Le site où le spécimen a été trouvé, Archingeay, correspond à un niveau d’argiles sableuses de Charente-Maritime, dans le Sud-Ouest de la France. Ce site a fourni un nouveau gisement à ambre et végétaux fossiles. Daté de l’Albien terminal par les dinoflagellés (± 100 Ma), ce gisement d’ambre devient le plus ancien site français fossilifère. Plusieurs inventaires des arthropodes trouvés dans l’ambre, les déterminations xylologiques et palynologiques et l’étude sédimentologique du gisement sont en cours (A. Nel, in litt.). Les premiers résultats permettent déjà de proposer une reconstitution paléoenvironnementale de la zone côtière du Nord du bassin d’Aquitaine à la fin du Crétacé inférieur : un milieu estuarien sous climat chaud et humide [7].

Scorpions are rare among the Arthropods fossilised in amber. Nevertheless, several specimens have recently been described from Dominican, Mexican and Baltic amber [3], [4] and [5]. Even though some of these descriptions may require amendment, there is little doubt that the amber fossils found in Hispaniola and Mexico are closely related to the extant Buthidae of the Caribbean and Neotropical regions. The position of the Baltic amber scorpions is somewhat different, because the known specimens, which also belong to the family Buthidae, can be classified among some extant but primitive lineages of micro-buthids. Five of these specimens have been described in recent years and represent distinct new genera that are related only approximately to extant groups. They are almost certainly primitive micro-buthids [3], [4] and [5]. The history of the study of amber scorpions, particularly those from the Baltic region, is complex. It has been described in detail by Lourenço & Weitschat [3], [4] and [5].

Two remarkable scorpion fossils have recently been described from Cretaceous amber. The first was found in Lebanese amber [1], which is the oldest known to contain biological fragments (±125/130 Myr). A new family, Archaeobuthidae Lourenço, was created for this specimen, which belongs to the Buthoidea. Cretaceous amber scorpions are much less common than those found in Baltic, Mexican or Caribbean amber. The type specimen of Archaeobuthus estephani Lourenço is not only the first Lebanese amber scorpion to have been discovered, but is undoubtedly the oldest scorpion found in amber of any kind (±125/130 Myr). The fossil scorpion found in Burmese amber [2] is the second oldest amber fossil so far discovered (±90 My). Only Archaeobuthus estephani from Lebanon is older. A new genus Palaeoburmesebuthus Lourenço, was created for this specimen, which was also tentatively classified among the Buthoidea, although for the moment it is regarded as Incertae familiae.

The specimen described in the present study is the first fossil scorpion to have been found in French amber. It is also the second oldest amber fossil so far discovered (±100 Myr). A new family, genus and species are required for it. For the first time, a fossil scorpion has been found in amber that is not associated with the buthoid scorpions. In fact, this new fossil family rather represents a proto-element to the extant chactoids, sensu Soleglad & Sissom [8].

The specimen investigated is trapped in a very clear block of pale yellow amber that measures 9 × 5 mm. It has been embedded in apoxy under vacuum [6]. The scorpion is incomplete, since the block of amber had been broken. Only the left pedipalp with patella and tibia are present. Both sides of the pedipalp are clearly visible, however, and allow detailed investigation.

The specimen was collected from a layer of clay interbedded in sandstone at Archingeay, Charente-Maritime (southwestern France). This site has yielded new deposits of amber as well as fossil plants. The age of the site can be dated as Uppermost Albian by the presence of dinoflagelates (±100 Myr). A survey of the arthropods found in amber from this site is in progress, together with xylological, palynological and sedimentological studies (A. Nel, in litt.). Preliminary results allow a palaeoenvironmental reconstruction of the coast of the northern Aquitaine Basin at the end of the Lower Cretaceous as an estuarine area with a warm and humid climate [7].

Superfamily Chactoidea Pocock, 1893

Family Palaeoeuscorpiidae fam. n.

