Paleozoic Period

Paleozoic Period (Carboniferous Era 359 – 318 Million Years Ago) Time travellers, finally it might be worth a trip to this period. The land has plants and the weather is definitely good for sunbathing. The beginning of the Carboniferous Era generally had a tropical, and humid climate throughout the year. A large expanse of ocean covered the entire surface of the globe. Travel destinations were limited to one land mass, Pangea, the massive supercontinent. Shallow, warm, marine waters often flooded the continents and salty swamps were common. In the ocean there wasn’t much seaweed. Crinoids (featherstars) dominate the shallow water habitat. The base of their stalks was modified to anchor the animal securely in the soft sediment. They evolved a variety of stalk heights, which enabled them to capture food at different levels above the sea floor. Crinoids were relative skyscrapers in the community, sometimes towering up to two meters (6.5 feet). Lacy bryozoans occupied a lower level. The prospects of getting a resort fishing adventure going had definitely improved. The heavily armoured fish from the Devonian became extinct, being replaced with fish fauna that looked more modern. Small bony fishes weaved among the crinoid stalks. Sharks cruised above the crinoid forests on the lookout for a meal. Below them, huge numbers of brachiopods (mollusc-like shelly creatures) monopolized the muddy bottom. Trilobites were increasingly scarce, but a few scuttled about like crabs, while tiny foraminifer shellfish were abundant in the mud. The sea levels all over the world fluctuated because of the presence of two large ice sheets at the southern pole. The uplift of the continents caused swamp forests to spread. Thick vegetation was pressed down on the bottom of swamps, eventually to become modern-day coal and oil deposits. Like all eras, the end was marked with a big extinction event after a drying trend, most likely caused by the advance of glaciers. 13 The Paleozoic Era – Permian Period 286-250 million years ago The end of the big extinction event saw the remaining species boom again and start to diversify. The continents continued to shift around slowly with what is now North America along the equator, and Africa at the South Pole. Australia lay beneath an ice cap at the start of the Permian and Victoria was swathed in a slow-moving ice-sheet. Desert areas covered the northern inland part of the supercontinent that Australia was a part of. Low lying and swampy shallow seas were still common. The oceans teemed with fish and invertebrates. Seas were dominated by crinoids, echinoderms, brachiopods, and planktonic graptolites. Permian reefs were generally mud mounds of carbonate sludge or reef mounds partly built up by larger skeleton building organisms including bryozoans. Importantly, corals had appeared but they were low growing rugose and tabulate corals. During this era animals, fungi, and plants colonized the land, the insects took to the air, and its swampy so bring the Aerogard. The early amphibian-like animals eventually gave rise to the reptiles. By the end of the period pine forests were common. Finally, the earth looked like something we might recognise today. At the end of the Permian, 251.4 million years ago, the biggest natural disaster in history killed 90 per cent of the planet’s species. The cause is not yet known – perhaps an asteroid impact, stagnant oceans, massive volcanic eruptions, a significant fall in sea levels, or a combination of these. Many marine groups became extinct including tabulate and rugose corals, eurypterids, sponges, blastoid echinoderms, graptolites, trilobites, and most crinoid species. The Permian extinction left “…crumbling blocks of lifeless rock, around which no fishes swam. Instead, there sprouted, here and there, the squat and flaccid mushroom shapes of pale stromatolites. These glowed a ghost-like green against the garish, toxic shades of fungal blooms. The seas were weirdly clear. The rich planktonic rains of fusilinid forams, diatoms, and softer-bodied forms, uncounted and unknown, were gone. All ocean life was strangled by anoxic waters reaching through unheard-of depths; and nothing lived that did not feed on death.” Time travellers, cancel those travel plans. For the following ten million years, there were no reefs. This period is known as the Early Triassic Reef Gap. 14 Crinoids (feather stars) Crinoids feed by filtering small particles of food from the sea water with their feather like arms. In most living species, the arms branch several times, producing anything up to two hundred branches in total. The arms are jointed, and lined by smaller feather-like appendages, or pinnules. They are covered with a sticky mucus that traps any food that floats past. Once they have caught a particle of food, the tube feet can flick it into the groove in their arms, where the cilia (hairs) are able to propel the stream of mucus towards the mouth. Divers can see this happening if they have the patience to look for it at night. Feather stars have separate sexes which are impossible to tell apart. The pinnules hold the eggs which will eventually rupture to release into the surrounding sea water. In most species, larvae don‘t look much like the adult. These swim in the water column for 10-40 days and eventually settle as baby feather stars. The feather star grows gradually to become an adult feather star in 8 –12 months. Some species develop directly (have no different-looking larval stage) and are nourished by food in the egg supplied by the mother. The majority of living crinoids are free-swimming and have only small stalk which is a reminder of their past evolution when most were attached to the bottom. Crinoids were much more numerous both in species and numbers in the past. Crinoid fossil fragments make up the majority of many old limestone beds. In fossils they usually only have five arms, but most living species have doubled their structure, having ten arms in total. The earliest known group crinoids lived about 400 million years ago and they evolved into many species. About 250 million years ago there was a massive extinction event. The crinoids with flexible arms that could filter-feed very efficiently survived and became very