No longer an enigma: Kudnu mackinlayi

I live for discoveries like this one,
which started as a Facebook post of the tiny specimen. This is what the LRT (Fig. 3) was built for.

Benton 1985 wrote:
“Bartholomai (1979) has described Kudnu [QMF8181], a partial snout from the early Triassic of Australia, as a paliguanid. The exact relationships of these forms to each other, and to other early ‘lizard-like’ forms are unclear (Carroll, 1975a, b, 1977; Currie, 1981c: 163-164; Estes, 1983: 12-15). Indeed, the group cannot be defined by any apomorphy, and the genera must be considered separately. As far as can be determined, all of these genera are lepidosauromorphs. Kudnu lacks the lepidosaur character X4 and the squamate character Y 1, but none of the others may be determined. Blomosaurus and Kudnu are classified here as Lepidosauromorpha, incertae sedis.”

Figure 1. Kudnu colorized using DGS and slight restored postcranially, shown 10x natural size at a 72 dpi standard screen resolution. Here's a taxon basal to Stephanospondylus, pareiasaurs and turtles. Prior workers excluded Stephanospondylus from their studies.

Figure 1. Kudnu colorized using DGS and slight restored postcranially, shown 10x natural size at a 72 dpi standard screen resolution. Here’s a taxon basal to Stephanospondylus, pareiasaurs and turtles. Prior workers excluded Stephanospondylus from their studies.

Contrad 2008 wrote:
“Other authors have followed this opinion and have described new ‘‘paliguanids’’, including Blomosaurus (Tatarinov, 1978) and Kudnu (Bartholomai, 1979). Even so, ‘‘Paliguanidae’’is widely regarded as a paraphyletic taxon and, unfortunately, the preservation of specimens constituting the known ‘‘paliguanid’’ genera (including Paliguana, Palaeagama, and Saurosternon) makes it impossible to characterize them except through plesiomorphy (Benton, 1985; Gauthier et al., 1988a; Rieppel, 1994). Thus, their position within Lepidosauromorpha is currently impossible to ascertain with any kind of precision.”

Evans and Jones 2010 wrote:
Kudnu (Australia, Bartholomai, 1979) and Blomosaurus (Russia, Tatarinov, 1978) are too poorly preserved to interpret with confidence but are probably also procolophonian.”

Figure 1. Click to enlarge. Stephanospondylus was considered a type of diadectid, but it nests with turtles and pareiasaurs, all derived from millerettids.

Figure 2.  Stephanospondylus was considered a type of diadectid, but it nests with turtles and pareiasaurs, all derived from millerettids,.. next to diadectids.

All that being said,
what does the LRT recover? In the large reptile tree (LRT, 1583 taxa, subset Fig. 3) Kudnu nests basal to Stephanospondylus (Fig. 2), a late survivor from deep in the lineage of pareiasaurs + turtles, not far from bolosaurids + diadectids + procolophonids. These clades are derived from Milleretta (Fig. 2) which was  2 to 3x larger.

Due to its small size,
Kudnu
can be considered phylogenetically miniaturized, the kind of taxon we often find at the base of many major reptile clades.

Sadly, earlier workers (see above)
were looking at the wrong candidates for sister taxa, excluding the right taxa. This is a problem that is minimized by the LRT due to its large number of taxa over a wide gamut.

Figure 1. Carbonodraco enters the LRT alongside another recent addition, Kudnu, at the base of the pareiasaurs + turtles.

Figure 2. Carbonodraco enters the LRT alongside another recent addition, Kudnu, at the base of the pareiasaurs + turtles.Figure 1. Carbonodraco enters the LRT alongside another recent addition, Kudnu, at the base of the pareiasaurs + turtles.

Once again,
you don’t need to see the fossil firsthand in a case like this. What you need is a wide gamut phylogenetic analysis like the LRT, to figure out how an enigma like Kudnu  nests with other reptiles.

If
Kudnu was earlier associated with Stephanospondylus, let me know and I will publish the citation. Otherwise, this is a novel hypothesis of interrelationships that inserts Kudnu without disturbing the rest of the LRT tree topology.


