Sookias et al. 2020: Euparkeria updated, cladogram outdated

Cutting to the chase: 
No one has studied and published on Euparkeria (Figs. 3-6) more than Roland Sookias and his colleagues (Sookias et al.  2014, Sookias 2016, Sookias et al. 2020). Unfortunately taxon exclusion mars all of his work (Figs. 1, 2), including his latest, otherwise terrific paper presenting close-up and µCT scans from the ten specimens found in a single locality, all attributed to Euparkeria. This paper is so rich in data, but so poor and misleading in systematics.

From the abstract:
“The archosauriform Euparkeria capensis from the Middle Triassic (Anisian) of South Africa has been of great interest since its initial description in 1913, because its anatomy shed light on the origins and early evolution of crown Archosauria and potentially approached that of the archosaur common ancestor.”

In the large reptile tree (LRT, 1714+ taxa, subset Fig. 1) Euparkeria nests far from Archosauria (= the last common ancestor of birds + crocs). Instead Euparkeria nests at the base of the Euarchosauriformes (= all archosauriforms closer to Euparkeria than to Proterosuchus and the pararchosauriforms, Fig. 1). These clades were separated in 2012 here, and that split has remained steady despite many additional taxa.

Figure 1. Subset of the LRT focusing on Archosauriformes. Clade colors match figure 2 overlay.

Figure 1. Subset of the LRT focusing on Archosauriformes. Clade colors match figure 2 overlay.

Phylogenetic analysis
Sookias et al. 2020 worked from a dataset in Sookias 2016. Sookias 2016 was built on the invalidated Nesbitt 2011 and Sookias et al. 2014. The Sookias et al. 2020 results are typical whenever taxon exclusion shuffles the clades, mixing unrelated taxa together. Clades nest where they do in Sookias 2020 by default. That’s how you get crocs and phytosaurs nesting together and euparkeriids arising from erythrosuchids (Fig. 2), rather that the other way around, as in the LRT (Fig. 1). We’re also wary of any cladogram that includes suprageneric taxa.

Figure 2. Sookias et al. 2020 cladogram lacks enough taxa compared to the LRT (Fig. 2) and so shuffles clades here. Here crocs nest within 'Other Pseudosuchia' and pterosaurs nest within Ornithodira, two clades invalidated by the LRT by adding taxa. Promoting this outdated myth of interrelationships in 2020 is not professional.

Figure 2. Sookias et al. 2020 cladogram lacks enough taxa compared to the LRT (Fig. 2) and so shuffles clades here. Here crocs nest within ‘Other Pseudosuchia’ and pterosaurs nest within Ornithodira, two clades invalidated by the LRT by adding taxa. Promoting this outdated myth of interrelationships in 2020 is not professional. Dongusuchus and Dorosuchus are know from bits and pieces of the post-crania.

Euparkeria has been studied previously,
but never so completely as in Sookias et al. 2020. As in Ewer (1965, Fig. 3) Sookias et al. present a freehand diagram chimaera skull (Figs. 4, 5) that combines data from several specimens they consider to be conspecific.

Figure x. Previous views of Euparkeria.

Figure 3. Previous views of Euparkeria.

Comparing a photo of the SAM 5867 specimen
to the Sookias et al. diagram may be instructive. Did they get all the details right?

Figure x. How does the skull of the 5867 specimen of Euparkeria compare to the diagram? Here they are to the same scale.

Figure 4. How does the skull of the 5867 specimen of Euparkeria compare to the diagram? Here they are to the same scale. You decide on the details.

Several color photos were included in Sookias et al. 2020,
so it is surprising that their diagram lacks colors (Fig. 5 left column). When colors are added, the bones lump and separate as well as the LRT lumps and separates taxa.

Figure x. Diagram from Sookias 2020 at left. Rearranged and colored at right for ease of viewing.

Figure 5. Diagram from Sookias et al.  2020 at left. Rearranged and colored at right for ease of viewing.

