Royal Ontario Museum Department of Museum Volunteers Data Sheet. Early Life Burgess Shale

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1 Royal Ontario Museum Department of Museum Volunteers Data Sheet Early Life Burgess Shale High on the Western slope of the Canadian Rockies lie the fossilized remains of some of the earliest known multicellular life on Earth. 505 million years ago, the land was completely devoid of life. All life was in the sea. The animals preserved in the Burgess Shale lived near the equator in warm, shallow seas on the continental margin of North America. Visitors may enjoy watching the digital kiosk presentation located near the display cases. How did the fossils, found in Yoho National Park about 90 km east of Banff find their way to a ridge between two mountains East of the Great Divide? The earth s crust moved: first to the north and east, and then up as the Pacific crustal plate forced itself underneath the western side of the North American Plate. Why is the Burgess Shale so important to the ROM? When they were recognized by Charles Walcott of the Smithsonian Institution in 1909, they represented the first evidence of the rapid appearance ( explosion ) of multicellular life during the Cambrian age (540 to 490 million years ago), near the beginning of the Paleozoic era. The ROM has the world s best and most comprehensive collection of Burgess Shale fossils. Starting in 1975 Desmond Collins, retired Curator of Invertebrate Paleontology, spent 25 years collecting and studying these fossils. Jean-Bernard Caron and David Rudkin continue this work today. These fossils are widely believed to contain the world's finest Cambrian-aged fossils. Usually fossils are dismembered, squashed and/or deformed during the formation of the sedimentary stone in which they are found, leaving paleontologists to deduce what these animals really looked like and how they lived. Think road kill. The 3-dimensional structure of the entire body of some of the Burgess Shale animals is preserved in stone. Even in Pompeii internal body structures were not preserved. How were these fossils formed? Most of the Burgess Shale fossils are the remains of bottom-dwelling (benthic) animals that were carried by flows of extremely fine mud over the edge of a reef made of algae (there were no corals at the time) into an oxygen poor area of the ocean floor. The lack of decay-causing oxygen preserved even the soft squishy bits of their bodies. It is believed that the fine grained clay that engulfed these animals was forced into every appendage, crack and crevice until the contents of some stomachs and even the internal and external organs of jellyfish are preserved in stone. How do they fit into the history of life on earth? The earth was formed about 4.5 billion years ago. The oldest sedimentary rocks, the type of rocks in which fossils are found, are 3.75 billion years old. The remains of the first individual cells (bacteria and archaea called prokaryotes) date from 3.7 billion years ago. So successful have the prokaryotes been that this single cell life accounts for most of the biomass in the world today. Stromatolites are a good example of this type of single celled life. Stromatolites are tussocks created by the build up of mats of oxygen-forming, chlorophyll-containing cyanobacteria (blue-green algae). The cyanobacteria formed a layer of sticky slime, which was covered with a layer of mud. Filaments of cyanobacteria grew up through the mud and formed another layer of slime. Over time, the layers built up and hardened to form rocky mounds or columns. These remarkable organisms are found in 3.5 billion year old fossils and have been so successful they can still be found in places in Africa and Australia today. In fact, Revised: August 28, 2012 Page 1 of 6

2 these were the first major polluters as oxygen was toxic to most types of life at the time. The bumpy white rock outside the second floor elevator in the Rotunda of the ROM is a 1.8 billion year old stromatolite fossil from Thunder Bay. Three billion years after the initial appearance of prokaryotes (610 to 540 million years ago), multicellular life appeared simultaneously all over the earth as soft-bodied organisms (Ediacaran and Vendian biota) followed by small shelly fauna with bits of mineralized matter in small and separate places all over their bodies. It is almost as though in experiments created by changing environmental conditions, two complete, unique sets of multicellular life appeared, lived for millions of years and then disappeared leaving only fossils to attest to their existence. There is no immediate apparent link between these fossils and macroscopic life on earth today, although it has been suggested that the soft bodied Ediacaran and Vendian biota may be related to jellyfish. The ROM s Jean- Bernard Caron and David Rudkin have proposed that two Burgess Shale fossils (Odontogriphus and Wiwaxia) are related to each other and evolved from the same Ediacaran animal. Dramatically, at the beginning of the Cambrian period about 545 million years ago, the macroscopic ancestors of all multicellular animals alive on the earth today appear. During the Cambrian period, complex creatures with skeletons, eyes and limbs emerged with amazing suddenness, including our ancestor, Pikaia Gracilens, the first animal with a spinal chord. The early Cambrian explosion is evidenced by the Chingziang Shale in China; the middle Cambrian explosion is evidenced by the Burgess Shale. Why is the Burgess Shale so important? In a 14.5 km wide geologic formation, all modern phyla of animals, many algae, Protozoa, and Fungus-like organisms are found. Accompanying them are animals with about 15 to 20 body types that cannot be matched with any group known today. Animals like Opabinia with 5 eyes with a single claw/mouth attached to a trunk like appendage, and Hallucucegenia with spikes sticking out from top and bottom so that paleontologists had trouble deciding which way was up. Many of these unique animals thrived for hundreds of millions of years and then, like the Vendians before them, were eradicated during the Permian extinction 240 million years ago. Many that were extremely rare survived, then thrived. Since the beginning of the Triassic (250 million years ago), the number of species in each modern phylum found in the Burgess Shale has increased, but the number of phyla (anatomical plans) remains unchanged, evidence that suggests that evolution of life on Earth has been characterized by rapid diversification and random extinction rather than by an orderly progression of "survival of the fittest". Suggestions for touring the Burgess Shale Most of these fossils are small for touring purposes. All are dark impressions on a background of a fine, light grey shale. There are two cases The Raymond Quarry on the north wall; and the Walcott Quarry on the east wall. Each of the cases has a small diorama showing the life that appears in the individual fossils contained in the case beneath. These dioramas were painted by Marianne Collins, whose accurate, artistic depictions of these life forms are considered to be the best available in the literature. Some of the major specimens are described below. The Raymond Quarry Anomalocaris canadensis, meaning Odd or Anomalous Canadian shrimp Located at the top left of the case. The Tyrannosaurus rex of the Burgess Shale. Largest specimens were 2 m (6.6 feet) long. Member of the Dinocarids class (terrible shrimp), the major predators of the time. Two large, spiny, curved claws in front of the mouth originally were found detached from the body. It was thought they represented an early type of shrimp. Hence the name odd shrimp. Had large eyes mounted on stalks. Body half-flanked with a series of swimming lobes that could probably be moved in a wave-like formation, allowing it to move at great speeds or to 'hover'. Revised: August 28, 2012 Page 2 of 6

