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Rooies Plesiomorphic basically refers to an ancestral (primitive) character state with reference to another derived state. In other words an anatomical trait that is found at the base of a lineage.

Thought about it some more and agree with the answer (nice question by the way!), only there are hundreds of plesiomorphs.

Simply said it is the original character of a branching phyletic lineage, found in the ancestral forms.

To put it differently: It represents the most primitive state of the evolution relative to another organism.



Correct Odessy. Only this question was directly about the Plesiomorph form of the Archaeopteryx lithographica

Thank you, you clever lot But was the way of flying different from our present birds?

The oldest and most primitive form of whatever can be called plesiomorph.

Some background info to the term:

During the 1950’s and1960’s three competing theories of classification came up:

a. Phenetic systematics (Phenetics): Organisms are classified, according to this theory, on the basis of “overall similarity”. Similarity is calculated from the presence or absence of numerous unweighted characters or character states . This method does not establish groups by inspection, but orders the lowest taxonomic units (usually species) into groups with the help of standardized procedures.
b. Cladistic systematics (Cladistics) Organisms are classified and ranked, according to this theory, exclusively on the basis of “recency of common descent”. Membership of species in taxa is recognized by the joint possession of derived (“apomorphous”) characters. Grouping and ranking are given simultaneously by the branching points.
c. Evolutionary systematics: Organisms are classified and ranked, according to this theory, on the basis of two sets of factors, 1. phylogenetic branching (“recency of common descent”, retrospectively defined), and 2. amount and nature of evolutionary change between branching points. The latter factor, in turn, depends on the evolutionary history of a respective branch, e. g., whether or not it has entered a new adaptive zone and to what extent it has experienced a major radiation.

Cladistics consists of two quite different sets of operations:
1. the reconstruction of the branching pattern of phylogeny through cladistic analysis,
2. the construction of a cladistic classification based on this branching pattern.
The most important step in the cladistic analysis is the attempt to separate characters into ancestral (plesiomorphous) and derived (apomorphous) characters.
The following terms are used to identify shared or distinct characters among groups:
• Plesiomorphy ("close form") or ancestral state, also symplesiomorphy ("shared plesiomorphy", i.e. "shared close form"), is a characteristic that is present at the base of a tree (cladogram). Since a plesiomorphy that is inherited from the common ancestor may appear anywhere in a tree, its presence provides no evidence of relationships within the tree.
• Apomorphy ("separate form") or derived state is a characteristic believed to have evolved within the tree. It can thus be used to separate one group in the tree from the rest. Within the group which shares the apomorphy it is a synapomorphy ("shared apomorphy", i.e. "shared separate form").

My conclusion: Plesiomorphic flight (if the term exists) is another term for primitive flight, but not a form of flight.

I think it's the African Jacana, now to check up on what the breeding system is called.

Polyandrous rings a bell.

Correct Sprocky

Thanks Rooies. Most guests are very suprised when you tell them about this.

Here is a question in the same format as your previous one...

Birds that heavily rely on their beaks for foraging have bill tips and tongues that are densely packed with receptors called ________ _______. These receptors are sensitive to both taste and touch and allow birds like Storks to locate food under water purely by touch.

Herbst corpuscles

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Spot on forestgump! Take IT away!

Cormorant?

not cormorant, my bird is named because of this behaviour

Dipper?