Paleontologists say they have discovered the first fossil of an Australian sawfly species, Baladi warru, found at McGraths Flat in central New South Wales.
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Baladi warru. Image credit: Michael Frese, University of Canberra.
Baladi warru lived in Australia during the Miocene period, between 11 and 16 million years ago.
This species belongs to Pergidae, a moderate-sized family of sawflies occurring in the western hemisphere and the Australasian region.
“Despite the name, sawflies are not flies but a type of wasp, with spitfires the most widely recognized group of sawfly species in Australia,” said CSIRO paleontologist Dr. Juanita Rodriguez and colleagues.
“They are called sawflies because they have a saw-like ovipositor that is used to lay eggs, and they could be mistaken as flies because they lack a typical wasp waist.”
“The sawfly family Pergidae includes 441 species, of which 276 are found in the Americas (the majority in South America) and 165 in the Australasian region,” they added.
“Most adult females lay eggs on suitable host plants and larvae feed on plant tissue, often in close aggregations.”
“The Pergidae are part of a large radiation of plant-feeding sawflies comprising more than 7,000 species of early Hymenoptera.”
“There are currently only two known fossil representatives of Pergidae: Fonsecadalia perfectus and Fonsecadalia propinquus.”
Life reconstruction of Baladi warru. Image credit: Alex Boersma.
The fossil of Baladi warru was found in 2018 at McGraths Flat, a fossil site around 25 km northeast of Gulgong in central New South Wales.
“We looked at the fossil and its morphology and then put this information together with molecular and morphological data from a wide sample of current sawfly species,” Dr. Rodriguez said.
“This helped us decipher the fossil’s placement in the sawfly tree of life.”
“We used the fossil’s age and its placement to establish that sawflies originated in the Cretaceous period, around 100 million years ago, which means their ancient ancestors lived in Gondwana.”
“When this supercontinent split up, sawflies ended up distributed in Australia and South America.”
“When we examined the fossil, we identified pollen grains on the sawfly’s head which revealed it had visited a flowering Quintinia plant.”
“This helped our team trace complex species interactions in the paleoenvironment of McGraths Flat.”
Reconstruction of the Miocene-period McGraths Flat. Image credit: Alex Boersma.
“This discovery would help researchers track evolution and distribution of sawflies,” said Dr. Michael Frese, a paleontologist at the University of Canberra and a visiting scientist at CSIRO.
“In particular, this find has helped us in understanding the incredible ability of sawflies to feed on toxic plants.”
“They eat the leaves of Myrtaceae — a family of woody plants that includes eucalypts — because they have mouthparts with which they can separate toxic oils or a chemical detoxification system inside their gut when feeding on myrtaceous leaves.”
“This enables the larvae, sometimes called spitfires, to use the oils as a defensive weapon.”
“In terms of the bigger picture, our work is helping researchers make sense of their current distribution across Australia and the Americas.”
“Although this particular species, Baladi warru, has been extinct for millions of years, it provides information on native pollinators so we can understand their evolution and impact in the present.”
The discovery is described in a paper published on October 17 in the journal Systematic Entomology.
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Juanita Rodriguez et al. A new exceptionally preserved sawfly fossil (Hymenoptera: Pergidae) and an evaluation of its utility for divergence time estimation and biogeography. Systematic Entomology, published online October 17, 2024; doi: 10.1111/syen.12653
