Transylvanian Dinosaurs

by David B Weishampel

  Here we have presented a sketch of what the environmental setting of Transylvania might have been like some 70 million years ago. Some of the information is readily available from the rock and fossil record, but other aspects remain highly speculative. On this basis, do we now think that the paleogeography, paleoenvironment, and biota is well understood? Not yet we don’t.

  HAŢEG ISLAND?

  As we have noted, Nopcsa and several recent paleogeographers of the Mesozoic of Europe depicted western Romania as a reasonably large island, often within an archipelago whose activity is due to movements of small tectonic plates associated with the conjoined motion of Africa and Apulia. However, things are not necessarily so straightforward; other studies indicate that this habitat reconstruction is far too simple.54 We cannot overemphasize how extremely difficult it is to reconstruct now-obliterated habitats, especially those terrestrial ephemera created and disposed of by tectonic dynamism during the evolution of the Cretaceous Neotethyan Ocean. Despite his strong belief that the Haţeg area was part of an island, Nopcsa also recognized that there was a paucity of geologic evidence to suggest that this was true—no trace could be found of beach or other tidally influenced deposits indicating the periphery of such an island. Abel also criticized Nopcsa’s reconstruction of the Haţeg region as an island, questioning whether the area that supported the fauna was actually small enough to be considered an island or, instead, was sufficiently large in this regard to be considered a mainland.

  Just how do we identify islands in deep time? Unlike the present or recent past, where islands can be quite easily seen or are uncontroversial in their reconstruction, we need to be more careful with our prehistoric interpretations. Nopcsa’s strategy was to enlist both geology and biology, just about the only observations we still have available to us. From geology, we could look for sedimentological evidence of beaches or shorelines (which Nopcsa—and others since—have been unable to find). We could also look to the depositional context, in particular the thickness of the stack of terrestrial sediments, for an estimate of the size of the rapidly subsiding depositional basin. Given that the thicknesses of the terrestrial rocks observed in the Haţeg Basin and the Transylvanian Depression range from 2,500 to 10,000 m, this large accumulation of sediment means that the Haţeg region cannot be reconstructed as a small island, and it needed to have been a sufficiently large emergent area to be able to accommodate the tectonic activities that clearly occurred there. As we have seen in the earlier portions of this chapter, another source of data comes from paleogeographic reconstructions. Current paleogeo-graphic maps indicate a sizeable emergent area in this northern Peri-Tethyan realm, corresponding to the relatively small Haţeg Basin and much larger Transylvanian Depression. However, from what is now eastern Iran to Italy, the entire area was a huge swath of active mountain building (Plate VI).55 It is therefore difficult (if not impossible) to assess, amid all of this flux, many of the geographic details necessary to have made Transylvania a sufficiently sizeable and remote island.

  Fortunately, the best indicators of islands seem to be biological.56 The nature of their isolation from more continental faunas will produce different effects on island faunas. First, it is highly likely that island faunas will be less diverse than those on the nearby mainlands from which they colonized. Second, these faunas are very likely to be unbalanced, with major clades known from the mainlands absent from the islands. Third, depending on how long ago the islands were colonized, their faunas may resemble the more primitive nature of earlier faunas elsewhere. Fourth, for those taxa present on islands, there is probably a high degree of endemism. Finally, for the individuals living on islands, changes in body size are common.

  The issue of body size will be considered in some detail in chapter 5. Here, we will explore diversity, balance, primitiveness, and endemism in Transylvania, based on information about the membership of other faunas. We begin by comparing the Transylvanian fauna with other assemblages from Europe (figure 4.8). These include several sites in Sweden, England, Bulgaria, and Czechia; numerous localities in southern France, Spain, and Portugal; the assemblage from Muthmannsdorf in Austria; several nearshore marine sites around Maastricht in the Netherlands and adjacent parts of Belgium; a poorly known assemblage from Crimea in Ukraine; and new finds made in the late 1990s and early 2000s from Italy, Germany, Slovenia, and Hungary.57