3 The mouth had a peculiar circular external structure with an internal ring of hard sharp teeth that did not meet in the middle but could crush the shell of an arthropod such as a trilobite. Misinterpreted for many years because only incomplete parts found. Four separate pieces were originally named as four species of arthropod until Dr Collins found a complete specimen. Ottoia prolifica, meaning penis worm; a priapulid worm Located at the middle front of the case. There are three Ottoia specimens displayed. A burrower that hunted prey with its eversible proboscis. Also appears to have scavenged on dead organisms. The spines on the proboscis have been interpreted as teeth used to capture prey. Its mode of life is uncertain, but it is thought to have been an active burrower, moving through the sediment after prey, and is believed to have lived within a U- shaped burrow that it constructed in the substrate. From that place of relative safety, it could extend its proboscis in search of prey. Gut contents show that this worm was a predator, generally swallowing its prey head-first. They also show evidence of cannibalism, which is common in priapulids today. The Walcott Quarry Pikaia gracilens Located at the top right of the case. Named after Pika Peak, a mountain in Alberta. The first known chordate (backboned animal), and may be the ancestor of all modern vertebrates, but this theory is fiercely debated amongst scientists. Averaging about 3.8 cm (1.5 inches) in length, swam above the sea floor using its body and an expanded tail fin. May have filtered particles from the water as it swam along. Its "tentacles" may be comparable to those in the present-day hagfish, a jawless chordate.. Revised: August 28, 2012 Page 3 of 6

4 Trilobites Located in the centre of the case, there are two reasonably-sized trilobites: o Two trilobites touching their antennae. o Olenoides serratus Trilobites were animals with an external skeleton and three lobes (hence the name) the body was divided into three parts. They were arthropods, the phylum that accounts for about 80% of the macroscopic species found on earth today (think crabs and lobsters, insects, butterflies and centipedes). They had well-defined eyes, and were one of the first animals to develop eyes made of multiple single lenses like those of modern flies. The trilobite head alone displayed many different characteristics. There were differences in ornamentation, number and placement of spines, and the shape of head segments. Lived by siphoning up food from the bottom of the ocean. Once the most common creatures in the world's oceans. They ranged in size from nearly microscopic to 45 cm (18 inches) weighing as much as 4.5 kg (10 pounds). Lived for 300 million years until they became victims of the Permian extinction 250 million years ago. Grew by moulting. As they grew, they shed their hard outer shell and grew a new larger one. Two trilobites touching their antennae Olenoides serratus Laggania cambria Located in the centre of the case. Related to Anomalocaris, described above. Although they are fairly similar in appearance, Laggania can be distinguished by the location of the eyes, its claw type and smaller body. Laggania and Anomalocaris both belong to the Dinocarids class. Its two mouth appendages had long bristle-like spines, it had no fan tail, and its short stalked eyes were behind its mouth appendages. These features are why some scientists don't think Laggania was an apex predator like Anomalocaris that hunted its prey, but rather used its appendages to filter water and sediment on the sea floor for prey. 108 specimens of Laggania are known. Revised: August 28, 2012 Page 4 of 6

