The Zuiyō Maru Carcass ("New Nessie")

The Zuiyō Maru was a 2,460-ton trawler owned by the Taiyo Fishery Company of Tokyo. In April 1977 it was trawling for mackerel east of Christchurch, New Zealand.

25 April 1977. About 10:40 in the morning. At a depth of about 300 metres, something large became tangled in the nets. As it was hoisted above the deck, assistant production manager Michihiko Yano told the captain, Akira Tanaka, that it was a rotten whale. Then Yano got a better look. He became less sure. It was already being readied for disposal when the slimy carcass slipped from its ropes and fell suddenly onto the deck.

Yano measured it. About 10 metres long. A small head on a neck of about 1.5 metres. A tail of about 2 metres. Four large, reddish fins. A white, sticky, fat-like substance covered much of the body, with reddish muscle underneath. The internal organs were gone. Its weight was estimated at about 1,800 kg. About 17 crew members saw it. They nicknamed it "Nessie".

With a camera borrowed from a shipmate, Yano took five colour photographs, some while it hung from the wire, others as it lay on deck. He pulled 42 horny fibers from a front fin. The smell was intense, unlike any fish. About an hour after it came aboard, the captain had it thrown back into the sea.

Back in Tokyo, Yano showed the photographs to ichthyologist Fujiro Yasuda. On 20 July 1977, Japan's Sea Day, they were made public. The press called the creature "New Nessie". A national plesiosaur craze followed, with wind-up toys, advertising campaigns and, on 2 November, a commemorative postage stamp. Taiyo sent its vessels to find the carcass again. None did.

Some scientists spoke boldly. Tokio Shikama of Yokohama National University said: "It has to be a plesiosaurus." Yasuda said: "If it is a shark, it is a species unknown to science." Others urged caution. Alwyne Wheeler of the British Museum of Natural History warned: "Greater experts than the Japanese fishermen have been foiled by the similarity of shark remains to a plesiosaur."

In September 1977 a research team of more than a dozen biochemists, ichthyologists and paleontologists began meeting. Nine papers followed in July 1978. The horny fibers had an amino-acid makeup almost identical to basking shark elastoidin, a protein found only in sharks and rays. Heated to 63 °C, they shrank to about a third of their length. The photographs showed fin rays rather than finger bones, a visible dorsal fin and too few neck vertebrae for a plesiosaur. Hasegawa and Uyeno concluded it was "more than likely a carcass belonging to a large size shark."

The accepted answer is a decomposed basking shark. As one rots, the jaws and gill arches fall away, leaving a small braincase on a long spine. The dorsal fin and lower tail lobe drop off first. What remains is a "pseudoplesiosaur". That same September, a confirmed basking shark stranded at Nemuro, Hokkaido, strikingly like the Zuiyō Maru carcass. Glen Kuban found "inaccuracies and apparent pro-plesiosaur bias" in Yano's sketch, drawn from memory about two months later. Creation-science writers kept arguing for a marine reptile. Even so, Answers in Genesis now lists the case among arguments to avoid.

The carcass was never recovered. Five photographs remain. Its shadow falls across Godzilla vs. King Ghidorah and Godzilla (2014). In Christchurch, The Press recalled it being called "a plessie, a taniwha, and New Zealand's answer to the Loch Ness monster". In 2020 Darren Naish put it plainly: "the evidence for it being a Basking shark is very strong."