Calanguban, another basalmost scleroglossan squamate

Calanguban alamoi (Simoes, Caldwell and Kellner 2014, Early Cretaceous) was originally considered the oldest scincomorph, but in the large reptile tree (not updated yet) it nests with Liushusaurus (Fig. 1) at the base of the Scleroglossa. Due to the large size of its skull and orbit, this was considered an immature specimen. But all sisters are likewise tiny with a large orbit and short rostrum. So what we appear to see hear is yet another case of miniaturization at the base of a major clade.

Earlier we looked at Euposaurus another basal squamate, but at the base of the Iguania.

Figure 1. Liushusaurus (above) and Calanguban (below) to scale. Both nest at the base of the Scleroglossa, which makes them sisters to the basalmost tested iguanid, Iguana.

Figure 1. Liushusaurus (above) and Calanguban (below) to scale. Both nest at the base of the Scleroglossa, which makes them sisters to the basalmost tested iguanid, Iguana. 

References
Evans SE and Wang Y 2010. A new lizard (Reptilia: Squamata) with exquisite preservation of soft tissue from the Lower Cretaceous of Inner Mongolia, China.
Simoes TR, Caldwell MW and Kellner AWA 2014. A new Early Cretaceous lizard species from Brazil, and the phylogenetic postion of the oldest known South American squamates. Journal of Systematic Palaeontology. http://dx.doi.org/10.1080/14772019.2014.947342

wiki/Liushusaurus

Advertisements

6 thoughts on “Calanguban, another basalmost scleroglossan squamate

  1. I know I have made this comment multiple times but immature animals share plesiomorphic traits such as large eyes and short rostra. In phylogenetic analyses they appear unnaturally primitive and tend to group together. This has been shown experimentally with modern ontonogenic series. While some of these might be separate taxa we cannot use phylogenetic analyses to eliminate the hypothesis that they represent immature individuals. Using another technique, like PCA, would be more appropriate here. Parsimony-based phylogenetic analyses are powerful but are not the only tool out there and should not be used as a panacea.

  2. Tell me more about PCA. I am unfamiliar. On the plus side, I’m finding, and you will too, miniaturization at the base of nearly every major clade. It seems to be a pattern. Miniaturization typically involves neotony, hence the juvenile appearance. Short rostrum, large orbit retained, btw, in larger proximal descendant taxa. So they’re not outliers.

    • Principle Component Analysis – it can help quantify the major sources of variation. It can also help test to see if the large orbit in derived taxa is morphologically similar to the large orbits of juveniles.

  3. Thanks, Rob, I’ll take a good look at PCA. You should also note that larger ancestor taxa, like Langobardisaurus? rossii which I lovingly call “Renestosaurus” (http://www.reptileevolution.com/renestosaurus.htm) has a larger orbit and shorter rostrum. Similarly for the another ancestor taxon, Scandensia (http://www.reptileevolution.com/scandensia.htm) which is smaller, also has traditional juvenile traits. What phylogenetic analysis gives you is a clear picture that all proximal taxa have conventional “juvenile” traits. Now it is possible that these are all juveniles, but considering the rarity of finding true juveniles in the fossil record, and the fact that many other clades originated via miniaturization, I think it more parsimonious to go with the phylogenetic analysis ‘as is.’ That logic has solved many problems in the past, without an a priori assumption of the ontogenetic age.

  4. Until we get histology we can’t assume maturity on any specimen I think. Immature traits don’t always = immature animal. Both those things are absolutely critical to understand, I agree. The large number of these traits clustering at the bases of multiple clades is concerning, however.

  5. Let’s not forget that small taxa (birds, mammals) generally have a shorter lifespan, based on months or a few years, not decades. And your last comment I appreciate. Let’s look at all the options. I’m happy to defend my results. And also change my mistakes. In tomorrow’s blog you’ll see I’ve taken a wrong turn and just realized it, then fixed it.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s