SVP 2018: Pelycosaurian phylogeny (should not include Caseasauria!)

Wilson, et al. 2018
discuss various issues with pelycosaurian phylogeny, but then make the mistake of including Caseasauria, an unrelated clade in the large reptile tree (subsets in Figs. 1, 2).

It’s that simple.
Adding taxa shows that Casesauria nest within the new Lepidosauromorpha derived from Milleretta, while pelycosaurs nest within the new Archosauromorrpha, derived from Varanops. The lateral temporal fenestra is convergent and appears in many caseasaur sisters and cousins (Fig. 2).

Given that, the authors report:
“We recover a monophyletic Caseasauria and Eupelycosauria.” Well, of course, they did. That happens with unrelated taxa.

Figure 1. A monophyletic Pelycosauria if we can accept the changes suggested in the text.

Figure 1. A monophyletic Pelycosauria without the Caseasauria, which nests in the basal Lepidosauromorpha (see figure 2) when more taxa are added.

Adding taxa
going back to the origin of the Amniota (= Reptilia) would clarify issues. That’s what the large reptile tree is for. No one has to use the characters or the scoring, but it is a mistake not to use the relevant taxa revealed by the LRT.

Figure 2. Subset of the LRT: basal lepidosauromorpha, featuring Caseasauria.

Figure 2. Subset of the LRT: basal lepidosauromorpha, featuring Caseasauria. Pelycosaurs nest in the basal archosauromorpha when more taxa are added.

Wilson WM, Angielczyk KD, Peecock B, Lloyd GT 2018. Pelycosaurian “lineages”: a meta-analysis of three decades of phylogenetic research. SVP abstracts.

Metaanalysis is the statistical procedure for combining data from multiple studies. When the treatment effect (or effect size) is consistent from one study to the next, metaanalysis can be used to identify this common effect.

From the first post on this subject back in 2011:

The case for taking Caseasauria out of the Synapsida.

Figure 3. Which of these skulls does NOT belong with the others. The case for taking Caseasauria out of the Synapsida.


SVP abstracts – Ennatosaurus

Romano et al. 2017
brings us a new reconstruction of Ennatosaurus (Fig. 1, btw – this is not it.)
Figure 1. An old reconstruction of Ennatosaurus, still not a synapsid, closer to millerettids and Eunotosaurus.

Figure 1. An old reconstruction of Ennatosaurus, still not a synapsid, closer to millerettids and Eunotosaurus.

As you read the abstract,
bear in mind the only thing wrong here is the author’s insistence that Ennatosaurus is a pelycosaur and a synapsid. It is neither, as the addition of taxa to a cladistic analysis would have informed the Romano team. Ennatosaurus was derived from the similarly built milllerettids. This was demonstrated several years ago in the large reptile tree by the simple addition of taxa to the inclusion set.

From the abstract:
The Russian caseid Ennatosaurus tecton (Synapsida Caseasauria) is an important member of the group, being among the few “pelycosaurs” occurring in the Middle Permian, thus making caseids among the longest-surviving groups of non-therapsid synapsids. Although the cranial skeleton has been recently restudied in detail, the descriptions currently available for the postcranium are essentially limited to the original short account on the holotype provided by the original description from the 1950s. This contribution represents a new analysis of the postcranium of this taxon, using several different approaches. The postcranium of Ennatosaurus is informative with respect to both the taxonomy and phylogeny, with autapomorphic characters present particularly in the vertebral column. In addition, we conducted eight principal component analyses to investigate the position of the various appendicular elements of Ennatosaurus within the caseid morphospace. Members of all major groups of “pelycosaurs” were included in the morphometric analysis (along with selected outgroup taxa), allowing us to make some broader preliminary inferences regarding postcranial morphospace occupation of these basal synapsids for each individually-considered element. From the results of the principal component analyses, a major decoupling among the morphological patterns of stylopodial and zeugopodial elements is detected. Whereas femora and humeri exhibit a shared common pattern (with a wider overlap in their respective morphospace), the ulnae, radii, tibiae and fibulae show well-separated regions of morphospaces in the different clades. This result indicates the importance of such long bones also for taxonomic differentiation (in addition to their use for classical functional and biomechanical studies). Finally, a 3D photogrammetric model of the mounted specimen at the Paleontological Institute of Moscow has been used to obtain the first in vivo reconstruction of Ennatosaurus tecton, providing for the first time a potentially realistic picture of the Russian caseid in life.

For all this great work
resistance to taxon inclusion doomed any conclusions drawn. Sadly this basic problem is similar to workers who resist adding fenestrasaurs to pterosaurs studies, thalattosaurs to Vancleavea studies, tenrecs and desmostylians to whale studies, etc. etc…

Romano M, Brocklehurst N and Fröbisch J 2017. Redescription of the postcranial skeleton of Ennatosaurus tecton (Synapsida, Caseasauria, Caseidae) and its first in vivo restoration. Abstrcts from the 2917 meeting of the Society of Vertebrate Paleontology in Calgary.

Can Vaughnictis attract caseasaurs back to the synapsids again?

