Eoractocetus, Kirejtshuk, 2025

Genus † Eoractocetus gen. nov.

Type species: † Eoractocetus storozhenkoi sp. nov.; Upper Eocene Baltic amber .

Diagnosis. The list of the diagnostic characters represent mostly those that can be used for the comparison of the genus † Eoractocetus gen. nov. within other seven genera currently defined in fossils, for which lists with corresponding characters are also compiled with the same numeration of characters for more convenience.

List of diagnostic characters of the genus † Eoractocetus gen. nov. ( type species: † Eoractocetus storozhenkoi sp. nov., Eocene Baltic amber):

1. Body moderately narrow.

2. Head with strongly reduced postocular portion and with very short temples.

3. Antennae moniliform with antennomeres 3–6 thickest.

4. Apical maxillary palpomeres simple and palpomere 3 modified into maxillary palporgan;

5. Pronotum elongate and convex along the middle and with a narrow median depression along entire length, about 1.5 times as long as wide and widest at base, anterior angles not to scarcely expressed, anterior edge strongly convex, gently rounded and far projecting anteriorly, posterior angles strongly projecting posteriorly.

6. Scutellum transversely subtriangular to subpentangular and widely rounded at apex, with subcordiform median plate narrowed at base, slightly longer than wide and not reaching scutellar apex.

7. Prosternum along its middle about a third as long as mesoventrite.

8. Metaventrite more than 1.5 times as long as wide, with posterior edge strongly projecting posteriorly.

9. Metacoxae rather “narrow” (distance between anterior and posterior edges), strongly obliquely declined to apices, their subcontiguous parts comprising a third of entire metacoxal length.

10. Abdominal ventrite 1 between metacoxal apices and its posterior edge markedly shorter than each of other abdominal ventrites (2–5).

11. Female pygidium slightly narrowing posteriorly, more than 1.5 times as long as wide, subpentagonal and subacute at apex.

12. Female hypopygidium (ventrite 5) less than 1.5 times as long as wide, widely rounded at posterior edge.

Notes. This new genus seems to be rather closely related to Cretoquadratus Chen 2019 , Eoractocetinus gen. nov., Lymexylopsis gen. nov. and Paratractocerus Nazarenko et Perkovsky in Nazarenko et al. 2020 differering from all of them in the comparatively short postocular portion of epicranium, convex anterior part of pronotum far projecting anteriorly and covering the head base ( Fig. 5 View FIGURES 5–6 ), and also subcordiform plate on basal part of scutellum. The short prosternum along the middle in Eoractocetus storozhenkoi sp. nov. ( Fig. 10 View FIGURE 10 ) (something like that in Atractocerus Palisot de Beauvois, 1801 ) is a very distinct character from that in species of Eoractocetinus gen. nov., Lymexylopsis gen. nov. and Paratractocerus with rather long prosternum, while the prosternum of Cretoquadratus remains unknown. Besides, Cretoquadratus is very distinct from Eoractocetus gen. nov. in its very large head in comparison with prothorax, very narrow antennae, pronotum widest at the tips of the anterior angles and without narrow median depression, larger and clearly pentagonal scutellum with distinct median stripe along its entire length. In addition to the mentioned characters, the genus Eoractocetinus gen. nov. differs from Eoractocetus gen. nov. in the compressed antennomeres, subquadrangular pronotum without narrow median depression, and also in the posterior edges of metaventrite slightly oblique mesally, while the genus Lymexylopsis gen. nov. —in more or less arcuate pronotal sides, subquadrate scutellum with a wide median subparallel-sided stripe and abdominal ventrite 1 markedly longer than each of ventrites 2–4. Finally, the genus Paratractocerus is distinct from other fossil atractocerine genera in simple maxillary palpi with comparatively short palpomeres, and also, in addition to the above-mentioned features, the latter genus is distinguished from Eoractocetus gen. nov. in the pronotum without narrow median depression, and also in the abdominal ventrite 1 markedly longer than each of ventrites 2–4.