The phylogeny of the living and fossil Sphenisciformes (penguins)

Abstract

We present the first phylogenetic analysis of the Sphenisciformes that extensively samples fossil taxa. Combined analysis of 181 morphological characters and sequence fragments from mitochondrial and nuclear genes (12S, 16S, COI, cytochrome b, RAG-1) yields a largely resolved tree. Two species of the New Zealand Waimanu form a trichotomy with all other penguins in our result. The much discussed giant penguins Anthropornis and Pachydyptes are placed in two clades near the base of the tree. Stratigraphic and phylogenetic evidence suggest that some lineages of penguins attained very large body size rapidly and early in the clade's evolutionary history. The only fossil taxa that fall inside the crown clade Spheniscidae are fossil species assigned to the genus Spheniscus. Thus, extant penguin diversity is more accurately viewed as the product of a successful radiation of derived taxa than as an assemblage of survivors belonging to numerous lineages. The success of the Spheniscidae may be due to novel feeding adaptations and a more derived flipper apparatus. We offer a biogeographical scenario for penguins that incorporates fossil distributions and paleogeographic reconstructions of the Southern continent's positions. Our results do not support an expansion of the Spheniscidae from a cooling Continental Antarctica, but instead suggest those species that currently breed in that area are the descendants of colonizers from the Subantarctic. Many important divergence events in the clade Spheniscidae can instead be explained by dispersal along the paths of major ocean currents and the emergence of new islands due to tectonic events.

Penguin heat-retention structures evolved in a greenhouse Earth

“…have been recovered only in the Palaeocene of New Zealand. Following the evolution of the humeral plexus, morecrownward penguin taxa spread rapidly to localities around the Gondwanan rim and later dispersed across wide swathes of open ocean [14,15,21,22]. We suggest that the evolution of the CCHE preceded, and probably played a major role, in Eocene phylogenetic radiations and dispersal events within Sphenisciformes, leading to trans-oceanic invasion of high latitudes.…”

“…Rather, the CCHE appears to have evolved in concert with dramatic skeletal modifications in Early Palaeogene stem penguins-changes that promoted neutral buoyancy and drag reduction, and thus improved long-distance swimming and deep-diving. Of note are the rapid evolution of large body size, osteosclerotic (densely thickened) limb bones related to buoyancy regulation and a hydrofoil wing with a compressed (fusiform) cross section, a semi-rigid elbow, and a relatively high surface area to volume ratio [13][14][15]21]. Indeed, the humeral arterial sulcus enables the blood vessels of the plexus to be drawn flush with the surface of the bone to preserve the hydrofoil profile of the wing.…”

African penguins (Spheniscus demersus) can detect dimethyl sulphide, a prey-related odour

“…Although less is known about the sensory ecology of foraging penguins, hunting by smell is likely in this group for a variety of reasons. Firstly, penguins are the closest relatives to the procellariiforms [see Ksepka et al (Ksepka et al, 2006) and references therein] and, similar to procellariiform adults, their chicks have a tube-nose (Kinsky, 1960). Thus, it seems logical to predict that penguins also have a functioning sense of smell, particularly in light of recent evidence (Van Buskirk and Nevitt, 2008) that suggests that DMS behavioural sensitivity is ancestral in the procellariiforms.…”

“…Penguins (Sphenisciformes) and procellariiforms (albatrosses and petrels) are phylogenetically closely related (Ksepka et al, 2006;Hackett et al, 2008) and share many common traits with respect to their foraging behaviour. For example, species within these two broad groups tend to forage on similar types of prey, such as krill, fish and squid, and exploit similar ocean habitats (for reviews, see Warham, 1990;Williams, 1995).…”

Distinguishing between two Antarctic species of Eocene Palaeeudyptes penguins: a statistical approach using tarsometatarsi

“…The genus Palaeeudyptes is unique among the Paleogene Sphenisciformes and this well−deserved term has its roots in several circumstances, most importantly: (i) it is the earliest erected taxon of fossil penguins (Huxley 1859), (ii) hundreds of re− mains that have been assigned to this genus are intriguingly widespread, both in space (Antarctica, Australia, New Zealand, South America) and time (Eocene, Oligocene), and (iii) its monophyly has been recently most vigorously contested (e.g., Ksepka et al 2006 andClarke et al 2007). Type specimens of all but one member species, i.e.…”