Taxon exclusion mars 2020 study of evolutionary innovation in reptiles

Simões et al. 2020 present
their vision of phenotypic diversity in reptiles (Fig. 1).

Unfortunately they do so
without knowing the last common ancestor of reptiles (Silvanerpeton) and the basal dichotomy of reptiles, both of which lead to a complete misunderstanding of the main branches in the phylogeny of reptiles. That lack of taxa led to a shuffling of the two major clades in the LRT, the new Archosauromorpha and the new Lepidosauromorpha.

For instance,
Simões et al. have no idea that ‘Diapsida’ is an invalid clade, unless restricted to only Archosauromorpha. Lepidosauriformes are the lepidosaur branch of the former ‘Diapsida’. Their figure 3 cladogram of the Lepidosauria omits Tritosauria and flips the order, nesting Iguania as a derived clade, rather than the basal clade it is in the LRT.

The large reptile tree (LRT) with 1746+ taxa remains the overlooked standard by which all smaller studies can be measured for no other reason that it includes more taxa. In the LRT phylogenetic miniaturization occurred at the genesis of many evolutionary novelties. This factor was overlooked in Simões et al. 2020 due to taxon exclusion.

Figure 1. Cladogram from Simoes et al. 2020 suffering from so much taxon exclusion that Archosauromorpha are shuffled within Lepidosauromorpha.

Figure 1. Cladogram from Simoes et al. 2020 suffering from so much taxon exclusion that Archosauromorpha are shuffled within Lepidosauromorpha.

The Simões et al. plan:
“Here, we explore megaevolutionary dynamics on phenotypic and molecular evolution during two fundamental periods of reptile evolution: (i) the origin and early diversification of the major lineages of diapsid reptiles (lizards, snakes, tuataras, turtles, archosaurs, marine reptiles, among others) during the Permian and Triassic periods, and (ii) the origin and evolution of lepidosaurs (lizards, snakes and tuataras) from the Jurassic to the present.”

Lacking pertinent taxa, Simões et al. mistakenly place turtles in diapsids and do not include pterosaurs, rhynchosaurs and tanystropheids in lepidosaurs.

Simões et al. conclude:
“Collectively, our findings suggest a considerably more complex scenario concerning the evolution of reptiles in deep time than previously thought.”

Without a proper phylogenetic context
anything this study presents is suspect or invalid from the get-go. Bring back your math, your charts, your statistics after you have a wide gamut, comprehensive cladogram with proper outgroup taxa, a working last common ancestor and valid branching thereafter, as in the LRT.

Colleagues:
add more taxa. That will expand, clarify and validate your cladograms.


References
Simões TR, Vernygora O, Caldwell MW and Pierce SE 2020. Megaevolutionary dynamics and the timing of evolutionary innovation in reptiles. Nature 11:3322  https://doi.org/10.1038/s41467-020-17190-9 http://www.nature.com/naturecommunications

Simões et al. 2020 fail to understand ‘diapsids’ due to taxon exclusion

Simões et al. 2020 brings us their study
on the rates of evolutionary change in reptiles with a diapsid skull architecture.

From the abstract:
“The origin of phenotypic diversity among higher clades is one of the most fundamental topics in evolutionary biology. However, due to methodological challenges, few studies have assessed rates of evolution and phenotypic disparity across broad scales of time to understand the evolutionary dynamics behind the origin and early evolution of new clades. Here, we provide a total-evidence dating approach to this problem in diapsid reptiles. We find major chronological gaps between periods of high evolutionary rates (phenotypic and molecular) and expansion in phenotypic disparity in reptile evolution. Importantly, many instances of accelerated phenotypic evolution are detected at the origin of major clades and body plans, but not concurrent with previously proposed periods of adaptive radiation. Furthermore, strongly heterogenic rates of evolution mark the acquisition of similarly adapted functional types, and the origin of snakes is marked by the highest rates of phenotypic evolution in diapsid history.”

This study suffers from taxon exclusion
By adding taxa the first dichotomy of the Reptilia (Amniota is a junior synonym) splits taxa closer to lepidosaurs (Lepidosauromorpha) from those closer to archosaurs (Archosauromorpha, including Synapsida). Thus members of the traditional clade ‘Diapsida’ are convergent. Other than through the last common ancestor of all Reptiles, Silvanerpeton in the Viséan, archosaurs are not related to lepidosaurs. The present paper by Simões et al. 2020 fails to recover this topology due to taxon exclusion. Without a valid phylogenetic context, the results are likewise hobbled.


References
Simões TR, Vernygora O, Caldwell MW and Pierce SE 2020. Megaevolutionary dynamics and the timing of evolutionary innovation in reptiles. Nature Communications 11: 3322.

http://reptileevolution.com/reptile-tree.htm

Here’s a project ripe for a PhD dissertation: Youngina and kin

Summary for those in a hurry:
Specimens nesting at the base of the marine and terrestrial younginiforms need a good review, as in a doctoral dissertation. Many of the specimens below have not been described and the collection has not been tested in a phylogenetic analysis, except here in the LRT. And let’s not forget headless Galesphyris (Fig. 4), the last common ancestor of this monophyletic clade of (at present) wastebasket “young-” younginids (Youngina, Youngolepis and Youngoides) needs to be part of the picture. The Late Carboniferous diapsid, Spinoaequalis (Fig. 2), is the outgroup taxon in the LRT.

