Two new species of Archelcana Sharov (Orthoptera: Elcanidae) from the Lower Jurassic of Luxembourg

: Two new species of the genus Archelcana Sharov (Orthoptera: Elcanidae: Archelcaninae) are described from the Toarcian (Lower Jurassic) deposits of Uerschterhaff, near Sanem, southern Luxembourg. Archelcana numbergerae sp. nov. and Archelcana tina sp. nov. are the first fossil insects to be formally described from the Uerschterhaff locality and the first fossil orthopterans from the Lower Jurassic of Luxembourg.


Introduction
Familiar and ubiquitous today, grasshoppers and crickets (Orthoptera) were already a diverse and important component of terrestrial ecosystems by the Early Jurassic. One of the most diverse and recognizable orthopteran clades of the Mesozoic are the Elcanidae, a group of grasshopper-like insects characterized primarily by their unique tegminal venation and the presence of prominent spurs on the metatibiae (Zessin 1987;Gorochov 1995;Heads et al. 2018). Despite a long and rich fossil record spanning the Triassic to the Paleocene, a precise phylogenetic placement for the elcanids has remained elusive Fang et al. 2018a,b;Schubnel et al. 2020). Their superficial resemblance to tettigonioids, with long antennae and well-developed, sword-like ovipositors, led many authors to assign them to Ensifera (Ander 1939;Zessin 1987;Gorochov et al. 2006), though these characters are almost certainly plesiomorphic among orthopterans. Other work based on tegminal venation has suggested relationships with or within Caelifera Béthoux & Nel 2001) or a position at the base of Orthoptera (Martynov 1938;Ragge 1955;Gorochov & Rasnitsyn 2002). At the time of writing, the Orthoptera Species File Online (Cigliano et al. 2022) places the family within Ensifera, though this assignment is erroneous and will certainly change following a comprehensive revision and phylogenetic analysis. Elcanidae were divided into two subfamilies by Gorochov et al. (2006) based on the condition of the tegminal cubitoanal veins: the nominate subfamily, Elcaninae, comprising the genera Cratoelcana Martins-Neto, 1991 from the Lower Cretaceous of Brazil (Heads & Martins-Neto 2007), Ellca Kočárek, 2020from mid-Cretaceous Burmese amber, Eubaisselcana Gorochov, 1986 from the Lower Cretaceous of Mongolia, Minelcana Gorochov, Jarzembowski & Coram, 2006 from the Lower Cretaceous of England, Panorpidium Westwood, 1845, definitively known only from the Lower Cretaceous of England, Eastern Europe, and Asia (see discussion below), and Probaisselcana Gorochov, 1989 from the Upper Jurassic of Kazakhstan and the Lower Cretaceous of England and China (Gorochov 1989;Tian et al. 2019a); and the arguably more primitive subfamily Archelcaninae, comprising the genera Archelcana Sharov, 1968 from the Lower Jurassic of England, Russia, and Uzbekistan   (Ren 1998;Peñalver & Grimaldi 2010;Heads et al. 2018). Longioculus Poinar, Gorochov & Buckley, 2007 from mid-Cretaceous Burmese amber is known only from a partially preserved adult in which the cubitoanal region of the tegmen is incomplete, preventing confident subfamilial assignment (Poinar et al. 2007). Similarly, the recently described and only Cenozoic elcanid, Cenoelcanus Schubnel, Desutter-Grandcolas, Garrouste, Hervey & Nel, 2020 from the Paleocene of France is known only from a single, incomplete tegmen lacking the cubitoanal region (Schubnel et al. 2020). The genera Elcanopsis Tillyard, 1918 from the Permi-Triassic of Australia, and Macrelcana Karny, 1932 from the Lower Miocene of Croatia are, at the time of writing, included in Elcanidae in the Orthoptera Species File Online (Cigliano et al. 2022) apparently following Jell (2004) and Cadena-Castañeda (2019) respectively. Both of these genera are of unknown affinity and require detailed redescription, though are certainly not elcanids in that neither possess the close association of RP with the stem of M+CuA that is synapomorphic of Elcanoidea sensu Gorochov & Rasnitsyn (2002).
The genus Archelcana Sharov, 1968 presently comprises four species: the type species Archelcana britannica  and Archelcana durnovaria , both from the Lower Jurassic of England , Archelcana ornata Zherikhin, 1985 from the Lower Jurassic of Kyrgyztan, and Archelcana shurabica  from the Lower Jurassic of Uzbekistan. Here, we describe two new species of Archelcana from the Toarcian of Luxembourg and briefly discuss the taxonomy of the Jurassic elcanids of Europe pending their comprehensive revision.

