Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2007 Jul 10;104(28):11545-50.
doi: 10.1073/pnas.0611099104. Epub 2007 Jun 29.

Paleogene equatorial penguins challenge the proposed relationship between biogeography, diversity, and Cenozoic climate change

Affiliations
Free PMC article

Paleogene equatorial penguins challenge the proposed relationship between biogeography, diversity, and Cenozoic climate change

Julia A Clarke et al. Proc Natl Acad Sci U S A. .
Free PMC article

Abstract

New penguin fossils from the Eocene of Peru force a reevaluation of previous hypotheses regarding the causal role of climate change in penguin evolution. Repeatedly it has been proposed that penguins originated in high southern latitudes and arrived at equatorial regions relatively recently (e.g., 4-8 million years ago), well after the onset of latest Eocene/Oligocene global cooling and increases in polar ice volume. By contrast, new discoveries from the middle and late Eocene of Peru reveal that penguins invaded low latitudes >30 million years earlier than prior data suggested, during one of the warmest intervals of the Cenozoic. A diverse fauna includes two new species, here reported from two of the best exemplars of Paleogene penguins yet recovered. The most comprehensive phylogenetic analysis of Sphenisciformes to date, combining morphological and molecular data, places the new species outside the extant penguin radiation (crown clade: Spheniscidae) and supports two separate dispersals to equatorial (paleolatitude approximately 14 degrees S) regions during greenhouse earth conditions. One new species, Perudyptes devriesi, is among the deepest divergences within Sphenisciformes. The second, Icadyptes salasi, is the most complete giant (>1.5 m standing height) penguin yet described. Both species provide critical information on early penguin cranial osteology, trends in penguin body size, and the evolution of the penguin flipper.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
Holotype of P. devriesi (MUSM 889). (a) Skull in dorsal view. (b) Skull in left lateral view. (c) Left dentary in medial view. (d) Skull in ventral view. (e) Right humerus in anterior and posterior views. (f) Right humerus in proximal view. (g) Right humerus in distal view. (h) Left carpometacarpus in distal view. (i) Left carpometacarpus in ventral and dorsal views. (j) Synsacrum, ilia, and left femur in dorsal view. (k) Right femur in posterior and anterior views. (l) Left tarsometatarsus in plantar and dorsal views. All to same scale except j (scale for j is at lower left); f, g, and h are enlarged in the line drawings to show detail. Anatomical abbreviations: ac, acetabulum; art, articular surface for antitrochanter; at, antitrochanter; cb, coracobrachialis insertion; d, depression on lingual surface of dentary; f, femur; fmn, articular facet for first digit of metacarpal III; fmj, articular facet for first digit of metacarpal II; ld, scar for latissimus dorsi; mtr, middle trochlear ridge; nc, nuchal crest; po, postorbital process; pp, pisiform process; ps, expansion of parasphenoid; ptr, posterior trochlear ridge; sc, scar for supracoracoideus; sf, fossa for salt gland; sp, supracondylar tubercle.
Fig. 2.
Fig. 2.
Holotype of I. salasi (MUSM 897). (a) Skull in lateral view. (b) Mandible in dorsal view. (c) Left quadrate in lateral view. (d) Left humerus in posterior and anterior views. (e) Left ulna in ventral view. (f) Left radius in ventral view. (g) Left carpometacarpus and phalanges in ventral view. (h) Left coracoid in ventral view. All are to the same scale except c, which is enlarged to show detail. Anatomical abbreviations: ac, acrocoracoid process; af, anteorbital fenestra; am, tubercle for m. adductor mandibulae externus; atr, anterior trochlear ridge; cb, coracobrachialis insertion; cf, ovoid coracoid fossa; fa, distal facet of first metacarpal; j, jugal; lc, lateral cotyle of mandible; mc, medial cotyle of mandible; mtr, middle trochlear ridge; n, nares; ol, olecranon; ptr, posterior trochlear ridge; qc, quadratojugal cotyle; qt, tubercle on optic process; sc, scar for supracoracoideus; sf, fossa for salt gland; ss, sesamoid of m. scapulotriceps tendon; tf, temporal fossa; tr, tricipital fossa; ts, transverse sulcus.
Fig. 3.
Fig. 3.
Recovered penguin phylogenetic relationships, including placement of new species P. devriesi and I. salasi (in red) and showing stratigraphic and latitudinal distribution of species against δ18O values as a proxy for changes in global temperature over the last 65 Ma (from ref. 12). The strict consensus cladogram of the four most parsimonious trees (4,356 steps) is shown. Black bars indicate stratigraphic range. No neospecies has a fossil record extending beyond the Pleistocene (6). Extinct taxa are indicated with a †. Branch color indicates the latitude of extant taxon breeding territories and the paleolatitude of fossil taxon localities, with ancestral latitude ranges reconstructed along internal branches from downpass optimization: 0–30°S latitude (yellow), 30–60° (green), and 60–90° (blue). Silhouettes reflect body size; small silhouettes indicate taxa smaller than extant Aptenodytes patagonicus (king penguin), medium silhouettes indicate taxa intermediate between A. patagonicus and Aptenodytes forsteri (emperor penguin), and large silhouettes indicate taxa larger than A. forsteri. The plot of mean δ18O values and estimated mean ocean water temperature scale (only valid for an ice-free ocean, preceding major Antarctic glaciation at ≈35 Ma) are from ref. and give an indication of changing conditions across the Cenozoic.

Similar articles

Cited by 20 articles

Publication types

LinkOut - more resources