ScAm - 09.2019

DISPATCHES FROM THE FRONTIERS OF SCIENCE, TECHNOLOGY AND MEDICINE

JOIN THE CONVERSATION ONLINE Visit 2_w²íˆ_Ĉ¬wޝ_C²on Facebook and Twitter

INSIDE

_5šx‹øžllā³D­ž`ä ̧…îšxÇx߅x`î`ßxÇx

_5DlÇ ̧§xäîšßžþž³ž³x§xǚD³îäÜ… ̧ ̧îÇߞ³îä

_%xÿ­DÇä ̧…<ÇßxþD§x³`xž³…ßž`D

_5ž³āß ̧U ̧îäîšDîÿ ̧ߦDäDø³ž‰xl`§øäîxß

GILBERT S. GRANT

Science Source

0"'%5'"'?

Motion in

the Ocean

Fossils clarify some of animals’

earliest deliberate movements

About 550 million years ago animals

were relegated to the seas. Microbes and

larger multicellular organisms covered

­ø`š ̧…îšxäxD‹ ̧ ̧ßž³D³ ̧ߐD³ž`­Dî䞭ž-

lar to pond scum. On top of this settled big-

ger animals, including Dickinsonia—a genus

of perplexing creatures shaped like dinner

ǧDîxäjß ̧ø³lUDîš­DîäD³l‹Dîîx³xl` ̧ž³äÍ

Scientists have long speculated about

what Earth’s life was like half a billion years

ago, during the Ediacaran period, and they

DßxäîxDlž§ā‰³lž³­ ̧ßx`§øxäÍäîølā

published online in June in Geobiology

reports that Dickinsonia may have been

ä ̧­x ̧…îšx‰ßäî` ̧­Ç§xĀD³ž­D§äî ̧­ ̧þx

̧³îšxžß ̧ÿ³ž³äxDß`š ̧…… ̧ ̧lÍ5šžä‰³lž³j

experts say, could help us better under-

stand animals’ evolution.

Since Dickinsonia ÿxßx‰ßäîlxä`ߞUxlž³

the 1940s, scientists have debated exactly

what type of organism they were. “They’ve

been interpreted as everything from a lichen

to a worm—a whole variety of things,” says

Scott Evans, a paleontology researcher at

the University of California, Riverside, and

one of the study authors. “Recently it has

Ux` ̧­xDÇÇDßx³îîšDîä³ÿDälx‰-

nitely an animal.” Based on the fossil evi-

dence, scientists think Dickinsonia were soft-

bodied and oval-shaped, with multiple body

divisions and ribbed upper and lower surfac-

es. They had a distinct front and back and

could grow up to a meter in length but were

only several millimeters thick.

Evans and other researchers from U.C.