Welcome to another taxon challenge from Dr. David Marjanović
Yesterday we looked at Diplovertebron, a taxon Dr. Marjanović suggested (as others have) was just another Gephyrostegus.

Today we’ll reexamine the traditional nesting of caseasaurs with synapsids with a focus on Vaughnictis (Fig. 1), which looks kind of like a caseasaur. Earlier we made the case that the Caseasauria nested better with Millerettidae than with Synapsida when more taxa are included. Since then Vaughnictis was added to the large reptile tree (LRT, 1012 taxa) and it nested as the last known common ancestor to birds and bats (= archosauromorph diapsids and synapsids). 

Despite great resemblance,
the basal prosynapsid Vaughnictis (Fig. 1) does not attract the clade Caseasauria (Fig. 2; Casea, Cotylorynchus and kin including Datheosaurus and Eothyris,Fig. 1) back to the base of the Synapsida (Fig. 3; Varanosaurus, Dimetrodon and kin). Given their phylogenetic distance from one another, the resemblance is indeed extraordinary, especially in the temporal area. Perhaps even more so between Vaughnictis and Milleretta, than with a basal caseasaurid, like Eothyris.

Figure 1. The basal synapsid, Vaughnictis, and the basal caseasaur, Eothyris. For starters, synapsids have a taller than wide skull and caseasaurs have a wider skull. See text for other details.

Figure 1. The basal prosynapsid, Vaughnictis, and the basal caseasaur, Eothyris. For starters, synapsids have a taller than wide skull and caseasaurs have a wider skull. See text for other details.

At present
the LRT nests caseasaurs with Eothyris + Oedaleops + Colobomycter) and slightly further from Feeserpeton + Australothyris + Eocasea and kin. A shift of the Caseasauria (Fig. 2) to the base of the Synapsida (Fig. 3) adds at least 26 steps.  

Figure 2. Milleretta, caseasaurs and kin. The LRT nests these taxa together apart from the Synapsida, with which they share a lateral temporal fenestra.

Figure 2. Milleretta, caseasaurs and kin. The LRT nests these taxa together apart from the Synapsida, with which they share a lateral temporal fenestra. If any taxon resembles Milleretta, Vaughnictis is a better candidate than any caseasaur.

Despite sharing a lateral temporal fenestra
caseasaurs share more traits with millerettids than with synapsids, which retain their predatory teeth and a taller, narrower skull. Vaughnictis retains a short rostrum from ancestors like Protorothyris (Fig. 3). Synapsids never had the rostral overbite found in caesars, nor did they have that arrowhead-shaped set of nasals. Caseids and kin had three premaxillary teeth, not four or more as found in synapsids and Vaughnictis. The surangular in caseids does not extend anterior to the coronoid process. The dentary tip rises in synapsids, but not caseids, among several other distinct traits.

Figure 3. Vaughnictis is basal to the Synapsida and the Prodiapsida, here represented by Mycterosaurus.

Figure 3. Vaughnictis is basal to the Synapsida and the Prodiapsida, here represented by Mycterosaurus.

Can Vaughnictis make Caseasauria a synapsid clade again?
No. Not with the present taxon list. The reason why experts continue to promote caseasaurs as synapsids goes back to a long-standing tradition of taxon exclusion. They exclude members of the Millerettidae. Expand the gamut of your taxon list, and let the taxa nest wherever they want to.

Caseid diaphragms? Bogus, bogus, bogus…

Lambertz et al. 2016 imagine
a diving aquatic niche for caseids like Cotylorhyhnchus (Fig. 1), and in order to breathe upon surfacing, a mammal-like diaphragm must have been present.

One of the authors, Dr. Steven Perry, has been working on the origin of the diaphragm for many years. Perry et al. 2010 wrote: despite over 400 years of research into respiratory biology, the origin of this exclusively mammalian structure remains elusive.” (But see below)

According to Wikipedia: “Mammals have diaphragms, and other vertebrates such as amphibians and reptiles have diaphragm-like structures, but important details of the anatomy vary, such as the position of the lungs in the abdominal cavity.” 

And Tegu lizards are known to possess a proto-diaphragm, which separates the pulmonary cavity from the visceral cavity. While not actually capable of movement, it does allow for greater lung inflation, by taking the weight of the viscera off the lungs.”

And “Crocodilians have a muscular diaphragm that is analogous to the mammalian diaphragm. The difference is that the muscles for the crocodilian diaphragm pull the pubis (part of the pelvis, which is movable in crocodilians) back, which brings the liver down, thus freeing space for the lungs to expand.” 

And this important and pertinent note to pet lizard owners:
“If you turn them over and stroke their bellies, they zonk out… Cute?.. NO, Stop! Lizards do not have diaphragms to help them breath. Their ribs moving in and out actually cause their lungs to inflate and deflate. When a dragon is held upside down or on its back, its stomach pushes on its lungs making it difficult for it to breath and will eventually result in suffocation.” Other similar cautionary notes are compiled here.

