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/

Plesiosaur necks: not so flexible after all

With a neck WAAAYYY longer than half the total length
elasmosaurs, like Albertonectes (Figs. 1, 2), have been traditionally referred to as ‘a snake threaded through a sea turtle’ (going back to the Buckland lectures 1832, full story online here). Snakes have no trouble swimming, but so far, paleontologists have not considered the long, minimally flexible neck of elasmosaurs a propulsive organ, as in sea snakes. That might change a little today.

Figure 1. A weak attempt at making sine waves in the neck of Albertonectes.

Figure 1. A weak attempt at making sea snake-like sine waves in the neck of Albertonectes. Note the minimum of bending through effort. Relaxation realigned the neck.

Earlier a vertical configuration was suggested
to explain the weird and extreme morphology of elasmosaurs, entering fish and squid schools from below, distinct from all other oceanic predators. While the flippers were powerful propulsive organs for long distance, when it came to fine tuning while hovering, perhaps the increasingly longer (Fig. 2), snake-like necks helped some. It also moved the bulky flapping torso further from the mouth, so the school of fish would be less and less  likely to notice the intruder in the middle.

Figure 3. Click to enlarge. Albertonectes reconstructed. This 11 m elasmosaur is the longest thusfar recorded. This may be the breathing pose, swallowing air, then submerging the neck. When horizontal the air could be passed back to the lungs, as hypothesized for Dinocephalosaurus.

Figure 2. Click to enlarge. Albertonectes reconstructed. This 11 m elasmosaur is the longest thusfar recorded. This may be the breathing pose, swallowing air, then submerging the neck. When horizontal the air could be passed back to the lungs, as hypothesized for Dinocephalosaurus.

By contrast, Noe, Taylor and Gomez-Perez 2017 reported,
Based on the anatomy of the articular faces of contiguous cervical vertebral centra, neural arches, and cervical ribs, the plesiosaur neck was mainly adapted for ventral bending, with dorsal, lateral and rotational movements all relatively restricted. A new model is proposed for the plesiosaur bauplan, comprising the head as a filter, straining, sieve feeding or sediment raking apparatus, mounted on a neck which acted as a stiff but ventrally flexible feeding tube, attached to the body which acted as a highly mobile feeding platform.”

“The neck increased drag due to its form and large surface area, but was also potentially part of an integrated locomotor system, for instance affecting steering (as it lies in front of the locomotor apparatus) and because the rear of the neck acted as anchorage for musculature from the anterior limb girdles. Hence, any explanation of neck function should consider both slow speed locomotion and more rapid movement during respiration, feeding and predator avoidance.”

Their study looked at
Muraenosaurus (Figs. 3, 4), Cryptoclidus and Tricleidus (none if these yet in the LRT) as exemplars of long-necked plesiosaurians. All are related to one another, not to elasmosaurs. Noe, Taylor and Gomez-Perez presented a history of plesiosaur neck interpretation and presented their own interpretation (ventral flexion, Fig. 5). Given that comprehensive review, apparently no prior workers envisioned a sea-snake analog for the long neck of elasmosaurs, nor have any envisioned a vertical feeding orientation.

Figure 2. Muraenosaurus in dorsal and lateral views. Compare to figure 1.

Figure 2. Muraenosaurus in dorsal and lateral views. Compare to figure 1.

Rather than a flexible ball-and-socket joint
between cervicals, each plesiosaur vertebra consisted of a spool-shaped centrum with flat or slightly concave articular surfaces (Fig. 4). Most cervical centra are wider than deep. according to Noe, Taylor and Gomez-Perez, but that is largely due to a dorsal indentation for the neural spine. Cervicals preserved in situ indicate no intervening cartilage between centra. So, think of plesiosaur centra as Incan wall stones. There are no spaces between either. This compaction between vertebrae greatly restricts movement between individual cervicals and restricts cervical movement overall. Even so, even half a degree per centrum magnified by 76 cervicals can add up (Fig. 1) permitting some movement. Short, L-shaped cervical ribs are fused to each centrum.Their distal processes do not articulate with one another, but hypothetical ligaments extending from anteroposteriorly-oriented distal tips may have done so.

Figure 5. Muraenosaurus cervical sections from Noe et al. 2017 alongside a ghosted diagram of a complete Muraenosaurus neck.

Figure 4. Muraenosaurus cervical sections from Noe et al. 2017 alongside a ghosted diagram of a complete Muraenosaurus neck. The space between centra can be compared to the space between Incan wall stones. In other words: none. That is not shown in the ghosted reconstruction.

