Struthio anderssoni, also known as the East Asian ostrich, is a large extinct species of ostrich that lived in the Pleistocene and Holocene in China, Mongolia and Russia. It was much larger than extant ostriches, with estimated mass of .
Taxonomy In 2023, based on a re-examination of cast of a femur, Éric Buffetaut suggested that this species be moved to the genus Pachystruthio, noting that the main differences are in size and not morphology between the femur of Pachystruthio and that of S. anderssoni.
Mikhailov and Zelenkov suggested this species is a larger bodied form of extant ostriches. Buffetaut disagreed with this hypothesis, noting the significantly larger size and differing morphological features, including the minimum shaft width/total length ratio of the femur.
Description Buffetaut and Angst conclude that Struthio anderssoni was significantly larger than the modern ostrich, with both eggs and skeletal remains indicating this.
Femur The femur of one specimen from Upper Cave at Zhoukoudian measures 355 mm in length (within the estimated range of 304 – 371 mm for the species) and 69 mm in minimum shaft width. A 187 mm minimum shaft circumference on a cast from this species gives a mass estimate of . Another partial femur has a minimum shaft circumference of 190 mm, which gives it a mass estimate of .
Eggs In 1933, three nearly complete eggs were measured to be in length and in width. Slightly differing size ranges from Lowe (1931) were calculated in a 2025 article to correspond to in mass. Buffetaut and Angst had earlier calculated a marginally smaller egg mass, being . Despite their larger size, the eggs are not significantly thicker than those of modern ostriches, being 2.1–2.3 mm in shell thickness. A mass estimate based on the eggs results in , with a mean of .
Paleobiology and extinction The large body and egg size of S. anderssoni may be an adaptation for a cold climate, in which this species was more cold tolerant than African ostriches (although this is not the sole explanation, due to the existence of large ostriches in warmer climates), but both being well suited for arid environments. They may have had similar internal physiology to African ostriches, due to similarity in egg morphology.
The youngest dates obtained by mass spectrometry analysis of eggshell fragments reveal that the species survived until at least 8.9 ka BP.
See Also
Struthio oldawayi Struthio wimani
References