Abstract
Abstract. Paleoxyela nearctica gen. et sp. nov., is described from the upper Eocene of Florissant Formation in Colorado. We placed Paleoxyela gen. nov. in the subfamily Macroxyelinae and the tribe Macroxyelini based on the numerous wing venation characters visible on the specimen. Proxyelia pankowskii gen. et sp. nov. is described from the lower Eocene Fossil Lake deposits of the Green River Formation in Wyoming. We placed Proxyelia gen. nov. in the subfamily Macroxyelinae and the tribe Xyeleciini based on the numerous wing venation characters visible on the specimen. These new records of the family Xyelidae are of particular importance to better understand the past diversity of the clade and propose hypotheses about their diversification. Extant Xyelidae inhabit temperate Northern Hemisphere forests, and most of their larvae feed on conifers, which may explain why they are relatively poorly diversified compared to the other symphytan families. We suggest that the global decline in conifers and the reduced diversity of extant host trees partly explain the diversity of extant Xyelidae. We correlate the biome repartition during the Eocene to that of the extant xyelid.
Highlights
The “symphytan” superfamily Xyeloidea Newman, 1834, is broadly accepted as the earliest diverging clade within the crown group Hymenoptera (Ronquist et al, 2012), while a recent study rather suggested the Pamphilioidea as the earliest diverging clade (Peters et al, 2017)
Proxyelia pankowskii gen. et sp. nov. is described from the lower Eocene Fossil Lake deposits of the Green River Formation in Wyoming
The Florissant Formation has been dated at 34.07 Ma (Evanoff et al, 2001), and the fossil beds were deposited in a paleolake that was formed by the volcanoclastic debris flow damming of the drainage basin (McLeroy and Anderson, 1966; Evanoff et al, 2001)
Summary
The “symphytan” superfamily Xyeloidea Newman, 1834, is broadly accepted as the earliest diverging clade within the crown group Hymenoptera (Ronquist et al, 2012), while a recent study rather suggested the Pamphilioidea as the earliest diverging clade (Peters et al, 2017). The Xyeloidea currently comprise the Xyelidae Newman, 1834, and the †Syspastoxyelidae Engel and Huang, 2016 (Zheng et al, 2021a). The former comprises about 80 extant species distributed in five genera (Taeger et al, 2018). The fossil record of the Xyelidae is abundant, even if rather poorly documented. More than 80 Mesozoic species within 47 genera are currently attributed to Xyelidae (e.g., Rasnitsyn, 1964, 1969; Wang et al, 2012; Kopylov, 2014; Zheng et al, 2019a, 2021b). The Cenozoic record of the family is more reduced, with only 14 species known to date (Table 1)
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