Eudyptes atatu sp. nov. (1 Viewer)

[Fred Ruhe]

Daniel B. Thomas, Alan J. D. Tennyson, R. Paul Scofield, Tracy A. Heath, Walker Pett and Daniel T. Ksepka, 2020

Ancient crested penguin constrains timing of recruitment into seabird hotspot

Proceedings of the Royal Society B: Biological Sciences. 287 (1932): Article ID 20201497. doi:10.1098/rspb.2020.1497

Abstract and free pdf: https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2020.1497

New Zealand is a globally significant hotspot for seabird diversity, but the sparse fossil record for most seabird lineages has impeded our understanding of how and when this hotspot developed. Here, we describe multiple exceptionally well-preserved specimens of a new species of penguin from tightly dated (3.36–3.06 Ma) Pliocene deposits in New Zealand. Bayesian and parsimony analyses place Eudyptes atatu sp. nov. as the sister species to all extant and recently extinct members of the crested penguin genus Eudyptes. The new species has a markedly more slender upper beak and mandible compared with other Eudyptes penguins. Our combined evidence approach reveals that deep bills evolved in both crested and stiff-tailed penguins (Pygoscelis) during the Pliocene. That deep bills arose so late in the greater than 60 million year evolutionary history of penguins suggests that dietary shifts may have occurred as wind-driven Pliocene upwelling radically restructured southern ocean ecosystems. Ancestral area reconstructions using BioGeoBEARS identify New Zealand as the most likely ancestral area for total-group penguins, crown penguins and crested penguins. Our analyses provide a timeframe for recruitment of crown penguins into the New Zealand avifauna, indicating this process began in the late Neogene and was completed via multiple waves of colonizing lineages.

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Fred

 

[Fred Ruhe]

Systematic palaeontology

Aves Linnaeus, 1758
Sphenisciformes Sharpe, 1891
Spheniscidae Bonaparte, 1831
Eudyptes Vieillot, 1816
Type species. Eudyptes atatu sp. nov. (this is of course not the type species, that will be Aptenodytes chrysocome J. R. Forster, 1781. (FR))

Holotype. NMNZ S.046318—cranium, mandible, seven vertebrae, sternum, left coracoid, right coracoid, right humerus, right scapula, right ulna, right radius (figure 1, see electronic supplementary material, S1 for measurements).
Referred material. CM 2017-62-8-1 cranium; CM 2016.33.4.1 synsacrum and pelvis; CM 2016.33.4.2 femur; CM 2016.33.4.3 tibiotarsus; CM 2016.33.5 sternum, scapula, coracoid, humerus, ulna (proximal end), radius (proximal end); CM 2016.33.6.1 cranium; 2016.33.6.2 mandible fragment; CM 2016.33.7 cranium; 2016.33.8 cranium; NMNZ S.046315 cranium; NMNZ S.046317 cranium; NMNZ S.046319 synsacrum and pelvis, femur, tibiotarsus, tarsometatarsus; NMNZ S.046320 rib fragment, scapula, humerus, femur. See electronic supplementary material, S1, figures S1–S8.

Diagnosis. Referred to Eudyptes based on (1) strong sigmoid curvature of jugal bar, (2) presence of shelf of bone bounding the salt gland fossa, (3) greatly deepened temporal fossae, (4) strongly shortened tarsometatarsus (ratio of length to proximal width less than 2.0) and (5) moderately deep sulcus between metatarsals II and III. Characters 1, 2 and 4 also occur within Pygoscelis, which differs from Eudyptes in exhibiting very weakly developed temporal fossae, partial or complete fusion of the ilia to the synsacrum, and a shallow sulcus between metatarsals II and III. Characters 1, 3, 4 and 5 also occur in Megadyptes, which differs from Eudyptes in having a less strongly curved jugal bar and a very deep depression for insertion of the iliotrochanteris muscle near the proximal margin of the trochanteric crest of the femur. Differentiated from all extant and recently extinct species of Eudyptes by (1) upper beak slender in dorsal view (versus rostral tip markedly swollen in extant Eudyptes) and (2) mandibular ramus modestly deepened at midpoint (versus strongly deepened in extant Eudyptes). Eudyptes atatu can be differentiated from the poorly known Eudyptes calauina (for which the skull remains unknown) by much smaller size (tarsometatarsus length 29.1 mm in E. atatu versus 41.3 mm in E. calauina holotype) and less robust tarsometatarsus (ratio of length to proximal width 1.9 in E. atatu versus 1.7 in E. calauina).

Etymology. From Te reo Ma¯ ori, ata tu¯ (‘dawn’), referencing the stem position within Eudyptes and the earliest recorded appearance of Eudyptes in New Zealand. Type locality and horizon. Late Pliocene (Piacenzian) Tangahoe Formation in the southern Taranaki region of the North Island of New Zealand [6]. Local Waipipian stage, constrained to 3.36–3.06 Ma based on oxygen isotope stage and magnetic polarity data (see [6,7]). Holotype and referred specimens were surface collected and do not have an exact Fossil Record Database record, but see Q21/f0002 for nearby location.

Fred

Figure 1. Eudyptes atatu sp. nov. showing key diagnostic features. Holotype specimen NMNZ S.046318 showing (a) right lateral view of skull and block with (c) mandible and (d ) postcranial elements. (b) Right lateral view of Snares crested penguin Eudyptes robustus NMNZ OR.023746 for comparison. Referred material of E. atatu including (e) S.046315 dorsal view of skull, ( f ) CM 2017-62-8-1 left lateral view of skull, (g) NMNZ S.046320 right humerus caudal view, and (h) dorsal and (i) plantar views of NMNZ S.046319 right tarsometatarsus. Ano, apertura nasale ossea (naris). Clh, crista lateralis hypotarsi (lateral hypotarsal crest); Co, coracoid; Cmh, crista medialis hypotarsi (medial hypotarsal crest); F*, frontal with wide shelf bordering the salt gland fossa; Fte*, fossa temporalis (temporal fossa) that is relatively deep; Fvpl, foramen vasculare proximale lateralis (medial proximal vascular foramen); Fvpm, foramen vasculare proximale mediale (medial proximal vascular foramen); Hu, humerus; Ic, incisura capitus (capital incisure); Imp, impressio musculus pectoralis ( pectoral muscle impression); Mr, ramus mandibula (mandibular ramus); Oj*, os jugale ( jugal bar) showing distinct curvature; Op, os palatinum ( palatine); Ma, articular end of mandible; Mr*, mandibular ramus that is relatively narrow at midpoint; Ra, radius; Sc, scapula; Sldl, sulcus longitudinalis dorsalis lateralis (lateral dorsal longitudinal sulcus); Sldm*, sulcus longitudinalis dorsalis medialis (medial dorsal longitudinal sulcus) which is moderately deep; St, sternum; Tmtc, tuberositas musculus tibialis cranialis (tuberosity for cranial tibial muscle); Tv, tuberculum ventral (ventral tubercle); Ve, vertebra. Asterisks denote diagnostic characters. Photographs (a)–(e), (g)–(i) from Jean-Claude Stahl at Museum of New Zealand Te Papa Tongarewa, photograph (f ) from R. Paul Scofield at Canterbury Museum. (Online version in colour.)