Tuesday, June 2, 2020

[PaleoEntomology • 2020] Merothrips aithiopicus • Two Fossil Thrips from Ethiopian Amber (Thysanoptera: Merothripidae) with Description of A New Species

Merothrips aithiopicus 
Ulitzka. 2020. 

Amber has rarely been found in Africa and only a few samples with fossil inclusions are known (Kiefert et al. 2015). The most important fossiliferous find was reported from an outcrop at the north-western Plateau of Ethiopia a decade ago, revealing diverse inclusions of arthropods, plant remains, fungi and microorganisms (Schmidt et al. 2010). Initially, this amber was classified as originating from the mid-Cretaceous. Later studies, however, have raised questions about this determination and indicated a much younger age: Cenozoic, likely Miocene (Coty et al. 2016, Perrichot et al. 2016, Perrichot et al. 2018). The contradictory—and rather controversial discussed—new dating was based on spectroscopic analyses, revised palynological data and more comprehensive palaeoentomological results showing that insect fossils mostly belong to extant families and genera. In total, Schmidt et al. (2010) reported 22 insects from eight identified orders including two specimens of Thysanoptera: “an undetermined, wingless thrips“ (obviously a larva) and a female associated with Merothripidae. A more detailed analysis of these specimens is the objective of the present study; regarding the larva, only a rough classification and description is given, as fossil larvae cannot be definitely associated with adult specimens.

FIGURES 1–7. Ethiopian amber fossils. Merothrips aithiopicus sp. n. holotype female 1–4: (1) dorsal view; (2) head, prothorax and metathorax (sa- sensory areas; soc- ocellar setae s3; spo- postocular setae; spa- pronotal posteroangular setae; sco- coxal setae); (3) left fore wing (cross vein indicated); (4) abdominal segments VII–X (spiracles indicated white, trichobothria indicated black). Thripidae, cf. Scirtothrips, female second instar larva 5–7: (5) dorsal view; (6) imprint of caudal abdominal segments (d1–d3- dorsal setae; sl- lateral seta; v1–v2- ventral setae); (7) right antenna.

Merothrips aithiopicus sp. n.  

Diagnosis. Even though the pair of lobes on the posterior margin of the seventh abdominal sternite is not visible the form of the antennal sensoria (fig. 2), the presence of trichobothria on abdominal tergite X (fig. 4), the shape of the wings with pointed tips (fig. 3) as well as the enlarged fore femora (figs 1, 2) indicate that the new species is attributable to Merothripidae. Species associated with this family usually have nine-segmented antennae, apart from members of Merothrips Hood, which have eight antennomeres. The classification of the new species into this genus is also supported by the trapezoidal pronotum, the wing venation and the chaetotaxy of the wing scale (c.f. Bhatti 2006; Mound & O’Neill 1974).

Etymology. The species epithet aithiopicus derives from the classical Greek word Αιθιοπία (Aithiopia), the ancient geographical name for a historic region in Africa, which included Ethiopia, the country where the amber deposit is located. 

It is not the main purpose of the present study to review the age of Ethiopian amber, but nevertheless the findings may provide some clues in this regard. M. aithiopicus sp. n. is related within the Merothripidae to a genus, which dates back to the Palaeogene and which still exists in the extant fauna. Similarly, the larva associated with Thripidae at least belongs to a family also showing large diversity only since the Paleogene. Even if members of both families are known since the Cretaceous (Nel et al. 2010, Shmakov 2009, Ulitzka 2018), the fossils examined here resemble rather modern species and may indicate that the amber was formed in a later era.

Manfred R. Ulitzka. 2020. Two Fossil Thrips from Ethiopian Amber (Thysanoptera) with Description of Merothrips aithiopicus sp. n. (Thysanoptera: Merothripidae). Zootaxa. 4786(2); 283–288. DOI: 10.11646/zootaxa.4786.2.10