Tertiary plotopterids (Aves, Plotopteridae) and a novel hypothesis on the phylogenetic relationships of penguins (Spheniscidae)

Plotopterids (Aves: Plotopteridae) are extinct wing-propelled diving birds which exhibit a strikingly similar wing morphology to penguins (Spheniscidae), but also share derived characters with 'pelecaniform' birds that are absent in penguins. The similarities between Plotopteridae and Spheniscidae have hitherto been attributed to convergence, and plotopterids were considered to be most closely related to the 'pelecaniform' Phalacrocoracidae (cormorants) and Anhingidae (anhingas). However, here I show that assignment of plotopterids to 'pelecaniform' birds does not necessarily preclude them from being the sister taxon of penguins. Cladistic analysis of 68 morphological characters resulted in sister group relationship between Plotopteridae and Spheniscidae, and the clade (Plotopteridae + Spheniscidae) was shown to be the sister taxon of the Suloidea, i.e. a clade including Sulidae (boobies and gannets), Phalacrocoracidae, and Anhingidae. Derived characters are discussed which support this novel hypothesis. Paedomorphosis probably accounts for the absence of derived characters in penguins that are shared by Plotopteridae and members of the Steganopodes. Plotopterids exemplify the importance of fossil birds for analyzing the phylogenetic relationships of modern taxa that exhibit a highly apomorphic morphology.     

Evolution of the brain and sensory organs in Sphenisciformes: new data from the stem penguin Paraptenodytes antarcticus

Penguins have undergone dramatic changes associated with the evolution of underwater flight and subsequent loss of aerial flight, which are manifest and well documented in the musculoskeletal system and integument. Significant modification of neurosensory systems and endocranial spaces may also be expected along this locomotor transition. However, no investigations of the brain and sensory organs of extinct stem lineage Sphenisciformes have been carried out, and few data exist even for extant species of Spheniscidae. In order to explore neuroanatomical evolution in penguins, we generated virtual endocasts for the early Miocene stem penguin Paraptenodytes antarcticus, three extant penguin species (Pygoscelis antarctica, Aptenodytes patagonicus, Spheniscus magellanicus), and two outgroup species (the common loon Gavia immer and the Laysan albatross Phoebastria immutabilis). These endocasts yield new anatomical data and phylogenetically informative characters from the brain, carotid arteries, pneumatic recesses, and semicircular canal system. Despite having undergone over 60 million years of evolution since the loss of flight, penguins retain many attributes traditionally linked to flight. Features associated with visual acuity and proprioception, such as the sagittal eminence and flocculus, show a similar degree of development to those of volant birds in the three extant penguins and Paraptenodytes antarcticus. These features, although clearly not flight‐related in penguins, are consistent with the neurological demands associated with rapid manoeuvring in complex aquatic environments. Semicircular canal orientation in penguins is similar to volant birds. Interestingly, canal radius is grossly enlarged in the fossil taxon Pa. antarcticus compared to living penguins and outgroups. In contrast to all other living birds, the contralateral anterior tympanic recesses of extant penguins do not communicate. An interaural pathway connecting these recesses is retained in Pa. antarcticus, suggesting that stem penguins may still have employed this connection, potentially to enhance directional localization of sound. Paedomorphosis, already identified as a potential factor in crown clade penguin skeletal morphology, may also be implicated in the failure of an interaural pathway to form during ontogeny in extant penguins. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166 , 202–219.     

Isolation and characterization of macaroni penguin (Eudyptes chrysolophus) microsatellite loci and their utility in other penguin species (Spheniscidae, AVES)

We report the characterization of 25 microsatellite loci isolated from the macaroni penguin (Eudyptes chrysolophus). Thirteen loci were arranged into four multiplex sets for future genetic studies of macaroni penguin populations. All 25 loci were tested separately in each of four other penguin species [Adélie penguin (Pygoscelis adeliae), chinstrap penguin (Pygoscelis antarctica), gentoo penguin (Pygoscelis papua) and king penguin (Aptenodytes patagonicus)]. Between eight and 12 loci were polymorphic per species. These loci are expected to be useful for studies of population genetic structure in a range of penguin species.     

Identification of land predators of African Penguins Spheniscus demersus through post-mortem examination

The African Penguin Spheniscus demersus is an endangered seabird endemic to southern Africa, and killing sprees by terrestrial predators have been one of the main threats for its mainland colonies. The methods employed to manage predators may differ depending on the species involved, therefore the implementation of strategies to limit the impacts of predation relies on the correct identification of the culprit predator. We report and quantify the lesions seen in African Penguins killed by four species of terrestrial predators: Caracal Caracal caracal (52 kills), Leopard Panthera pardus (27 kills), Domestic Dog Canis lupus familiaris (10 kills), and Cape Grey Mongoose Galerella pulverulenta (4 kills). We discuss patterns of necropsy findings that can be used to identify the predator species involved. Traditional forensic methods are useful tools to direct species-specific management actions for the conservation of the African Penguin and other seabirds so that effective mitigating measures can be deployed quickly to prevent further losses. It should be borne in mind, however, that the age, size and previous hunting experience of the predator are likely to influence the pattern of lesions that will be observed, and not all carcasses will have hallmark lesions or recognisable bite marks.     

Patterns of energy acquisition by a central place forager: benefits of alternating short and long foraging trips

In some seabirds, foraging trips have been defined as eitherlong or short, with the length of time spent traveling to theforaging area apparently a critical feature in determining foragingtrip length. Using logger technology, together with complimentarydata from published studies, we investigated traveling and foragingtimes in 18 free-living Adélie Penguins Pygoscelis adeliae,which were foraging for chicks. Most deep, foraging dives weredistributed around the center of the foraging trip. This centraltendency was particularly apparent if the cumulative amountof undulations in the depth profile (indicative of prey capture)was considered during deep dives; values started to increasebefore 20.9% and ceased after 67.2% of the dives had occurred.This concentration of the feeding activity in the middle ofthe foraging trip indicates that birds traveled to and froma prey patch whose location varied little over the birds' trips.These data form the basis for a simple model that uses travelingand foraging times together with projected rates of prey ingestionand chick and adult gastric emptying to determine that thereare occasions when, to optimize rates of prey ingestion whileat sea for both adults and chicks, birds should conduct foragingtrips of bimodal lengths.     

New data on the humerotriceps of penguins and its implications in the evolution of the fossa tricipitalis

A paddle-shaped wing, the general morphology of the humerus, and the muscles involved in wing movement are among the most characteristic adaptations to diving in penguins. Particularly, the humeral fossa tricipitalis and the musculus humerotriceps are clear examples of muscular rearrangement accompanying skeletal changes. In extant Spheniscidae, we were able to identify two heads of this muscle attaching within a different compartment of the bipartite fossa. Since the partition of the fossa appeared as a novelty during the Miocene, we propose that this might have had implications for underwater flight contributing to wing-propelled diving efficiency.