widespread. A response to heavy predation possibly caused them to further evolve by separating from the bottom to improve mobility. The crinoids we see today are just a small fragment of the species of feather star that once carpeted the bottom of our ancient oceans. Looks like a plant?, well this deep water crinoid was photographed crawling along the bottom using its feather arms like feet 15 Ancient Sharks (Hexanchiformes) The various types of sharks were at a high c. 360 mya, but by the ending of this period (also known as Carboniferous) and the beginning of the Permian age, many of them had become extinct. The rest were saved thanks to a rise in the numbers and variety of ray-finned fish. Since they make for great shark food, sharks once again flourished and the evolution of sharks continued. Hexanchiformes are an ancient living shark from 260-300 mya. Their 2 families are Frilled sharks (Chlamydoselachidae), which look like eels, and Cow Sharks. This order includes some of the most primitive looking sharks that swim in our oceans today. Besides rows of scary needle teeth, one of the other ‘primitive’ features of these sharks is the presence of six or seven gill slits. The Frilled shark Frilled Sharks resemble the ancient shark, Xenacanthus. The teeth of the Frilled shark closely resemble those of species which dates back to the Carboniferous Period – over 340 million years. There are 4 species of Frilled sharks. Due to the very deep water that Hexanchiform sharks inhabit, little is known about these mysterious sharks. One was recently caught off the NSW coast by a trawler, fishing near Lakes Entrance in Gippsland caught in water more than a kilometre deep. It has up to 47 rows of teeth, grows to lengths of two metres and is mostly found in ocean depths below 400 metres – or in a Taiwanese fish market. Frilled sharks have 6 to 12 pups per litter. The frilled shark has six gills on either side that wrap around and almost join underneath. These are what give the shark its name. It is capable of swallowing prey more than half its size and it eats squid and octopus. Like an eel, it can turn back on itself. Its teeth are described as backwards needles and it is capable of extending its jaw so that it can swallow everything whole. “I remember seeing one off Victoria a while ago and also when I walked through fish markets in Taiwan,” said William White, research scientist at the Australian National Fish Collection, CSIRO. “I know they occasionally see them at the surface, because a lot make vertical migrations at night time, as they follow prey up and down in the water column,” he said, adding that its eel-like swimming motion makes it quite unique among sharks. The species is more likely to be found in cool, temperate waters and seems to avoid warm water, said Mark Meekan, shark biologist at the Australian Institute of Marine Science. “There are usually three main spots it is found, in waters off New Zealand, near Japan and along the coast of the British Isles, down through Spain into northern Africa. However, there are some maps that show distributions that encompass the Victorian coast,” he said. 16 Cow Sharks The other Hexanchiforms are relative newbies, evolving about 95 million years ago, after dinosaurs disappeared. They are located throughout the world. The Broadnose Sevengill inhabits shallower water than other cow sharks thus making observation and study possible. Cow sharks have anywhere from 6 to 108 pups. They hunt mostly at night, attacking smaller sharks in the water column. They will also eat anything else they can catch, fish, crabs and carrion. Cow sharks skeletons resemble those of ancient extinct forms, with few modern adaptations. Their digestive systems are also unspecialised and primitive. Their feeding behaviour seems to differ from place to place, with the species schooling to attack seals only in South Africa. It isn’t especially aggressive or powerful and attacks so far haven’t been fatal. In captivity it has bitten divers and may be responsible for some infrequent attacks on swimmers. Attacks on human bathers and divers are very infrequent and have largely been recorded from the South Island of New Zealand. The biting incidents may be territorial rather than hunting responses. They are common in embayments like Norfolk Bay in Tasmania and Port Phillip Bay in Victoria, but they are mostly active at night and are rarely seen. Divers have encountered them on the deep and dark wreck of the Lake Illawarra under the Tasman Bridge in Tasmania. They are also seen at night off Rye Pier in Victoria and off Phillip Island. They are also seen in the Rip, Cape Schanck and Flinders. This species was responsible for an attack on a surfer at Flinders recently. They are also commonly fished, being caught by anglers off Point Lonsdale and Queenscliff. They are also common in the Illawarra where they regularly get caught by the NSW beach meshing program (92 caught in NSW from 1991-2007, 59 in the Illawarra and 14 in Sydney). They are under heavy game fishing pressure in some areas. Chimaeras The DNA of the elephant shark hasn’t changed much in 400 million years, now that’s a winning design. The elephant shark uses an elephant-like trunk to rummage for crustaceans on the ocean floor at depths of around 200 metres. To the ancient Greeks, Chimaera was a mythological monster made up of the parts of other animals. Sharks evolved from bony vertebrates around 450 million years ago. Elephant sharks are not a true shark but a chimaera, a small group of fish that diverged from sharks, rays and skates around 420 million years ago. A comparison has been made of the genomes of the elephant shark, humans and other vertebrates. The study found that the genetic code of the elephant shark isn’t complicated, being less than a third that of humans. The genome could hold insights into how bones are formed, which could help the fight against the bone disease osteoporosis. More secrets may lie in the elephant shark’s immune system. Its defences seem rudimentary, lacking the kind of immune cells found in humans that combat viral and bacterial infection. Despite this, its immune system is clearly robust and enables the fish to live a long life. Maybe there are some secrets for a longer human life.