You heard it here first: Small Tanystropheus specimens were adults, too.

Updated August 13, 2020
with a new blogpost two days later that shows where a mistake was made, how it was made, then corrected. The mistake (in Fig. 4) is retained in this post for this purpose.

Spiekman et al. 2020
used bone histology and µCT scans to determine that small Tanystropheus specimens (Fig. 1) were also adults. Six years ago, the large reptile tree (LRT, 1722+ taxa) determined the same thing using phylogenetic bracketing. That’s because…

Tanystropheids are tritosaur lepidosaurs, not archosauromorphs. 
In this clade, from Huehuecuetzpalli to Zhejiangopterus, hatchlings and juveniles are identical to adults, except for size. In other words tritosaur lepidosaurs grow isometrically (Peters 2018). Thus: differences indicate distinct genera. Spiekman et al. did not discuss this aspect of tanystropheids.

Tanystropheus and kin going back to Huehuecuetzpalli.

Figure 1. Tanystropheus and kin going back to Huehuecuetzpalli.

Spiekman et al. note:
“The configuration of the temporal region of Tanystropheus differs strongly from that of other early archosauromorphs.” 

Stuck in their traditional groove,
Spiekman et al. did not realize that tanystropheids are lepidosaurs (Peters 2007, 2011, 2018). They perpetuated the myth that tanystropheids and the similar, but unrelated Dinocephalosaurus were archosauromorphs (Fig. 2). The authors cited Pritchard et al. 2015, whose study included data from Nesbitt 2011, which was shown to be so poorly scored that Nesbitt’s cladogram changed radically after corrections were made earlier in a nine-part series ending here. Nesbitt’s repaired cladogram matched the LRT.

Spiekman et al. provided a cladogram
of interrelations (Fig. 2) that suffers from massive taxon exclusion and poor scores when compared to the LRT (Fig. 3). Spiekman et al. mix archosauromorphs with lepidosauromorphs, separates Protorosaurus from Prolacerta, separates some rib gliders from other rib gliders and matches little gliding Icarosaurus with big non-gliding Trilophosaurus among other red flags.

Figure 2. Cladogram from Spiekman et al. 2020. Colors added here to show mixing of archosauromorphs and lepidosauromorphs from the LRT.

Figure 2. Cladogram from Spiekman et al. 2020. Colors added here to show mixing of archosauromorphs and lepidosauromorphs from the LRT. Gold taxa (at right) are tritosaurs in the LRT.

Trimming the LRT to match the taxon list in Spiekman et al. 2020
(Fig. 3) results in a topology that cleanly separates lepidosauromorphs and archosauromorphs… and the tritosaur lepidosaurs, including Huehuecuetzpalli, nest together.

Figure 3. LRT reduced to Spiekman et al. taxon list. Archosauromorpha - blue. Lepidosauromorpha - yellow. Tritosauria in amber.

Figure 3. LRT reduced to Spiekman et al. taxon list. Archosauromorpha – blue. Lepidosauromorpha – yellow. Tritosauria in amber.

Spiekman et al. report,
“A quadratojugal is identified confidently for the first time in Tanystropheus.” Actually that misidentified right-angle splint of bone is an ectopterygoid (Fig. 4). What Spiekman et al. identified as an ectopterygoid is instead a crushed anterior cervical (Fig. 4).

Figure 4. Identifying the quadratojugal as an ectopterygoid here.

Figure 4. Identifying the quadratojugal as an ectopterygoid, and the ectopterygoid as a short anterior cervical.

A real quadratojugal 
was confidently identified in another specimen of Tanystropheus back in 2003 (Fig. 5). As in related taxa, including pterosaurs, the tritosaur quadratojugal is a small sharp extension of the posterior process of the jugal.

Figure 2. Skull of specimen Q of Tanystropheus. Only an arrow was added to show the location of the quadratojugal first identified in 2003.

Figure 5. Skull of specimen Q of Tanystropheus. Only an arrow was added to show the location of the quadratojugal first identified in 2003.

To distinguish the large and small tanystropheids,
the team named the bigger one T. hydroides, after the hydra in Greek mythology. Its smaller cousin kept the original species name of T. longobardicus. If they were going to do this, they should have done it right and split the several large specimens apart, as done here in 2014 (Fig. 6).

Figure 2. Tanystropheus with skull reconstructions based on two specimens, exemplar i and exemplar m.

Figure 6. Tanystropheus with skull reconstructions based on two specimens, exemplar i and exemplar m.

