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Dinosaurs Lived with Protoratites and Primates



From: Ben Creisler bh480@scn.org

A couple of recent news stories not strictly about 
dinosaurs might be of interest since they relate Mesozoic 
geography to theories on the evolution of ratites and 
primates. I have included the original refs with abstracts.

Dinosaur extinction grounded ancient birds
http://www.physorg.com/news183297127.html

Ref:
Matthew J. Phillips, Gillian C. Gibb, Elizabeth A. Crimp, 
and David Penny 
Tinamous and Moa Flock Together: Mitochondrial Genome 
Sequence Analysis Reveals Independent Losses of Flight 
among Ratites 
Systematic Biology 2010 59: 90-107 

Ratites are large, flightless birds and include the 
ostrich, rheas, kiwi, emu, and cassowaries, along with 
extinct members, such as moa and elephant birds. Previous 
phylogenetic analyses of complete mitochondrial genome 
sequences have reinforced the traditional belief that 
ratites are monophyletic and tinamous are their sister 
group. However, in these studies ratite monophyly was 
enforced in the analyses that modeled rate heterogeneity 
among variable sites. Relaxing this topological constraint 
results in strong support for the tinamous (which fly) 
nesting within ratites. Furthermore, upon reducing base 
compositional bias and partitioning models of sequence 
evolution among protein codon positions and RNA 
structures, the tinamouâ??moa clade grouped with kiwi, emu, 
and cassowaries to the exclusion of the successively more 
divergent rheas and ostrich. These relationships are 
consistent with recent results from a large nuclear data 
set, whereas our strongly supported finding of a tinamouâ??
moa grouping further resolves palaeognath phylogeny. We 
infer flight to have been lost among ratites multiple 
times in temporally close association with the Cretaceousâ??
Tertiary extinction event. This circumvents requirements 
for transient microcontinents and island chains to explain 
discordance between ratite phylogeny and patterns of 
continental breakup. Ostriches may have dispersed to 
Africa from Eurasia, putting in question the status of 
ratites as an iconic Gondwanan relict taxon. 


Keywords: Base composition; flightless; Gondwana; 
mitochondrial genome; Palaeognathae; phylogeny; ratites
---------
New Theory on the Origin of Primates
http://www.sciencedaily.com/releases/2010/01/100119154710.h
tm

Ref:
Michael Heads. 2009. Evolution and biogeography of 
primates: a new model based on molecular phylogenetics, 
vicariance and plate tectonics (p).
ABSTRACT
The ages of the oldest fossils suggest an origin for 
primates in the Paleocene (~56 Ma). Fossil-calibrated 
molecular clock dates give Cretaceous dates (~80â??116 Ma). 
Both these estimates are minimum dates although they are 
often 'transmogrified' and treated as maximum or absolute 
dates. Oldest fossils can underestimate ages by tens of 
millions of years and instead of calibrating the time-
course of evolution with a scanty fossil record, the 
geographical boundaries of the main molecular clades of 
primates are calibrated here with radiometrically dated 
tectonic events. This indicates that primates originated 
when a globally widespread ancestor (early Archonta) 
differentiated into a northern group (Plesiadapiformes, 
extinct), a southern group (Primates), and two south-east 
Asian groups (Dermoptera and Scandentia). The division 
occurred with the breakup of Pangea in the Early Jurassic 
and the opening of the central Atlantic (~185 Ma). Within 
primates, the strepsirrhines and haplorhines diverged with 
volcanism and buckling on the Lebombo Monocline, a 
volcanic rifted margin in south-east Africa (Early 
Jurassic, ~180 Ma). Within strepsirrhines, lorises and 
galagos (Africa and Asia) and lemurs (Madagascar) diverged 
with the formation of the Mozambique Channel (Middle 
Jurassic, ~160 Ma). Within haplorhines, Old World monkeys 
and New World monkeys diverged with the opening of the 
Atlantic (Early Cretaceous, ~130 Ma). The main aspects of 
primate distribution are interpreted as the result of 
plate tectonics, phylogeny and vicariance, with some 
subsequent range expansion leading to secondary overlap. 
Long-distance, trans-oceanic dispersal events are not 
necessary. The primate ancestral complex was already 
widespread globally when sea-floor spreading, strike-slip 
rifting and orogeny fractured and deformed distributions 
through the Jurassic and Cretaceous, leading to the origin 
of the modern clades. The model suggests that the topology 
of the phylogenetic tree reflects a sequence of 
differentiation in a widespread ancestor rather than a 
series of dispersal
events.