Unfortunately, Lambertz et al. also revert to an old invalid tradition,
that caseids are basal synapsids. For over five years it has been known that caseids are not basal to synapsids. The large reptile tree nests caseids as sisters to Feeserpeton and Australothyris and all are derived from a sister to Milleretta within the Lepidosauromorpha, not the Archosauromorpha, in which the Synapsida nests. Thus if you want to know if caseids had a diaphragm, you need to look at living lizards, all of which lack a working diaphragm.

Cotylorhynchus romeri

Figure 1. Cotylorhynchus romeri. Extant lizards lack a diaphragm, so caseids also lacked a daphragm.

Given that backstory Lambertz et al. report:
“The origin of the diaphragm remains a poorly understood yet crucial step in the evolution of terrestrial vertebrates, as this unique structure serves as the main respiratory motor for mammals. Here, we analyze the paleobiology and the respiratory apparatus of one of the oldest lineages of mammal-like reptiles: the Caseidae. [1] Combining quantitative bone histology and functional morphological and physiological modeling approaches, we deduce a scenario in which an auxiliary ventilatory structure was present in these early synapsids. Crucial to this hypothesis are indications that at least the phylogenetically advanced caseids might not have been primarily terrestrial but rather were bound to a predominantly aquatic life. Such a lifestyle would have resulted in severe constraints on their ventilatory system, which consequently would have had to cope with diving-related problems. [2] Our modeling of breathing parameters revealed that these caseids were capable of only limited costal breathing and, if aquatic, must have employed some auxiliary ventilatory mechanism to quickly meet their oxygen demand upon surfacing. [3] Given caseids’ phylogenetic position at the base of Synapsida [4] and under this aquatic scenario, it would be most parsimonious to assume that a homologue of the mammalian diaphragm had already evolved about 50 Ma earlier than previously assumed.” [5]

  1. Not valid for the last five years. Caseids are derived from millerettids and are related to non-synapsids with a convergent lateral temporal fenestra. Hence the confusion.
  2. No one imagines caseids as divers. Maybe shoulder deep in shallow streams.
  3. Diving turtles have no such problems upon surfacing.
  4. Wrong again. See above.
  5. This is a ‘just-so’ story built on taxon exclusion and a couple of big IFs. See below for a hypothesis built on phylogenetic bracketing and skeletal morphology.

So while we’re on the topic of diaphragms,
let’s take a look at another possibility in stem mammals. Since basalmost mammals, like the platypus, Ornithorhynchus, have a diaphragm we’re looking for the origin of this lung muscle in earlier taxa.

A likely place to look 
is at the transition from lateral undulation to limb rotation during locomotion. Only at that stage, where both lungs can inflate simultaneously during locomotion (see Carrier’s constraint), can the diaphragm develop.

Figure 2. Chiniquodon had erect hind limbs and sprawling forelimbs, the first stage in parasagittal locomotion, a requirement for the invention of the diaphragm.

Figure 2. Procynochus, Thrinaxoon, Chiniquodon transition to erect hind limbs while keeping sprawling forelimbs. This was the first stage in parasagittal locomotion, a requirement for the invention of the diaphragm and the most likely stage for its origin.

That transition began with the hind limbs on
derived cynodonts (Fig. 2) which slowly evolved parasagittally rotating hind limbs while retaining sprawling fore limbs. Monotreme mammals continue to retain sprawling forelimbs. Parasagittal forelimbs first appear with Juramaia and the later Therians.

Coincidentally (#1)
The lumbar ribs began to shrink in derived cynodons (Fig. 2) disappearing completely in basalmost mammals.

Coincidentally (#2)
The dorsal rib cage becomes pear-shaped in dorsal view (Fig. 3), with narrower ribs anteriorly and wider ribs posteriorly, near the developing diaphragm.

Coincidentaly (#3)
The dorsal vertebrae become differentiated into dorsal and lumbar vertebrae with neural spines angled posteriorly and anteriorly respectively and shorter and longer vertebral lengths respectively.

Coincidentally (#4)
Sternal ribs, sternebrae, a manubrium and xiphoid process all appear in basalmost mammals, likely signaling the completion of the evolution of the diaphragm.

Coincidentally (#5)
the vertebral column in vivo develop an arch in lateral view (Fig. 3) with a rise to the base of the rib cage followed by a lumbar decent to the sacrals.

Coincidentally (#6)
The external nares become anteriorly oriented, confluent and the premaxillary ascending process disappears, facilitating greater volumes and velocities with every breath.

Figure 1. Megazostrodon, an early mammal, along with Hadrocodium, a Jurassic tiny mammal.

Figure 3 Megazostrodon, an a Jurassic mammal, along with Hadrocodium, a Jurassic tiny mammal.

In summary
in the transition from Cynodontia to Mammalia many changes occurred in the rib cage. Such changes are the most likely skeletal markers for the origin of the soft tissue diaphragm. Such changes are not seen in caseids, which, in any case, are related to lizards not mammals.

I have not read the Lambertz paper,
only the abstract, but with caseids unrelated to mammals, they are sadly barking up the wrong tree. Based on a false premise, that paper was a complete waste of time to produce. Build your papers on a solid phylogenetic foundation and everything will into place naturally.

