Assassin Bug Fossil

Recovered from the Green River Formation in present-day Colorado, this fossil represents a new genus and types of predatory insects known as assassin bugs. Credit: Image courtesy Palaeontological Association

The fossilized insect is small and its genital pill, called a pygophore, is roughly the length of a grain of rice.

The find is reported in the journal Documents in Palaeontology

Sam Heads

Illinois Nature Survey paleontologist Sam Heads co-led the research study of an extraordinarily unspoiled 50 million-year-old fossil bug. Credit: Image by L. Brian Stauffer

Found in 2006 by bursting a slab of rock, the fossilized bug split nearly perfectly from head to abdomen. The fracture also broke the pygophore in 2. A fossil dealership later on offered each half to a different collector, and the scientists tracked them down and reunited them for this study.

Having the ability to see a bug’s genitalia is extremely practical when trying to figure out a fossil insect’s place in its family tree, said Sam Heads, a paleontologist at the Illinois Nature Survey and self-described fossil insect-genitalia specialist who led the research with Daniel Swanson, a college student in entomology at the University of Illinois Urbana-Champaign.

Types are frequently specified by their ability to successfully mate with one another, and little differences in genitalia can lead to sexual incompatibilities that, gradually, might result in the increase of new types, Swanson said. This makes the genitalia a great place to focus to determine an insect types.

However such structures are typically obscured in compression fossils like those from the Green River Development.

” To see these great structures in the internal genitalia is an unusual reward,” Swanson said. “Typically, we only get this level of detail in types that are living today.”

The structures visible within the pygophore include the basal plate, a hardened, stirrup-shaped structure that supports the phallus, he stated. The fossil also maintained the shapes of the phallotheca, a pouch into which the phallus can be withdrawn.

Daniel Swanson

U. of I. entomology college student Daniel Swanson co-led the research on an ancient assassin bug fossil. Credit: Image by L. Brian Stauffer

The find suggests that the banded assassin bugs, a group to which the new specimen is believed to belong, are about 25 million years older than previously thought, Swanson said.

” There have to do with 7,000 types of assassin bug explained, but just about 50 fossils of these bugs are understood,” he said. “This just speaks with the improbability of even having a fossil, let alone among this age, that provides this much details.”

This is not the earliest fossil bug genitalia ever discovered, however.

” The earliest recognized arthropod genitalia are from a kind of bug called a harvestman that is 400-412 million years of ages, from the Rhynie Chert of Scotland,” Heads stated. “And there are likewise various fossil pests in amber as old as the Cretaceous Period with genitalia preserved.

” Nevertheless, it is nearly unusual for internal male genitalia to be protected in carbonaceous compressions like ours,” he said.

The researchers named the brand-new assassin bug Aphelicophontes danjuddi. The types name originates from among the fossil collectors, Dan Judd, who donated his half of the specimen to the INHS for study.

Recommendation: 19 January 2021, Documents in Paleontology
DOI: 10.1002/ spp2.1349

The INHS is a division of the Grassy field Research Study Institute at the U. of I.

The National Science Foundation supported this work.


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