Cretaceous Cold Case No. 4: Graveyard Shift
This is the fourth post in a series called “Cretaceous Cold Cases” in which the science of taphonomy, or prehistoric forensics, is explained by fascinating cases from the files of Terry “Bucky” Gates, a research scientist with a joint appointment at NC State and the North Carolina Museum of Natural Sciences.
The graveyard shift in Madagascar doesn’t happen at night. Instead, paleontologists sweat all day in the heat of the sub-tropical island’s sun. It’s a hot place to dig for long-necked dinosaurs, huge voracious carnivorous dinosaurs, and birds with long tails and sickle claws that roamed the island 70 million years ago.
Since 1995, a team of paleontologists has been uncovering the huge dinosaur bonebeds, or graveyards, on Madagascar. Ray Rogers has led the paleo-forensic investigation of these remains. The skeletons are beautifully preserved, although some are scattered over a large area or are completely missing sections.
Careful examination of the bones revealed curious gouges and parallel lines on some specimens. Could these markings be clues to the dinosaurs’ demise? Ray needed to know. And so did I.
My name is Bucky Gates, and I’m a taphonomist.
Bones from several different animals found in the graveyards showed signs of damage, but most of the damaged bones came from Majungasaurus, the Cretaceous-king of the fourth largest island nation in the world. With lots of broad, sharp teeth and a gnarly face that only a mother could love, Majungasaurus ate other dinosaurs such as the long-necked herbivore Rapetosaurus.
The evidence at hand was the spacing of the teeth in the mouth of the perp, and the number of denticles on its teeth. Denticles are small bumps on the sharp edge of teeth that act just like the serrations on a steak knife. Ray and his team microscopically examined the teeth marks found on Majungasaurus and Repetosaurus bones, and found that the U-shaped furrows, parallel alignment, and in some cases the denticles scrapings indicated the marks were made by something hungry and well equipped.
Time for the suspect lineup. On Madagascar during this time period, there were only a few possible perpetrators: Majungasaurus, the kingpin of the Madagascar carnivores; Masiakasaurus, a much smaller relative of the kingpin with teeth that stuck straight out of the lower jaw; and finally, Mahajungasuchus and Trematochampsa, two species of large crocodiles.
At first glance, it seemed that Majungasaurus was innocent because most of the tooth marks were found on Majungasaurus bones. But after careful comparison, none of the other carnivores had teeth or serrations that matched the forensic evidence.
Could it be?
Yes, the teeth spacing matched perfectly. The serrations matched perfectly. Therefore, the only possible conclusion is that Majungasaurus was a cannibal!
Not often in paleontology can a specific species be pinned down as eating another. This is a very special case where the lower dinosaur biodiversity on Madagascar helped to catch a…killer? Scavenger? The fact is we don’t know if Majungasaurus killed another of its own species, or if it simply ate the remains after the victim had already perished. And if the latter scenario is true, then we still don’t know what killed the king.
In the next segment I will talk about my hunt for a 300 million-year-old serial killer.