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A “stocky dragon” from Transylvania

Ancestors of dinosaurs and other animals from the Haţeg Basin in Transylvania may have arrived from what was once a continent of Asiamerica by “island hopping,” suggests a fossil discovery published today. By Hans-Dieter Sues Islands are wonderful natural laboratories for the study of evolutionary change and for that reason have long attracted the attention...

Ancestors of dinosaurs and other animals from the Haţeg Basin in Transylvania may have arrived from what was once a continent of Asiamerica by “island hopping,” suggests a fossil discovery published today.

By Hans-Dieter Sues

Islands are wonderful natural laboratories for the study of evolutionary change and for that reason have long attracted the attention of biologists. Their peculiar ecological conditions often led to the evolution of species that greatly differ in body size and/or form from their closest relatives on the mainland.

Large animals often become smaller on islands (due to limited food resources) and small ones become larger (often due to the absence of predators). This phenomenon is known as the “island rule.”

One of the best-known examples from the fossil record are the pony-sized elephants that lived on Crete and other Mediterranean islands during the Pleistocene and Holocene.

Other striking examples include the ‘koala lemur’ Megaladapis from Madagascar, which attained a weight of up to 100 kg (220 pounds) and vanished only in the 16th century, and the ground-dwelling owl Ornimegalonyx from the Pleistocene of Cuba, which may have stood an impressive 1.1 m (3.6 feet) tall.

At the beginning of the 20th century, the Austro-Hungarian paleontologist Franz Baron Nopcsa reported dinosaur fossils from sedimentary rocks of latest Cretaceous age in the Haţeg Basin of Transylvania (which became part of Romania after World War I). His sister had discovered dinosaur bones on one of the family’s estates, which excited the young nobleman’s interest and led him to a distinguished career in paleontology. Additional collecting by Nopcsa and others led to the recovery of bones belonging to several new species of dinosaurs.

What is most intriguing about these fossils is the fact that they represent animals of much smaller body size than related species elsewhere. Based on this size difference, Nopcsa inferred that the Haţeg dinosaurs represented an island community. However, his work was largely ignored until there was a resurgence of interest in the Late Cretaceous dinosaurs from Transylvania in the late 1970s.

Evolutionary decrease in body size

Recent studies on the microscopic structure of the bones in the duck-billed dinosaur Telmatosaurus and the titanosaurian sauropod Magyarosaurus from the Haţeg Basin support Nopcsa’s hypothesis that both dinosaurs had undergone an evolutionary decrease in body size.

Since the 1970s, many new finds of vertebrate fossils have further demonstrated the peculiar nature of the biota from the Late Cretaceous of the Haţeg Basin. In the Proceedings of the National Academy of Sciences a team of Romanian and American paleontologists has just announced the most remarkable discovery to date–an unusual new predatory dinosaur.

During Late Cretaceous times (about 100 to 65 million years before present), a warm, shallow sea sprinkled with islands of various sizes covered much of present-day Europe. Motions of the African continental plate led to volcanic activity and formation of islands along the northern margin of the western portion of the Tethys Sea (which would later become the Mediterranean Sea).

The Haţeg Basin of Romania was located on an island in an archipelago that extended from the region now occupied by the European Alps eastward to present-day southwest Asia.

Closest dinosaurian relatives of birds

The new species of predatory dinosaur from Romania has been named Balaur bondoc. (Balaur is derived from an ancient Romanian word for ‘dragon’ and bondoc means ‘stocky.’) It belongs to the Dromaeosauridae, which include the (misnamed) “raptors” of the blockbuster movie Jurassic Park and are now considered the closest dinosaurian relatives of birds.

One of the specimens assigned to this new species preserves articulated bones of the limbs and girdles (Figure 1).


Figure 1. Reconstructed body silhouette of Balaur bondac with known bones shown.

Courtesy and copyright of M. Ellison (American Museum of Natural History).

The sturdily built skeleton of Balaur bondoc is unlike that of other known dromaeosaurs in a number of features.

The hand shows extensive fusion of bones in the wrist and hand. There are only two functional fingers, unlike the three-fingered grasping hand in related species.

The foot retains an enlarged, functional first toe, unlike the greatly reduced digit in most predatory dinosaurs. This toe is very similar in size and shape to the second one, which, as in other dromaeosaurs, carries a much enlarged, sickle-shaped claw that had a large arc of motion.

Each foot of Balaur sported a double set of these claws, which were probably used in seizing prey (Figure 2). The robust hind leg shows extensive fusion of bones in its shin and foot. Apparently Balaur could deliver powerful strikes with its deadly feet.


Figure 2. Left lower leg and foot of Balaur bondoc with two greatly enlarged claws (marked by white arrow heads).

Courtesy and copyright of M. Ellison (American Museum of Natural History).

Balaur is most closely related to the Late Cretaceous Velociraptor from Mongolia and China. This is an important finding because one of the unresolved issues concerning the Haţeg dinosaurs had concerned their origin: Did they represent ancient lineages that had only survived on an island or did at least some of the species have faunal connections with neighboring continents late into the Cretaceous?

The duck-billed dinosaur Telmatosaurus suggested connections to Asia. The discovery of Balaur now provides further support for this hypothesis.

The researchers argue that the peculiar skeleton of this predator represents an example of the “island effect.” The precursors of the dinosaurs and other animals from the Haţeg Basin may have arrived from Asiamerica (a vast ancient landmass that included what are now East Asia and western North America) by “island hopping,” especially during intervals of lower sea levels.

Hans-Dieter-Sues.jpgHans-Dieter (Hans) Sues is a vertebrate paleontologist based at the National Museum of Natural History in Washington, D.C. He is interested in the evolutionary history and paleobiology of vertebrates, especially dinosaurs and their relatives, and the history of ecosystems through time.

A former member of the National Geographic Committee for Research and Exploration, Hans has traveled widely in his quest for fossils and loves to share his passion for ancient life through lectures, writings, and blogging.

Blog entries by Hans-Dieter Sues >>

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