Canadian Rockhound: World's Biggest Trilobite

Complete trilobite
Figure 1. Complete fossil.

Canadian paleontologists working in northern Manitoba have discovered the world's largest recorded complete trilobite fossil. The 445 million-year-old fossil is over 70 cm in length, 70% longer than the previous record holder. Trilobites, an extinct group of sea-dwelling arthropods (joint-legged animals) distantly related to crabs, scorpions and insects, are among the most familiar fossils of the Paleozoic Era (about 545-250 million years ago). Their fossil remains are eagerly sought by amateur and professional paleontologists. Most trilobites were between 3 and 10 cm long.

The giant trilobite was found and recovered during a long-term field project investigating fossil life along a Late Ordovician age tropical coast.

Crew
Figure 2. 1998 field crew (left to right) David Wright, Graham Young, Bob Elias, Dave Rudkin, Curtis Moffat, Janis Klapecki, Ed Dobrzanski.

The project is led by Graham Young (Manitoba Museum of Man & Nature) and Bob Elias (University of Manitoba); the trilobites are being studied by Dave Rudkin (Royal Ontario Museum).

An Ancient Giant

"As a Museum, we are primarily an educational facility and this trilobite provides us with an excellent opportunity to educate our visitors about a fossil animal group other than the dinosaurs. We have found a very unusual specimen that illustrates some of the diversity and weirdness of ancient life." – Dr. Graham Young, Museum Associate Curator of Geology and Paleontology.

Science is 99% hard work and 1% inspiration, and most scientists only rarely have the thrill of making a significant discovery. For the group of scientists who discovered the world's largest known trilobite, the intense excitement of uncovering this incredible specimen made the preliminary fieldwork, delicate quarrying to extract the fossil, and subsequent research and specimen preparation all worthwhile.

Diorama
Figure 3. Reconstruction of a trilobite living on the sea bottom.

Trilobites, an extinct group of sea-dwelling arthropods (joint-legged animals) distantly related to crabs, scorpions and insects, are among the most familiar fossils of the Paleozoic Era (about 250 - 570 million years ago). Rudkin noted that "The majority of trilobites were between three and ten centimeters long. Their fossil remains are eagerly sought by amateur and professional paleontoligists alike." However, there is nothing familiar about this particular specimen! "It is an important and amazing find" says Dr. Bob Elias.

Measuring 72 centimetres in length, this giant trilobite is nearly 30 centimetres longer than the largest previously known to science! It also dwarfs most members of the trilobite group, typically ranging in size from three to ten centimetres.

Figure 4. Scale drawings of giant trilobites from northern Manitoba (a,c) other large species reported in the literature (b,d,e) and a typical large trilobite (f). A house cat is shown for size comparison.

"A trilobite of this size really is an amazing discovery," said Dr. Graham Young, Museum Associate Curator of Geology and Paleontology and member of the team of scientists that uncovered the creature. "The arthropods are animals without backbones so normally they are quite small. For small creatures like bugs, this structure works very well. However, in large creatures, this overall design raises questions about how blood is circulated throughout the body, how the nervous system functions and how oxygen is transported through the tissue."

Long before unearthing this scientific treasure embedded in Churchill's rocky shoreline, Young and Dr. Bob Elias of the University of Manitoba had been conducting preliminary fieldwork in the area. For the 1998 field season, the team included Young's associate Ed Dobrzanski, Museum Collections Manager Janis Klapecki, volunteer David Wright, University of Manitoba summer student Curtis Moffat and David Rudkin, Assistant Curator of Palaeobiology of the Royal Ontario Museum.

In July of that year, the eager team of scientists set out for the northern Manitoba site. They hoped to find fossils similar to those uncovered by digs of the past, like the 43 centimetre-long trilobite excavated from the area in the 1980s.

The Excavation Process

"Do you want to see something amazing?" said Rudkin with exuberance, after returning from the field area far from the rest of the group, which he had chosen for the third day of the dig. Emerging from the deposited limestone was a trilobite tail much larger than any they had seen before. "If more of it is here, this could be the biggest trilobite anywhere."

As the largest known trilobite and a member of a species previously unknown to science, this specimen is truly unique. Its size contradicts the idea that larger animals are more commonly associated with colder climates. Although Churchill is now subarctic, millions of years ago when trilobites ruled the region, it was submerged in salty sea water, located on the equator and had a tropical climate.

Excavation 1
Figure 5. The trilobite, as discovered, is still largely hidden within the limestone bedrock.

Uncovering fossil
Figure 6. A lot of hammer and chisel work is needed to uncover the fossil and lever it out of the rock.

Lifting specimen out

Figure 7. The specimen is lifted out in four large pieces for transportation to Winnipeg, Manitoba, Canada.

This important scientific discovery will provide the Paleontology field with increased insight into this diverse group of fossil animals.

The giant trilobite is on display in Timeless Treasures: Opening the Vaults, a stunning exhibition of unique and exotic heirlooms, archaeological artifacts, scientific specimens and rarely displayed curiosity items from the collections of the Museum and heritage organizations throughout the province.

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The preceding article was reformatted for this issue. The information in the article is also available on the Internet through the Manitoba Museum of Man and Nature website [www.manitobamuseum.mb.ca]. All photographs were provided courtesy of the Manitoba Museum of Man and Nature. This article was reprinted in the Canadian Rockhound with permission.