A new ‘Youngina’ specimen came to my attention
(Fig. 1) published in Sues 2019. Unfortunately no museum number was provided. Pending acquisition of that number, the new specimen was added to the large reptile tree (LRT, 1694+ taxa) just to see where the new one would nest among the many Youngina, Youngoides and Youngolepis specimens (Figs. 2, 3) already in the LRT. Scale bars indicate it’s a big one.

Figure 1. Unidentified specimen attributed by Sues 2019 to Youngina capensis. Here it nests with the much smaller BPI 375 specimen basal to protosaurs.

Figure 1. Unidentified specimen attributed by Sues 2019 to Youngina capensis. Here it nests to scale with the much smaller BPI 375 specimen basal to protosaurs, like the AMNH 9520 specimen assigned to Prolacerta.

Relatively few workers
have published on the Youngina, Younginoides and Youngolepis specimens. That is unexpected considering the key position in the LRT of these largely ignored taxa at the bases of several major clades.

Figure 1. Terrestrial Yonginiformes + Galesphyrus representing the marine clade, all to scale except the toned area containing protorosaurs, which have their own scale.

Figure 2. Terrestrial Yonginiformes + Galesphyrus representing the marine clade, all to scale except the toned area containing protorosaurs, which have their own scale.

One traditional Youngina specimen, 
short-legged BPI 3859, does not nest with the terrestrial taxa in the LRT, despite the many similarities.

Figure 3. The odd one out, the BPI 3859 specimen assigned to Youngina does not nest with the others, but with marine taxa.

Figure 3. The odd one out, the BPI 3859 specimen assigned to Youngina does not nest with the others, but with marine taxa.

However,
if headless Galesphyris turns out to be a junior synonym of Youngina, then the genus would be monophyletic across tested taxa. Let’s leave open that possibility. Otherwise, let’s rename them all appropriately.

Figure 4. If Galesphyrus was Youngina, the genus would be monophyletic.

Figure 4. If Galesphyrus was Youngina, the genus would be monophyletic.

At nine cm in length, the skull of the new specimen
is the largest skull assigned to the genus Youngina. Like the smaller BPI 375 specimen, it nests basal to protorosaurs in the LRT. Other specimens nest basal to Archosauriformes. As noted above, the BPI 3859 specimen nests basal to Claudiosaurus in the LRT along with other marine younginiformes, including plesiosaurs, mesosaurs and ichthyosaurs.


References
Broom R 1914. A new thecodont reptile. Proceedings of the Zoological Society of London, 1914:1072-1077.
Broom R and Robinson JT 1948. Some new fossil reptiles from the Karroo beds of South Africa: Proceedings of the Zoological Society of London, series B, v. 118, p. 392-407.
Gardner NM, Holliday CM and O’Keefe FR 2010. The braincase of Youngina capensis (Reptilia, Diapsida): New insights from high-resolution CT scanning of the holotype. Paleonotologica Electronica 13(3).
Gow CE 1975. The morphology and relationships of Youngina capensis Broom and Prolacerta broomi Parrington. Palaeontologia Africana, 18:89-131.
Olson EC 1936. Notes on the skull of Youngina capensis Broom. Journal of Geology, 44 (4): 523-533.
Olson EC and Broom R 1937. New genera and species of tetrapods from the Karroo Beds of South Africa. Journal of Paleontology 11(7):613-619.
Smith, RMH and Evans SE 1996. New material of Youngina: evidence of juvenile aggregation in Permian diapsid reptiles. Palaeontology, 39 (2):289–303.
Sues HD 2019. The Rise of Reptiles: 320 Million Years of Evolution.
Johns Hopkins University Press, Baltimore. xiii + 385 p.; ill.; index.
ISBN: 9781421428673 (hc); 9781421428680 (eb).

wiki/Youngina

The affinities of ‘Parareptilia’ and ‘Varanopidae’: Ford and Benson 2020

Readers will know the knives are out for this one
by Ford and Benson 2020 since the large reptile tree (LRT, 1625+ taxa) finds the Parareptilia is polyphyletic and the Varanopidae (1940) is a junior synonym for Synapsida (1903). And yes, Ford and Benson’s cladogram (Fig. 1) suffers from (altogether now): taxon exclusion. The Ford and Benson paper, like many before it, keeps perpetuating the myth of the Parareptilia and other traditional clades.

Figure 1. Cladogram by Ford and Benson 2020, with orange overlay showing taxa in the Archosauromorpha in the LRT. Massive taxon exclusion is the problem with the Ford and Benson tree.

Figure 1. Cladogram by Ford and Benson 2020, with orange overlay showing taxa in the Archosauromorpha in the LRT. Massive taxon exclusion is the problem with the Ford and Benson tree.

