[D] Mochlodon suessi [jG]
Describer
Seeley, 1881 / Bunzel, 1871
Time
Cretaceous Late Campanian Maastrichtian
Classification
Ornithischia Ornithopoda Iguanodontia Rhabdodontidae
Diet
Herbivore
Fossilsite
Gosau Formation, Austria
Fall Under
Rhabdodon
Info
Genus
Rhabdodon (Matheron, 1869) = ?Mochlodon (Seeley, 1881 / Bunzel, 1871)
Rhabdodon (Matheron, 1869) > Rhabdodon priscus (Matheron, 1869) >> Oligosaurus adelus (Seeley, 1881) > Ornithomerus gracilis (Seeley, 1881) >> Mochlodon suessi (Bunzel, 1871) > Iguanodon suessi (Bunzel, 1871)
Rhabdodon (Matheron, 1869) > Rhabdodon septimanicus (Buffetaut& Le Loeuff, 1991)
Rhabdodon (Matheron, 1869) > Mochlodon vorosi (Osi, Prondvai, Butler, Weishampel, 2012)
Ősi, A.; Prondvai, E.; Butler, R.; Weishampel, D. B. (2012). Evans, Alistair Robert. ed. ’Phylogeny, Histology and Inferred Body Size Evolution in a New Rhabdodontid Dinosaur from the Late Cretaceous of Hungary.’ PLoS ONE 7 (9): e44318. doi:10.1371/journal.pone.0044318 [Mochlodon vorosi]
Systematic palaeontology
Ornithischia Seeley, 1887
Ornithopoda Marsh, 1881
Iguanodontia Sereno, 1986 (sensu Sereno 2005)
Rhabdodontidae Weishampel, Jianu, Csiki & Norman, 2003
Mochlodon Seeley, 1881
Type species
Iguanodon suessii Bunzel, later recombined as Mochlodon suessii by Seeley, as Mochlodon suessi by Nopcsa, as Mochlodon suessi by Weishampel et al., and as Rhabdodon suessi by Steel and Pincemaille-Quillevere. The type material was referred to Zalmoxes sp. by Sachs and Hornung.
Lectotype
Right dentary (PIUW 2349/2).
Type locality
Konstantin mining tunnel, Felbering Mine, Muthmannsdorf, Wiener Neustadt-Land district, Niedero¨sterreich (Lower Austria), Austria.
Type horizon
Grunbach Formation, Gosau Group, lower Campanian.
Diagnosis
Small-bodied rhabdodontid dinosaur with a total body length of approximately 1.5–2 meters distinguished fromRhabdodon and Zalmoxes on the basis of the following unique combination of characters (autapomorphies marked with an asterisk): mandibular symphysis is only slightly curved medially; *dorsal margin of the symphyseal region has a deep and caudally wider groove; *depression (depth ranging from 1–3 mm) on the lateral wall of the caudal part of the dentary, just below the coronoid process, that becomes more obvious in larger individuals; *the dorsal edge of the sympysis in lateral view is directed straight rostrally or slightly rostroventrally (in Mochlodon suessi), parallel to the long axis of the dentary.
Remarks
Following the work of Seeley and the early works of Nopcsa, the material of Mochlodon suessi from Austria was referred to Rhabdodon by most authors. However, Weishampel et al. and Weishampel and Jianu regarded Mochlodon suessi as a nomen dubium because they considered the Austrian material to be non-diagnostic. Sachs and Hornung redescribed the Austrian material and concluded that, although in their opinion indeterminate, it is more similar to the Transylvanian rhabdodontid Zalmoxes than to Rhabdodon.
As a result, they referred the Austrian material to Zalmoxes sp. Thus, the Austrian material has been referred on at least one occasion to every genus in Rhabdodontidae during the last 135 years, and still there is no consensus concerning its taxonomic status. The Hungarian material described here helps to clarify this problem because it is not from Rhabdodon or Zalmoxes, but is most similar to the Austrian remains (see below).
This similarity is further supported by the close palaeogeographic position (,100 km) of the two localities during the Late Cretaceous, and their similar stratigraphic age. Based on autapomorphic features of the dentary (not recognized by Sachs and Hornung), we here resurrect the generic name Mochlodon for the Austrian (early Campanian) and Hungarian (Santonian) material, but distinguish two differentspecies based upon osteological differences of the dentaries.
Mochlodon suessi (Bunzel 1871)
Lectotype
Right dentary (PIUW 2349/2).
Type locality
Konstantin mining tunnel, Felbering Mine, Muthmannsdorf, Wiener Neustadt-Land district, Niedero¨sterreich (Lower Austria), Austria.
Type horizon
Grunbach Formation, Gosau Group, lower Campanian.
Diagnosis
The dentary of Mochlodon suessi differs from that of the Hungarian species Mochlodon vorosi n. sp. (see below) in having the dorsal margin of the symphyseal region slightly rostroventrally oriented and its rostral tip in a deeper position. Referred material. Dentary tooth (PIUW 2349/3); maxillarytooth (PIUW 2349/4); fragmentary parietal (PIUW 2349/54); fragmentary left scapula (PIUW 3518); fragmentary ?radius (PIUW 3517); ?manual ungual (PIUW 2349/38); fragmentary left femur (PIUW 2349/3); fragmentary ?right tibia (PIUW 2348/35).
Remarks
The lectotype of Mochlodon suessi is one of the smallest rhabdodontid dentaries (74 mm preserved length) that might well represent a juvenile specimen.