Teyujagua: Not “transitional between archosauriforms and more primitive reptiles”

A new paper by Pinheiro et al. 2016
reports that the small skull (UNIPAMPA 653) of a new genus, Teyujagua paradoxa (Figs. 1, 2), is “transitional in morphology between archosauriforms and more primitive reptiles. This skull reveals for the first time the mosaic assembly of key features of the archosauriform skull, including the antorbital and mandibular fenestrae, serrated teeth, and closed lower temporal bar. Phylogenetic analysis recovers Teyujagua as the sister taxon to Archosauriformes…”

Well, that might be true if
you restrict the taxon list to the few (44) taxa employed by Pinheiro et al.

But when you expand the taxon list
to the size of the large reptile tree (660+ taxa) where we already have a long list of Youngina, Youngoides (Fig. 1) and Youngopsis sisters to Archosauriformes, then Teyujagua nests as a phylogenetically miniaturized sister to the NMQR 1484/C specimen attributed to Chasmatosaurus alexandri (Fig. 1). Like another phylogenetically miniaturized descendant of chasmatosaurs, Elachistosuchus huenei MB.R. 4520 and BPI 2871 (Figs. 3, 4), Teyujagua also turned its once large antorbital fenestra into a vestige (Figs. 1, 2).

Figure 1. Teyujagua compared to sister taxa, including Youngoides, Proterosuchus and Chasmatosaurus. Teyujagua is a phylogenetic miniature in which the antorbital fenestra became a vestige.

Figure 1. Teyujagua compared to sister taxa, including Youngoides, Proterosuchus and Chasmatosaurus. Teyujagua is a phylogenetic miniature in which the antorbital fenestra became a vestige. Note the posterior jugal, which may or may not have supported a now missing quadratojugal anterior process.

I can see why the authors got so excited about their discovery.
The Teyjjagua skull looks like a little Chasmatosaurus skull without the antorbital fenestra. That’s because it IS one. In their own words, “This skull represents a previously unknown species that is the sister taxon to Archosauriformes and which fills a major morphological gap in understanding of early archosauriform evolution.”

Unfortunately, the authors were dealing with an antiquated cladogram
in which Youngina is basal to lizards and archosaurs… among many, many other atrocities.  They report, “Our novel cladistic analysis recovered two most parsimonious trees with 872 steps. The strict consensus of these topologies positions Teyujagua as the sister taxon of Archosauriformes, a position previously occupied by the Lower Triassic Prolacerta.”

So this is where it really pays off
to use several specimens from the Youngina grade and several specimens from the Proterosuchus grade along with 660+ opportunity taxa to nest with.

Figure 2. The rostrum of Teyujagua with the vestigial antoribital fenestra circled here. You can see how the maxilla grew over the opening. Once again, this is data that should have been announced from firsthand observation by PhD level paleontologists, not from a casual observer of photographic data.

Figure 2. The rostrum of Teyujagua with the vestigial antoribital fenestra circled here. You can see how the maxilla grew over the opening. Once again, this is data that should have been announced from firsthand observation by PhD level paleontologists, not from a casual observer of photographic data.

Diagnosis (from the paper)
“Archosauromorph with the following unique character combination: confluent, dorsally positioned external nares; maxilla participating in orbital margin; antorbital fenestra absent; trapezoidal infra temporal fenestra with incomplete lower temporal bar; teeth serrated on distal margins; surangular bearing a lateral shelf; external mandibular fenestrae present and positioned beneath the orbits when the lower jaw is in occlusion (autapomorphic for Teyujagua).”

Comments on the diagnosis
The NMQR 1484/C specimen of Chasmatosaurus (Fig. 1) is pretty well preserved except for the premaxilla/narial region. Given the morphology of the Teyujagua rostrum, the NMQR specimen likely shares the trait of a dorsal naris, perhaps with a slender ascending process of the premaxila, which might be lost in both specimens. The maxilla actually does not appear to reach the orbit. The antorbital fenestra remains present as a closed over vestige. The lower temporal bar might be incomplete, but just as likely the anterior process of the quadratojugal might be taphonomically missing, as in the NMQR specimen (Fig. 1). Other proterosuchids have similar tooth serrations. The mandibular fenestra is further forward, but the posterior mandible is also deeper. The specimen is indeed distinct enough to merit a unique generic name, as is the case with several of the Chasmatosaurus/Proterosuchus specimens, which do NOT represent a growth series.

