1
$\begingroup$

What is the logic behind Archosauria being a subclass when they have such major differences between Lizards, Snakes, and Turtles. The Amphibians appeared before the Diapsids, which then split into Synapsids and Sauropsids, so classes aren't just based on time of origin. Archosauria have many skeletal and morphological features that separate them from Lepidosaurs as much as Lepidosaurs were separated from synapsids.

Maybe I am just missing something but I can't find the reasoning behind Archosauria not being classified unique from Lepidosauria in the same way. The more I learn the more it seems like the Tetrapod classes should be Synapsids, Amphibians, Lepidosauria and Archosauria.

P.S. Please help me clarify this question. I have spent a long time on this but I don't think I'm being very clear. I can't think of the correct way to word this at all. It feels garbled and all over the place.

$\endgroup$
1
  • 4
    $\begingroup$ The phylogenetic labels like class, order, family, etc are fairly outdated and not meaningful. All that is important is the hierarchy, the specific level and number of levels is arbitrary and highly biased to the humans that labeled them. $\endgroup$
    – Bryan Krause
    Commented May 6 at 23:06

1 Answer 1

4
$\begingroup$

See Bryan Krause's comment, but I'll add that the reason is historical. Linnaeus identified three classes of tetrapods (mammals, birds, and reptiles/amphibians), and reptiles and amphibians were later split into their own classes. This was all before Darwin, so classes were defined based on morphological similarity, and not evolutionary relationships. When taxonomists started defining groups based on phylogeny, they tried to preserve Linnaeus's ranks of kingdom, phylum, class, order, family, and genus, even though they're arbitrary. So the classes you suggest would probably make more sense, but we keep the old ones for historical reasons. In fact, the clade Aves is usually considered a class, even though it lies within Archosauria, within the class Reptilia! This is one of the few exceptions to the rule that you can't have a class inside a class (or order inside an order, etc.). No, it doesn't make sense, but try telling an ornithologist that Aves is now a "superorder".

$\endgroup$
1
  • $\begingroup$ Thank you, I thought it was just me. It makes me wonder if the entire classifications system will be reworked the same way planet classification was back with pluto. $\endgroup$ Commented May 24 at 14:21

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .