A new Myrmecarchaea (Araneae: Archaeidae) species from Oise amber (earliest Eocene, France)

Abstract

Extant Archaeidae, also known as pelican or assassin spiders, have an Austral distribution (South Africa, Madagascar and Australia), but were present in Eurasia during the Mesozoic and Cenozoic, as attested by fossils from Cretaceous Burmese amber (Ross A. 2019. Burmese (Myanmar) amber checklist and bibliography 2018. Palaeoentomology 2(1): 22–84) and Eocene European ambers (Wunderlich J. 2004. Fossil spiders in amber and copal: conclusions, revisions, new taxa and family diagnoses of fossil and extant taxa. Hirschberg-Leutershausen: Ed. Joerg Wunderlich, 1893 p.). They have been known to occur in Oise amber (Ypresian, early Eocene, MP7), from northern France. However, they are not abundant in Oise amber, and have been the subject of few studies until now. Here, we describe the only well-preserved, almost complete, archaeid fossil specimen. This adult male is described as Myrmecarchaea antecessor sp. nov, based on the presence of unique morphological features. The elongate petiolus and extremely long legs are characteristic of the genus Myrmecarchaea from the Middle Eocene Baltic amber. However, unique traits such as the thick, stout petiolus and the extremely elongated, posteriorly tapering cephalothorax distinguish it from the other species of Myrmecarchaea. This specimen is of high interest, as besides being a new species, it is also the first documented adult male in the genus, allowing us to observe sexual characters for the first time. Furthermore, it is the first occurrence of this genus outside Baltic amber, showing affinities between Oise and Baltic ambers, which are, otherwise, very different in their faunistic compositions, and further extends the known past range of the archaeid spiders.