References
Bartholomai A 1979. New lizard-like reptiles from the Early Triassic of Queensland. Alcheringa: An Australasian Journal of Palaeontology 3:225–234.
Benton MJ 1985. Classification and phylogeny of the diapsid reptiles. Zoological Journal of the Linnean Society 84:97–164.
Conrad JL 2008. Phylogeny and systematics of Squamata (Reptilia) based on morphology.  Bulletin of the American Museum of Natural History 310: 182pp.
Evans SE and Jones MEH 2010. Chapter 2 The Origin, Early History and Diversification of Lepidosauromorph Reptiles in Bandyopadhyay S (ed.), New Aspects of Mesozoic Biodiversity, Lecture Notes in Earth Sciences 132, DOI 10.1007/978-3-642-10311-7_2 Springer-Verlag Berlin Heidelberg 2010

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…

References
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.

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!

Unfortunately, 
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.

References
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). www.tandfonline.com/doi/

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.”

Oddly,
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.

Notably
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.

References
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.

Oedaleops: why the post-cranial traits weaken the synapsid nesting

A recent paper
by Sumida et al. 2014 gives us our first look at the post-crania of Oedaleops (Fig. 1). That’s fantastic as many of Oedaleops’s sisters are also known from skulls only. Here is the abstract. Notes to follow are numbered in parentheses.

From the abstract: The Early Permian amniote Oedaleops is generally considered to be one of the basalmost pelycosaurian-grade synapsids (1). Thus it occupies a key position for understanding the phylogenetic relationships of basal synapsids (1) specifically and basal amniote interrelationships more generally. This assessment has until now been based almost exclusively on the remains of a single skull from the Lower Permian Cutler Formation of north-central New Mexico. The identification of additional cranial as well as numerous postcranial elements of at least three additional individuals now permits a more complete understanding of its anatomy and allows the first attempt at a partial body reconstruction of this basal pelycosaurian-grade synapsid. Oedaleops is confirmed as an extremely basal synapsid taxon, but the addition of postcranial data from Oedaleops to data matrices of earlier phylogenetic analyses unexpectedly weakens, as opposed to strengthens, support for the hypotheses of a monophyletic Eothyrididae (2).

Notes:
(1) In the large reptile tree Oedaleops and the Caseasauria nest as derived from millerettids, far from synapsids.

(2) Adding the post-cranial traits attributed to Oedaleops cements its place within the Diadectes/Casea clade derived from Milleretta. Synapsids were not the only clade to develop a lateral temporal fenestra, as everyone knows.

Figure 1. Oedaleops with newly recovered post-crania to scale. These new traits are also derived from millerettids, not synapsids.

Figure 1. Oedaleops with newly recovered post-crania to scale. These new traits are also derived from millerettids, not synapsids. The postcrania, to know one’s surprise, is short-legged and bulky.

References
Langston W 1965. Oedaleops campi (Reptilia: Pelycosauria), a new genus and species from the Lower Permian of New Mexico, and the family Eothyrididae. Bulletin of the Texas Memorial Museum 9: 1–47. online pdf
Sumida SS, Pelletier V and Berman DS 2014. New information on the basal pelycosaurian-grade synapsid Oedaleops. Vertebrate Paleobiology and Paleoanthropology 2014:7-23.
wiki/Oedaleops

Ambedus – a basal diadectid(?) with a shallow dentary

Diadectids come in many sizes, all bulky. Wiki considers them to be anamniotes (pre-reptiles), the first herbivores among tetrapods and the first tetrapods to attain large size. These are all debatable.

Ambedus pusillus (Kissel and Reisz 2004) is from the Early Permian of Ohio. It was considered the most primitive diadectid and one of the smallest. Like larger taxa, it had labiolingually broad blunt teeth with a central cusp over many of them. This genus is represented by MCZ 9436 (Fig. 1).

Kissel (2010) wrote: “Diagnosis: A small diadectid distinguishable from other members of the group by: 1) a shallow dentary; 2) relatively high maxillary and mandibular tooth count; 3) lack of a labial parapet of dentary; 4) anterior teeth of maxilla and dentary conical, in contrast to the incisiform anterior teeth of other diadectids; and 5) shallow alveolar shelf, which suggests a relatively shallow tooth implantation.”

Figure 1. Ambedus pusillus compared to candidate sister taxa. The shallow mandible and small size of this adult does not match the deep mandible found in diadectids, but more closely matches millerettids, solenodonsaurs and chroniosuchids. The outgroup of all of these taxa is Romeria primes, which has a medium depth dentary.

