November 22, 2010
Hot on the heels of a team of researchers who described Zhuchengceratops from the Cretaceous of China, paleontologists Yuong-Nam Lee, Michael J. Ryan and Yoshitsugu Kobayashi have just announced the discovery of another ceratopsian dinosaur—Koreaceratops hwaseongensis—from the 103-million-year-old rock of South Korea. It is the first dinosaur of its kind to be found in the country, though it shows some peculiar similarities to other dinosaurs found elsewhere.
Represented by a nearly complete tail, portions of the hips and partial hindlimbs, Koreaceratops was discovered on the west coast of the Korean peninsula in 2008 near Jeongok harbor. Not very much of it was left to compare to other dinosaurs, particularly since no elements of the skull were found, but the handful of distinctive characteristics in the hindlimbs and tail identified it as a ceratopsian dinosaur closely related to Archaeoceratops and Cerasinops.
The most prominent feature of Koreaceratops is its deep tail. Like Protoceratops, Montanoceratops and similar horned dinosaurs, Koreaceratops had a series of exceptionally long neural spines sticking up from its tail vertebrae which get progressively longer towards the end of the tail before becoming shorter near the tip. This would have given Koreaceratops a tall, deep tail which would have looked superficially like a paddle. Over the past century, several paleontologists have argued that ceratopsians with this tail shape may have been amphibious.
The authors of the new study approach the possibility that Koreaceratops was semi-aquatic tentatively. The paper’s abstract states that the tall neural spines of Koreaceratops, Montanaceratops and other ceratopsians may have evolved multiple times as a possibly adaptation to swimming, but in the body of the paper they state that the evidence that these dinosaurs were regular swimmers is equivocal.
I am doubtful that the deep tails of these dinosaurs can be taken as a good indicator of their swimming ability. As the authors of the new study document in the paper, the tail shapes of each of these deep-tailed ceratopsians varies significantly. Koreaceratops had a tail with taller and taller neural spines approaching the tip—making the end portion of the tail the deepest—while in Protoceratops the deepest portion is closer to the hips, being in the middle of the tail or just a bit closer to the rest of the body. If all of these dinosaurs had tails that independently evolved to allow them to propel themselves through the water, it might be expected that they would all have tails with the same shape, namely with the deepest part of the tail being near the tip as this would give them the most thrust. Instead, the different deep tail types may have been involved in display or species recognition, in which case we would expect for there to be variation in tail shape from one dinosaur to another.
Admittedly it is relatively easy to come up with hypotheses about tail function. What is more difficult is finding a way to test ideas about long-extinct organisms. In this case anatomy alone may not provide an unambiguous answer, but there may be a way to determine whether or not Koreaceratops and its kin were semi-aquatic. Paleontologists have regularly used levels of oxygen isotopes preserved in the teeth and bones of prehistoric animals to determine whether or not certain animals spent a great deal of time in the water. Earlier this year a different group of paleontologists used this technique to provide support for the idea that the predatory spinosaurs were semi-aquatic animals, and the same line of evidence could be applied in this long-running debate about ceratopsians. No single study will shut the case entirely, but the more lines of evidence we can draw upon to approach the question of swimming ceratopsians, the better.
Lee, Y., Ryan, M., & Kobayashi, Y. (2010). The first ceratopsian dinosaur from South Korea Naturwissenschaften DOI: 10.1007/s00114-010-0739-y
July 8, 2010
Fossil dinosaur tracks don’t often get the same popular attention that skeletons do. The impressions within the rock seem to pale in comparison to the beautiful organic architecture of the bones, but, while they might not be as aesthetically interesting to some, tracks are bits of behavior preserved for millions of years. They were made by living creatures, and by studying them carefully paleontologists can reconstruct the details of how these animals moved.
There are many dinosaur track sites scattered all over the world, but in a paper published in Palaeogeography, Palaeoclimatology, Palaeoecology, scientists Bo Seong Kim and Min Huh focus on just one small set of Cretaceous-age footprints preserved in South Korea. Called “trackway B”, this set of impressions was made by a theropod dinosaur while running—the footprints clearly show that it was increasing its stride length between each step as a sprinting creature would do. In order to better appreciate how this dinosaur was moving, though, Kim and Huh made numerous measurements of the tracks to estimate the size of the dinosaur, its speed and how quickly it accelerated as it began to run.
Using the size of the footprints to calculate size, the scientists estimated that the dinosaur would have been about three feet high at the hips—this was a relatively small theropod. It would have been pretty fast, though. The speed estimates obtained for the tracks suggest that the dinosaur was moving at about seven miles per hour and then accelerated to between nine and twenty miles per hour. It appears that the dinosaur was already trotting at the beginning of the trackway, but the latter portion of it shows a quick uptick in speed to full running.
Just what spurred this dinosaur’s turn of speed, though, is unknown. The authors state that it was probably running about as fast as it could, so obviously it was moving with some urgency. Perhaps the dinosaur was after a potential meal, or was in danger of becoming a meal itself. We will probably never know for sure, but, regardless of what happened, the footprints represent a snapshot into a dinosaur’s life.
Kim, B., & Huh, M. (2010). Analysis of the acceleration phase of a theropod dinosaur based on a Cretaceous trackway from Korea Palaeogeography, Palaeoclimatology, Palaeoecology, 293 (1-2), 1-8 DOI: 10.1016/j.palaeo.2010.04.020
October 13, 2009
Even though some of the largest dinosaurs get the most attention, dinosaurs actually came in a variety of sizes. This past week paleontologists announced two discoveries that emphasize just how large, and how small, some dinosaurs were.
From Plagne, France came the announcement of the largest dinosaur footprints yet discovered. Naturalists Marie-Hélène Marcaud and Patrice Landry found the tracks back in April, at which point paleontologists Jean-Michel Mazin and Pierre Hantzpergue from the Université Claude Bernard Lyon went out to have a look. They discovered that the 150-million-year-old tracks were made by enormous sauropod dinosaurs, the largest probably stretching over 85 feet and weighing more than 40 tons.
Contrast that with a find announced yesterday in the Korea Herald. The newspaper reported that a resident of one of South Korea’s southern provinces discovered one of the smallest dinosaur footprints ever found: the track of a theropod dinosaur measuring only half an inch long. According to Kim Gyeong-su of Chinju National University of Education, the track is about 100 million years old and is consistent with a previously-known track type called Minisauripus.
I wonder how many of the tiny theropods could have fit into just one track made by the enormous sauropod!