Tuesday, June 12, 2018

[Paleontology • 2018] Anomalipes zhaoi • A New Caenagnathid Dinosaur from the Upper Cretaceous Wangshi Group of Shandong, China, with Comments on Size Variation Among Oviraptorosaurs


Anomalipes zhaoi 
 Yu, Wang, Chen, Sullivan, Wang, Wang & Xu, 2018


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.


Figure 2 Preserved left femur, tibia, and fibula of Anomalipes zhaoi ZCDM V0020.
 Left femur in anterior (a), posterior (b), lateral (c), medial (d) and proximal (e) views.
Left tibia in anterior (f), posterior (g) and distal (j) views. Shading indicates the articular facet for the ascending process of the astragalus.
Left fibula in lateral (h) and medial (i) views.

Abbreviations: act, accessory trochanter; dg, distinct groove; fc, fibular crest; fh, femoral head; ft, fourth trochanter; gt, greater trochanter; if, iliofibularis tubercle; ig, intercondylar groove; lm, lateral malleolus; lr, lateral ridge; lt, lesser trochanter; mm, medial malleolus; pt, posterior trochanter; taf, triangular articular facet. Scale bar 1 cm.

Figure 3 Preserved pedal elements of Anomalipes zhaoi ZCDM V0020.
Left metatarsal III in lateral (a), medial (b), posterior (c), anterior (d), proximal (e) and distal (f) views. Dark lines indicate ridges on the posterior surface of the shaft.
Phalanx IV-1 in lateral (g), medial (h), proximal (i), and distal (j) views. Phalanx II-3 in lateral (k) and medial (l) views.

Abbreviations: fl, flexor tubercle; lc, lateral condyle; lgf, ligament fossa; pdc, proximal dorsal crest; pdl, proximal dorsal lip; vr, ventral ridge; ptaf, proximal triangular articular facet; rlmh, ridge-like medial hemicondyle; vr, ventral ridge (extending to medial hemicondyle). Scale bar 1 cm.


Systematic palaeontology

Theropoda Marsh 1881
Oviraptorosauria Barsbold 1976

Caenagnathidae Sternberg 1940

Anomalipes zhaoi gen.et sp. nov

Etymology: Generic name is a combination of the Latin “Anomalus” and “pes”, referring to the unusual shape of the foot. Specific name is in honour of Xijin Zhao, a Chinese palaeontologist who has made great contributions to research on Zhucheng dinosaur fossils.

Holotype: ZCDM V0020 (Zhucheng Dinosaur Museum, Zhucheng, Shandong, China), an incomplete left hindlimb, including the left femur missing the distal end, the left tibia missing the proximal end, the left fibula missing the distal and proximal ends, a complete metatarsal III and two pedal phalanges. Although these bones are disarticulated, they are inferred to be derived from a single theropod individual given that 1) they were preserved in a small area of less than 0.3 square metres within a Shantungosaurus bonebed; and 2) no other theropod skeletal elements are preserved nearby.

Locality and horizon: Kugou, Zhucheng City, Shandong Province, China. Upper Cretaceous Wangshi Group.

Diagnosis: A new caenagnathid with the following unique combination of features: femoral head anteroposteriorly narrow and somewhat deflected posteriorly; accessory trochanter low; lateral ridge present on femoral lateral surface; weak fourth trochanter present; metatarsal III with triangular proximal articular surface, prominent anterior flange near proximal end, medial hemicondyle much narrower than lateral hemicondyle, and longitudinal groove on distal articular surface; and pedal phalanx II-3 with lateral collateral groove deeper and more dorsally located than medial groove.

Figure 5 Simplified oviraptorosaurian phylogenetic tree, showing size ranges for basal oviraptorosaurs, the Caenagnathidae, and the Oviraptoridae. Grey boxes represent body mass ranges for three oviraptorosaurian groups: basal oviraptorosaurs, oviraptorids, and caenagnathids. See the electronic supplementary material for estimated body masses of various oviraptorosaurian species.

 Abbreviations: Caud: Caudipteryx zoui; Avim: Avimimus portentosus; Conc: Conchoraptor gracilis; Micr: Microvenator celer; Wula: Wulatelong gobiensis; Citi: Citipati osmolskae; Nank: Nankangia jiangxiensisAnom: Anomalipes zhaoi; Neme: Nemegtia barsboldi; Anzu: Anzu wyliei; Giga: Gigantoraptor erlianensis.

Yilun Yu, Kebai Wang, Shuqing Chen, Corwin Sullivan, Shuo Wang, Peiye Wang and Xing Xu. 2018. A New Caenagnathid Dinosaur from the Upper Cretaceous Wangshi Group of Shandong, China, with Comments on Size Variation Among Oviraptorosaurs. Scientific Reports. volume 8, Article number: 5030. DOI: 10.1038/s41598-018-23252-2 


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