Overoraptor chimentoi gen. et sp. nov. (1 Viewer)

Matías J. Motta, Federico L. Agnolín, Federico Brissón Egli & Fernando E. Novas, 2020

New theropod dinosaur from the Upper Cretaceous of Patagonia sheds light on the paravian radiation in Gondwana

The Science of Nature. 107 (3): Article number 24.
doi:10.1007/s00114-020-01682-1

Abstract: https://link.springer.com/article/10.1007/s00114-020-01682-1

The fossil record of basal paravians in Gondwana is still poorly known, being limited to the Cretaceous unenlagiids from South America and the problematic Rahonavis from Madagascar. Here we report on a new paravian from the Cenomanian-Turonian (Late Cretaceous) of Río Negro province, NW Patagonia, Argentina. The new taxon exhibits a derived bird-like morphology of the forelimbs (e.g., robust ulna with prominent, anteriorly oriented, and proximally saddle-shaped radial cotyle and wide medial flange on metacarpal I) and a plesiomorphic foot with a raptorial pedal digit II. Phylogenetic analysis recovers the new taxon in a monophyletic clade with Rahonavis, being the sister group of the remaining Avialae and more derived than other non-avian dinosaurs. Both exhibit derived forelimb traits in opposition with their plesiomorphic hind limbs. The position of the new taxon and Rahonavis as stem avialans indicates that Gondwanan basal paravians are represented by two different clades, at least. The new taxon probably constitutes a previously unknown grade in the avian-line theropods in which some flight-related adaptations of the forelimbs are present in cursorial taxa. The present discovery sheds light on the acquisition of flight-related traits in non-avian dinosaurs and on the still poorly known paravian radiation in Gondwana.

Overoraptor chimentoi gen. et sp. nov. is described.

Enjoy,

Fred

Introducing Overoraptor, a new theropod dinosaur from the Upper Cretaceous of Patagonia

https://paleonerdish.wordpress.com/...osaur-from-the-upper-cretaceous-of-patagonia/

Fred

Free pdf: https://www.researchgate.net/public...s_light_on_the_paravian_radiation_in_Gondwana

Fred

Is this journal still published in print ?
(At https://www.springer.com/journal/114 , we are told "Frequency: Bimonthly in print.", but subscription to a printed version does not seem possible.)

Systematic paleontology

DINOSAURIA Owen, 1842
SAURISCHIA Seeley, 1888
THEROPODA Marsh, 1881
MANIRAPTORA Gauthier, 1986
PARAVES Sereno, 1997
Overoraptor chimentoi gen. et sp. nov.

Holotype MPCA-Pv 805, incomplete and disarticulated specimen including four caudal vertebrae, two hemal arches, right scapula, right ulna, elements of right hand (metacarpal I, phalanx I-1, and unguals of digits I and II), fragment of right ilium, incomplete left pubis, right and left metatarsals II and III, and elements of left foot (phalanges I-1 and II-2 and unguals of digits I and II)

Paratype MPCA-Pv 818, fragmentary specimen, 20% smaller than the holotype (see Supplementary Material 1), represented by right manual phalanges I-1 and III-2, fragment of left ilium, nearly complete right pubis, right metatarsal II, left pedal phalanx II-1, and right pedal phalanx III-1. This individual is very similar to the holotype specimen in most anatomical traits (see “Description and comparisons”) and in the notably gracile proportions of the metatarsals and the pedal and manual phalanges.
The holotype and paratype specimens of O. chimentoi were found in a quarry measuring 1.5 m in diameter and 0.30 m in depth. They were found in association with disarticulated crocodilian and turtle bones. Some of these elements were previously reported as belonging to Unenlagiidae (Motta et al. 2016).

Etymology Overo from “overo” the Spanish word meaning piebald, in reference to the coloration of the O. chimentoi bones, which consists of a pattern of light and dark spots, and raptor from the Latin for thief. The species name chimentoi honors its discoverer, the paleontologist Dr. Roberto Nicolás Chimento.

Diagnosis The new taxon differs from other paravians in the following combination of characters (autapomorphies are marked by an asterisk): posterior caudal centra with a complex system of lateral longitudinal ridges and concavities (also present in Buitreraptor and Rahonavis); scapula with a medially deflected distal end*; acromial process reduced and ridge-like*; robust ulna; radial cotyle of ulna saddle-shaped and prominent; metacarpal I with extensive medioventral crest*; metatarsal II with longitudinal lateroventral crest on distal half, ending distally in a posterior tubercle* (present on both specimens); metatarsal III distal end non-ginglymoidal (also present in Pamparaptor); metatarsal III distal end dorsoventrally deeper than transversely wide*; and strongly dorsally displaced collateral pits on pedal phalanx II-2.

Locality and horizon The specimen comes from beds of the Huincul Formation (middle Cenomanian-early Turonian; Garrido 2010), cropping out at 39°23′52.37″ S, 68°37′4.30″ W, southeast of the Ezequiel Ramos-Mexía lake, NW Río Negro province, Argentina (the fossil locality is historically known as “Violante farm”). These beds have yielded remains of different theropod clades, including Carcharodontosauridae (i.e.,
Mapusaurus rosae and Taurovenator violantei) (Coria and Currie 2006; Motta et al. 2016), Abelisauridae (i.e., Ilokelesia aguadagrandensis, Skorpiovenator bustingorryi, Huinculsaurus montesi, and Tralkasaurus cuyi) (Coria and Salgado 1998, Canale et al. 2009, Baiano et al. 2020, Cerroni et al. 2020), and Megaraptora (i.e., Gualicho shinyae and Aoniraptor libertatem) (Apesteguía et al. 2016, Motta et al. 2016).

Fred

Fig. 1 Silhouette of Overoraptor chimentoi gen. et sp. nov. (MPCA-Pv 805) showing selected skeletal elements. (a) Pelvic girdle elements including fragments of ilium in lateral (top) view and left pubis in medial (left) view, (b) right scapula in dorsal (top) and lateral (bottom) views, (c) mid-caudal vertebra in left lateral view, (d) right ulna in lateral (bottom) and proximal (top) views, (e) right metacarpal I in dorsal (top), medial, ventral, and distal (bottom) views, ( f ) right manual phalanx I-1 and manual ungual of digit I in medial view, (g) left pedal phalanx II-2 and left pedal ungual of digit II in medial view, (h) left metatarsal II in lateral (left), dorsal (right), and distal (bottom) views, (i) left pedal phalanx I-1 and pedal ungual of digit I in medial view, (j) left metatarsal III in dorsal (right), lateral (left) and distal (bottom) views. Abbreviations: a anterior, acr acromion, cg collateral groove, cp collateral pit, ft flexor tubercle, gf glenoid fossa, ip ischium pedicle of ilium, l lateral, lc lateral crest, lr lateral ridge, lvc lateroventral crest, ldc laterodorsal crest, mvc medioventral crest, rp radial process of ulna, sra surface for radial articulation, tc bump representing the m. tibialis cranialis insertion, tsb tapered scapular blade, pa pubic apron, pr protuberance, pt proximal tubercle, vh ventral heel. Scale bar equals 50 cm in the silhouette; 4 cm in a, b, d, h, and j; and 2 cm in c, e, f, g, and i.