Using a little DGS on a skull tracing of the SAM 4067a specimen
(Fig. 6) permits one to copy and paste elements from the left and right to create a reconstruction (Fig. 6) without reverting to the unconscious bias that attends all freehand drawings. Broom 1913 assigned this specimen to Browniella africana. Haughton 1922 considered Browniella a junior synonym and this synonymy has been accepted by all prior workers. No prior workers provided a reconstruction for accurate scoring. They just  ‘eye-balled’ the roadkill skull.

Figure 1. The SAM 4967a specimen attributed to Euparkeria. Images from Sookias et al. 2020 with colors and reconstruction added here.

Figure 6. Browniella africana, the SAM 4967a specimen attributed to Euparkeria. Images from Sookias et al. 2020 with colors and reconstruction added here.

Euparkeria capensis (Broom 1913, SAM 5867) Early Triassic, ~247 mya, 60 centimeter length is derived from the FMNH UC 1528 specimen of Youngoides (Fig. 7), a taxon ignored by Sookias et al. An unpublished paper can be found on ResearchGate.net.

The SAM 5867 specimen of Euparkeria nests between Pararchosauriformes, like Polymorphodon (Fig. 8), and all higher Euarchosauriformes like Garjainia (Fig. 9). The SAM 5867 specimen nests at the base of the Euparkeriidae, which presently include only two other tax, the SAM 4067a specimen (Fig. 6) and Osmolskina, which nest with each other (Fig. 1).

Figure 1. Youngoides romeri FMNH UC1528 demonstrates an early appearance of the antorbital fenestra in the Archosauriformes. This specimen is the outgroup to Proterosuchus, the traditional basal member of the Archosauriformes. 

Figure 7. Youngoides romeri FMNH UC1528 demonstrates an early appearance of the antorbital fenestra in the Archosauriformes. This specimen is the outgroup to the Archosauriformes.

Figure 1. Skull elements of Polymorphodon.

Figure 8. Skull elements of Polymorphodon, basal to proterochampsids.

Figure 1. Garjainia at several scales and views.

Figure 9. Garjainia at several scales and views.

Osmolskina czatkowicensis (Borsuk-Biaynicka and Evans 2009), Early Triassic,

Browniella africana  (Fig. 6, SAM 4067A) is a eurparkeriid more closely related to Osmolskina in the LRT.

Sometimes additional detail comes in handy.
And Sookias et al.  2020 provided that additional detail.

Unfortunately, without a valid phylogenetic context
you won’t know the outgroups, ingroups, ancestors and descendants of any taxon under your µCT scanner. Sometimes you need a metaphorical ‘panoramic camera’ like the LRT, for that wide gamut view that minimizes taxon exclusion.


References
Broom R 1913. On the South-African Pseudosuchian Euparkeria and Allied Genera. Proceedings of the Zoological Society of London 83: 619–633.
Borsuk-Bialynicka M and Evans SE 2009. Cranial and mandibular osteology of the Early Triassic archosauriform Osmolskina czatkowicensis from Poland. Palaeontologia Polonica 65, 235–281.
Ewer RF 1965. The Anatomy of the Thecodont Reptile Euparkeria capensis Broom Philosophical Transactions of the Royal Society London B 248 379-435.
doi: 10.1098/rstb.1965.0003
Haughton S 1922. On the reptilian genera Euparkeria Broom, and Mesosuchus Watson. Transactions of the Royal Society South Africa 10, 81–88. (doi:10.1080/00359192209519270
Nesbitt SJ 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bull. Am. Mus. Nat. Hist. 352, 1–292. (doi:10.1206/352.1)
Nesbitt SJ et al. 2017 The earliest bird-line archosaurs and the assembly of the dinosaur body plan. Nature 544, 484–487.
Sookias RB, Sullivan C, Liu J, Butler RJ. 2014 Systematics of putative euparkeriids (Diapsida: Archosauriformes) from the Triassic of China. PeerJ2, e658 (doi:10.7717/peerj.658)
Sookias RB 2016. The relationships of the Euparkeriidae and the rise of Archosauria. Royal Soceity open science 3, 150674. (doi:10.1098/rsos. 150674)
Sookias RB, Dilkes D, Sobral G, Smith RMH, Wolvaardt FP, Arcucci AB, Bhullar B-AS and Werneburg I 2020. The craniomandibular anatomy of the early archosauriform Euparkeria capensis and the dawn of the archosaur skull. R. Soc. Open Sci. 7: 200116.
http://dx.doi.org/10.1098/rsos.200116