  Paleontologists working at sites in southern France have recovered some of the most important terrestrial and nearshore marine vertebrate faunas from the Late Cretaceous of Europe.58 From Provence in the east to the northern foothills of the Pyrenees in the west, a wealth of dinosaurs, turtles, crocodilians, pterosaurs, bony fish, frogs, lizards, and mammals have been collected since the earliest discoveries in the 1700s.59 There are theropods from southern France, quite similar to the dinosaurs of the Transylvanian fauna. Like their Transylvanian relatives, most of these French specimens are poorly understood as yet. They include small forms, as well as the 7–10 m long Tarascosaurus and some tantalizing remains of a large bird (neither of which is yet known from Transylvania). A titanosaurian sauropod is present—Ampelosaurus—as are the ornithopods Rhabdodon, some newly discovered hadrosaurid material referred to Pararhabdodon (see below), and the nodosaurid Struthiosaurus. There are also plenty of turtles, fish, and crocodilians, gigantic pterosaurs, and eggs displaying a megaloolithid architecture.60

  Figure 4.8. A map of modern Europe, indicating known dinosaur-bearing localities from the Late Cretaceous. Scale = 600 km

  Numerous terrestrial faunas have also been found across the Iberian Peninsula. Those from Portugal are less well known, but they include, among the dinosaurs, a variety of small theropods, titanosaurian sauropods, nodosaurids, and ornithopods, as well as crocodilians, turtles, mammals, amphibians, and fish.61 Spanish localities have yielded a variety of thus-far poorly understood small theropods, titanosaurian sauropods (including one named Lirainosaurus), the nodosaurid Struthiosaurus, at least two kinds of ornithopods (Rhabdodon and Pararhabdodon), dinosaur eggs, pterosaurs, and a rich array of crocodilians, lizards, snakes, turtles, placental mammals, amphibians, bony fish, and sharks.62

  We have been introduced already to the Gosau fauna of Muthmannsdorf, Austria (chapter 2).63 The dinosaurs from this area consist of indeterminate theropods, an indeterminate rhabdodontid (formerly known as Mochlodon suessi),64 and the nodosaurid Struthiosaurus, while the rest of the fauna includes pterosaurs, crocodilians, a choristoderan (a small crocodilianlike fish-eater), lizards, and turtles.

  Nearshore marine deposits from the Maastricht region of the southernmost Netherlands and adjacent Belgium have produced a rich marine fauna, but very few dinosaurs thus far.65 A hadrosaurid known as Orthomerus dolloi and a theropod called Betasuchus bredai are known only from isolated and often fragmentary bones and teeth. These remains may represent cast-off body parts from bloated carcasses that drifted out to sea, for otherwise the vertebrate fauna consists of marine crocodilians, plesiosaurs, mosasaurs, turtles, bony fish, and sharks.

  Of the few remaining European faunas, the earliest known, described in 1945 by A. N. Riabinin from St. Petersburg, is from Crimea, the portion of Ukraine projecting into the Black Sea.66 Several postcranial skeletal elements belong to a hadrosaurid (originally called Orthomerus weberi, but this is probably not diagnostic). More recently, Peter Wellnhofer, a Bavarian paleontologist and one of the world’s leading specialists on Pterosauria, described a tantalizing, yet frustrating hadrosaurid femur from Maastrichtian marine limestones in Bavaria, Germany.67 At the opposite end of the scale of preservation, some excellent hadrosaurid material, including most of the skeleton and skull, occurs in Santonian deposits in northeastern Italy; it has been named Tethyshadros insularis.68 Finally, discoveries made over the past ten years in several areas in eastern and northern Europe—Kozina, Slovenia; Iharkút, Hungary; Labirinta Cave, Bulgaria; Mezholezy, Czechia; and the Belgorod and Volgorod regions of Russia—have disclosed additional dinosaur records from the Late Cr
etaceous. Thus far the dinosaur fauna from Slovenia, which is roughly contemporary with those of southern France, includes hadrosaurids and other ornithopods, small theropods, and two different crocodilians,69 while that from Hungary, dating from as early as late Santonian, indicates the presence of a neoceratopsian (Ajkaceratops kozmai), a nodosaurid ankylosaur (Hungarosaurus tormai), a rhabdodontid ornithopod, theropods (including an enantiornithine bird), an azhdarchid pterosaur (Bakonydraco galaczi), several kinds of crocodilians (including Iharkutosuchus makadi), turtles, amphibians, and fish.70 The Bulgarian occurrence is a disarticulated, incomplete hadrosauroid hind limb and a caudal vertebra that come from Labirinta Cave, southwest of the town of Cherven Bryag, in the northwestern part of the country.71 From Czechia comes a fragmentary yet tantalizing medium-sized femur that is thought to come from an ornithopod dinosaur. It was collected from shallow marine sediments (late Cenomanian in age) near the village of Mezholezy, between the towns of Kutná Hora and Čáslav. Currently, the Russian material from Belgorod consists of a tooth and a vertebra of what appears to be a close hadrosaurid relative, perhaps similar to Telmatosaurus, but of Albian–Cenomanian age.72 Finally, the Volgorod locality, Maastrichtian in age, has yielded two dinosaurs (an indeterminate hesperornithid and a basal theropod) and a few turtles.73

