Palaeospheniscus patagonicus(Aves, Sphenisciformes): new discoveries from the Early Miocene of Argentina

Abstract

The penguin skeleton studied here constitutes the fourth partial skeleton found in Patagonia, and the third one with an associated humerus and tarsometatarsus. The finding of this partial skeleton identified with certainty asPalaeospheniscus patagonicusMoreno and Mercerat, 1891 (Aves, Sphenisciformes) allows the first description of elements other than the tarsometatarsus. The material comes from the basal sector of the Gaiman Formation (Early Miocene), located along the Atlantic coast of Chubut Province, south of Rawson city. This unit comprises a succession of shales, fine tuffs, sandstones, tuffaceous sandstones, and coquinas deposited in a shallow marine environment. These beds contain abundant marine vertebrates (sharks, dolphins, rays, birds), mollusk casts, and oyster beds. The skeleton includes: rostrum, two thoracic vertebrae, right coracoid without the distal end, left humerus, right femur, right tarsometatarsus, left fragmentary scapula, left coracoid, left radius without the distal end, proximal portion of left ulna, proximal end of left femur, and preacetabular part of the synsacrum.P. patagonicuswould have been a medium-sized penguin weighing about 5 kg that inhabited the breeding colonies established in the nearby Bryn Gwyn area during the early Miocene. Despite the abundance of penguin remains known for Argentina, and the fact that they are among the birds with a better fossil record, this skeleton is an exceptional case. This finding allows a readjustment of the taxonomic criteria applicable to fossil and living species.

The Basal Penguin (Aves: Sphenisciformes) Perudyptes devriesi and a Phylogenetic Evaluation of the Penguin Fossil Record

“…Undescribed material of the Oligocene taxon Platydyptes preserves an elongate, narrow beak (referenced in Slack et al, 2006), and a recently reported partial beak of the Miocene taxon Palaeospheniscus patagonicus resembles those of modern shortbeaked penguins (Acosta Hospitaleche et al, 2008). Current evidence is thus consistent with the first acquisition of a short-beaked skull type occurring by the Miocene in clade 11, close to the origination of Spheniscidae.…”

“…In contrast, Acosta Hospitaleche et al ( , 2008 placed Palaeospheniscus within the crown clade, as sister taxon to extant Aptenodytes. Although Acosta Hospitaleche et al (2008) commented that Bertelli et al (2006) pro- The incorporation of 12 vertebrae into the synsacrum of Palaeospheniscus bergi (see Simpson, 1946) may also represent a primitive feature given that the most basal known penguin, Waimanu manneringi, possesses 11 synsacral vertebrae and extant penguins typically possess 13 synsacral vertebrae. We observed 14 synsacral vertebrae in Pygoscelis papua and some exemplars of Eudyptes robustus, and 12 synsacral vertebrae in Eudyptula minor (these totals are optimized as apomorphic increases/decreases on our strict consensus tree).…”

“…In the present study, we modified Ksepka's (2007) version of this matrix, including 25 morphological characters and 11 fossil taxa added since the most recent published version of the matrix (Clarke et al, 2007). In addition to increasing taxonomic sampling, we were also able to incorporate additional codings for Palaeospheniscus biloculata based on new material reported by Acosta and for Palaeospheniscus patagonicus based on new material reported by Acosta Hospitaleche et al (2008). The current dataset contains 219 morphological characters and .6000 bp of sequence data.…”

“…Madrynornis mirandus, one of the most complete fossil penguins yet discovered, was previously identified as the sister taxon of extant Eudyptes by Acosta Hospitaleche et al ( , 2008. However, these authors reported a significantly different phylogeny ( fig.…”

“…Exclusion of .100 osteological and soft tissue characters from previous studies that could not be scored in sampled fossil taxa (Paraptenodytes, Palaeospheniscus, and Madrynornis) from the analyses of Acosta Hospitaleche et al ( ,2008 may account for some differences in topology. Rather than improving accuracy or resolution, exclusion of characters with missing data is likely to reduce accuracy (e.g., Wiens, 1998).…”