Yatenavis ieujensis gen. et sp. nov. (1 Viewer)

[Fred Ruhe]

Gerarso Alvarez Herrera, Federico Agnolin, Sebastian Rozadilla, Gaston E. Lo Coco, Makoto Manabe, Takanobu Tsuihiji & Fernando E. Novas, 2022

New enantiornithine bird from the the uppermost Cretaceous (Maastrichtian) of southern Patagonia, Argentina

Cretaceous Research: 105452.
doi:10.1016/j.cretres.2022.105452. ISSN 0195-6671

Abstract: New enantiornithine bird from the the uppermost Cretaceous (Maastrichtian) of southern Patagonia, Argentina

Enantiornithes were the dominant avialan clade in the Mesozoic. However, their record for the Upper Cretaceous is scarce. In this study, we present and describe Yatenavis ieujensis gen. et sp. nov., one of the youngest occurence of an enantiornithine bird. The specimen, the distal half of a right humerus, was found in Chorrillo Formation, southern Santa Cruz Province of Argentina, making it also the australmost enantiornithine specimen recorded to date. Yatenavis is unique among enantiornithines for its combination of characters, including a crest on the medial side of the shaft which bears a muscular scar cranially; the presence of a dorsal supracondylar process proximal to the dorsal epicondyle; equally distally projected dorsal and ventral condyles; and a rod-like caudal extension of the ventral condyle bearing a distal sulcus scapulotricipitalis. Several of these features are shared with an unnamed enantiornithine recovered from Upper Cretaceous beds in another fossil site in Patagonia.

Enjoy,

Fred

 

[Fred Ruhe]

Systematic paleontology

Avialae Gauthier, 1986
Enantiornithes Walker, 1981
Yatenavis ieujensis gen. et sp. nov.
urn:lsid:zoobank.orgub:448797D5-B25E-44FB-9830-74B6B1185D0A

Holotype.

MPM-PV-23086, distal end/half of a right humerus, with flexor process slightly eroded.

Diagnosis.

A sparrow-sized enantiornithine that is distinguishable from other enantiornithines on basis of the unique combination of following characters: 1) humeral shaft narrow (less than half of the maximum width of the distal end of the humerus) and slightly bowed cranio-caudally; 2) dorsal supracondylar process prominent and slightly concave; 3) m. brachialis fossa wide, deep and proximally extended; medially positioned and laterally delimited by a ridge; 4) presence of a well-defined fossa proximal to the distal condyles, and dorsally separated from the m. brachialis fossa through a wide and prominent ridge; 5) presence of a craniocaudal ridge along the distal margin of the ventral condyle; 6) a D-shaped distal fossa delimited laterally by the ridge of the ventral condyle and separated from the olecranal fossa and 7) distal end of humerus almost perpendicular to the longitudinal axis of the bone.
Characters 2 and 5 are shared with Alexornis, Kizylkumavis, Martinavis, and the unnamed enantiornithine from La Colonia Formation (Lawver et al., 2011) and Madagascar (O´Connor and Forster, 2010). A well-defined dorsal supracondylar process also appears to be present in Eocathayornis (Zhou, 2002) and Cathatyornis (Zhou et al., 1992). Character 3 is shared only with an unnamed enantiornithine from La Colonia Formation (Lawver et al., 2011).

Etymology.

Yaten is the Aoni Kenk word for “stone”; avis means “bird” in Latin, and ieuj means “snow” in the Aoni Kenk language.

Locality and Horizon.

The specimen comes from the outcrop of the Chorrillo Formation (lower Maastrichtian; Moyano Paz et al., 2021) at Estancia La Anita, 30 km south to El Calafate City, southwest of Santa Cruz Province in Argentinian Patagonia (Fig. 1). The specific GPS point is S 50°31'07.7" W 72°33'50.7". The Chorrillo Formation is principally composed of intercalated fine-grained sandstones interpreted as having accumulated in a fluvial depositional system (Novas et al., 2019; Moyano-Paz et al., 2022). The particular site is a small spot (approximately 10 x 20 m) which also yielded several minute and disarticulated fossil remains of terrestrial gastropods, fishes, frogs, mammals, snakes, turtles, a sphenodont, small non-avialan dinosaurs and the present enantiornithine. This spot is stratigraphically comparable to the level of the “Puma cave site” described in Novas et al. (2019) and also similar in the preservation mode and fossil assemblages to the latter. These sites are horizontally separated by approximately 500 m from each other and both represent the middle portion of the Chorrillo Formation.

Fred


Figure 1. Right humerus of Yatenavis ieujensis gen. et sp. nov. Right humerus (MPM-PV-23086; holotype) in cranial (A), caudal (B), ventral (C) and dorsal (D) views, and details of the distal end in cranial (E) and distal (F) views. Abbreviations: bf, brachial fossa; br, brachial ridge; cf, crescentic fossa; cr, caudal ridge; dc, dorsal condyle; df, distal fossa; dsp, dorsal supracondylar process; ds, dorsal scar; ecrs, m. extensor carpi radialis scar; ect, ectepicondyle; ent, entepicondyle; ig, intercondylar groove; lip, lip of the dorsal condyle; of, olecranal fossa; vc, ventral condyle; vr, ventral ridge.