Sapeornis chaoyangensis
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Sapeornis Temporal range: Early Cretaceous, 124.5–120 Ma |
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| Fossil specimen, Hong Kong Science Museum | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Avebrevicauda |
| Family: | †Omnivoropterygidae |
| Genus: |
†Sapeornis Zhou & Zhang, 2002 |
| Species: | †S. chaoyangensis |
| Binomial name | |
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Sapeornis chaoyangensis Zhou & Zhang, 2002 |
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| Synonyms | |
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Sapeornis is a type of avialan which lived during the early Cretaceous period (late Aptian to early Albian, roughly 125-120 mya). The genus Sapeornis contains only one species, Sapeornis chaoyangensis.
Sapeornis was large for an early avialan, about 30–33 centimetres (0.98–1.08 ft) long in life, excluding the tail feathers.
The hand of Sapeornis was far more advanced than that of Archaeopteryx. It had three fingers, the outer ones with two and the middle one with three phalanges, and a well-fused carpometacarpus. Its arms were about half again as long as the legs, suggesting a large wing area. On the other hand, its shoulder girdle was apparently ill-adapted to flapping flight and its furcula was unusual, with a hypocleidum similar to more advanced avialans but a general anatomy even more primitive than in Archaeopteryx. The humerus was large and bore holes, apparently to save weight, as in the Confuciusornithidae.
The skull has a handful of teeth in the upper jawtip only. Sapeornis had gastralia but no (or unossified) uncinate processes. The breastbone (sternum) was either absent or, more likely, made of cartilage rather than bone, as in more primitive theropods. The pygostyle was rod-like as in Confuciusornis and Nomingia, but like in the former there was no long bony tail anymore. While the tarsometatarsi were more fused than in Archaeopteryx, the fibula was long and reached the distal point of the tarsal joint, not reduced as in more modern birds (and some non-avian theropods like Avimimus). The first toe pointed backwards. In specimen IVPP V12375, the stomach contained numerous small gastroliths. Analysis of its skeletal bones suggest that it had an ontogeny and slow growth like Archaeopteryx and small carnivorous dinosaurs, rather than the explosively fast growth seen in modern birds.
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