The new find suggests that Liassophlebiidae — a small extinct family of damsel-dragonflies known from the Early Mesozoic of Europe, Asia, and Antarctica — arose in the immediate aftermath of the Triassic-Jurassic mass extinction.
An artist’s impression of Liassophlebia sp., resting on a frond of the paleofern species Phlebopteris muensteri. Image credit: Jules Kiely, Bristol Museum & Art Gallery / Swaby et al., doi: 10.1080/08912963.2023.2261957.
Damselflies and dragonflies comprise the insect superorder Odonatoptera, one of the oldest groups of winged insects. The earliest records of their occurrence are from the Serpukhovian age of the Carboniferous period.
The Carboniferous Odonatoptera include the well-known, large proto-odonates known as griffenflies that had the largest wingspan (c. 71 cm, or 28 inches) of all the insects that have ever lived.
The Triassic was a pivotal period for Odonatoptera lineages, with the diversification of the three groups ‘Protozygoptera,’ Triadophlebiomorpha, and crown Odonata.
One of the earliest Odonata lineages, Liassophlebiidae, is a small extinct family of damsel-dragonflies known from the early Mesozoic of Western Europe, Central Asia, and Antarctica.
First described in 1925, the family is currently represented by the following five genera: Bavarophlebia, Ferganophlebia, Grimmenopteron, Rossiphlebia, and Liassophlebia.
“Whilst evidence within the fossil record shows that Liassophlebiidae clearly diversified during the Early Jurassic, the initial appearance of Liassophlebiidae has previously only been suggested from three very fragmentary specimens in layers interpreted to be latest Rhaetian in age at Strensham, Worcestershire, UK,” said Open University paleontologist Emily Swaby and colleagues.
“Thus any new fossils from this family, including the new specimen, are important for better evaluating and understanding the diversification of the crown Odonata.”
Part (a), counterpart (b) and line drawing (c) of a fossilized partial forewing — only the fourth specimen of the Rhaetian Liassophlebiidae — belonging to the damsel-dragonfly Liassophlebia sp. Parts of the wing are missing, including a large area towards the tapered end. The veins in the wing are of different thickness, with the thickest veins along the top edge. Image credit: Swaby et al., doi: 10.1080/08912963.2023.2261957.
The new specimen of Liassophlebiidae is an incomplete forewing about 4.2 cm (1.7 inches) long and 1 cm (0.4 inches) wide.
The fossil dates back 202 million years to the very latest part of the Rhaetian age of the Triassic period and likely represents a new species of the Liassophlebia genus.
It was collected from Bowdens Quarry, Somerset, UK, from the lower part of the White Lias Formation.
“While previous fossils attributed to Liassophlebia (Liassophlebiidae), most likely from the Rhaetian, were fragmentary and incomplete, this new specimen confirms the presence of Liassophlebiidae very close to the Triassic-Jurassic boundary in strata that is likely to be of Rhaetian age,” the paleontologists said.
“Although the specimen corresponds to a new species, we prefer not to establish a new name, due to the incomplete preservation of the other specimens and species of Liassophlebia. Thus, the specimen is assigned to the Liassophlebia genus.”
“The discovery of this new specimen enriches our knowledge of Odonata diversity at this time and indicates that Liassophlebiidae is likely to have originated immediately after the Triassic-Jurassic mass extinction,” they concluded.
Their paper was published in the journal Historical Biology.
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Emily J. Swaby et al. A new Liassophlebiidae (Odonata: Heterophlebioidea) from strata close to the Triassic-Jurassic boundary in Somerset, UK. Historical Biology, published online October 16, 2023; doi: 10.1080/08912963.2023.2261957
