The Earliest Known Metazoans

In 1964 S.B. Mirsa, a graduate student at Memorial University in Newfoundland, discovered a group of well-preserved fossilized soft-body animals. Subsequent research revealed the fauna were from the Ediacaran Period 635-542 million years ago.

Ediacaran was not officially recognized as a geological period until 2004, the first new period in over 120 years. The period is named after the Ediacaran Hills in Southern Australia, which take their name from aborigine Idiyakra, “water is present”, the type locality for the fauna. Over the globe 25 localities have been discovered that possess fossils from this period. The localities are typically grouped into three types based assemblage of organisms they possess. These organisms represent the oldest known complex multicellular organisms predating the Cambrian Explosion by several million years.

The site that Mirsa discovered and described is Mistaken Point on the southern tip of Avalon Peninsula in Newfoundland. The deposit dates to 550-560 mya and of all the localities has the largest quantity of fossils. Organisms preserved here inhabited a muddy seafloor and were covered by a fine-grain volcanic ash that preserved the fossils in exquisite detail.

I mention Mistaken Point for two reasons. First the biota were deep-dwelling and well below the photosynthetic zone. Perhaps not as deep as the typical organisms we discuss here, they likely represented organisms on a continental shelf fauna. The second reason I mention this is that the recent American Society for Limnology and Oceanography meeting in St. Johns Newfoundland allowed me the oppurtunity to visit this Mecca of Science and see the fossils first hand.

River be damned! The Ediacaran awaits!

The trip require a a quarter day drive down the Newfoundland coast on the Irish Loop. A turn off the highway had colleagues and I driving down a 9 mile unpaved road in a rental hybrid poorly equipped for such an adventure. At the parking lot a 4-6 mile round trip hike is awaited us. The hike over rolling hills right on the beautiful Avalon coast while not strenuous did require wading across a sizable stream (small river?) with Newfoundland’s finest and potentially coldest waters. A hiker and son returning the opposite direction did much to curtail our enthusiasm for the site. Both expressed disappointment, claiming to see only a few small and poorly preserved things.

Thankfully the hiker and son were wrong. The Mistaken point fauna is nothing short of spectacular! The fossils are large, dense, interesting, and well-preserved. I stood in total awe realizing I was viewing a organisms that inhabited the deep 560 million years ago. These animals were the among the first complex organisms and standing there I was viewing a pivotal moment in the history of life.

Now for the best part! Below the fold are pictures of these organisms.

Spindle-Shaped Form

Spindle/Stalk Form with potential holdfast like structure

Another holdfast like structure

???

The best preserved Spindle-Shaped Form observed