Macrogryphosaurus

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Macrogryphosaurus
Temporal occurrence
Upper Cretaceous ( Coniacium )
89.7 to 86.3 million years
Locations
Systematics
Dinosaur (dinosauria)
Ornithischia
Ornithopoda
Iguanodontia
Elasmaria
Macrogryphosaurus
Scientific name
Macrogryphosaurus
Calvo , Porfiri & Novas , 2007
Art
  • Macrogryphosaurus gondwanicus

Macrogryphosaurus is a genus ornithopod dinosaur and a basal representative of the Iguanodontia . So far, a single fragmentary skeleton without a skull is known, which was found in the Portezuelo Formation in the Upper Cretaceous ( Coniacium ) of Argentina . The genus wasscientifically described in 2007 with the only species Macrogryphosaurus gondwanicus . The most closely related genus and sister genus is Talenkauen , with which Macrogryphosaurus is combined into a group called Elasmaria. Macrogryphosaurus was a two-legged herbivore about six meters long,which was characterized among other things by thin, ossified plates arranged on the side of the trunk.

features

The holotype specimen is estimated to be 6 meters long; however, the not yet fused sutures between vertebral arches and vertebral centers on some vertebrae suggest that this individual was not yet fully grown. Macrogryphosaurus was thus one of the largest ornithopods in South America outside of the Hadrosauridae .

Of the total of ten cervical vertebrae, eight have been preserved; the first and second cervical vertebrae (atlas and axis) are missing. As with the closely related sister genus Talenkauen , the third cervical vertebra shows well-developed epipophyses (processes that are located above the postzygapophyses); a feature that is unusual for ornithischians. The vertebrae series is completely anatomically connected and consists of 14 vertebrae, a small number for ornithopods. The well-developed hyposphene of the last vertebra is unique for ornithopods and thus an autapomorphy of Macrogryphosaurus . The tail has only survived in fragments; 16 mostly incomplete caudal vertebrae are known. Further autapomorphies are the three- pointed sternum and its four flattened, twisted and distally elongated ribs. However, only three of these four sternum ribs have survived. Bony, approximately circular and 1 to 3 mm thick plates were arranged on the side of the trunk. Such ossifications have otherwise only been found in ornithopods in the sister genus Talenkauen and in Thescelosaurus . In contrast to these genera, one of these plates in Macrogryphosaurus was located in front of the sternum, which represents a further autapomorphy.

Systematics

Macrogryphosaurus was a basal Iguanodontia within the Euiguanodontia and closely related to the also South American Talenkaue santacrucensis from the Maastrichtian . The descriptors came to the conclusion that Macrogryphosaurus and Talenkaue form a new, monophyletic group, the Elasmaria. As synapomorphies (jointly derived features) of this group, they list the thin ossified plates and the well-developed epipophyses of the third cervical vertebra.

Find and naming

The skeleton was discovered in 1999 during an expedition of the Universidad Nacional del Comahue on the west bank of Lake Mari Menuco in the Argentine province of Neuquén . Stratigraphically , the find comes from the Portezuelo Formation , a member of the Neuquén group . The rocks of the site are dated to the Coniacium . The specimen found ( holotype , copy number MUCPv-321) consists of the incomplete spine, ribs, sternum a four bony plates and two iliac bones (Ilia), the pubic bone (pubis) and the seat leg (ischium). The skeleton was articulated in the found position and pointed up with the belly, with the cervical and back spine lying straight.

Macrogryphosaurus means something like "large, enigmatic lizard" ( Gr. Macro - "large", grypho - "enigmatic", saurus - "lizard"). The species name gondwanicus refers to what was then the southern continent of Gondwana , on which this dinosaur lived.

literature