Lambertz M, Shelton CD, Spindler F & Perry SF 2016. A caseian point for the evolution of a diaphragm homologue among the earliest synapsids. Annals of the New York Academy of Sciences (advance online publication) DOI: 10.1111/nyas.13264.
Merrell AJ and Kardon G 2013. Development of the diaphragm – a skeletal muscle essential for mammalian respiration. FEBS Journal 280(17): 4026-4035.
Perry SF, Similowski T, Klein W and Codd JR 2010. The evolutionary origin of the mammalian diaphragm. Repiratory Physiology & Nuerobiology 171(1):1-16.
Zimmer C. 2015. Behind Each Breath, an Underappreciated Muscle. The New York Times 04/07/2015.

Just ran the numbers: Eocasea is not a sister to Casea

Reisz and Fröbisch 2014
considered Eocasea martini (Late Pennsylvanian, Fig. 1) the basalmost caseid, despite its long slender appearance and small size.

Figure 1. Eocasea in situ with anterior skull imagined.

Figure 1. Eocasea in situ with anterior skull imagined based on phylogenetic bracketing. This long, low taxa does not nest with large, big-bellied caseasaurs but with more similar sister, including Delorhynchus. These are not wide dorsal ribs, but belong to a specimen with a standard, narrow torso.

And at the time (2 years ago), I wrote in,
“[Eocasea] had a long narrow torso and short legs. Note the resemblance to millerettids like Australothyris and Oedaleops.” 

Reisz and Fröbisch did not include those two
in their phylogenetic analysis because they were so sure they had a caseasaur. They also did not include Eunotosaurus, Acleistorhinus, Microleter, Delorhynchus, or Feeserpeton for the same reason.

But they should have done so, because
that’s where Eocasea nests in the large reptile tree (Fig. 2) close to, but not with caseasaurs.

Figure 2. Eocasea nests between Feeserpeton + Australothyris and Delorhynchus in this subset of the large reptile tree, not close to Casea.

Figure 2. Eocasea nests between Feeserpeton + Australothyris and Delorhynchus in this subset of the large reptile tree, not close to Casea.

The problems with the Reisz and Fröbish data set
is that it was too small. The authors presumed Eocasea would be a caseasaur and so included only the following taxa: Reptilia, Diadectes, Limnoscelis, Mycterosaurus, Varanops, Oromycter, Casea, Cotylorhynchus, Angelosaurus, Ennatosaurus and Eocasea. As you can imagine, providing scores to a clade named, “Reptilia” is inappropriate and, frankly, dangerous, whether cherry-picking traits or scoring all zeroes. Diadectes, Limnoscelis, Mycterosaurus, Varanops are not related to each other or to caseasaurs. Reisz and Fröbisch were making guesses without having a large gamut study from which to draw subsets.

Reisz and Fröbisch report,
“Eocasea changes significantly our understanding of the evolutionary history of both caseids and caseasaurs.” Not with the current nesting. The discovery of Eocasea extends the fossil record of Caseasauria and Caseidae significantly, well into the Pennsylvanian, in line with the fossil record of other early synapsid clades, indicating that the initial stages of synapsid diversification were well under way by this time.” Eocasea is not a caseid and caseids are not synapsids, so it doesn’t extend anything related to Caseidae.

“More significantly, Eocasea also allows us to re-evaluate the origin and evolution of herbivory within this clade, and terrestrial vertebrates in general.” It’s not an herby and it’s not a clade member. “Thus, we can identify Paleozoic herbivores because their rib cages are typically significantly wider and more capacious than those of their closest insectivorous or carnivorous relatives. Not in Eocasea. “Nevertheless, it is likely that the ability to process this kind of plant matter precedes the skeletal correlates that can be found in the fossil record.” This is an unsupported supposition in light of the new nesting. “It is therefore possible that we are underestimating the extent of herbivory that existed in the Paleozoic, but this does not invalidate our results because the clades of herbivores that we examine here are widely separated by successive clades of non herbivorous vertebrates.” There is no ‘therefore’ when the setup if invalid. 

To their credit, 
Reisz and Fröbisch did not nest Edaphosaurus or Protorothyris as outgroup taxa to the Caseasauria (Eothyris at its base). Perhaps that is so because they did not include these taxa! And I wonder why? But they did nest the unrelated Varanops and Mycterosaurus as caseasaur outgroups. Both nest about twenty nodes away on the other major branch of the Reptilia, the new Archosauromorpha.The Reisz and Fröbisch tree is bogus because their outgroup taxon list was based not on testing, but on tradition.

If you’re looking for
osteological evidence for herbivory in the ancestry of the Caseasauria, you won’t find big bellies and flat teeth, but you will find several herbivores arising from Milleretta (late Permian late survivor of a Carboniferous radiation) in the clade Lepidosauromorpha. These include diadectids and their allies bolosaurids (post-crania unknown) and procolophonids, pareiasaurs and their allies turtles, along with caseasaurs.

