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| Plotornis archaeonautes Ksepka, Tennyson, Richards & Fordyce, 2023 |
ABSTRACT
Albatrosses are among the most intensely studied groups of living birds, yet their fossil record remains sparse. Despite modern albatrosses being more abundant and widespread in the Southern Hemisphere, the vast majority of fossil albatrosses identified to date come from Northern Hemisphere localities. Here, we describe Plotornis archaeonautes sp. nov., a new albatross species from the earliest Miocene that represents the earliest record of Procellariiformes in New Zealand and the earliest uncontroversial record of the clade Pan-Diomedeidae from the Southern Hemisphere. Phylogenetic analyses support the placement of Plotornis outside of the clade uniting all extant albatrosses. The new fossil reveals that stem lineage albatrosses were widespread by the onset of the Neogene. Although the humerus of Plotornis archaeonautes exhibits a short processus supracondylaris dorsalis, this early species may have possessed at least one of the unique ossifications associated with the patagial bracing system present in modern albatrosses.
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| Holotype (OU 22690: A-I, M-P, S-T) and referred specimens (NMNZ S48291: J-L, NMNZ S47315: Q-R) of Plotornis archaeonautes. Beak tip in A, lateral and B, ventral views, C, skull roof in dorsal view, cervical vertebra 12 in D, cranial, E, lateral and F, dorsal views, fragment of left humerus in G, caudal and H, cranial views, I, proximal end of right ulna in proximal view, referred right tarsometatarsus in J, proximal, K, dorsal and L, plantar views, right humerus in M, caudal and N, cranial views, left radius in O, ventral (rotated slightly) and P, distal views, referred left radius in Q, ventral and R, dorsal views, S, proximal portion of right carpometacarpus in ventral view, T, shaft of left carpometacarpus in dorsal view. Abbreviations: fgn: fossa glandulae nasalis; fos: fossa housing subdivided pneumatic foramen; fur: furrow on lateral face of beak, gr: groove formed where furrow meets tomial margin; pf: pneumatic foramen; pp: processus pisiformis; st: sulcus tendineus; tb: tubercle at distal end of radius; tm: tomial margin; tmp: tubercle for the insertion of m. pectoralis. |
Aves Linnaeus, 1758
Procellariiformes Fürbringer, 1888
Pan-Diomedeidae G.R. Gray, 1840
Plotornis Milne-Edwards Citation1874
Type Species. Plotornis delfortrii Milne-Edwards Citation1874
Included Species. Plotornis delfortrii, Plotornis graculoides and Plotornis archaeonautes (sp. nov.)
Comments. Pan-Diomedeidae is used here as a name for the albatross total group, i.e. all taxa more closely related to Diomedeidae than to any of the other extant clades of Procellariiformes.
Plotornis archaeonautes sp. nov.
Type Locality and Horizon. Earliest Miocene (Aquitanian) Mount Harris Formation, Hakataramea Quarry, South Canterbury, New Zealand (New Zealand Fossil Record Number I40/f442).
Diagnosis. Plotornis archaeonautes differs from Plotornis delfortrii in the more proximodistally elongated tuberculum supracondylare ventrale, shallower fossa m. brachialis, and less ventrally deflected proximal tip of the condylus dorsalis, and differs from Plotornis graculoides in having a more weakly developed tubercle at the distal end of the crista deltopectoralis, a less widened proximal end of the tarsometatarsus (relative to shaft width), and a more distal origin of the crista plantaris lateralis of the tarsometatarsus.
Measurements. Humerus distal width 19.5 mm (Plotornis delfortrii: ∼18.0 mm; Plotornis graculoides: 19.0 mm), tarsometatarsus proximal width 14.0 mm as preserved, estimated 15.0 mm when complete (Plotornis delfortrii: 12.6 mm; Plotornis graculoides: ∼14.5 mm).
Etymology. From the Greek ἀρχαῖος (ancient) + ναύτης (mariner). The name reflects the ancient age and the wide oceanic range of Plotornis albatrosses, and makes allusion to the fabled albatross of Samuel Taylor Coleridge's The Rime of the Ancient Mariner.
Daniel T. Ksepka, Alan J. D. Tennyson, Marcus D. Richards and R. Ewan Fordyce. 2023. Stem Albatrosses wandered Far: A New Species of Plotornis (Aves, Pan-Diomedeidae) from the earliest Miocene of New Zealand. Journal of the Royal Society of New Zealand [Special issue: Fossil vertebrates from southern Zealandia]. DOI: 10.1080/03036758.2023.2266390
