Vaughnictis (Brocklehurst et al. 2016): a new last common ancestor of birds and bats

Recently Brocklehurst et al. 2016
renamed ‘Mycterosaurus’ smithae (Lewis and Vaughn 1965; early Permian, MCZ 2985). The new name is Vaughnictis smithae. The specimen was originally considered a varanopid close to the holotype of Mycterosaurus (Fig. 1). Now the Brocklehurst team nest the MCZ 2985 specimen between Eothyris and Oedaleops (Fig. 1) at the base of the Caseasauria, which they consider a clade at the base of the Synapsida.

Unfortunately, 
the large reptile tree nests Vaughnictis at the bases of two major clades: between Protorothyris and the Synapsida (represented here (Fig. 1) by Elliotsmithia) + the Prodiapsida (represented here by Mycterosaurus). The Caseasauria, as noted five years ago here, does not nest with the Synapsida when the taxon list is expanded, and the Prodiapsida (former varanopids) split from the Synapsida at their base when the taxon list is expanded.

Figure 2. Vaughnictis nests between Protorothyris and the Synapsida (Elliotsmithia) + Prodiapsida (Mycterosaurus) in the large reptile tree - not the Caseasauria (Eothyris + Oedaleops).

Figure 1. Vaughnictis nests between Protorothyris and the Synapsida (Elliotsmithia) + Prodiapsida (Mycterosaurus) in the large reptile tree – not the Caseasauria (Eothyris + Oedaleops). Despite the many similarities, the narrow skull with parallel sides, upturned mandible tip and longer rostrum are a few traits that split Vaughnictis from caseasaurs and lump it with prosynapsids.

Lewis and Vaughn got it right.
Vaughnictis is a sister to Mycterosaurus in the LRT. It is not a caseasaur.

Brocklehurst et al. got it right
in that Vaughnictis is distinct enough from Mycterosaurus to warrant its own genus.

Despite their phylogenetic distance
only 22 additional steps are needed when Vaughnictis is force shifted over to Eothyris. This is largely due to convergence. Both clades developed lateral temporal fenestrae in similar patterns, had large eyes and a short rostrum at this stage.

Figure 2. Vaughnictis skull in situ with color tracings. See figure 3 for reconstruction.

Figure 2. Vaughnictis skull in situ with color tracings. See figure 3 for reconstruction. The jaws shifted posteriorly during taphonomy The parietal and its opening are difficult to read.

The phylogenetic importance of Vaughnictis
was overlooked by Brocklehurst et al. It is the most primitive known specimen in the lineage of synapsids and diapsids to have a lateral temporal fenestra. That’s why it is the last common ancestor of bats and birds, an honor formerly earned by Protorothyris, but now superseded by a taxon with lateral temporal fenestrae.

Figure 1. Color tracings of bones moved to their in vivo positions and traced.

Figure 3. Color tracings of bones moved to their in vivo positions and traced. Note the anterior shifting of the jaws to their in vivo positions based on posterior dentary and jugal positions common to most if not all candidate sister taxa. 

I wish that Brocklehurst et al. had 

  1. created a multi-view reconstruction
  2. showed candidate sisters side by side compared to Vaughnictis
  3. not excluded pertinent taxa (diapsids for the former varanopids and millerettids for the caseasaurs)
  4. used colors to identify bones, rather than lines, which helps when bones overlap. They did color the teeth (Fig. 4), but not all the teeth.
Figure 6. Teeth scanned by Brocklehurst fit to dorsal view of skull. Premaxillary and maxillary teeth were not published. Note the scale bar for the teeth appears to be off by a factor of 2.

Figure 4. Teeth scanned by Brocklehurst fit to dorsal view of skull. Premaxillary and maxillary teeth were not published. Note the scale bar for the teeth appears to be off by a factor of 2. Also note the premaxillary teeth appear to be jammed back from their in vivo position. 

The interesting thing about their cladogram
is that the Brocklehurst team nested Captorhinus, Limnoscelis and Tseajaia as outgroup taxa — which is correct for Caseasauria, but not for Synapsida. Protorothyris is also listed as the proximal outgroup to the Caseasauria (incorrect) + Synapsida (correct). It is clear they rely on tradition, rather than testing for their inclusion set.

