Kapes: a new procolophonid with long cheeks

Zaher, Coram and Benton 2018
bring us a new procolophonid, Kapes bentoni, with long cheek bones (Fig. 1).

Figure 1. Kapes bentoni. Perserved parts are in gray.

Figure 1. Kapes bentoni. Perserved parts are in gray.

Unfortunately,
Zaher, Coram and Benton have no idea how their included taxa are related to one another because they exclude so many pertinent taxa (Fig. 2), as determined by the large reptile tree (LRT, 1280 taxa). Infamously, Dr. Benton purposefully deleted taxa in prior works. Not sure why that was also done here.

Figure 2. Cladogram from Zaher, Coram and Benton excluding so many pertinent taxa present in the LRT that the phylogenetic order is here reversed.

Figure 2. Cladogram from Zaher, Coram and Benton excluding so many pertinent taxa present in the LRT that the phylogenetic order is here reversed.

Workers don’t have to believe
the hypothesis of relationships proposed by the LRT, but it would profit them to at least include the pertinent taxa shown revealed by the LRT.

References
Zaher M, Coram RA and Benton MJ 2018. The Middle Triassic procolophonid Kapes bentoni: computed tomography of the skull and skeleton. Papers in Palaeontology 2018:1–28. doi: 10.1002/spp2.1232

 

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/

The plate and counterplate of Sclerosaurus

Earlier the large reptile tree nested the small pareisaur Sclerosaurus armatus (von Meyer 1857; Early to Middle Triassic; 30 cm long; Fig.1) at the base of the soft shell turtle clade (Fig. 2). This is at odds with current thinking (see below). Here the software program Adobe Photoshop enables researchers to superimpose the fossil plate upon the counterplate to provide a more complete set of data. This is the DGS method, a tried and true method for identifying bones to aid in interpretation as a prelude to creating a reconstruction. It’s much better than simply putting a label or arrow somewhere on the unoutlined bone. The only limitations are in the data available and the expertise of the interpreter.

Figure1. The plate and counter plate of Sclerosaurus, an ancestral taxon to soft shell turtled. Girdles and extremities are reconstructed.

Figure1. Click to enlarge. The plate and counter plate of Sclerosaurus, an ancestral taxon to soft shell turtled. Girdles and extremities are reconstructed. Frames change every 5 seconds. Here imposing the  plate and counter plate upon one another in Photoshop helps to reconstruct the specimen. The humerus has been rotated about 180 degrees during taphonomy.

Sclerosaurus armatus (Meyer 1859, Sues and Reisz 2008; Middle Triassic; ~50 cm in length), was originally considered a procolophonid, then a pareiasaurid, then back and forth again and again, with a complete account in Sues and Reisz (2008) who considered it a procolophonid. After Procolophon, Sues and Reisz (2008) considered TichvinskiaHypsognathus, Leptopleuron and Scoloparia sister taxa to Sclerosaurus. These all nest with Diadectes in the large reptile tree, not pareiasaurs.

Wikipedia also reports that Sclerosaurus is a procolophonid. Shifting Sclerosaurus to the procolophonids in the large reptile tree adds 55 steps.

Figure 1. New cladogram of turtle systematics. Note the separation of soft shell turtles with orbits visible in dorsal view from domed hard shell turtles with laterally oriented orbits here.

Figure 2. New cladogram of turtle systematics. Note the separation of soft shell turtles with orbits visible in dorsal view from domed hard shell turtles with laterally oriented orbits here.

Here, based on data from Sues and Reisz (2008), Sclerosaurus nests between pareiasaurs and basal soft-shell turtles like Odontochelys and Trionyx. It is a sister to Arganaceras, but was smaller with larger supratemporal horns.

FIgure 1. Sclerosaurus face.

FIgure 3. Sclerosaurus face.

Figure 4. Sclerosaurus reconstructed.

Figure 4. Sclerosaurus reconstructed.

