- Placoderm existed 400 million years ago, and its remains were uncovered in 1980 on Tolo Channel’s north coast, expanding knowledge of city’s geological history
- Check out our graphic below to learn about how this prehistoric fish’s evolution is connected to modern aquatic animals
A model of Dunkleosteus from the Devonian era is displayed in the Prehistoric Story Room at the Bank of China Tower in Central in 2011. Photo: SCMPScientists estimate more than 99 per cent of all species that have ever existed on Earth are now extinct. Only a handful of them have been preserved as fossils.
Fossils are ancient organisms’ preserved remains or traces of remains. They are usually found in places such as deserts and badlands with eroded sedimentary rocks.
But in Hong Kong, rocks are predominantly granite or volcanic. This makes it tricky to hunt for fossils here, but that does not mean the city does not have any. Palaeontologists definitely need a strong understanding of the geographical area, some perseverance, and tons of luck to come across impressive fossils in Hong Kong.
Scientists discover new dinosaur with slashing tail weapon
Hong Kong’s fossils
The city’s first one was found in 1920; it was an ammonite, which is an extinct shelled sea creature that is a relative of squid, octopus and cuttlefish. The fossil was from the early Jurassic period about 190 million years ago.
But being the first does not mean it is the oldest. That title goes to a marine animal called the placoderm, also called an armoured fish. It existed 400 million years ago. It was uncovered in 1980 on the north coast of the Tolo Channel.
This exciting discovery expanded knowledge of Hong Kong’s geological history, which goes back to the mid-Devonian period about 400 million years ago.
By examining the rocks surrounding these fossils, scientists determined that the environment back then was probably a fluvial plain or estuarine delta.
A fluvial plain is a largely flat landform. It is created when one or more rivers coming from highland regions deposit sediment over a long period of time. An estuarine delta is a partly enclosed wetland where the fresh water meets the salt water and deposits sediment to form a landform shaped like a triangle.
New fossils are still uncovered in Hong Kong. The most recent discovery last year was an ammonite piece and trace fossil containing evidence of previous life forms in mudflats. There is always potential to uncover new traces of prehistoric life and, perhaps, even dinosaurs!
‘Flying Dragon’ dinosaur roamed the southern skies too, scientists say
More about placoderms
Placoderms are a class of prehistoric armoured fish that first appeared during the Silurian period around 443 million years ago. The term placoderm means “plated skin” in Greek. They were among the first animals to evolve jaws. They had internal cartilaginous skeletons like sharks and rays but with an armour-like external skeleton made up of bony plates covering their head and thorax.
Placoderms were the most abundant and diverse group of fish during the Devonian period, which was 419 to 359 million years ago.
From small bottom-dwellers to giant predators, placoderms occupied oceans, rivers and lakes. They could be as small as a few centimetres and as big as great white sharks, which are more than 3 metres long. They fed on almost everything, including seafloor carcasses, invertebrates, other fish and even other placoderms.
Placoderms dominated the aquatic world for more than 200 million years before the first dinosaurs appeared. Unfortunately, like most marine life during this time, they met their demise during the devastating mass extinction at the end of the Devonian period.
Note: A licence from the Antiquities and Monuments Office is required before excavating, removing or looking for fossils in Hong Kong.
Young Post is pleased to partner with Hong Kong Science Museum and Hong Kong Space Museum on our STEM Lab series. Our aim is to encourage you in your pursuit of science. Every month, the two museums will answer your burning questions about the fantastic world around us, the cosmos, and beyond.