What is Brouffia, a short series – part 3

Earlier and a day before that we looked at the problems posed by Brouffia, which two earlier workers, Brough and Brough (1967) and Carroll and Baird (1972) interpreted significantly different from each other. Both sets of workers had direct access to the fossil and presumably looked at it with binocular microscopes.  The two authors did not agree on the placement of the pineal opening, the presence or absence of intertemporal bones and several other distinctions, including the number of sacrals present. Ironically, the Brough and Brough team found an intertemporal and thus determined the specimen was pre-reptilian, but then decided there were two sacrals present, which is a reptilian trait. The Carroll and Baird team found no intertemporal, but only one sacral, a pre-reptilian trait.

Today we’ll do our best to make sense of this mess without seeing the actual fossil, or even a photo of the fossil (yes, I’m peering over the abyss). Instead we’ll pull clues from the only available data, drawings (Fig. 1) by the above two studies.

The first thing I note is that neither prior study found large palatal fangs. So that puts us over the pre-reptile/reptile divide on the reptile side. The prefrontal and postfrontal just barely did not touch. That is also a reptilian trait. The Carroll and Baird (1972) study found only one sacral, but the evidence indicated the earlier Brough and Brough (1967) study was correct in finding two sacrals. The posterior rim of the squamosal was straight, lacking an otic notch, which is another reptilian trait.

Brouffia skull reconstructed

Figure 1. The skull of Brouffia based on both Brough and Brough (1967 anterior) and Carroll and Baird (1972 posterior and overprinted here). The dorsal lacrimal and posterior jugal fade away in the reconstruction because those areas are unknown in situ. I do NOT imagine a lateral or rostral fenestra here. This is the data I used to populate the matrix.

A new reconstruction of the skull (Fig. 1) is based on the anterior data provided by Brough and Brough (1967) because the the Carroll and Baird (1972) study failed to provide data here. The posterior data is based on Carroll and Baird (1972) because it is more reptilian and we’re leaning that way due to the lack of palatal fangs, last seen in Gephyrostegus. Brough and Brough (1967) also interpreted some strange processes on the dorsal jugal that probably represent the ventral postorbital/postfrontal suture.

With the reconstruction of the skull in hand the data nested Brouffia at the most basal position in the new Archosaurmorpha branch of the large reptile tree (it’s not listed there yet, but will be before year’s end). It shares a few traits with gephyrostegids and new lepidosauromorphs that no other archosauromorph shared. I suspect that more of the palatine is hiding beneath the mandibles. The premaxilla/maxilla connection is more fragile than in any other basal reptile. Overall the skull resembles gephyrostegids and coelostegids and paleothyrids. The premaxilla dipped as in captorhinids.

I will be relaying out the appropriate pages on reptileevolution.com to make room for this key taxon at the very base of the Reptilia. This moved Cephalerpeton over to the new lepidosauromorpha, so we no longer have a single most basal reptile following Gephyrostegus. 

Still looking for photos of the specimen, if available. We’ll have one more post on this series detailing some of the traits this new taxon nesting sheds light on.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Brough MC and Brough J 1967. The Genus Gephyrostegus. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 252 (776): 147–165. doi:10.1098/rstb.1967.0006
Carroll RL and Baird D 1972. Carboniferous Stem-Reptiles of the Family Romeriidae. Bulletin of the Museum of Comparative Zoology 143(5):321-363. biodiversitylibrary

What is Brouffia? – A short series – part 2

Yesterday we looked at two very different interpretations of the skull of Brouffia orientalis, neither of them mine. Today, here’s the post-crania in situ, part and counterpart (Fig. 1, click to enlarge it) presented by Brough and Brough (1967, one view flipped for comparisons).

Sorry we’re taking it so slow. Lots going on over here, including Christmas shopping. I’m also hoping someone out there will send a good photo of the specimen to put under DGS.

brouffia-overall-insitu800

Figure 1. Click to enlarge. Quite close to the earliest known reptile, phylogenetically, the only fossils of Brouffia are known from the Late Carboniferous. Was it a reptile? Or a close runner-up? The twin tops on the ilium are otherwise only known in pre-reptiles. If an intertemporal was present, as Brough and Brough (1967) interpret the skull, that would confirm its pre-reptile status. However if the inter temporal was gone, having fused to the parietal, as Carroll and Baird (1972) see it (above), then the phylogenetic picture is muddied.