References
Meyer H von 1859. Sclerosaurus armatus aus dem bunten Sandestein von Rheinfelsen. Palaeontographica 7:35-40.
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/Sclerosaurus

 

Adding taxa to the Diadectes clade

Adding a few
and distinct Diadectes specimens (no two appear to be conspecific) opens the door to new insights into that corner of the cladogram. Some of the data are from 3D skull images with sutures delineated. Others are from firsthand observation. Some data are from drawings. Berman et al. 1992 made an interesting observation that prior authors illustrated the skull roof of Diadectes in a variety of ways (Fig. 1). The caption does not indicate that all were drawn from the same specimen. I suspect they were not.

Figure 1. How Berman et al. copied the illustrations of prior authors who each figured the skull roof of Diadectes. Perhaps these were several distinct specimens, not just one.

Figure 1. How Berman et al. copied the illustrations of prior authors who each figured the skull roof of Diadectes. Perhaps these were several distinct specimens, not just one. Not sure, at this point, which illustrations represent which specimens.

The Berman et al. phylogenetic analysis
included seven taxa, including two suprageneric taxa, Pelycosauria and Captorhinomorpha. They included only nine characters. The anamniote, Seymouria, was the outgroup. The first clade included Pelycosauria + (Limnoscelis +(Tseajaia and Diadectes). The second clade included Captorhinomorpha + Petrolacosaurus. The large reptile tree includes hundreds more taxa and characters. The pertinent subset is shown here (Fig. 2). It is also clear from the Berman et al. taxon set that they thought they were dealing with a small set of basal reptiles and pre-reptiles. In 2015 it is clear that they did not include the pertinent taxa they should have as some of these taxa are not related to any of the others except distantly.

Figure 2. How the large reptile tree lumps and splits the several Diadectes specimens now included here. Note that bolosaurids, including Phonodus, now nest within other Diadectes specimens.

Figure 2. How the large reptile tree lumps and splits the several Diadectes specimens now included here. Note that bolosaurids, including Phonodus, now nest within other Diadectes specimens.

Now, with current data
it is becoming increasingly clear that both bolosaurids and procolophonids nest within  a fully reptilian Diadectes clade. It is also clear that the genus Diadectes needs to be further split, as Kissel (2010) started to do by renaming Silvadectes and Oradectes from former Diadectes species.

Skeleton of Diadectes. Perhaps unnoticed are the broad dorsal ribs of this taxon, basal to Stephanospondylus, Procolophon and pareiasaurs.

Figure 3. Skeleton of Diadectes (UC 706, UC 1078). Perhaps unnoticed are the broad dorsal ribs of this taxon, basal to Stephanospondylus, Procolophon and pareiasaurs.

Also note
the placement of Stephanospondylus as a proximal sister taxon to the diadectids nesting at the base of the pareiasaurs (including turtles). Turtles are sisters to pareiasaurs and they ARE pareiasaurs because they are derived from pareiasaurs, just as birds are derived from theropod dinosaurs.

Figure 4. Click to enlarge. Stephanospondylus based on parts found in Stappenbeck 1905. Several elements are re-identified here. Note the large costal plates on the ribs, as in Odontochelys. The pubis apparently connected to a ventral plastron, not preserved. The interclavicle was likely incorporated into the plastron.

Figure 4. Click to enlarge. Stephanospondylus based on parts found in Stappenbeck 1905. Several elements are re-identified here. Note the large costal plates on the ribs, as in Odontochelys. The pubis apparently connected to a ventral plastron, not preserved. The interclavicle was likely incorporated into the plastron.

Like everyone who studies prehistoric reptiles
there is a day when you don’t know anything about a taxon and later there is a day when you are making contributions to Science. Those days keep on coming.

References
Berman DS, Sumida SS and Lombard E 1992. Reinterpretation of the Temporal and Occipital Regions in Diadectes and the Relationships of Diadectomorphs. Journal of Vertebrate Paleontology 66(3):481-499.
Kissel R 2010. Morphology, Phylogeny, and Evolution of Diadectidae (Cotylosauria: Diadectomorpha). Thesis (Graduate Department of Ecology & Evolutionary Biology University of Toronto).

The Phonodus-Bolosaurus-Bashkyroleter connection

This post might be boring.
These are the unpopular, rarely studied plain-looking reptiles that ultimately gave rise to many of the most interesting clades.

