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Ancient giant penguins liked it hot

June 25, 2007
Courtesy PNAS
and World Science staff

New fos­sil finds are shed­ding light on the strange world of an­cient pen­guins, some of which were as tall as many hu­mans.

Jul­ia Clarke of North Car­o­li­na State Un­ivers­ity in Ra­leigh, N.C. and col­leagues dis­cov­ered skulls and other bones of two ex­tinct pen­guin spe­cies in coast­al Pe­ru. 

Artists con­cep­tion of the late Eo­cene gi­ant pen­guin Icadyptes salasi (right) and the mid­dle Eo­cene Pe­rudyptes de­vriesi (left) are shown to scale with the on­ly ex­tant pen­guin in­hab­it­ing Pe­ru, Sphenis­cus hum­bolti (cen­ter). Icadyptes salasi is said to be the first gi­ant pen­guin known from a com­plete skull. (Image Cour­te­sy PNAS)

The smaller of the two, Pe­ru­dyp­tes de­v­rie­si, was around the size of today’s King Pen­guins, re­search­ers said. These are about three feet (90 cm) tall.

The larg­er of the two, Ica­dyp­tes sa­lasi, would have been fear­some to en­coun­ter at over five feet (1.5 m) tall, and with a long beak, sci­ent­ists said. The sur­prise, they added, was that pen­guins—and large ones in par­tic­u­lar—would live in such a hot place and time as these ones did, near the equa­tor.

Pa­le­on­tol­ogists gen­er­ally as­sume that spe­cies mov­ing from cold to warm cli­mates evolve to be smaller, as the balmy tem­per­a­tures elim­i­nate the need for a large body to con­serve heat.

Clarke’s team dat­ed the bones to the mid­dle and late Eo­cene pe­ri­od, 42 and 36 mil­lion years ago, re­spec­tively—one of the Earth’s warmest eras in the past 65 mil­lion years. 

Pa­le­on­tol­ogists previously thought pen­guins arrived so near the equa­tor only four to eight mil­lion years ago, dur­ing a much cool­er time, Clarke and col­leagues said. Penguins are thought to have evolved at least 65 mil­lion years ago from the same an­ces­tral stock as alba­trosses, shear­waters and petrels.

Sa­id to be the first com­plete known skull of a gi­ant pen­guin, from the new­found spe­cies Icadyptes salasi. A skull of Sphenis­cus hum­bolti, the on­ly spe­cies in­hab­it­ing Pe­ru to­day, is shown for com­par­i­son. The scale ba­r at low­er right rep­re­sents a length of 1 cm. (Pho­to cour­tesy Dan­iel Ksep­ka.)

As ar­rest­ing as the sight of giant pen­guins might be, the new­found pen­guins weren’t the big­gest known to ev­o­lu­tion­ary his­to­ry. 

Many an­cient pen­guins were out­sized by mod­ern stan­dards. Ex­tinct pen­guins were an es­ti­mat­ed 50 per­cent taller on av­er­age than liv­ing ones.

The tallest known, An­thro­por­nis nor­den­skjoel­di, found on Sey­mour Is­land in Ant­arc­ti­ca, stood at 170 cm (five feet sev­en inches). Pachy­dyptes pon­dero­sus, found in New Zea­land, was only slightly short­er, but as heavy as an adult hu­man male.

But the newfound Icadyptes salasi, of the late Eocene, is the first gi­ant pen­guin known from a com­plete skull, re­search­ers said. The stu­dy appears in the advance on­line edi­tions of the re­search jour­nal Pro­ceed­ings of the Na­tion­al Aca­d­emy of Scien­ces this week.

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New fossil finds are shedding light on the strange world of ancient penguins, some of which were as tall as many humans are. Julia Clarke of North Carolina State University in Raleigh, N.C. and colleagues discovered skulls and bones of two extinct penguin species in the coastal desert of Peru. The smaller of the two, Perudyptes devriesi, was around the living king penguins, which are around three feet (90 cm) tall, researchers said. The larger, Icadyptes salasi, would have been fearsome to encounter at over five feet (1.5 m) tall, with a long beak, researchers said. The surprise, they added, was that penguins – and large ones in particular – would inhabit such hot climes as these ones did, in a near-equatorial region. Paleontologists generally assume that species moving from cold to warm climates evolve to be smaller, as the balmy temperatures eliminate the need for a large body to conserve heat. Scientists dated the specimens to the middle and late Eocene period, 42 and 36 million years ago, respectively – one of the Earth’s warmest eras in the past 65 million years. Before these findings, paleontologists thought that penguins reached low latitudes only four to eight million years ago, during a period of much cooler climate, Clarke and colleagues said. As arresting as the sight of such penguins might be, they weren’t the biggest penguins known to evolutionary history. Many ancient penguins were inordinately large by today’s standards; extinct penguins were an estimated 50 percent taller on average than living ones. The largest known fossil penguin, Anthropornis nordenskjoeldi, found on Seymour Island in Antarctica, stood 170 cm (five feet seven inches) tall. Pachydyptes ponderosus, found in New Zealand, was only slightly shorter.