Working on their ‘wish list’
Reisz and Fröbisch continue with their hypothesis: “Whereas other caseids also show dental specializations, with leaf-like large serrations being present in the marginal dentition, Eocasea, Oromycter, and the undescribed Bromacker Quarry caseid lack these serrations. Interestingly, both Oromycter, and the Bromacker caseid show skeletal evidence for herbivory, raising the possibility that oral processing in the form of puncturing vegetation may have evolved within Caseidae after the acquisition of herbivory.”  Only the latter two are indeed caseasaurids. Eocasea definitely is not one. You can’t derive homolog conclusions from unrelated taxa.

Reisz and Fröbisch continue
“Late Pennsylvanian and Early Permian diadectids also show convincing evidence of dental and skeletal adaptations for herbivory. These enigmatic
[not any more] Paleozoic forms are part of Diadectomorpha, a sister group to crown Amniota  [not any more]. A preliminary phylogeny of diadectids indicates that Ambedus, a small diadectid from the Early Permian, tentatively identified as omnivorous because of its labiolingually expanded cheek teeth (but no evidence of dental wear) is the sister taxon to all other diadectids. Ambedus may not be a diadectid as noted here. However, the oldest known diadectid from the late Pennsylvanian of Oklahoma is already clearly an herbivore and older than the edaphosaur Edaphosaurus novomexicanus. As is the case with the caseid and edaphosaur synapsids, the sister taxon of Diadectidae, the Early Permian Tseajaia from New Mexico, was faunivorous.” That oldest known diadectid is not identified.

Reisz and Fröbisch add to their unsupported hypothesis with,
“Although the holotype of Eocasea certainly represents a juvenile individual [actually, and you can check this, it is the same size as sister taxa, but smaller than basal and other caseasaurs], it is diminutive, with an estimated snout-vent length of 125 mm. In contrast, the smallest known herbivorous caseid with a comparable ontogenetic age, based on level of ossification of the vertebrae and pedal elements, is a basal, undescribed form from Germany and has an estimated snout-vent length of 400 mm.” Not sure which specimen this is…

If Reisz and Fröbisch had just
increased the size of their taxon list, they would/could have correctly nested Eocasea, and avoided making the many subsequent mistakes based on that bad nesting, including the unfortunate and inappropriate naming of the taxon and the bogus headline that got tacked to the article and all the PR that attended it.

We don’t have a name yet
for the enanticaseasaurs or paracaseasaurs (Fig. 2), but we need one!

Reisz R and Fröbisch J 2014. The oldest caseid synapsid from the Late Pennsylvanian of Kansas, and the evolution of herbivory in terrestrial vertebrates. PLoS ONE 9(4): e94518. doi:10.1371/journal.pone.0094518


Another, more complete Colobomycter adds data to this enigma

Revised June 10, 2016 with a new reconstruction and nesting with Eothyris. 

A new paper
by MacDougall et al. 2016 introduces Colobomycter vaughni (BRMP 2008.3.1, Fig. 1) a new toothy specimen that adds much needed data to the former enigma taxon, Colobomycter pholeter. They report on the synapomorphies, “enlarged premaxillary tooth and paired enlarged maxillary teeth, unique dentition that grants it an appearance quite distinct from other parareptiles at Richards Spur. This new material differs from that of C. pholeter in that it possesses at least three more teeth on its maxilla, the enlarged premaxillary and maxillary teeth are more gracile than those in C. pholeter, and the lacrimal is restricted externally to the orbital margin and does not exhibit an extra lateral exposure.” 

Figure 1. The new Colobomycter compared to the original pasted on a ghost of the new material. We're learning more about this genus!

Figure 1. The new Colobomycter compared to the original pasted on a ghost of the new material. We’re learning more about this genus!

MacDougall et al. considered Colobomycter a member of the Lanthanosuchoidea. According to MacDougall et al. taxa in that clade include Feeserpeton, Lanthanosuchus, Acleistorhinus and Delorhynchus.

In the large reptile tree 
(Fig. 2) Lanthanosuchus
 nests with Bashkyroleter, Macroleter and Emeroleter.

On the other hand (and this is revised from the original posting)
Colobomycter pholeter
(Vaughn 1958, Modesto and Reisz 2008, UWBM 95405), Lower Permian ~278 mya, was originally considered a caseid pelycosaur, like Eothyris. (But note that Eothyris is not considered a pelycosaur in the large reptile tree (subset Fig. 2). Later, Modesto and Reisz (2008) considered Colobomycter a “parareptile” close to Acleistorhinus. After further consideration, it turns out that Colobomycter is indeed quite similar to Eothyris, as Vaughn 1958 indicated with much less data and fewer optional candidate taxa to consider. Hats off to Vaughn!

Figure 2. Revised cladogram of Colobomycter nesting this genus with Eothyris in an unnamed clade that includes caseasauria.

Figure 2. Revised cladogram of Colobomycter nesting this genus with Eothyris in an unnamed clade that includes caseasauria.

Sharp-eyed observers will note
that earlier I nested the rostrum of Colobomycter with procolophonids based on a smaller portion of rostrum. Clearly. I’m not as sharp as Vaughn was.