In Vaughnictis, as opposed to Eothyris, note the 

  1. relatively narrow skull
  2. the rising mandible tip
  3. the lack of maxilla/orbit contact
  4. the shorter temporal length
  5. the lower rostrum

These traits ally Vaughnictis with Elliotsmithia to the exclusion of basal caseasaurs.

Brocklehurst et al. note:

  1. Vaughnictis lacks these mycterosaurine and varanopid traits (but it is not a member of either of these clades in the LRT) :
    a. slender femur
    b. linguo-labially compressed and strongly recurved teeth – I disagree, the teeth are indeed recurved
    c. lateral boss on the postorbital – I don’t see this on candidate taxa
  2. Vaughnictis has these caseasaur traits:
    a. coronoid teeth – plesiomorphic for synapsids, but they have been lost in derived caseids, ophiacodontids, varanopids and sphenacodontians. Most workers do not include these in their tracings of pertinent taxa, so are rarely noted.
    b. large supratemporal – actually they are long, as in synapsids, not large (and wide) as in caseasaurs
    c. large pineal foramen – unable to confirm, but Elliotsmithia and Mycterosaurus also have a large pineal foramen.

Teeth
Broklehurst et al. published synchrotron scans of the palatal, dentary and coronoid teeth (perhaps the scale bar should be 1 cm, not 5mm, Fig. 4), but did not publish scans of the maxillary teeth. All of the palatal teeth form shagreen fields, not single rows. That’s different than all candidate sister taxa, whether caseasaurid or protorothyrid. What they label as “vomerine teeth” may be premaxillary teeth based on the posterior displacement of the jaws. The dentary teeth are recurved and robust. Coronoid and parasphenoid teeth are present.

Figure 6. Subset of the large reptile tree showing the nesting of Vaughnictis at the base of the Synapsida and Prodiapsida.

Figure 5. Subset of the large reptile tree showing the nesting of Vaughnictis at the base of the Synapsida and Prodiapsida. Also note that the Synapsida is NOT the first clade to branch off from the base of the Amniota. Far from it.

This Brocklehurst team was led by
the venerable Robert Reisz, who has made dozens of great discoveries, but has resisted testing candidates suggested by the large reptile tree. And that sort of paleoxenophobia is unfortunate. Outsiders can make valuable contributions.

Finally, kudos and credit to the Brocklehurst team,
for finding the one best specimen closest to the advent of the Synapsida + Prodiapsida. It should be in every textbook from here on out.

References
Brocklehurst N, Reisz RR, Fernandez V and Fröbisch 2016. A Re-Description of ‘Mycterosaurus’ smithae, an Early Permian Eothyridid, and Its Impact on the Phylogeny of Pelycosaurian-Grade Synapsids. PLoS ONE 11(6):e0156810. doi:10.1371/journal.pone.0156810
Lewis GE, Vaughn PP 1965. Early Permian vertebrates from the Cutler Formation of the Placerville Area, Colorado. Geological Survey Professional Paper 500C: 1–50.
Reisz RR, Dilkes DW and Berman DS 1998. Anatomy and relationships of Elliotsmithia longiceps Broom, a small synapsid (Eupelycosauria: Varanopseidae) from the late Permian of South Africa. Journal of Vertebrate Paleontology 18(3):602-611.

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When Synapsids and Diapsids split

At some point
on every reptile cladogram the Synapsida emerges and somewhere else the Diapsida emerges.

In contrast to all prior cladograms,
on the large reptile tree, the traditional Diapsida is diphylletic, with lepidosaurs no longer related to archosaurs except by way of the basalmost Viséan reptiles (at the archosauromorph/ lepidisauromorph split). The reduced Diapsida (sans lepidosaurs) arises from the Prodiapsida, which splits from the Synapsida at the common base of both clades, near Protorothyris (Fig. 1), a basal archosauromorph. What happened at that split is today’s topic.

One of the basalmost synapsids
is Varanosaurus. One of the basal prodiapsids is Heleosaurus (Fig. 1). Both have a synapsid temporal morphology. Among traditional paleontologists, both are considered traditional synapsids.

