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Re: [dinosaur] Dinosaur evolution at work



On Mon, Aug 24th, 2020 at 5:55 PM, Poekilopleuron <dinosaurtom2015@seznam.cz> 
wrote:

> Good day again! Thanks to everyone who responded to my previous queries. I
> have another one, concerning the evolutionary processes in dinosaurian
> lineages. I would like to ask, if there is a clear evolutionary lineage of
> certain dinosaur groups (most likely ceratopsians or hadrosaurids), in which
> we can observe the evolutionary processes at work. In other words, is there a
> clear hereditary lineage of at least a few million years, supported by both
> morphology and dating of sediments in which they are preserved? For example
> Einiosaurus - Achelousaurus - Pachyrhinosaurus comes to mind here... Thank
> you in advance! Tom

Determining direct ancestor-descendant relationships between fossils with any 
degree of certainty is next 
to impossible. It's likely that entire species are missing from the fossil 
record due to the unlikeliness of 
fossilisation, or the complete loss of such fossils in the intervening time due 
to erosion.

Fossil relationships are mostly determined by bone morphology in the absence of 
sufficiently long (or 
usually any) DNA sequences. There is no way to be confident that similarities 
in bone morphology are due 
to heredity rather than parallel evolution. Even if those morpholgical 
similarities were due to genetic 
relationships, you can't be sure whether those shared genes represent a direct 
ancestor-descendant 
relationship, or whether those related species had a common ancestor that 
branched off into entirely 
separate lineages.

-- 
Dann Pigdon