Shell-breaking crab from dinosaur age discovered


This video from the USA is called Florida Stone Crab, Clearwater Marina, Clearwater, Florida.

From Cornell University in the USA:

While waiting for colleagues at a small natural history museum in the state of Chiapas, Mexico last year, Cornell paleontologist Greg Dietl chanced upon a discovery that has helped rewrite the evolutionary history of crabs and the shelled mollusks upon which they preyed.

In a museum display case he recognized a 67- to 69-million-year-old fossil from the Late Cretaceous period of a big crab with an oversized right claw. Such crabs with claws of different sizes were not known to exist until the early Cenozoic era, about 20 million years later. Aside from being larger than most known Late Cretaceous crabs (about the size of today’s Florida stone crabs) and having asymmetrical claws, this ancient crab also sported a curved tooth on the movable finger of the larger right claw. This was another specialized adaptation that paleontologists thought developed millions of years later for peeling snail shells open.

“I immediately had to point it out to my colleagues around me,” said Dietl, an adjunct professor in Cornell’s Department of Earth and Atmospheric Sciences and director of collections at the Cornell-affiliated Paleontological Research Institution in Ithaca. “I was really excited when I found it. The fossil re-opens the question of the role crabs played in the well-documented restructuring of marine communities that occurred during the Mesozoic era [251 million years ago to 65 million years ago].”

The discovery led to a study, published March 10 in the online version of the Royal Society’s Biology Letters journal>, coauthored by Francisco J. Vega, a geologist at the Universidad Nacional Autónoma de México.

The museum’s staff showed Dietl and colleagues another fossil of the same species in a back room. Both specimens, found near the town of Ocozocoautla in southeastern Mexico, are the oldest fossils with these unique features on record and represent a new species, Megaxantho zogue.

The large right “crusher” claw generated a great deal of force to break shells, while the smaller left cutter claw moved faster and could manipulate prey into position. Also, the curved tooth increased the power of the claw.

Dietl hopes the discovery will spur other researchers to search for similar examples of these curved tooth structures from the Late Cretaceous period, just prior to the extinction of the dinosaurs.

Although Megaxantho crabs became extinct around 65 million years ago, these features evolved again in other crab species throughout the Cenozoic era, leading to present-day crabs, according to the study. The repeated evolution suggests that such power-enhancing adaptations may evolve during times and places where resources are abundant and accessible, Dietl said.

Cretaceous marine life extinction: here.

Rare crab Labuanium trapezoideum, feared extinct, spotted in Taiwan: here.

Crabs Not Only Suffer Pain, But Retain Memory Of It: here.

Rare visitors washed up on Cornish beach – Columbus crabs: here.

2 thoughts on “Shell-breaking crab from dinosaur age discovered

  1. Updated Tuesday, June 30, 2009 9:42 am TWN, CNA

    Watch out for crabs crossing the highway: Kenting park

    PINGTUNG, Taiwan — Southern Taiwan’s Kenting National Park Administration urged motorists yesterday to slow down when driving on the highway near the coastal area of Kenting, Pingtung County because large numbers of land crabs will soon be making their way down to the sea to lay eggs.

    Hundreds of the crabs will cross Provincial Highway 1 in the town to spawn on the seashore beginning July 7 or July 8 this year and continuing to late October, the high season for land crabs to spawn, park rangers told reporters.

    As the highway separates the land crabs’ normal habitat from their spawning grounds, the crustaceans used to be crushed by passing vehicles, which prompted the park administration to later enact traffic restrictions in the peak spawning season to protect the creatures.

    The move is part of increasing efforts made by Taiwan’s government and people in recent years to protect animals and the environment.

    The highway runs along Kenting’s Banana Bay, the part of which near Oluanpi is the main spawning area for the crabs.

    Rangers on Monday reminded motorists to be extra careful when driving on that part of the highway at night from July to October. During this period, female crabs loaded with eggs make their way across the highway down to the sea to spawn at night time.

    Along the highway at Banana Bay, a public traffic sign has been erected warning motorists to “Watch out for land crabs and drive slowly.”

    According to a research study conducted by an academic institute several years ago, 25 different species of land crabs live near the Banana Bay area, making it the No. 1 place in the world in terms of the diversity of land crab species.

    “The number of species has increased to 28 now, thanks to conservation measures,” the rangers said.

    http://www.chinapost.com.tw/taiwan/local/pingtung/2009/06/30/214241/Watch-out.htm

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