From the abstract:
“Amniotes include mammals, reptiles and birds, representing 75% of extant vertebrate species on land. They originated around 318 million years ago in the early Late Carboniferous and their early fossil record is central to understanding the expansion of vertebrates in terrestrial ecosystems.

By contrast, in the LRT the last common ancestor of all amniotes (= reptiles) is Silvanerpeton from the Viséan (Early Carbonferous, 335mya, not listed in Fig. 1) with a likely genesis earlier since the Viséan includes several other  amphibian-like reptiles, also not listed. Ford and Benson need to dip much deeper into the basal Tetrapoda to figure out which taxon is the last common ancestor of the Amniota and which taxa precede it. They make the mistake of considering Tseajaia and Limnoscelis pre-amniotes.The LRT nests them both deep within Amniota / Reptilia.

“We present a phylogenetic hypothesis that challenges the widely accepted consensus about early amniote evolution, based on parsimony analysis and Bayesian inference of a new morphological dataset.”

That would be great, so long as they include pertinent taxa, which they do not.

“We find a reduced membership of the mammalian stem lineage, which excludes varanopids.”

That’s odd because when you add pertinent taxa, the LRT finds an increased membership in the diapsid/mammal stem lineage, the new Archosauromorpha.

“This implies that evolutionary turnover of the mammalian stem lineage during the Early–Middle Permian transition (273 million years ago) was more abrupt than has previously been recognized.”

No one can make valid implications from the Ford and Benson cladogram. It is largely incomplete.

“We also find that Parareptilia are nested within Diapsida.”

This is only possible due to massive taxon exclusion. Ford and Benson omit many taxa that would change the topology of their tree. The Parareptilia include a diverse and polyphyletic assembly of taxa according to the LRT. Ford and Benson are not aware that Lepidosauria are no longer members of the archosauromorph Diapsida.

“This suggests that temporal fenestration, a key structural innovation with important functional implications, evolved fewer times than generally thought, but showed highly variable morphology among early reptiles after its initial origin.”

Just the opposite. In the LRT fenestration evolved MORE times than generally thought.

“Our phylogeny also addresses controversies over the affinities of mesosaurids, the earliest known aquatic amniotes, which we recover as early diverging parareptiles.”

That can only happen with massive taxon exclusion. We’ve known for several years that mesosaurs nest as derived pachypleurosaurs close to thalattosaurs and ichthyosaurs in the LRT. Those pertinent taxa are omitted in Ford and Benson’s paper.

From the introduction:
“The current paradigm of early amniote evolution was established in the late twentieth century. It includes a deep crown group dichotomy between Synapsida (total group mammals) and Reptilia (total group reptiles, including birds), followed by an early divergence of Parareptilia from all other reptiles (Eureptilia).”

Add taxa and the first dichotomy separates the new Archosauromorpha from the new Lepidosauromorpha. This has been online since July 2011 and represents the current paradigm. Ford and Benson are digging into old myths and traditions.

“Furthermore, both molecular and morphological studies have recovered turtles, which lack fenestrae, as diapsids.”

Since molecular studies do not replicate trait studies in deep time molecular studies must be wrong (probably due to epigenetics) and do not employ fossil taxa. So forget genomics in paleontology. Genomics delivers false positives.

“Our analysis includes 66 early fossil members of the amniote crown group, and four crownward members of the amniote stem group, giving a total of 70 operational taxonomic units.” 

By contrast the LRT includes 1625+ taxa not biased by prior studies, including dozens of basal vertebrates and basal tetrapods.

“The goal of our study is to examine the deep divergences of the amniote crown group.” 

If so, then Ford and Benson need to add dozens to hundreds of more taxa to their incomplete study. A suggested list is found here.

“We excluded recumbirostrans from our analysis. Recumbirostrans have generally been assigned to non-amniote microsaurs, but were recently recovered as early crown group amniotes.”

By contrast the LRT includes seven taxa listed by Wikipedia/Recumbirostra. We learned earlier that previous workers have deleted taxa that otherwise deliver unwanted results. Not sure what is happening in the Ford and Benson paper after their omission of this clade. Those seven recumbirostran taxa nest outside the Reptilia /Amniota in the LRT.

From the Results:
“All our analyses recover parareptiles and neodiapsids as a monophyletic group within Diapsida.”

These are false positive results due to taxon exclusion as shown here.

From the Discussion:
“The sister relationship between parareptiles and neodiapsids, and their relationship to Varanopidae, implies a single origin of temporal fenestration before the common ancestor of these clades.” 

These are false positive results due to taxon exclusion as shown here. We’ve known the clade Diapsida is polyphyletic since July 2011 with a last common ancestor in Early Carboniferous amphibian-like reptiles.

Happy holidays, dear readers. 


References
Ford DP and Benson RBJ 2020. The phylogeny of early amniotes and the affinities of Parareptilia and Varanopidae. Nature ecology & evolution 4:57–65. SuppData

Modesto SP 2020. Rooting about reptile relationships. Nature Ecology & Evolution 4:10–11.

