A phasianid bird from the Pleistocene of Tainan (1 Viewer)

[Fred Ruhe]

Cheng-Hsiu Tsai & Gerald Mayr, 2021

A phasianid bird from the Pleistocene of Tainan: the very first avian fossil from Taiwan

Journal of Ornithology (advance online publication)
doi: https://doi.org/10.1007/s10336-021-01886-w
https://link.springer.com/article/10.1007/s10336-021-01886-w

Free pdf:
https://link.springer.com/content/pdf/10.1007/s10336-021-01886-w.pdf

Abstract:

Taiwan accommodates more than 600 avian species, including about 30 endemic ones. As yet, however, no fossil birds have been scientifically documented from Taiwan, so that the evolutionary origins of this diversified avifauna remain elusive. Here we report on the very first fossil bird from Taiwan. This Pleistocene specimen, a distal end of the left tarsometatarsus, shows diagnostic features of the galliform Phasianidae, including an asymmetric plantar articular facet trochlea metatarsi III. Our discovery of a Pleistocene phasianid from Taiwan opens a new perspective on studies of the evolution of the avifauna in Taiwan because the fossil shows that careful search for fossils in suitable localities has the potential of recovering avian remains. In general, East Asia has an extremely poor avian fossil record, especially if terrestrial birds are concerned, which impedes well-founded evolutionary scenarios concerning the arrival of certain groups in the area. The Phasianidae exhibit a high degree of endemism in Taiwan, and the new fossil presents the first physical evidence for the presence of phasianids on the island, some 400,000â800,000 years ago. The specimen belongs to a species the size of the three larger phasianids occurring in Taiwan today (Syrmaticus mikado, Lophura swinhoii, and Phasianus colchicus). Still, an unambiguous assignment to either of these species is not possible due to the incomplete nature of the left tarsometatarsus. Because the former two species are endemic to Taiwan, the fossil has the potential to yield the first data on their existence in the geological past of Taiwan if future finds allow identification on species-level.

Enjor,

Fred

 

[Fred Ruhe]

Systematic paleontology

Aves Linnaeus, 1758
Galliformes Temminck, 1820
Phasianidae Horsfield, 1821
Gen. et. sp. indet.

Referred specimen
NTUM-VP 210117, a distal end of the left tarsometatarsus.
The high-resolution 3D file of NTUM-VP 210117 can be
freely downloaded at: https:// doi. org/ 10. 5281/ zenodo. 45529
28 or https:// schol ars. lib. ntu. edu. tw/ handle/ 12345 6789/556266. The specimen was first found by the private collector L.-R. Hou. LRH donated it to CHT (the first and corresponding author), the principal investigator of the Lab of Evolution and Diversity of Fossil Vertebrates at the National Taiwan University for the permanent curation and research.

Locality and geological horizon
NTUM-VP 210117 was collected from the Chi-Ting Formation in the city of Tainan, Taiwan (Fig. 1). The geological age of the Chi-Ting Formation ranges broadly from 0.8 to 0.4 million years ago (Chen 2016) in the Middle Pleistocene; see Chen (2016) and Otsuka (1984) for detailed lithological descriptions and the paleoenvironmental considerations of the Chi-Ting Formation. Due to the long-term, unmanageable, and somewhat destructive fossil collecting behavior along the Tsai-Liao River and nearby areas in Tainan, we refrain from providing the exact locality or more relevant information publicly. Nevertheless, the request can be addressed to CHT.

Diagnosis and morphological remarks
Except for some minor damage due to abrasion, the specimen (NTUM-VP 210117) is relatively intact. The proximal portion is broken, and the preserved proximodistal length is 21.66 mm. Nevertheless, the preserved lateromedial width across trochlea II and IV is 13.81 mm, comparable with male Syrmaticus mikado and Lophura swinhoii and slightly larger than that of female Phasianus colchicus.
NTUM-VP 210117 can be assigned to the Galliformes because of the possession of a diagnostic feature—a trochlea metatarsi III with an asymmetric plantar articular surface, in which the lateral rim reaches farther proximal than the medial one; for identifying the diagnostic features, see Mayr (2000)]. In other aspects of its morphology, NTUM-VP 210117 also closely resembles phasianids, including the presence of a plantar projection on the trochlea metatarsi II, and a relatively narrow incisura intertrochlearis. The specimen belongs to a species the size of the three larger phasianids occurring in Taiwan today: Mikado Pheasant (Syrmaticus mikado), Swinhoe’s Pheasant (Lophura swinhoii), and Common Pheasant (Phasianus colchicus), but an unambiguous assignment to either of these species is not possible. Because the three extant species are almost inseparable based only on the distal portion of the tarsometatarsus, we currently identify NTUM-VP 210117 as Phasianidae gen. et. sp. indet.

Fred


Fig. 1 Anatomical interpretations of NTUM-VP 210117 from the Pleistocene of Taiwan and morphological comparison to three extant phasianids. a dorsal view of the left tarsometatarsus from the Pleistocene of Taiwan (NTUM-VP 210117); b dorsal view of the left tarsometatarsus of Syrmaticus mikado (SMF 2448); c dorsal view of the left tarsometatarsus of Lophura swinhoii (SMF 19620); d dorsal view of the left tarsometatarsus of Phasianus colchicus (SMF 19325); e plantar view of the left tarsometatarsus from the Pleistocene of Taiwan (NTUM-VP 210117); f plantar view of the left tarsometatarsus of Syrmaticus mikado (SMF 2448); g plantar view of the left tarsometatarsus of Lophura swinhoii (SMF 19620); h plantar view of the left tarsometatarsus of Phasianus colchicus (SMF 19325). The 3D file of NTUM-VP 210117 is freely accessible (see Availability of data and material) for detailed examination of our anatomical explanations