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A drawing showing the parts of the skeleton recovered for Balaur, with photos of the hands and feet. From Csiki et al, 2010.

Thanks to their prominent appearances in museum displays and the Jurassic Park film franchise, many people are very familiar with what dromaeosaurid dinosaurs looked like. Relatively small and lightly-built, these predators had long, grasping hands and a hyperextendable second toe on each foot tipped in a large sickle-shaped claw. But a newly-discovered “raptor” from the Late Cretaceous rock of Transylvania has an altered body plan that sets it apart from its evolutionary cousins. It is one of the strangest raptors ever discovered.

Announced by a team of paleontologists led by Zoltán Csikia in this week’s issue of PNAS, the dinosaur Balaur bondoc comes from Romanian geological deposits representing an ancient island which was home to a variety of dwarfed herbivorous dinosaurs. The herbivores are relatively easy to find at these sites, but bones from predatory dinosaurs are much rarer, and the partial skeleton used to identify Balaur is the most complete set of dromaeosaurid remains yet found from the area. This alone makes it an important discovery—a first, detailed look at one of the predators that lived on the prehistoric island—but what really makes Balaur unique are its hands and feet.

Thanks to the discovery of numerous other dromaeosaurids, paleontologists have recognized that the standard set of predatory equipment for raptors includes three-fingered hands and a foot with two toes touching the ground and one (the second toe) held off the ground to support a large, recurved claw. What makes Balaur different is that, while it only had two fingers on each hand, its first toe was rotated forward and supported a second sickle claw. This was not just an aberrant, polydactyl individual; the additional hyperextendable toe was a highly modified version of the standard first toe seen in other raptors.

As strange as it is, though, Balaur does not appear to occupy some weird new branch of raptor dinosaurs. Instead, Csikia and colleagues found that it was most closely related to the well-known Velociraptor, meaning that the lineage Balaur belonged to became highly modified after the time of its split with the common ancestor of Velociraptor. Why it is so different from its relatives is still unknown. The authors of the new paper state that the “island effect,” which caused the herbivorous dinosaurs to become dwarfed, may account for the strange anatomy of Balaur, but exactly what this means is left unclear. Nevertheless, Transylvania was clearly a strange place during the Late Cretaceous: an island where strange theropods such as Balaur stalked the dwarfed sauropods and hadrosaurus of the day.

References:

Csiki, Z., Vremir, M., Brusatte, S., & Norell, M. (2010). From the Cover: An aberrant island-dwelling theropod dinosaur from the Late Cretaceous of Romania Proceedings of the National Academy of Sciences, 107 (35), 15357-15361 DOI: 10.1073/pnas.1006970107

The partial dinosaur hip from Dinosaur Cove as seen from the right (B) and the front (C). It is shown compared to the hip of a known tyrannosaur (D). From Science.

Last March a team of paleontologists led by Roger Benson described what appeared to be a partial hip of a tyrannosauroid dinosaur from Australia—the first-ever trace of this group of dinosaurs on the southern continent. Now, in a comment and reply printed in last week’s Science, Matthew Herne, Jay Nair and Steven Salisbury argue that the case for a tyrant from down under isn’t as strong as Benson proposed.

The argument hinges upon parts of the front, downward-oriented part of the hip known as the pubis. Tyrannosaurs, particularly some of the last ones to have evolved, are well-known for having distinctive, robust pubic bones, and the specimens recovered from the vicinity of Victoria, Australia certainly look like they could belong to a tyrannosaur. Yet, according to Herne and colleagues, the anatomical details initially thought to diagnose the bones as belonging to a tyrannosaur are seen among other theropods, too. Precisely what kind of theropod the bones represent is difficult to determine, but Herne and his co-authors propose that it came from one of the theropod dinosaur varieties already known from Australia (such as other types of coelurosaur and the carcharodontosaurians).

As would be expected, Benson and the other authors of the original paper disagree. In a reply published along with the new commentary, the scientists maintain that a peculiar feature of the hip—known as the pubic tubercle—is most similar to the same feature in tyrannosaurs to the exclusion of similar theropods. Even though this feature is broken, the authors behind the original description argue that the orientation of the missing portion can still be determined, and if it were complete it would show a condition similar to that of the tyrannosauroid dinosaurs. Furthermore, discoveries made during the past several decades have shown that dinosaur diversity cannot be simply divided into northern (Laurasian) and southern (Gondwanan) groups. The closest relative of the Australian theropod Australoventaor, for example, is Fukuiraptor from Japan, indicating that some groups of dinosaurs crossed what were once thought to be geographic barriers.

