ReptileEvolution.com is a website devoted to presenting the family tree of the Reptilia, illustrating its members and nesting their relationships to one another using phylogenetic analysis. A study of this scope has not been attempted or published before. New taxa are added weekly, so this is a study without end. The web is an ideal medium for this attempt. New papers can be promoted and prior mistakes can be rectified without the delays and deadlines of paper publication.
This website is the product of collaboration. This site would not have been possible without the hundreds of paleontologists, preparators, paleoartists and editors who have discovered, exposed, reconstructed and published the taxa presented here. Most of the data here comes from their published papers and prepared specimens.
This website is all about the big picture. No one has ever put together a phylogenetic analysis sampling the entire reptile family tree until now. Many smaller studies made mistakes by excluding important taxa and including unrelated taxa. These mistakes could only have been recognized in a more inclusive study such as this one.
This website is a work in progress. It will be added to, refined and culled as necessary in order to be as right as possible, echoing the natural order of evolution. As more data is published by today's paleontologists, the tree will continue to grow.
Nearly every novel nesting here is the result of expanding the taxon list.In prior smaller studies too much reliance was placed on tradition and past paradigms. Here more taxa produce more possible nesting sites and sometimes they are filled with little surprises.
Sometimes I'm wrong. Sometimes others are wrong. Most of the discoveries herein were made simply by expanding the taxon list. In other cases purported autapomorphies turned out to be misinterpretations (exemplified by my published mistakes with Cosesaurus and Sharovipteryx). If you find misinterpretations here, or new data becomes available, please contact me. It's more important to get it right than to be right. Credit will be given! Criticisms without evidence will be ignored or exposed as fraud.
I often use my computer screen as my microscope, replacing the traditional microscope and camera lucida. That gives a big flat view that enables subtle lines to be identified over an extremely wide view. In this age of pdfs and jpegs examining jpegs is a common practice when sharing data (and it saves on costly jet fuel). I digitally trace images using a software program called Adobe Photoshop. Referees have claimed that I manipulate images, which is false with regard to shapes and details. I only adjust contrast. Here you'll see several examples of the benefits of Photoshop using DGS or Digital Graphic Segregation, such as the skull of Jeholopterus or the contents of the three pterosaur eggs. You may not be able to "see" all the detail I present. Observation and identification takes practice and experience. Sometimes I don't "see" something until the photo is turned off and the tracing remains. On crushed two-dimensional fossils, DGS enables one to trace by line or color every element in the fossil, segregating on separate digital layers ribs from gastralia from forelimbs from vertebrae, etc. Segregation and color coding helps reduce the apparent chaos of "road-kill" fossils and enables one to create reconstructions that can be understood at a glance. By the way, I'm not the first or only palenotologist to use DGS.
Not much makes sense the way textbooks are now teaching reptile evolution. Many studies nested diadectids and microsaurs just outside the clade Amniota, but they share very few characters in common. Moreover, diadectids are mismatches for all of the reptiles considered basal. Elsewhere within other family trees there are other force-fits and "by default" mismatches, all due to employing too small of an inclusion list. As a result the ancestries of various clades (basal reptiles, caseasaurs, snakes, turtles, pterosaurs, mesosaurs, dinosaurs, ichthyosaurs to name a few) have remained mysteries or poorly supported. All those mysteries and mistakes are clarified and repaired here simply by expanding the taxon list.
Textbooks focus on the various skull openings and ankle shapes in reptiles, dividing them accordingly, but not linking one large clade to another. These openings and ankle shapes are indeed diagnostic, but convergence and reversal are almost never identified. Here they are.
This website presents a new solution to many of these phylogenetic problems by presenting the results of a cladistic analysis that included samples from all the major clades, with special focus on the troublesome taxa. No one has ever done that before. If you follow this method (expanding your taxon list) you will find identical results no matter which characters you employ, so long as a sufficient number (~200) are used.
Here two major clades of reptiles were recovered. One, the new Lepidosauromorpha, includes turtles, lizards and their ancestors. The other, the new Archosauromorpha, includes mammals, birds, crocodilians and their ancestors. In the present tree, basal synapsids gave rise to diapsids (excluding lepidosaurs). Here one can trace the origin of dinosaurs (or any other clade) back to the origin of reptiles. All the sister taxon transitions are gradual with no morphological mismatches or enigmas in the lot.
In support of this nesting, Rieppel and deBraga (1996) reported during embryonic development the jugal shows a semilunate shape without a posterior process in both lepidosaurs and turtles, whereas a triradiate jugal with a posterior process is found in mammals and crocodiles. In addition, turtles and lepidosaurs lack a true radiale in the carpus (wrist), its homological equivalent buds off from the intermedium during embryonic development, but in mammals and crocodiles the radiale buds off the radius. The patterns of ossification of the fifth metatarsal and tarsus also separates turtles and lepidosaurs from mammals and crocs.
Rieppel O and deBraga M 1996. Turtles as diapsid reptiles. Nature 384:453-454.
You might wonder why I don't publish on some of the new hypotheses and observations proposed here. Well, it's not like I haven't tried. Unfortunately many of my hypotheses often "go against the grain," revealing weaknesses in prior studies. Many of the hypotheses I have tested and rejected were authored by professors chosen to referee my submissions. Sure that's a conflict of interest, but that's reality. I realize now that these hypotheses will never be published in peer-reviewed journals. They step on too many toes. On the other hand, I also realize that once posted on the web, this data will never be able to be published in traditional form. Nevertheless, past misinterpretations (some of which are mine) have to be revealed and the mistakes have to be rectified. It's a big job looking at 210 taxa and 228 characters. That's over 47,000 character scores, not counting the missing data. Not many workers are going to want to devote themselves to such a chore. So here it is. The tree can be replicated and every portion thereof is just as robust. So, smaller studies can be based on these results. This list can provide a basis for taxon inclusion decisions in future smaller studies. Otherwise, we're stuck with the nesting of flying pterosaurs as sister to the croc-like phytosaurs, as a recent paper by Nesbitt (2011) proposed, based on earlier works listed below. Problem nestings, such as this, are why this website was built.
Also included on this website are several specimens from private collections that would otherwise never be published. There is a general ban on such publication because private specimens are not readily available for scientific study. In truth, neither are several "public" specimens which often get stuck in professorial drawers for months or years or end up on display behind glass. In any case, no such restrictions hamper the reporting of private specimens here. So, finally we'll get a report on a privately owned baby Pteranodon and something about a few other private specimens as well.
Click here to read several of my published papers and abstracts.
Click here to make comments or suggestions.