 

New ‘Mesenosaurus’ closer to other taxa in the LRT

Maho, Gee and Reisz 2019
introduce us to a new Early Permian skull-only specimens (OMNH 73208, OMNH 73209 and OMNH 73500; Figs. 1, 2) they attribute to a new species of an old genus, Mesenosaurus efremovi

Figure 1. ?Mesenosaurus efremovi, left and right sides from Maho et al. 2019. Colors added using DGS techniques.

Figure 1. ?Mesenosaurus efremovi, left and right sides from Maho et al. 2019. Colors added using DGS techniques. Note the antorbital fossa without a fenestra.

The original art in Maho et al. 2019
(Fig. 1) was used to create this reconstruction (Fig. 2) using DGS techniques, using the best bones from the left and right to make this reconstruction. There are no surprises here.

Figure 2. ?Mesenosaurus efremovi reconstructed using DGS techniques.

Figure 2. ?Mesenosaurus efremovi reconstructed using DGS techniques. See figure 1.

After testing OMNH 73209
(Figs. 1, 2) in the large reptile tree (LRT, 1592 taxa, subset Fig. 4) this specimen nests a node away from three other Mesenosaurus specimens. So, distinct from Maho et al. 2019 (Fig 3), this specimen is not congeneric with other Mesenosaurus in the LRT (Fig. 4).

Figure 3. From Maho et al. 2019, their cladogram of Mesenosaurus relationships.

Figure 3. From Maho et al. 2019, their cladogram of Mesenosaurus relationships.

Further complicating matters,
Maho et al. contend that Mesenosaurus is a varanopid (Fig. 3). This is an outmoded traditional hypothesis invalidated in 2014 by the LRT. Mesenosaurus and kin are Protodiapsids, nesting between the basalmost synapsid, Vaughnictis and archosauromorphs with a diapsid skull architecture, labeled Diapsida in the LRT.

Figure 4. Subset of the LRT focusing on the clade Protodiapsida nesting between basalmost synapsids and archosauromorph diapsids.

Figure 4. Subset of the LRT focusing on the clade Protodiapsida nesting between basalmost synapsids and archosauromorph diapsids.

As we learned earlier in 2011
lepidosauriformes also developed a diapsid skull architecture by convergence, here labeled Lepidosauriformes. That news has not reached the three authors, Maho, Gee and Reisz, nor have they tested a sufficient number of pertinent taxa to recover that basal dichotomy, known for the last eight years.

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 5. 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.

According to the LRT
the various Mesenosaurus specimens (Fig. 5) demonstrate a wider variety of skull shapes than do many congeneric taxa.

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 6. 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.

Varanopids have a smaller clade membership
than the authors suppose when more taxa are tested. All they have to do is add taxa to see their varanopid clade become a dichotomy (Fig. 6) leading to mammals on one line and dinosaurs and giant sea reptiles on the other. All this was overlooked by the PhDs.


References
Maho S, Gee BM, Reisz RR 2019. A new varanopid synapsid from the early Permian of Oklahoma and the evolutionary stasis in this clade. R. Soc. open sci. 6: 191297. http://dx.doi.org/10.1098/rsos.191297

https://pterosaurheresies.wordpress.com/2014/03/03/basal-diapsida-and-proto-diapsida/

Early Permian Cabarzia enters the LRT on two legs

Spindler, Werneberg and Schneider 2019
bring us news of a new headless, but otherwise complete skeleton from the Early Permian of Germany. The authors considered Cabarzia trostheidei (Figs. 1, 2, 5; NML-G2017/001) a close match to the Middle Permian protodiapsid Mesenosaurus (Fig. 2) from the Middle Permian of Russia and the oldest evidence for bipedal locomotion, 15 million years earlier than Eudibamus.

Figure 1. Cabarzia in situ and tracing distorted to fit the photo from Spindler, et al. 2019. Inserts show manus and pes with DGS colors and reconstructions. Scale bar = 5 cm.

Figure 1. Cabarzia in situ and tracing distorted to match the photo from Spindler, et al. 2019. Inserts show manus and pes with DGS colors and reconstructions. Scale bar = 5 cm. Pelvis enlarged in figure 4.

In slight contrast
the large reptile tree (LRT, 1385 taxa; subset Fig. 4) nests Cabarzia on the synapsid side of the Synapsida-Protodiapsida split within the new Archosauromorpha. Skull-less Cabarzia nests with the synapsids, Apsisaurus and Aerosaurus, also from the Early Permian. This is only a node or two away from Mesenosaurus.

In an earlier Spindler et al. 2016 phylogenetic analysis,
the last outgroup to the Synapsida-Protodiapsida split, Vaughnictis nested with the new Lepidosauromorpha caseid, Oedaleops (Fig. 3) far from the synapsids, but close to Feeserpeton and other taxa with a lateral temporal opening not related to synapsids. That error and the mistaken monophyly of the clade Varanopidae, are common to in all current paleontological books. Both are due to taxon exclusion at the base of the Reptilia (see below) and the lack of diapsid taxa in synapsid studies and vice versa.

Figure 2. Two specimens attributed to Mesenosaurus compared to scale with Cabarzia. Scale bar = 5cm.

