Eocursor

Eocursor
	Artistic live representation of Eocursor
Temporal occurrence
	Upper Triassic (late Norium or Rhaetium )
	210 to 201.3 million years
Locations
	Free State ( South Africa );
Systematics
	Archosauria
	Ornithodira
	Dinosaur (dinosauria)
	Pelvic dinosaur (Ornithischia)
	Eocursor
Scientific name
	Eocursor
	Butler , Smith & Norman , 2007
Art
	E. parvus Butler, Smith & Norman, 2007 ;

Eocursor ("runner of the dawn") is a genus of dinosaurs and a very early and original representative of the bird pelvic dinosaur (Ornithischia). The only specimen to date wasrecoveredin South Africa in 1993from a layer of the Lower Elliot Formation ( Upper Triassic , late Norium or Rhaetian ). Based on this specimen, which includes both cranial bones and some postcranial bones, the first scientific description of the only known species under the name Eocursor parvus was made in 2007. Despite its fragmentary tradition, Eocursor is still the most completely preserved Triassic pelvic dinosaur.

Very early bird pelvic dinosaurs are generally only known from very few finds, which is why Eocursor is of great scientific importance for understanding the early evolution of this group.

etymology

The name Eocursor parvus ( Greek eos - "dawn"; Latin cursor - "runner"; Latin parvus - "small") means something like "little runner of the dawn" and refers to the developmental position, the ability to fast Running and on the small size of this bird pelvic dinosaur.

description

Eocursor was a slightly built, two-legged dinosaur with an estimated length of about three feet and a waist height of about 30 centimeters. It was probably a fast runner, as the proportions of the leg bones indicate. The general physique resembles that of the Lower Jurassic pelvic dinosaurs such as Lesothosaurus and Scutellosaurus , which in turn all differ only slightly in habit from contemporary lizard dinosaurs. However, the hand was comparatively robust and elongated and thus resembles that of the Heterodontosauridae , a relatively specialized group of primitive bird pelvic dinosaurs. The morphology of the triangular teeth indicates that Eocursor was at least partially feeding on plants .

With its pubic bone pointing back and down ( opisthopubic pelvis ) and a clearly pronounced prepubis, i.e. H. a forward-pointing appendage at the upper (proximal) end of the pubic bone, Eocursor shows key features of the pelvic dinosaur.

Details of the first find

The only remains of Eocursor so far come from a three-meter-thick, massive, dark red-brown siltstone horizon in the highest part of the late Triassic Lower Elliot Formation of the Karoo main basin . The sediments of the Elliot Formation are generally traced back to fluvial deposits in arid and warm climates. The exact age of the find layer is indicated by “? Norium ”. However, this information is based on an older chronostratigraphic structure of the Upper Triassic, so that in addition to the uppermost norium, the rhaetium also comes into question as a period of deposit. ^§ The site is located in the area of the farm Damplaats 55 (formerly Ladybrand District, today Mantsopa Municipality ) in the south of the South African province of Free State .

The bones found to be disarticulated (not anatomically related) include various cranial bones, various vertebrae, shoulder blades and forelegs, pelvis and hind limbs. The material is kept in the collection of the Iziko South African Museum in Cape Town under copy number SAM-PK-K8025 .

Systematics

Eocursor is an early and original bird pelvic dinosaur. The result of the relationship analysis, which was carried out in the context of the first description, shows him as a basic but not the most basic representative of this large group, whereby there is a sister group relationship with the common group of the "higher" bird pelvic dinosaurs ( genasauria ):

Dinosauria

Lizard dinosaur (Saurischia)

Pelvic dinosaur (Ornithischia)

† Pisanosaurus

† Heterodontosauridae

	† Eocursor

	† Genasauria ("higher" ornithic)

Remarks

^§Butler et al. (2007) refer to a work by Smith & Kitching from 1997, who base their age classification of the Lower Elliot Formation on a tetrapod bio- and ichnostratigraphic work by Olsen & Galton from 1984. Olsen & Galton (1984) place the Lower Elliot Formation in the Norium and the Upper Elliot Formation in the Lower Jurassic ( Sinemurian and Hettangian ). However, in their correlation table, the rhaetium is missing in the chronostratigraphic structure, so that in it the entire higher Upper Triassic is synonymous with the norium. But since Butler et al. (2007) according to the Eocursor find horizon is only a few meters below the marker horizon, which is considered the Triassic-Jura boundary, it cannot be ruled out that the find horizon is to be placed in the rhaetian according to the chronostratigraphy of the Upper Triassic, which is customary today.

