| Petaluridae Temporal range: Stem group known from Late Jurassic | |
|---|---|
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| Tanypteryx pryeri | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Odonata |
| Infraorder: | Anisoptera |
| Superfamily: | Petaluroidea |
| Family: | Petaluridae Needham, 1903 [1] |
| Genera | |
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The petaltails, also called graybacks, of the family Petaluridae are among the most ancient of the extant true dragonflies (infraorder Anisoptera), [2] having fossil members from as early as the Jurassic, over 150 million years ago. A 2024 molecular phylogeny found that the petaltails comprise two clades, a Gondwanan clade and a Laurasian clade. Their divergence time was estimated at 160 million years ago. [3]
Modern petalurids include only 11 species, one of which, the Australian Petalura ingentissima , is by some measurements the largest of living dragonflies, having a wingspan of up to about 160 mm (6.3 in) and a body length of about 125 mm (4.9 in) ( Tetracanthagyna plagiata of another family can match or exceed its wingspan). Another large Australian species is Petalura gigantea , commonly known as the giant dragonfly. In the United States, two species are found, Tanypteryx hageni in the west and Tachopteryx thoreyi in the east. The larvae live primarily in stream banks, mostly in burrows, but the larvae of the eastern US species, Tachopteryx thoreyi, the gray petaltail, live in depressions under wet leaves. [4] The semiaquatic habitat of the larvae makes the petaltails unique in the modern dragonfly families.
Many fossil dragonfly genera have previously been suggested to belong to the Petaluridae, but currently, the only one that can definitively be placed in the Petaluridae itself is † Argentinopetala from the Early Cretaceous of Argentina. [5] Uniquely, this genus is thought to be a crown group-petalurid most closely related to Phenes . Outside the Petaluridae, several stem-group petalurid families are known, including †Cretapetaluridae from the Late Jurassic or earliest Cretaceous to the early-mid Cretaceous of Great Britan & Brazil, †Aktassidae from the Late Jurassic to early Cretaceous of Germany & China, and †Protolindeniidae from the Late Jurassic of Germany & Australia. While studies have found some of these to be fossil petaluroids, others appear to be paraphyletic with respect to the Gomphidae, and thus further taxonomic revisions are likely necessary. [6]