Brough and Brough (1967) published large tracings of tiny Brouffia (which they considered a specimen of Gephyrostegus). The lack of complete ossification in the pelvis and pectoral girdle argues for an immature status in this specimen. The presence of complete ossification in the carpus argues for a mature status. Was this a small adult? Or a well-ossified (but only in certain places) juvenile? Related forms, including Cephalerpeton and Casineria did not have a coosified pectoral girdle, but others did.

No intercentra have been observed, but they may have been poorly ossified. The spaces between the centra are beveled to receive them.

Brough and Brough (1967) restore the manus with short digits. I found the hand to be longer and more asymmetric (Fig. 1), matching those of related taxa and those several nodes away.

Brough and Brough (1967) reported two sacrals, making it more reptilian. Carroll and Baird (1972) reported only one. The pelvis is unknown in Cephalerpeton, but it is more reptilian looking in the non-reptile Gephyrostegus than in Brouffia. Odd that the coracoids appear to be missing.

More later.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Brough MC and Brough J 1967. The Genus Gephyrostegus. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 252 (776): 147–165. doi:10.1098/rstb.1967.0006
Carroll RL and Baird D 1972. Carboniferous Stem-Reptiles of the Family Romeriidae. Bulletin of the Museum of Comparative Zoology 143(5):321-363. biodiversitylibrary

What is Brouffia? A short series – part 1

Today we’re going to start a short series of Brouffia, which may be either a basal reptile or a non-reptile closer to Gephyrostegus, only much smaller, depending on which professional tracing is more correct (Fig. 1).

Brouffia

Figure 1. What is Brouffia? Here we see two professional tracings made by teams of paleontologists both of whom had this specimen under the microscope. Brough and Brough (1967) interpreted the specimen with pre-reptile traits. The Carroll and Baird (1972) had the benefit of seeing the prior interpretation and saw things differently. Yes the scale bars don’t match. I’ll try to get to the bottom of that problem, too. 

Earlier I was under the impression that the Brough and Brough (1967) part and counterpart specimen belonged to Gephyrostegus, as they considered it. Then I discovered that this specimen is one and the same with Brouffia, which Carroll and Baird (1972) considered to be an early reptile. In any case, I made a mistake that will be rectified shortly.

Despite the Late Carboniferous age of Brouffia, the fine line between reptile and non-reptile is currently best represented right here as discussed earlier.

The current large reptile tree lists this specimen as two taxa, separated earlier. But with new data (not shown publicly yet) Brouffia moved to the base of the new Archosauromorpha, prompting the head slap and opening up this new study.

The way this turns out will require minor changes to the current large reptile tree at its base. At this point, late Sunday night, I don’t know how this is all going to turn out. Come along for the ride.

At this point I have only these drawings to use as data. It just goes to show that a first-hand inspection with a microscope is not always the panacea and trump card that others have claimed. If anyone has a photo of the specimen, that might help explain the differences.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Brough MC and Brough J 1967. The Genus Gephyrostegus. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 252 (776): 147–165. doi:10.1098/rstb.1967.0006
Carroll RL and Baird D 1972. Carboniferous Stem-Reptiles of the Family Romeriidae. Bulletin of the Museum of Comparative Zoology 143(5):321-363. biodiversitylibrary

There’s another basalmost reptile out there…

Currently Cephalerpeton is the basalmost reptile we know of, the most primitive one most likely to have laid that first amniotic egg. It nests at the base of all other reptiles and descended from a tiny Gephyrostegus watsoni (Figs. 2 and 3).

The problem is Cephalerpeton was twice the size of G. watsoni. Cephalerpeton had those giant teeth, both in the premaxilla and maxilla. These traits had morphologically skewed Cephalerpeton toward the plant-eating side of the basal Reptilia beginning with the captorhinids and millerettids.

Cephalerpeton, the most primitive known reptile

Figure 1. Cephalerpeton, the most primitive known reptile. Even so, it is clearly derived from its proximal sister, Gephyrostegus watsoni. If you’re looking for THE most primitive reptile, look for something in between G. watsoni and Cephalerpeton in size and morphology.

Plus, Cephalerpeton has a few autapomorphies, like a long robust neck and the deeply concave mandible. Then again, Cephalerpeton arrives rather late on the scene in the fossil record.

