Kotatsu
Phthirapterist
Please ignore this post:
On the extreme off-chance that Old Bob is trained in systematics, I would like to point out that from a systematic point of view, stating that a character is typical of a certain group (normally a species or so) does not mean either that all members of the group have to have the feature, nor that all individuals that have the feature is a member of that group.
For instance, Spoonbills (Ciconiiformes: Threskiornithidae: Platalea spp.) typically have black, spatulate bills (1), yet the Spoonbilled Sandpiper (Charadriformes: Scolopacidae: Eurynorhynchus pygmaeus) has a black, spatulate bill but is not a member of the Spoonbills. Conversely, I believe Limnodrilus worms (Clitellata: Tubificidae) typically have bifid setae (2), but in Limnodrilus falciformis they are unifid (3).
This would invalidate many comments made here if it wasn't for the fact that Old Bob is just talking rubbish. I would not have made this comment were it not for the fact that I have seen similar statements made before, particularly in threads debating the existence or non-existence of human races. The same feature may be diagnostic for several groups, if they together form a subgrouping within a larger group. Obversely, they may be features undergoing parallel evolution, but still be diagnostic due to rarity within the larger group.
There. I have done my pedantry for today and can reward myself with some gingerbread!
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(1) That is, it is shaped like a spoon.
(2) That is, the bristles are divided into two "teeth" in the far end, one typically considerably smaller than the other.
(3) That is, not divided at the tip.
On the extreme off-chance that Old Bob is trained in systematics, I would like to point out that from a systematic point of view, stating that a character is typical of a certain group (normally a species or so) does not mean either that all members of the group have to have the feature, nor that all individuals that have the feature is a member of that group.
For instance, Spoonbills (Ciconiiformes: Threskiornithidae: Platalea spp.) typically have black, spatulate bills (1), yet the Spoonbilled Sandpiper (Charadriformes: Scolopacidae: Eurynorhynchus pygmaeus) has a black, spatulate bill but is not a member of the Spoonbills. Conversely, I believe Limnodrilus worms (Clitellata: Tubificidae) typically have bifid setae (2), but in Limnodrilus falciformis they are unifid (3).
This would invalidate many comments made here if it wasn't for the fact that Old Bob is just talking rubbish. I would not have made this comment were it not for the fact that I have seen similar statements made before, particularly in threads debating the existence or non-existence of human races. The same feature may be diagnostic for several groups, if they together form a subgrouping within a larger group. Obversely, they may be features undergoing parallel evolution, but still be diagnostic due to rarity within the larger group.
There. I have done my pedantry for today and can reward myself with some gingerbread!
---
(1) That is, it is shaped like a spoon.
(2) That is, the bristles are divided into two "teeth" in the far end, one typically considerably smaller than the other.
(3) That is, not divided at the tip.