This spiny slug blazed a trail for snails

February 06, 2017

New Haven, Conn. - Reach back far enough in the family tree of a snail or a clam and you'll find a spiny little slug with tiny teeth, wearing a helmet.

Scientists have unearthed the 480-million-year-old remains of a creature that reveals the earliest stages in the evolution of mollusks, a diverse group of invertebrates that includes squids, octopuses, snails, and clams. The discovery was announced in a paper published online Feb. 6 in the journal Nature.

The animal's name is Calvapilosa -- which means "hairy scalp" -- and it came from a fossil-rich deposit in Morocco known as the Ordovician Fezouata Formation. The researchers said Calvapilosa is an early offshoot of the line leading to modern coat-of-mail shells or chitons. Calvapilosa has a tooth-lined jaw for feeding, carries a helmet-like shell on its head, and has spines that extend over its entire upper body.

"This discovery brings a neat solution to how the ancestor of all mollusks may have looked," said lead author Jakob Vinther, a former Yale doctoral student who is now at the University of Bristol. "It was a slug that carried a single shell and lots of little spines or sclerites."

The researchers believe these spines, which were not mineralized in the earliest mollusks, hardened and became stronger in Calvapilosa.

"Mollusks consist of a multitude of distinct groups, which all originated about 520 million years ago in a very short period of time, probably less than 20 million years," said Derek Briggs, Yale's G. Evelyn Hutchinson Professor of Geology and Geophysics and curator at the Yale Peabody Museum of Natural History. Briggs co-authored the study.

"Their evolutionary history is squeezed into a brief interval of evolutionary time called the Cambrian explosion, which makes the sequence of events difficult to piece together," Briggs said.

Calvapilosa's anatomy is similar to that of some famous older fossils from the Burgess Shale in Canada (Orthrozanclus) and Sirius Passet in Greenland (Halkieria). Those animals, along with Calvapilosa, now will find places on the earliest branches of the mollusk family tree.

Additional co-authors are Peter Van Roy, a former postdoctoral researcher at Yale, who is now at Ghent University; and Luke Parry, a doctoral student at the University of Bristol who will be joining the Briggs lab at Yale in 2018. "Morocco has revealed itself as a fossil treasure trove for ancient life," said Van Roy, who discovered the Fezouata Biota. "It never ceases to amaze me what is discovered there."
-end-
The research was supported by a grant from the National Science Foundation and by the Division of Invertebrate Paleontology at the Yale Peabody Museum of Natural History, where specimens of the new fossil mollusk are held.

Yale University

Related Evolution Articles from Brightsurf:

Seeing evolution happening before your eyes
Researchers from the European Molecular Biology Laboratory in Heidelberg established an automated pipeline to create mutations in genomic enhancers that let them watch evolution unfold before their eyes.

A timeline on the evolution of reptiles
A statistical analysis of that vast database is helping scientists better understand the evolution of these cold-blooded vertebrates by contradicting a widely held theory that major transitions in evolution always happened in big, quick (geologically speaking) bursts, triggered by major environmental shifts.

Looking at evolution's genealogy from home
Evolution leaves its traces in particular in genomes. A team headed by Dr.

How boundaries become bridges in evolution
The mechanisms that make organisms locally fit and those responsible for change are distinct and occur sequentially in evolution.

Genome evolution goes digital
Dr. Alan Herbert from InsideOutBio describes ground-breaking research in a paper published online by Royal Society Open Science.

Paleontology: Experiments in evolution
A new find from Patagonia sheds light on the evolution of large predatory dinosaurs.

A window into evolution
The C4 cycle supercharges photosynthesis and evolved independently more than 62 times.

Is evolution predictable?
An international team of scientists working with Heliconius butterflies at the Smithsonian Tropical Research Institute (STRI) in Panama was faced with a mystery: how do pairs of unrelated butterflies from Peru to Costa Rica evolve nearly the same wing-color patterns over and over again?

Predicting evolution
A new method of 're-barcoding' DNA allows scientists to track rapid evolution in yeast.

Insect evolution: Insect evolution
Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich have shown that the incidence of midge and fly larvae in amber is far higher than previously thought.

Read More: Evolution News and Evolution Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.