Monday, May 1, 2017

[PaleoOrnithology • 2017] An Ichthyornis-like bird from the earliest Late Cretaceous (Cenomanian) of European Russia

An Ichthyornis-like bird from the earliest Late Cretaceous (Cenomanian) of European Russia. 
Zelenkov, Averianov & Popov, 2017   Illustration: Andrey Atuchin 

Ornithuromorph birds (the clade which includes modern avian radiation) first appeared in the Early Cretaceous in Asia and achieved a great diversity during the latest ages of the Late Cretaceous (Campanian and Maastrichtian). The evolutionary history of orithuromorphs during the first 17 MYAs of the Late Cretaceous (Cenomanian to Santonian ages) remains very poorly known, as the fossil record for this time interval is largely restricted to several isolated finds of the classic avian genus Ichthyornis in North America. Here we describe an isolated distal tibiotarsus of an evolutionary advanced bird, morphologically similar to Ichthyornis, from the middle Cenomanian of Saratov Province, European Russia. This is the first documentation of an Ichthyornis-like bird in the Old World. The find further constitutes only the second pre-Campanian record of the Late Cretaceous Ornithuromorpha in Eurasia, the second record of Cenomanian birds in Russia. This discovery shows that Ichthyornis-like birds enjoyed a wide geographical distribution as early as the beginning of the Late Cretaceous. Given that the earliest and the most primitive ornithuromorph birds are known from Asia, the new find supports a Eurasian origin for Ichthyornithidae.

Keywords: Cenomanian; East Europe; Ornithuromorpha; Palaeobiogeography

Systematic paleontology
Aves Linnaeus 1758
Ornithuromorpha Chiappe et al. 1999
Ornithurae Haeckel 1866
?Ichthyornithidae Marsh 1873

Gen. et sp. indet.

Material. Specimen PIN 5554/1, distal fragment of a right tibiotarsus.

Locality and horizon. Site SNB-2a, Nizhnyaya Bannovka, Krasnoarmeisk District, Saratov Province, Russia; Middle Member, Melovatka Formation, middle Cenomanian, lower Upper Cretaceous.

Fig. 2. Specimen PIN 5554/1, distal tibiotarsus of an Ichthyornis-like bird from the middle Cenomanian of European Russia. A, lateral view; B, cranial view; C, medial view; D, caudal view; E, proximal view; F, distal view; G, interpretative drawing of the cranial view.
Abbreviations: cl, condylus lateralis; cm, condylus medialis; conc, concavity; csic, concavities within sulcus intercondylaris; ?dep, depression; em, epicondylus medialis; sic, sulcus intercondylaris; se, sulcus extensorius; tub, tuberosity. 

A partial tibiotarsus from the middle Cenomanian of the Nizhnyaya Bannovka locality in Saratov Province (European Russia) belongs to an evolutionary advanced ornithuromorph bird, similar in size and morphology to the North American Ichthyornis. This is the first reliable documentation of Ichthyornis-like birds in the Old World, because previously referred specimens indeed belong to Enantiornithes. This discovery confirms a wide geographic distribution of Ichthyornis-like birds already in the beginning of the Late Cretaceous and supports the Eurasian origin of Ichthyornithidae. The new specimen is further the first pre-Campanian Late Cretaceous ornithuromorph bird in Eurasian known from postcranial material.

Nikita V. Zelenkov, Alexander O. Averianov and Evgeny V. Popov. 2017. An Ichthyornis-like bird from the earliest Late Cretaceous (Cenomanian) of European Russia.
Cretaceous Research. 75; 94–100. DOI: 10.1016/j.cretres.2017.03.011

Поволжский ихтиорнис • Никита Зеленков • Научная картинка дня на «Элементах» • Палеонтология