Icadyptes

Abstract: We present the first detailed description of the giant Eocene penguin Icadyptes salasi . The species is characterized by a narrow skull with a hyper-elongate spear-like beak, a robust cervical column and a powerful flipper. The bony beak tip of Icadyptes is formed by fusion of several elements and is unique among penguins, differing markedly from previously described giant penguin beaks. Vascular canal patterning similar to that of boobies, frigatebirds and albatrosses suggests I. salasi may have had a thin, sheet-like rhamphotheca unlike the thick rugose rhamphotheca of modern penguins. Together, these features suggest a novel ecology for I. salasi , most likely involving the capture of larger prey items via spearing. As the first described giant penguin specimen to preserve a complete wing skeleton, the I. salasi holotype yields significant insight into the shape, proportions and orientation of the wing in giant penguins. In articulation, the forelimb of I. salasi is straighter, permitting less manus and antibrachium flexion, than previous depictions of giant penguin wings. Cross-sections of the humerus and ulna reveal a level of osteosclerosis equalling or surpassing that of extant penguins. Based on ontogenetic data from extant penguins and the morphology of the carpometacarpus of I. salasi , we infer the retention of a free alular phalanx in basal penguins. Previously, the status of this element in penguins was disputed. Differences in the proportions of the manual phalanges contribute to a more abruptly tapering wingtip in I. salasi compared with crown penguins. Fossils from Peru, including the I. salasi holotype specimen, document that penguins expanded to nearly the whole of their extant latitudinal range early in their evolutionary history and during one of the warmest intervals in the Cenozoic.

Abstract: Penguins (Aves: Sphenisciformes) are icons of Antarctic wildlife. Nevertheless, they are not restricted to this part of the Southern Hemisphere, and most species occur in more northerly areas (Davis & Renner 2003). The longest latitudinal range (across nearly 758 latitude) of penguin rookeries comprises coastal West Antarctica, the Scotia Arc and the Pacific coast of South America (Jadwiszczak 2009, fig. 3). Taking into account plate tectonics, a distributional pattern similar to that present in extant Sphenisciformes can be observed in the record of Eocene (55.8–33.9 Ma) penguins. Their remains are known from as far south as the Antarctic Peninsula (mainly isolated bones) and as far north as Peru (Jadwiszczak 2009, Clarke et al. 2010). The most diverse assemblage of these seabirds comes from the Eocene La Meseta Formation of Isla Marambio (Seymour Island; northern Antarctic Peninsula), particularly from its upper part corresponding to the late middle and late Eocene (Jadwiszczak 2010, fig. 2). Individuals from four species (two genera differing in morphology and frequency), Anthropornis nordenskjoeldi Wiman, 1905, A. grandis (Wiman, 1905), Palaeeudyptes gunnari (Wiman, 1905), P. klekowskii Myrcha, Tatur & del Valle, 1990, were larger than the largest modern penguins (Aptenodytes forsteri Gray; Jadwiszczak 2001). The record of Eocene penguins from South America comprises a partial skeleton (slightly smaller than that of A. forsteri) from the late middle Eocene of Argentine Tierra del Fuego (Clarke et al. 2003), ten bones of both small-bodied and ‘giant’ birds (undetermined sphenisciforms and Palaeeudyptes sp. respectively) from the middle to late Eocene of the Magallanes Region, Chile (Sallaberry et al. 2010), and partial skeletons of three species from the middle and late Eocene of Peru: a relatively largebodied Perudyptes devriesi Clarke et al., 2007 as well as two ‘giant’ penguins, Icadyptes salasi Clarke et al., 2007 and Inkayacu paracasensis Clarke et al., 2010 (Clarke et al. 2007, 2010). Inkayacu paracasensis, diagnosed mainly on the basis of five ‘‘autapomorphies within Sphenisciformes’’ (i.e. unique features), is of particular interest because its remains include partial feathering (Clarke et al. 2010). Presented here are bones from the late Eocene of the Antarctic Peninsula demonstrating that some of postulated (Clarke et al. 2010) autapomorphies of Inkayacu are actually synapomorphies shared with taxa represented by these Antarctic specimens. This finding substantially expands knowledge of the source region for the second oldest equatorial ingression by Palaeogene penguins. Two Antarctic penguin bones discussed here come from the upper La Meseta Formation (north-north-west side of the unit Telm7; Jadwiszczak 2010, fig. 1), Seymour Island (64817'S, 56845'W). They are permanently deposited at the Institute of Biology, University of Bia"ystok, Poland; abbreviated IB/P/B (Jadwiszczak 2006).

Abstract: Penguins (Sphenisciformes) are extremely specialized seabirds from the Southern Hemisphere. The fossil record of this order covers most of the Cenozoic. The oldest representatives of Sphenisciformes come from the Paleocene of New Zealand (Waimanu manneringi and W. tuatahi) and the Antarctic Peninsula (Crossvallia unienwillia). These archaic penguins were large flightless birds differing in terms of body shape from their modern counterparts. Moreover, several lines of evidence indicate a lack of some adaptations within their locomotor functional morphology and physiology that are typical of recent penguins. The next epoch, Eocene, was characterized by a remarkable morphological, taxonomic and ecological diversity of early Sphenisciformes. The most numerous penguin remains have been found in the Antarctic Peninsula. So far, four genera and ten species (excluding debatable taxa) have been described. During Eocene, the recognized range of this order expanded to Australia and South America (Argentina, Chile and Peru). Significant or dominant component of the fossil assemblages were species characterized by large body size, often clearly exceeding in this respect their modern relatives (fossil genera Anthropornis, Palaeeudyptes, Pachydyptes, Icadyptes and Inkayacu). The considerable body size was in some cases accompanied by intriguing, from a functional point of view, morphological features, e.g. within the wing skeleton of the Antarctic Anthropornis. Interestingly, the only penguin feather fossils (assignable to the Peruvian Inkayacu paracasensis) are Eocene in age. Climate change, particularly severe cooling at the Eocene/Oligocene boundary, may have led to the disappearance of penguins, for some 20 million years, from the known fossil record of Antarctic faunas. The actual nature of this hiatus remains unknown, however. Oligocene penguins are known almost exclusively from New Zealand.