Figure 1. Ambedus pusillus compared to candidate sister taxa. The shallow mandible and small size of this adult does not match the deep mandible found in diadectids, but more closely matches millerettids, solenodonsaurs and chroniosuchids. The outgroup of all of these taxa is Romeria primus, which has a medium depth dentary. The labiolingually wide teeth of Ambedus connect it to diadectids, but Kissel and Reisz should have compared it to these taxa, too. You can’t be sure of basal status without including several even more basal taxa in the outgroup. Is Ambedus really a diadectid or a millerettid or a romeriid with convergent teeth? Maybe the teeth appeared first. More data would help.

Not a juvenile
Kissel (2010) wrote, “the remains described herein as A. pusillus possess none of the features that typify known juvenile individuals of previously described diadectid taxa. All elements are therefore thought to represent those of adult individuals.”

Short tooth roots
Kissel (2010) wrote, “The shallow alveolar shelf in Ambedus pusillus suggests that tooth implantation was not as deep as that in other diadectids. The shallow alveolar shelf of MCZ 9436 indicates that root length is less than crown height in Ambedus, as observed in the diadectomorphs Limnoscelis and Tseajaia.”

No dentine infolding
Kissel (2010) wrote, “In no specimen is it possible to determine if the marginal teeth of Ambedus exhibit infolding of the dentine, a feature present in all other diadectomorphs.”

No incisiform teeth
Kissel (2010) wrote, “The maxillary dentition of heretofore known diadectids consists of two incisiform teeth that are succeeded by a series of molariform cheek teeth. The maxillary dentition of Ambedus adheres to this general pattern, but the anteriormost teeth of MCZ 9436 are not incisiform.”

Unique tooth number
Kissel (2010) wrote, “MCZ 9438, a complete left dentary, possesses a complete tooth row, and a total of 22 teeth are present. Such a tooth count represents the greatest yet recorded for a diadectid, with the mandibular tooth counts of other diadectids including 14 to 18 for Diadectes, 15 for Diasparactus, 14 for Desmatodon and  17 for Orobates.”

Humerus not referred
Kissel (2010) also referred to MCZ 8667 an isolated humerus that was collected within the same vicinity as the maxillae and dentaries. Kissel wrote: “Because the humerus exhibits no features indicative of Diadectidae, it is not referred to Ambedus pusillus, and it is therefore not described herein.” 

Summary
What we learn from the above is Ambedus is not very much like other diadectids. One wonders then, is it something else? Related taxa with a shallow dentary and more teeth include Solenodonsaurus and the chroniosuchids, neither of which had diadectid teeth. Milleretta is also similar (Fig. 1). Not sure about the tooth shapes there. Then again there’s a third, perhaps more likely possibility based on tooth shape and number. Ambedus may be the romeriid root taxon for all three of these clades with a nod toward the diadectidae based on tooth shape. If so, that humerus may come back “into play.” Notably the manus of Romeria priimus is very slender and very un-diadectid-like. Not sure what the rest of it looks like. We’ll see if the humerus data helps answer those questions. Currently it’s on loan.

References
Kissel R 2010. Morphology, Phylogeny, and Evolution of Diadectidae (Cotylosauria: Diadectomorpha). Toronto: University of Toronto Press. pp. 185. online pdf
Kissel RA and Reisz RR 2004. Ambedus pusillus, new genus, new species, a small diadectid (Tetrapoda: Diadectomorpha) from the Lower Permian of Ohio, with a consideration of diadectomorph phylogeny. Annals of Carnegie Museum 73:197-212.

 

Acleistorhinus is NOT a Lanthanosuchid

In their influential JVP paper, DeBraga and Reisz (1996) nested the tiny, round-head Acleistorhinus (Fig. 1) with the much larger flat-head, Lanthanosuchus (Fig.1 ). They erected the clade Lanthanosuchoidea and defined it as the most recent common ancestor of Lanthanosuchidae and Acleistorhinus. They also defined “Parareptilia” and “Ankyramorphorpha,” none of which makes any sense in the large reptile tree.

Well, one look at these taxa and their closest kin on the large reptile tree falsifies that relationship rather neatly. The details do too.

Acleistorhinus is a sister to Milleretta (RC14) and Eunotosaurus. Lanthanosuchus is more closely related to Romeriscus and Macroleter, all three of the flathead variety.

Figure 1. Acleistorhinus is a sister to Milleretta (RC14) and Eunotosaurus. Lanthanosuchus is more closely related to Romeriscus and Macroleter, all three of the flathead variety. Pretty easy to see when they’re all lined up like this. 

