Chapter 2 The Fossil Record of Mesozoic and Paleocene Pennaraptorans MICHAEL PITTMAN,1 JINGMAI O’CONNOR,2 EDISON TSE,1 PETER MAKOVICKY,3 DANIEL J. FIELD,4 WAISUM MA,5 ALAN H. TURNER,6 MARK A. NORELL,7 RUI PEI,2 AND XING XU2 ABSTRACT An unabated surge of new and important discoveries continues to transform knowledge of pen- naraptoran biology and evolution amassed over the last 150+ years. This chapter summarizes prog- ress made thus far in sampling the pennaraptoran fossil record of the Mesozoic and Paleocene and proposes priority areas of attention moving forward. Oviraptorosaurians are bizarre, nonparavian pennaraptorans first discovered in North America and Mongolia within Late Cretaceous rocks in the early 20th century. We now know that oviraptorosaurians also occupied the Early Cretaceous and their unquestionable fossil record is currently limited to Laurasia. Early Cretaceous material from China preserves feathers and other soft tissues and ingested remains including gastroliths and other stomach contents, while brooding specimens and age-structured, single- species accumulations from China and Mongolia provide spectacular behavioral insights. Less specialized early oviraptorosaurians like Incisivosaurus and Microvenator remain rare, and ancestral forms expected in the Late Jurassic are yet to be discovered, although some authors have suggested Epidexipteryx and possibly other scansoriopterygids may represent early-diverging oviraptorosaurians. Long-armed scansoriopterygids from the Middle-Late Jurassic of Laurasia are either early-diverg- ing oviraptorosaurians or paravians, and some have considered them to be early-diverging avialans. Known from five (or possibly six) feathered specimens from China, only two mature individuals exist, representing these taxa. These taxa,Yi and Ambopteryx, preserve stylopod-supported wing membranes that are the only known alternative to the feathered, muscular wings that had been exclusively associated with dinosaurian flight. Thus, scansoriopterygid specimens—particularly those preserving soft tissue—remain a key priority for future specimen collection. Dromaeosaurids and troodontids were first discovered in North America and Mongolia in Late Cretaceous rocks. More recent discoveries show that these animals originated in the Late Jurassic, were strikingly feathered, lived across diverse climes and environments, and at least in the case of dromaeosaurids, attained a global distribution and the potential for aerial locomotion at small size. 1 Vertebrate Palaeontology Laboratory, Division of Earth and Planetary Science, the University of Hong Kong, Hong Kong. 2 Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology & Paleoanthropology, Beijing; and CAS Center for Excellence in Life and Paleoenvironment, Beijing. 3 Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN. 4 Department of Earth Sciences, University of Cambridge, Cambridge. 5 School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, U.K. 6 Department of Anatomical Sciences, Stony Brook University, Stony Brook, NY. 7 Division of Paleontology, American Museum of Natural History, New York. 38 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 440 China and Mongolia have yielded the most dromaeosaurid and troodontid specimens and taxa, but Gondwanan troodontids are almost unknown compared to southern dromaeosaurids, so the fidelity of this biogeographical signal is worth further exploration. Discovery of well-preserved Middle-Late Jurassic material will be crucial for understanding the origin of key dromaeosaurid and troodontid traits, with the controversial anchiornithines potentially already offering this if their troodontid status can be solidified. In line with the preferences of most theropod palaeontologists, birds are defined herein as mem- bers of Avialae, including stem and crown taxa, whilst Aves herein refers to crown-group birds (see Pittman et al., chapter 1, for the precise definition of Avialae adopted; elsewhere, typically among ornithologists, Aves refers to stem and crown taxa whilst Neornithes refers to crown-group birds). Despite taphonomic bias against avialans in the fossil record, their Early Cretaceous record is fairly robust largely due to the high taxonomic and ecological diversity preserved within the rich Jehol deposits of northeastern China. Archaeopteryx (and possibly the controversial Middle-Late Jurassic anchiornithines) show what some of the earliest birds were like, but better-preserved soft tissues hold the key to understanding their substantially different anatomy and flight capabilities to crown- group birds (Aves). The Late Cretaceous–early Paleocene fossil record of crown birds is especially poor, and improved sampling