Noe, Taylor and Gomez-Perez conclude,
The consistent presence of numerous cervical segments that lack bony stiffening adaptations, however, is also strong evidence that flexibility was an important functional element in plesiosaur necks (Evans 1993), and gives the potential for a considerable range of movement in the living animal (cf. Zarnik 1925–1926).” The authors compare plesiosaurs to stiff-necked tanystropheids (with only 12 cervicals) to emphasize their point. They overlooked the tight articulations of each centrum with its neighbors. 

From a historical perspective, Noe, Taylor and Gomez-Perez report, 
“Previous workers have considered the degree of neck flexibility in plesiosaurs to range from: extreme mobility (Hawkins 1840; Zarnik 1925–1926; Welles 1943; Welles and Bump 1949), including the ability to arch the neck like a swan (Conybeare 1824; Andrews 1910; Brown 1981b); through relative inflexibility (Hutchinson 1897; Williston 1914; North 1933; Shuler 1950; Storrs 1997); to almost complete rigidity (Buckland 1836; Watson 1924, 1951; Cruickshank and Fordyce 2002; Figs. 3, 9); although some of this variation in interpretation may be due to differences between the species studied (Watson 1924, 1951).”

Clearly some of these workers were right and others were wrong.
But which ones? Zoe, Taylor and Gomez-Perez conclude, to their credit, “Overall, the range of movement available to the plesiosaur neck was strictly limited.”

Figure 7. Illustration from Noe, Taylor and Perez-Gomez showing their view of plesiosaur feeding and escape configurations.

Figure 5. Illustration from Noe, Taylor and Perez-Gomez showing their view of plesiosaur feeding and escape configurations. Usually paleo illustrations are more anatomically accurate than this.

Elasmosaurs were morphologically different than anything else in the sea. 
And they became more and more different as time went by (Fig. 2). So, something was working better and better as evolution selected for more extreme neck lengths.

Once again, let’s broaden our scope and look at the environs,
including coeval predators. All of these were robust, fast, streamlined, short-neck predators that swam horizontally preceding an attack from outside in. All of this is the opposite of elasmosaurs who hypothetically loitered below schools of fish unobtrusively rising to slip only their head in from below with minimum turbulence in order to remove fish or squid at leisure from the inside out.

Plesiosaur respiration at the surface
had to take place horizontally due to air pressure constraints. Alternatively, elasmosaurs could have gulped air, then assumed a horizontal or diving orientation to let the air bubble travel back through their long neck back or up to their lungs. With such tiny nostrils, gulping air seems more reasonable than narial inhalation.

Exhalation could have been more leisurely
and might have involved producing a ‘bubble net’ from stale air stored in the long trachea and released through the tiny nares. Extant baleen whales sometimes produce a bubble net to herd fish and plankton as they rise to feed on them. Perhaps elasmosaurs did the same, again based on their vertical orientation.

Fins at all four corners
Noe, Taylor and Gomez-Perez report, “With limbs at the four corners of the body, plesiosaurs could potentially produce vectored thrust from different limbs, to provide fine control of movement in all directions, and around all axes. This is more useful in slow swimming or hovering animals than simple shark-like control fins, which require movement in order to generate a current over the control surfaces.” Exactly. Unfortunately, these authors did not consider plesiosaurs to have a vertical orientation. Instead they focused on the ability of the neck to flex ventrally from a horizontal orientation.

Stomach stones
Noe, Taylor and Gomez-Perez report, “Swimming efficiency was further impaired by the mass of the neck, and the stomach stones commonly preserved in plesiosaurs. This stone ballast was probably needed to establish trim control and longitudinal stability to enable the animal to swim slowly horizontally and to hover, especially when diving in shallow water when the animal was positively buoyant.” The other explanation is that stomach stones helped weight the body below the more buoyant neck (filled with stagnant air), again supporting a vertical orientation when not swimming to other locations.


References
Noe LF, Taylor MA and Gomez-Perez M 2017. An integrated approach to understanding the role of the long neck in plesiosaurs. Acta Palaeontologica Polonica 62 (1): 137–162.

Short-necked azhdarchids? Probably not.

Naish and Witton 2017 bring their insight
to a short, but giant cervical from a Romanian azhdarchid (Fig. 1 inset). They reported, “we discuss a recently discovered giant azhdarchid neck vertebra referable to Hatzegopteryx from the Maastrichtian Sebes Formation of the Transylvanian Basin, Romania. This vertebra, which we consider a cervical VII, is 240 mm long as preserved and almost as wide. Among azhdarchid cervicals, it is remarkable for the thickness of its cortex (46 mm along its ventral wall) and robust proportions.”

Naish and Witton conclude:
“By comparing its dimensions to other giant azhdarchid cervicals and to the more completely known necks of smaller taxa, we argue that Hatzegopteryx had a proportionally short, stocky neck highly resistant to torsion and compression.”

