New tanystropheid paper promotes archosauromorph myth

Colleagues. Stop promoting this myth.
Formoso  et al. 2019 report that Tanystropheus (Fig. 1) is an archosauromorph. Dr. Sterling Nesbitt, known for his widely cited, but poorly populated and scored  2011 cladogram, is a co-author. Their nesting of Tanystropheus as an archosauromorph is only possible by way of taxon exclusion and the omission of pertinent published works. Peters 2007 and the large reptile tree (LRT, 1611+ taxa, subset Fig. 2) firmly and unequivocally nest tanystropheids within the Tritosauria, within the Lepidosauria, within the Lepidosauriformes and within the Lepidosauromorpha.

Tanystropheus underwater among tall crinoids and small squids.

Figure 1. Tanystropheus in a vertical strike elevating the neck and raising its blood pressure in order to keep circulation around its brain and another system to keep blood from pooling in its hind limb and tail.

Formoso et al. report,
“Tanystropheids are a unique group of archosauromorph reptiles, which likely appeared in the Late Permian (based on inferred ghost lineages) and diversified within five million years after the end-Permian extinction.”

By contrast
the LRT nest tanystropheids as sister taxa to pterosaurs, some of which had similar elongated cervicals, all derived from basal tritosaurs like Huehuecuetzpalli, Bavarisaurus macrodactylus and Tjubina. The protorosaur, Ozmik, had elongate cervicals. None of these are mentioned in the text. Strangely there is also no citation for Fuyuansaurus and Pectodens, the basalmost taxa in the Tanystropheus clade in the LRT (subset Fig. 2). They are all Middle Triassic taxa, as are all the macrocnemids. The only known Late Permian taxa in the LRT lineage of Tanystropheus are the basal arboreal lepidosauriformes, Saurosternon and Palaegama.

So where does this
“likely appeared in the Late Permian” supposition come from?

The authors uncritically cite Sennikov 2011
who mistakenly placed his tanystropheid, Augustaburiania vatagini, in the Early Triassic, perhaps based on Sennikov’s earlier similar mistake with regard to the coeval sauropterygian Tanaisosaurus kalandadzei. No other sister taxa for either taxon predate the Middle Triassic. Sennikov describes, “The Triassic beds of the Lipovskaya Formation are eroded, overlie Carboniferous marine limestones, and are covered by Middle Jurassic continental sands and clays.” Based on phylogenetic bracketing, the Lipovskaya is a Middle Triassic formation.

Formosa et al. also cite, “Early Triassic tanystropheid elements from the Sanga do Cabral Formation of Brazil (Olsen, 1979; Casey et al., 2007; Sues and Fraser, 2010; Sues and Olsen, 2015; Pritchard et al., 2015; De Oliveira et al., 2018; Lessner et al., 2018).”

  1. Olsen 1979 refers to Tanytrachelos and the Newark Supergroup is Late Triassic-Early Jurassic.
  2. Casey et al. 2007 also refers to TanytrachelosCow Branch Formation of the Dan River Basin, part of the Newark Supergroup… Late Triassic (Carnian) age.
  3. Sues and Fraser, 2010 is a book on Triassic life.
  4. Sues and Olsen, 2015 does not appear on their list of references/citations
  5. Pritchard et al., 2015 discuss “Late Triassic tanystropheids…”
  6. De Oliveira et al., 2018 discuss,”Tanystropheid archosauromorphs in the Lower Triassic of Gondwana, Sanga do Cabral Formation of Brazil (see below).
  7. Lessner et al., 2018) report on “New insights into Late Triassic dinosauromorph-bearing assemblages”
  8. Formosa et al. assign their finds to the Middle Triassic (Anisian; 247-242 Ma).

De Oliveira et al. 2018 report,
“The fossil assemblage of the Sanga do Cabral Formation so far includes procolophonids, temnospondyls, and archosauromorphs. Vertebrate fossils are often found isolated and disarticulated. This preservation mode suggests extensive exposure and post-mortem transport of bones during the biostratinomic phase, and subsequent reworking after diagenesis.”

A Middle to Late Triassic time window for tanystropheids
is best supported here, along with a call for better editing among the several academic authors.

So, some phylogenetic and chronological problems surfaced
in Formosa et al. 2019. Reason: all scientists accept without testing, sometimes, because it’s easier. It remains important not to perpetuate myths in science, starting here and now.

Figure 5. Subset of the LRT focusing on the Tritosauria. Note the separation of one specimen attributed to Macrocnemus.

Figure 2. Subset of the LRT focusing on the Tritosauria. Note the separation of one specimen attributed to Macrocnemus.

Interesting phylogenetic note:
The clade Tanystropheidae is defined as the most recent common ancestor of MacrocnemusTanystropheus, Langobardisaurus Renesto, 1994, and all of its descendants (Dilkes 1998). In the LRT, that definition includes pterosaurs and their outgroups (Fig. 2).

Tanystropheus and kin going back to Huehuecuetzpalli.

Figure 3. Tanystropheus and kin going back to Huehuecuetzpalli. Note the scale change from the white zone to the yellow zone with duplicated taxa.

Formosa et al. report,“The Moenkopi tanystropheid cervical vertebrae belong to a considerably smaller tanystropheid than the largest Tanystropheus, but we determined that its body length was approximately three times larger than Tanytrachelos ahynis known primarily from the eastern United States.” Earlier Pritchard et al. 2015 described relatively giant Tanytrachelos specimens from the same formation. Those are not the same specimens described by Formosa et al.

Formosa KK, Nesbitt SJ, Pritchard AC, Stocker MR and Parker WG 2019. A long-necked tanystropheid from the Middle Triassic Moenkopi Fromation (Anisian) provides insights into the ecology and biogeography of tansytropheids. Palaeontologia Electronca 22.3.73 online
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Pritchard AC, Turner AH, Nesbitt SJ, Irims RB & Smith ND 2015. Late Triassic tanystropheids (Reptilia, Archosauromorpha) from northern New Mexico (Petrified Forest Member, Chinle Formation) and the biogeography, functional morphology, and evolution of Tanystropheidae. Journal of Vertebrate Paleontology 35(2):e911186, 20pp
Sennikov AG 2001. Discovery of a Primitive Sauropterygian from the Lower Triassic of the Donskaya Luka (Don Basin) and the Range of Triassic Marine Reptiles in Russia. Paleontological Journal 35(3):301–309.
Sennikov AG 2011. New Tanystropheids (Reptilia: Archosauromorpha) from the Triassic of Europe. Paleontological Journal 45(1): 90–104.

Leave a Reply

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

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

Google photo

You are commenting using your Google 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 )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.