Now let’s take a look
at some of the characters that split these sister taxa that otherwise share so many traits and put forth some hypotheses as to what they may mean in the grand scope of reptile evolution.

Figure 1. Taxa at the split between Synapsida and Diapsida (Prodiapsida): Varanosaurus and Heleosaurus to scale along with their common ancestor, Protorothyris.

Figure 1. Taxa at the split between Synapsida and Diapsida (Prodiapsida): Varanosaurus and Heleosaurus to scale along with their common ancestor, Protorothyris.

In many respects,
Varanosaurus was just a bigger Heleosaurus. And both were much larger than their predecessor, Protorothyris. So size was a major factor in the Early Permian. Basal synapsids were larger than prodiapsids and both were larger than their Carboniferous predecessors.

Distinct from Varanosaurus,
Heleosaurus had 19 rather minor traits in the large reptile tree. As a rule they’re not very interesting or informative (but see the next topic header):

  1. Remained < 60 cm long
  2. Slightly wider skull relative to height at orbit
  3. The nasal shape retains ‘narrows anteriorly’ description (not arrowhead)
  4. Orbit stays in anterior half of the skull
  5. Supratemporal/squamosal overhang
  6. Shorter jugal quadratojugal process
  7. Quadrate rotates to vertical
  8. Lateral temporal fenestra larger, circumtemporal bones more gracile
  9. Occiput remains close to quadrates
  10. Basipterygoid lateral processes prominent
  11. Mandible tip straight
  12. Mandible fenestra remains absent
  13. Olecranon process not present (Heleosaurus clade only)
  14. Clavicles medially not broad
  15. Radius + ulna > 3x longer than wide
  16. Retained pubis angled ventrally
  17. Acetabulum opens ventrally (Heleosaurus clade only)
  18. Tibia < 2x ilium length
  19. Dorsal osteoderms present (restricted to Heleosaurus

In summary,
these Heleosaurus traits break down to four major and a few minor distinctions from Varanosaurus:

  1. Smaller size, larger orbit, shorter rostrum, relatively less bone in the skull – all attributable to neotony (retention of embryo/juvenile traits)
  2. Relatively longer hind limbs and more slender tail (shorter chevrons and transverse processes (ribs). Together these two make prodiapsids speedy, not lumbering. Ideal for avoiding larger enemies and attacking insect prey.
  3. Relatively larger orbit: possible nocturnal hunter.
  4. Longer, more gracile ribs: fast locomotion requires more efficient and rapid respiration provided by expanding ribs
  5. Minor traits: Fewer teeth, ‘solid’ palate, larger choanae: all part of the insectivore, rapid respiration bauplan.

In my opinion
the smaller size of Heleosaurus helped it retain an insect diet, rather than moving into carnivory, piscivory or herbivory, as proposed for the pelycosaurs. Heleosaurus was probably faster and more agile than its larger and smaller relatives, better adapted to hunt insects and avoid predators.

Later taxa
‘improved’ on these traits as the clade Diapsida appeared, followed quickly by a division into terrestrial younginiforms and aquatic younginiforms.

These lizardy archosauromorph diapsids competed with
outwardly similar lepidosauromorphs lepidosaur pseudo-diapsids, like Tjubina. The lepidosaur branch retained insectivory, for the most part. The archosauromorph branch did not, for the most part, with the exception that several extant mammals and birds today are insectivores.

New reconstruction of Mycterosaurus, a basalmost protodiapsid

Earlier here and here we looked at Mycterosaurus (Fig. 1). This cat-sized taxon nests as a basalmost protodiapsid (along with Archaeovenator), not far from the basalmost synapsids, Aerosaurus, Varanops etc. and their last common ancestor, Protorothyris, a basal taxon which does not have a lateral temporal fenestra. Other basal protodiapsids include Milleropsis and Erpetonyx and these ultimately give rise to diapsids like Spinoaequalis and Petrolacosaurus in the large reptile tree. This new reconstruction (Fig. 1) is based on more precise data from Berman and Reisz (1982) than originally available from Williston (1915).

Figure 1.Mycterosaurus. Click to enlarge. This is a sister to the basalmost protodiapsid, and thus an ancestor of birds and crocs.