Two groups of researchers looked at the same fossils and came to very different conclusions. One group interpreted the hip bones as those of the first tyrannosaur known from the southern hemisphere, while the other argues that there is nothing which explicitly identifies it as such. For the moment, though, the identification of the bones could go either way. More fossils will be needed to know for sure, and I anxiously await the announcement of further remains from this contested Australian dinosaur.

For more on this discovery, see this in-depth summary at The Bite Stuff.

References:

Herne, M., Nair, J., & Salisbury, S. (2010). Comment on “A Southern Tyrant Reptile” Science, 329 (5995), 1013-1013 DOI: 10.1126/science.1190100

Benson, R., Barrett, P., Rich, T., Vickers-Rich, P., Pickering, D., & Holland, T. (2010). Response to Comment on “A Southern Tyrant Reptile” Science, 329 (5995), 1013-1013 DOI: 10.1126/science.1190195

The skeleton of Albertosaurus on display at the Royal Tyrrell Museum. Image from Wikipedia.

Every year scores of paleontologists head out to the field in search of dinosaur fossils, but sometimes the remains of the charismatic creatures are hiding right underfoot. As reported in various news outlets earlier this week, sewer construction workers Aaron Krywiak and Ryley Paul discovered dinosaur bones while working 120 feet under the city of Edmonton in Alberta, Canada. The fossils were from at least two well-known dinosaurs that lived about 75 million years ago, near the end of the Cretaceous: the tyrannosaur Albertosaurus and the hadrosaur Edmontosaurus. Teeth, vertebrae, and ribs are among the bones discovered by the duo, and city workers are going to cooperate with paleontologists from the Royal Tyrrell Museum and the University of Alberta to make sure future discoveries in the tunnel are carefully collected while diminishing construction delays.

A diagram showing how rain could have triggered debris flows which preserved some of the Early Cretaceous fossils on the Isle of Wight. From Sweetman and Insole, 2010.

When I think of dinosaur bones, the rocky and shrub-flecked expanses of western North America immediately come to mind, but it should not be forgotten that some of the first dinosaurs recognized by science were discovered across the Atlantic in England. Paleontologists have been searching for dinosaurs there longer than anywhere else, and among the localities scientists keep returning to are the Early Cretaceous strata on the Isle of Wight. In fact, paleontologists Steven Sweetman and Allan Insole have recently published a new study in Palaeogeography, Palaeoclimatology, Palaeoecology about what the island was like during the time of the dinosaurs, and it also identifies the unusual mechanism by which the remains of the dinosaurs were trapped in stone.

Part of a larger geologic unit called the Wealden Supergroup, the Wessex Formation contains records of an ancient river valley from a time when the Isle of Wight was a bit further south and dinosaurs indicative of the Jurassic were giving way to groups that became prominent during the Cretaceous. At this time—approximately 130 million years ago—the area experienced a warmer, seasonal climate with both wet and dry seasons, and much of this is known from geologic layers created along the edges of an ancient, winding river. About 4 percent of these deposits consist of plant debris (with vertebrate bones in the same beds) which were thought to have been laid down by regular floods, but in their new study Sweetman and Insole propose a different scenario.

Contrary to previous hypotheses that the area was subject to frequent, seasonal flooding, Sweetman and Insole took the content and pattern of the plant debris deposits to indicate that the area was subject to relatively rare depositional events which moved plant material and animal remains a short distance before settling. In fact, the details of each plant bed appear to indicate that the plant debris was not sloshed about in a large quantity of water, but instead was transported in what is known as a debris flow—a damp slurry of moving plant debris and other organic matter. In the scenario proposed by the authors, forest fires may have removed trees and low-lying plants that would have trapped water and stabilized the soil on hillsides. When heavy rain fell on these areas, logs, plants, and soil material would have spilled down the hill in a wet sort of landslide, picking up dinosaur carcasses and other objects before settling near the riverbank.