Bolosaurids
are rarely studied, rarely included in phylogenetic analyses and little has been published on them. Bolosaurus and Belebey are the classic specimens. Long-legged Eudibamus has been added to this clade by traditional workers (Berman et al. 2000), but the large reptile tree nests it instead with basal diapsids, like long-legged Petrolacosaurus.

The busiest and most difficult corner
of the large reptile tree always seemed to be between Milleretta and Macroleter (Fig. 1).This subset of the tree also includes many previous enigmas here resolved, including  turtles.

Figure 1. A subset of the large reptile tree focusing on the taxa between Milleretta and Lepidosauriformes, perhaps the most difficult corner of the large reptile tree.

Figure 1. A subset of the large reptile tree focusing on the taxa between Milleretta and Lepidosauriformes, perhaps the most difficult corner of the large reptile tree.

Phonodus was originally considered a procolophonid.
(Modesto et al. 2010). Here (Fig. 2) Phonodus nests close to procolophonids, but closer to bolosaurids. As an Early Triassic taxon, Phonodus represents a late surviving member of a Late Pennsylvanian/Earliest Permian radiation that produced Early Permian diadectids and others. Based on its unusual teeth, Phonodus was highly derived.

Figure 1. Phonodus tracing. This turns out to be a basal bolosaurid.

Figure 2. Phonodus tracing. This turns out to be a basal bolosaurid, close to procolophonids. Note the deeply excavated squamosal. The naris was originally overlooked. 

A related taxon
Bashkyroleter (Fig. 3) was originally considered a nyctoleterid parareptile (not a valid clade). Here (Fig. 1) Bashkyroleter is basal to the bolosaur/diadectid/procolophon clade and pareiasaur/turtle clade AND the remainder of the lepidosauromorpha, including the lanthanosuchids proximally. So, it is a key taxon, largely overlooked except for one paper (Müller and Tsuji 2007) on reptile auditory capabilities.

Yes,
this solidification of the large reptile tree involved some topology changes. Science is self correcting. New data brings new insights. One of these new insights involved Bashykyroleter and a previously overlooked connection of the lateral to the naris. (Fig. 2).

Figure 2. Bashkyroleter appears to have a small naris/lacrimal connection.

Figure 3. Bashkyroleter appears to have a small naris/lacrimal connection as shown above. If anyone has a dorsal, occipital  or palatal view of this taxon, please send it along. Another deeply embayed squamosal. 

References
Berman, DS, Reisz RR, Scott D, Henrici AC, Sumida SS and Martens T 2000. Early Permian bipedal reptile. Science 290: 969-972.
Modesto SP, Scott DM, Botha-Brink J and Reisz RR 2010. A new and unusual procolophonid parareptile from the Lower Triassic Katberg Formation of South Africa. Journal of Vertebrate Paleontology 30 (3): 715–723. doi:10.1080/02724631003758003.
Müller J and Tsuji LA 2007. Impedance-Matching Hearing in Paleozoic Reptiles: Evidence of Advanced Sensory Perception at an Early Stage of Amniote Evolution. PLoS ONE 2 (9): e889. doi:10.1371/journal.pone.0000889. PMC 1964539. PMID 17849018

A shift in the topology of the large reptile tree

As loyal readers know…

  1. I have challenged others to find taxa that are improperly nested.
  2. So far this year no one has stepped up to the challenge. Well, they had their chance…
  3. Yesterday I discovered a mistake in the large reptile tree and made the correction (Fig. 1). The diadectomorph clade (including procolophonids) have moved closer to the bolosaurids and pareiasaurs.
Figure 1. A shift in the tree topology moves diadectids (and procolophonids) closer to pareiasaurs and away from limnoscelids. But Orobates stayed back.

Figure 1. A shift in the tree topology moves diadectids (and procolophonids) closer to pareiasaurs and away from limnoscelids. But Orobates stayed back. At the bottom of the chart, that line leads to macroleterids and nycteroleterids, then on to the lepidosauriformes and lepidosaurs.