Figure 2. Quetzalcoatlus has a long cervical 7 and a short cervical 8. Naish and Witton consider the Romanian cervical #7, creating a short neck. But see figure 2.

Figure 2. Quetzalcoatlus has a long cervical 7 and a short cervical 8. Naish and Witton consider the Romanian cervical #7, creating a short neck. But see figure 2. The tall neural spine on cervical 8 is speculative and may be absent.

If the Romanian cervical is similar to cervical 7 of Quetzalcoatlus,
(Fig. 1) then the authors’ extrapolation seems reasonable.

Figure 2. Azhdarcho cervicals 7 and 8 are both short, but the anterior cervicals are elongate.

Figure 2. Azhdarcho cervicals 7 and 8 are both short, but the anterior cervicals are elongate. The Romanian cervical may belong to a similar genus, only larger.

However, if similar to the shorter cervical 7 of Azdarcho,
(Fig. 2) then the authors’ extrapolation can only be considered inconclusive. The rest of the cervicals in Azhdarcho are long and slender, matching those of all other clade members. Azhdarcho comes from Uzbekistan, closer to Romania than Quetzalcoatlus (Fig. 1), which comes from Texas.

Naish and Witton suggest,
“This specimen is one of several hinting at greater disparity within Azhdarchidae than previously considered, but is the first to demonstrate such proportional differences within giant taxa.”

Given the anatomy of Azhdarcho,
that conclusion is premature at present. We need to see at least some short anterior cervicals.

Historically, Naish and Witton imagined giant azhdarchids
as world-wide soarers, able to quad launch with folded wings, and terrorizing terrestrial prey like tiny sauropods. All of these fanciful hypotheses have been invalidated, but remain popular with paleoartists.


References
Naish D and Witton MP 2017. Neck biomechanics indicate that giant Transylvanian azhdarchid pterosaurs were short-necked arch predators. PeerJ 5:e2908; DOI 10.7717/peerj.2908

Pre-elasmosaurs out-competed tanystropheids as passive vertical predators

The hyper-elongate neck developed by convergence three times
(Figs. 1, 2) in the known prehistory of marine tetrapods. On land we have giraffes, langobardisaurs and sauropods, but they are not considered here due to their separate terrestrial environs. Based on the similar necks and diets (fish and squid of these three marine tetrapods, perhaps some of the mystery surrounding these taxa can be resolved.

Figure 1. Albertonectes, Tanystropheus and Dinocephalosaurus to scale.

Figure 1. Albertonectes, Tanystropheus and Dinocephalosaurus to scale. With all the other predators assuming a horizontal pose, maybe the vertical neck of these predators in the midst of schools of fish and squid went unnoticed…until it was too late. Maybe those rocks in the belly of the elasmosaur helped keep it anchored.

The three marine taxa with hyper elongate necks
(Fig. 1) are Albertonectes (Elasmosauridae), Tanystropheus (Tritosauria), and Dinocephalosaurus (Tritosauria). We also know of several specimens closely related to each of these taxa, discussed here, here, and here. They all share more than a hyper-elongate neck in common, but that’s the one thing that predominates. They appear to have all been marine vertical predators, passively extending their neck up into schools of prey, essentially unrecognized because they were not horizontal speedsters, like all the other predators out there.

Figure 2. Skulls of Albertonectes, Dinocephalosaurus and two types of Tanystropheus skulls not to scale.

Figure 2. Skulls of Albertonectes, Dinocephalosaurus and two types of Tanystropheus skulls compared, not to scale. Lots of convergence here, it’s plain to see.

Convergent skull traits in vertical feeders:

  1. Small skull
  2. Long procumbent teeth
  3. Large premaxilla
  4. Upward facing eyes
  5. Dorsally displaced nares
  6. Rostrum wider than tall
  7. Internal naris migrated posteriorly
  8. Flat palate

Renesto 2005 along with Renesto and Saller 2018
presented evidence to show that Tanystropheus had a semi-aquatic horizontal lifestyle.

  1. “Tanystropheus was able to lift the body off the substrate when on land,
  2. Tanystropheus lacked adaptations for continuous swimming, either tail-based or limb-based,
  3. Tanystropheus was able to swim for by rowing with symmetrical strokes of the hind limbs.”

But remember,
Renesto and Saller mistakenly considered Tanystropheus a protorosaur and an archosauromorph. It is neither. In the large reptile tree (LRT, 1175 taxa) Tanystropheus nests with Huehuecuetzpalli and pterosaurs, all in the clade Tritosauria, a clade within Lepidosauria.

