A new caenagnathid dinosaur from the Upper Cretaceous Wangshi Group of Shandong, China, with comments on size variation among oviraptorosaurs

Abstract

The bone-beds of the Upper Cretaceous Wangshi Group in Zhucheng, Shandong, China are rich in fossil remains of the gigantic hadrosaurid Shantungosaurus. Here we report a new oviraptorosaur, Anomalipes zhaoi gen. et sp. nov., based on a recently collected specimen comprising a partial left hindlimb from the Kugou Locality in Zhucheng. This specimen’s systematic position was assessed by three numerical cladistic analyses based on recently published theropod phylogenetic datasets, with the inclusion of several new characters. Anomalipes zhaoi differs from other known caenagnathids in having a unique combination of features: femoral head anteroposteriorly narrow and with significant posterior orientation; accessory trochanter low and confluent with lesser trochanter; lateral ridge present on femoral lateral surface; weak fourth trochanter present; metatarsal III with triangular proximal articular surface, prominent anterior flange near proximal end, highly asymmetrical hemicondyles, and longitudinal groove on distal articular surface; and ungual of pedal digit II with lateral collateral groove deeper and more dorsally located than medial groove. The holotype of Anomalipes zhaoi is smaller than is typical for Caenagnathidae but larger than is typical for the other major oviraptorosaurian subclade, Oviraptoridae. Size comparisons among oviraptorisaurians show that the Caenagnathidae vary much more widely in size than the Oviraptoridae.

The skull evolution of oviraptorosaurian dinosaurs: the role of niche partitioning in diversification

“…The lower beak form morphospace also displays a similar pattern, with most caenagnathids and oviraptorids situated at the opposing sides and basal oviraptorosaurs located between them on PC1. However, in both morphospaces, Gigantoraptor is located closer to oviraptorids than other caenagnathids and even basal oviraptorosaurs on PC1, despite phylogenetic studies consistently placing it within caenagnathids (Longrich et al, ; Lü et al, ; Yu et al, ). The functional morphospace shows a similar pattern with that of mandible form, as caenagnathids and oviraptorids are separated on PC1 and do not overlap.…”

“…Caenagnathids might have partitioned niches as well, but with a different strategy: they developed a wide range of body sizes (Yu et al, ). In the Nei Mongol Erlian Formation, Gigantoraptor , the largest known caenagnathid, has a mandible length and dentary width of 46.0 and 10.0 cm, respectively (Ma et al, ).…”

Caenagnathids of the Dinosaur Park Formation (Campanian) of Alberta, Canada: anatomy, osteohistology, taxonomy, and evolution

“…Microvenator celer is recovered as the earliest-diverging caenagnathid, followed by Gigantoraptor erlianensis. Anomalipes zhaoi is recovered as more deeply nested than Gigantoraptor erlianensis, rather than as its sister taxon, contrary to the position recovered by Yu et al (2018). Chirostenotes pergracilis and Hagryphus giganteus are sister taxa, and they diverge from a clade comprising the paraphyletic 'elmisaurs' and the large-bodied Anzu wyliei and its kin.…”

“…Perplexingly, Caenagnathasia martinsoni is also recovered in this latter group, despite drastic differences in body size and morphology. The basal position of Chirostenotes pergracilis is also novel, as it has been deeply nested in Caenagnathinae in previous studies (Longrich et al 2013;Funston and Currie 2016;Yu et al 2018). However, each of these results is poorly supported by decay indices, which suggests that new data could alter the recovered topology.…”

“…The first caenagnathids (Gilmore 1924a;Sternberg 1932Sternberg , 1940Parks 1933) were recovered from the Dinosaur Park Formation (DPF) of Alberta, which continues to produce the most abundant caenagnathid material worldwide. However, caenagnathids are now also known from China (Yao et al 2015;Yu et al 2018), Mongolia (Osmólska 1981;Currie et al 2016a), throughout the United States Caenagnathids of the Dinosaur Park Formation (Campanian) of Alberta, Canada: anatomy, osteohistology, taxonomy, andevolution et al 2015, 2016a), but numerous issues remain unresolved. Of chief importance is the taxonomy of DPF caenagnathids, which remains problematic because of fragmentary, isolated specimens, and little overlap between referable material of each taxon.…”