Principiala

''Principiala'' is an extinct genus of lacewing in the moth lacewings family Ithonidae. The genus is known from Cretaceous fossils found in South America, Europe, and possibly Asia. The genus is composed of two species, the type species ''Principiala incerta'', and ''Principiala rudgwickensis''.

History and classification

''Principiala'' is known only from three fossils assigned to the two species and an additional fossil tentatively assigned to the genus. The holotype adult of ''P. incerta'', specimen number SMNK PAL 5352 is housed in the collections of the State Museum of Natural History Stuttgart, while the partial paratype adult, specimen number SMNS 66000/255, is part of the State Museum of Natural History Karlsruhe, Germany. The specimens are preserved as compression fossils in finely laminated siltstones, which were recovered from outcrops of the Nova Olinda Member of the Late Aptian Crato Formation in Northeastern Brazil. ''P. rudgwickensis'' was described from a single part and counterpart holotype, "BMB 025005, -6" that is part of the Booth Museum of Natural History in Brighton and Hove, England. The species is older than ''P. incerta'', having been recovered from Rudgwick Brickworks which mined sediments of the Barremian Upper Weald Clay Formation. A single wing has been recovered from the Yixian Formation in China which was noted as probably belonging to the genus by Makarkin ''et al'' in 2012.

The Brazilian fossils were first studied by the paleoentomologists Vladimir N. Makarkin of the Far Eastern Branch of the Russian Academy of Sciences and Federica Menon from the University of Manchester in England. Their 2007 type description of the new genus and species was published in the journal ''Cretaceous Research''. The genus name ''Principiala'' was coined by the researchers as a combination of "Principi", in honor of Italian entomologist Maria Principi and the Latin word ''ala'' meaning "wing". The specific epithet "incerta" is derived from the Latin ''incertus'', in reference to the uncertain relationship of the genus within Ithonidae.

Two years later a group of researchers led by paleoentomologist James Jepson described the second species ''P. rudgwickensis''. The team chose the species name "rudgwickensis" as a reference to the Rudgwick Brickworks where the fossil was found.

Overall the vein structure of ''Principiala'' is most similar to the genus ''Allorapisma'', known from Ypresian fossils found in the northwestern United States. The wings of both genera show the apical end of the Rs vein fused to the MA vein. Both have similar positioning and shaping of the MP vein and the CuA vein running parallel to the MP vein. As such, Makarkin and Archibald suggested the two be grouped in an informal suprageneric group called the ''Principiala'' group. This group is one of three possibly monophyletic groups in Ithonidae, the others two being the ''Ithone'' group and the ''Rapisma'' group.

Description

The genus is identified by the short length of the antennae. Being approximately long, they are the shortest of the described neuropterans, with ''Rapisma'' having the shortest of the extant genera. The costal region of the fore-wing shows a regular series of cross-veins which gives the appearance of a longitudinal vein in the base area of the region. In contrast to the cross-veins of the costal area, the cross-veins in the subcostal area of the fore-wing are there are irregularly spaced and uneven. The area between the radius and median veins is notably narrow near the fore-wing base, and narrows towards the wing tip until the two veins merge. As with many Ithonidea genera, the head is pulled most of the way under the pronotal shield. ''P. incerta'' and ''P. rudgwickensis'' are distinguished by the characters of the species fore-wings, with an approximate length of for the former and only an estimated in the latter. In addition the last branch of the Rs vein in ''P. rudgwickensis'' is distinctly longer than that seen in ''P. incerta'' before the branches merge with the Median vein. ''P. rudgwickensis'' also shows a number of crossveins between the Rs branches of the Radial vein and the tip sections of the Rs branches are straight, both features absent or not preserved in ''P. incerta''.

References

{{Taxonbar, from=Q7553270

Ithonidae
Cretaceous insects
Insects of South America
Early Cretaceous animals of South America
Cretaceous Brazil
Fossils of Brazil
Crato Formation
Prehistoric insects of Europe
Cretaceous insects of Asia
Fossil taxa described in 2007
Fossil taxa described in 2009