The problem was
so much of the data for the taxa around these nodes are represented by drawings, sometimes with errors. The most difficult taxa and perhaps the least interesting of all reptiles (judging by the number of papers written about them) are also at this node: Saurorictus, Milleretta (both specimens) and the bolosaurids (sans Eudibamus, which nests with Petrolacosaurus). While a single tree was found then, and is also found now, the bootstrap scores were not strong, now or then. The present bootstrap scores could use a boost owing to the skull-only and otherwise unfortunately incomplete data in several taxa often represented only by drawings. Many taxa were rescored.

The other problem was
diadectomorphs nest pretty well with Orobates, millerettids, caseasaurs and limnoscelids. Now they nest just a little better with bolosaurs and pareiasaurs. At one point it was either way.

What sparked this change?
When I added Bashkyroleter, added data to Procolophon and Belebey, and created a new skull restoration of Sauropareion. Issues arose and I took another look at several dozen taxa.

On the plus side,
Stephanospondylus (still known from very poor data) has traditionally been considered a diadectomorph. Now it nests as a sister to that clade. Some diadectids had some widely expanded ribs, as did Stephanospondylus. Both were experimenting with a morphology that would be perfected in their now closer relatives, the turtles.

The limnoscelids and their kin, including Orobates, are all long-bodied taxa now. The diadectids plus pareiasaurs plus turtles are all shorter bodied taxa with progressively wider bodies and shorter tails.

The true procolophonids (Procolophon and kin) are now closer to the nycteroleterids and owenettids, which were traditionally associated in a large single clade. They’re still not directly related.

As noted earlier, one of the earmarks of good Science is correcting errors. I encourage the finding of errors in reptileevolutiion.com. Behind the scenes, as you already know, I make corrections and additions all the time. As mentioned earlier:

Carl Sagan (in the Demon Haunted World) wrote:
“Science has built-in error-correcting mechanisms—because science recognizes that scientists, like everybody else, are fallible, that we make mistakes, that we’re driven by the same prejudices as everybody else. There are no forbidden questions. Arguments from authority are worthless. Claims must be demonstrated. Ad hominem arguments—arguments about the personality of somebody who disagrees with you—are irrelevant; they can be sleazeballs and be right, and you can be a pillar of the community and be wrong.”

In other words,
watch out for those who hold dearly to their paradigms, whether religious or scientific. It’s okay to test those paradigms.

Alveusdectes: a small, late-surviving diadectomorph – with procolophonid cheeks

Earlier we looked at the overlooked similarities of Diadectes and Procolophon (Fig. 1).

In the large reptile tree Procolophon nests with Diadectes, and both share a large otic notch, a trait Wiki says makes Diadectes an amphibian.

Figure 1. In the large reptile tree Procolophon nests with Diadectes, and both share a large otic notch, a trait Wiki says makes Diadectes an amphibian.

In the large reptile tree these two clades (procolophonids and diadectomorphs) nest together. No one has ever seen that before or since.

A new discovery
(Liu and Bever 2015) links these two clades closer together. Unfortunately, Liu and Bever used outdated cladograms. Taxon exclusion was the source of their errors. From their abstract: “Diadectomorpha is a clade of Late Palaeozoic vertebrates widely recognized as the sister group of crown-group Amniota* and the first tetrapod lineage to evolve high-fibre herbivory**. Despite their evolutionary importance, diadectomorphs are restricted stratigraphically and geographically, with all records being from the Upper Carboniferous and Lower Permian of North America and Germany. We describe a new diadectomorph, Alveusdectes fenestralis, based on a partial skull from the Upper Permian of China. The new species exhibits the derived mechanism for herbivory and is recovered phylogenetically as a deeply nested diadectid. Approximately 16 Myr younger than any other diadectomorph, Alveusdectes is the product of at least a 46 Myr ghost lineage. How much of this time was probably spent in Russia and/or central Asia will remain unclear until a specimen is described that subdivides this cryptic history, but the lineage assuredly crossed this region before entering the relatively isolated continent of North China. The discovery of Alveusdectes raises important questions regarding diadectomorph extinction dynamics including what, if any, ecological factors limited the diversity of this group in eastern Pangea. It also suggests that increased sampling in Asia will likely significantly affect our views of clade and faunal insularity leading up to the Permo-Triassic extinction.”

