8 mm, (D) 0.1 mm. Abbreviations: an - antenna, c - cardo, ga - galea, lc - lacinia, pl - labial palpus, pmt - prementum, pmx - maxillary palpus, ptg - posterior tentorial bridge, sa - sensorial appendage.

Figure 3. † Cretomophron mutilus Rosova, Prokop & Beutel, gen. et sp. nov., volume renders of the segmented SRµCT data: A dorsal view, B lateral view, C ventral view. Scale bar 0.8 mm.

Figure 4. (A) Habitus of † Cretomophron mutilus Rosova, Prokop & Beutel, gen. et sp. nov., dorsal view. Dashed lines show missing or poorly visible structures. Scale bar 0.8 mm; (B) Habitus of larva of Omophron limbatum (Fabricius, 1776), adapted from Luff 1993, modified.

Figure 5. † Cretomophron mutilus Rosova, Prokop & Beutel, gen. et sp. nov.: A head, dorsal view, chaetotaxy simplified; B head, ventral view; C abdominal segment VI, dorsal view. Dashed lines show missing or poorly visible structures. Scale bars 0.4 mm. Abbreviations: an - antenna, c - cardo, co - coronal suture, f - frontal suture, ga - galea, lc - lacinia, md - mandible, nas - nasale, pl - labial palpus, pmt - prementum, pmx - maxillary palpus, ptg - posterior tentorial bridge, sa - sensorial appendage, st - stipes, ste - stemmata.