Figure 2. Two specimens attributed to Mesenosaurus compared to scale with Cabarzia. Scale bar = 5cm.

Spindler et al. 2016 (the Ascendonanus paper)
presented a phylogenetic analysis that included Vaughnictis, which nested with the Lepidosauromorph caseid, Oedaleops, (Fig. 3) without providing enough taxa to recover a basal Lepidosauromorpha-Archosauromorpha split recovered by the LRT that separates caseids from synapsids and nests them with other bulky herbivores with a lateral temporal fenestra, like Eunotosaurus. Cabarzia was then known as the Cabarz specimen, then considered a member of the Varanopidae (Fg. 3).

FIgure 3. Spindler et al. 2016 cladogram suffering from massive taxon exclusion.

FIgure 3. Spindler et al. 2016 cladogram suffering from massive taxon exclusion. The red panel highlights taxa that nest within the new Lepidosauromorpha in the LRT. The dark gray panel highlands various actual and putative varanopids nesting paraphyletically. In the LRT they nest together. Note the proximity of the Cabarz specimen (Cabarzia) to Elliotsmithia, but some distance from Apsisaurus, Aerosaurus, Varanops and and Varanodon.

The LRT
(subset Fig. 4) does not suffer from taxon exclusion. At least, so far… Rather this wide gamut study illuminates previously unrecognized splits, like those within the traditional Varanopidae that produced the Protodiapsida.

Figure 4. Subset of the LRT focusing on basal Archosauromorpha including Vaughnictis and Cabarzia nesting at the base of the Protodiapsid-Synapsid split. Note all the large varanopids nest together here in the Synapsida, separate from small varanopids in the Protodiapsida.

Figure 4. Subset of the LRT focusing on basal Archosauromorpha including Cabarzia nesting at the base of the -Synapsida. Note all the large varanopids nest together here in the Synapsida, separate from small varanopids in the Protodiapsida.

Bipedal locomotion
Spindler et al. report, “Although the proportions of the entire postcranium of Cabarzia roughly resemble those of Eudibamus, these genera can easily be distinguished based on their vertebrae.” 

Citing Berman et al. 2000b and Sumida et al. 2013,
Spindler et al. list the adaptations of functional bipedalism. (my notes added)

  1. short neck (but Chlamydosaurus has a long neck)
  2. long hindlimbs
  3. short forelimbs
  4. short and slender trunk
  5. and a long robust tail (but Chlamydosaurus has a long attenuated tai)
  6. a rearward shift of the center of body mass

Spindler et al. 2018 note: “Decreased asymmetry of the hindlimb is seen in basal varanopids and mesenosaurines. Eudibamus has remarkably narrow caudal vertebrae; this may indicate that it evolved active bipedalism, facilitating slow bipedal locomotion.” We talked earlier here about the basal diapsid with a long neck and super slender tail, Eudibamus and its putative bipedal abilities. Spindler et al. do not cite the most active scientist currently working with bipedal lizards, Bruce Jayne and his video of lizards on treadmills.

FIgure 4. Pelvis of Cabarzia colored with DGS. Note the offset femoral head perforating the pelvis, the anterior process of the illiim and the four sacral vertebrae, all pointing to bipedal locomotion. Some of this was overlooked by Spindler et al.

FIgure 4. Pelvis of Cabarzia colored with DGS. Note the offset right femoral head perforating the pelvis, the anterior processes of the illi a and the four sacral vertebrae, all pointing to bipedal locomotion. Some of this was overlooked by Spindler et al. The left femur is too long due to the split. The pink linear bones are probably displaced gastralia.

The traditional touchstones of bipedal locomotion in lizards
(e.g. Chlamydosaurus kingii) are also present in Cabarzia. These include (according to Shine and Lambeck 1978, Snyder 1954; my notes added in bold):

  1. Bipedal reptiles are generally small, having experienced phylogenetic miniaturization –  outgroup taxa, Protorothyris and Vaughnictis, are not larger than Cabarzia.
  2. Bipeds are terrestrial and/or arboreal – present in most tetrapods
  3. Longer hind limbs than forelimbs – present in many tetrapods
  4. Anterior process of the illiim, no matter how small – present in Cabarzia 
  5. Typically stronger or more sacral connections to the ilium – present in Cabarzia 
  6. Typically a long neck and short torso  unknown in Cabarzia 

In Cabarzia we also find

  1. perforated acetabulum
  2. elongate and offset cylindrical femoral head

Overlooked by Spindler et al.:
Cabarzia provides a more complete look at the post-crania of basalmost synapsids, which include humans. No one has ever considered the possibility that bipedal locomotion in the Early Permian was part of that story. It is also common knowledge that more derived taxa in the lineage of synapsids, therapsids and mammals retained  quadrupedal locomotion, an imperforated acetabulum and only two sacrals. So bipedalism was a dead-end for Cabarzia, producing no known ancestors.

Figure 5. Cabarzia compared to Vaughnictis and Apsisaurus to scale. Finger 1 and other phalanges were identified in published photos of this specimen (Fig. 1) using DGS tracing and reconstruction methods.