Parareptilia (Olsen 1947)
We talked about the uselessness of the paraphyletic clade “Parareptilia” before. DeBraga and Reisz (1996) defined it as the most recent common ancestor of millerettids, Acleistorhinus, lanthanosuchids, Macroleter, Procolophonia and all of its descendants. According to the large reptile tree that most recent common ancestor is a sister to Romeria primus, just two nodes away from the most basal reptile known, Cephalerpeton. Delete Procolophon from this list and you get a most recent common ancestor close to the RC14 specimen of Milleretta (Fig. 1). This definition includes all living lizards and snakes as well, so many parareptiles are actually reptiles. Evidently the definition was formulated at a time when all “parareptiles” were thought to have been monophyletic and extinct. That’s no longer the case.

Ankyramorpha
DeBraga and Reisz (1996) defined “Ankyramorpha” as the most recent common ancestor of Procolophonia, Macroleter, Lanthanosuchidae, Acleistorhinus and all its descendants. Unfortunately, according to the large reptile tree, that definition includes the exact same taxa as Parareptilia. Dropping millerettids doesn’t change a thing.

Lanthanosuchoidea
DeBraga and Reisz (1996) defined “Lanthanosuchoidea” as the most recent common ancestor of Lanthanosuchidae and Acleistorhinus. In the large reptile tree that taxon is Milleretta RC14, so sans Procolophon, this clade is the same as the two previous ones since the two defining taxa are in separate clades. Lanthanosuchus belongs with Romeriscus and Macroleter. All have a wide flat skull and several other defining traits. Acleistorhinus belongs with Milleretta RC14 and Eunotosaurus (Fig. 1).

DeBraga and Reisz (1996) analyzed the relationships of Acleistorhinus using 8 taxa and 60 characters. With such a short taxon  list they obviously presupposed where Acleistorhinus would nest prior to creating their inclusion set. Their Procolophonia included procolophonids, pareiasaurs and turtles. These are paraphyletic in the large reptile tree (now 338 taxa and growing). Their Millerettidae included Milleretta, Millerosaurus and Milleropsis. These are also paraphyletic. Now Millerettidae includes only Milleretta and desendants (listed above), and no longer includes Millerosaurus and Milleropsis. Those nest  on the opposite branch of the Reptilia, the new Archosauromorpha, among the protodiapsids.

References
Cisneros et al 2004. A procolophonid reptile with temporal fenestration from the Middle Triassic of Brazil. Proceedings of the Royal Society London B (2004) 271, 1541–1546
DOI 10.1098/rspb.2004.2748
Daly E 1969. 
A new procolophonoid reptile from the Lower Permian of Oklahoma. Journal of Paleontology 43: 676-687.
DeBraga M 2001The postcranial anatomy of Procolophon (Parareptilia: Procolophonidae) and its implications for the origin of turtles. PhD thesis, University of Toronto.
DeBragra M 2003. The postcranial skeleton, phylogenetic position and probable lifestyle of the Early Triassic reptile Procolophon trigoniceps. Canadian Journal of Earth Sciences 40: 527-556.
DeBraga M and Reisz RR 1996. The Early Permian reptile Acleistorhinus pteroticus and its phylogenetic position. Journal of Vertebrate Paleontology 16(3): 384–395.
Efremov JA 1946. On the subclass Batrachosauria – an intermediary group between amphians and reptiles. USSR Academy of Sciences Bulletin, Biology series 1946:615-638.

Batrachosauria web page
wiki/Lanthanosuchus

wiki/Acleistorhinus

A tree topology change – turtles and pareiasaurs move from diadectids to millerettids

I spent last week adding taxa and running through potential problems with the large reptile tree. Several matrix boxes were rescored. The result shifted turtles + pareiasaurs from Diadectides + Procolophon  to Milleretta RC70 + Odontochelys (a near-turtle now, not a real turtle), which we discussed earlier.

An interesting shift. 
Moving pareiasaurs + Proganochelys back to Diadectes + Procolophon now adds 22 steps. Moving pareiasaurs + turtles to Eunotosaurus (following the results of Lyson et al. 2013) adds 28 steps.

The RC14 specimen of Milleretta is still in the same clade as Acleistorhinus + Eunotosaurus + Austraolthyris + Feeserpeton + Belebey + Bolosaurus. 

Maybe not as crazy as it sounds
It’s the “plain brown sparrows” like Milleretta, that lie at the bases of major clades, not the highly derived taxa, like Procolophon and Diadectes. Those become extinct. The various specimens of Milleretta have long been ignored, but they really are the keys to understanding the reptile family tree.