https://www.researchgate.net/publication/328388486_Youngoides_romeri_and_the_origin_of_the_Archosauriformes

wiki/Osmolskina
http://reptileevolution.com/euparkeria.htm
http://reptileevolution.com/osmolskina.htm

Cladogram quirk and basalmost Euarchosauriformes

Updated July 31, 2020
with so many additional taxa, the LRT is no longer completely resolved. Many headless taxa nest with skull only taxa, which leads to loss of resolution. The LRT is built taxon upon taxon, day by day. Updated data on Browniella and Euparkeria are provided along with an updated subset of the LRT. The new data moved Browniella closer to Osmolskina.


I’ve claimed on several occasions 
that my cladogram was fully resolved and all of its subsets were also fully resolved. While that is typically true, everyone prefers a cladogram with more strength, where the taxa are lumped and separated by at least three points in Bootstrap Analysis. When that happens the Bootstrap tree will also be completely resolved (= all scores 50-100).

I found a quirk
And as I write this I am going to figure out why this happened and wonder if it can be repaired. Typically a bad score or several bad scores are responsible for any lack of resolution. Not sure if that’s the case this time.

Follow me
as I describe the setup and the problem. I’m looking to apply Bootstrap scores to members of the basal Archosauriformes with the addition of Teyujagua, a proterosuchid we looked at earlier.

  1. A heuristic search algorithm using PAUP of the entire cladogram: fully resolved. 
  2. The same deleting all anamniotes and lepidosaurormorpha — the new Archosauromorpha (Eldeceeon and all derived taxa) remains: fully resolved.
  3. The same deleting all basal archosauromorphs and synapsids: the protodiapsida (Myceteosaurus and all derived taxa) remains: fully resolved.
  4. The same deleting all basal protodiapsids and basal diapsids: the new younginiforms  (Spinoaequalis and all derived taxa) remains: fully resolved.
  5. The same deleting all aquatic younginiforms: the terrestrial younginiforms: Spinoaequalis + the SAM K7710 specimen(s) of Youngina and all derived taxa) remains: fully resolved.
  6. Now, working backwards: The same deleting all dinosaurs: 6 trees retained. Loss of resolution in the Protodinosauria. Several incomplete taxa based on drawings there. We’ll reexamine that clade in a later post.
  7. The same adding Herrerasaurus: fully resolved. A more complete data specimen solves the problem in #6.
  8. The same deleting all archosaurs: fully resolved.
  9. The same deleting the protoarchosaurs (the Gracilisuchus clade): fully resolved.
  10. The same deleting all the poposaurs: fully resolved.
  11. The same deleting all the Arizonasaurus/Ticinosuchus/Aetosaurus clade: fully resolved. 
  12. The same deleting all remaining Rauisuchia (Vjushkovia through Postosuchus): fully resolved.
  13. The same deleting all erythrosuchidae and ornithosuchidae: 2 trees retained. Loss of resolution at the Euparkeria node.
  14. The same adding Garjainia: fully resolved. 
  15. The same deleting all Choristodera: fully resolved.
  16. The same deleting all Chanaresuchidae and Parasuchia: fully resolved.
  17. At this point with a single tree scoring 447, I attempted a Bootstrap analysis. Basically all that is left here are the basal terrestrial younginiforms including several Youngina and Youngoides specimens, protorosaurs and basal archosauriforms up to and including all tested proterosuchids + Euparkeria, Osmolskina and Garjainia. Here  the small Proterosuchus skull (BPI/1/4016) and Elaphrosaurus rubidgei (RC59) are apparently mucking up the works, even though they do not nest together otherwise.
  18. The same adding Diandongosuchus, a basal parasuchian: fully resolved.
  19. At this point with a single tree scoring 488, warrants another Bootstrap analysis. Again Elaphrosuchus scores insufficiently distinct from several other included taxa to lack a score of 50+ across four other clades. And a very low score of 51 separates Elaphrosuchus from the BPI/1/4016 specimen of Proterosuchus. Both are skull only taxa and both have a certain amount of damage.
  20. The same deleting the new taxon, Teyujagua: Bootstrap scores all above 50. So that addition caused problems.

