Note: See Brochu 1997, 1999; Buscalioni et al. 2001; Delfino et al. 2005; Pol et al. 2009.
These discoveries suggest that there is greater ecological diversity in Transylvanian taxa on the line toward living crocodilians than had been previously recognized.28 We suspect that Allodaposuchus, the best known among them, was probably an opportunistic, highly efficient predator, preferring to hunt and feed mainly at night, as is true in present-day crocodilian forms.29 These prehistoric creatures may have tracked their next meal, overpowering and dismembering the body before swallowing chunks of the carcass in single gulps. The ability of crocodilians to eat almost any animal they can overpower or drag underwater and drown has contributed to their success as predators.
The crocodilian habit of basking during daylight hours has led to the popular misconception that these animals are idle predators with limited social acumen. However, present-day crocodilians are known to engage in complex social behavior, including gregariousness, visual and vocal display, territoriality, and courtship behavior. Mothers build and guard nests, and they aid newborns in their struggle to leave their eggs. In addition, parental care extends well into the lives of these hatchlings. Whether a similar behavioral repertoire was present in any of the Transylvanian crocodilians is, unfortunately, still unknown.
As we have noted, the role of the top dinosaurian predator from the Transylvanian assemblages may have been occupied either by small, agile theropods or perhaps by the enormous pterosaur Hatzegopteryx. Could it be that Allodaposuchus also shared in this predatory biological role? Nopcsa, for one, regarded this ecological status as a distinct possibility. He even suggested that the fragmented, disarticulated dinosaurian remains in places like Sânpetru represented the ancient feeding grounds of Allodaposuchus.30 While we’re not so sure about this, it is true that Allodaposuchus and its crocodilian cohort would have been formidable predators on whatever they could get a hold of, not only the young and debilitated, but also any of the Transylvanian creatures caught unawares.
THE HAŢEG SQUAMATES
Although archosaurs dominate the Transylvanian assemblages, they do not represent the complete roster of taxa known from this region during the Late Cretaceous. The squamate (lizards and snakes) portion of the Haţeg fauna is known from screening sediment for microfaunal remains. Through these efforts, we know that scincomorphs predominate (box 3.3). Known principally from jaws, teeth, and isolated parts of the skull, Haţeg forms—such as Becklesius nopcsai, B. hoffstetteri, and Bicuspidon hatzegiensis—were probably swift, long-tailed forms resembling their present-day relatives (figure 3.10 on p. 74).31
In contrast, anguimorphs represent the slow-moving, secretive predators among present-day lizards. Known only from an upper jaw of an indeterminate anguimorph, this clade is very rare in the Haţeg fauna thus far.32
BOX 3.3 Evolutionary Relationships in Squamata
Living snakes, lizards, and amphisbaenians, plus all the descendants of their most recent common ancestor, form the clade known as Squamata (meaning “the scaled ones”). Systematically, squamates include iguanians (agamids, chameleons, and iguanids) and scleroglossans. The latter include anguimorphs (monitors, Gila monsters, and alligator lizards, among others), amphisbaenians (worm lizards), geckos, scincomorphs (skinks, whiptail lizards, and others), and serpents (snakes). The phylogenetic relationships of these taxa are provided in the figure.
Note See Vidal and Hedges 2005; Conrad 2008.
Finally, a single vertebra represents all that we know about snakes in the Late Cretaceous of Transylvania. This snake, an indeterminate madtsoiid, apparently killed its prey by constriction, much like present-day boids, to which, however, they are not particularly closely related.33
THE HAŢEG TURTLES
Turtles are ubiquitous—scutes, limb elements, and rare skull materials have been collected nearly everywhere, ranging from localities in the Haţeg Basin to Vurpăr, Jibou, Bărăbanţ, Lancrăm, Sebeş, and Oarda de Jos in the Transylvanian Depression.34 One of these has been known for some time. Named Kallokibotion bajazidi by Nopcsa in 1923,35 it may have been quite abundant: fragments of its shell occur everywhere in rocks from the region, although other parts of the skeleton are relatively rare. Kallokibotion was a moderately large, broad-headed turtle, with an oblong shell measuring much as 50 cm in length and 40 cm in width (figure 3.11), about the size of a present-day snapping turtle. Like present-day turtles, it was toothless, and the margins of its upper and lower jaws were covered by a horny beak. A slow ambler on land, Kallokibotion most likely fed on low-lying foliage and fleshy fruits. Living turtles lay clutches of leathery eggs, which are then abandoned; there is no parental care. We think this may also have been the case with Kallokibotion.
