The base of the new Lepidosauriformes illustrated to scale

Short one today, 
told mostly in pictures (Figs. 1, 2). Click here or see below for more data and taxon links.

These are the taxa from which all later lepidosaurs
arose and diversified. Thus, these are the ancestors of snakes, pterosaurs, ‘rib’ gliders and rhynchosaurs at their genesis and basal diversification.

Proximal outgroups
in the large reptile tree (subset Fig. 2) include Owenetta, Barasaurus and other small, low, wide owenettid lepidosauromorphs lacking an upper temporal fenestra.

Figure 1. Taxa at the base of the Lepidosauria include Paliguana, Tridentinosaurus, Lanthanolania, Lacertulus, Gephyrosaurus, Megachirella, Lacertulus and Palaegama.

Figure 1. Taxa at the base of the Lepidosauria include Paliguana, Tridentinosaurus, Lanthanolania, Lacertulus, Gephyrosaurus, Megachirella, Lacertulus and Palaegama. See figure 2 for a subset of the LRT.

Basal lepidosauriformes are rare.
For tens of millions of years, between the the first and last days of the Triassic, these are just about all we have in the sparse fossil record at the genesis of new Lepidosauriformes (= Paliguana + Sophineta, their last common ancestor and all descendants). Paliguana is a late survivor of that earlier genesis.

Figure 2. Subset of the LRT focusing on basal Lepidosauria. Taxa in colored blocks are shown to scale in figure 1.

Figure 2. Subset of the LRT focusing on basal Lepidosauria. Taxa in colored blocks are shown to scale in figure 1. Note: the chronology is not reflected in the phylogeny due to the rarity of fossil specimens.

Chronology does not always mirror phylogeny.
And that’s okay.

For instance:
It’s okay that Archaeopteryx was found in Late Jurassic strata and one of its its putative ancestor, Velociraptor, was found in Late Cretaceous strata. You might remember when a bunch of paleontologists waved their hands over that matter, then later blushed and said, “Never mind.” In like manner, it’s okay that Paliguana was found in younger strata than its phylogenetic descendants.


References
http://reptileevolution.com/owenetta.htm
http://reptileevolution.com/paliguana.htm
http://reptileevolution.com/lacertulus.htm

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