References
Broom R 1913. On the Structure and Affinities of Bolosaurus. Bulletin of the American Museum of Natural History 32:509-516
Broom R 1938 On the Structure of the Reptilian Tarsus: Proceedings of the Zoological Society of London, v. 133, 108, p. 535-542.
Broom R 1948. A contribution to our knowledge of the vertebrates of the Karroo beds of South Africa: Transactions of the Royal Society of Edinburgh, Endinburgh 61: 577-629.
Case EC 1907.
 
Description of the Skull of Bolosaurus striatus Cope. Bulletin of the American Museum of Natural History 23:653-658
Cope ED 1878
. Descriptions of extinct Batrachia and Reptilia from the Permian formations of Texas. Proceedings of the American Philosophical Society 17:505-530
Gow CE 1972. The osteology and relationships of the Millerettidae (Reptilia: Cotylosauria). Journal of Zoology, London 167:219-264.
Watson DMS 1954. On Bolosaurus and the origin and classification of reptiles.Bulletin of the Museum of Comparative Zoology at Harvard College,, v. 111, no. 9444-449.

wiki/Milleretta
wiki/Bolosaurus

The origin of pareiasaurs (and turtles).

Revised July 13, 2014 with a new image of Sclerosaurus.

Pareiasaur (Anthodon) and its phylogenetic predecessor, Stephanospondylus, a robust millerettid.

Figure1. Pareiasaur (Anthodon) and its phylogenetic predecessor, Stephanospondylus, a robust millerettid and an ancestor to turtles. Note the close correspondence of dorsal skull elements.

Earlier we looked at the ancestry of hard shell turtles (starting with Proganochelys) and soft shell turtles (starting with Odontochelys). According to the large reptile tree, the closest sister taxon to turtles is the clade Pareiasauria, represented above by Anthodon (Fig. 1). Stephanospondylus is basal to pareiasaurs followed more distantly diadectids, bolosaurids and ultimately Milleretta. So pareiasaurs AND turtles are sisters to diadectids and millerettids,

Figure 3. Soft shell turtle evolution featuring Arganaceras, Sclerosaurus, Odontochelys and Trionyx.

Figure 3. Soft shell turtle evolution featuring Arganaceras, Sclerosaurus, Odontochelys and Trionyx.

Sues and Reisz (2008) considered Sclerosaurus a procolophonid, but their concept of a procolophonid was much greater (includes more taxa) than is appropriate, according to the results of the large reptile tree.

References
Broom R 1938 On the Structure of the Reptilian Tarsus: Proceedings of the Zoological Society of London, v. 133, 108, p. 535-542.
Broom R 1948. A contribution to our knowledge of the vertebrates of the Karroo beds of South Africa: Transactions of the Royal Society of Edinburgh, Endinburgh 61: 577-629.
Gow CE 1972. The osteology and relationships of the Millerettidae (Reptilia: Cotylosauria). Journal of Zoology, London 167:219-264.
Hartmann-Weinberg AP 1933. Evolution der Pareiasauriden: Trudy Palaeontological institute Academe Nauk, SSSR, 1933, n. 3, p. 1-66.
Lee MSY 1997. Pareiasaur phylogeny and the origin of turtles. Zoological Journal of the Linnean Society 120: 197-280.
Owen R 1876. Descriptive and Illustrated Catalogue of the Fossil Reptilia of South Africa in the Collection of the British Museum. London, British Museum (Natural History).
Sues H-D and Reisz RR 2008. Anatomy and Phylogenetic Relationships of Sclerosaurus armatus (Amniota: Parareptilia) from the Buntsandstein (Triassic) of Europe. Journal of Vertebrate Paleontology 28(4):1031-1042. doi: 10.1671/0272-4634-28.4.1031 online

wiki/Anthodon
wiki/Deltavjatia
Deltavjatia paleocritti
wiki/Pareiasaur
Sclerosaurus paleocritti
wiki/Milleretta

More on the Origin of Turtles – Lyson et al. 2010

Lyson et al.  (2010 – available online) put together their hypothesis on the origin of turtles. In their abstract, they wrote, “We reanalysed a recent dataset that allied turtles with the lizard–tuatara clade and found that the inclusion of the stem turtle Proganochelys quenstedti  and the ‘parareptile’ Eunotosaurus africanus  results in a single overriding morphological signal, with turtles outside Diapsida.”