Bone growth rings
revealed to Spiekman et al. the smaller Tanystropheus were indeed adults, making it fairly clear that what the researchers had on their hands were two separate species, confirming results from six years ago.

Breathing
“The reptile’s skull has its nostrils perched on top, much like a crocodile’s snout – just the thing for an ambush predator to keep a lung full of air while waiting for a meal to pass by.”

This is not news. We’ve known large tanystropheids had such nostrils since at least Wild 1973. The breathing regime would have taken place as described earlier for the unrelated, but overall similar Dinocephalosaurus (Peters, Demes and Krause 2005, not cited in Spiekman et al. 2020).

Configuration
“We can now almost imagine the animal’s squat, croc-like body lying against the floor of a shallow coastline some 242 million years ago, its head rising high up to the surface so its nostrils can siphon down air, its bristling mouth slightly agape in anticipation of a stray squid to stumble by.”

This is not news either. As shown earlier with Dinocephalosaurus, the air bubble in the throat would have a difficult time moving down toward the deeper lungs while submerged without assuming a horizontal configuration, whether at the surface or sea floor, for at least that portion of the respiratory cycle. Exhaling would have been no problem in a vertical configuration. Consider the possibility of an exhaled bubble net, giving the long trachea another use: for stale air storage.

Cervicals
“Part of its oddness is the shape of the neck bones. Unlike those in a snake or lizard, the cervical vertebrae in Tanystropheus fossils are stretched out like a giraffe’s.

This is not news either. Spiekman et al. noted a diet of squid, but overlooked tanystropheids lived in crinoid forests. So, tanystropheids could have been crinoid stem mimics as shown earlier in 2012 (Fig. 7). Spiekman et al. did not discuss this possibility. Nor did he discuss why two anterior chevrons on Tanystropheus were exceptionally large. Standing as a biped these chevrons would have created a tripodal set-up for Tanystropheus.

Tanystropheus underwater among tall crinoids and small squids.

Figure 7. 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.

Pterosaur homologies
“In fact, when its remains were first uncovered in 1852, the scattered bones were assumed to be the elongated wing bones of a flying pterosaur.”

Tanystropheids also have feet identical to basal fenestrasaurs and pterosaurs with a short metacarpal 5 and elongate p5.1 (Fig. 8). Only the tanystropheid cervicals were thought to be pterosaur wing bones in 1852. Not sure why no one other than Peters (2000a, b) included pterosaurs in tanystropheid studies and vice versa.

The best matches to Prorotodactylus and Rotodactylus. In this case, something between a small Tanystropheus and an even smaller Cosesaurus provides the best matches in all regards.

Figure 8. The best matches to Prorotodactylus and Rotodactylus. In this case, something between a small Tanystropheus and an even smaller Cosesaurus provides the best matches in all regards. These taxa were not even mentioned by Niedwiedcki et al. (2013) and skeletal fossils are known from geographically and chronologically similar sediments.

A valid phylogenetic context is key to understanding 
what a taxon is. Spiekman et al. lacked this understanding and context despite having seven co-authors, many with PhDs. Adding taxa and correcting scores clarifies all issues. Borrowing analyses perpetuates myths. Citing competing hypotheses might have helped this paper. Their µCT scans did not prevent them from including two mis-identifications, (noted above).


References
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Peters D, Demes B and Krause DW 2005. Suction feeding in Triassic Protorosaur? Science, 308: 1112-1113.
Pritchard AC, Turner AH, Nesbitt SJ, Irmis RB and 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 Vertebrrate Paleontology 35, e911186.
Spiekman SNF et al. (6 co-authors) 2020. Aquatic Habits and Niche Partitioning in the
Extraordinarily Long-Necked Triassic Reptile Tanystropheus. Current Biology 30:1–7. https://doi.org/10.1016/j.cub.2020.07.025
Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus (Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-162 plus plates.

https://pterosaurheresies.wordpress.com/2019/11/28/new-tanystropheid-paper-promotes-archosauromorph-myth/

https://pterosaurheresies.wordpress.com/2019/12/19/spiekman-and-scheyer-2019-discuss-variation-in-tanystropheus/

https://pterosaurheresies.wordpress.com/2014/10/17/the-many-faces-of-tanystropheus/

https://www.sciencealert.com/half-of-this-ancient-reptile-s-body-is-made-of-neck-and-we-now-know-how-it-used-it

From October 2018:
researchgate.net/publication_A_new_lepidosaur_clade_the_Tritosauria

From September 2011:
https://pterosaurheresies.wordpress.com/2011/09/22/the-tritosauria-an-overlooked-third-clade-of-lizards/

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