Cephalerpeton size comparisons

Figure 2. Cephalerpeton and Gephyrostegus watsoni size comparisons

The tiny Gephyrostegus watsoni (Fig. 3) is probably closer to the size expected following Carroll’s (1970) hypothesis on egg-laying. All it needs is to fuse the intermedium to the supratemporal or postorbital. Or, the intermedium may have become reduced to nothing, as it never reappears in derived taxa.

Gephyrostegus watsoni

Figure 2. Gephyrostegus watsoni, a tiny pre-reptile and THE sister to the Reptilia. In most respects it is a close match to Cephalerpeton and the larger, more primitive G. bohemicus.

Okay, so to find the basalmost reptile…
We’re looking for a twin to G. watsoni with the following changes: 1) loss of the intermedium; 2) pelvis without two dorsal processes; 3) a smaller, narrower interclavicle; 4) perhaps a taller, more ossified scapula; 5) better ossified vertebrae.

If something like this is languishing unloved in some museum drawer, well, let’s bring it out!

Speaking of something old, something new on Romeriscus coming soon.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Brough MC and Brough J 1967. The Genus Gephyrostegus. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 252 (776): 147–165. doi:10.1098/rstb.1967.0006
Carroll RL 1970. The Ancestry of Reptiles. Philosophical Transactions of the Royal Society London B 257:267–308. online pdf
Carroll RL and Baird D 1972. Carboniferous Stem-Reptiles of the Family Romeriidae. Bulletin of the Museum of Comparative Zoology 143(5):321-363. online pdf
Gauthier JA 1986.  Saurischian monophyly and the origin of birds, p. 1-55. In K. Padian (ed.) The Origin of Birds and the Evolution of Flight. Memoirs of the California Academy of Science 8, Berkeley, California.
Gregory JT 1948. The structure of Cephalerpeton and affinities of the Microsauria. American Journal of Science, 246:550-568 doi:10.2475/ajs.246.9.550
Jaeckel O 1902. Über Gephyrostegus bohemicus n.g. n.sp. Zeitschrift der Deutschen Geologischen Gesellschaft 54:127–132.
Moodie RL 1912. The Pennsylvanic Amphibia of the Mazon Creek, Illinois, Shales. Kansas University Science Bulletin 6(2):232-259.

Patterns of Herbivory within the Reptilia

I recently mapped the herbivorous reptiles on the large reptile tree. Click here to see it. Some interesting patterns emerged.

The separation between plant-eaters and insect-eaters formed the basal split in the large reptile tree. The emergence of Limnoscelis and its kin and Lanthanosuchus and its kin from this clade bears further scrutiny. I’m sure there’s a story brewing there. Turtles also emerged from this clade of herbivores. Among charted lepidosauromorphs we don’t see any other herbivores until Iguana and even it supplments with insects when young. Let me know if I’m missing any others.

On the archosauromorph side, Edaphosaurus is the first herbivore with several therapsid clades not far behind. Thereafter we don’t see any until the Placodontia (if they were indeed herbivores and not shell crushers), the Aetosaurs and the Phytodinosauria.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Diedrich CG 2011. Fossil middle triassic “sea cows” – placodont reptiles as macroalgae feeders along the north-western tethys coastline with pangaea and in the germanic basin. Natural Science 3 (1) 9-27 (2011)


How Can Two Trees Look So Different?

A recent paper by Tsuji, Müller and Reisz (2012) reexamined the nycteroleterid, Emeroleter, a long-legged sister to Nyctiphruretus and Macroleter. Their traditional tree (Figure 1) nested Diadectidae and Limnoscelidae outside the Amniota, among many other odd nestings that, unfortunately, recover “sisters” that too often don’t resemble one another. Such odd nestings may be due to misinterpretations, to too many missing taxa between the oddballs or to too few characters employed (136 vs. 228). A contributing factor has to be the lack of an understanding of the diphyletic nature of the complete reptile family tree. The lack of strong support between the clades in the Tsuji, Müller and Reisz tree(Fig. 1) is telling. There are far too few taxa here for the gamut of included taxa.

Sister Problems
In the Tsuji, Müller and Reisz (2012) tree Diadectes nests in its traditional position, outside the Amniota, a whopping 16 nodes away from its sister Procolophon in the large tree. In the Tsuji, Müller and Reisz (2012) tree mesosaurids nest as sisters to Captorhinidae and Millerettidae + Eunotosaurus, none of which resemble mesosaurids.