5 Wiwaxia corrugata, meaning bristle worm Located in the front right of the case. Named for Wiwaxy Peaks in Yoho National Park. A slug-like animal, covered in hundreds of plates, which would have functioned like armour against predators. Hundreds of complete specimens have been recovered from the Burgess Shale Walcott Quarry, and this genus has also been found in China and other Cambrian localities across the world. The affinity of this animal has fueled an ongoing debate since it was first described in Hypotheses have ranged from some sort of annelid worm to a mollusc. Most recently, new specimens from the ROM s collection have shown that the mouth apparatus is almost identical to the one found in the animal Odontogriphus, described below. Together with Odontogriphus, Wiwaxia probably represents an early stage in the evolution of molluscs, a group known today by animals such as clams and snails. Both animals were most likely grazers and lived at the bottom of the sea. Note that the photo shown at right is not the one shown in the case it is an image of another specimen in the collection. A bilaterally symmetrical animal. Viewed from the top the body was elliptical with no distinct head or tail, and from the front or rear it was almost rectangular. The animal was covered in small ribbed armor plates called sclerites, that lay flat against the body, overlapped so that the rear of one covered the front of the one behind, and formed five main regions the top, with 8-9 rows of sclerites; the upper part of the sides, with 11-12; the lower part of the sides, with 8; the front; and the area nearest the sea-floor, with rows. Most of the sclerites were shaped like oval leaves, but the ventro-lateral ones, nearest the sea-floor, were crescent-shaped, rather like flattened bananas, and formed a single row with the tips pointing down. In addition there were two rows of ribbed spines running from to rear, one along each side of the top surface, and projecting out and slightly upwards, with a slight upwards curve near the tips. Each sclerite was rooted separately in the body; the roots of body sclerites are 40% of the external length or a little less, while the roots of the spines are a little over 25% of the external length; all were rooted in pockets in the skin, rather like the follicles of mammalian hair. Flat underside was soft and unarmored. Usually had two tooth-rows. There was a feeding apparatus that consisted of two (or in rare large specimens three) rows of backward-pointing conical teeth. Even the smallest specimens have this type of apparatus, with two rows containing the same number of teeth as in larger ones. This indicates that Wiwaxia s feeding habits remained the same throughout its life after the larval stage. The feeding apparatus may have acted as a rasp to scrape bacteria off the top of the microbial mat that covered the sea-floor, or as a rake to gather food particles that lay on the sea-floor. Since there is no sign of eyes or tentacles, Wiwaxia may have relied mainly on chemical senses such as smell and taste. Its respiratory system is also unknown. The long dorsal spines may have been a defense against predators, and finds of broken spines suggest that Wiwaxia was attacked. The animal appears to have crawled on the surface of the sea-floor feeding on particles that fell from higher levels of the sea. Wiwaxia shows no signs of legs and was probably too large to move on cilia, so it probably moved by muscular contraction that made its foot ripple. Juveniles may have burrowed into the sea-floor. Wiwaxia grew by expansion rather than addition; that is to say it appears to have maintained a constant complement of scales as it grew, with each sclerite growing larger (by an unspecified means, probably by molting and replacement), and changing slightly in shape, but no new sclerites being inserted. One juvenile specimen appears to be preserved while moulting and not yet completely detached from its discarded armor. Moulting appears to have occurred all at once, as adult specimens shows no signs of interruptions in the sclerite armor that would indicate molting of parts of the armor or of individual sclerites. Revised: August 28, 2012 Page 5 of 6

6 Odontogriphus omalus, meaning weird wonder Located in the front middle of the case. Odontogriphus literally means toothed riddle. Was regarded as one of the most mysterious animals from the Burgess Shale. The first interpretation of this creature was based on a single, poorly preserved specimen, and the morphology and affinity of this species remained unclear. However, the discovery of close to 200 specimens by ROM expeditions over the past 15 years has led to a thorough redescription of this animal. Had an ovoid body. The mouth had a chevron-like structure (X-shape), and was positioned at equal distances from the front edges of the animal. It contains a mouth apparatus called a radula, made up of short rows of small tooth-like elements a typical feature of the mollusca group. Behind the mouth on its underside, it had a muscular, broad foot situated between a series of simple gill-like structures. Lived on the bottom of the sea and probably grazed on bacteria and small algae. Thanks to its radula, foot, and gills, this animal can be recognized as a primitive member of the molluscs. Contrary to modern molluscs, which include squids and land snails, Odontogriphus did not have a shell. Related to Wiwaxia, described above. Opabinia regalis Named after Opabin Pass in Yoho National Park. Had five eyes, a frontal nozzle, or proboscis, a body with serially repeated lateral lobes and gills, and a prominent tail fan. The frontal proboscis was four times longer than the head. It was highly flexible, and had a fused pair of appendages at the end, consisting of two opposing claws with five or six spines each. The trunk was divided into 15 segments, each bearing a pair of lateral lobes in association with gill structures. Was a swimmer. Undulatory waves along its lateral lobes propelled it forward, while it used its tail fan to steer. Probably employed the claws on its flexible nozzle to grasp soft food items and carry them towards its mouth. Bibliography Touring Section, Information Sheet, The Burgess Shale, April 1, 2003 Museum Storytellers, Information Sheet, February 28, 2005 Additional Material for Burgess Shale Data Sheets, April 20, 2005 Gould, Stephen Jay, Wonderful Life, 1989 The Radiation of the First Animals, Dr. Jerry Lipps, Department of Integrative Biology and The Museum of Paleontology, University of California, Berkeley Various Wikipedia articles Revised: August 28, 2012 Page 6 of 6