* This is an error.
Diadectomorpha are derived from Milleretta and kin in the large reptile tree.

** Another error.
Basalmost lepidosauromorphs were all herbivores.

In dorsal view
the skull of Alvuedectes has a strongly triangular appearance, similar to that of procolophonids. Most of the skull must be restored because it is missing. And it can be restored in at least two ways (Fig. 2).

Figure 2. Alvuesdectes (from Liu and Bever 2015) restored and compared to Diadectes and Procolophon. Note the triangular shape of the skull in dorsal view.

Figure 2. Alvuesdectes (from Liu and Bever 2015) restored and compared to Diadectes and Procolophon. Note the triangular shape of the skull in dorsal view. Click to enlarge.

Liu and Bever did not compare
their find to any procolophonids, only diadectomorphs. This is why the large reptile tree was created, to provide an umbrella study to provide taxa for more focused studies. It is unfortunate that Liu and Bever did not reference this study, which has been online for over four years. Procolophonids continued to the Late Triassic, which makes procolophonids the “last diadectomorphs.”

References
Liu J and Bever GS 2015. The last diadectomorph sheds light on Late Palaeozoic tetrapod biogeography. Biol. Lett.11: 20150100.

 

Restoring Scoloparia as a procolophonid AND as a pareiasaur

Today I have a quandary…
Is Scoloparia a procolophonid or a pareiasaur? I’ve looked at it both ways (Figs. 1, 2). It nests both ways (depending on the restoration), and at least one way is wrong.

This problem highlights more basic problems
found within the Procolophonidae, some of which nest in the large reptile tree (still not updated)  with diadectids (Procolophon and kin, Fig. 1), with pareiasaurs (Sclerosaurus) and the rest nest as pre-Lepidosauriformes (Owenetta and kin). Conventionally procolophonids are considered parareptiles. Cisneros lists Nyctiphruretus as the outgroup and owenettids as basal taxa within the Procolophonidae. The large reptile tree replicated that outgroup only for the owenettids.

Scoloparia glyphanodon (Sues and Baird 1998) is currently represented by several specimens, three of which are figured, colorized and restored here (Figs. 1, 2). All three differ in size. Comparable skulls differ in morphology. This has been attributed to ontogeny.

Figure 1. Scoloparia restored here as a procolophonid together with other procolophonids.

Figure 1. Scoloparia restored here as a procolophonid together with other procolophonids. Click to enlarge. The large YPM mandible is a definite procolophonid. The small 82.1 specimen is a definite procolophonid. The holotype is the big question mark.

Clearly the referred specimens
(the dentary and the small 82.1 specimen) are procolophonids. Only seven blunt and rotated teeth in a mandible that tips down anteriorly along with gigantic orbits mark these taxa as procolophonids. They compare well with other procolorphonids.

Figure 2. Scoloparia restored as a pareiasaur close to Elginia along with several other pareiasaurs for comparison. Sclerosaurus typically nests as a procolophonid, but even with the removal of all skull traits, it nests as a small pareiasaur.

Figure 2. Scoloparia restored as a pareiasaur close to Elginia along with several other pareiasaurs for comparison. Sclerosaurus typically nests as a procolophonid, but even with the removal of all skull traits, it nests as a small pareiasaur. The new restoration reidentifies several bones. Note the convergence with the procolophonids in figure 1.

The problem is in the large holotype
The 83.1 specimen holotype of Scoloparia was preserved without a skull roof or palate, so the nasals, frontals and parietals are restored here.

Originally
the size and morphological differences were attributed to the juvenile status of the smaller specimen. H. Sues wrote to me, “Both specimens have the same peculiar ‘cheek’ teeth, which are unlike those of any other procolophonid.” 

I think what Dr. Sues means is shown below in figure 3. The teeth of the referred specimen attributed to Scoloparia have multiple cusps, unlike most procolophonids, but approaching the serrated morphology of pareiasaurs. The convergences are mounting!! And now you see why this is a quandary!

Figure 4. Teeth compared. Elginia, Scolaparia (referred), Leptopleuron and Diadectes.