I’d like to see the Tsuji, Müller and Reisz reconstruction of the the Eudibamus skull, which nests in their tree as a sister to Belebey (known only from a skull). No skull reconstruction or closeup of Eudibamus has ever been published other than here. The slender and long-toed post-crania of Eudibamus is much closer to that of other basal diapsids, like Petrolacosaurus, rather than to short-toed and thick-ribbed millerettids and Eunotosaurus, the only sisters of Belebey with known post-crania.

Lanthanosuchus should have nested with Macroleter. To their credit, Diadectes is indeed a “close enough”sister to Limnoscelis. Younginiformes are indeed sisters to Araeoscelida. Millerettidae are indeed sisters to Eunotosaurus. The pareiasaurs are related to one another as are the nycteroleterids.

Tsuji, Muller and Reisz (2012) tree of basal reptiles.

Figure 1. Tsuji, Muller and Reisz (2012) tree of basal reptiles. Only those branches with support over 66 are highlighted with yellow circles. Note how few branches are highlighted.

Results of the Large Heretical Tree, Pruned to Match
By greatly expanding the taxon list more confidence can be placed in the nesting of individual taxa because there are so many more opportunities available for them to nest. Figure 2 presents a greatly reduced version of the large tree, pruned to more closely match the taxon list of Tsuji, Müller and Reisz (2012). I would have thought the two trees would be closer to each other in topology, but they are not. I’m not surprised by the lack of resolution here (Fig. 2) at the bases of the three recovered main clades (in color). There are many other taxa excluded between the clades, as recovered in the large tree. This is what happens to small studies with too large a gamut and too few taxa.

The large tree pruned to match the taxon list of Tsuji, Muller and Reisz (2012).

Figure 2. The large tree pruned to match the taxon list of Tsuji, Muller and Reisz (2012). While the pruned tree reflects the results recovered from the large tree, it does not match the Tsuji, Muller and Reisz tree. One must be very wrong. Here it matters little how much support is present to support the branches because so many taxa have been excluded here from the large tree with complete resolution.

How Do Scientists Test One Tree Against Another?
How can one judge the validity of one tree versus another? The Tsuji, Müller and Reisz (2012) tree was created by professional paleontologists. These PhDs had direct access to the specimens. I did not have any of these advantages. However…

In counterpoint, everyone knows that adding taxa and character traits to a cladistic analysis is like adding greater diameter to a telescope lens or mirror. More taxa and characters = greater resolution. The large study is a magnitude larger than the Tsuji, Müller and Reisz (2012) tree. Larger size provides greater confidence in tree topology because more possibilities are covered rather than excluded.

As blogged several times earlier, sister taxa should look like one another. Take mesosaurs. Sister taxa should have long jaws, a retracted naris, an elongated torso and tail, short paddle-like limbs and a long pedal digit 5. We find such traits in Wumengosaurus, Askeptosaurus, Utatsusaurus and other enaliosaurs. We don’t find those traits in sisters recovered by Tsuji, Müller and Reisz (2012), captorhinids and millerettids.

I’m stymied to see so many tree topology differences in the two similar taxon list trees. I wish the character list of Tsuji, Müller and Reisz (2012) followed the traditional order of: skull, mandible, axial and appendicular characters, but they are all mixed up. Given this disorganization, it will be difficult to wade through the data point by point. When I have more to say on this, I will do so.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Tsuji, Müller and Reisz 2012. Anatomy of Emeroleter levis and the Phylogeny of the Nycteroleter Parareptiles. Journal of Vertebrate Paleontology 32 (1): 45-67. doi:10.1080/02724634.2012.626004.

The Tiny Gephyrostegus and The Tiny Origin of the Reptilia

This page is no longer valid. Please see the update at:
https://pterosaurheresies.wordpress.com/2014/11/02/news-at-the-base-of-the-amniota-part-3-the-amniotic-egg/

And at: www.reptileevolution.com/gephyrostegus_watsoni.htm

Gephyrostegus-size

Figure 1. Two species of Gephyrostegus, the closest outgroup taxon to the Reptilia, in size comparisons to Cephalerpeton, the most primitive reptile. As you can see, Gephyrostegus watsoni was smaller than both. Whether G. watsoni (Fig. 2) was a juvenile or not (it is not a tadpole but certain tiny bones remain unossified), the fact remains that the earliest of reptiles were all smaller than Gephyrostegus bohemicus and they stayed small for several succeeding phylogenetic nodes. 