Figure 3.10. The scincomorphs Becklesius nopcsai (top left), Bicuspidon hatzegiensis (top right), and a modern scincomorph, Chalicides chalicides (the three-toed skink) (bottom). Scale = 1 mm (top left), 500 mm (top right)
Nopcsa regarded Kallokibotion as closely related to several primitive cryptodiran turtles, those forms that pull their heads into their shells by folding their necks vertically (the other major group of turtles are pleurodires—side-necked turtles—that bend their necks sideways). Recent studies now position it as the sister taxon to Testudines, the crown group consisting of the most recent common ancestor of all cryptodires and pleurodires and all the descendants of this ancestor (box 3.4).36
Figure 3.11. A restoration of the skull and carapace of Kallokibotion bajazidi. Scale = 5 cm
BOX 3.4 Evolutionary Relationships in Testudinates
Turtles—all living forms and a myriad of fossil taxa—are scientifically known as Testudinata. Characterized by the presence of a shell (composed of a dorsal carapace and a ventral plastron) that completely encloses both of the limb girdles, the absence of teeth lining the jaws, and other features, turtles are known from as far back as the Late Triassic and Early Jurassic, not only from their most primitive taxon, Proganochelys, but also from the earliest members of many of today’s major groups.
Testudines basally consist of Proganochelys and Rhaptochelydia, the latter divided into Austrochelyidae and Casichelydia. Casichelyds make up all modern turtles and their extinct relatives, including Pleurodira (side-necked turtles) and Cryptodira (hidden-necked turtles). The monophyly of these two groups is well supported by both morphological and molecular evidence. Cryptodires make up the greatest diversity among living and extinct turtles. Basally, this group includes the Early Jurassic Kayentachelys from Arizona, an unnamed clade consisting of Meiolaniidae and others, and Selmacryptodira. Kallokibotion is thought to be the sister taxon of Diacryptodira, consisting of the remainder of all cryptodirans.
Note: See Hirayama et al. 2000; Joyce 2007.
Another turtle—a yet-to-be-determined dortokid—has recently been announced by Vlad Codrea and his coworkers.37 Previously known from the Cretaceous of southern France and northern Spain, and from the early Tertiary of Romania,38 they have now been collected from Oarda de Jos and Vurpăr. Dortokids are thought to be primitive pleurodires.
THE HAŢEG MAMMALS
By this time in Earth’s prehistory, there was one great mammalian dynasty—Multituberculata—and, emerging from its shadow, two fledgling groups, marsupials and our own group, placentals (box 3.5). The most diverse and abundant of Mesozoic mammals, multituberculates are first known with certainty from Upper Jurassic deposits,39 but especially so in the Cretaceous fossil record (they survived the Cretaceous–Tertiary mass extinction, flourishing for another 35 million years before dying out in the early Oligocene 30 million years ago). These mammals ranged in size from that of a small mouse (25 g) to that of a woodchuck (4 kg).
Only multituberculates have been found in the Haţeg strata thus far, but it is not known whether the absence of marsupials and placentals is biologically real or whether they will be discovered eventually in Transylvania. The first multituberculate to be described, in 1985, was based on an isolated upper incisor from the Pui locality,
and two lower molars from the same site were described in 1986.40 Known as Barbatodon transsylvanicus,41 the lower molar from this creature was the best material available from the Haţeg Basin until 1996, when the first multituberculate skull from Sânpetru—named Kogaionon ungureanui—was described by two paleontologists from Institutul speleologic “Emil Racoviţă” Bucureşti, Costin Rădulescu and Petre-Mihai Samson (figure 3.12).42 A possible new species of Kogaionon was reported by Vlad Codrea and his coworkers in 2002.43 Finally, a multituberculate called Hainina, otherwise known from Paleocene rocks in western Europe, was also discovered in 2002 from the Late Cretaceous of the Haţeg Basin.44
BOX 3.5 Evolutionary Relationships in Mammalia
Mammalia, the large group of vertebrates in which we claim membership, presently dominates the world’s biota of large animals. The northern high latitudes have their musk ox, elk, and polar bears; the tropics, their tapir, giraffe, elephants, rhinos, hippos, tigers, and lions. Placentals all, they are united by having a special construction of the embryonic membranes between mother and embryo called the placenta. By comparison, marsupials have only an incomplete placenta, but most females carry their young in an abdominal pouch called a marsupium. Today, marsupials are best known from Australasia, but they are also found in South America, and—thanks to the pesky Virginia opossum (Didelphis virginiana)—in North America as well. Together, placentals and marsupials are grouped as Theria. The remaining living mammal group, the egg-laying Monotremata, includes platypuses and echidnas from Australia and New Guinea.