At this point
Colobomycter likely had a lateral temporal fenestra.

Herbivore or carnivore?
There are herbivores, carnivores and omnivores related to Colobomycter. It looks like the anterior dentary teeth could scrape off or collect whatever the premaxillary tusks had stabbed into. Eothyris had similar large maxillary teeth.

Figure 3. Eothyris skull in three views. This taxon is the closest known relative to Colobomycter.

Figure 3. Eothyris skull in three views. This taxon is the closest known relative to Colobomycter.

This is only one of tens of thousands of errors I have made
I’m only embarrassed by the ones that have yet to surface. Science and scientists don’t always have all the answers, but if the formula (or in this case cladogram) recovers a sticking point, as it did earlier, it will reward you to go back in and figure out where the errors were made. In this case several little errors among several taxa added up, but are corrected here, resulting once again in a completely resolved tree, hopefully more closely echoing Nature.

MacDougall MJ, Modesto SP and Reisz RR 2016. A new reptile from the Richards Spur Locality, Oklahoma, USA, and patterns of Early Permian parareptile diversification, Journal of Vertebrate Paleontology (advance online publication).

Datheosaurus and Callibrachion: two former haptodine synapsids get reassigned

A recent paper
by Spindler, Falconnet and Fröbisch 2016 correctly reassigned two former haptodine synapsids to the base of the Caseasauria.

Datheosaurus and Callibrachion, two basal caseasaurs, not synapsids, as all prior authors assert, but derived from millerettids, as the large reptile tree demonstrates. Image from Spindler, Falconnet and Fröbisch 2016

Datheosaurus and Callibrachion, two basal caseasaurs, not synapsids, as all prior authors assert, but derived from millerettids, as the large reptile tree demonstrates. Image from Spindler, Falconnet and Fröbisch 2016

Datheosaurus macrourus (Schroeder 1904, Spindler, Falconnet and Fröbisch 2016, Artinskian, Early Permian, 285 mya) was a basal caseasaur, basal to Ennatosaurus and Casea and a sister to Eothyris, all derived from a sister to Eocasea and before that, Milleretta RC70. It was originally and later (Romer and Price 1940) considered a sister to Haptodus. At present the part and counterpart fossils have not been fully worked out.

Callibrachion gaudryi (Boule and Glangeaud, 1893b; Spindler, Falconnet and Fröbisch 2016) was similar and larger, but is less completely known.

Both of these taxa
were originally described over a hundred years ago and have not been studied much since then. Romer and Price (1940) evidently paid little attention to them and followed the earlier assignment to the haptodine synapsids. Please note that over a hundred years ago, when these taxa were first studied, there were very few other basal reptile specimens to compare them to, essentially just Mesosaurus and Protorosaurus. Other casesaurs first came to light in the late 1930s. It is good that they have been finally and correctly reassigned.

Spindler, Falconnet and Fröbisch 2016 follow tradition (without testing) and nest the Caseasauria at the base of the Synapsida. The large reptile tree tests more possibilities and provides more opportunities. It nests all caseasaurs with Feeserpeton, Australothyris, Acleistorhinus and Eunotosaurus derived from millerettids, like Milleretta RC70, among the new Lepidosauromorpha, not with the Synapsida. We looked at the mistaken nesting of caseasaurs several years ago here.

Spindler et al. note: “These new observations on Datheosaurus and Callibrachion provide new insights into the early diversification of caseasaurs, reflecting an evolutionary stage that lacks spatulate teeth and broadened phalanges that are typical for other caseid species. Along with Eocasea, the former ghost lineage to the late Pennsylvanian origin of Caseasauria is further closed. For the first time, the presence of basal caseasaurs in Europe is documented.Here, we re-describe Callibrachion gaudryi and Datheosaurus macrourus for the first time in detail. The specimens are too poorly preserved to allow their inclusion in a phylogenetic analysis. Nonetheless, their assignment to Caseasauria is robust, therefore we attempt to discuss the historical findings as well as caseasaurian phylogenetic and evolutionary trends.”

I found no problem
including the more complete Datheosaurus in phylogenetic analysis in the large reptile tree (now 630 taxa). It nested right about where Spindler, Falconnet and Fröbisch 2016 said it would.

Boule M and Glangeaud P 1893a. Le Callibrachion Gaudryi, nouveau reptile fossile du Permien d’Autun. Bulletin de la Société d’Histoire naturelle d’Autun 6: 199–215.
Romer AS and Price LI 1940. Review of the Pelycosauria. Geological Society of America Special Papers 28: 1-538.
Schroeder H 1904Datheosaurus macrourus nov. gen. nov. sp. aus dem Rotliegenden von Neurode. Jahrbuch der Königlich Preußischen Geologischen Landesanstalt und Bergakademie 25 (2): 282–294. [reprint 1905]
Spindler F, Falconnet j and Fröbisch J 2016Callibrachion and Datheosaurus, two historical and previously mistaken basal caseasaurian synapsids from Europe. Acta Palaeontologica Polonica 61: xx-xx.
online pdf

Microleter mckinzieorum Tsuji et al., 2010

Microleter (Fig. 1) was described a few years ago (Tsuji et al. 2010) as an Early Permian parareptile (an invalid multiphyletic assembly of early reptiles). Tsuji et al. nested Microleter between millerettids and Acleistorhinus + Lanthanosuchus (another unnatural assembly).

