Terrestrial fossils are the remains of plants and animals that lived on land. The best places to find them are in lake, swamp and river deposits. New Zealand has many terrestrial sedimentary rocks, but they are not as rich in fossils as marine sediments.
Coal deposits are widespread. These originate from wood and leaves that accumulated in swamps and forests between 70 and 45 million years ago (Ma). Younger lignite and lake sediments (20–10 Ma) also have fossils. Parts of fossil plants are well known from these rocks, especially wood, leaves, pollen and spores, along with rare fruits, seeds, flowers and resin (amber). Animal fossils other than freshwater and terrestrial molluscs are extremely rare.
New Zealand’s oldest terrestrial fossils
The oldest terrestrial animal fossil is Middle Triassic, about 245 million years old. This is a single fossil bone, from a large salamander-like amphibian collected from rocks in the Titirangi Stream, a tributary of Southland’s Mataura River.
The oldest leaf fossils are called Glossopteris. They are about 255 million years old. The oldest fossil pollen and spores, collected from the same rocks within Southland’s Wairaki Hills, are of similar age.
Fossils of insects, including beetles, are extremely rare, yet fragments attributed to insects are commonly found with fossil pollen and spores. New Zealand’s oldest beetle fossil is a 145-million-year-old wing case, collected near Port Waikato.
New Zealand dinosaur fossils are known from three localities, and are about 145, 75 and 65 million years old. Although dinosaurs lived exclusively on land, it is interesting to note that fossils have been unearthed from shallow sea sediments, not terrestrial (lake or river) sediments.
The 75-million-year-old dinosaurs are about 10 million years younger than the separation of Zealandia from Gondwana. Over 10 million years of isolation they must have evolved considerably from their original Gondwanan ancestors, making them distinctly Zealandian dinosaurs. Only fragmentary bone fossils have been found, so the detailed identity of these dinosaurs remains obscure.
Sauropods and theropods
New Zealand’s first dinosaur fossil was found by Joan Wiffen and her friends in the late 1970s. Identification of this first find, the tail vertebra of a theropod dinosaur, was confirmed in 1980 by Australian vertebrate paleontologist Ralph Molnar. After that, Joan Wiffen found other bones which showed that 75 million years ago a community of dinosaurs existed including sauropods, a theropod and armoured dinosaurs. At least six different species have been discovered in the Mangahouanga Stream, inland Hawke’s Bay.
Scientists know that dinosaurs and mammals lived alongside each other. If dinosaurs existed on Zealandia then it follows that other reptiles and mammals were also living there. However, so far no Mesozoic (251–65 Ma) mammal fossils have been found in New Zealand. It is probably only a matter of time before they are.
Other reptile fossils
Fragments of fossil crocodile bones and teeth have been found in at least one locality in Central Otago. These are 20–15 million years old. Turtle fossils are recorded from a number of localities, but so far there are no confirmed discoveries of fossil snakes. The fossil record of tuatara, lizards and frogs is surprisingly poor, with no fossils older than 2 million years.