Here's a piece of evidence worthy of a Sherlock Holmes (or Scooby Doo) mystery: fossilized turtles found in Germany, at the Messel Pit Fossil Site between Darmstadt and Frankfurt.

The turtles are a form of pitted-shell (or carettochelyid) turtle, Allaeochelys crassesculpta, and what is unique about these particular fossils is the fact that they are preserved as mating pairs -- fossilized during the act of copulation.  As this scientific paper published last month in the biology journal of the Royal Society explains, this is the first such example of fossilized vertebrates preserved in the act of having sex.  As this BBC article explains, about nine such pairs have been discovered in that area over the years.

Obviously, this presents something of a head-scratcher: how did these turtles happen to end up as fossils in such a position?  Presumably, both members of the mating pair must have died at the same time, indicating the likelihood of some sort of catastrophe that befell them rapidly.

Actually, the presence of any fossils generally presents a problem for uniformitarian geology (geology that attempts to explain most phenomena using long periods of non-catastrophic causes that have not changed much over millions of years), as this previous blog post explains. Animals that die (even if not in the middle of copulation) do not simply settle to the forest floor or the ocean floor and become fossilized -- they usually decompose long before that.  The presence of massive numbers of fossilized animals and plants on our planet may be evidence of a catastrophic event or events that created conditions in a rapid manner to preserve them before they decomposed.

With the case of the fossilized copulating turtles, the authorities in the mystery story have to come up with a thesis that fits the evidence, just as in a Sherlock Holmes or Scooby Doo mystery (this previous post discussed the usefulness of this analogy).  In this case, the authorities have their theory:
it is unlikely that the turtles would mate in poisonous surface waters. Instead, the turtles initiated copulation in habitable surface waters, but perished when their skin absorbed poisons while sinking into toxic layers. The mating pairs from Messel are therefore more consistent with a stratified, volcanic maar lake with inhabitable surface waters and a deadly abyss. 
This explanation is plausible, especially as the phenomenon appears to be localized, and as the lead author of the paper says that there is evidence of such rapid death happening to some mating turtles in volcanic lakes of East Africa.  However, we again point out that those turtles dying in volcanic lakes today are probably not going to end up as fossils millions of years from now, so this conventional storyline still has some holes in it.

An alternative explanation, and one that would explain how these turtles ended up this way, is that a catastrophic flood event rapidly buried these mating turtles in tons of wet sediments, killing them instantly and leading to their preservation as fossils, as described by Dr. Walt Brown in his hydroplate theory and supported by extensive other corroborating pieces of evidence.

Note that if the proponents of the "toxic volcanic lake theory" can point to supporting evidence from contemporary African lakes, it would appear that supporters of the hydroplate explanation can point to even more extensive supporting evidence in the form of literally thousands of instances of one fish fossilized in the act of devouring another fish (see image below, from Fossil Butte National Monument in Wyoming).

The case of fish fossilized while eating other fish is a very strong parallel to these turtle fossils from Germany.  The fossils clearly seem to point to a sudden catastrophic mechanism.  Just to point out the obvious, if the larger fish died in the act of swallowing another fish alive, that second fish would probably extract itself and swim away.  Similarly, in the case of the turtles, if one turtle died during intercourse, the other would not be expected to wait around to become a fossil as well.  In the case of the fish, it is difficult to propose the theory that they somehow started their meal in shallow non-toxic waters and then died when they sank to more toxic depths, the way that conventional scientists are arguing in the case of the fossilized copulating turtles.

You decide: which explanation makes more sense?

Special thanks to my good friend Dan the Organic Farmer for alerting me to this turtle tale.