While the fossilized remains within the debris beds are a bit messy, by sampling through them paleontologists have been able to pick out a pretty good representation of what kinds of animals lived during the time. As indicated by scraps of plants, the vegetation of the time was a mix of the ancient and modern, with cycads and gingkoes existing alongside conifers and flowering plants. Altogether, the plant community appears to represent a savanna-like environment in which only the occasional stand of conifer trees stood up among large open areas of lower vegetation.

The riverside-savanna habitat the authors reconstruct for the area was apparently very productive, for, in addition to invertebrate remains, the bones of lizards, turtles, crocodiles, small mammals, pterosaurs and numerous kinds of dinosaurs have been found within the debris beds. Ankylosaurs, sauropods, theropods and representatives of other dinosaur groups have been found here, leading the authors to conclude that—at least during times when plants were abundant—the floodplain area was able to support a diverse array of dinosaurs. (It is worth noting, however, that dinosaurs have been found in this area outside of debris beds, meaning that different skeletons became preserved by different means.) When the debris flows came down the hill, they carried the bones from whatever dinosaur carcasses were already present on the hillside, thus creating a representative mix of the animals which modern paleontologists can use to measure the biodiversity of a long-lost habitat.

References:

Sweetman, S., & Insole, A. (2010). The plant debris beds of the Early Cretaceous (Barremian) Wessex Formation of the Isle of Wight, southern England: their genesis and palaeontological significance Palaeogeography, Palaeoclimatology, Palaeoecology, 292 (3-4), 409-424 DOI: 10.1016/j.palaeo.2010.03.055

Ah, The Crater Lake Monster, a film that repeatedly made me wonder, “why the heck am I still watching this movie?”

Like the last Dinosaur Drive-In film featured here, Crater Lake Monster contains no actual dinosaurs (no matter how many times the scientists in the film call it one). Instead our monstrous star is a big, hungry plesiosaur hatched out of an egg kept in “suspended animation” at the bottom of a lake until a meteorite strike turns the lake bottom into an incubator. It’s not the most original premise, but not a terrible place to start, either, and the stop-motion special effects of David Allen are pretty good for their time. Too bad the filmmakers had no idea what to do with their story.

The film opens with a trio of scientists who have discovered a cave painting—said to be thousands of years old but looking like it was made with a Sharpie just yesterday—depicting Native Americans attacking a plesiosaur. The scientists have to scramble out of the cave as the meteorite strikes the lake, and they soon forget their first discovery to investigate the impact. Pretty standard monster movie stuff, but the movie jumps the track when we meet our unexpected protagonists, a pair of local ne’er do-wells named Arnie and Mitch.

Arnie and Mitch are meant to be the film’s comic relief. They are not the least bit funny. They haggle, squabble and complain for an inordinate amount of time without moving the plot forward, outside perhaps of giving people an opportunity to fall prey to the lake’s plesiosaur by renting them boats. After finding one of their rented boats full of blood and a snooty couple in shock after a run-in with the monster, Arnie and Mitch begin to suspect something might be up, though they never see the monster themselves despite working around the lake, scuffling in the lake and otherwise acting like oblivious potential prey items. Perhaps the odd day-night cycle is responsible for their weird behavior. Throughout the movie characters keep saying things like, “look at all the stars,” in the middle of the day; the director apparently tries to convince his audience that it’s dark out by having characters repeatedly comment on it being nighttime, all evidence to the contrary.

In any case, the monster continues to select morsels from the lakeside buffet—from cattle to fugitive liquor store robbers—before running into the town’s sheriff. Everything comes together, but when the local law enforcement brings up the problem to the scientists we met at the beginning of the film he receives little sympathy. The researchers basically yell “SCIENCE!” at the sheriff and decide that it would be wiser to trap the monster in a nearby bay for study rather than destroy it outright. A town meeting—filled with people apparently given $5 by the director to be in the movie and giving him his money’s worth—is called to resolve the issue, but it doesn’t get very far before the monster starts tossing around hay bales in a nearby work yard. It’s the last straw for the sheriff, who powers up a flimsy bulldozer that looks capable of giving the monster a very dull shave. Before he can dispatch the monster, though, the plesiosaur kills Arnie, leaving a sullen Mitch alone as the end credits begin to roll. As the yellow list began to flash over the screen, my wife said it best when she said, “wow. Nothing happened in that movie.”