Braconid Wasps are the second largest group of extant Hymenopterans (the group that includes all Wasps, Ants, Bees, and Sawflies), and are the sister group to the Ichneumonidae, the largest Hymenopteran group, with the two forming the Superfamily Ichneumonoidea. Both groups are parasitoids (i.e. their larvae are parasites which grow inside the bodies of other Animals, generally killing the host as they grow, but their adult stages are free-living), targeting a wide range of terrestrial Arthropod species. The Ichneumonoids have been around since at least the Early Cretaceous, although Cretaceous fossils of these Insects are not particularly common. One noteworthy group of early Braconids is the Protorhyssalinae, which is known only from Albian (113-100.5 million years ago) to the Campanian (83.6-71.2 million years ago) deposits, chiefly as inclusions within amber.
In a paper published in the journal ZooKeys on 30 May 2022, Sergio Álvarez-Parra of the Departament de Dinàmica de la Terra i de l’Oceà and Institut de Recerca de la Biodiversitat at the Universitat de Barcelona, Enrique Peñalver of the Instituto Geológico y Minero de España, Xavier Delclòs, also of the Departament de Dinàmica de la Terra i de l’Oceà and Institut de Recerca de la Biodiversitat at the Universitat de Barcelona, and Michael Engel of the Division of Entomology at the Natural History Museum of the University of Kansas, the Department of Ecology and Evolutionary Biology at the University of Kansas, and the Division of Invertebrate Zoology at the American Museum of Natural History, describe a new species of Protorhyssaline Braconid Wasp from Early Cretaceous San Just Amber from the Maestrazgo Basin of eastern Spain.
The Maestrazgo Basin contains about 30 amber-producing outcrops, although amber with fossil inclusions is known from only four of these. The San Just outcrop produces amber clasts from a layer of organic-rich grey-black marls, which have been assigned to the Escucha Formation. This deposit is thought to have accumulated in a freshwater swamp plain, and has been dated to the upper Albian, based upon pollen inclusions in the amber. Twenty five species of Arthropod have previously been described from San Just Amber.
The new species is named Utrillabracon electropteron, where 'Utrillabracon' is a combination of Utrillas, the municipality in which the San Just outcrop is found, and '-bracon' for Braconid, while 'electropteron' means 'amber-wing'. The species is described from a single poorly preserved specimen, MAP-7819 (SJE2012 49-04), comprising the wings, head, and a single forelimb of the Wasp.
While this material is very fragmentary, the wings of Insects are considered to be extremely useful taxonomically, with the veination typically unique at species level, but sufficiently similar within groups to allow the taxonomic placement of species. The veination of the wings of specimen MAP-7819 (SJE2012 49-04) is unlike that of any previously described species, but contains features which enable its confident placement within both the Protorhyssalinae and the Braconidae, notably the presence of veins Rs and M and absence of vein 2m-cu in the forewing, and the rs-m vein being proximal to the bifurcation of veins R1 and Rs in the hindwing, all traits diagnostic of Braconids, and the presence of a pentagonal (five-sided) second submarginal cell in the forewing and the presence of vein 2Cu in the hindwing, which are traits considered diagnostic of the Protorhyssalinae.
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