Figure 5. Cabarzia compared to Vaughnictis and Apsisaurus to scale. Finger 1 and other phalanges were identified in published photos of this specimen (Fig. 1) using DGS tracing and reconstruction methods.

Despite the similar and coeval red bed matrices
of Aerosaurus, ApsisaurusVaughnictis and Cabarzia, the former three come from the western USA (Colorado) while Cabarzia comes from central Germany. Back then they were closer to one another, not separated by an Atlantic Ocean (Fig. 6).

Figure 6. Early Permian Earth, prior to the separation of Europe from North America.

Figure 6. Early Permian Earth, prior to the separation of Europe from North America.

References
Shine R and Lambeck R 1989.Ecology of Frillneck Lizards, Chlamydosaurus kingii (Agamidae), in Tropical Australia. Aust. Wildl. res. Vol. 16: 491-500.
Snyder RC 1954.
 The anatomy and function of the pelvic girdle and hind limb in lizard locomotion. American Journal of Anatomy 95:1-46.
Spindler F, Werneberg R and Schneider JW 2019. A new mesenosaurine from the lower Permian of Germany and the postcrania of Mesenosaurus: implications for early amniote comparative osteology. PalZ Paläontologische Gesellschaft

 

SVP 2018: The evolution of varanopids

Reisz 2018 reports,
“Varanopidae is a clade of small to medium sized carnivorous synapsids whose fossil
record spans the Late Pennsylvanian to late Permian, one of the longest known temporal
ranges of any Paleozoic eupelycosaur clade. It has also been recently suggested that this clade may not be part of Synapsida, but may instead nest within Diapsida.”

In the large reptile tree (LRT, 1306 taxa, subset Fig. 1) Vaughnictis is the last common ancestor of Diapsida and Synapsida. Varanodon nests within the Synapsida. A series of former varanopids nest as pre-diapsids.

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

Figure 1. Subset of the large reptile tree showing the nesting of Vaughnictis at the base of the Synapsida and Prodiapsida. Higher synapsids arise from Ophiacodon. Diapsids arise from the Broomia clade. If Reisz isn’t getting this topology, he may have to add taxa. 

Reisz 2018 concludes,
“A revised and expanded data matrix and phylogenetic analysis that integrates Permo-Carboniferous synapsids and reptiles does recover a monophyletic Varanopidae within Synapsida, with Varanodon and its varanodontine sister taxa, Watongia, Varanops, Tambacarnifex, as apex, gracile predators of the early Permian, contemporaries of the larger, more massively built sphenacodontid synapsids.”

Unfortunately taxon exclusion
prevents Dr. Reisz from seeing the big picture (subset Fig. 1), published online in 2015 here and expanded since then.

References
Reisz RR 2018. Varanodon and the evolution of varanopid synapsids. SVP abstracts.

SVP 2018: Large biped in the Permian

Shelton, Wings, Martens, Sumida and Berman 2018 report,
from the same quarry that produced bipedal Eudibamus, comes a MUCH larger taxon most closely comparable to Eudibamus (Fig. 1) with long bones 10 to 24 cm in length. They report, “Given this evidence, we hypothesize that either there was an additional bipedal species that existed sypatrically with E. cursori, or these bone casts represent a later ontogenetic stage of Eudibamus with the type specimen being a juvenile.”

FIgure 1. Eudibamus scaled to femoral (=long bone) lengths of 10 and 24 cm. This makes the giant eudibamid either half a meter or a meter in snout-vent length.

FIgure 1. Eudibamus scaled to femoral (= long bone) lengths of 10 and 24 cm. This makes the giant eudibamid either half a meter or a meter in snout-vent length.

None of the present sisters
to Eudibamus (Fig. 2) in the LRT approach the size of the new bone cast specimen.

Figure 1. Basal diasids and proto-diapsids. Largely ignored these putative synapsids actually split from other synapsids while retaining the temporal fenestra trait that serves as the basis for the addition of upper temporal fenestra in diapsids. Included here are Protorothyris, Archaeovenator, Mycterosaurus, Heleosaurus, Mesenosaurus, Broomia, Milleropsis, Eudibamus, Petrolacosaurus, Spinoaequalis, and Tangasaurus.

Figure 2. Basal diasids and proto-diapsids. Largely ignored these putative synapsids actually split from other synapsids while retaining the temporal fenestra trait that serves as the basis for the addition of upper temporal fenestra in diapsids. Included here are Protorothyris, Archaeovenator, Mycterosaurus, Heleosaurus, Mesenosaurus, Broomia, Milleropsis, Eudibamus, Petrolacosaurus, Spinoaequalis, and Tangasaurus.

The authors continue to hold to their original hypothesis
that Eudibamus is a bolosaurid (Fig. 3). In the large reptile tree (LRT, 1313 taxa) bolosaurids nest with diadectids and procolophonids. Eudibamus nests with basalmost diapsids (Fig. 3).

Figure 2. Eudibamus skull revised here with new data compared to bolosaurids, on the left, and basal diapsids, on the right. Post crania for bolosaurids is very fragmentary. Bolosaurids are related to pareiasaurs and turtles, all derived from millerettids. Can you see why Eudibamus was confused with bolosaurids?

