"Long before it's in the papers"
December 02, 2015


Strange, early ecosystems found more complex than once thought

Nov. 30, 2005
Courtesy of University of Bristol
and World Science staff

Sci­en­tists have used com­put­er sim­ula­t­ions to work out how a strange 555-mil­lion-year-old crea­ture, with no known mod­ern rel­a­tives, ate.

The re­sult, sur­pris­ing for that time pe­ri­od, re­veals that some of the first large or­gan­isms formed ecosys­tems that were much more com­plex than pre­vi­ously thought, re­search­ers claim.

Tri­bra­chid­ium fossil (Credit: M. Laflamme)

They stud­ied fos­sils of an ex­tinct mar­ine or­gan­ism called Tri­bra­chid­ium. Us­ing a com­put­er mod­el­ing ap­proach called com­puta­t­ional flu­id dy­nam­ics, they con­clud­ed that it fed by col­lect­ing par­t­i­cles sus­pended in wa­ter. 

This is called sus­pen­sion feed­ing and it had­n’t pre­vi­ously been doc­u­mented in or­gan­isms from this pe­ri­od.

Tri­bra­chid­ium lived dur­ing a pe­ri­od called the Edi­acaran, which ranged from 635 mil­lion to 541 mil­lion years ago. This pe­ri­od fea­tured a va­ri­e­ty of large, com­plex or­gan­isms, most of which are hard to link to any mod­ern spe­cies. Another recently studied creature from that era is the ball-like Mega­clo­no­phy­cus.

Sci­en­tists pre­vi­ously thought that these or­gan­isms formed sim­ple ecosys­tems char­ac­ter­ized by only a few bas­ic feed­ing meth­ods, said Si­mon Dar­roch, a re­search­er at Van­der­bilt Un­ivers­ity in Nash­ville, Tenn., and a mem­ber of the re­search team.

The new stu­dy, pub­lished Nov. 27 in the jour­nal Sci­ence Ad­vanc­es, sug­gests they were ca­pa­ble of more types of feed­ing.

“For many years, sci­en­tists have as­sumed that Earth’s old­est com­plex or­gan­isms, which lived over half a bil­lion years ago, fed in only one or two dif­fer­ent ways. Our study has shown this to be un­true. Tri­bra­chid­ium and per­haps oth­er spe­cies were ca­pa­ble of sus­pen­sion feed­ing. This demonstra­tes that, con­tra­ry to our ex­pecta­t­ions, some of the first ecosys­tems were ac­tu­ally quite com­plex,” said Dar­roch.

Co-author Marc Laflamme of the Un­ivers­ity of To­ron­to Mis­sis­sau­ga added: “Tri­brachid­ium does­n’t look like any mod­ern spe­cies, and so it has been really hard to work out what it was like when it was alive. The ap­plica­t­ion of cutting-edge tech­niques, such as CT scan­ning and com­puta­t­ional flu­id dy­nam­ics, al­lowed us to de­ter­mine, for the first time, how this long-ex­tinct or­gan­ism fed.”

Com­puta­t­ional flu­id dy­nam­ics is a meth­od for sim­ulating flu­id flows that is com­monly used in en­gi­neer­ing, for ex­am­ple in air­craft de­sign, but this is among the first ap­plica­t­ions of the tech­nique in pa­le­on­tol­ogy.

“The com­put­er sim­ula­t­ions we ran al­lowed us to test com­pet­ing the­o­ries for feed­ing in Tri­bra­chid­ium. This ap­proach has great po­ten­tial for im­prov­ing our un­der­stand­ing of many ex­tinct or­gan­isms,” said Im­ran Rah­man of the Un­ivers­ity of Bris­tol, one of the col­la­bo­ra­tors.

“Meth­ods for dig­it­ally an­a­lyz­ing fos­sils in 3D have be­come in­creas­ingly wide­spread and ac­ces­si­ble over the last 20 years. We can now use these da­ta to ad­dress any num­ber of ques­tions about the bi­ol­o­gy and ecol­o­gy of an­cient and mod­ern or­gan­isms,” added co-author Ra­chel Raci­cot of the Nat­u­ral His­to­ry Mu­se­um of Los An­ge­les Coun­ty.

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Scientists have used computer simulations to work out how a strange 555-million-year-old creature, with no known modern relatives, ate. The result, surprising for that time period, reveals that that some of the first large organisms formed ecosystems that were much more complex than previously thought, researchers claim. They studied fossils of an extinct organism called Tribrachidium. Using a computer modeling approach called computational fluid dynamics, they concluded that it fed by collecting particles suspended in water. This is called suspension feeding and it hadn’t previously been documented in organisms from this period. Tribrachidium lived during a period called the Ediacaran, which ranged from 635 million to 541 million years ago. This period featured a variety of large, complex organisms, most of which are hard to link to any modern species. Scientists previously thought that these organisms formed simple ecosystems characterized by only a few basic feeding methods, said Simon Darroch, a researcher at Vanderbilt University in Nashville, Tenn., and a member of the research team. The new study, published Nov. 27, in the journal Science Advances, suggests they were capable of more types of feeding. “For many years, scientists have assumed that Earth’s oldest complex organisms, which lived over half a billion years ago, fed in only one or two different ways. Our study has shown this to be untrue. Tribrachidium and perhaps other species were capable of suspension feeding. This demonstrates that, contrary to our expectations, some of the first ecosystems were actually quite complex,” said Darroch. Co-author Marc Laflamme of the University of Toronto Mississauga added: “Tribrachidium doesn’t look like any modern species, and so it has been really hard to work out what it was like when it was alive. The application of cutting-edge techniques, such as CT scanning and computational fluid dynamics, allowed us to determine, for the first time, how this long-extinct organism fed.” Computational fluid dynamics is a method for simulating fluid flows that is commonly used in engineering, for example in aircraft design, but this is among the first applications of the technique in paleontology. “The computer simulations we ran allowed us to test competing theories for feeding in Tribrachidium. This approach has great potential for improving our understanding of many extinct organisms,” said Imran Rahman of the University of Bristol, one of the collaborators. “Methods for digitally analyzing fossils in 3D have become increasingly widespread and accessible over the last 20 years. We can now use these data to address any number of questions about the biology and ecology of ancient and modern organisms,” added co-author Rachel Racicot of the Natural History Museum of Los Angeles County. finds