Milleretta (RC14 specimen) and the Lyson et al. 2010 tree on the origin of turtles.

Figure 1. Milleretta (RC14 specimen) and the Lyson et al. 2010 tree on the origin of turtles. Note the broad ribs already developing in Milleretta, a sister to Acleistorhinus and Eunotosaurus. On its face this seems like a slam dunk for Eunotosaurus and turtles. However, according to the large reptile tree the origin of turtles parallleled the origin of Eunotosaurus. Missing from the Lyson et al. 2010 analysis is Romeria primus and Stephanospondylus, which are closer to the lineage of turtles. A sister to Romeria primus is the last common ancestor of Eunotosaurus and turtles.

Unfortunately,
Lyson et al. (2010) did not include Romeria primusOrobates (Fig. 2) and Stephanospondylus, three taxa found to be closer to the origin of turtles than Eunotosaurus, a terminal taxon with only one known sister, Acleistorhinus. Unfortunately we have no post-crania for Romeria primus (other than slender manual digits) or Acleistorhinus. That lack of data makes it less obvious how they are related to other taxa, but still the large reptile tree nested them in that fully resolved tree. Stephanospondylus was also the sister to the pareiasaurs, a derived clade previously and correctly associated with turtles, but only at the bases of both clades.

Click to enlarge. These skulls are arranged phylogenetically according to the results recovered from the large reptile tree.

Figure 2. Click to enlarge. These skulls are arranged phylogenetically according to the results recovered from the large reptile tree. This was first published a few days ago.

Would be nice to find the common ancestor of both pareiasaurs and turtles, something a little less turtle-like than Stephanspondylus. For now, Orobates(in yellow, Fig. 2) is the best candidate, and prior to that, Romeria primus (in pink). Orobates and Stephanospondylus are Early Permian. The two turtles are Late Triassic. That gives 60-70 million years to evolve a carapace and plastron, plenty of time for transitional taxa to be discovered in. 

Eunotosaurus

Figure 3. Eunotosaurus, a milleretid not related to turtles, but converged with them in several ways. Actually Eunotosaurus is closer to Acleistorhinus and the Caseasauria, which makes sense if put these two together, like Clark Kent and Superman.

Lyson et al. 2012 did find turtle genes closer to lizard genes, while others did not.

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
Broom R 1924. On the classification of the reptiles. Bulletin of the American Museum of Natural History 51:39-45.
Geinitz HB and Deichmüller JV 1882. Die Saurier der unteren Dyas von Sachsen. Paleontographica, N. F. 9:1-46.
Gregory WK 1946. Pareiasaurs versus placodonts as near ancestors to turtles. Bulletin of the American Museum of Natural History 86:275-326
Kissel R 2010. Morphology, Phylogeny, and Evolution of Diadectidae (Cotylosauria: Diadectomorpha). Toronto: University of Toronto Press. pp. 185. online pdf
Li C, Wu X-C, Rieppel O, Wang L-T, Zhao L-J 2008. An ancestral turtle from the Late Triassic of southwestern China. Nature 456: 497-501.
Lyson TR, Bever GS, Bhullar B-AS, Joyce WG and Gauthier JA. 2010. Transitional fossils and the origin of turtles. Biology Letters 2010 6, 830-833 first published online 9 June 2010. doi: 10.1098/rsbl.2010.0371
Lyson TR, Sperling EA, Heimberg AM, GauthierJA, King BL, and Peterson KJ 2011. MicroRNAs support a turtle + lizard clade. Biol Lett 2011 : rsbl.2011.0477v1-rsbl20110477.abstract – online news story
Reisz RR and Head JJ 2008. Turtle origins out to sea. Nature 456, 450–451.
Rieppel O and deBraga M 1996. Turtles as diapsid reptiles. Nature 384:453-454.
Rieppel O and Reisz RR 1999. The Origin and Early Evolution of Turtles. Annual Review of Ecology and Systematics 30: 1-22.
Romer AS 1925. Permian amphibian and reptilian remains described as Stephanospondylus. Journal of Geololgy 33: 447-463.
Stappenbeck R 1905. Uber Stephanospondylus n. g. und Phanerosaurus H. v. Meyer: Zeitschrift der Deutschen Geologischen Gesellschaft, v. 57, p. 380-437.
Williston SW 1917. The phylogeny and classification of Reptilies. Journal of Geology 28: 41-421.

wiki/Stephanospondylus