Carroll’s Hypothesis
As blogged earlier, Dr. Robert L. Carroll (1970) figured out that the earliest of all reptiles, the ones that biologically invented the amniotic egg, would be small specimens similar to Gephyrostegus. Carroll (2008) wrote: “On the basis of the present fossil record, all adequately known Palaeozoic reptiles appear to have had a common ancestry among the predecessors of the known gephyrostegids.” Carroll (2008) considered the possibility of a long ghost-lineage for gephyrostegids, unfortunately he did not undertake a cladistic analysis like the one here. Later Carroll (2009) dismissed his earlier hypothesis because, […gephyrostegids] lack many definitive features [of reptiles] and the best-known genus only occurs long after the appearance of unquestioned amniotes.” 

Gephyrostegus watsoni

Figure 2. Gephyrostegus watsoni. This tiny specimen retained an intermedium in the skull roof, a hallmark of non-reptiles. Small manual phalanages were poorly ossified. The pelvis likely connected to only one sacral vertebra, another non-reptile hallmark.

The Importance of Small Body Size
Carroll (2008) wrote, “Study of the earliest known reptiles and their closest relatives among contemporary amphibians indicates that the initial adaptation leading to the emergence of the class was assumption of a terrestrial habit, with accompanying small body size. The small body size of the immediate ancestors of reptiles would have made it possible for them to produce sufficiently small eggs that they could develop in damp places on land without initially being supported and protected by extraembryonic membranes.”

Carroll (1991) presumed the hatchling of tiny early reptiles would have been very large relative to the adult, skipping the tadpole stage and adapting to life immediately as an adult. He noted living salamanders that lay eggs on land have the largest hatchling to adult ratio. Carroll (1991) estimated the size of such an egg at 1 cm with an adult of 10 cm in snout-vent length. Cephalerpeton was exactly that size. Gephyrostegus watsoni (Fig. 2) was less than half that size.

The Origin of the Reptilia
Here Gephyrostegus is the closest outgroup taxon to the Reptilia and Cephalerpeton is the most primitive reptile (despite being 30 million years younger than the oldest known fossil reptiles, Westlothiana and Casineria). Another species, Gephyrostegus watsoni, was smaller than both. Whether G. watsoni was a juvenile or not (it is not a tadpole but certain tiny bones remain unossified), the fact remains that the earliest of reptiles were all smaller than Gephyrostegus bohemicus and basal reptile stayed small for several succeeding phylogenetic nodes.

Reptiles
Distinguished from basal tetrapods, basal reptiles lose their palatal fangs, the intertemporal (a tiny skull roof bone) and the occipital notch at the back of the skull. The occiput includes a large supraoccipital bone linking the skull roof bones to the back of the braincase. The pterygoid developed a transverse flange. The intercentra were reduced to crescents. The proximal tarsals integrated to form an astragalus and calcaneum, which was present in Gephyrostegus and reversed in Weslothiana.

Rapid Size Increase?
Carroll (2008) wrote: The rapid increase in body size in all lineages of Pennsylvanian reptiles indicates the prior development of an amniotic egg.” Perhaps not with reptiles first appearing some 340 million years ago (e.g. Casineria to Hylonomus) and not getting much bigger for the next 40 million years (e. g. Cephalerpeton to Milleretta).

A chronology of the basal Reptilia.

Figure 3. Click to enlarge. A chronology of the basal Reptilia.

Diadectids
Carroll (2008) was not able to establish the specific relationships of the Diadectidae. Here that clade is buried deep within the new Lepidosauromorpha.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Carroll RL 1970. The Ancestry of Reptiles. Philosophical Transactions of the Royal Society London B 257:267–308. online pdf.
Carroll RL 1991. The Origin of Reptiles in Origins of the Higher Groups of Tetrapods: Controversy and Consensus.  Schultze H-P and Trueb L (eds). Cornell University Press.
Carroll RL 2008. Problems of the Origin of Reptiles. Biological Reviews 44(3):393-431.
Carroll RL 2009. The Rise of the Amphibians 365 Million Years of Evolution. The Johns Hopkins University Press. 360 pp.

wiki/Gephyrostegus
wiki/Cephalerpeton

Book Review: The Rise of the Amphibians

Robert L. Carroll, famous for his encyclopedic Vertebrate Paleontology and Evolution (1988) has produced another encyclopedic volume focusing on the basal tetrapods arising from fish and producing frogs, salamanders, caecelians and, our favorite subject: reptiles (including birds and mammals) in The Rise of the Amphibians – 365 Million Years of Evolution (2009).