Figure 3. Teeth compared. Elginia, Scolaparia (referred), Leptopleuron and Diadectes, a stem procolophonid. Oddly the very procolophonid Scoloparia (referred specimen) does have peculiar teeth for a procolophonid. They are serrated somewhat like those in the pareiasaur, Elginia.

I have asked to see images of the teeth for the Scoloparia holotype. No reply yet.

The mystery of the holotype 
Teeth were not illustrated by Sues and Baird for the holotype 83.1 specimen, who reported the mandible was articulated. The authors described two premaxillary, six maxillary and eight dentary teeth. That low number of teeth point toward a procolophonid ancestry. The upper anterior four teeth are described as incisiform with bluntly conical crowns that are rounded in cross section. The first premaxillary tooth is reported to be much larger than the other teeth. A large medial pmx tooth also points toward a procolophonid ancestry, as we’ve already seen with Colobomycter. In Elginia (Fig. 3)  the many small teeth are slightly constricted at the base and serrated at the crown as in other pareiasaurs.

Figure 4. Elginia colorized in four views. Note the rotation of the tabulars to the dorsal skull.

Figure 4. Elginia colorized in four views. Note the rotation of the tabulars to the dorsal skull. Click to enlarge. Note the many similarities to the pareiasaur-like restoration of Scoloparia. 

Nuchal osteoderms
Sues and Baird noted “nuchal (neck) osteoderms” preserved posterior to the skull in the 83.1 holotype of Scoloparia. Cisneros (2008) reports osteoderms have only been found in Sclerosaurus and Scoloparia. Since Sclerosaurus nests here as a pareiasaur, that means no other procolophonids have osteoderms. Hmmm.

Reversals in the skull roof of pareiasaurs 
In the large reptile tree pareiasaurus are sisters to turtles (all derived from Stephanospondhylus) and bolosaurids, all derived from Milleretta. In Stephanospondylus (Fig 5) a reversal takes place in which the postparietals (or are they tabulars?) rotate to the dorsal surface of the skull and the supratemporals develop small horns. These traits usually appear on pre-amniotes.

Figure 2. Stephanospondylus skull in two views. Note the rotation of the post parietals to the dorsal skull along with the transformation of the supratemporals into small horns.

Figure 5. Stephanospondylus skull in two views. Note the rotation of the post parietals to the dorsal skull along with the transformation of the supratemporals into small horns.

This dorsalization of the tabulars
becomes even more apparent in pareiasaurs (Fig. 2) and Elginia (Fig. 4). If the purported nuchals of Scoloparia are actually large supratemporals, tabulars, and opisthotics, then it’s a pareiasaur. If so, a foramen magnum is also present topped by a supraoccipital and two flanking exoccipitals. What a quandary!

Not quite enough to go on
I am working from a 2D line drawing here (from Sues and Baird 1998), not a photograph. So I await images of the teeth and any other data that may come down the pike. If new data ever comes in, I will let you know. For now, can’t tell if we’re dealing with autapomorphic nuchal osteoderms on a procolophonid or dorsalized tabulars and an occiput on a pareiasaur.

References
Cisneros JC 2008. Phylogenetic relationships of procolophonid parareptiles with remarks on their geological record. Journal of Systematic Palaeontology): 345–366.
Sues HD and Baird D 1998. Procolophonidae (Reptilia: Parareptilia) from the Upper Triassic Wolfville Formation of Nova Scotia, Canada. Journal of Vertebrate Paleontology 18:525-532.

The Procolophonidae

The Procolophonidae are odd, little-to-medium-sized, plant-eating reptiles that evolved from a sister to the basal diadectid, Orobates, survived the Permian extinction, but did not survive the Triassic. Here are a few of them (Fig. 1).

Figure 1. Click to enlarge. Procolophonids including Procolophon, Pentaedrusaurus, Colobomycter, Hypsognathus and Leptopleuron. Orobates is the outgroup taxon.

