Awkward! A pair of turtles turned into fossils during mating! 47 million years later, people still have to watch...

Expert of this article: Liu Yadan, former assistant secretary-general/researcher of China Fisheries Society, national chief scientific communication expert

This article was reviewed by Zou Qiangjun, Director of the Science Promotion Section of Beijing Aquatic Wildlife Rescue Center, and Senior Engineer of Science Communication

Discovering fossils is nothing particularly new, but discovering a pair of mating turtle fossils is shocking!

In Germany's famous "Messel Fossil Pit", a turtle named "Allaeochelys crassesculptata" died biologically about 47 million years ago, but suddenly appeared in front of the world in the form of a fossil, and it was still in a mating state!

Walter G. Joyce et al. / Biology Letters(2012)

How to tell if this pair of turtle fossils were in a mating state? Scientists found that the male tucked his tail under the female partner, with the two tails aligned, which is consistent with the state of courtship for turtles. This is also the first time in history that a fossil of an ancient turtle in a mating state has been found.

You should know that mating is an instantaneous behavior and is the most difficult to record. Among the numerous fossils, only insects can be preserved by the resin that suddenly falls off during mating, which seals them into amber.

Seeing this, I think many people will ask: How did all this happen? Read on to find out↓↓

How can this pair of turtles stay mated?

Experts analyzed the site where the turtle fossils were unearthed, Lake Messel, and found that under normal circumstances, Allaeochelys crassesculptata turtles would mate in the shallow water of the lake. However, there was volcanic activity at the bottom of the lake, and toxic gases such as methane and hydrogen sulfide suddenly erupted. The turtles were mating at the time and were unable to swim, so they gradually sank to the bottom of the lake and inhaled the toxic gases, leading to their death.

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However, many organisms disappear after death, so what conditions can the turtle maintain such instantaneous behavior? There are both external and internal factors.

The external factors are that the lake is inland and the water is not flowing, so the bodies were not washed away. The second reason is that the turtles sank to the bottom of the lake. Due to the lack of oxygen at the bottom of the lake, the bodies did not oxidize and rot. Millions of years of sediments pressed on the bodies layer by layer, sealing them up. The internal reason is that the shells and bones of turtles are very hard, which increases the possibility of them becoming fossils after death.

What animal is its close relative, the pig-nosed turtle?

It is difficult for biologists to reveal much information about biological behavior from fossils. Studying the behavioral characteristics of fossils is relatively complicated. Among the methods including trace fossils, taphonomy, functional morphology and close relative comparison, some experts still choose close relative comparison. In the long river of history, the closest relative of Allaeochelys crassesculptata may be the pig-nosed turtle with the scientific name Carettochelys Insculpta.

The pig-nosed turtle is named after its nose that looks like a pig (if you only look at the nose, you would think it is a pig that can swim). Because it has two claws on each of its limbs, it is also called a two-clawed turtle. It mainly lives in the waters around Australia and Papua New Guinea. Most turtles are amphibians, but some are terrestrial, while the pig-nosed turtle is an aquatic turtle and does not like to go ashore. They are good swimmers and have a unique skill of swimming backwards. In addition to laying eggs, they like to live in water all year round.

Pig-nosed turtle Carettochelys Insculpta | Photo courtesy of Zou Qiangjun

Although this turtle is timid and likes to stay in dark corners, the pig-nosed turtle is a fighting turtle among turtles and has a violent temper. It is not easy for us to watch the fight in the wild, but in artificial breeding places such as the Amphibian Research Institute, we can often see turtles biting and chasing each other, with scars all over their bodies, especially the rear edge of their carapace and tail are incomplete, and the tail vertebrae are exposed.

The breeding season of the pig-nosed turtle is in the dry season, which is between July and October. The embryonic dormancy period is what makes the pig-nosed turtle unique. In the natural environment, after the embryo of the pig-nosed turtle matures, it will enter a dormant state in the egg, waiting for the rainy season flood to come and bring them abundant food, and the hatchlings will break out of the ground.

Tortoises eat birds?

We often hear about big birds eating small turtles, but last year there was a video report of a tortoise killing a small bird. This is an Aldabra giant tortoise, and the bird being eaten is a small black tern chick. In the video, the giant tortoise eats the bird skillfully and looks experienced. However, scientists are not sure whether preying on small birds is a common behavior of giant tortoises. They can only guess that this story happened because the food chain in the habitat is affected by humans.

Aldabra giant tortoise | Mirko Schoenitz

Although most turtles are quiet and slow, it does not mean that they are not agile in hunting. Some turtles are very good at camouflage and hunting, such as the leaf turtle. This is a turtle with the strangest appearance. Its head looks like a leaf and its shell has many edges and corners, which looks like a piece of bark. The leaf turtle is also one of the oldest reptiles in existence. It lives in South America and is huge. Due to the special shape and size of its head, it cannot be retracted into the shell, so it is not a turtle with a retracted head!

Leaf Turtle Chelus fimbriatus | neil_mass

Are turtles endangered?

Nowadays, we see pet turtles entering more and more people's homes, and it feels like turtles are very common in life. But in fact, more than 60% of wild turtles have become endangered species. Scientific and technological personnel are working hard to conduct research and exploration on artificial breeding, and the country has also set up many turtle protection areas, especially sea turtle protection areas. In addition, the country has been promoting the protection of testudinidae animals that are at risk of extinction in my country, such as the "Plan for the Rescue of the Porphyrio cantorii (2019-2035)" released in April 2020.

Many Testudinata species are protected animals that are prohibited from being captured and traded. There are also many turtles listed in the Red List of Endangered Species of the World Conservation Union (IUCN). For example, the concave-shelled tortoise and the ground turtle are endangered species, the loggerhead turtle is a vulnerable species, and the hawksbill turtle is listed as a critically endangered species. There are 104 aquatic turtle species listed in the CITES Appendix that are protected by the Convention on International Trade in Endangered Species of Wild Fauna and Flora. Among the protected species promulgated by my country in 2020, there are 21 species of turtles and tortoises, of which tortoises, sea turtles, soft-shelled turtles and spotted softshell turtles are first-class protected animals, and 11 species such as flat-breasted turtles, three-lined box turtles, and mountain softshell turtles are second-class protected animals.

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In addition to strict protection, conducting artificial breeding research is also an effective way to protect endangered species. In accordance with the relevant provisions of the "Wildlife Protection Law of the People's Republic of China", the Ministry of Agriculture and Rural Affairs has issued two batches of "Lists of National Key Protected Aquatic Wildlife under Artificial Breeding", which include protected turtles such as the three-lined box turtle, yellow-throated turtle, flower turtle, black-necked turtle, Annam turtle, yellow-margined box turtle and black pond turtle.

turtle animal

An integral part of the ecosystem

Protecting endangered and rare species

It is an important task to maintain the stability of the ecosystem

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