Renesto and Saller continue:
“The life style of Tanystropheus,the largest and most bizarre of all tanystropheids, remained uncertain since its discovery… In conclusion, Tanystropheus may have had lived in a shore line environment, where the elongate neck, may have been used to cach preys in shallow water by dashing at the prey propelled by hindlimbs, either starting from the shoreline from a resting positionor, in water, eventually after slowly closing the distance. In water, the long neck would have allowed Tanystropheus to conceal its real size while slowly approaching to fish or squid schools by reducing the disturbance caused by body surrounding water, avoiding to be detected by the prey’s lateral line. When close enough, Tanystropheus may have shifted to fast pursuit for the sudden propulsive final phase, with a series of rapid symmetrical strokes of the hind limbs (Fig. 6).”

Yeah, maybe…
but Renesto and Saller just said Tanystropheus was not a good swimmer. So let’s toss out that shift to fast pursuit.

Imagine a passive predator distinct from
all the other predators assuming a horizontal pose. Maybe the vertical neck of all these predators in the midst of schools of fish and squid went unnoticed by them…until it was too late. Maybe it’s as simple as that. No extant taxa can be used by analogy, so we have to look at extinct taxa with similar traits. We looked at Tanystropheus among the crinoids (Fig. 1), and the evolution to that niche earlier here. The convergent Dinocephalosaurus neck strike hypothesis is from Peters, Demes and Krause 2005. The long-necked limbed ancestors of elasmosaurs were morphologically similar and coeval to long-necked limbed tritosaurs in the Middle Triassic (Fig. 5).

Note added on the vertical neck: 
Peters, Demes and Krause 2005 (actually just Peters, in this case, as there were three comments to the original Dinocephalosaurus paper (Li, Rieppel and LaBarbera 2004), now lumped into one reply) suggested that breathing would have been difficult for long-necked underwater taxa due to changes in pressure with increasing depth, but these taxa could swallow air at the surface then lower the neck to allow the air bubble to rise into the lungs. Just a few degrees of declination would do the trick.

Renesto and Saller report:
“The study focused mostly on the post-dorsal sections of the vertebral column, on the pelvis and hind limb.”  Ignoring the neck in Tanystropheus ignores the biggest clue to its niche. Let’s not do that.

Figure x. The Late Triassic world with the tropical San Giorgio area where Tanystropheus is found highlighted.

Figure 3. The Middle Triassic world with the tropical shallow San Giorgio area where Tanystropheus is found highlighted. Warm waters enabled Tanystropheus and other Triassic reptiles  to stay submerged continually.

Another dinocephalosaur
was reconstructed here (Fig. 3). The neck in this specimen is so gracile, it is difficult to imagine it in any active mode, so the vertical passive pose remains as the only viable alternative. These are not active predators.

Figure 1. The new Dinocephalosaurus has traits the holotype does not, like a longer neck with more vertebrae, a robust tail with deep chevrons and a distinct foot morphology with an elongate pedal digit 4.

Figure 4. The new Dinocephalosaurus has traits the holotype does not, like a longer neck with more vertebrae, a robust tail with deep chevrons and a distinct foot morphology with an elongate pedal digit 4.

And finally
Note the long neck of the derived nothosaur/pre-elasmosaur, like Wangosaurus (Middle Triassic), preceded the evolution to flippers found in later vertical feeding elasmosaurs (Fig. 5). Like the the coeval vertical predators tanystropheids (Fig. 1) and dinocephalosaurs (Fig. 4) pre-elasmosaurs like Wangosaurus out-competed these similar tritosaur lepidosaurs, which cannot be found after the Triassic. Clearly pre-elasmosaurs were not such great swimmers when they started, and must have been only marginally better swimmers after their small limbs became small flippers. Given this data, the hypothesis of vertical predation of small squid and fish prey in pre-elasmosaurs and their elasmosaur descendants deserves the opportunity to be falsified.

By contrast, pliosaurs,
like Brachauchenius, with their big flippers and large toothy skulls, were excellent horizontal predators and fast swimmers. This contrast is key to the present hypothesis.

Figure 5. Elasmosaurid origins. The long neck preceded the flippers in this clade of vertical feeders.

Figure 5. Elasmosaurid origins. The long neck preceded the flippers in this clade of vertical feeders.

Additional data:
Albertonectes vanderveldei (Kubo et al. 2012; Upper Campanian, Alberta; TMP 2007.022.0002) is a virtually complete elasmosaur 11.2m in length (the longest of any elasmosaur) lacking only the skull. It had a 7m neck of 76 vertebrae, the most of any vertebrate. Stones in the belly might have kept it anchored. The gizzard in birds is located posteriorly, as seen in this elasmosaur.

