Discovery provides new insights into the evolution of crabs and when they spread around the world
Looking at the ancient piece of amber, Javier Luque’s first thought wasn’t whether the crustacean trapped inside could help fill a crucial gap in crab evolution. He just, more or less, wondered what the heck is a crab doing stuck in fossilized tree resin?
“In a way, it’s like finding a shrimp in amber,” said Luque, a post-doctoral researcher in the Harvard Department of Organismic and Evolutionary Biology. “Talk about wrong place, wrong time.”
Luque spent three years trying to unravel the puzzle and, along with a team of international scientists, reported the findings on today (October 20, 2021) in Science Advances.
They say the 100-million-year-old piece of amber, recovered from the jungles of Southeast Asia, holds what’s believed to be the oldest modern looking crab ever found. The discovery provides new insights into the evolution of these crustaceans and when they spread around the world.
The 5-millimeter crab is the first-ever found in amber from the dinosaur era, and the researchers think it represents the oldest evidence of incursions into non-marine environments by “true crabs.”
True crabs (known as Brachyurans) stand in contrast to “false crabs” (called Anomurans) that aren’t technically crabs but are still sometimes called by the name (think hermit crabs or king crabs).
Previous fossil records, which mainly consist of bits and pieces of claws, suggested that nonmarine crabs came onto land and freshwater about 75 to 50 million years ago. This new discovery pushes that back to at least 100 million years ago, answering Luque’s initial question of what this crab was doing in the jungle and bringing the fossil record in line to long-held theories on the genetic history of crabs.
“If we were to reconstruct the crab tree of life — putting together a genealogical family tree — and do some molecular
The team, using micro-CT scans, was able to see in clear detail delicate tissues like the crab’s antennae, legs, and mouthparts lined with fine hairs, large compound eyes, and even its gills. Not even a single hair was missing, they said.
The study was a collaboration between Harvard and the China University of Geosciences, and included authors from 10 institutions including (function(d, s, id){
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