  How do these European faunas compare with each other and with others globally, in terms of diversity, balance, primitiveness, and endemism? It can be argued that the Transylvanian fauna is not much different from those elsewhere in Europe at the end of the Late Cretaceous—it has approximately the same within-clade diversity of creatures as France, Spain, or Austria: one or two ornithopods, a titanosaur or two, small and rare theropods, maybe a nodosaurid, pterosaurs, eusuchian crocodylomorphs, lizards, and amphibians. From this quick census, we would be hard-pressed to see many differences in diversity among the European regions.

  In this way, the European faunas appear to be reasonably ecologically balanced when compared with one another; that is, the makeup of the trophic organization of each region is roughly equivalent. For example, there are a variety of primary consumers in each fauna. Which group is at the top of the food chain (small theropods, pterosaurs, or eusuchian crocodilians) is somewhat questionable, but all are well represented from region to region. None of these faunas seems out of place with the others in terms of relative primitiveness. For all of these reasons, none of the European faunas appear to be loaded with endemics.

  That said, we’ve been looking at the wrong level for our comparisons. Major clades are expected to be widely distributed, on mainlands and on islands. When looked at from a species-level perspective, however, the pattern of similarity across the region changes. Telmatosaurus transsylvanicus is known only from Romania, while Pararhabdodon isonensis comes just from Spain and France. Ampelosaurus atacis has been found only in France, while Magyarosaurus dacus hails solely from Romania. The three species of the nodosaurid Struthiosaurus (S. austriacus, S. transylvanicus, and S. languedocensis) are each found in different parts of Europe. At these lower taxonomic levels, each European fauna is completely endemic to its particular region.

  Global comparisons of diversity, balance, and primitiveness are perhaps the most telling. At the global level, mainland faunas often have twice or three times (and more) the within-clade species diversity that is found in the different regions of Europe.74 Then there’s the issue of faunal balance, in particular regarding the top predator. If the European faunas of the Late Cretaceous differ in terms of the makeup at the top of the food chain, then they are not just microcosms of continental conditions elsewhere in the world. When compared globally, the most obvious difference between these European assemblages and those elsewhere in the world is who is represented in this top rank. The absence of a large theropod in Transylvania and in the other European faunas differs from the more continental situation during the Late Cretaceous. In western North America, we have Albertosaurus, Daspletosaurus, and Tyrannosaurus; central and eastern Asia has its Tarbosaurus and Alectrosaurus; and in South America there are Abelisaurus and Giganotosaurus.75 The lack of a large theropod in the European assemblages could be an artifact of collecting; none of the European localities can match the availability of fossils in the badlands and deserts of these other, larger regions. Nevertheless, if this lack is not an artifact, then the European faunas do depart from the more continental conditions of North and South America and Asia, making them unbalanced, at least in terms of who the top predator was. Further faunal absences from Europe consist of a host of major theropod groups, including tyrannosauroids, ornithomimosaurs, oviraptorosaurs, and therizinosauroideans. Another factor in this imbalance is the absence of diplodocoidean sauropods, ankylosaurids, pachycephalosaurs, and ceratopsians in Transylvania. Without many of these taxa, the European faunas tend to look rather primitive, more closely resembling those from the Early rather than the Late Cretaceous.