Figure 1. Microleter in situ and reconstructed with a larger lateral temporal fenestra than originally reconstructed. The skull is 3 cm long. That's a pair of fused vomers and a left pterygoid (dorsal view) at lower right. Freehand original reconstruction by Tsuji et al. 2010 at upper left.

Figure 1. Microleter in situ and reconstructed with a larger lateral temporal fenestra than originally reconstructed. The skull is 3 cm long. That’s a pair of fused vomers and a left pterygoid (dorsal view) at lower right. Freehand original reconstruction by Tsuji et al. 2010 at upper left. Note the expansion of the quadratojugal/squamosal in the freehand drawing compared to the in situ tracing. Note the reduction of the postorbital in the freehand drawing. Note the absence of the splenial in the freehand drawing.

Character analysis
Tsuji et al. used the matrix of Modesto et al. (2009) which was based on Mülller and Tsuki (2007) consisting of 30 taxa and 137 characters. Both numbers are too small. The analysis recovered six trees in which Microleter nested in an unresolved polygamy with Australothyris and Acleistorhinus  + Lanthanosuchus at the base of the ‘ankyramorphan parareptiles’ (another unnatural assembly).

The large reptile tree (575 taxa, completely resolved) found Microleter nested between Delorhynchus and Eunotosaurus + Acleistorhinus. The clade Australothyris + Feeserpeton is the proximal outgroup. The caseasaurs and millerettids are more distant.

Figure 2. The nesting of Microleter with Delorhynchus, Acleistorhinus and Eunotosaurus.

Figure 2. The nesting of Microleter with Delorhynchus, Acleistorhinus and Eunotosaurus.

With insight Tsuji et al report, “As it is becoming increasingly clear, temporal fenestration is actually a common phenomenon among parareptiles, quite a departure for a group once termed Anapsida.”

Tsuji et al. include mesosaurs in their parareptilia and do not give them temporal fenestra. Oddly Tsuji et al nest Procolophon with Owenetta. Oddly they nest Eudibamus with Belebey. Oddly Tsuji et al nest Acleistorhinus with Lanthanosuchus, but not Eunotosaurus.They think the anapsid condition re-evolved in pareiasaurs. That’s not true. The ‘parareptile’ pseudoclade is a mess. It’s time for a thorough cleaning with more taxa.

the pterygoids produced a circular opening between them, as in Eunotosaurus, but not so exaggerated. Acleistorhinus does not have this trait. Here (Fig. 1), based on self-evident transfer techniques, the lateral temporal fenestra is reconstructed larger than Tsuji et al. drew it freehand. The lacrimal may not have contacted the naris according to the reconstruction where the maxilla contacts the nasal.

Linda A. Tsuji; Johannes Muller; Robert R. Reisz (2010). Microleter mckinzieorum gen. et sp. nov. from the Lower Permian of Oklahoma: the basalmost parareptile from Laurasia”Journal of Systematic Palaeontology 8 (2): 245–255.

Oromycter, a basal caseid, but still not a synapsid

Thanks to N. Brocklehurst for suggesting I take a look at Oromycter (Fig. 1).

Casea (above) and Oromycter (below) reconstructed and restored.

Figure 1. Casea (above) and Oromycter (below) reconstructed and restored. The relatively large naris-orbit distance is primitive. So are the simple, unserrated teeth. A curious area at the back of the maxilla would normally be considered a jugal, but the jugal is missing and would have created a lower margin for the orbit. So, I wonder, is this a very unusual extension of the quadratojugal? Or just an funky shape in the maxilla? Coin toss.

Oromycter dolesorum (Reisz 2005, latest Early Permian, Leonardian) is a basal caseid represented by a few skeletal parts, all superbly preserved. It is more primitive than other caseids in that it lacks leafy tooth serrations, has a longer lacrimal (naris-orbit distance) and a larger number of marginal teeth.

Reisz (2005) noted that caseids were unique among synapsids. (* That’s because they were ACTUALLY closer to millerettids and bolosaurids according to the large reptile tree). He noted that caseids appeared late in the evolution of synapsids, but nested at its base and that little is known about the origins of this group (* yet another reason for a large reptile tree with a larger gamut of included taxa: avoiding such by default nestings!).

Oromycter is considered by Reisz (2005) as the most basal member of the caseids. This seems more than reasonable, but has not been tested yet. Outgroup taxa include the basal CaseasauriaEothyris and Oedaleopsand beyond them Australothyris, Romeria primes and Concordia, not far from the basalmost reptile, Cephalerpeton

Caseasauria are closer to these millerttids and join other plant-eating basal reptiles (listed above) in the new Lepidosauromorpha, far from the insect-to-meat-eating synapsida (with allowance for Edaphosaurus and the various herbivores in the Therapsida. This needs to be tested on a genus-based level. Might need to rewrite a textbook or Wiki entry.

