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paleo-penguin paper



HI ALL:
 I saw this on another listserver and thought it might be on interest:

Ksepka, Daniel T., and Julia A. Clarke  2010.  The basal penguin (Aves:
Sphenisciformes) *Perudyptes devriesi* and a phylogenetic evaluation of
the
penguin fossil record.  Bulletin of the American Museum of Natural
History,
337: 1-77.

Can be downloaded from:
http://digitallibrary.amnh.org/dspace/handle/2246/6065

Abstract: We present the first detailed description of *Perudyptes
devriesi*,
a basal penguin from the middle Eocene (~42 Ma) Paracas Formation of Peru,
and a new analysis of all published extinct penguin species as well as
controversial fragmentary specimens. The *Perudyptes devriesi* holotype
includes key regions of the skull and significant postcranial material,
thus
helping to fill a major phylogenetic and stratigraphic (~20 million year)
gap between the earliest fossil penguins (*Waimanu manneringi* and
*Waimanu
tuatahi*, ~5861.6 Ma) and the next oldest partial skeletons. *Perudyptes
devriesi* is diagnosable by five autapomorphies: (1) an anteroventrally
directed postorbital process, (2) marked anterior expansion of the
parasphenoid rostrum, (3) posterior trochlear ridge of the humerus
projecting distal to the middle trochlear ridge and conformed as a large,
broadly curved surface, (4) convex articular surface for the
antitrochanter
of the femur, and (5) extremely weak anterior projection of the lateral
condyle of the tibiotarsus. The skull of *Perudyptes* is characterized by
deep temporal fossae and an elongate, narrow beak that differs from other
reported stem penguins in its short mandibular symphysis. The wing
skeleton
of *Perudyptes* preserves a combination of plesiomorphic features also
observed in the basal penguin *Waimanu* and derived features shared with
more crownward penguins. Features of the wing optimized as primitive for
Sphenisciformes include retention of a discrete dorsal supracondylar
tubercle on the humerus and presence of a modestly projected pisiform
process on the carpometacarpus. Derived features present in *Perudyptes*
and
all more crownward penguins, but absent in *Waimanu*, include a more
flattened humerus, development of a trochlea for the tendon of m.
scapulotriceps at the distal end of the humerus, and bowing of the
anterior
face of the carpometacarpus.

A combined molecular and morphological dataset for Spheniciformes was
expanded by adding 25 osteological and soft tissue characters as well as
11
taxa. In agreement with previous results, *Perudyptes devriesi* is
identified as one of the most basal members of Sphenisciformes. This
analysis also confirms the placement of the middle/late Miocene (~1113 Ma)
fossil *Spheniscus muizoni* as a member of the *Spheniscus* clade and
places
the late Miocene (~10 Ma) *Madrynornis mirandus* as sister taxon to extant
*
Eudyptes*. These two species, known from relatively complete partial
skeletons, are the oldest crown clade penguin fossils and represent
well-corroborated temporal calibration points for the *Spheniscus*-*
Eudyptula* divergence and *Megadyptes*-*Eudyptes* divergence,
respectively.
Our results reaffirm that the Miocene penguin taxon *Palaeospheniscus*,
recently proposed to represent a member of the crown radiation, belongs
outside of the crown clade Spheniscidae.

The phylogenetic positions of small Eocene Antarctic penguin taxa (*
Delphinornis*, *Marambiornis*, and *Mesetaornis*) recently proposed as
possible direct ancestors to crown Spheniscidae were further evaluated
using
alternate coding strategies for incorporating scorings from isolated
elements that preserve critical morphologies and are thought to represent
these taxa, although they cannot yet be reliably assigned to individual
species. Under all scoring regimes, *Delphinornis*, *Marambiornis*, and *
Mesetaornis* were recovered as distantly related to Spheniscidae.

Using synapomorphies identified in the primary analysis, we evaluated the
phylogenetic position of fragmentary specimens, including the holotypes of
valid but poorly known species, specimens currently unassignable to the
species level, and morphologically distinct specimens that have not yet
been
named. All pre-Miocene specimens can be excluded from Spheniscidae based
on
presence of plesiomorphies lost in all crown penguins, consistent with a
recent radiation for the penguin crown clade. This study provides
additional
support for a scenario of penguin evolution characterized by an origin of
flightlessness near the K-T boundary, dispersal throughout the Southern
Hemisphere during the early Paleogene, and a late Cenozoic origin for the
crown clade Spheniscidae. Stratigraphic distribution and phylogenetic
relationships of fossil penguins are consistent with distinct radiations
during the Eocene, Oligocene, and Miocene. While the Eocene and Oligocene
penguin faunas are similar in many respects, the Miocene fauna is
characterized by smaller average size and novel cranial morphologies,
suggesting that an ecological shift in diet occurred close to the origin
of
crown Spheniscidae.

-- 

Ian Paulsen
Bainbridge Island, WA, USA
" Which just goes to show that a
  passion for books is extremely unhealthy."
 from Cornelia Funke's "Inkheart".