Tanystropheus longobardicus (Tanystropheus conspicuus von Meyer 1855,  Tribelesodon longobardicus Bassani 1886,  Tanystropheus longobardicus Peyer 1930) Anisian, Middle Triassic, ~240 mya, ~4.5m in length, was considered a pterosaur before Peyer (1930) established that the long bones were neck bones, not wing bones. Derived from a sister to the the T4822 specimen of MacrocnemusTanystropheus was a sister to the much smaller Tanytrachelos and Langobardisaurus, rather than the convergent Dinocephalosaurus. Warm waters enabled Tanystropheus and other Alpine Triassic reptiles  to stay submerged continually.

Dinocephalosaurus orientalis (Li, Rieppel and LaBarbera 2004) Late Ladinian, Middle Triassic ~228 mya, was orginally considered a marine sister to Tanystropheus with limbs nearly transformed into paddles of similar size. Phylogenetic analysis places it closer to a specimen of MacrocemusT2472. Dinocephalosaurus was not a protorosaur, as originally described. Rather Dinocephalosaurus was a tritosaur lepidosaur The skull was described as crushed, but it was actually quite flat in life with dorsally directed orbits. The ribs were also much wider than deep. Both of these are characters found in bottom dwellers, not free-swimmers. The cervical (25) and dorsal (33) counts are the highest among tanystropheids. The limbs were short but the hands and feet were relatively large, paddle-like and probably webbed.

Figure 6. A squad of squid, food for both tanystropheids and elasmosaurs.

Figure 6. A squad of squid, food for both tanystropheids and elasmosaurs.

References
Bassani F 1886. Sui Fossili e sull’ età degli schisti bituminosi triasici di Besano in Lombardia. Atti della Società Italiana di Scienze Naturali 19:15–72.
Li C, Rieppel O and LaBarbera MC 2004. A Triassic aquatic protorosaur with an extremely long neck. Science 305:1931.
Liu, J. et al. 2017. Live birth in an archosauromorph reptile. Nature Communications 8, 14445 doi: 10.1038/ncomms14445
Peters D, Demes B and Krause DW 2005. Suction feeding in Triassic Protorosaur? Science, 308: 1112-1113.
Kubo T, Mitchell MT and Henderson DM 2012. Albertonectes vanderveldei, a new elasmosaur (Reptilia, Sauropterygia) from the Upper Cretaceous of Alberta. Journal of Vertebrate Paleontology 32 (3): 557-572. DOI:10.1080/02724634.2012.658124.
Li C 2007. A juvenile Tanystropheus sp.(Protoro sauria: Tanystropheidae) from the Middle Triassic of Guizhou, China. Vertebrata PalAsiatica 45(1): 37-42.
Li C, Rieppel O and LaBarbera MC 2004. A Triassic aquatic protorosaur with an extremely long neck. Science 305:1931.
Liu, J. et al. 2017. Live birth in an archosauromorph reptile. Nature Communications 8, 14445 doi: 10.1038/ncomms14445
Lockley MG 2006. Observations on the ichnogenus Gwineddichnium and  wyneddichnium-like footprints and trackways from the Upper Triassic of the Western United States. In: Harris JD, Lucas SG, Spielmann JA, Lockley MG, Milner ARG. & Kirkland JI (Eds) – The Triassic-Jurassic Terrestrial Transition. New Mexico Museum of Natural History Science Bulletin 37: 170-175.
Meyer H von 1847–55. Die saurier des Muschelkalkes mit rücksicht auf die saurier aus Buntem Sanstein und Keuper; pp. 1-167 in Zur fauna der Vorwelt, zweite Abteilung. Frankfurt.
Nosotti S 2007. Tanystropheus longobardicus (Reptilia, Protorosauria: Reinterpretations of the anatomy based on new specimens from the Middle Triassic of Besano (Lombardy, Northern Italy). Memorie della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano, Vol. XXXV – Fascicolo III, pp. 1-88
Peters D, Demes B and Krause DW 2005. Suction feeding in Triassic Protorosaur? Science, 308: 1112-1113.
Peyer B 1931. Tanystropheus longobardicus Bass sp. Die Triasfauna der Tessiner Kalkalpen. Abhandlungen Schweizerische Paläontologie Gesellschaft 50:5-110.
Renesto S 2005. A new specimen Tanystropheus (Reptilia Protorosauria) from the Middle Triassic of Switzerland and the ecology of the genus: Rivista Italiana di Paleontologia e Stratigrafia 111(3): 377-394.
Renesto S and Saller F 2018. Evidences for a semi aquatic life style in the Triassic diapsid reptile Tanystropheus. Rivista Italiana di Paleontologia e Stratigrafia 124(1):23-34.
Rieppel O, Jiang D-Y, Fraser NC, Hao W-C, Motani R, Sun Y-L & Sun ZY 2010. Tanystropheus cf. T. longobardicus from the early Late Triassic of Guizhou Province, southwestern China. Journal of Vertebrate Paleontology 30(4):1082-1089.
Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus(Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-162 plus plates.

wiki/Dinocephalosaurus
wiki/Tanystropheus
https://en.wikipedia.org/wiki/Albertonectes

Several appearances and disappearances of the neck

FIgure 1. Panderichthys has no neck, but closely related Tiktaalki does have a neck.