Because all these mammalian groups are still living, we consider them crown-group Mammalia, but they alone aren’t all of the major groups represented in this clade. Another group, Multituberculata, is more closely related to Theria than Monotremata is. First appearing in the Late Jurassic and going extinct in the Oligocene, these small herbivores are well represented all over the Northern Hemisphere.
Note: See Kielan-Jaworowska and Hurum 2001; Kielan-Jaworowska et al. 2004; Lillegraven et al. 1979; McKenna and Bell 2000.
Figure 3.12. A reconstruction of Kogaionon ungureanui (top), and the lower left first molar of the Haţeg multituberculate Barbatodon transsylvanicus, in occlusal (middle left) and lingual (middle right) views. Scale = 1 mm. Dorsal (bottom left) and ventral (bottom right) views of the skull of the Haţeg multituberculate Kogaionon ungureanui. Scale = 5 mm. (Top and middle after Rădulescu and Samson 1986; bottom after Rădulescu and Samson 1996)
BOX 3.6 Evolutionary Relationships in Amphibia
Modern amphibians (Lissamphibia) include frogs and toads (Anura), salamanders and newts (Caudata, or Urodela), and caecilians (Gymnophiona, or Apoda). In addition, a number of extinct taxa are known within Lissamphibia. As concerns us here, Albanerpetontidae is known from the Jurassic to the Miocene. Members of this wholly extinct clade most closely resemble modern salamanders.
Note: For Gymnophiona, see Frost et al. 2006. For Albanerpetontidae, see Gardner 2000, 2002; Gardner et al. 2003; McGowan 2002; Venczel and Gardner 2005.
Multituberculates have a long, broad skull that is superficially rodent-like in appearance, with long lower incisors, followed by a gap (called a diastema) between them and the cheek teeth. The lower premolars are specialized into shearing blades, whereas the molars are designed for crushing or grinding food, suggesting that multituberculates, including those from Haţeg, had a varied diet that included seeds as well as other larger, hard food items.45
Based on features of the most complete skeletons, paleontologists believe that at least some multituberculates were arboreal.46 With a prehensile tail, a hind limb held in a crouched position, a reversible ankle similar to that seen in squirrels, and a wide range of forelimb motion, these forms could have descended tree trunks headfirst to forage on the ground. However, other multituberculates may have been burrowers, and a third interpretation is that some forms were leapers.47 Whatever the case (and these interpretations are not mutually exclusive), it would be premature to characterize the Transylvanian forms as leapers, burrowers, or tree climbers without any postcranial skeletal material. Whatever their mode of locomotion, Barbatodon transsylvanicus and Kogaionon ungureanui would probably have been found scurrying by moonlight in the mosaic of shadowed alcoves, branches, or undergrowth, as did many nocturnal Mesozoic mammals, since the best escape from predatory dinosaurs was the cover of darkness.
Figure 3.13. The dentaries (with teeth) of (a) Hatzegobatrachus grigorescui (an anuran), (b) Paralatonia transylvanica (an anuran), and (c) Albanerpeton sp. Scale = 0.5 mm. A living anuran, (d) Discoglossus galganoi, and (e) a reconstruction of the extinct Albanerpeton sp.
THE HAŢEG AMPHIBIANS
Active screening for microvertebrate remains in Transylvania in the past two decades has produced a number of new frogs and an albanerpetontid (box 3.6).48
Hatzegobatrachus grigorescui and Paralatonia transylvanicus are small frogs (with an estimated 30–50 mm snout–vent length) known from jaw elements and various postcranial elements. Other indeterminate frogs have been reported from the Haţeg Basin: one that appears to be closely related to Eodiscoglossus, and another having an affinity with Paradiscoglossus (figure 3.13).49
BOX 3.7 Evolutionary Relationships in Actinopterygii
Actinopterygii, also known as ray-finned fish, possess fins supported by lepidotrichia (bony or horny spines). Currently consisting of nearly 30,000 species, actinopterygians are found in both freshwater and marine environments, from the highest mountain streams to the deepest sea. Three groups of actinopterygians (acipenseriforms, lepisteostids, and teleosts) are recognized from the Late Cretaceous of Transylvania.