Figure 1.Mycterosaurus. Click to enlarge. This is a sister to the basalmost protodiapsid, and thus an ancestor of birds and crocs. There is an interesting shift in the dorsal vertebral neural spines that is not present in related taxa.

This subset of the large reptile tree (Fig. 2) shows relationships at the base of two large clades of reptiles, Synapsida and Diapsida (sans lepidosauriformes, which have convergenently developed a similar temporal morphology).

Figure 2. A subset of the large reptile tree showing the relationships of protosynapsids, synapsids, protodiapsids and diapsids. Traditionally nested with synapsids as varanopids, the protodiapsids have rarely, if ever, been tested with diapsids.

Figure 2. A subset of the large reptile tree showing the relationships of protosynapsids, synapsids, protodiapsids and diapsids. Traditionally nested with synapsids as varanopids, the protodiapsids have rarely, if ever, been tested with diapsids.

Mycterosaurus longiceps (Middle Permian, Williston 1915, Berman and Reisz 1982) nested with Heleosaurus as a basal protodiapsid. Botha-Brink and Modesto (2009) also correctly nested it with Mesenosaurus and Heleosaurus but considered those taxa varanopid synapsids unrelated to diapsids. 

The tip of the snout is unknown in Mycterosaurus, but probably straight as in sister Heleosaurus. Berman and Reisz 1982 considered the AMNH 7002 specimen (above) another Mycterosaurus, but it has recurved canines more like those of Mesenosaurus, the maxilla is lower and the jugal had a different shape.

No DNA studies link mammals (synapsids) to birds and crocs (diapsids) yet embryological studies show that both develop of jugal with a quadratojugal process, something lizard and turtle embryos do not produce. I continue to be perplexed about DNA vs. morph studies. But I also continue to urge cladogram builders to include key taxa, like Mycterosaurus in studies on basal diapsids and vice versa.

References
Berman DS and Reisz RR 1982. Restudy of Mycterosaurus longiceps (Reptilia, Pelycosauria) from the Lower Permian of Texas. Annals of Carnegie Museum 51, 423–453.
Botha-Brink J and Modesto SP 2009. Anatomy and Relationships of the Middle Permian Varanopid Heleosaurus scholtzi Based on a Social Aggregation from the Karoo Basin of South Africa. Journal of Vertebrate Paleontology 29(2):389-400.
Broom R 1907. On some new fossil reptiles from the Karroo beds of Victoria West, South Africa. Transactions of the South African Philosophical Society 18:31–42.
Willistion SW 1915. A New Genus and Species of American Theromorpha: Mycterosaurus longiceps. The Journal of Geology 23(6):554-559.
wiki/Mycterosaurus

Skulls at the Protodiapsid/Synapsid Split

Updated February 23, 2015 with a new image of Mycterosaurus.

Earlier we looked at taxa at the Protodiapsid/Synapsid split. Here’s an update with skulls alone after the addition of two Protorothyris skulls (Fig. 1).

Figure 1. Reptile skulls at the protodiapsid/ synapsid split to scale with Protorothyris as the proximal outgroup. Note the elongation of the rostrum and the appearance of the the lateral temporal fenestra. The two clades were originally quite similar. Two versions of Mycterosaurus are shown. Click to enlarge.

Figure 1. Reptile skulls at the protodiapsid/ synapsid split to scale with Protorothyris as the proximal outgroup. Note the elongation of the rostrum and the appearance of the the lateral temporal fenestra. The two clades were originally quite similar. Two versions of Mycterosaurus are shown. Click to enlarge.

Descending from a sister
to Coelostegus, Protorothyris (Fig. 1) nests as the proximal outgroup to the split between the Synapsids and Protodiapsids (which gave rise to the Diapsida). The narrower skull of the more derived MCZ 2149 specimen of Protorothyris continues in both clades. The relatively short rostrum of the MCZ 2149 specimen of Protorothyris was an autapomorphy.

