The Only Known Vertebrate Fossil In The Act Of Copulation

[BullStrong]

http://www.bbc.co.uk/news/science-environment-18495102

By Jonathan AmosScience correspondent, BBC News

The turtles were found in male-female pairs

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Turtles killed as they were having gender and then fossilised in position have been described by scientists.

The remains of the 47-million-year old animals were unearthed in the famous Messel Pit near Darmstadt, Germany.

They were found as male-female pairs. In two cases, the males even had their tails tucked under their partners' as would be expected from the coital position.

Details are carried in the Royal Society journal Biology Letters.

Researchers think the turtles had initiated gender in the surface waters of the lake that once existed on the site, and were then overcome as they sank through deeper layers made toxic by the release of volcanic gases.

The animals, still in embrace, were then buried in the lakebed sediments and locked away in geological time.

"We see this in some volcanic lakes in East African today," explained Dr Walter Joyce of the University of Tübingen.

"Every few hundred years, these lakes can have a sudden outburst of carbon dioxide, like the opening of a champagne bottle, and it will poison everything around them."

The turtles described in Biology Letters are of the extinct speciesAllaeochelys crassesculpta.

They are about 20cm in length; the females are slightly bigger than the males.

Their nearest living relatives are probably the pig-nosed turtle (Carettochelys insculpta), a much bigger species that swims in waters around Australia and Papua New Guinea.

A. crassesculpta is just one of thousands of exquisitely preserved fossil creatures pulled from Messel Pit, which has Unesco World Heritage status because of its palaeontological significance.

Nine pairs of turtles have been unearthed at the site over the past 30 years.

In most of the couples, the individuals were discovered in contact with each other. For the pairs that were not, the individuals were no more than 30cm apart.

"People had long speculated they might have died while mating, but that's quite different from actually showing it," said Dr Joyce.

"We've demonstrated quite clearly that each pair is a male and a female, and not, for example, just two males that might have died in combat.

"This fact combined with the observation that their back ends are always orientated toward one another, and the two pairs with tails in the position of mating - that's a smoking gun in our view."

It is said to be the only example in the fossil record of vertebrates being preserved in the act of having gender.

For invertebrates, there are numerous examples in the scientific literature of copulating insects being caught in amber, or fossilised tree resin.

The closest living relative is probably the distinctive pig-nosed turtle

Edited June 1, 2013 by BullStrong

[Boesse]

This is somewhat old news, it came out a year ago...

[BullStrong]

Yes it is, i searched the forum thinking it was already posted but didn't find it, If its been posted already and I missed it, sorry for the re-post!

[Scylla]

Here it is:

http://www.thefossilforum.com/index.php?/topic/30128-mating-turtles-found/?hl=turtle#entry332562

[painshill]

interruptus indeed.

In Richard Lund’s 1990 review of the chondrichthytes (sharks, rays etc) from the Bear Gulch limestone in Montana, he reported on another possible example found a few years earlier.

The deposits were roughly 320 million years old and – like the Messel site in Germany – they are lagerstätten. Sharks which are otherwise known only from their teeth have been found in remarkable states of preservation.

Lund’s review includes details of a male/female pair of six-inch long Falcatus falcatus sharks, the female of which has her jaws clamped around the male’s head ornament – a horn-like spike that curves up from behind the eyes. So, at death, the female was on top with her belly along the male’s back.

Here’s a reconstruction illustration from Lund’s review:

That’s the wrong position for copulation – the male’s genitalia (which protrude along the pelvic fin area) are not even close to the female’s but the nature of the association between the two fossils is intriguing. All the more so since a pair of Damocles serratus sharks with similar morphology have also been found with the same juxtaposition and orientation.

So, not copulation, but certainly highly suggestive of a pre-copulation mating ritual.

[Auspex]

It is remarkable enough that the state of preservation of these sharks is good enough to differentiate the sexes!

[Coco]

Hi,

I didn't understand if these sharks were enough well preserved to recognize the sexes, or if the sexes were guessed from teeth (to certain selachians, males and females have different teeth).

Coco

[painshill]

Hi,

I didn't understand if these sharks were enough well preserved to recognize the sexes, or if the sexes were guessed from teeth (to certain selachians, males and females have different teeth).

Coco

The genders were determined from the presence/absence of the head ornament. Males have a spike, but females do not.

[Auspex]

The genders were determined from the presence/absence of the head ornament. Males have a spike, but females do not.

I did not know that!

[Coco]

Hi,

Thanks Painshill. I just known that about chimaera, not about sharks !

Coco

[painshill]

Hi,

Thanks Painshill. I just known that about chimaera, not about sharks !

Coco

Not all sharks of course. Here's a well-preserved male Falcatus from the Montana deposits that shows the spine very clearly:

[pic by H. Zell - Creative Commons license]

In some cases the gender can also be determined from the presence of valvae (claspers) behind the pelvic fin, which are only present in males.

[Coco]

Who ! Thanks Painshill for this pic ! Marvelous !

Coco