Are there scoring errors here? 
Or do these taxa converge? Or do two sisters lack any data points in common? Let’s find out by taking a closer look at the offending parties.

[About a day or two elapses at this point in the narrative]

Scoring errors
There were many errors around these nodes, hopefully all are now repaired. I reexamined several drawings, photos and tracings. Unfortunately fossil bones don’t come with overlying colors, so they have to be interpreted.

I also added a taxon
(Figs, 1, 2). It turned out to be a key transitional taxon. Score corrections and the new taxon boosted 5/6 of the Bootstrap scores.

Figure 1. The SAM 4967a specimen attributed to Euparkeria. Images from Sookias et al. 2020 with colors and reconstruction added here.

Figure 1. The SAM 4967a specimen attributed to Euparkeria. Images from Sookias et al. 2020 with colors and reconstruction added here.

Adding the ‘other Euparkeria‘: SAM PK K6047A
While reexamining the images of the Euparkeria holotype in Ewer 1967, I compared the rostrum that has a naris (SAM PK K6047A) with the classic holotype (SAM PK K 5867) that lacks a naris (Fig. 1). The fossils did not match. The dimensions were off (orbit vs antorbital fenestra, etc.) and the teeth were different in length. Ewer provides two images of the 6047 specimen, lacking data for the middle rostrum between the pix. The tracing (Fig. 1) recovers a basal euarchosauriform with a longer rostrum and narrower orbit, more like that of its phylogenetic predecessor, the BPI/1/4016 specimen of Proterosuchus (Fig. 3). This taxon ties Euparkeria more closely (more gradual transition in traits) to Proterosuchus (Figs. 2, 3).

There is also a SAM PK K6047B specimen
and it has been named Browniella africana by Broom (1913) I have not seen it. I do not know if it resembles or was found with the 6047A specimen. Most workers consider this taxon a junior synonym of Euparkeria.

Sookias and Butler 2013
reviewed the Euparkeriidae, but did not mention the 6047A or B specimens, except, perhaps as two of the eleven specimens that comprise their hypodigm. They defined the clade in this fashion: “Euparkeriidae Huene 1920. Stem-based definition –the most inclusive clade containing Euparkeria capensis Broom 1913a but not Crocodylus niloticus Laurenti 1768 or Passer domesticus Linnaeus 1758. (new).” I have not tested all the taxa listed by Sookias and Butler, but their definition seems to be overly broad.

Figure 1. Subset of the LRT focusing on Archosauriformes. Clade colors match figure 2 overlay.

Figure 1. Subset of the LRT focusing on Archosauriformes. Clade colors match figure 2 overlay.

What do we learn here?

  1. Incomplete taxa can cause loss of resolution, as everyone knows. The addition of a more complete cousin can provide the remedy.
  2. Scoring errors also lead to loss of resolution.
  3. There is only one tree, the tree of Nature, that we are trying to model here. So there IS a correct solution to this problem.
  4. Adding taxa almost always provides traits that make phylogenetic transitions more gradual. The only exceptions are terminal taxa, those that lack descendants.
  5. Known proterosuchids still do not represent ontogenetic (maturation) stages. They are phylogenetically distinct taxa that lead to more derived clades (Figs. 2,3).
  6. There is still no evidence for the sisterhood of Euparkeria with the verified sisters Turfanosuchus and Gracilisuchus  (Sookias and Butler 2013, Butler et al. 2014).
  7. Phylogenetic miniaturization preceded and was part of the basal archosauriform radiation.
  8. It is important for professionals not to assume that different specimens represent a single species. Minor differences might turn out to be key traits as demonstrated here.
Figure 3. Click to enlarge. Updated image of various proterosuchids and their kin. When you see them all together it is easier to appreciated the similarities and slight differences that are gradual accumulations of derived taxa.

