How Mollusks Got Their Teeth 

University of Toronto graduate student Martin Smith has for the first time reconstructed mouthparts of two mollusk-like animals Odontogriphus and Wiwaxia that lived in Cambrian seas 500 million years ago.

by Sergio Prostak

The radula sounds like something from a horror movie – a conveyor belt lined with hundreds of rows of interlocking teeth. In fact, radulas are found in the mouths of most mollusks, from the giant squid to the garden snail. Smith has found that a ‘prototype’ radula of 500-million-year-old fossils was not a flesh-rasping terror, but a tool for humbly scooping food from the muddy sea floor.

The Cambrian animals Odontogriphus and Wiwaxia might not have been much to look at – the former a naked slug, the latter a creeping bottom-dweller covered with spines and scales. Despite the hundreds of fossil specimens collected from the Canadian Rockies by the Royal Ontario Museum, scientists could not agree whether they represented early mollusks, relatives of the earthworm, or an evolutionary dead-end.

Smith, author of a paper published in the Proceedings of the Royal Society B, employed a new, non-destructive type of electron microscopy to reveal the new details.

“I put the fossils in the microscope, and the mouth parts just leaped out,” Smith said. “You could see details you’d never guess were there if you just had a normal microscope.”

After examining some 300 fossils, Smith was able not just to reconstruct the mouthparts, but work out how they grew…

(read more: Sci-News)           (image: Nobu Tamura)

Hermaphrodite Sea Slug Mates With Throwaway Penis

“A bizarre, hermaphrodite sea slug may give new meaning to the word “quickie.” The nudibranch uses a disposable penis to have sex more frequently, according to a new study.

The animal, described today (Feb. 12) in the journal Biology Letters, is the first discovered to use an easily regenerated, disposable penis.

Nudibranches are simultaneous hermaphrodites, meaning that they have penises that they use to fertilize others as well as female sex organs. But exactly how their sex worked remained a mystery.”

These Costa Rican tadpoles have see-through skin that reveals neatly coiled intestines.

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Strange Ancient Fish Had Front And Back Legs

The closest known relative of the ancestors of limbed animals such as humans likely evolved the foundation for rear legs even before the move to land, researchers say. This ancestor may have even been able to walk underwater, they added.

These findings reveal that a key step in the evolution of hind limbs happened in fish, challenging previous theories that such appendages evolved only after the move to land.

Scientists investigated fossils of a 375-million-year-old fish known as Tiktaalik roseae, discovered in 2004 in northern Canada’s Ellesmere Island. Possessing a broad flat head and sharp teeth, Tiktaalik resembled a cross between a fish and a crocodile, growing to a length of 9 feet (2.7 meters) as it hunted for prey in shallow freshwater.