Saurodektes: Filling in the missing parts

Saurodektes rogersorum
is a small owenettid lepidosauromorph (BP/1/6025, Early Induan, Early Triassic) originally named “Saurodectes” by Modesto et al. (2003), but that name was preoccupied by a fossil louse. The holotype of Saurodektes is known from a partial skull and anteriormost postcrania (Fig. 1).

Figure 1. Saurodektes (originally Saurodectes) by Modesto et al. 2003 (black/white). Missing parts in color based on phylogenetic bracketing.

Figure 1. Saurodektes (originally Saurodectes) by Modesto et al. 2003 (black/white). Missing parts in color based on phylogenetic bracketing.

The missing parts of the skull
can be restored using phylogenetic bracketing after phylogenetic analysis. In the large reptile tree Saurodektes nests at the base of the Owenetta clade, between the Nyctiphruretus and Barasaurus clades.

Procolophonomorpha?
No. All of these taxa nest far from Procolophon and kin, which nest with Diadectes and kin.

Lepidosauriformes?
Almost. These taxa were ancestral to Paliguana and the Lepidosauriformes, which gave rise to all living lizards and a host of extinct relatives, including pterosaurs.

Nascent upper temporal fenestra?
No. While the tiny space between the parietal and large supratemporal appears to be creating an upper temporal fenestra in Saurodektes, in lepidosauriformes the supratemporal is reduced and migrates to the back as it it is replaced by the squamosal, which comes to rim the upper temporal fenestra. Best to consider those cranial holes as damaged goods here in Saurodektes.

References
Modesto SP, Damiani RJ, Neveling J,Yates AM 2003. A new Triassic owenettid parareptile and the Mother of Mass Extinctions. Journal of Vertebrate Paleontology 23 (3): 715.

Restoring Pintosaurus

Pintosaurus (Piñeiro et al. 2004)
was described as a basal procolophonid close to Coletta and Owenetta on the basis of a incomplete skull (Fig. 1). Cisneros (2008) nested Pintosaurus similarly.

Figure 1. Pintosaurus restored from Piñeiro et al. 2004.

Figure 1. Pintosaurus (Late Permian) restored from Piñeiro et al. 2004.

Here (Fig. 1) just a little color and phylogenetic bracketing adds in the missing pieces from the Pintosaurus skull. The upper portions had weathered away, but are here restored.

Distinct from sister taxa,
Pintosaurus had only three teeth in the premaxilla, and it appeared to have a posterolateral process of the premaxilla. The large palatal fangs on the palatine are also unique to this genus. But when Contritosaurus (aka Phaanthosaurus, Fig. 2) is added it shares the trait of three large premaxillary teeth, but the naris is anterior on a transverse premaxilla. This clade has an unusual narial fossa (depression).

Figure 2. Contritosaurus (aka Phaanthosaurus sinus), a sister to Pintosaurus. Note the narial fossa and palatine teeth.

Figure 2. Contritosaurus (aka Phaanthosaurus sinus), a sister to Pintosaurus. Note the narial fossa and palatine teeth.

Like their sister, Coletta (Fig. 3, Gow 2000, Modesto, Damiani and Sues 2002, Early Triassic, GHG 228), these genera likely had upper temporal fenestra. They nest as derived owenettids and stem lepidosauriformes.

Figure 3. Coletta nests with Pintosaurus and Contritosaurus in the large reptile tree. Note the small upper temporal fenestrae, marking this taxon as a stem owenettid.

Figure 3. Coletta nests with Pintosaurus and Contritosaurus in the large reptile tree. Note the small upper temporal fenestrae, marking this taxon as a derived owenettid and a stem lepidosauriform.

These are sisters to the ancestors of the gliding lepidosauriforms, and all lepidosaurs, including Sphenodon, pterosaurs, lizards and snakes.

References
Cisneros JC 2008. “Phylogenetic relationships of procolophonid parareptiles with remarks on their geological record”Journal of Systematic Palaeontology 6:345–366.
Cudinov PK and Vjushkov BP 1956. New data on small cotylosaurus from the Permian and Triassic of the USSR. Doklady Akademii Nauk SSSR 108:547-550.
Gow CE 2000. A new procolophonid (Parareptilia) from the Lystrosaurus Assemblage Zone, Beaufort Group, South Africa. Palaeontologia Africana 36:21–23.
Ivakhnenko MF 1974. New data on Early Triassic procolophonids of the USSR. Paleontological Journal 8:346-351.
Modesto SP, Damiana RJ and Sues H-D 2002. A reappraisal of Coletta seca, a basal procolophonid reptile from the lower Triassic of South Africa. Palaentology 45(5):883-895.
Piñeiro G, Rojas A and Ubilla M 2004. A new procolophonid (Reptilia, Parareptilia) from the Upper Permian of Uruguay. Journal of Vertebrate Paleontology 24:814-821.