Figure 3. Click to enlarge. Updated image of various proterosuchids and their kin. When you see them all together it is easier to appreciated the similarities and slight differences that are gradual accumulations of derived taxa. In the white zone are specimens considered proterosuchids.

Finally: the value of a large gamut cladogram
becomes more valuable with every added taxon. More gradual transitions become apparent and bias is further minimized.


References
Broom R 1913. On the South-African Pseudosuchian Euparkeria and Allied Genera. Proceedings of the Zoological Society of London 83: 619–633.
Butler RJ, Sullivan C, Ezcurra MD, Liu J, Lecuona A and Sookias RB (2014). New clade of enigmatic early archosaurs yields insights into early pseudosuchian phylogeny and the biogeography of the archosaur radiation. BMC Evolutionary Biology 14:1-16.
Ewer RF 1965. The Anatomy of the Thecodont Reptile Euparkeria capensis Broom Philosophical Transactions of the Royal Society London B 248 379-435.
doi: 10.1098/rstb.1965.0003
Sookias RB and Butler RJ 2013. Euparkeriidae. Geological Society, London, Special Publications published online January 24, 2013 as doi: 10.1144/SP379.6

 

 

 

Evolution basics – starring Jon Stewart and Babe Ruth

Evolution does not work in mysterious ways.
The basics (small variations leading over dozens of generations to larger changes) are simple:

GIF movie 1. Skull width as a variable demonstrated by Babe Ruth and John Stewart in this animated GIF file.

GIF movie 1. Skull width as a variable demonstrated by Babe Ruth and John Stewart in this animated GIF file.

  1. wider / narrower (skull, body, feet, etc.)
  2. taller-larger / smaller-shorter
  3. longer (more ribs) / shorter (fewer ribs)
  4. longer limbs / shorter limbs
  5. larger skull / smaller skull
  6. longer preorbital region / longer postorbital region
  7. longer neck / shorter neck
  8. sharp claws / rounded claws
  9. etc. / etc.

At left 
are extinct baseball star, Babe Ruth, and extant comedian/commentator, Jon Stewart, graphically demonstrating #1 on the above list, wider / narrower in the skull shape. Both are male members of the species Homo sapiens.

Other traits
one can add to this list include various perforations or fenestrae (which have several and often convergent origins and disappearances:

  1. fenestra between the naris and orbit (antorbital fenestra)
  2. fossa surrounding antorbital fenestra
  3. one or more fenestrae between the orbit and occiput
  4. fenestra in the mandible
  5. occipital fenestrae expand over braincase
  6. acetabulum perforated or not

And once fenestrae are formed:

  1. Loss of lower temporal arch
  2. Loss of upper temporal arch
  3. Loss of both

Then add
the size and shape of various bones and their processes compared to other bones and you have yourself a long character list. Enough of these (150+) provide a good matrix of characters and character states that can produce the menagerie of reptiles found in the large reptile tree, now numbering 566 taxa for 228 characters.

The wider / narrower and smaller / larger dichotomies 
can also be seen in the variety of specimens attributed to Proterosuchus and Chasmatosaurus (Fig. 2, Broom 1903). Some paleontologists (Welman 1998, Ezcurra  and Butler 2015) consider these taxa congeneric. They think this variety constitutes an ontogenetic series. On the other hand, the large reptile tree recovered these taxa in distinct nodes and clades. Narrower-skulled forms nest together. So do wider-skulled forms and they lead to other even more distinct taxa, including some once again tiny forms. The tall-skulled proterosuchids do not lead to more derived taxa.