FIgure 1. Panderichthys has no neck, but closely related Tiktaalki does have a neck.

One of the main differences between fish and tetrapods,
other than the transition from fins to feet, is the origin of the neck. famously in the amphibian-like fish, Tiktaalik (Fig. 2). The proximal outgroup taxon in the large reptile tree (LRT, 1016 taxa), Panderichthys (Fig. 1), does not have a neck. The skull and opercular bones are jammed up against the cleithrum (pectoral girdle) permitting no wiggle room. That wiggle room ultimately comes from the disappearance of those opercular bones.

Figure 1. Tiktaalik had a neck, that small space between its skull and pectoral girdle not seen in more primitive taxa.

Figure 2. Tiktaalik had a neck, that small space between its skull and pectoral girdle is not seen in more primitive taxa, which retain opercular bones, lost in Tiktaalik.

It is noteworthy
that more primitive taxa than Tiktaalik, in the Paratetrapoda, like Pholidogaster and Colosteus (Fig. 3) also lack a neck. The pectoral girdle extends beneath the posterior jaws, as in Osteolepis.

Figure 1. Colosteus relatives according to the LRT. Only Pholidogaster and Colosteus are taxa in common with traditional colosteid lists. Note the lack of a neck in Osteolepis, Pholidogaster and Colosteus.

Figure 3. Colosteus relatives according to the LRT. Only Pholidogaster and Colosteus are taxa in common with traditional colosteid lists. Note the lack of a neck in Osteolepis, Pholidogaster and Colosteus.

The first tetrapod clade,
(Fig. 9) with flat-headed Greererpeton at its base, had a neck, though not much of one. In related taxa like Gerrothorax (Fig. 4), the skull and torso were so wide that a neck would have been useless for lateral movements, but essential to help the skull rise during feeding (famously, like a toilet bowl lid!). More derived taxa in this clade, like Metoposaurus, had a little more neck represented by more space between the skull and pectoral girdle.

Figure 1. Gerrothorax, lacks a supratemporal rim and has laterally extended ribs, similar to those in Greererpeton.

Figure 4. Gerrothorax, has a wide skull and wide torso permitting little to no lateral skull movement, but vertical movement is not impeded.

The second tetrapod clade,
(Fig. 9) with Ossinodus and Acanthostega (Fig. 5) at its base, likewise did not have much of a neck. Perhaps there was less of a neck than in more basal Tiktaalik. This is a small clade with just these two members, so far.

Figure 4. Acanthostega does not have much of a neck.

Figure 5. Acanthostega does not have much of a neck. There is little wiggle room between the skull and pectoral girdle.

The third tetrapod clade,
(Fig. 9) with Pederpes and Crassigyrinus (Fig. 6) at its base likewise had very little wiggle room between the skull and cleithrum. Crassigyrinus had a short neck between its cheeks, so likely was immobile. In this clade derived members, Sclerocephalus and Eryops, document the third appearance of the neck in tetrapods. Even so, it was a very short relatively immobile neck.

Figure 5. Crassigyrinus has little to no neck.

Figure 6. Crassigyrinus has little to no neck. What neck it has is now tucked between its cheeks.

The fourth tetrapod clade
(Fig. 9) with Ichthyostega (Fig. 7) as its base, might have had some wiggle room between the skull and tall cleithrum. Not sure whether the small skull or large skull is correct. Certainly its phylogenetic successor, the reptilomorph Proterogyrinus (Fig. 8), had a substantial neck as did most of its descendants (but see below for notable exceptions).

Figure 6. Not sure which is more correct, but this Ichthyostega data shows little to no wiggle room for the larger skull, more for the smaller skull.

Figure 7. Not sure which is more correct, but this Ichthyostega data shows little to no wiggle room for the larger skull, much more for the smaller skull.

Basal reptilomorpha
and in the clade Seymouriamorpha, like Seymouria, and in the LRT leads to both Reptilia and Lepospondyli, had an increasingly mobile neck.

Figure 6. Proterogyrinus had a substantial neck.

Figure 8. Proterogyrinus had a substantial neck apart from the pectoral girdle.

The number of cervicals
remains low (under 4) in basal lepospondyls, and sometimes that number decreases to one. An exception, Eocaecilia, had 5 elongate cervicals. Basal amniotes, like Gephyrostegus, had six flexible cervicals.

