Photo credits: Oksana Vernygora / University of Alberta Yale University announced the discovery of a treasure trove of hundreds of well-preserved crab specimens. The fossils include species of real shrimp, prawn shrimp and exciting new branch of the evolutionary crab tree. The specimens were recovered from Colombia and the United States and date from the mid-Cretaceous period (about 90 to 95 million years ago).
Googly-eyed by design
"Callichimaera perplexa is so unique and strange that it is possible to have the duckbill of the crab world," said Javier Luque, who led the research effort.
"It hints at how develop new shapes and become so different over time. Usually we think of crabs as big animals with wide carapaces, powerful claws, small eyes in long eye stems and a small tail stowed under the body. Well, Callichimaera resists all this & # 39; sullen & # 39; Characteristics and forces a rethinking of our definition of what makes a crab a crab.
Reconstruction of Callichimaera perplexa.
Photo credits J. Luque et al., 2019, Science Advances.
The team writes Callichimaera perplexa is one of the earliest species Scorpio (which lived more than 250 million years ago) was named after the Chimera, a mythological creature whose body contains features from several animals, its full name meaning "amazing beautiful chimeras".  The specimen, which Luque describes as "unusual and cute," is definitely confusing.The ancient crab was rather tiny and about a quarter in size, with a striking pair of large, compound eyes – but no eye sockets. leg-like mouthpieces and a long body ending in an exposed tail completed his face.
These latter features are b is characteristic of pelagic crab larvae today, writes the team. This points to an evolutionary connection that connects them to the ancient species. The team believes that these characteristics have been maintained and enhanced in miniaturized adults through changes in timing and development speed. This process, called "heterochrony," is one of the mechanisms by which species evolve novel body parts.
"It is very exciting to find new branches in the tree of life from a distant past, especially from regions, like the tropics, which, although today they are hotspots of diversity, are places which we know least about their former diversity, "said Luque Formen about heterochrony," was published in the journal Science Advances .