Cretaceous Cold Case No. 2, Part 2: It’s a Trap?

This is part two of the second case in a series called “Cretaceous Cold Cases” in which the science of taphonomy, or prehistoric forensics, is explained through fascinating cases from the files of Terry “Bucky” Gates, a research scientist with a joint appointment at NC State and theNorth Carolina Museum of Natural Sciences。Part 1 is这里。

The 147-million-year-old Cleveland-Lloyd Dinosaur Quarry is truly a prehistoric cold case. Paleontologists believed that the evidence pointed to gluttony and miscalculation as the causes of death for 53 carnivorous dinosaurs.

我没有说服。在证据中有巨大的漏洞，以前的调查人员对异常大量的死食的重点并没有和我坐在一起。

考虑到这一点,我看了看Cleveland-Lloyd Dinosaur Quarry in a different way. Instead of addressing the elephant in the room – how did so many carnivorous dinosaurs get buried in this location? – I stepped back and asked a broader, dinosaur-sized question.

“What could have led to the death and burial of more than 75 dinosaurs at this location?”

The new investigation was open.

My first step in the investigation was to make a list of all possible ways that dinosaurs could have ended up at the quarry. I thought through all the ways the animals could have died at the site, including scenarios such as volcanic eruption, drought, or predator trap, and also scenarios where the dinosaurs died elsewhere and were brought to the site, as in a large flood.

Then I had to find forensic evidence. Taphonomists don’t bring dust for paleo-forensic investigations. We make dust. The only way to find forensic data in the fossil record is to dig it up. During the course of our two-year excavations and hundreds of hours back at the museum, I collected data on the position and condition of every bone we found. This included the size of the bone, direction the bone was pointing in the ground, depth it was buried, and whether there was evidence of carnivorous tooth marks. I also tried to determine whether the bone had lain on the ground surface for years before being buried, and observed the edges of the bones to see if they had been scuffed or rounded.

Patching together the stories of each individual bone and the geologic sequence through the bone layer revealed the history of the entire fossil assemblage.

最后，我能够扣除！这是迄今为止绘制的最令人兴奋的部分。在古生物学中，我们依靠简单的公理，“现在是过去的关键。”这意味着我们在史前时代期间，我们周围每天都会看到的自然过程也在非常相似。所以我比较了洪水的现代证据，杰林（一种觉得陷入泥土的奇特方式），干旱和火山喷发我们所看到的克利夫兰 - 劳埃德采石场，并成为一个很酷，有趣的新结论。

I believe that a pandemic drought caused the accumulation and death of around 75 dinosaurs in one spot during the Late Jurassic of central Utah.

这是现场：旱季开始，1.47亿年前，犹他州。植物散落在地面上，但唯一的大型森林靠近蜿蜒的河流，现在在流动中徘徊。穿过洪泛区，一个浇水洞是一定距离的唯一水源和少数植物吃恐龙，如Camarasaurus和Stegosauruslumber toward it. In modern droughts, some animals will find a watering hole and stay there until the dry season ends, which may have happened with these dinosaurs. Of course, the carnivores were not far behind.

When some of the herbivores succumbed to the prolonged drought the carnivores began feasting on their meat. The smell of rotting 100,000-pound dinosaurs is sure to attract its fair share of hungry diners. As such, more and more carnivores, especiallyAllosaurus.fragilis, arrived at the party. The sight of so many prowling predators – and their many rows of shiny, sharp teeth – in one place may have scared away other herbivores, which would explain why so few are preserved at the site.

One thing we know is that carnivores like meat, even meat of their own species. I found evidence that someAllosaurus.bones were eaten by predatory dinosaurs, and given how manyAllosaurus.were found at the site, my money is on the carnivores devouring one another once the herbivores expired.

Eventually, the drought ended and the floodwaters refilled the watering hole, covering dozens of dead dinosaurs.

一个新的问题，新数据和新的解释。这种冷箱是关闭的......现在。