Zalmoxes

''Zalmoxes'' is a genus of rhabdodontid ornithopod dinosaur from the Maastrichtian age of the Late Cretaceous in what is now Romania. The genus is known from specimens first named as the species '' Mochlodon robustum'' in 1899 by Franz Nopcsa before being reclassified as '' Rhabdodon robustum'' by him in 1915. In 1990, this name was corrected to ''Rhabdodon robustus'' by George Olshevsky and, in 2003, the species was once more reclassified as the type species ''Zalmoxes robustus''. ''Zalmoxes'' refers to the Dacian deity Zalmoxis and ''robustus'' refers to the robustness of the remains. Also in 2003, another species was named, ''Zalmoxes shqiperorum'', named for the Albanian name for Albanians.

History of discovery

''Zalmoxes'' was first known from numerous fossils found in Transylvania, which were named as the species '' Mochlodon robustus'' by Baron Franz Nopcsa in 1899. The specific name referred to its robust build. In 1915, Nopcsa renamed the species to '' Rhabdodon robustum'', amended in 2003 by David B. Weishampel, Coralia-Maria Jianu, Zoltan Csiki, and David B. Norman. Weishampel ''et al.'' (2003) published a paper on new remains from Romania, which they found to represent a new species. They found ''R. robustus'' was sufficiently different from ''Rhabdodon'' and named the new genus ''Zalmoxes'' for the former. The genus refers to the Thracian deity Zalmoxis (sometimes spelled Zalmoxes), who retreated for three years in a crypt to be resurrected on the fourth year. Likewise, the animal ''Zalmoxes'' had been liberated from its fossil grave to attain taxonomic immortality. The naming article further explained this by referring to a Greek legend according to which Zalmoxes was a slave of Pythagoras, when he travelled to Dacia and was deified by the Dacian people. In addition, Weishampel ''et al.'' named the new specimens ''Zalmoxes shqiperorum'', after Shqiperia, the Albanian name for Albania, with which Nopcsa had a special relationship. One specimen is now assigned to ''Telmatosaurus'', while another specimen is also suspected to belong to that genus based on similar basicrania morphology.

Description

''Zalmoxes'' is a rather small genus of bipedal herbivore with a large triangular head and a beak. ''Z. shqiperorum'' is the larger species, known from a subadult long, as well as an early juvenile in length, while ''Z. robustus'' subadults range from long. An adult ''Z. robustus'' would have measured up to in length and in body mass. An unnamed species of ''Zalmoxes'', is known from larger sizes, with an adult in length. Although Nopcsa thought the small size of ''Zalmoxes'' was due to island dwarfism, Attila Ösi and colleagues found it was closer to the size of the rhabdodontid ancestor, with larger ''Rhabdodon'' and smaller ''Mochlodon'' having island gigantism and island dwarfism respectively. However, when the species of ''Zalmoxes'' are taken into account separately, it can be seen than ''Z. shqiperorum'' continued the general size trend from '' Orodromeus'' to ''Tenontosaurus'', while ''Z. robustus'' may have had slight nanism. ''Zalmoxes'' had a relatively slow growth rate and long growth period, suggesting that this dinosaur may have had a unique growth strategy.

''Z. robustus'' is known from about 80% of the skull. However, no complete articulated skull is known, and most of the bones do not overlap and are found in isolation. Weishampel ''et al.'' found that these likely represented one individual, as the bones were from the same formation and are the same colour. Four individuals were identified by Nopcsa for ''Z. robustus'', and from these it can be seen that there is skeletal variation in the species. Like with the cranial material, vertebrae of ''Z. robustus'' are often found isolated. All regions of the vertebral column are represented in the fossil record, although no sternal plates have been found yet. The sacrum includes three vertebrae, with two sacrodorsals (dorsal vertebrae in the sacrum) and three sacrocaudals (caudal vertebrae in the sacrum). The limb and girdle bones are also well represented, with only the hands ( manus) and feet ( pes) mostly lacking.

While more poorly known than ''Z. robustus'', ''Z. shqiperorum'' is still known from a relatively large amount of the skeleton. Only two mostly complete skeletons are known, the holotype adult, and a referred juvenile. The lower jaw (dentary) of ''Z. shqiperorum'' is relatively shorter than the equivalent in ''Z. robustus'', although it is much larger. Ossified tendons are known from the juvenile specimen, showing that they were circular or elliptical in cross section and have fine striations in ''Z. shqiperorum''. Cervical, dorsal and caudal vertebrae are known from ''Z. shqiperorum'', although the former two are only represented by juvenile material. A complete articulated sacrum is known for ''Z. shqiperorum'', with three vertebrae and at least two sacrodorsals. No manual material is known from the species, although a metatarsal and a few phalanges are known.

Classification

The species of ''Mochlodon'', ''Rhabdodon'' and ''Zalmoxes'' had long had an uncertain phylogenetic placement, being referred to various families. Nopcsa (1901) also had referred the genus to Hypsilophodontidae, and he suggested affinities with ''Camptosaurus'' in 1902, 1904 and 1915. Nopcsa (1915) also realized that ''Rhabdodon '' and ''Mochlodon'' may be congeneric, placing the complex in Camptosauridae.

For the next half-century, taxonomic workers found ''Rhabdodon'' and ''Mochlodon'' within either Camptosauridae or Iguanodontidae. However, Paul Sereno (1986) found that ''Rhabdodon'' and ''Mochlodon'' were within Iguanodontia. The ICZN (1988) resolved this complication, selecting the ornithopod ''Rhabdodon'' as having priority over ''Mochlodon''. From this publication, scientists began placing ''Rhabdodon'' and ''Mochlodon'' within Euornithopoda. In 2003, Weishampel ''et al.'' named a new family for ''Mochlodon'', ''Rhabdodon'' and the new genus ''Zalmoxes''. This family, Rhabdodontidae, was placed as a derived within Iguanodontia. Further studies support this placement of Rhabdodontidae, phylogenetically between ''Talenkauen'' and ''Tenontosaurus''.

Below are two possible phylogenies of Rhabdodontidae by McDonald ''et al.'' (2010; left), and Ösi ''et al.'' (2012; right).

Paleobiology

''Zalmoxes'' has a more robust build than its precursors and more derived relatives. Infraspecific ontogenetic growth is relatively well known in ''Zalmoxes'' as there is juvenile material known for the species. Nopcsa proposed that the animals of the Hateg Basin, which were smaller than their relatives elsewhere, adapted through insular dwarfism. Fossils of both species of ''Zalmoxes'' have been unearthed in the Sânpetru Formation, the Sebes Formation and Densuş-Ciula Formation in Romania, both species have been found exclusively in the Hateg Island region.

Diet

A scientific paper from 2003 found that ''Zalmoxes'' most likely had a diet that consisted of tough fibrous plants like soft shoots, horsetails, angiosperms, pteridophytes, and ferns. Further studies showed that it could process and digest C3 plants.

References

External links

Dinosaur Mailing List entry (announces the formal publication of ''Zalmoxes'')

{{Portal bar, Dinosaurs, Paleontology, Romania

Rhabdodontidae
Dinosaur genera
Maastrichtian dinosaurs
Dinosaurs of Romania
Fossil taxa described in 2003
Fossil taxa described in 1899
Taxa named by Franz Nopcsa von Felső-Szilvás
Taxa named by David B. Weishampel
Taxa named by David B. Norman