Figure 2. Eudibamus skull revised here with new data compared to bolosaurids, on the left, and basal diapsids, on the right. Post crania for bolosaurids is very fragmentary. Bolosaurids are related to pareiasaurs and turtles, all derived from millerettids. Can you see why Eudibamus was confused with bolosaurids?

It will be interesting to see
what this new Early Permian taxon looks like when it becomes available. Right now it is an outlier.

References
Shelton CD, Wings O, Martens T, Sumida SS and Berman DS 2018. Evidence of a large bipedal tetrapod from the Early Permian Tambach Formation preserved as natural bone casts discovered at the Bromacher quarry (Thuringia, Germany). SVP abstracts.

The Early Permian Ascendonanus assemblage

There are five specimens from the same pit
that were assigned to the varanid taxon Ascendonanus. Spindler et al. 2018 thought they were all conspecific.

Given their distinct proportions
(Fig. 1) and the phylogenetic differences recovered in 2 of the 5 so far (earlier one nested as a basal iguanid), we’re going to need some new generic names for at least one of the referred specimens. The others have not yet been tested in the large reptile tree (LRT, 1179 taxa).

The holotype
remains Ascendonanus, but here it’s no longer a varanopid synapsid. Here it nests as a derived prodiapsid and the basalmost tested diapsid (Fig. 2), a little younger than the oldest diapsid, Petrolacosaurus.

Figure 1. The five specimens from the Ascendonanus quarry, all to the same scale. Most images from Spindler et al. 2018. Some have skulls 3x the occiput/acetabulum length. Others as much as 5x, the first hint that these taxa are no conspecific.

Figure 1. The five specimens from the Ascendonanus quarry, all to the same scale, counter plate flipped in every specimen. Most images from Spindler et al. 2018. Some have skulls 3x the occiput/acetabulum length. Others as much as 5x, the first hint that these taxa are no conspecific.

Some of these specimens
(Fig. 1) have an occiput/acetabulum length distinct from the others, ranging from 3x to 5x the skull length, the first clue to their distinct morphologies.

Figure 2. The Prodiapsida now include the holotypes of Ascendonanus and Anningia.

Figure 2. The Prodiapsida now include the holotypes of Ascendonanus and Anningia. Remember, the Diapsida does not include any Lepidosauriforms, which nest elsewhere.

Spindler et al. 2018
did not include several taxa typically included in pelycosaur studies and should not have included any caseasaurs, despite their traditional inclusion. Spindler et al. did not include any diapsids nor did they understand the role of the former varanopids now nesting as ancestors to the Diapsida (sans Lepidosauriformes).

Figure 3. Cladogram from Spindler et al. 2018. Colors refer to clades in the LRT.

Figure 3. Cladogram from Spindler et al. 2018. Colors refer to clades in the LRT.

The holotype 0924 specimen has more of a varanopid skull
than the 1045 specimen we looked at earlier. Prodiapsid sisters include varanopids ancestral to synapsids. Prodiapsids, as their name suggests, are late-surviving ancestors to diapsids like the coeval Araeoscelis (Early Permian) and the earlier Spinoaequalis (Late Carboniferous).

Figure 3. The Ascendonanus holotype skull as originally traced and as traced here.

Figure 3. The Ascendonanus holotype skull as originally traced and as traced here. Whether an upper temporal fenestra was present (as shown in the color tracing), or not (as shown in the drawings, makes no difference as this taxon nests at the transition. 

Not sure yet
where the other three specimens assigned to Ascendonanus nest. Enough muck stirred for the moment.

References
Rößler R, Zierold T, Feng Z, Kretzschmar R, Merbitz M, Annacker V and Schneider JW 2012. A snapshot of an early Permian ecosystem preserved by explosive volcanism:
New results from the Chemnitz Petrified Forest, Germany. PALAIOS, 2012, v. 27, p. 814–834.
Spindler F, Werneburg R, Schneider JW, Luthardt L, Annacker V and Räler R 2018. First arboreal ‘pelycosaurs’ (Synapsida: Varanopidae) from the early Permian Chemnitz Fossil Lagerstätte, SE Germany, with a review of varanopid phylogeny. DOI: https://doi.org/10.1007/s12542-018-0405-9

SVP abstracts 2017: Eudibamus forelimb description

Sumida et al. 2017 bring us new information
on the pectoral region of Eudibamus, (Figs. 1,2) an early likely biped in the sprawling manner of the unrelated extant iguanian lizards, Chlamydosaurus and Basiliscus by convergence.

Unfortunately,
Sumida et al. continue to cling to the invalidated tradition that Eudibamus is a bolosaurid, largely based on convergent tooth shapes and taxon exclusion in their analyses.

Figure 1. Basal diasids and proto-diapsids. Largely ignored these putative synapsids actually split from other synapsids while retaining the temporal fenestra trait that serves as the basis for the addition of upper temporal fenestra in diapsids. Included here are Protorothyris, Archaeovenator, Mycterosaurus, Heleosaurus, Mesenosaurus, Broomia, Milleropsis, Eudibamus, Petrolacosaurus, Spinoaequalis, and Tangasaurus.