Both protodiapsid and synapsid clades display 

  1. a new lateral temporal fenestra (with concurrent temporal bone shape changes)
  2. a longer rostrum
  3. longer ascending process of the premaxilla
  4. the maxilla was at least as deep as the lacrimal
  5. the pineal opening was larger
  6. the frontal was not so narrow
  7. the supratemporal contacted the postorbital
  8. the cervical ribs were not robust and parallel to the centra
  9. metatarsal 1 was less than half of metatarsal 3
  10. pedal 5.1 did not extend beyond metatarsal 4

In basal protodiapsids

  1. the naris was ventrally bordered by the maxilla chiefly.
  2. the maxilla expanded dorsally, blocking contact between the lacrimal and naris, but only in the Heleosaurus/Mycterosaurus/Mesenosaurus clade. Other protodiapsids and basal diapsids did not have his trait.
  3. the naris was elongated
  4. the nasals and frontals were subequal
  5. the basipterygoid processes were prominent
  6. retroarticular process descended
  7. cervical neural spines were not taller than the centra
  8. medially the clavicles were not broad
  9. the coracoid, even when fused, was larger than the scapula
  10. the radiale and intermedium were elongated
  11. the radius and ulna were together longer than 3x their width
  12. the tibia is not less than twice the ilium length

In basal synapsids

  1. the naris is ventrally bordered by the premaxilla ventrally.
  2. most of this clade had nasals longer than frontals
  3. most taxa had a convex ventral maxilla (but so did Helosaurus).
  4. the occipital was anterior to the jaw joint
  5. broader supraoccipital
  6. mandible tip rises
  7. retroarticular process rises
  8. transverse processes appear on the vertebrae
  9. the manus and pes were subequal
  10. the ilium is longer than tall
  11. the pelvic elements are fused
  12. pedal 4.1 is shorter than three times its width
  13. overall length longer than 30cm

This phylogenetic split has not been recognized in academic literature as generic diapsids are rarely to never tested with basal synapsids.

References
Clark J and Carroll RL 1973. Romeriid Reptiles from the Lower Permian. Bulletin of the Museum of Comparative Zoology 144 (5): 353-408 .
Price LI 1937. Two new Cotylosaurs from the Permian of Texas: Proceedings of the New England Zoological Club, v. 16, p. 97-102.
wiki/Protorothyris

Variation in Mesenosaurus and Mycterosaurus

Updated February 23, 2015 with a new image of Mycterosaurus.

Mesenosaurus romeri (Efremov 1938, Reisz and Berman 2001) Late Carboniferous to Early Permian ~300 to ~260 mya was originally considered a varanopseid, like Varanops, but it lies outside the varanopsids and outside the synapsids when tested against a larger list of taxa. Here Mesenosaurus was derived from a sister to Archaeovenator and phylogenetically preceded Milleropsis within the Protodiapsida and Eudibamus and Petrolacosaurus within the Diapsida (sans Lepidosauriformes, which nest elsewhere).

The clade of Heleosaurus + Mycterosaurus is a sister to Mesenosaurus (Fig. 1).

Figure 1. Mesenosaurus skulls compared to sisters Heleosaurus and Mycterosaurus. Note the greater angularity of the skull shapes along with the wider posterior skulls in derived taxa (toward the bottom). The SGU specimen needs better data on the squamosal, which is illustrated as missing its ventral/lateral portion here.

Figure 1. Mesenosaurus skulls compared to sisters Heleosaurus and Mycterosaurus. Note the greater angularity of the skull shapes along with the wider posterior skulls in derived taxa (toward the bottom). The SGU specimen needs better data on the squamosal, which is illustrated as missing its ventral/lateral portion here.

The Mycterosaurus question
The Mycterosaurus in figure 1 was illustrated by Williston in 1915. Bones attributed to Mycterosaurus by Reisz et al. 1996 are shown in figure 2. The tooth shapes are not the same. The depth of the maxilla is not the same. Yet the tooth shapes in the Williston image are not the same as those in Heleosaurus and Mesenosaurus. The Reisz et al. images are more similar.

Figure 2. Mycterosaurus bones from a fissure fill formation. Typically such bones are individually preserved, so their association with each other and with a certain genus and species is due to the expert eye of a paleontologist. I note differences in the shapes of Mycterosaurus here compared to the Williston specimen/reconstruction in figure 1. So, the data is confusing.