will be necessary to clarify our understanding of avialan survivorship, ecological selectivity, and recovery across the end-Cretaceous mass extinction. Deposits of Eocene age, such as Messel and Green River, have been especially useful for documenting the early evolutionary history of crown birds. However, the discovery of new Cretaceous and/or Palaeogene bird-bearing lagerstätten from Gondwana will be important for accurately determining ancestral biogeographic patterns. BACKGROUND is limited to Laurasian continents and dominated by discoveries from Asia and North America (fig. Pennaraptorans are a clade of vaned feathered 1). The last 30 years have seen the discovery of coelurosaurian dinosaurs that are comprised of most known oviraptorosaurian taxa, particularly the Oviraptorosauria, Scansoriopterygidae, from the Cretaceous of China and the Late Cre- Dromaeosauridae, Troodontidae, and Avialae taceous of North America and Mongolia. These (see Pittman et al., in the previous chapter for discoveries have greatly broadened our under- additional information). They include the only standing of this group, including in regard to the dinosaurs to have evolved flight and the only evolution of their beaked and strangely pneuma- ones to have persisted to the present day. tized skulls, as well as the origin of brooding in theropod dinosaurs. Asia: This continent is the home of the first Oviraptorosauria described oviraptorosaurian species (Osborn, Oviraptorosaurian fossils were first discov- 1924), the eponymous species Oviraptor. Asia is ered in the 1920s and are now represented by also home to more than 75% of valid oviraptoro- more than 40 genera spanning a size range across saurian genera. The most important sources of three orders of magnitude (table 1). The 1920s to Asian oviraptorosaurians are the Early Creta- 1940s, the 1970s, 1980s, 1990s, and the past 20 ceous (Hauterivian-Aptian) Jehol Lagerstätte of years have been key periods in our documenta- northeastern China, the Campanian-Maastrich- tion of the oviraptorosaurian fossil record, which tian Ganzhou oviraptorid fauna of southern 2020 PITTMAN ET AL.: THE FOSSIL RECORD 39 FIG. 1. Geographic distribution of pennaraptoran theropods illustrated on palaeogeographic globes of the Late Jurassic (Oxfordian-Tithonian), Early Cretaceous (Berriasian-Albian), and Late Cretaceous (Cenoma- nian-Maastrichtian). Palaeomaps modified from GPlates (www.gplates.org) (Müller et al., 2018). 40 TABLE 1 Oviraptorosaurian fossil record Geological Continent Country Period Age Age Reference Taxa Reference Unit Jehol Group Incisivosaurus, Caudipteryx, Ji and Ji, 1997; Ji et al., 1998; 2012; (Yixian Ningyuansaurus, Protarchaeop- Early Barremian- Chang et al., 2009, 2017; Zhou et al., 2000; Xu et al., 2002a, Asia Formation; China teryx, Similicaudipteryx (possibly Cretaceous Aptian Pan et al., 2013 2010a; He et al., 2008; Balanoff et Jiufotang Incisivosaurus), Xingtianosaurus; HISTORY NATURAL OF MUSEUM AMERICAN BULLETIN al., 2009; Qiu et al., 2019 Formation) Similicaudipteryx Bureau of Geology and Banji, Corythoraptor, Xu and Han, 2010; Lü et al., 2013a; Nanxiong Late Campanian- Mineral Ganzhousaurus, Huanansaurus, China Wang et al., 2013a; Wei et al., Formation Cretaceous Maastrichtian Resources of Jiangxi Jiangxisaurus, Nankangia, 2013; Lü et al., 2015, 2016, 2017 Province, 1984 Tongtianlong Haoling Early China Aptian/Albian Xu et al., 2012a Luoyanggia Lü et al., 2009 Formation Cretaceous Bureau of Geology and Dalangshan Late Mineral Resources of China Maastrichtian Heyuannia Lü, 2003 Formation Cretaceous Guangdong Province, 1988 Pingling Late China Maastrichtian Zhao et al., 1991 Shixinggia Lü and Zhang, 2005 Formation Cretaceous Qiupa Late Campanian- China Jiang et al., 2011 Yulong Lü et al., 2013b Formation Cretaceous Maastrichtian Gaogou Late Cenomanian- China Liang et al., 2009 Beibeilong Pu et al., 2017 Formation Cretaceous Turonian Erlian van Itterbeeck et al., Late Campanian- Avimimus, Caenagnathasia, Kurzanov, 1981; Xu et al., 2007; (Iren Dabasu) China 2005; Bonnetti et al., Cretaceous Maastrichtian Gigantoraptor Yao et al., 2015; Ma et al., 2017 Formation 2014 Wulansuhai (Bayan Late Longrich et al., 2010; Xu et al., China Campanian Godefroit et al., 2008 Machairasaurus, Wulatelong Mandahu) Cretaceous 2013b Formation Wangshi Late China Campanian An et al., 2016 Anomalipes Yu et al., 2018 Group Cretaceous van Itterbeeck et al., Osborn, 1924; Kurzanov, 1981; 440 NO. Djadokhta Late 2005; Dingus et al., Avimimus, Citipati, Khaan, Mongolia Campanian Clark et al., 2001; Clark et al., Formation Cretaceous 2008; Hasegawa et al., Oviraptor 2002; Balanoff and Norell, 2012 2009 TABLE 1 continued 2020 Geological Continent Country Period Age