Note: See Stiassny et al. 1996.
Albanerpeton, an enigmatic, extinct, salamanderlike taxon, is the last of the amphibians recovered from the Late Cretaceous of western Romania.50 Otherwise known from the Middle Jurassic to the Miocene of Europe, North America, and central Asia, albanerpetontids were approximately 10 cm long, predominantly terrestrial (although some may have been fossorial), and predatory.51 Albanerpetontids are placed within Lissamphibia (the crown group that includes frogs, salamanders, and caecilians).52
THE HAŢEG ACTINOPTERYGIAN FISH
The Haţeg fauna, despite coming from sediments laid down in streams and rivers (chapter 4), is counterintuitively very poor in fish of any kind (box 3.7). Thus far, the only known fossil remains from members of this fully aquatic community are acipenseriforms (chondrosteans), lepisteostids (holosteans), and teleosts. Living acipenseriforms consist of sturgeons and paddlefish, both with cartilaginous skeletons, elongate bodies, and triangular snouts. Acipenseriforms are bottom feeders. Rhomboidal, thick scales and a conical, slightly recurved tooth attest to the Haţeg presence of the gar Lepisosteus.53 Present-day gars are long-snouted carnivores, with a long, slender body and a heterocercal caudal fin. Finally, characiform teleosts have been reported from the Haţeg Basin.54 Today we know some of these characiforms as the popular aquarium pets called tetras (figure 3.14).
Figure 3.14. Living representatives of the Transylvanian actinopterygians: gar (Lepisosteus oculatus; top); blue neon tetra (Paracheirodon simulans; middle), a characiform teleost; and sturgeon (Acipenser transmontanus; bottom)
CHAPTER 4
Living on the Edge
What was the Transylvanian region like some 70 million years ago, during the Maastrichtian age of the Late Cretaceous? To Franz Baron Nopcsa, the prehistoric landscape had a distinctly different appearance than it does in modern times. Here is how he might have imagined it, with a bit of a current paleogeographic spin.
Seen from high in the air, the Transylvanian region is an island—a speck among other specks—that, together with its neighbors, forms a chain that extends across the northern flank of a broad seaway. This great body of water, called the Neotethyan Ocean, covers what is now most of Europe and Russia to the north and northern Africa to the south. Some islands are small oceanic volcanoes no more than 100 square km in area, but a few are the size of present-day
Madagascar. One of the latter, which would form what is now part of southern France and the majority of Spain, is the westernmost island of the chain, some 2,500 km away from Haţeg Island. The other end of the chain, in what is now the Caucasus, lies 2,000 km away from us, and we are some 3,000 km from the nearest coast of northern Africa (Plate VI).
Thus our island of interest—Haţeg Island—is halfway along this chain, some 20°–30° North Paleolatitude, just below the Late Cretaceous position of the Tropic of Cancer. As we descend through the tropical clouds toward our island, the air becomes more humid and we see several highflying birds and pterosaurs. The green flanks of volcanoes stand out against the deep blue of the surrounding Neotethyan Ocean as we begin to perceive the horseshoe shape of the island and its extent, some 75,000 square km in area (about the size of present-day Sri Lanka).1
As we get ever closer, the neighboring islands disappear from view. An occasional ash cloud drifts up from the cauldron of one of the volcanoes on Haţeg Island, but otherwise the air is clear—clear and thick with humidity and the white noise of insect cacophony. The climate on Haţeg Island is largely controlled by the surrounding warm currents of the Neotethyan Ocean and the prevailing westerly winds. Parts of the island receive abundant but seasonal rains, such that the island undergoes alternating wet and dry periods.
The island’s details emerge and we see not a single geometric unit, but tiers of diverse habitats and their denizens. Beaches ring the periphery; the island is rugged in places, and lava hints at a violent volcanic past. Most of the lower elevations of the island are covered with diverse rain forests. Farther inland, a series of low hills and terraces leads away from the shore. This gently sloping alluvial plain is well drained by numerous, rapidly flowing, shallow rivers. Their channels are interspersed with sand bars and occasional, short-lived, shallow lakes. Abundant fetid swamps occupy the lower-lying regions. Floodplains, on which soils have formed and vegetation flourishes, are broadly distributed among water and wetlands. There is luxuriant plant growth everywhere: dense forests towering above a lush tropical understory, and river banks covered with a riot of colors from flowering angiosperms.
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