Procolophonids and look-alikes, like Sauropareion

A recent endaaper
by MacDougall et al. (2013) reported on the post-crania of the Early Triassic reptile, Sauropareion (Fig. 1). The description was excellent.

Unfortunately
they labeled it a procolophonid and a parareptile. That was by tradition, for the most part.

Figure 1. Sauropareion in situ from MacDougall et al 2013.

Figure 1. Sauropareion in situ from MacDougall et al 2013.

A phylogenetic analysis was performed by them (Fig. 2) to nest Sauropareion. While their test included several taxa I have not tested (everyone needs a new project for the new year), the large reptile tree found a much different nesting (color notes in Fig 2), at the base of the owenettids, and, by extension, at the base of the Lepidosauriformes, close to Paliguana.

Figure 2. Nesting Sauropareion. Here it nests correctly with owenettids, but the inclusion of pareiasaurids like Sclerosaurus, and diadectids, like Procolophon, is unwarranted, according to the results of the large reptile tree. Also, several taxa that should have been included were not, given the gamut of the inclusion set. Several basal lepidosauriformes should also have been included given their proximity in the large reptile tree. The lack of resolution may be due to the inclusion of unrelated taxa or the incompleteness of the included taxa.

Figure 2. Nesting Sauropareion. Here it nests correctly with owenettids, but the inclusion of pareiasaurids like Sclerosaurus, and diadectids, like Procolophon, is unwarranted, according to the results of the large reptile tree. Also, several taxa that should have been included were not, given the gamut of the inclusion set. Several basal lepidosauriformes should also have been included given their proximity in the large reptile tree. The lack of resolution may be due to the inclusion of unrelated taxa or the incompleteness of the included taxa.

We need to take a large look at procolphonids
Unfortunately Procolophonidae has become a wastebasket taxon for any small reptile with short toes and a large orbit. A large gamut phylogenetic analysis is needed to correctly nest the many taxa that have been attributed to it — and to correctly nest the Procolophonidae itself.

The large reptile tree nests Procolophon, Hypsognathus and Pentaedrusaurus with Diadectes, a taxon typically excluded in prior analyses.

MacDougall et al. include Sclerosaurus, but that taxon nests with pareiasaurs in the large reptile tree.

Phonodus nests with bolosaurs in the large reptile tree, not far from procolophonids and diadectids.

Assumptions and traditions
need to be tested in a larger gamut analysis. If I have any influence over the study of paleontology, this is what I want, a large gamut analysis by someone else to test the large reptile tree.

References
MacDougall MJ, Modesto SP and Botha-Brink J 2013. The postcranial skeleton of the Early Triassic parareptile Sauropareion anoplus, with a discussion of possible life history. Acta Palaentologica Polonica 58(4):737-749.

Santaisaurus – A rare paliguanid (basal lepidosauriform)

Santaisaurus yuani (Koh 1940) doesn’t have much presence out there. It’s a small crushed fossil from the Early Triassic of China. Li (1989) nested it with Paliguana at the base of the lepidosauriformes. The large reptile tree agrees with this nesting.

Figure 1. Santaisaurus yuani, a rarely studied owenettid/basal lepidsoauriform originally considered a procolophonid.

Figure 1. Click to enlarge. Santaisaurus yuani, a rarely studied owenettid/basal lepidosauriform originally considered a procolophonid. At right, largely in situ and crushed, original tracing of tracing by Koh (1940). That tracing leaves open the possibility of upper temporal fenestra, a trait scored as (?) in the large reptile tree. At left, reconstructed.

Lucas (2002) considered Santaisaurus a possible eolacertilian and notes it is now represented by three incomplete skeletons. Lucas lists traits that agree with a procolophonid assignment, but notes tooth differences.

Palaeocritti nests Santaisaurus tentatively within the Procolophonidae. However, Santiasaurus has small, subpleurodont teeth, not the the acrodont teth of procolophonids. In this way it presages the pleurodont teeth of sphenodontia, which are derived and closely related through Gephyrosaurus. Fairly large limbs like these (Fig. 1) are also found in the related Palaegama and Saurosternon, two likely arboreal reptiles.