Figure 1. Click to enlarge. Procolophonids including Procolophon, Pentaedrusaurus, Colobomycter, Hypsognathus and Leptopleuron to scale. Orobates is the outgroup taxon. Note the large front teeth on Orobates and Colobomycter and the miniaturization that occurred between them. Arrows indicate more derived taxa. 

Yesterday we looked at the orbit in Hypsognathus. As procolophonids evolved, the orbits migrated to the top of the skull and elongated to accommodate the bulge of the temporal muscles. Procolophonids also evolved horns developed on the cheeks.

Most workers consider owenettids to be basal to procolophonids, but actually owenettids are basal to lepidosauriformes. Milleretta and diadectids like Orobates are basal to both Diadectes and Colobomycter + Procolophon. The large reptile tree tests more taxa giving each taxon more opportunities to nest more parsimoniously. This clade gave rise to no descendants.

Broom 1939 coined the term Procolophonoidea to include the Owenettidae and the Procolophonidae, but the two clades are not directly related.

Seeley 1888 coined the term Procolophonia to incude the above taxa plus the Pareiasauria, but the Pareiasauria are not related to Procolophon and kin despite the convergent development of expanded cheek bones.

Laurin & Gauthier 1996 define the Procolophonia cladistically as “The most recent common ancestor of pareiasaurs, procolophonids, and testudines (Chelonia), and all its descendants. The most recent common ancestor of these taxa, according to the large reptile tree, is Milleretta and all of its descendants include all living and extinct lizards, probably not what they intended.

deBraga & Reisz 1996 coined the term Ankyramorpha to include the above taxa plus Lanthanosuchus and Acleistorhinus, two taxa that are not even related to each other according to the large reptile tree. See what happens when you exclude pertinent sister taxa? We really need the large reptile tree to set the stage for smaller studies.

Romer 1964 coined the term Procolophonomorpha to include Nyctiphruretus and the above taxa.

Jalil and Janvier (2005) considered the clade  Procolophonomorpha = to Ankyramorpha.

References
deBraga M and Rieppel O. 1997. Reptile phylogeny and the interrelationships of turtles. Zoological Journal of the Linnean Society, 120: 281-354.
Jalil N-E and Janvier P 2005. Les pareiasaures (Amniota, Parareptilia) du Permien supérieur du Bassin d’Argana, Maroc. Geodiversitas, 27(1): 35-132.
Ruta M, Cisneros JC, Liebrecht T, Tsuji LA and Müller J 2011. Amniotes through major biological crises: Faunal turnover among Parareptiles and the end-Permian mass extinction. Palaeontology 54(5):1117.

When the orbit is on top of the skull… Hypsognathus

Earlier we looked at possible eyeball orientations for a basal tetrapod (amphibian) with orbits on top of its skull. The procolophonid, Hypsognathus (Fig. 1) is similar, only the orbit is so large that the eyeball shares the space with bulging temporal muscles.

Figure 1. Hypsognathus restored with an eyeball and jaw muscle filling the orbit.

Figure 1. Hypsognathus restored with an eyeball and jaw muscle filling the orbit. Rather than pointing skyward, the eyeballs probably were still oriented laterally, scanning the horizon, like crocs and frogs. Scale bar = 3 cm.

Even though the skull is quite odd, the eyeballs probably were oriented laterally, to scan the horizon, not the sky. When the orbit and jaw muscles fill the same space, as they also do in basal mammals, every time the jaw muscle moves it changes ever slightly the eyeball shape, either pushing it or relaxing it. Evidently this was not such a big problem for Hypsognathus or basal mammals, because Nature did not correct it. However, when you get to primates, the plate at the back of the primate orbit prevents this interaction because sharp eyesight is paramount for these tree dwellers with binocular vision.

Procolophonids descend from basal diadectomorphs, plant eaters that had to watch out for predators. They produced no descendants.

References
Gilmore CW 1928. New Fossil Reptile from the Triassic of New Jersey. Proceedings of the United States National Museum 73(7):1-8
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, Olsen PE, Scott DM and Spencer PS 2000. Cranial Osteology of Hypsognathus fenneri, a Latest Triassic Procolophonid Reptile from the Newark Supergroup of Eastern North America. Journal of Vertebrate Paleontology, 20(2):275-284.