Fossils: Ancient parasitic ‘Venus flytrap’ wasp preserved in amber
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Holotype of Sirenobethylus charybdis
view moreCredit: Qiong Wu
An extinct lineage of parasitic wasps dating from the mid-Cretaceous period and preserved in amber may have used their Venus flytrap-like abdomen to capture and immobilise their prey. Research, published in BMC Biology, finds that the specimens of Sirenobethylus charybdis — named for the sea monster in Greek mythology which swallowed and disgorged water three times a day — date from almost 99 million years ago and may represent a new family of insects.
The morphology of S. charybdis indicates the wasps were parasitoids — insects whose larvae live as parasites and eventually kill their hosts. Modern-day parasitoids of the superfamily Chrysidoidea include cuckoo wasps and bethylid wasps. However, the S. charybdis specimens possess a unique pattern of veins in the hind wing that suggests the species belongs within its own family, the Sirenobethylidae.
Taiping Gao, Lars Vilhelmsen, and colleagues from the Capital Normal University, China, and the Natural History Museum of Denmark used Micro-CT scanning to analyse 16 female S. charybdis specimens preserved in amber dated to 98.79 million years ago. These specimens were collected from the Kachin region in northern Myanmar. They find the species was likely to have been a koinobiont — a parasitoid which allows its host to continue growing while feeding on it. The wasp specimens have an abdominal apparatus comprised of three flaps, the lower of which forms a paddle-shaped structure with a dozen hair-like bristles, visually reminiscent of a Venus flytrap plant. The authors note the abdominal apparatus of S. charybdis is unlike that of any known insect, and may have served as a mechanism to temporarily restrain the host during egg-laying. As the wasp was likely unable to pursue prey over long distances, they speculate that it would have waited with the apparatus open for a potential host to activate its capture response.
The authors believe the elaborate grasping apparatus allowed S. charybdis to target highly mobile prey such as small, winged or jumping insects. The preserved specimens suggest that Chrysidoidea displayed a wider range of parasitoid strategies in the mid-Cretaceous period than their present-day counterparts.
Journal
BMC Biology
Method of Research
Observational study
Subject of Research
Animals
Article Title
A Cretaceous fly trap? Remarkable abdominal modification in a fossil wasp
Article Publication Date
27-Mar-2025
New species revealed after 25 years of study on ‘inside out’ fossil – and named after discoverer’s mum
Study from University of Leicester describes a new species of fossil that is 444 million years-old with soft insides perfectly preserved
University of Leicester
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The fossil Keurbos susanae - or Sue - in the rock.
view moreCredit: University of Leicester
A new species of fossil from 444 million years ago that has perfectly preserved insides has been affectionately named ‘Sue’ after its discoverer’s mum.
The result of 25 years of work by a University of Leicester palaeontologist and published in the journal Palaeontology, the study details a new species of multisegmented fossil and is now officially named as Keurbos susanae.
Lead author Professor Sarah Gabbott from the School of Geography, Geology and the Environment said: “‘Sue’ is an inside-out, legless, headless wonder. Remarkably her insides are a mineralised time-capsule: muscles, sinews, tendons and even guts all preserved in unimaginable detail. And yet her durable carapace, legs and head are missing – lost to decay over 440 million years ago.
“We are now sure she was a primitive marine arthropod but her precise evolutionary relationships remain frustratingly elusive.”
Today about 85% of animals on Earth are arthropods, and they include shrimps, lobsters, spiders, mites, millipedes and centipedes.
They have an excellent fossil record stretching back over 500 million years but usually their fossil remains are of their external features, whereas ‘Sue’ is the complete opposite because it is her insides that are fossilized.
The fossil was found in the Soom Shale, a band of silts and clays at a location 250 miles north of Cape Town in South Africa. These strata were laid down on the seafloor over 440 million years ago at a time when a devastating glaciation had wiped out about 85% of Earth’s species – one of the big five ‘mass extinctions’. It seems that the marine basin in which ‘Sue’ swam was somehow protected from the worst of the freezing conditions and a fascinating community of animals, including ‘Sue’, took refuge there.
The conditions in the sediments where Sue came to rest were toxic in the extreme. There was no oxygen but worse than that there was deadly (and stinking) hydrogen sulphide dissolved in the water. The researchers suspect that a strange chemical alchemy was at work in creating the fossil and its unusual inside-out preservation.
But there is a downside, because the unique preservation of ‘Sue’ makes it difficult to compare her to other fossils of the era and so it remains a mystery how she fits into the evolutionary tree of life.
The small roadside quarry where Professor Gabbott found the fossils 25 years ago at the start of her academic career has all but disappeared and so other specimens are unlikely to be found. The fossil was incredibly difficult to interpret and Professor Gabbott held out hope of finding another specimen with its head or legs intact.
Professor Gabbott adds: “This has been an ultramarathon of a research effort. In a large part because this fossil is just so beautifully preserved there’s so much anatomy there that needs interpreting. Layer upon on layer of exquisite detail and complexity. I’d always hoped to find new specimens but it seems after 25 years of searching this fossil is vanishingly rare – so I can hang on no longer. Especially as recently my mum said to me ‘Sarah if you are going to name this fossil after me, you’d better get on and do it before I am in the ground and fossilized myself’.
“I tell my mum in jest that I named the fossil Sue after her because she is a well-preserved specimen! But, in truth, I named her Sue because my mum always said I should follow a career that makes me happy – whatever that may be. For me that is digging rocks, finding fossils and then trying to figure out how they lived what they tell us about ancient life and evolution on Earth.”
Professor Sarah Gabbott from the University of Leicester School of Geography, Geology and the Environment, at the site where the fossil was discovered.
Professor Sarah Gabbott from the University of Leicester School of Geography, Geology and the Environment, at the site where the fossil was discovered.
Professor Sarah Gabbott from the University of Leicester School of Geography, Geology and the Environment, at the site where the fossil was discovered.
Professor Sarah Gabbott from the University of Leicester School of Geography, Geology and the Environment, at the site where the fossil was discovered.
Professor Sarah Gabbott from the University of Leicester School of Geography, Geology and the Environment, at the site where the fossil was discovered.
Credit
University of Leicester
University of Leicester
Journal
Palaeontology
Article Title
A new euarthropod from the Soom Shale (Ordovician) Konservat-Lagerstätte, South Africa, with exceptional preservation of the connective endoskeleton and myoanatomy
Article Publication Date
26-Mar-2025
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