Raphidioptera Navas 1916
- Dataset
- Early Eocene snakeflies (Raphidioptera) of western North America from the Okanagan Highlands and Green River Formation
- Rank
- ORDER
Classification
- kingdom
- Animalia
- phylum
- Arthropoda
- class
- Insecta
- order
- Raphidioptera
description
A generalised climatic profile has been estimated for the Kishenehn formation by a nearest living relative analysis of mollusks (Pierce & Constenius, 2001). These include taxa associated with both megathermal and microthermal climates. Pierce and Constenius rejected the notion that these coexisted, assuming the mixing of populations from different elevations. Such a mixed community is, however, consistent with a temperate climate with mild winters as in the Okanagan Highlands (above).
description
It has been generally thought that extant snakeflies (Inocelliidae and Raphidiidae) require a cold interval to mature, explaining their restriction to mid- and higher latitudes of the Northern Hemisphere, reportedly in high, cooler elevations in the southern portions of their range (Aspöck, 1998, 2000, 2002; Aspöck & Aspöck, 2009, 2014; Abbt et al., 2018). Aspöck (2000) stated that the cold interval is necessary to induce pupation and develop the imago, which must be 0 ° C or below. Abbt et al. (2018) later found that at least some can mature in the laboratory with a cold interval of 4 ° C. This would account for their exclusion from the tropics. In North America, they are found west of the Rocky Mountains from about 53 ° N in southern British Columbia with some known from as far south as the Mexico-Guatemala border. In the Eastern Hemisphere, they range from Norway at 70 ° N as far south as parts of Mediterranean North Africa, with scattered records eastward through Asia to the Pacific, southward to the Himalayas, northern Thailand and Taiwan (Aspöck, 1998; Aspöck et al., 2011, 2012 a, b; Aspöck & Aspöck, 2014; Blades, 2019). The fossil record of Raphidioptera before the Oligocene, especially of the extant families, would then present a biogeographic puzzle. The Eocene / Oligocene boundary represents the end of the globally warm “ greenhouse world ” climates of the Cretaceous through the Paleocene and Eocene, with higher mean annual temperatures (MAT), a low pole to equator MAT gradient, and lowered temperature seasonality with mild winters. The post-Eocene onset of the modern “ icehouse world ” regime saw extra-tropical climates with colder MAT, lacking Arctic ice sheets until the later Neogene and Antarctic ice sheets beginning to form at the end of the Eocene, an increased latitudinal MAT gradient, and more severe extra-tropical winters (Zachos et al., 2008). Raphidioptera of the Paleocene and Eocene did not then experience cold winters, and in the Mesozoic lived under even warmer conditions, some in low latitudes, e. g., Brazil (e. g., Oswald, 1990) and Myanmar (e. g., Engel, 2002; Liu et al., 2016).
description
The Okanagan Highlands communities also included a suite of other insects that today inhabit cooler boreal regions, higher elevations in lower latitudes, or mostly so. These include aphids (Hemiptera, Aphidoidea), scorpionflies (Mecoptera, Panorpidae, species of Panorpa Linnaeus: Archibald et al., 2013 b) and sawflies and wood wasps (Hymenoptera, Symphyta: Tenthredinidae, Siricidae, Pamphiliidae, Cephidae: Archibald & Rasnitsyn, 2015; Archibald et al., 2018). The Okanagan Highlands green lacewings (Neuroptera, Chrysopidae) consist of at least nine species of Nothochrysinae and one of the predominantly Mesozoic Limaiinae, it’s youngest occurrence. Today, Nothochrysinae mostly prefer Mediterranean climates of milder winters (Archibald et al., 2014). Green lacewings of the Chrysopinae thrive in a wide range of climates, including regions of very cold winters. They appear in the fossil record after Okanagan Highlands time at the end of the Eocene, subsequently diversifying to vastly dominate the family today across most of the globe from the equator to northern Siberia in our post-Eocene icehouse world as the Nothochrysinae became relictual. Nymphinae (Neuroptera, Nymphidae), found at two Okanagan Highlands localities (Archibald et al., 2009; Archibald & Makarkin, 2020) is today restricted to Australia, where it is less seasonal than at equivalent northern latitudes.
discussion
At the same time, snakeflies to the east of the Okanagan Highlands from the Green River Formation of Colorado inhabited much warmer lowland climates, with high mesothermal (mesothermal = MAT> 13 °, <20 ° C) to megathermal (MAT ≥ 20 ° C) MAT value estimates ranging from 19.6 ° C to 23.0 ° C (Wilf, 2000; Archibald et al., 2011 and references therein). Its forests also included frost-intolerant palms. Green River Raphidioptera probably inhabited similar or warmer temperatures than Harraphidia at Tarifa, Spain, where MAT is 17.2 ° C and had mild coldest months as above (Monserrat & Papenberg, 2006; AEMET, 2020). Although the Green River Formation was deposited in a lowland intermontane basin, the abundance of snakefly fossils indicates that they were part of the local community, as river transport from a distant mountain source would have been a rare event. There are numerous rocks with more than one specimen, in one case, four (Fig. 14 A). Further, almost all specimens in the UCM collection examined have a body with wings, i. e., are complete or at least relatively so. The wings may be folded in some, but in general, these do not appear to have suffered mechanical degradation characteristic of long-distance river transport. We believe that these also lived near their depositional lake.
discussion
Therefore, all known Raphidioptera before the Oligocene, including Inocelliidae and Raphidiidae, inhabited regions of mild winters without cold intervals whether in hot or temperate climates. An adaptation to winter cold must have evolved independently in both extant families sometime after the Eocene / Oligocene boundary in the modern icehouse world climatic regime, with some members retaining or subsequently reverting to the plesiomorphic adaptation to warm winters. After the onset of cold extra-tropical icehouse world winters, biota of latitudes outside of the tropics either went extinct (perhaps accounting for the extinctions of, e. g., the Limaiinae and Baissopteridae), moved to or restrict their ranges to lower latitudes and Southern Hemisphere regions of mild winters (e. g., Nymphidae, palm bruchids, Dinidoridae, Mastotermitidae, Mymeciinae, and Diplopterinae), or remained and adapted to more severe winters (e. g., aphids, Panorpa, Tenthredinidae, Siricidae, Pamphiliidae, Cephidae, Panorpidae, shift to dominance of the Chrysopinae within Chrysopidae). Raphidioptera appears to have mostly followed the latter path.
Name
- Homonyms
- Raphidioptera Navas 1916
- Raphidioptera