Phylogenetic miniaturization
has reduced the antorbital fenestra in BPI 2871 and Elachistosuchu, which nest at the base of the Choristodera. Both nest as descendants of larger Chasmatosaurus specimens in the large reptile tree.

Figure 1. Elachistosuchus (Janensch 1949, Sobral et al. 2015) is a sister to BPI 2871, a basal choristodere.

Figure 3. Elachistosuchus (Janensch 1949, Sobral et al. 2015) is a sister to BPI 2871, a basal choristodere.

Not mentioned by the authors
The miniaturized skull of Teyujagua has fewer teeth than in sister or ancestors, but matching the condition in Euparkeria (Fig. 1), a related taxon only one node away at the base of a sister clade.

Rostral area of BPI 2871, formerly considered a younginid and here nesting at the base of the Choristodera.

Figure 4. Rostral area of BPI 2871, formerly considered a younginid and here nesting at the base of the Choristodera as a descendant of Chasmatosaurus.

If you don’t remember
this earlier post (2011), Youngoides (UC1528, Fig. 5) had the genesis of an antorbital fenestra. It is the current proximal sister to the Archosauriformes in the large reptile tree.

Figure 1. GIF movie tracing the antorbital fenestra with fossa and surround bones of the FMNH UC 1528 specimen of Youngoides romeri. This is one of the earliest and most primitive appearances of the archosauriform antorbital fenestra, previously overlooked.

Figure 5. GIF movie tracing the antorbital fenestra with fossa and surround bones of the FMNH UC 1528 specimen of Youngoides romeri. This is one of the earliest and most primitive appearances of the archosauriform antorbital fenestra, previously overlooked.

In summary, the authors report
“Teyujagua presents an unexpected combination of basal archosauromorph and typical archosauriform features. For example, Teyujagua resembles basal archosauromorphs in lacking an antorbital fenestra and retaining open lower temporal bars1. However, Teyujagua possesses external mandibular fenestrae and serrated teeth, features previously considered unique to Archosauriformes.”

Unfortunately, the authors appear to forget
that the antorbital fenestra can phylogenetically disappear and Chasmatosaurus demonstrates that the quadratojugal can wither phylogenetically or taphonomically disappear. It is a fragile bone.

References
Pinheiro FL, França MAG, Lacerda MB, Butler RJ and Schultz CL 2016. An exceptional fossil skull from South America and the origins of the archosauriform radiation. Nature Scientific Reports 6:22817 DOI: 10.1038/srep22817.

Advertisements

4 thoughts on “Teyujagua: Not “transitional between archosauriforms and more primitive reptiles”

  1. “Thank you” for your ridiculous and insulting post. Hopefully, one day a team of professional paleontologists who have spent months working first hand on a specimen will be able to publish a paper that your superior observation skills are not able to demolish within 24 hours on the basis of highly imaginative examination of photographs.

    Pinheiro et al. discovered, excavated, prepared and studied the specimen. Don’t you think they might have spotted the “antorbital fenestra” you claim to see based on a photograph if it was really there?

    • The fact is, as Pinheiro et al. report, the antorbital fenestra is not there any more. We all agree on that. The antorbital fenestra is scored as ‘absent’ in the matrix. However, the cladogram indicates that is the derived, not the primitive condition. As you know, sometimes the antorbital fenestra disappears through phylogeny. This is one of those cases. Take a chill pill please.

  2. If your analysis is “more robust” than others, why not publish it? Based on your words, your matrix and analysis have high taxa and characters number. Hennig certainly privilege the quality of the characters and take into account the priori weighing: the influence of the observer on the object. If you want to do science, please, sit your ass in the chair and write a manuscript.

    • It’s been done several (over ten) times. Always with rejection. That’s why you see no publications from me since 2009. Thanks for your suggestion. See today’s post in about 2 hours for further thoughts on that matter.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s