Dinosaurs In New Zealand

Forest and Bird, Issue 312, 1 May 2004, Page 40

Dinosaurs In

New Zealand

TIM GALLOWAY

After visiting an exhibition of Chinese dinosaurs, ANN GRAEME asked 'Did dinosaurs ever live in New

Zealand?’ Illustrations by

"wos, id a Brontosaurus once lumber over backyard, or a Tyrannosaurus a " terrify the Tararuas, or a Stegosaurus shake the plains of Canterbury? Well, not exactly. There were dinosaurs in New Zealand, lots of them, but it was not New Zealand as we know it. When the earliest dinosaurs first appeared, 250 million years ago, all of Earth’s land was joined in a massive super-continent called Pangaea. With no seas to divide them, the dinosaurs could spread across the whole land mass. Then, about 25 million years later, Pangaea split into two super-continents, the northern Laurasia and the southern Gondwana. Over the millennia, sediment eroded and washed off the eastern margin of Gondwana. Later, in the Jurassic period, this sediment was pushed up again to create the ancestral New ~ Zealand, a huge land mass stretching from New Caledonia to the Campbell Islands. The Jurassic was the heyday of the dinosaurs and they would have spread from Gondwana far across that ancestral New Zealand. For millions of years they would have been the dominant animals in old New Zealand, just as they were in the drier plains of the Northern Hemisphere. There, flash floods and sandstorms buried countless dinosaurs in sediments which remained stable to the present day when erosion (and spades) have revealed the bones to curious fossil hunters. In ancestral New Zealand conditions were not good for preserving fossils. Carcasses

rotted in the warm, moist forests and the humic acid in the boggy ground dissolved the bones. Even so, many dinosaur fossils could have been preserved — had the land remained. But old New Zealand began to erode. For 100 million years the weather whittled it away until most of it was back under the ocean and most of the life on land and the fossils had been destroyed. Dinosaurs became extinct everywhere 65 million years ago. It was not till 50 million years later, at the end of the Miocene period, that the local mountain-building which created present-day New Zealand began. The old sediments on the sea floor were crushed and thrust up again to create the Southern Alps and the mountain chains of the North Island. Volcanoes covered the land with ash. Eroded, buried, uplifted, covered with ash: the chance of finding a dinosaur fossil in present-day New Zealand seems very slim indeed. But someone did! Enter an amateur — Joan Wiffen. Armed with knowledge, enthusiasm, persistence and a measure of good fortune, she found the first dinosaur fossil in New Zealand. Joan was not a professional geologist. Her interest began on family field trips with the local rock and mineral club. She attended night classes in geology, standing in for her sick husband. Then Joan taught herself palaeontology and began fossil hunting. She set her sights on finding a dinosaur fossil, although at the time many scientists did not

think dinosaurs had ever lived in ancestral New Zealand. In 1972 she bought an old geology map of the Taupo region. The notes with it read, ‘reptilian bones found in the Te Hoe valley’. The Te Hoe valley was not far from the family home in Hawkes Bay, and that summer, the family set out for their first trip to look for fossils. ‘Who knows, we may find a dinosaur; quipped Joan. They found the Mangahouanga stream, the site referred to on the map, and clambered down its steep, forest-covered banks. The stream bed was a jumble of boulders, and they were encrusted with fossils — shells, sharks’ teeth, fish scales and bones. The boulders were concretions of sandstone which had been laid down in an estuary some 70 million years ago. Joan and her husband Pont found many fossils of extinct marine reptiles — ferocious mosasaurs and long-necked plesiosaurs and both sea and land turtles. Joan became adept at recognising the bones of animals that lived in the sea and used their limbs for swimming, but none was from a dinosaur. Then, in 1975, she found a fossil vertebra that didn’t fit the patterns. It was not till 1979, however, while visiting the Queensland Museum, that she spotted a dinosaur vertebra that looked like the odd fossil she had found. She sent the museum a cast of the vertebra and in no time came back the response: ‘You've found a dinosaur!’ That first find belonged to a theropod, a member of the group of meat-eating dinosaurs which walked on two legs, and to which the well-known Tyrannosaurus rex belonged. Dinosaurs were land animals. How had this theropod come to lie on a sandy sea

floor amongst the sea shells and fish bones? About 70 million years ago a watercourse, perhaps a broad, shallow river, had emptied out into a bay. After a great storm, the carcass of a theropod may have floated down the muddy river and been washed out to sea, its bones scattered and then buried in the storm-eroded sediment. (See Tim Galloway’s picture sequence below.) Over millions of years, layer upon layer of mud and sand built up and hardened. Then the sea floor was uplifted and the sandstone sediment containing marine fossils and the theropod vertebra came to lie deep in the ranges of Hawkes Bay. There they remained hidden until the Mangahouanga stream chewed down into the bedrock and exposed them. Joan Wiffen also found fossils of hypsilophodonts, plant-eating dinosaurs about the size of a sheep. Evidence of similar species from North America suggests that they lived in small groups, browsing in the forest and were hunted by the theropods. Altogether Joan has found six of the seven New Zealand dinosaur fossils. The evidence of dinosaurs in New Zealand is indisputable, but like all initial fossil discoveries, it is rather insignificant in size. All of Joan’s dinosaur fossils would fit into a shoebox, but this is no reflection of the study and effort that went into their discovery. In 1994 Joan Wiffen was awarded an Honorary Doctorate from Massey University, a fitting recognition for a remarkable woman who put New Zealand on the dinosaur map. — ANN GRAEME is the coordinator of Forest and Bird’s ~~ Kiwi Conservation Club for younger members. Joan Wiffen’s work is featured in a display at Napier Museum and in her ‘ book Valley of the Dragons published in 1991 by Random Century.