Archaeoceratops

Archaeoceratops
	Reconstruction of Archaeoceratops
Temporal occurrence
	Lower Cretaceous ( Aptium ? - Albium )
	126.3 (?) To 100.5 million years
Locations
	China;
Systematics
	Pelvic dinosaur (Ornithischia)
	Cerapoda
	Marginocephalia
	Ceratopsia
	Neoceratopsia
	Archaeoceratops
Scientific name
	Archaeoceratops
	Dong & Azuma , 1997
Art
	A. oshimai Dong & Azuma, 1997 ( type ); A. yujingziensis You et al., 2010;

Archaeoceratops is a genus of pelvic dinosaurs (Ornithischia) from the group of Ceratopsia . The genus is one of the more primitive representatives of this group. In addition to the type species Archaeoceratops oshimai , another species Archaeoceratops yujingziensis is known.

Etymology and history of research

The first fossil remains of Archaeoceratops were discovered during the "Sino − Japanese Silk Road Dinosaur Expedition" of 1992 in the Xinminbao Group in the Mazong Mountains (Mǎzōng Shān; Chinese 马鬃山 ) of the Gansu province and in 1997 by Dong and Azuma under the Name Archaeoceratops oshimai first described . The generic name is derived from the Greek words ἀρχαῖος archaios ("old") and the ending " -ceratops " from ancient Greek κέρας kéras ("horn") and ὤψ ōps ("eye", "face"), a common part of the Ceratopsia name . It can be roughly translated as "old horn face" and alludes to the primeval character of this genus of Ceratopsia .

In 2003 the holotype (IVPP V 11114) and the paratype (IVPP V 11115) were re-described by A. oshimai , both at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing , by You and Dodson .

In 2010, You et al. a second species of the genus Archaeoceratops is described as Archaeoceratops yujingziensis (holotype CAGS-IG-VD-003). The find material also comes from the Xinminbao group in the Mǎzōng Shān area and was, initially unrecognized, only uncovered as an accompanying find in the course of the preparation of another dinosaur fossil.

Fossil record

The holotype (IVPP V 11114) of Archaeoceratops oshimai contains a well-preserved, almost complete skull including the associated lower jaw bones as well as parts of the spine and pelvis. The paratype (IVPP V 11115) contains parts of the spine, including an almost completely preserved tail, parts of the pelvis and hind limbs, and a complete foot skeleton.

Archaeoceratops yujingziensis fossil material includes a partially preserved skull, a right mandibular bone, and parts of the postcranial skeleton, including parts of the right shoulder blade, both femurs, 2 metatarsals and 3 toe bones .

features

Skull of the holotype (IVPP V 11114) of Archaeoceratops oshimai ; from You & Dodson (2003) scale bar = 2 cm

The representatives of the genus Archaeoceratops were relatively small Ceratopsia . The body length of the holotype (IVPP V 11114) of Archaeoceratops oshimai is estimated to be approx. 80 cm, with a hip height of approx. 33 cm. The cranial skeleton of the holotype shows no evidence that it was a juvenile. However, it may be a not yet fully grown adult animal . The body length of the paratype (IVPP V 11115) is given as about 67 cm, with a hip height of about 28 cm.

The holotype of Archaeoceratops yujingziensis (CAGS-IG-VD-003) was even smaller with an estimated body length of only approx. 55 cm and a hip height of approx. 23 cm. There are no conclusive signs of an individual's youth.

Cranial skeleton

The skull is composed compared to the body, very large, parietal and shed leg neck shield formed, however, relatively small. As with all ceratopsians, there was a rostral bone on the front part of the upper jaw , this was pointed at the front and with the also pointed predentale (at the tip of the lower jaw ) formed the parrot-like snout typical of this group of dinosaurs. There are no approaches for over-eye horns or for a nasal horn. A primeval feature is that teeth were still present on the intermaxillary bone in the upper jaw. These were simply built and pin-shaped. The teeth behind it had a leaf-shaped crown and were adapted to a plant-based diet. The teeth of the maxilla and the lower jaw each have only one tooth root ; also a typical feature of the basal representatives of the Ceratopsia . More developed representatives of the group usually show two roots per tooth.

Sacrum and ilium of the holotype (IVPP V 11114) of Archaeoceratops oshimai ; from You & Dodson (2003) scale bar = 2 cm

A weak, bumpy ornamentation on the outside of the zygomatic bone is considered to be autapomorphy of the cranial skeleton .

In A. yujingziensis , in contrast to A. oshimai , the area of the intermaxillary bone is laterally widened to form a kind of spoon-shaped beak, so that the teeth of the intermaxillary bone are no longer in line with those of the maxilla . The teeth of the intermaxillary bones in A. yujingziensis also show a noticeable welt that is not present in A. oshimai . Other distinguishing features of A. yujingziensis are the lack of a "primary ridge" on the inside of the maxilla teeth and a largely horizontal platform between the root and crown of the teeth in the lower jaw.