Figure 2. Mycterosaurus bones from a fissure fill formation. Typically such bones are individually preserved, so their association with each other and with a certain genus and species is due to the expert eye of a paleontologist. I note differences in the shapes of Mycterosaurus here compared to the Williston specimen/reconstruction in figure 1. So, the data is confusing.

Sometimes one trusts an illustration…
especially if that’s the only available data. Other times, especially if the illustration is old, the trust is reduced. Howecer, the holotype is the benchmark. Fissure fill specimens, disarticulated as they are, and recent figures are typically more accurate. But how do they relate to the holotype?

If anyone has better data on the holotype of Mycterosaurus,
like a photograph of, please send it and the accuracy of the large reptile tree will be enhanced.

References
Efremov JA 1938. Some new Permian reptiles of the USSR. Academy of Sciences URSS, C. R., 19: 121-126.
Reisz RR and Berman DS 2001. The skull of Mesenosaurus romeri, a small varanopseid (Synapsida: Eupelycosauria) from the Upper Permian of the Mezen River basin, northern Russia. Annals of the Carnegie Museum 70: 113-132. online pdf
Reisz RR, Wilson H and Scott D 1996. Varanopseid synapsid skeletal elements form Richards Spur, a Lower Permian fissure fill near Ft. Sill, Oklahoma. Oklahoma Geology Notes 56 (3):160-170.

wiki/Mesenosaurus

Erpetonyx, not a bolosaurid, but a milleropsid (protodiapsid)

Updated January 19, 2015 with new reconstruction and skull.

A new paper
by Modesto et al. (2014) describes a new Late Carboniferous reptile, Erpetonyx arsenaultorum (Fig. 1, ROM 55402, 303.7 to 298.9 Ma).

First in 20 years!
Erpetonyx arsenaultorum is the first Carboniferous reptile to be described in nearly two decades.

It made the news!
From the CBC website: “A fossil of a lizard-like creature found by a boy on a Prince Edward Island beach is a new species and the only reptile in the world ever found from its time, 300 million years ago, a new study shows.”

Complete but crushed,
with a disarticulated skull and extremities, this protodiapsid was considered a bolosaurid by Modesto et al, likely because it nests very close to Eudibamus, a basal diapsid they consider to be a bolosaurid. We looked at Eudibamus earlier here.

One mistake makes the next mistake easier to make.
Bolosaurids are turtle and pareiasaur sisters with crushing teeth. Note the long, narrow teeth of Erpetonyx (Fig. 1) more closely resemble those of Milleropsis (Fig. 2). This is an on-going issue.

Parareptile? 
Modesto et al. also support the paraphyletic clade Parareptilia and list Erpetonyx among them (Fig. 1). According to Modesto, et al., parareptilia (Fig. 1) is a clade nesting between Synapsida and Eureptilia (all the rest of the Amniota).

Unfortunately,
adding taxa, as in the large reptile tree, splits up most of the ‘parareptiles’. Mesosaurs nest with ichthyosaurs and thalattosaurs. The conventional millerosaurs, Milleroposis (Fig. 2) and Milleretta, are not related to each other. Procolophonids are derived from diadectids, not pareiasaurs. Australothyris is related to Milleretta and caseasaurs, not Lanthanosuchus. However, Lanthanosuchus, Microleter and Nyctiphruretus are related, not to far from bolosaurids, pareiasaurs and turtles.

Figure 1. Click to enlarge. When you put the hands and feet and skull back together, you find Erpetonyx nests close to Eudibamus, but closer to Milleropsis.

Figure 1. Click to enlarge. When you put the hands and feet and skull back together, you find Erpetonyx nests close to Eudibamus, but closer to Milleropsis.

The Late Carboniferous age
of Erpetonyx does precede that of its relatives, Broomia (Middle Permian) and Milleropsis (Early Permian), but a more derived taxon, Petrolacosaurus, is also Late Carboniferous in age.

Milleropsis, a largely forgotten taxon that displays possible bipedal traits at the base of the Diapsida.

Figure 1. Milleropsis, a largely forgotten taxon that displays possible bipedal traits at the base of the Diapsida. Note the long stiff tail without chevrons, as in Erpetonyx.