Rise of the Amphibians by Robert Carroll

Rise of the Amphibians by Robert Carroll. A must have for all interested in the origin and evolution of all tetrapods.

Carroll takes us from the earliest Cambrian fossils up through the key Devonian fish taxa that ultimately developed limbs, then on through all the Carboniferous and later basal tetrapods (amphibians) that once dominated the shallow waters. Skeletal drawings are richly provided. The text is easy to read.

Amniotes
Carroll’s (1970) hypotheses on early amniote development are landmarks. According to the present large tree, his concept of a tiny tetrapod as the first amniote egg layer has been confirmed with the transition from a small Gephyrostegus species to the only slightly larger Cephalerpeton (both known from late surviving specimens). Earlier Carroll (1970) considered Gephyrostegus close to the ancestry of amniotes, but he dismisses that hypothesis here because, “they lack many definitive features [of reptiles] and the best-known genus only occurs long after the appearance of unquestioned amniotes.” Evidently he didn’t consider the possibility of a long ghost-lineage in this case.

No Cladistic Analysis Here
Carroll (2009) does not employ or present any novel cladistic analysis. Neither does he point out which of the several Carboniferous amniotes he surveys in chapter 7 is the best candidate for the title of “most primitive reptile.” Rather he introduces us to Hylonomus and Paleothyris and provides a list of the “Distinctive Characters of Early Tetrapods” (although I’m sure he meant to title the list the “Distinctive Characters of Early Amniotes.”)

Westlothiana
Carroll reports, “Westlothiana has many features of the skeleton that are closer to those of early amniotes than any other Lower Carboniferous tetrapods, but the more primitive palate and tarsus and the great elongation of the trunk relative to the limbs suggest that it belongs to an earlier and divergent lineage.” In the large tree Westlothiana nested at the base of the new Archosauromorpha as a phylogenetic descendant of a sister to Cephalerpeton, despite its several autapomorphies and reversals. Yes, it was a “backslider.” It happens.

Diadectids
In chapter 7 Carroll (2009) also provides several illustrations of skeletal elements, stages in the development of the amniote egg of a chicken, a sequence illustrating the process of amniote entrapment in hollow tree trunks and several classic diadectid, pelycosaur and Petrolacosaurus skeletons. I’m glad he put diadectids into this chapter. He describes them as “…large animals also thought to be close to early amniotes…” so he doesn’t take a stand on which side of the amniote egg they belong. Here they nest with amniotes.

For anyone embarking on a study of the non-amniote tetrapods, here’s a great start and a thorough reference volume. This book should be on every college library shelf.

References
Carroll RL 1970. The Ancestry of Reptiles. Philosophical Transactions of the Royal Society London B 257:267–308. online pdf
Carroll RL 2009. The Rise of the Amphibians 365 Million Years of Evolution. The Johns Hopkins University Press. 360 pp.

The First Anniversary of ReptileEvolution.com – Dec 21

December 21 marks the first year anniversary of ReptileEvolution.com, the basis and chief reference for the PterosaurHeresies.comReptileEvolution.com was created to get the word out on the various mistakes and oversights in the current literature. These errors were found principally by testing them against the relationships recovered from the large reptile family tree. Some morphological insights were also reported. Proper nestings and great papers were given all due honor.

Frustration, the Mother of all Invention
As mentioned on the “About” page, the impetus for the creation of ReptileEvolution.com came about after getting one last manuscript rejected at the hands of various pterosaur experts who did not want my work to make it into the literature. Yes, my work opposed theirs and suppression was their motive. Sadly, they continue to prefer untenable nestings and bizarre descriptions.

Turned Out to Be a Good Thing!
Had those manuscripts been accepted, the published papers would have languished in quiet isolation on college library shelves, like most papers do. Now the data and results enjoy free worldwide exposure and access. Rather than standard black and white printed imagery, the web permits full color with video overlays and animation. The speed of reporting has been accelerated. Here, updates, additions and corrections take less than a day.

The Tree Keep Growing
A year ago
the reptile tree stood at some 230 taxa, not counting the pterosaur tree, which stood at 165 or so taxa. Today the reptile tree includes 279 taxa, the pterosaur tree includes 180 taxa and the basal therapsid tree includes 39 taxa for rough total of about 500 taxa, give or take some overlap and estimating as I write this 2 weeks prior to uploading. All trees are resolved with high Bremer Test scores. I’m pleased to report that workers are requesting the data matrix for their own studies.