Figure 3. The many faces of Proterosuchus to scale and in phylogenetic order, among with their closest known relatives. Note the phylogenetic miniaturization, reduction of the drooping premaxilla and loss of the antorbital fenestra after the TM 201 specimen of Chasmatosaurus. Click to enlarge.

Figure 2. The many faces of Proterosuchus to scale and in phylogenetic order, among with their closest known relatives. Note the phylogenetic miniaturization, reduction of the drooping premaxilla and loss of the antorbital fenestra after the TM 201 specimen of Chasmatosaurus. Click to enlarge.

The smallest taxon
shown here (Fig. 2), Youngoides romeri, leads to euparkeriids and then to a long list of archosauriforms including dinosaurs, crocs and birds. This last common ancestor of proterosuchids and euparkeriids (all archosauriforms) also had a small antorbital fenestra.

Have a great weekend!
Keep those cards and letters coming.

References
Broom R. 1903. On a new reptile (Proterosuchus fergusi) from the Karroo beds of Tarkastad, South Africa. Annals of the South African Museum 4: 159–164.
Ezcurra MD and Butler RJ 2015. Post-hatchling cranial ontogeny in the Early Triassic diapsid reptile Proterosuchus fergusi. Journal of Anatomy. Article first published online: 24 APR 2015. DOI: 10.1111/joa.12300
Welman J 1998. The taxonomy of the South African proterosuchids (Reptilia, Archosauromorpha). Journal of Vertebrate Paleontology 18 (2): 340–347.

Sometimes the larger sister has the more juvenile traits.

A few posts ago we noted the interesting fact that the larger Garjainia  (Otchev 1958, Early Triassic ~240 mya, 2 m. long) had the relatively larger skull compared to its sister, Euparkeria  (Broom 1913 Early Triassic, ~240 mya, 60 cm). Generally a larger head is considered a juvenile trait. Garjainia also had a shorter tail and a shorter torso.

In the background is Garjainia, a basal erythrosuchid. Euparkeria is at its ankles, both to scale. Euparkeria is the more derived taxon. Below the tail of Euparkeria is a greatly reduced Garjainia. No fossils exist that show Garjainia to this size.

Figure 1. In the background is Garjainia, a basal erythrosuchid. Euparkeria is at its ankles, both to scale. Euparkeria is the more derived taxon. Below the tail of Euparkeria is a greatly reduced Garjainia as if a juvenile of Euparkeria. No fossils exist of Garjainia at this size.

On the other hand
Euparkeria did have the slightly larger orbit, a trait generally considered juvenile. The skull of Euparkeria also had smoother contours (no pmx/mx notch, less of a jugal descent).

Evolution Uses Premature Maturation
The greatly reduced size of Euparkeria is yet another example of a new clade arising from shrimps arising from old clades. Others have complained that size is not pertinent to phylogenetic matrices, but this example shows otherwise. Deciding where to draw “the line” will continue to be argued, no doubt.

Figure 3. Here Euparkeria nests between Garjainia, a basal erythrosuchid, and Ornithosuchus following the nestings recovered by the large reptile tree. All three share a suite of traits that do not include a long narrow rostrum and a dorsal naris, among other traits.

Figure 2. Here Euparkeria nests between Garjainia, a basal erythrosuchid, and Ornithosuchus, an ornithosuchid, following the nestings recovered by the large reptile tree. Note the relative size of the skull in Garjainia, much larger than the much smaller Euparkeria.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Broom R 1913. On the South-African Pseudosuchian Euparkeria and Allied Genera. Proceedings of the Zoological Society of London 83: 619–633.
Ewer RF 1965. The Anatomy of the Thecodont Reptile Euparkeria capensis Broom Philosophical Transactions of the Royal Society London B 248 379-435.
Otchev VG 1958. Novye dannye po pseudozukhiyam SSSR: Doklady Akademii Nauk SSR, 123(4):749-751.
Parrish JM 1992. Phylogeny of the Erythrosuchidae. Journal of Vertebrate Paleontology 12:93–102.

wiki/Euparkeria
wiki/Garjainia