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g ^h Richard J. Butler, Roger MH Smith, David B. Norman : A primitive ornithischian dinosaur from the Late Triassic of South Africa, and the early evolution and diversification of Ornithischia. In: Proceedings of the Royal Society. Series B: Biological Sciences. Vol. 274, No. 1621, 2007, ISSN 0080-4649 , pp. 2041-2046, doi : 10.1098 / rspb.2007.0367 .
↑ Fossil traces deep dinosaur roots. BBC News article dated June 12, 2007.
↑ ^a ^b Data Supplement to: Richard J. Butler, Roger MH Smith, David B. Norman: A primitive ornithischian dinosaur from the Late Triassic of South Africa, and the early evolution and diversification of Ornithischia. In: Proceedings of the Royal Society. Series B: Biological Sciences. Vol. 274, No. 1621, 2007, pp. 2041-2046, online .
↑ Roger MH Smith, James Kitching : Sedimentology and vertebrate taphonomy of the Tritylodon Acme Zone: a reworked palaeosol in the Lower Jurassic Elliot Formation, Karoo Supergroup, South Africa. In: Palaeogeography, Palaeoclimatology, Palaeoecology. Vol. 131, No. 1-2, 1997, ISSN 0031-0182 , pp. 29-50, doi : 10.1016 / S0031-0182 (96) 00143-5 .
^ Paul E. Olsen, Peter M. Galton : A Review of the Reptile and Amphibian Assemblages from the Stormberg of Southern Africa, with Special Emphasis on the Footprints and the Age of the Stormberg. In: Palaeontologia Africana. Vol. 25, 1984, ISSN 0078-8554 , pp. 87-110.

Web links

Commons : Eocursor - collection of images, videos and audio files

Drawing reconstruction of the entire skeleton of Eocursor parvus , made by Scott Hartman.

[butleretal_07-1] ↑ ^a ^b ^c ^d ^e ^f ^g ^h Richard J. Butler, Roger MH Smith, David B. Norman : A primitive ornithischian dinosaur from the Late Triassic of South Africa, and the early evolution and diversification of Ornithischia. In: Proceedings of the Royal Society. Series B: Biological Sciences. Vol. 274, No. 1621, 2007, ISSN 0080-4649 , pp. 2041-2046, doi : 10.1098 / rspb.2007.0367 .

[2] Fossil traces deep dinosaur roots. BBC News article dated June 12, 2007.

[butleretal_07_suppl-3] Data Supplement to: Richard J. Butler, Roger MH Smith, David B. Norman: A primitive ornithischian dinosaur from the Late Triassic of South Africa, and the early evolution and diversification of Ornithischia. In: Proceedings of the Royal Society. Series B: Biological Sciences. Vol. 274, No. 1621, 2007, pp. 2041-2046, online .

[4] Roger MH Smith, James Kitching : Sedimentology and vertebrate taphonomy of the Tritylodon Acme Zone: a reworked palaeosol in the Lower Jurassic Elliot Formation, Karoo Supergroup, South Africa. In: Palaeogeography, Palaeoclimatology, Palaeoecology. Vol. 131, No. 1-2, 1997, ISSN 0031-0182 , pp. 29-50, doi : 10.1016 / S0031-0182 (96) 00143-5 .

[5] Paul E. Olsen, Peter M. Galton : A Review of the Reptile and Amphibian Assemblages from the Stormberg of Southern Africa, with Special Emphasis on the Footprints and the Age of the Stormberg. In: Palaeontologia Africana. Vol. 25, 1984, ISSN 0078-8554 , pp. 87-110.