Figure 4. Subset of the LRT with the addition of Lethiscus as a sister to Oestocephalus, far from the transition between fins and feet. Here the microsaurs are not derived from basal reptiles

Figure 9. Subset of the LRT with the addition of Lethiscus as a sister to Oestocephalus, far from the transition between fins and feet. Here the microsaurs are not derived from basal reptiles

Notable reversals, back to lacking a neck, include:

  1. Rana, the frog.
  2. Cacops the basal lepospondyl
  3. Mixosaurus, the ichthyosaur and
  4. Eubaelana, the right whale, with short fused cervicals
Figure 5. Eubalaena australis, the Southern right whale nests with Cetotherium in the LRT.

Figure 10. Eubalaena australis, the Southern right whale nests with Cetotherium in the LRT. Here the cereals are fused and immobile.

 

 

Hatzegopteryx: one error in cervical identification leads to trouble

Azhdarchid pterosaurs
as we learned earlier, first achieved their slender proportions in small, sand-piper-like taxa similar to n44 and n42 during the Late Jurassic (Fig. 1). Coeval and later taxa grew larger, some attaining stork-like and then giraffe-like sizes while maintaining their slender proportions.

Azhdarchids and Obama

Figure 1. Click to enlarge. Here’s the 6 foot 1 inch former President of the USA alongside several azhdarchids and their predecessors. Most were knee high. The earliest examples were cuff high. The tallest was twice as tall as a human male.

Extant storks are stalkers
whether wading or on firmer substrates. That analogy brings us, once again, to the Naish and Witton 2017 concept of azhdarchids as terrestrial stalkers. They revisit the subject  a third time (after Witton and Naish  2008. 2015), but now freshly armed with the evidence of a large short cervical from Hatzegopteryx, a giant pterosaur from Romania.

The big question is: which cervical is it?

In giant derived azhdarchids.
like Quetzalcoatlus and Hatzegopteryx, half the cervicals (1-3 and 8) are not elongate and the other half (4-7) are elongate.

Unfortunately and earlier
Witton and Naish 2008 mistakenly numbered the cervicals of Phosphatodraco 4-9, when they should have labeled them 3-8 (Fig. 2). They saw that neural spine on #7, which they thought was #8.

Cervical number 8 is always short in azhdarchids
and if correctly identified would have allowed the possibility that Hatzegopteryx had a typical azhdarchid neck. Cervical number 5 is always the longest in giant azhdarchids and Phospatodraco, which gives workers a starting point if the bones are scattered or incomplete at the ends.

But Naish and Witton took it the other way
and with their misidentification of a wide cervical number 7 they imagined a wide cervical series for Hatzegopteryx. And with that they thought they had more evidence for terrestrial stalking instead of aquatic wading, as practiced by all ancestors back to the Late Jurassic. I’m not saying azhdarchids didn’t pick up a few tidbits on land. I am saying they and all their ancestors were built like living sandpipers, stilts and herons, which find their diet in the shallows.

Figure 2. Black images are from Naish and Witton 2017. Cervical series is from Witton and Naish 2008. Purple and red are added here. Improper cervical identity in 2008 led to bigger problems in 2017.

Figure 2. Black images are from Naish and Witton 2017. Cervical series is from Witton and Naish 2008. Purple and red are added here. Improper cervical identity in 2008 led to bigger problems in 2017 where the authors switched real for imaginary in their graphic, which makes it look like they had more data than they really did. BTW, none of these belly-flopping pterosaurs could have taken off in this fashion.

As much as Naish and Witton write about azhdarchids,
they should not be making basic mistakes over and over again. Not only do they misidentify a cervical, they illustrate their pterosaurs doing belly flops in a purported take-off configuration that has no chance of succeeding. See here, here and here for details.) And finally they should no longer consider that pterosaurs had nine cervicals. That goes back to S. Christopher Bennett’s PhD thesis in which he considered vertebrae number 9 to be a cervical since it did not contact the sternum. Even so, it bore long ribs and was located inside the thorax.

Pictured here
(Fig. 3) is the Hatzegopteryx cervical in question. Compared to both Phosphatodraco (Fig. 2) and Quetzalcoatlus sp. (Fig. 3) this is cervical #8, the short one, not cervical #7, the long one.

Figure 3. Hatzegopteryx cervical. If it is number 7, as Naish and Witton suggest, then it is very short and likely would be part of a very short neck. But if it is number 8, then the proportions are typical for azhdarchids. This is where Occam's Razor might have been useful.

Figure 3. Hatzegopteryx cervical. If it is number 7, as Naish and Witton suggest, then it is very short and likely would be part of a very short neck. But if it is number 8, then the proportions are typical for azhdarchids. This is where Occam’s Razor might have been useful.

