Fossils of 10 unknown species found by sewage plant

Paleontologists sifted through thousands of 3 to 3.7 million year-old fossils in New Zealand, which also included great white shark teeth and the spine of an extinct sawshark.
A large group of white and gray fossils laid out on a blue tarp.
Some of the 266 fossil species found during a wastewater plant excavation in New Zealand. Bruce Hayward

Fossils and ancient relics of the past turn up in some weird places, from the stretches of the New Jersey shore and random Walmarts to Swedish lakes and even the moon. They are also common finds during major excavations. More than 200 fossil species were found in a mound of sand beneath Mangere Wastewater Treatment Plant in Auckland, New Zealand.

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The fossils include some of the world’s oldest known flax snails, an extinct sawshark spine, great white shark teeth, and at least 10 previously known species. They are described in a study published on August 28 in the New Zealand Journal of Geology and Geophysics. According to the team, this treasure trove represents one of the richest and most diverse groups of three-million-year-old animal fossils ever found in New Zealand. 

They were first uncovered in 2020 by Watercare, Auckland’s water and wastewater service. The company was excavating two large vertical shafts as part of an upgrade to the major pipeline that brings raw sewage from the center of the city to a plant for treatment. While digging, they came upon the ancient shell bed dating back at least three million years. Geologist and study co-author Bruce Hayward from Auckland-based research group Geomarine Research said that the discovery was similar to “finding gold right on your doorstep.”

Watercare and their contractors brought the shelly sand over to a nearby field so that Hayward and a team of paleontologists led by Auckland Museum curator Wilma Blom could carefully sift through it. The team examined more than 300,000 fossils of 266 species, and several thousand specimens have been brought to this museum.

The fossils were likely deposited between 3 and 3.7 million years ago into a subtidal channel that would become present-day Manukau Harbour. “At that time, sea level was slightly higher than it is today as the world was also several degrees warmer than now,” Hayward said in a statement. “As a result, the fossils include a number of subtropical species, whose relatives today live in the warmer waters around the Kermadec and Norfolk islands.”

In the study, the team describes 266 different fossil species and some rare finds, including a baleen whale vertebrae, dental plates of eagle rays, and a broken sperm whale tooth. The roughly 10 previously unknown species described and named in future research. 

[Related: Fossil trove in Wales is a 462-million-year-old world of wee sea creatures.]

One aspect of this fossil bed that surprised the team is that the fossilized remains belong to animals that lived in many different environments that were eventually brought together in the ancient marine channel through strong currents and waves. Ten specimens of an iconic  mollusk called the New Zealand flax snail likely lived on the land next to the ancient subtidal channel and were washed out to sea by storm runoff, according to the team. Other specimens were likely attached to hard rocky shorelines, while others were washed into the channel from areas further offshore.  

The team dedicated the work to New Zealand’s leading molluscan fossil expert Alan Beu, who was working on the fossils before he died earlier this year.