New Evidence for Deinocheirus mirificus

Due nuovi esemplari dell'enigmatico Teropode mongolo Deinocheirus mirificus sono stati ufficialmente presentati al meeting SVP 2013 in un abstract da Lee et al. (2013).
Dopo decenni di speculazioni basate sulla coppia di arti anteriori (enormi) che formano l'olotipo del Taxon, oggi abbiamo abbastanza elementi da permetterci di ricostruire l'animale in modo verosimile, ed esso si presenta in modo sensibilmente diverso da quanto ipotizzato.
I nuovi reperti (appartenenti ad un esemplare maturo ed un subadulto) comprendono gran parte dello scheletro postcraniale (il cranio purtoppo risulta assente) ad esclusione di alcune vertebre dorsali, gran parte delle vertebre caudali distali ed entrambe i piedi e sono stati assegnati a Deinocheirus sulla base della mirabile morfologia degli arti anteriori.
Deinocheirus risulta (come precedente ipotizzato) un ornithomimosauro basale, tuttavia presenta caratteristiche morfologiche uniche, probabilmente fortemente legate al suo gigantismo.
Nonostante esso appaia relativamente snello,con lunghe costole dritte, infatti possiede bacino ed arti posteriori pesantemente costruiti ed un femore molto robusto, più lungo del tibiotarso e spine neurali appaiono alte, soprattutto al livello del bacino, al di sopra del quale doveva ergersi un sorta di gobba.
La presenza di gastroliti associati agli esemplari supporta fortemente una dieta a base di vegetali per il Taxon.

Sotto l'abstract completo di Lee et al. (2013).

NEW SPECIMENS OF DEINOCHEIRUS MIRIFICUS FROM THE LATE CRETACEOUS OF MONGOLIA

LEE, Yuong-Nam, Korea Institute of Geoscience and Mineral Resources, Daejeon, Korea, Republic of (South); BARSBOLD, Rinchen, Paleontological Center, Ulaanbaatar, Mongolia; CURRIE, Philip, University of Alberta, Edmonton, AB, Canada; KOBAYASHI, Yoshitsugu, Hokkaido University Museum, Sapporo, Japan; LEE, Hang- Jae, Korea Institute of Geoscience and Mineral Resources, Daejeon, Korea, Republic of (South)

The holotype of Deinocheirus mirificus was collected by the Polish-Mongolian Palaeontological Expedition at Altan Uul III in 1965. Because the holotype was known mainly on the basis of giant forelimbs with scapulocoracoids, Deinocheirus has remained one of the most mysterious dinosaurs. Two new specimens of Deinocheirus were discovered in the Nemegt Formation of Altan Uul IV in 2006 and Bugin Tsav in 2009 by members of the Korea-Mongolia International Dinosaur Expedition (KID). Except for the skull, middle dorsal and most of the distal caudal vertebrae, the right forelimb, left manus, and both pedes, the remaining parts of the skeleton (Mongolian Paleontological Center [MPC]-D 100/127) including a left forelimb clearly identifiable as Deinocheirus were collected. The humerus (993 mm in length) is longer than the 938 mm humerus of the holotype. The Altan Uul IV specimen (MPC-D 100/128) is a subadult Deinocheirus (approximately 72% of MPC-D 100/127), which consists of post-cervical vertebrae, ilia, ischia, and hind limbs. Both specimens provide important paleontological evidence for exact postcranial reconstruction of Deinocheirus mirificus. Cladistic analysis indicates that Deinocheirus is a basal member of Ornithomimosauria, but many new unique skeletal features appear to be quite different from other ornithomimosaurs. These include extreme pneumaticity of tall, anterodorsally oriented distal dorsal neural spines (7~8 times taller than centrum height) with basal webbing, fused sacral neural spines forming a midline plate of bone that extends dorsally up to 170% of the height of the ilium, ventrally keeled sacral centra, a well-developed iliotibialis flange, a posterodorsally projecting posterior iliac blade with a concave dorsal margin, a steeply raised anterior dorsal margin of the ilium, an anteriorly inclined brevis shelf, vertically well-separated iliac blades above the sacrum, an completely enclosed pubic obturator foramen, triangular pubic boot in distal view, vertical ridges on anterior and posterior edges of medial surface of the femoral head, and a robust femur that is longer than tibiotarsus. These features suggest that Deinocheirus (unlike other ornithomimosaurs) was not a fastrunning animal, but a bulky animal with a heavily built pelvis and hind limbs. However, the dorsal ribs are tall and relatively straight, suggesting that the animal was narrowbodied. A large number of gastroliths (>1100 ranging from 8 to 87 mm) were collected from the abdominal region of MPC-D 100/127, suggesting Deinocheirus was an herbivore.