Some azhdarchids and their kin
have a tall neural spine only on cervical #8. Quetzalcoatlus is in this clade. Some, like Zhejiangopterus and Chaoyangopterus, have no tall neural spines. That’s also the case with the tiny basalmost clade members. By contrast, the flightless pterosaur, JME-Sos 2428 has a tall neural spine on cervicals 6-8, which makes me wonder if Phosphatodraco (Fig. 2) is a sister to it, given the present limited amount of data.

The Domino Effect
When Naish and Witton decided that Hatzegopteryx cervical #8 was #7, that mistake unleashed the possibility that they had discovered the first “short neck” azhdarchid! They must have been excited.

What Naish and Witton did not show you…
In lateral view, the Hatzegopteryx cervicals Naish and Witton illustrated actually look normal for an azhdarchid, but in dorsal view the omitted cervicals would have to have been twice as wide as typical and no longer cylinders (Fig. 2). So the “short” neck was really a “wide flat” neck, but that does not have the same headline cache. Such a major departure from the azhdarchid bauplan should have caused Naish and Witton to reconsider that their ‘discovery’ was actually a simple error in identification, now percolating online for the last 8 years.  Hope this helps quell the notion!

References
Naish D and Witton MP 2017. Neck biomechanics indicate that giant Transylvanian azhdarchid pterosaurs were short-necked predators. PeerJ 5:e2908; DOI 10.7717/peerj.2908
Witton MP and Naish D 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLOS ONE 3:e2271 DOI 10.1371/journal.pone.0002271.
Witton MP and Naish D 2015. Azhdarchid pterosaurs: water-trawling pelican mimics or terrestrial stalkers? Acta Palaeontologica Polonica 60:651660 DOI 10.4202/app.00005.2013.

Brian Switek blog
wiki/Hatzegopteryx

The Search for Epipophyses Beyond the Dinosauria

This post has been modified from the original to correct inaccuracies.

Figure 1. Herrerasaurus epipophyses (epi, in pink) on a cervical in three views. Postzygopophyses (poz, bone articulations) in yellow.

Figure 1. Herrerasaurus epipophyses (epi, in pink) on a cervical in three views. Postzygopophyses (poz, bone articulations) in yellow.

Wiki reports, “The epipophyses are bony projections of the cervical vertebrae found in dinosaurs (Fig. 1 in pink) and some fossil basal birds. The presence of epipophyses is a synapomorphy (distinguishing feature) of the group Dinosauria. Epipophyses (Fig. 1) were present in the basalmost dinosaurs, but absent in closely related ancestors of this group like Marasuchus and Silesaurus (Fig. 2). The immediate ancestor of the Dinosauria, Gracilisuchus, did not have epipophyses.

Silesaurus cervicals. Note the lack of epipophyses.

Figure 2. Silesaurus cervicals. Note the lack of epipophyses.

Then I heard pterosaurs also had epipophyses. However, I found that only some derived pterosaurs have them (Figs 3, 4). Since dinosaurs and pterosaurs are on opposite sides of the large reptile tree, I wondered if epipophyses were more widespread than the Wiki author asserted. So I looked around.

Epipophyses are not present on these pterosaurs.

Figure 3. Epipophyses are not present on these pterosaurs.

Tiny epipophyses on the third cervical of Anhanguera.

Figure 4. Tiny epipophyses (in pink) on the third cervical of the ornithocheirid pterosaurs Anhanguera.

Epipophyses on Columbyua, the common loon and on Macrocnemus, but not Cosesaurus.

Figure 5. Epipophyses on Colymbus, the common loon and on Macrocnemus, but not Cosesaurus.

Evidently, they are more widespread

Here’s what I found (with some help from M. Mortimer, see below). Epipophyses are present in Colymbus, the loon (Fig. 4, itself a bird and therefore a dinosaur), and in Anhanguera (Fig. 4, a pterosaur), Tanystropheus (Fig. 6) and Macrocnemus (Fig. 5). These last three now nest with lizards. Epipophyses are not found in Cosesaurus (Fig. 5) or most pterosaurs (Fig. 3). Other large pterosaurs, like Pteranodon and Quetzalcoatlus, do not have epipophyses.

Epipophyses on Tanystropheus, a relative to Cosesaurus and pterosaurs.

Figure 6. Epipophyses on Tanystropheus, a relative to Cosesaurus and pterosaurs.

Epipophyses strengthen the neck, but are not always associated with a long neck (Fig. 3). Perhaps epipophyses are more widespread than this. For now, it’s enough to know what epipophyses are and that epipophyses are indeed present beyond the Dinosauria. According to Wiki, epipophyses disappear in some dinosaurs. All the more reason that this trait should be scored on a genus-by-genus basis.