Postcranial skeleton

The ilium of A. oshimai shows the distinguishing feature of a striking recess on the outer side of the "seat leg extension" ( "ischiadic peduncle"), so that extension of the ilium of the ischium is connected. The surface structure of the cavity suggests a lack of ossification center. Since this peculiarity was found in both the holotype (IVPP V 11114) and the paratype (IVPP V 11115) of Archaeoceratops oshimai , it does not seem to be a pathological change. The function of this feature is unknown. The previously known A. yujingziensis fossil material does not contain any corresponding skeletal elements. It is therefore unclear whether it is a genus-typical characteristic or a species-typical characteristic, restricted to A. oshimai .

limbs

Paratype foot skeleton (IVPP V 11115) of Archaeoceratops oshimai ; from You & Dodson (2003) scale bar = 2 cm

The paratype (IVPP V 11115) of Archaeoceratops oshimai contains a largely completely preserved foot skeleton of the right hind leg. Another autapomorphism here is a clear tapering of the shaft and the proximal ends of the metatarsals .

In many of the basal representatives of the Ceratopsians, the front legs were significantly shorter than the rear legs and it is assumed that these dinosaurs mostly moved on two legs ( biped ). However, it is unclear whether this interpretation can also be applied to Archaeoceratops , since the front legs are so far unknown.

Systematics

Archaeoceratops is incorporated into the Neoceratopsia within the Ceratopsia . When it was first described, it was considered the most primitive representative of Neoceratopsia and a sister group of all other dinosaurs in this group. In the meantime, with Liaoceratops , Yamaceratops and others, other basal Neoceratopsia have been discovered that are possibly more primitive. Apart from a few controversial genera, Archaeoceratops is one of the oldest known representatives of this group of dinosaurs, otherwise known mainly from the Upper Cretaceous .

Paleecology

The above anatomical fossil record shows Archaeoceratops to be a genus of small, possibly at least partially bipedal, herbivorous dinosaurs. Further information on the way of life of Archaeoceratops is provided by sedimentological and palynological analyzes of the corresponding layers of finds. These analyzes indicate that the sediments of the Xinminbao Group were deposited under semi-arid , subtropical conditions in a landscape dominated by lakes and rivers (“fluviolacustrines”) within a rift basin.

literature

You Hailu, Peter Dodson : Basal Ceratopsia. In: David B. Weishampel , Peter Dodson, Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , pp. 478-493, digitized version (PDF; 808 kB) .

Web links

Datasheet at Dino Directory

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j H.−L. You & P. Dodson: Redescription of neoceratopsian dinosaur Archaeoceratops and early evolution of Neoceratopsia. In: Acta Palaeontologica Polonica , Vol. 48, No. 2, pp. 261–272, 2003. (digitized version )

↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ H.−L. You, K. Tanoue & P. Dodson: A New Species of Archaeoceratops (Dinosauria: Neoceratopsia) from the Early Cretaceous of the Mazongshan Area, Northwestern China. In: MJ Ryan, BJ Chinnery-Allgeier & DA Eberth (Eds.): New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium. Pp. 59–67, Bloomington and Indianapolis, Indiana University Press, 2010. ISBN 978-0-253-35358-0 (excerpt)

↑ H.-L. You, & P. Dodson: Basal Ceratopsia. In: DB Weishampel, P. Dodson & H. Osmólska (eds.): The Dinosauria. 2nd edition, University of California Press, Berkeley CA et al. Pp. 478-493, 2004, ISBN 0-520-24209-2 .

↑ F. Tang, Z.-X. Luo, Z.-H. Zhou, H.-L. You, JA Georgi, Z.-L. Tang & X.-Z. Wang: Biostratigraphy and palaeoenvironment of the dinosaur-bearing sediments in Lower Cretaceous of Mazongshan area, Gansu Province, China . In: Cretaceous Research , Vol. 22, pp. 115–129, 2001 (digitized version )

[You_&_Dodson,_2003-1] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j H.−L. You & P. Dodson: Redescription of neoceratopsian dinosaur Archaeoceratops and early evolution of Neoceratopsia. In: Acta Palaeontologica Polonica , Vol. 48, No. 2, pp. 261–272, 2003. (digitized version )

[You_et_al.,_2010-2] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ H.−L. You, K. Tanoue & P. Dodson: A New Species of Archaeoceratops (Dinosauria: Neoceratopsia) from the Early Cretaceous of the Mazongshan Area, Northwestern China. In: MJ Ryan, BJ Chinnery-Allgeier & DA Eberth (Eds.): New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium. Pp. 59–67, Bloomington and Indianapolis, Indiana University Press, 2010. ISBN 978-0-253-35358-0 (excerpt)

[You_&_Dodson,_2004-3] H.-L. You, & P. Dodson: Basal Ceratopsia. In: DB Weishampel, P. Dodson & H. Osmólska (eds.): The Dinosauria. 2nd edition, University of California Press, Berkeley CA et al. Pp. 478-493, 2004, ISBN 0-520-24209-2 .

[Tang_et_al.,_2001-4] F. Tang, Z.-X. Luo, Z.-H. Zhou, H.-L. You, JA Georgi, Z.-L. Tang & X.-Z. Wang: Biostratigraphy and palaeoenvironment of the dinosaur-bearing sediments in Lower Cretaceous of Mazongshan area, Gansu Province, China . In: Cretaceous Research , Vol. 22, pp. 115–129, 2001 (digitized version )