A new species of Eogruidae (Aves: Gruiformes) from the Miocene of the Linxia Basin, Gansu, China: Evolutionary and climatic implications

AmericanOrnithology.org Volume 137, 2020, pp. 1–13 DOI: 10.1093/auk/ukz067 RESEARCH ARTICLE A new species of Eogruidae (Aves: Gruiformes) from the Miocene of the Linxia Basin, Gansu, China: Evolutionary and climatic implications Grace Musser,1,*, Zhiheng Li,2,3,*, and Julia A. Clarke1, The University of Texas at Austin, The Jackson School of Geosciences, Austin, Texas, USA Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China 3 CAS Center for Excellence in Life and Paleoenvironment, Beijing, China * Corresponding authors: Grace Musser, ; Zhiheng Li, 1 2 ABSTRACT Despite having one of the most robust fossil records within core-gruiform birds (rails, cranes, and allies), the biogeographic history of Gruidae (cranes) and key drivers of diversification within this group remain largely unknown. The Eogruidae of Eurasia represent some of the earliest known crane-like fossils. Here, we present description of a new species represented by a well-preserved specimen of a foot from the late Miocene (7–6.5 mya) Liushu Formation of Linxia Basin, Gansu, China. It is the only eogruid fossil that has been found in this formation and is the first eogruid known from northwest China. Linxia Basin is located along the margin of the northeastern Tibetan Plateau, which allows for new insight into Miocene dispersal of the Eogruidae and potential climatological and geological connections. It is also the first specimen with an associated tarsometatarsus and nearly complete phalanges, including a claw, which provides further morphological information on this taxon. Referral of the new specimen to Eogruidae is based on extreme reduction of the trochlea of metatarsal II, which is most similar to the condition present in the eogruid subclade traditionally termed Ergilornithidae. Keywords: biogeography, China, Eogruidae, evolution, Linxia, morphology, palaeoclimate, Tibetan Plateau Una nueva especie de Eogruidae (Aves, Gruiformes) del Mioceno de la Cuenca de Linxia, Gansu, China: Implicancias evolutivas y climáticas RESUMEN A pesar de tener uno de los registros fósiles más robustos dentro del núcleo de las aves gruiformes (rálidos, grullas y aliados), la historia biogeográfica de Gruidae (grullas) y los factores claves de diversificación dentro de este grupo siguen siendo mayormente desconocidos. Los Eogruidae de Eurasia representan algunos de los primeros fósiles conocidos del tipo de las grullas. Aquí, presentamos la descripción de una nueva especie representada por un espécimen bien preservado de un pie del Mioceno tardío (7–6.5 Ma atrás) de la Formación Liushu de la Cuenca de Linxia, Gansu, China. Este es el único fósil de Eogruidae que ha sido encontrado en esta formación y es el primer Eogruidae conocido del noroeste de China. La Cuenca de Linxia está ubicada a lo largo del margen noreste de la meseta tibetana, lo que brinda una nueva mirada a la dispersión del Mioceno de los Eogruidae y las potenciales conexiones climatológicas y geológicas. También es el primer espécimen con un tarso-metatarso asociado y falanges casi completas, incluyendo una garra, lo que brinda información morfológica adicional de este taxón. La remisión de la nueva especie a Eogruidae está basada en la extrema reducción de la tróclea del metatarsiano II, el cual es más similar a la condición presente en el sub-clado Eogruidae tradicionalmente denominado Ergilornithidae. Palabras clave: biogeografía, China, Eogruidae, evolución, Linxia, meseta tibetana, morfología, paleoclima INTRODUCTION The fossil record of Gruidae (cranes) is one of the most extensive within core-Gruiformes. Gruid fossils have largely been found in northern hemisphere localities (Mayr 2009, 2016a). The biogeographic history, life history, and potential drivers of diversification within extinct gruids remains little understood, and many of these fossils require phylogenetic revision. This is especially true of the Eurasian Eogruidae, a group that contains the oldest crane-like remains after those of the Geranoididae from the early-middle Eocene of Wyoming (Wetmore 1933, Cracraft 1969, 1973; Clarke et al. 2005, Mayr 2009). The only phylogenetic study of Eogruidae (Clarke et al. 2005) recovered Eogrus aeola (Wetmore 1934) within an unresolved group containing Psophiidae and Gruidae using a modified dataset (Mayr and Clarke 2003). Results also placed an eogruid-like specimen (IGM 100/1447) as the sister taxon of an Aramidae Copyright © American Ornithological Society 2019. All rights reserved. For permissions, e-mail: . Submission Date: June 29, 2019; Editorial Acceptance Date: October 11, 2019; Published November 28, 2019 2 New species of Eogruidae—Linxia Basin, Gansu, China several tibiotarsi have also been referred to the taxon (Wetmore 1934, Kurochkin 1976, 1981; Clarke et al. 2005). Remains of the Late Eocene–early Oligocene Sonogrus gregalis (Khoer-Dzan; Kurochkin 1981) were also recovered in Mongolia. Late Eocene to early Pliocene taxa that were historically placed within Ergilornithidae have been recovered as far east as Mongolia and as far west as the Balkan Peninsula (Kurochkin 1981, Zelenkov et al. 2016; see Table 1). Four genera were originally named: Proergilornis (Kozlova 1960), Ergilornis (Kozlova 1960), Urmiornis (Mecquenem 1908), and Amphipelargus (Lydekker 1891). Today 3 genera are recognized: Ergilornis, Amphipelargus, and Urmiornis, with Proergilornis and Ergilornis being synonymized (Kurochkin 1981). The Paleogene ergilornithid record comprises several unknown species of Ergilornis from the late Eocene–early Oligocene of southeastern Mongolia (Ergilin Dzo and Khoer-Dzan; Zelenkov and Kurochkin 2011, 2015) and the late Eocene of eastern Kazakhstan (Kustovskaya svita; Kozlova 1960, Kurochkin 1981). The Neogene record of these taxa currently consists of Urmiornis brodkorbi from the early Miocene of western Kazakhstan (Mynsualmas and Altynshokysu; Karhu 1997); Ergilornis sp. from the late Middle Miocene of western Mongolia (Sharga; Zelenkov FIGURE 1. Distribution of the Eogruidae. A star denotes the Linxia Basin, where the new eogruid was found. Empty circles denote Eocene specimens, filled circles denote Oligocene taxa, daggers denote Miocene taxa, and an X denotes Pliocene taxa. Numbers correspond to the names of taxa as follows: (1) Sonogrus gregalis (SE Mongolia); (2) Eogrus sp. (SE Mongolia); (3) IGM100.1447 (Mongolia); (4) E. aeola (NE China); (5) E. wetmorei (NE China); (6) E. crudus (Mongolia); (7) Sinoergilornis guangheensis (N China); (8) Eogrus turanicus (E Kazakhstan); (9) Ergilornis spp. (SE Mongolia); (10) Ergilornis sp. (E Kazakhstan); (11) Urmiornis brodkorbi (W Kazakhstan); (12) U. brodkorbi (W Kazakhstan); (13) ?Ergilornis sp. (W Mongolia); (14) ?U. cracrafti (N Pakistan); (15) U. sp. (N Kazakhstan); (16) U. orientalis (E Kazakhstan); (17) U. maraghanus (N Iran); (18) U. ukrainus (S Moldova); (19 (...truncated)