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.

Reisz R. 2005. Oromycter, a new caseid from the lower Permian of Oklahoma. Journal of Vertebrate Paleontology 25(4):905-910.

Are Diadectomorphs Reptiles (= Amniotes)?

Mickey Mortimer was kind enough to provide some interesting literature refs regarding the non-reptile status of Diadectomorphs (= Diadectes, Limnoscelis and Tseajaia). That means these taxa would have developed from tadpoles and non-amniote eggs laid in water. The large reptile tree found these taxa to be related to one another deep within the Reptilia, and also related to procolophonids, pareiasaurs, chroniosuchids and turtles. That means diadectomorphs would have laid eggs in dry areas without the young developing form tadpoles. M. Mortimer’s comments followed an earlier post linking caseasaurs and diadetids (but not as sisters, only cousins).

From M. Mortimer’s notes:
“Laurin and Reisz (1995) list several characters of Amniota. Diadectomorphs lack: [my comments follow in brackets]:
– Frontal contacting orbit. [also lacking in Eothyris, Orobates, pareiasaurs and turtles! And… among non-amniotes the frontal contacts the orbit in Cacops and Doleserpeton.]
– Occipital condyle almost as high as it is broad. [Procolophon and turtles also lack this trait.]
– Labyrinthodont infolding of enamel absent (Kemp, 2003). [Diadectes infolding of enamel also absent (double negative here), so this may be a convergent trait with Limnoscelis and labyrinthodonts].
– Axial centrum tilted anterodorsally. [I can’t comment on this hard-to-see trait].
– Cleithrum restricted to anterior edge of scapulocoracoid. [I never knew it wrapped around or did anything else.]
– Presence of three scapulocoracoid ossifications.”[often in basal reptiles (Paleothyris, Eocaptorhinus, the scapulocoracoid is completely fused.]

According to M. Mortimer: “More problematic are-
– Occipital flange of squamosal gently convex.  Even if I understood it, they say diadectomorphs’ condition may be an autapomorphy. [such gentle convexity, wherever present, is difficult to determine from drawings and photos].
– Transverse flange bearing a row of large teeth on its posterior edge.  Also in Limnoscelis, so could work with synapsid diadectomorphs. [So, Limnoscelis gets a free pass. Captorhinids, caseids, Belebey, Milleretta, etc. etc.  also lack a row of large teeth on the transverse flange.]
– Presence of astragalus.  They followed Rieppel’s (1993) model, but O’Keefe et al. (2006) showed amniotes have the same astragalar homology as Diadectes. [Okay].

M. Mortimer further reported, “Not to mention diadectomorphs aren’t even sister to caseasaurs in your tree.  You have derived diadectids by procolophonids, basal diadectomorphs strewn with Solenodonsaurus, Tetraceratops and chroniosuchians, and caseasaurs sister to various taxa usually placed in Parareptilia, and these three clades are successively less closely related to lepidosaurs.” 

No, they’re not sisters (lots of branching in the Millerettids + Caseasauria), but shared a recent common ancestor, Romeria primus.

M. Mortimer also noted that “Berman et al. (1992) and Berman (2000) both suggested diadectomorphs were the sister group of synapsids as opposed to the sister group of amniotes. Kemp (2003) analysed their evidence, concluding-
– A posterolateral corner of the skull table formed entirely or nearly entirely by the supratemporal is only found is Tseajaia, which I note would make it ambiguous synapomorphy is [if] diadectomorphs and synapsids were sister taxa.
– A long posterior expansion of postorbital that contacts supratemporal to exclude the parietal lappet from contacting the squamosal is primitively present in cotylosaurs, including basal sauropsids.
– Presence of an otic trough of the opisthotic is shared, but not by varanopids, which I note isn’t a problem if caseasaurs are basal.
– A deep, nonsculptured component of the tabular which contacts the distal end of a ventrally displaced, laterally directed paroccipital process, enclosing laterally a small, ventrally displaced, posttemporal fenestra is absent in Limnoscelis and Desmatodon, so is more likely convergent in synapsids and Diadectes.

Nicely put. All I can say is the several hundred traits used to determine the tree topology of the large reptile nested the casesaurs and diadectids where they did because they and 320+ other taxa provided the opportunity and motive. As an experiment, moving all three caseasaurs to the synapsids adds 24 steps. Caseasaurs become strange bedfellows with the basal synapsids and basal protodiapsids derived from a sister to Protorothyris.

The other thing that could be happening here, is this: the Diadectomorpha are on the primitive side of the Amniota and the Synapsida were the first clade to break off from the rest. That alone could indicate a relationship in a traditional sense. Then again, if Berman et al. 1992 and Berman 2000 included casesaurs within their suprageneric Synapsida, then they recovered what the large reptile tree recovered, sans all the other basal reptiles included in the large reptile tree but not included in their analysis.

Thank you for your thoughts, Mickey.

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.