The Eoblattodea, or 'roachoids' form a stem group to the living Dictyoptera, which comprises the Cockroaches, Mantises, and Termites (a stem group contains fossil species more closely related to the living group they are on the 'stem' of than to any other living group, but not descended from the last common ancestor of all living members of that group). This stem group first appeared in the Carboniferous, with the common ancestor of all living Dictyopterans probably living in the Jurassic. The Subioblattids are a small group of 'roachoids' known from the Triassic of South Africa, France, and Central Asia. This group is fairly well-known from its forewing anatomy (the forewings are considered to be reliable on their own for the diagnosis of Insect relationships), but to date no body fossils found to date.
In a paper published in the Swiss Journal of Palaeontology on 10 March 2025, Matteo Montagna of the Department of Agricultural Sciences at the University of Naples Federico II, Fabio Magnani of the Museo Cantonale di Storia Naturale, Giulia Magoga, also of the Department of Agricultural Sciences at the University of Naples Federico II, and André Nel of the Institut de Systématique, Évolution, Biodiversité at the National d’Histoire Naturelle, describe a new species of Subioblattid 'roachoid' from the Middle Triassic of Monte San Giorgio fauna of Switzerland.
The Monte San Giorgio fauna derives its name from Monte San Giorgio, a mountain on the border between Italy and Switzerland in the Lugano Prealps. The exposed geological sequence on this mountain begins in the Lower Permian, where a succession of volcanic rocks mark the onset of the Variscan Orogeny, as the continents of Euramerica and Gondwana collided during the formation of the supercontinent of Pangea. These are overlain by a sequence of Triassic sediments recording a tropical terrestrial environment, a shallow near-shore environment, a deeper marine basin with extensive limestone deposits, a second terrestrial exposure caused by a major marine regression (drop in sealevel) in the Late Triassic, and finally an Early Jurassic marine Basin.
The fossils of the Monte San Giorgio fauna come from shales of the Besano Formation and the overlying Meride Limestone, which were laid down in the Early-Middle Triassic marine basin. These fossils include Bivalves, Marine Reptiles, Fish, Crustaceans, and Cephalopods, as well as terrestrial-derived fossils such as Plants, terrestrial Vertebrates, and Insects. To date, 273 species of Insect have been recorded from Monte San Giorgio, including Thrips, True Bugs, and Flies, as well as representatives of groups such as the Monura and Permithonidae, which were thought to hve died out in the End Permian Extinction until they were discovered here.
The new species is described from a single specimen from Meride Limestone of Monte San Giorgio. This is placed in the genus Samaroblattella on the basis of its forewing veination, but assigned to a new species, valmarensis, meaning 'from Val Mara' in reference to the location where the fossil was found.
The genus Samaroblattella was first described in 1976 to describe a fossil from South Africa, with a second species described from Kazakhstan, Central Asia, in 2001. Unlike these previously described species, and indeed all other previously described members of the roachoid family Subioblattidae, to which the genus is assigned, Samaroblattella valmarensis has a preserved body as well as wings.
The hind legs of Samaroblattella valmarensisi closely resemble those of the extant Jumping Cockroach, Saltoblattella montistabularis, with both species also having an elongate shape, and a narrow pronotum (plate on the forepart of the prothorax, before the wings) suggesting that this ancient roachoid may have had a similar jumping habit.
However, a close relationship is not proposed, as Samaroblattella valmarensisi also has an elongated, sword-like, external ovipositor, something absent from crown group Dictyopterans (ctown group comprises all species deecended from the last common ancestor of all living species), which have an internal ovipositor. External ovipositors were found in the earliest Insects, with internal ovipositors having appeared separately several times in different groups.
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