The structure of the tree has not changed so far, despite the influx of 20% more taxa. That’s a good test. Certain taxa have shifted a node or two. That happened as I found mistakes in the matrix that were corrected while uploading new taxa. Correcting mistakes and oversights is the process of science.

The Insights Have Been Very Rewarding
The results speak for themselves. The feedback has been gratifying. The process has been more than interesting. Nothing beats making a discovery!

Thank you for following this blog and checking out the data presented in ReptileEvolution.com. I value your input and will continue to modify any statements and images that are not right on the mark.

Here’s to a great future in prehistory!

Best regards,
David Peters

A Chronology of Basal Reptilia

The dual origin of the Reptilia (following Cephalerpeton) was blogged earlier. Here we’ll take a look at the chronology of basal reptiles during the Carboniferous and Permian.

A chronology of the basal Reptilia.

Figure 1. Click to enlarge. A chronology of the basal Reptilia.

The Most Primitive Known Reptile Was Not the Oldest
Cephalerpeton nested as the most basal reptile, the one closest to the nearest outgroup taxon, Gephyrostegus. Unfortunately the fossil record of both succeed the earliest known reptiles, Westlothiana and Casineria, by some 40 million years. That means the first appearance of Cephalerpeton had to precede its first (and only) appearance in the fossil record by a similar time span. Thus Cephalerpeton was a long-lived taxon. Supporting this hypothesis, the appearance of the proximal sister to Gephyrostegus, Silvanerpeton, first appeared in the fossil record alongside Casineria.

The first appearance of Cephalerpeton during the Kasimovian, some 305 million years ago, also followed the first appearances of several other reptilian taxa, including Hylonomus, Paleothyris and Solenodonsaurus. The first appearance of Cephalerpeton also coincided with the first appearances of Haptodus and Archaeothyris. Such timing demonstrates long ghost lineages in which one can expect to find more Cephalerpeton specimens back to the basal Visean, 345 million years ago.

Protorothyris and Limnoscelis Ghost Lineages
Protorothyris, an outgroup taxon to the Synapsida and Protodiapsida, first appeared in the fossil record about 290 million years ago. That succeeded the first appearances of phylogenetic descendants by some 15 million years. So, Protorothyris was also a long-lived taxon with an earlier origin.

Limnoscelis, a basal diadectomorph, succeeded its phylogenetic successor, Solenodonsaurus.

Turtle Ancestry
The earliest know turtles, Odontochelys and Proganochelys, first appeared in the Late Triassic, 225 million years ago. Their phylogenetic predecessor, Stephanospondylus, appeared 290 million years ago. That gives turtles 65 million years (nearly the entire Permian and Triassic) to develop their unique morphologies from their closest known sister taxon at the base of the Permian.

Therapsid Ancestry
Basal therapsids, like Nikkasaurus and Biarmosuchus, first appeared some 250-255 million years ago. Their closest outgroup sisters, Ophiacodon and Archaeothyris, lived some 50 million years earlier.

Heleosaurus and Milleretta Ghost Lineage
Heleosaurus appears in the fossil record approximately 270 mya, but its phylogenetic successors appeared 305 mya, 35 million years earlier. Thus Heleosaurus was a long-lived taxon.

Milleretta appears in the fossil record approximately 255 mya, but its phylogenetic successors, including Bolosaurus, appeared 300 mya, 45 million years earlier. Thus Milleretta was also a long-lived taxon.

Most of the rest of the taxa are chronologically ordered with regard to their phylogenetic order. Sphenodon, the living Tuatara, is a living example of a long-lived taxon.

Morphological Stasis and Rapid Radiation
The chronological tree (Fig. 1) illustrates the twin topics of morphological stasis and rapid radiation. The Tournaisian (Early Carboniferous) was a time of rapid change in our reptilian predecessors. Most of the rest of the Early Carboniferous was a time of stasis with a rapid radiation in the Pennsylvanian, producing all of the major reptilian clades. The Permian is where we find most of the basal reptile fossils. Here we find some basal taxa (presumably earliest Permian) surviving to the end of the Permian, a case of stasis. The Triassic, as I need not remind anyone, was a time of rapid radiation following the Permian extinction event.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.