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Frogmouth evolution, plotopterid skulls, age of crown-group penguins



New papers on fossil birds that might be of interest to the list:

Mayr G 2015 Eocene fossils and the early evolution of frogmouths
(Podargiformes): further specimens of Masillapodargus and a comparison
with Fluvioviridavis. Palaeobio Palaeoenv
doi:10.1007/s12549-015-0200-5

New fossils of the podargiform _Masillapodargus longipes_ are
described from the early Eocene German fossil site Messel. Previously
unreported skeletal details of this species confirm its assignment to
Podargiformes (frogmouths), and especially the wing and pectoral
girdle bones exhibit close similarities to crown group Podargiformes.
Here, I show that the postcranial skeletal morphology of
_Masillapodargus_ is quite different from that of the early Eocene
North American taxon _Fluvioviridavis_, for which podargiform
affinities were recently proposed. With regard to the morphologies of
the humerus and the coracoid, _Fluvioviridavis_ more closely resembles
Steatornithiformes (oilbirds). These may be plesiomorphic
similarities, if Steatornithiformes and Podargiformes are sister taxa
as recently suggested. Both podargiform affinities of
_Fluvioviridavis_, as well as a sister group relationship between
Podargiformes and Steatornithiformes, are, however, only weakly based.
A well-founded classification of _Fluvioviridavis_ depends on a better
understanding of the basal divergences within extant Strisores, the
clade including "caprimulgiform" and apodiform birds, which remain
controversial.

Mayr G, Goedert JL, Vogel O 2015 Oligocene plotopterid skulls from
western North America and their bearing on the phylogenetic affinities
of these penguin-like seabirds. J Vert Paleont e943764

Plotopterids are penguin-like, wing-propelled birds with controversial
phylogenetic affinities. They are usually regarded as closely related
to Suloidea (gannets, cormorants, and allies), with the penguin-like
features considered to be of convergent origin. However, it has also
been proposed that the similarities shared by plotopterids and
penguins are due to common ancestry. An in-depth assessment of
plotopterid affinities has been hampered by the fact that very little
data about the skull of these birds were available. New fossils of
_Tonsala_ from the Oligocene Pysht Formation in Washington State
(U.S.A.) include the first well-preserved cranial remains of this
taxon. They show that although plotopterids share derived cranial
features with members of Suloidea that are absent in species of
Sphenisciformes (penguins), they lack diagnostic derived features of
the representatives of crown group Suloidea. To assess the affinities
of plotopterids, we performed a phylogenetic analysis that included,
for the first time, early stem group representatives of
Sphenisciformes, resulting in a sister-group relationship between
Plotopteridae and Suloidea. Intriguingly, however, our reanalysis of
the emended data of a more comprehensive recent analysis that
supported a position of Plotopteridae within Suloidea recovered a
sister-group
relationship between Plotopteridae and Sphenisciformes. Although
cranial morphology challenges the hypothesis of close affinities
between plotopterids and penguins, more data on early stem lineage
representatives of penguins are needed for a robust placement of
Plotopteridae relative to Sphenisciformes.


The paper on the origin of crown-group penguins uses Bayesian tip
dating with a modification of the Fossilized Birth-Death (FBD) tree
process prior which, for the first time, allows some of the analyzed
fossils to be ancestors of other taxa rather than tips. (The model was
first introduced by Gavryushkina et al. 2014.) Figures 1 and 4 are
particularly interesting in this regard: according to the former,
_Waimanu manneringi_ (the oldest known stem-penguin) has a posterior
probability of up to 80% of being a direct ancestor of later penguins
(depending on the model used), and according to the latter, there is
"positive evidence" (log(Bayes factor) > 1) for several other taxa
being sampled ancestors instead of tips.

Gavryushkina A, Heath TA, Ksepka DT, Stadler T, Welch D, Drummond AJ
2015 Bayesian total evidence dating reveals the recent crown radiation
of penguins. arXiv:1506.04797v1 [q-bio.PE], June 15
http://arxiv.org/pdf/1506.04797v1.pdf (free pdf)

The total evidence approach to divergence-time dating uses molecular
and morphological data of extant and fossil species to infer
phylogenetic relationships, species divergence times, and
macroevolutionary parameters in a single coherent framework. Current
model-based implementations of this approach lack an appropriate model
for the tree describing the diversification and fossilisation process
which can result in erroneous conclusions. We address this shortcoming
by providing a total evidence method implemented in a Bayesian
framework. This approach uses a mechanistic tree prior to describe the
underlying diversification process that generated the tree of extant
and fossil taxa. Previous attempts to apply the total-evidence
approach have used tree priors that do not account for the possibility
that fossil samples may be direct ancestors of other samples, that is,
ancestors to fossil or extant species or to clades. The fossilised
birth-death process explicitly models the diversification,
fossilisation, and sampling processes and naturally allows for sampled
ancestors. This model was recently applied to estimate divergence
times based on molecular data and fossil occurrence dates. We
incorporate the fossilised birth-death model and a model of
morphological trait evolution into a Bayesian total-evidence approach
to dating species phylogenies. We apply this method to extant and
fossil penguins and show that the modern penguins radiated much more
recently than has been previously estimated, with the basal divergence
in the crown clade occurring at ∼12.5 Ma and most splits leading to
extant species occurring in the last 2 million years. Our results
demonstrate that including stem-fossil diversity can greatly improve
the estimates of the divergence times of crown taxa. The method is
available in BEAST2 (version 2.3) software www.beast2.org with
packages SA (version 1.1.3) and morph-models (version 1.0.1)
installed.

*Ref:*

Gavryushkina A, Welch D, Stadler T, Drummond AJ 2014 Bayesian
inference of sampled ancestor trees for epidemiology and fossil
calibration. PLoS Comp Biol 10(12): e1003919

-- 
David Černý