Diagnosis

Total length probably about 25 mm, based on the length of the pedipalp segments. These are as follow, in mm: Tibia length, 6.11; chela width, 1.81, depth, 1.36. Patella length, 3.32, width, 1.71, depth, 1.37. In comparison, an adult specimen of Euscorpius flavicaudis (Euscorpiidae) from France, with a total length of 25.7 mm, shows the following values: tibia length, 6.21; chela width, 2.90, depth, 1.80; patella length, 3.31, width, 1.70, depth, 1.31.

The general morphology of the pedipalp segments is somewhat similar to that of a few chactoid genera but is closer to that of extant species of the genus Euscorpius. The main difference is its strong flattened appearance. The new family and genus can be distinguished from other known chactoid families and genera by its unusual trichobothrial pattern. This is similar to type C of Vachon [9], but with a much reduced number of trichobothria, in particular on the external aspect of patella (six trichobothria). According to Vachon [9], the fundamental trichobothrial pattern of type C (orthobothriotaxy) always presents a minimum of 13 trichobothria on the external aspect of patella, and, in the case of exceptions (major neobothriotaxy), this number is always higher.

Genus Palaeoeuscorpius gen. n.

Diagnosis: as for the new family.

Type species: Palaeoeuscorpius gallicus gen. n. et sp. n.

Palaeoeuscorpius gallicus gen. n. et sp. n. (Fig. 1–4 and Fig. 5–9)

Holotype: a possible adult (sex unknown). Deposited in the ‘Laboratoire de paléontologie’, ‘Muséum national d’histoire naturelle’, Paris (specimen No. ARC236-2/5).

Type locality and horizon: France, Charente-Maritime. Upper Cretaceous.

Diagnosis: as for the new family and new genus.

Derivatio nominis: the specific name makes reference to France, the country where the fossil specimen was found.

Coloration: the general colour is yellowish. The amber is very clear, but numerous air bubbles are present; no parts of the specimen are covered with the milky white substance, which often prevents more precise observation of coloration.

Morphology (Fig. 1–4 and Fig. 5–9). Carapace, keels and furrows unknown. Median ocular tubercle and lateral eyes unknown. Sternum unknown. Mesosoma: tergites I to VII unknown. Venter: genital operculum, pectines and sternum unknown. Sternites and spiracles unknown. Metasoma: unknown. Telson unknown. Cheliceral dentition unknown. Morphology of pedipalps: both tibia and patella very flattened; dentate margins of pedipalp-tibia fingers with a single linear row of granules, without accessory granules. Tibia with two dorsal and two ventral carinae; patella with one internal apophysis and with two dorsal, one external and two ventral carinae. Trichobotriotaxy: the following trichobothria can be observed with precision (patella, four on dorsal aspect, one on the internal aspect, five on dorso-external aspect, six on external aspect and 14 on the ventral aspect). Tibia, four on dorsal aspect of chela, two on the base of the fixed finger, two on the dorso-external aspect of chela, three on the ventral aspect of chela and one on the ventro-external aspect of chela. Morphology of legs: unknown (Figs. 10–12).

According to some of the characters mentioned in the description – shape of pedipalp tibia and patella, presence of an apophysis on the internal aspect of patella, and especially the trichobothrial pattern observed – the specimen is unquestionably a member of the Chactoidea, sensu Soleglad & Sissom [8]. The possible assignment to any of the extant chactoid families at present accepted is, however, rejected on account of the very reduced trichobothrial pattern observed (minor neobothriotaxy), the incompleteness of the specimen and in particular on account of the geological horizon (Lower Cretaceous). The specimen is therefore assigned to a new family Palaeoeuscorpiidae until further material becomes available.

The discovery of this fossil is important in the sense that is represents the first non-buthoid element ever found in amber. Moreover, it may represent one element living on litter rather than an arboricolous element. In fact, according to A. Nel (in litt.), several other typical litter insects have been found in this site, suggesting that fairly large amounts of resin flowed directly onto to the soil.

With regard to extant chactoids, the new family lies at a low evolutionary level. As in the case of the Cretaceous buthoids [1] and [2], this suggests that several extant groups may have evolved since the Late Mesozoic and Early Cenozoic.