Figure 1. Basal diasids and proto-diapsids. Largely ignored these putative synapsids actually split from other synapsids while retaining the temporal fenestra trait that serves as the basis for the addition of upper temporal fenestra in diapsids. Included here are Protorothyris, Archaeovenator, Mycterosaurus, Heleosaurus, Mesenosaurus, Broomia, Milleropsis, Eudibamus, Petrolacosaurus, Spinoaequalis, and Tangasaurus.

From the Sumida et al. abstract
Eudibamus cursoris, a bolosaurid parareptile, from the Early Permian Tambach Formation (approximately 290 mybp), Thüringer Wald (Thuringian Forest), of central Germany, has been interpreted as the earliest known facultative biped. This was initially proposed based on the postcranial limb proportions in the type specimen (MNG [Museum der Natur, Gotha, Germany] 8852), but the forelimb itself has never been formally described. A nearly complete left, and partial right forelimb are preserved in the type specimen. The forelimb is less than 60% the length of the hindlimb. Only a thin, blade-like scapula is visible. Brachial, antebrachial, and manual elements are slender and elongate compared to those of other basal amniotes. The humerus has two well developed distal condyles with terminally facing articular facets. Delto-pectoral attachments were along a narrow ridge. The radius and ulna are nearly subequal in length. Conspicuously, the ulna lacks a well developed olecranon process. Carpals are proximodistally elongate compared to other basal amniotes. The intermedium and lateral centrale and the radiale and medial centrale articulate end-to-end, and their combined lengths equal that of the ulnare; the intermedium and radiale, and the medial and lateral centralia are equal in length. Four distal carpals are visible, it is unclear whether whether the fifth is truly absent or simply unossified. The distal carpal associated with digit two is reduced to a tiny pebble of bone, whereas that associated with digit four is largest and somewhat wedge shaped. Four metacarpals, likely equivalent to digits two-five, are present. The proximal portion of metacarpal two is present but length of the entire element cannot be determined. No elements of digit one can be seen, though its absence could be an artifact of preservation; however, the presence of only four distal carpals suggests Eudibamus may have had only four manual digits. Three phalanges are preserved in digits three and four. Both come to blunt tips and neither exhibits a significantly elongate penultimate element. The overall limb proportions seen in Eudibamus could suggest facultative bipedality or vertical clinging and leaping. However, vertical clingers and leapers normally have at least one is proportionately elongate manual digit and well-developed manual claws. Neither phalangeal proportions, nor the two well-developed terminal phalanges show such adaptations in Eudibamus and its interpretation as a facultative biped remains the most plausible interpretation of its postcranial anatomy.”

Figure 1. Click to enlarge. Eudibamus in situ (above), traced (middle) and reconstructed (below). The revised skull retains a large orbit and has a shorter rostrum.

Figure 1. Click to enlarge. Eudibamus in situ (above), traced (middle) and reconstructed (below). The revised skull retains a large orbit and has a shorter rostrum.

First of all,
Parareptilia has been invalidated as a monophyletic clade since 2012. 

Figure 2. Eudibamus skull revised here with new data compared to bolosaurids, on the left, and basal diapsids, on the right. Post crania for bolosaurids is very fragmentary. Bolosaurids are related to pareiasaurs and turtles, all derived from millerettids. Can you see why Eudibamus was confused with bolosaurids?

Figure 2. Eudibamus skull revised here with new data compared to bolosaurids, on the left, and basal diapsids, on the right. Post crania for bolosaurids is very fragmentary. Bolosaurids are related to pareiasaurs and turtles, all derived from millerettids. Can you see why Eudibamus was confused with bolosaurids?

Since 2011
Eudibamus has nested with other slender, speedy, basalmost archoauromorph diapsids (Araeoscelis, Petrolacosaurus and kin) (Fig. 1) in the large reptile tree, far from the squat, slow, bolosaurids, like Bolosaurus and Belebey that nest with diadectids and pareiasaurs.

Let’s look again
at the pectoral region and forelimb of Eudibamus as listed by Sumida et al. above. Note how many of these traits are also present in basal archosauromorph diapsid taxa and their outgroups shown in figure 1 above. Bolosaurids, by contrast, are known chiefly by skull material, so direct comparisons to forelimbs cannot be made.

Imagine the co-authors, grad students 
who disagree with Dr. Sumida on the phylogenetic position of Eudibamus, perhaps after testing a larger gamut of taxa or by reading this blog. All co-authors sign that they agree with what is in the abstract. This is how paleontology puts on blinders, clings to traditions and generally avoids rocking the hypotheses of senior professors.

Fortunately
non-academic renegades and independent researchers have no such restrictions, but are free to explore and experiment.

References
Sumida SS et al. 2017. Structure of the pectoral limb of the early Permian bolosaurid reptile Eudibamus cursors: further evidence supporting it as the earliest known facultative biped. SVP abstracts 2017.

Sumida 2009 Ted Talk video
What is Eudibamus?