Eogranivora edentulata gen. et sp. nov. (1 Viewer)

Xiaoting Zheng, Jingmai K. O'Connor, Xiaoli Wang, Yan Wang, Zhonghe Zhou, 2018

Reinterpretation of a previously described Jehol bird clarifies early trophic evolution in the Ornithuromorpha

Proceedings of the Royal Society B: Biological Sciences. 285 (1871): 20172494. doi:10.1098/rspb.2017.2494

Abstract:

STM35-3 from the Yixian Formation is the only Early Cretaceous ornithuromorph preserving direct evidence of granivory. The crop contains numerous seeds and the preservation of gastroliths presumably within the ventriculus indicates this diet was paired with the presence of a gastric mill as in living granivorous birds. STM35-3 was originally referred to Hongshanornis longicresta, member of a diverse clade of small, basal ornithuromorphs with elongate hindlimbs known as the Hongshanornithidae. Hindlimb proportions suggest that hongshanornithids were wading birds, an ecological inference somewhat in conflict with direct evidence suggesting Hongshanornis fed on seeds. However, close inspection of STM35-3 reveals that the specimen represents a new species not closely related to hongshanornithids, distinguished by large forelimbs that exceed the length of the hindlimbs, robust and narrow coracoids, and a delicate edentulous rostrum. By contrast, all hongshanornithids have hindlimbs that far exceed the length of the forelimbs, coracoids with wide sternal margins, and small teeth throughout the upper and lower jaws. Reinterpretation of this new taxon, Eogranivora edentulata gen. et sp. nov, helps to clarify trophic driven patterns of tooth loss within the Ornithuromorpha. Apparent loss of the hallux may represent the first such occurrence in a Mesozoic bird and suggests a highly terrestrial lifestyle.

Enjoy,

Fred

Systematic palaeontology
Aves Linnaeus 1758
Ornithothoraces Chiappe 1995
Ornithuromorpha Chiappe 2002
Eogranivora gen. nov.
Diagnosis. As for species.
Eogranivora edentulata sp. nov.

Holotype
STM (Shandong Tianyu Museum of Nature, Pingyi, China) 35-3, a nearly complete fully articulated subadult–adult individual preserved in a slab and counterslab with weak feather impressions, crop contents and gastroliths.

Etymology
‘Eogranivora edentulata’ meaning toothless early granivore. The generic name ‘Eogranivora’, eo- meaning early and -granivora meaning seed-eater, refers to the crop contents preserved in the holotype; the specific name ‘edentulata’ means without teeth and refers to the toothless rostrum that characterizes this taxon.

Diagnosis
Medium-sized ornithuromorph (U-shaped furcula, coracoid with procoracoid process, small plough-shaped pygostyle, caudally expanded and dorsoventrally compressed first phalanx of the major digit, U-shaped pubes) with the unique combination of the following morphological features: upper and lower jaws completely edentulous; well-developed mandibular symphysis occupying the rostral 20% of the mandible; coracoid without distinct sternolateral process; lateral and intermediate sternal trabeculae narrow and extend caudally to the same level; xiphial region of sternum V-shaped; short and robust alular digit; dorsomedially oriented bluntly triangular process present on the pubes located one-third of the length from the proximal end; metatarsal I and hallux absent.

Locality and horizon
Lower Cretaceous Yixian Formation (125 Ma), Dawangzhangzi, Lingyuan, Western Liaoning Province, China.

Enjoy,

Fred