  INSULARITY IS IT

  The Transylvanian region seems to have been an island or, at the least, it behaves like one biologically. Even so, its areal extent is nearly unconstrained. It assuredly was large enough to form basins with very thick terrestrial depositions. It was also big enough to support numerous interacting tetrapod species. Could it have been large enough or close enough to contemporary mainlands to operate as an outpost, part of a tectonically active region where sizeable terrestrial habitats were contiguous with continental landmasses, but on an off-and-on basis?76 At the moment, it’s difficult to say. And maybe it’s not really relevant to determine whether the Transylvanian region was an island or an outpost. Perhaps what is most important here is the degree of insularity or isolation of the Transylvanian region and its fauna from those elsewhere in the world.

  Insularity need not be limited just to those landforms we call islands. Rather, it is used as a qualitative measure of isolation in present-day ecosystems. MacArthur and Wilson stated this in their opus on theoretical ecology and island biogeography:

  Insularity is moreover a universal feature of biogeography. Many of the principles graphically displayed in the Galápagos Islands and other remote archipelagos apply in lesser or greater degree to all natural habitats. Consider, for example, the insular nature of streams, caves, gallery forest, tide pools, taiga as it breaks up into tundra, and tundra as it breaks up into taiga.77

  In the case of our Transylvanian investigation, what matters is the insularity of the region, rather than the name of the landform we give to where it existed. Islands surrounded by water, remote lakes surrounded by land, clumps of woodland in a prairie, oases in the desert, mountain peaks, geologically ephemeral outposts in a tectonically active assemblage of microcontinental plates—all are characterized by being isolated from each other by a formidable barrier.78 However we reconstruct the paleogeography of Transylvania, it was certainly an insular place, by virtue of tectonics, geography, and ecology. The Transylvanian dinosaurs made their living on the edge, thanks to their insularity from the much larger continental faunas of Africa, Asia, and North America. Now it is a matter of understanding how and when this remarkable fauna may have arisen. To do so, we will take up the issues of phylogeny, heterochrony, and historical biogeography in chapters 6, 7, and 8.

  CHAPTER 5

  Little Giants and Big Dwarfs

  The earliest recognition of fossil bones, whether they were dinosaurian, mammalian, or some other vertebrate, cannot be recounted, but it is clear that they were given serious attention at least since antiquity. Seized on as being the remains of giants, so began the link between fossils and what might be called gigantology, a fascination with large size that continues to this day.1

  It was the bones of large fossil mammals, especially of extinct elephants, that originally attracted attention. Adrienne Mayor, in her tour de force treatment of the meaning of fossils in antiquity, noted many instances of massive bones discovered in such places as the islands of Sicily and Capri that were thought to be the remains of a race of giants.2

  Discove
ries and interpretations such as these continued to be made throughout the Middle Ages and the Renaissance—indeed, up until the end of the seventeenth century—whereby large fossil bones were generally thought to be the remains of human giants, dragons, or mythical monsters hearkening back to Greek mythology. In the skull of a Pleistocene dwarf elephant discovered in a Sicilian cave near Trapani in the fourteenth century, Giovanni Boccaccio (1313–1375), author of the Decameron, saw the face of the cyclops Polyphemus.3

  As Christianity took hold across Europe, scripture (“There were giants in the earth in those days,” Genesis 6:4) and the existence of ancient behemoths became closely tied. Consequently, the practice of attributing fossil bones to giants—often as saints and other biblical personages—led to these remains being kept in churches, especially in Europe. Other interpretations fashionable at that time included ascribing animal fossils to real people. Thus, according to legend, the remains of Theutobochus (King of the Teutons, Cimbri, and Ambrones) were recovered at Lang-don, France, in 1613. The giant Theutobochus was the basis for considerable controversy, in which opposing physicians and surgeons attacked each other over the authenticity and determination of these remains. In the end, these bones proved to be those of a Miocene elephant called Deinotherium giganteum.4