Chin. Sci. Bull. csb.scichina.com DOI 10.1007/s11434-014-0669-8 www.springer.com/scp Article Geology A new species from an ornithuromorph (Aves: Ornithothoraces) dominated locality of the Jehol Biota Shuang Zhou • Jingmai K. O’Connor • Min Wang Received: 10 July 2014 / Accepted: 16 September 2014 Ó Science China Press and Springer-Verlag Berlin Heidelberg 2014 Abstract We report on a new species of ornithuromorph 1 Introduction bird, Iteravis huchzermeyeri gen. et sp. nov., from the previously unreported Sihedang locality of the Lower The Early Cretaceous Jehol Biota in Northeastern China Cretaceous Yixian Formation, the oldest ornithuromorph comprises the most important avifauna in the world, con- bearing deposit in the world. Unlike most other Cretaceous taining the earliest members of every clade of Cretaceous localities, specimens from this new quarry are largely bird including the oldest member of Ornithuromorpha, the referable to Ornithuromorpha, similar to the Lower Cre- derived clade of birds that includes living birds (Neornithes) taceous Aptian Xiagou Formation in Gansu Province. Also [1]. Traditionally, Cretaceous avifaunas are dominated by similar to the Xiagou avifauna, the fauna at Sihedang is Enantiornithes, the sister taxon to Ornithuromorpha and largely dominated by a single taxon (described here). often considered the first major avian radiation [2]. However, Differences in faunal dominance may suggest the Sihedang this successful clade succumbed with other non-neornithine records a unique ecological habitat. This may also explain dinosaurs at the end of the Cretaceous; the underlying causes the dominance of Gansus in the younger Xiagou Formation of their extinction and whether their demise was sudden or locality and suggests that previous hypotheses regarding gradual are unclear. Until now, known localities in the Jehol the shift in dominance between Enantiornithes and Orni- Biota have either been dominated by enantiornithines (not thuromorpha need to be reassessed in terms of potential any one taxa) or Confuciusornis, a beaked basal pygostylian ecological biases due to limited sampling. Furthermore, the bird apparently endemic to the Jehol and the single most recognition of an ornithuromorph dominated locality in the abundant taxon in the avifauna [3, 4]. In contrast, the only Sihedang significantly weakens the signal of such an other avian bearing Early Cretaceous deposits in China, the inferred trend. Compared to most Jehol birds, the new slightly younger Xiagou Formation in Gansu Province, is specimen is relatively better preserved in three dimensions dominated by ornithuromorph specimens largely assignable revealing morphological details of the skeleton, as well as to a single taxon, Gansus yumenensis [5, 6]. Because the preserves feather impressions including a rectricial mor- Xiagou Formation is younger than the Yixian formation, it phology previously unknown among Mesozoic birds. has been suggested that the Xiagou records the shift from enantiornithine to ornithuromorph dominance [7]. Keywords Early Cretaceous Á Sihedang Á The Yixian Formation (125 Ma) records the second Ornithuromorpha Á Aves Á Tail feathers phase of the Jehol Biota and the first appearance datum (FAD) of Ornithuromorpha. Enantiornithes first appears in the slightly older Huajiying Formation (alternatively referred to as the Dabeigou Formation in some early lit- S. Zhou Á J. K. O’Connor (&) Á M. Wang erature), the first phase of the Jehol Biota (130.7 Ma) [8]. Key Laboratory of Vertebrate Evolution and Human Origins The younger Jiufotang Formation (120 Ma) preserves a of Chinese Academy of Sciences, Institute of Vertebrate greater diversity of ornithuromorph taxa compared to the Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China Yixian Formation, although still less than that recognized e-mail: [email protected] for Enantiornithes [1]. The new locality, Sihedang, belongs 123 Chin. Sci. Bull. to the Yixian Formation; located near Lingyuan, western 3 Description Liaoning, this locality has already produced hundreds of turtles and more recently approximately 20 orni- 3.1 Skull thuromorphs, as well as one caudipteryid (Maniraptora: Oviraptorosauria); however, not a single enantiornithine Although the skull is largely complete, preserved in left has yet to be collected (Zhou Z. pers. comm.). Most of the lateral view, overlap of the thin bones from both sides of new ornithuromorphs appear to represent a single new the skull make it difficult to identify some structures and taxon, which we describe here. We investigate this new interpret their details, especially in the caudal region specimen through phylogenetic analysis and discuss the (Fig. 2). The premaxilla appears toothless; the lateral sur- implications