Morphological dating

[David Marjanovic <david.marjanovic@gmx.at>]

In analogy to molecular dating, the following SVP meeting abstract presents 
the idea of using morphological data for deriving divergence date estimates.

My thesis supervisor had the same idea; we'll put it into my thesis, but we 
won't be able to sell it as new anymore.

And in case anyone wonders, I'm a touch-typist :o)

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Thomas DeCecchi & Hans Larsson: Tempos and modes of theropod evolution, p. 
67A

Genomic clocks, a method [sic] for dating lineage divergences through the 
steady regular accumulations of sequence mutations, has become a standard 
tool in evolutionary biology[,] yet is of limited use in paleontology. 
Genomic information is generally absent in fossils but a large amount of 
data is preserved in skeletal morphology. We present a novel method that 
estimate[s] a "morphological clock" to examine divergence times within 
Theropoda. Origination times for major clades of theropods are calculated 
using a recent large and broad-ranging data set from [the book] "The 
Dinosauria" and grounded with known geological times for specimens. This 
method has also been extended to predict the origin of theropods and can, 
when combined with traditional "relative" rate measurements, allow for 
comparisons between different evolutionary trajectories within Theropoda. 
The results presented give the first insight into absolute evolutionary 
rates within theropod evolution. They provide data for the evaluation of 
modular evolutionary rates across the skeleton and transformational 
evolutionary modes across the lineage. Using this method we have determined 
the origin of Theropoda at during the Late [sic] Anisian, 5 -- 7 million 
years before the [Carnian] Ischigualasto fauna, a date consistent with other 
estimates of theropod origins. Our data shows that at Eumaniraptora 
(Deinonychosaurians + Aves) there is a noted increase in the rate of 
character evolution coincident with the origin of flight, especially in the 
pectoral region. Beginning at the node Eumaniraptora a separate 
morphological clock using a different calibration points [sic] is proposed 
to estimate early avian divergence times, since this increase in character 
rate evolution during this transition is not adequately modeled by the 
general theropod trend.