There’s a larger issue
As reported earlier, the traditional Procolophonoidea appears to have an upside-down tree with Owenetta primitive and Procolophon derived, just the opposite of that found in the large reptile tree where Procolophon nests with the primitive Diadectes while the essentially unrelated Owenetta nests with derived lepidosauriformes, like Santaisaurus and Paliguana. Several non-procolophonids nest inbetween.

References
Koh  T-P 1940. Santaisaurus yuani gen. et sp. nov., ein neues Reptil aus der unteren Trias von China. Bulletin of the Geological Society of China 20(1):73-92.
Li J-L1989. A New Genus of Procolophonidae from Lower Triassic of Shaanxi, China. Vertebrata PalAsiatica 27(4):248-267.
Lucas S 2002. Chinese Fossil Vertebrates. Columbia University Press.

Procolophonid phylogeny – problems and solutions

Cisneros 2008 reviewed the “procolophonids” as traditionally assumed (Fig. 1) and created a  focused phylogenetic family tree with Nyctiphruretus and Owenettids at the base and Procolophon, Hypsognathus and Sclerosaurus as derived taxa (Fig.1). Unfortunately, this topology was not replicated in the large reptile tree. Moreover, the Cisnernos tree appears to be upside down.*

Figure 1. The Procolophonid family tree according to Cisneros 2008.

Figure 1. The traditional procolophonid family tree according to Cisneros 2008. Highlighted taxa are found scattered in the large reptile tree (figure 2). Nyctiphruretus is the outgroup. Owenettidae is the secondary outgroup. The large reptile tree found Orobates to be the outgroup for Procolophon and kin (Fig. 2). Nowhere here are any diadectids, the sister group to Procolophon and kin in the large reptile tree. 

Figure 2. A segment of the large reptile tree with a gamut more or less equal to the Cisneros tree demonstrating the large number of excluded intervening taxa discovered by increasing the inclusion set.

Figure 2. A segment of the large reptile tree with a gamut more or less equal to the Cisneros 2008 tree demonstrating the large number of excluded intervening taxa discovered by increasing the inclusion set. Highlighted taxa are found in the Cisneros 2008 tree (figure 1).

The large reptile tree
found a different topology (Fig. 2) with Hypsognathus and Procolophon at the base derived from a sister to Orobates. Sclerosaurus nested with pareiasaurs. Nyctiphruretus and owenettids nested as derived taxa basal to lepidosaurs (outgroup to Paliguana). Clades were widely separated from one another by numerous taxa.

Background
Cisneros 2008 reviewed the prior literature on the subject, noting with regularity that owenettids were previously not associated with procolphonids and otherwise often are found to each be monophyletic taxa. That all changed when Reisz and Laurin (1991) considered Owenetta to be a procolophonid. DeBraga and Rieppel (1997) found an Owenettidae-Procolophonidae clade. DeBraga (2003) placed Sclerosaurus within the Procolophonidae.

The problem
with Cisneros 2008 and the other prior papers listed above appears to be a reliance on small traditional inclusion sets without basing them on a verified and valid larger gamut study, like the large reptile tree (Fig. 2). Such a large study establishes broader relationships. Then more focused studies, like Cisneros 2008, can proceed with greater confidence and fewer taxon inclusion/exclusion errors.

This is the reason to have a large gamut study of the reptile family tree — to avoid such assumptions based on tradition, not testing. Larger trees also establish outgroups better.

Real procolophonids
Are restricted to Hypsognathus and Procolophon (from the large reptile tree), plus the procolophonid cousins listed in figure 1. Sclerosaurus, nyctiphruretids and owenettids belong to small non-procolophonid clades on the new Lepidosauromorpha branch leading to lepidosaurs, further to the right in the tree, far from the true procolophonids.

References
Cisneros JC 2008. Phylogenetic relationships of procolophonid parareptiles with remarks on their geological record. Journal of Systematic Palaeontology 6(3): 345-366.
deBraga M 2003. The postcranial skeleton, phylogenetic position, and probable life style of the Early Triassic reptile Procolophon trigonicepsCanadian Journal of Earth Sciences 40: 527–556.
DeBraga M and Rieppel O 1997. Reptile phylogeny and the interrelationships of turtles. Zoological Journal of the Linnean Society 120: 281–354.
Reisz RR and Laurin M 1991. Owenetta and the origin of turtles. Nature 349: 324–326.

* We’ve seen such trees before here, with phylogenetic relationships perfectly ordered but upside-down.