Material and Methods
The specimens described herein were collected during fieldwork led by the National Museum of Natural History Luxembourg (MnhnL) between 2018 and 2021 at a site called Uerschterhaff near Sanem in southern Luxembourg (Figure 1). Construction works for a new prison temporarily exposed a succession of uppermost Pliensbachian marls and claystones, and lower Toarcian bituminous shales and limestone nodules. All the specimens were retrieved from a single layer of flat, finely laminate bituminous limestone nodules, several decimeters in diameter and approximately 10 cm thick. The nodules yield abundant shells of the small gastropod Coelodiscus Brösamlen, 1909. Other fossils include, in decreasing abundance, isolated bones and partly decomposed skeletons of the small teleost fish Leptolepis Agassiz, 1843, plant fragments, ammonites, decapod crustaceans, and coleoid cephalopods.
Ammonites found in the limestone nodules date the insect fossils to the Exaratum subchronozone, Serpentinum chronozone, lower Toarcian (sensu Page 2003). Similarities in stratigraphic position, lithofascies, and fossil content suggest that the insect-yielding nodule bed at Sanem is a lateral equivalent, if not direct continuation of, the nodule bed that yielded the rich insect assemblage from nearby Bascharage (Nel, 1989;Nel et al. 1993Nel et al. , 1994Henrotay et al. 1997Henrotay et al. , 1998Delsate et al. 1999) and other sites in southern Luxembourg (Nel et al. 2017) and adjacent parts of Belgium (Delsate et al. 1992).
The insect-bearing nodule bed exposed at Sanem was deposited in a quiet sublittoral setting near the southeastern shore of the emergent London-Brabant landmass (Thuy & Numberger-Thuy 2021). During the lower Toarcian, the area was part of the northeastern Paris Basin and the sediments deposited are comparable to the Posidonia Shale of southwestern Germany (Hermoso et al. 2014).
All specimens are deposited in the fossil collection of the Department of Palaeontology at the National Museum of Natural History Luxembourg (NMNHL) in Luxembourg City. Photographs were made using a Keyence VHX-6000 both dry and under ethanol. Drawings were made using Adobe Illustrator 2021. Vein abbreviations are as follows (from anterior to posterior): CP, posterior costa; ScA, anterior subcostal; ScP posterior subcostal; RA, anterior radius; RP, posterior radius; MA1 and MA2, first and second branches of anterior media; MP, posterior media; CuA, anterior cubitus; CuPaα, anterior branch of first posterior cubitus; CuPaβ, second branch of posterior cubitus; AA1, first branch of first anal.

Discussion
Elcanidae are one of the most common and diverse orthopteran families of the Lower Jurassic of western Europe, though they remain poorly studied. Handlirsch ( , 1939 described some 67 species, all of which he placed in the waste-basket genus Elcana. Following the synonymization of Elcana with  Panorpidium (see Gorochov et al. 2006), all of Handlirsch's species were transferred to the latter genus, where the vast majority are currently considered synonyms in Orthoptera Species File Online (Cigliano et al. 2022). However, when revising the Early Cretaceous Orthoptera of southern England, Gorochov et al. (2006) noted that P. tessellatum and other Panorpidium species possess a unique distal fusion of veins in the cubitoanal region of the tegmen; a diagnostic character of the Elcaninae. This distal fusion is not present in the Archelcaninae, in which CuPaβ, CuPb, and the anal veins remain largely parallel to each other and are free distally (i.e. not fused). The former condition is typical of Early Cretaceous members of Panorpidium (e.g. P. bimaculatum, P. minutum, P. parvum, P. proximum, P. tessellatum) and other elcanine genera (Cratoelcana, Eubaisselcana, Minelcana, and Probaisselcana). In contrast, none of the species described in Elcana by Bode (1905) Germar (1842, Giebel (1856), Handlirsch ( , 1939, and Heer (1865Heer ( , 1880 from the Lower Jurassic of Western Europe possess this condition, indicating that they are archelcanines and thus, incorrectly placed in Panorpidium. Of these 79 species, only 15 are currently considered valid in the Orthoptera Species File Online (Cigliano et al. 2022): P. angustior (Handlirsch, 1939), P. beyrichi (Giebel, 1846), P. deichmuelleri , P. geinitzi (Heer, 1880), P. liasinum (Giebel, 1846), P. lithophilum (Germar, 1842), P. longicorne , P. magnum , P. medium , P. mesostenum (Handlirsch, 1939), P. minimum , P.
oppenheumi , P. phyllophorum , P. reticulatum (Handlirsch, 1939), and P. westwoodi . Given their obvious generic and subfamilial misplacements, all of the European Lower Jurassic elcanids require comprehensive revision, and while many resemble Archelcana, we refrain from reassigning them without having examined all available type material. It is possible, if not likely, that once such a revision is complete, Archelcana itself may be divided into several genera, but at present we consider it as comprising only the six species listed alongside all other archelcanine genera and species in Table 1. At present, the true scale of European Jurassic elcanid diversity remains unenumerated, but the description herein of two distinctive new species from the Toarcian of Luxembourg hints at the existence of a potentially rich assemblage across western Europe in the Early Jurassic. Table 1. List of genera and species currently included in the subfamily Archelcaninae (Elcanidae). Asterisks indicate type species for that genus.