of this new locality in regards to earlier face is marked by small but well-defined nutrient foramina. interpretations concerning avifaunal shifts in the The shallow premaxillary corpus is elongate, three times Cretaceous. longer than it is dorsoventrally high, although it is still fairly rostrally restricted contributing to only the rostral third of the facial margin. The rostral margin is gently 2 Systematic paleontology rounded, and the nasal and maxillary processes are nearly parallel. The nasal (frontal) processes are elongate; they are Aves Linnaeus 1758 unfused along most of their length, and the left process is Ornithothoraces Chiappe 1995 missing the caudal half. The distal eighth of the right Ornithuromorpha Chiappe 2002 process is broken and slightly displaced, but we infer they Iteravis huchzermeyeri gen. et sp. nov. would have articulated with the frontals. Just ventral to the distal quarter of this process, a short, broad sheet of bone Holotype IVPP V18958, a nearly complete, articulated ventral may represent the left nasal. The straight maxilla is specimen with feather impressions preserved in a single slightly displaced dorsally; although this element is not slab in dorsolateral view (Fig. 1). well preserved, several teeth are visible intercalating with the dentary teeth. We infer the last maxillary tooth was Locality and horizon Sihedang locality, near Lingyuan, level with the rostral margin of the antorbital fossa. The western Liaoning Province, China; Lower Cretaceous premaxillary ramus of the maxilla is approximately twice Yixian Formation [9]. the length of the jugal ramus, forming the ventral margin of Etymology The name Iteravis (Latin iter—meaning elongate nares. The nasal process is incomplete, but the journey, avis—meaning bird) huchzermeyeri meaning well preserved rostral margin indicates that it would have Huchzermeyer’s journey bird is in honor of the late formed the caudal margin of the external nares. A large archosaur biologist, Dr. Fritz Huchzermeyer, and his end- sheet of bone visible through the external nares appears to less quest for knowledge. be the palatal shelf of the maxilla or the palatine. The exposed ‘dorsal’ surface is concave and appears to be Diagnosis An ornithuromorph bird (predentary bone continuous with the premaxillary ramus of the maxilla present, delicate U-shaped furcula, first phalanx of the supporting the former interpretation. Between the concave major digit expanded, short plow-shaped pygostyle) with palatal shelf and the lateral surface of the premaxillary the unique combination of the following features: pre- ramus, there is located a shallow and caudally tapered maxillary corpus elongate and toothless; maxilla with groove that we infer is for the articulation of the premax- numerous teeth; rostrum 50 % of skull length; ethmoid illa. The region of the antorbital fenestra is not clear, and bone lining rostral half of the orbit; tubercle on caudal the lacrimal bone cannot be clearly identified; however, it margin of minor digit phalanx; pubes with dorsally appears the antorbital fenestra was short, similar to that of expanded distal boot; and narrow ischium with concave Confuciusornis. A very broad and sheet-like bone located ventral margin and weak dorsal process at midpoint. in the rostral third of the orbit and apparently rostrally in Ontogenetic remarks The well ossified periosteal sur- contact with the frontal appears to be an ethmoid bone faces of all the preserved elements and the complete fusion forming a rostrally enclosed interorbital septum. Alterna- of the tibiotarsus and tarsometatarsus indicate that growth tively, this may represent the lacrimal, in which case it was nearly complete, thus the specimen does not represent would represent a very strange hypertrophied and autapo- a juvenile; however, apparent incomplete fusion of the morphic morphology. A trend toward decreasing lacrimal pygostyle, proximal carpometacarpus, and caudal midline size in more derived ornithuromorphs (absent in Neorni- of the sternum indicate that IVPP V18958 was not fully thes) supports interpretations of this bone as the ethmoid. mature. We consider this specimen to represent a near adult The lateral surface bears a slight ridge that extends cau- subadult. dodorsal–cranioventrally (Fig. 2). The jugal is not well 123 Chin. Sci. Bull. preserved, partially obscured by scleral ossicles; it appears The thoracic vertebrae are poorly preserved, obscured to be fairly thin, slightly bowed, and tapered rostrally. The by overlap with other elements (Fig. 1). They are slightly dentary clearly preserves numerous teeth located in indi- shorter than the cervicals, with broad fossae excavating vidual sockets, not a communal row as in Hesperornithi- their lateral