The carpus of Erpetonyx
is distinctive and quite similar to that of Broomia (Fig. 3). The original diagnosis of Erpetonyx makes note of the carpus. From the text: “A small, basal parareptile that possesses 29 pre sacral vertebrae (viz. five cervicals and 24 dorsals), relatively small carpal bones (the radiale and the pisiform are ca one-half the size of the ulnare and the fifth distal carpal, respectively), a femoral distal end with an epicondylar axis at 45º to the shaft, a fourth metatarsal with a relatively broad distal end, and well-developed unguals with prominent flexor tubercles.”

Figure 1. Broomia. A long-recognized sister to Milleropsis, an early possible biped. Check out those thighs!

Figure 3. Broomia. Another long-recognized sister to Milleropsis, an early possible biped close to Erpetonyx. Note the similarities in the carpus and tarsus.

Bolosauria
The authors resurrect the name Bolosauria, which was erected as an ordinal name by Kuhn to contain the family Bolosauridae Cope, 1878, and define it as a branch-based group: Bolosaurus striatus Cope, 1878 and all species related more closely to it than to Procolophon trigoniceps Owen, 1876. Unfortunately the last common ancestor of these two taxa in the large reptile tree is Saurorictus and Erpetonyx does not nest in this clade. The authors did not provide reconstructions.

Figure 6. Detail of skull tracings and reconstruction of Erpetonyx skull. The new data nests Erpetonyx closer to Milleropsis.

Figure 6. Detail of skull tracings and reconstruction of Erpetonyx skull. The new data nests Erpetonyx closer to Milleropsis. The prefrontal is broken up. The original frontal is now a lacrimal. 

References
Modesto SP, Scott DM, MacDougall MJ, Sues H-D, Evans DC and Reisz RR 2014. The oldest parareptile and the early diversification of reptiles. Proc. R. Soc. B 282:
20141912. http://dx.doi.org/10.1098/rspb.2014.1912

Pyozia – close to Orovenator

Wikipedia reports, “Pyozia (Fig. 1) is an extinct genus of basal Middle Permian varanopid synapsid known from Russia. It was first named by Jason S. Anderson and Robert R. Reisz in 2004 and the type species is Pyozia mesenensisPyozia mesenensis is known from the holotype PIN 3717/33, a three-dimensionally preserved partial skeleton including a nearly complete skull. It was collected from the Krasnoschelsk Formation, dating to the Capitanian stage of the Guadalupian epoch, about 265.8-263 million years ago.”

Pyozia in situ. Not much is known, but enough to nest it with Orovenator in the protodiapsida.

Pyozia in situ. Not much is known, but enough to nest it with Orovenator in the protodiapsida.

Anderson and Reisz (2004) nested Pyozia between Archaeovenator and Mycterosaurinae + Vanranodontidae.

In the large reptile tree (not yet updated) Pyozia nests with Orovenator (Fig 2) in the protodiapsida, which includes Archaeovenator and Mycterosaurus, outside of the Synapsida, which includes Varanops and Varanodon.

Figure 1. Orovenator (holotype on right) along with the larger referred specimen (on left, and scaled down to the size of the holotype above right). Arrows point to mismatches.

Figure 2. Orovenator (holotype on right) along with the larger referred specimen (on left, and scaled down to the size of the holotype above right). Arrows point to mismatches.

Reisz et al. 2011 nested Orovenator with Lanthanolania (a rib glider known from a skull only) and basal diapsids like Araeoscelis and basal Younginiformes like Tangasaurus, but Reisz et al. included the referred specimen, which has upper temporal fenestra. The holotype and referred specimens show several differences among the bones they share in common, so probably they are not related. Their combination creates a chimaera with traits not present in the holotype. Better to test just the holotype.

References
Anderson JS and Reisz RR 2004. Pyozia mesenensis, a new, small varanopid (Synapsida, Eupelycosauria) from Russia: “pelycosaur” diversity in the Middle Permian. Journal of Vertebrate Paleontology 24: 173–179.
Reisz RR, Modesto SP and Scott DMT 2011. A new Early Permian reptile and its significance in early diapsid evolution. Proceedings of the Royal Society, London B doi:10.1098/rspb.2011.0439