The many faces of Tanystropheus

Added September 21, 2020:
Think about a bubble net, as in humpback whales, coming form the long, dead=air storage vessel that is that elongate trachea. That long neck rotating like an inverted cone to surround confused fish just above the jaws.

Tanystropheus is well known
as the sometimes giant reptile with the hyper-elongate neck (Figs. 1, 2). Several specimens are known, all by letters in the alphabet based on Wild (1973). Few specimens have skulls.

The smaller Tanystropheus specimens (Fig. 1) have multicusp posterior teeth, and some workers consider these juveniles that change their diet and teeth as they grow. Others, including yours truly, think these are two different species, if not different genera. Remember, guyz and galz, you don’t get giant species without first going through the medium and large size ranges. We learned this earlier with Pteranodon.

Wild’s (1973) reconstruction of the skull was taken as gospel for a good long time. Then Nosotti (2007) came along and rebuilt the small skull in convincing fashion. Here we’ll take a look at a skull from a small individual (Fig. 1, Exemplar a) and compare it to two skulls from the larger forms (Fig. 2, Exemplars i and q). Then you can decide if the differences are ontogenetic or phylogenetic.

Tanystropheus exemplar a.

Figure 1. Tanystropheus exemplar a.

Exemplar a has a low rostrum and large orbit. The frontals extend over the orbits like brow ridges. The nasals are not visible on any articulated skulls, and displaced samples can be placed on the skull two different ways. The ascending process of the premaxilla is also a big question mark. It could be present or absent. The pineal opening is not large in any sister taxa, so it redevelops here. The posterior skull leans down, which, by analogy with basal synapsids indicates a bit of posterior pull on the mandible, as if Exemplar a was tugging at its meals.

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

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

Among the giant specimens…

Exemplar i is the skull that Wild (1973) used for his ‘adult’ specimen. Like  Exemplar a, the frontals are wide, the nasals are unknown and the ascending process of the premaxilla is apparently gone. This creates quite a large confluent set of nares dorsally oriented. The posterior skull does not descend posteriorly. Only a few teeth are preserved and in dorsal view the rostrum is wide and rather flat, like a hat brim. One gets the impression that a great circle of procumbent teeth emanated from these jaws because the premaxilla appear to be quite flat in situ with no indication of any depth.

Exemplar q is lower, longer and had a reduced pterygoid and vomers. Here the nares are also very large, but divided by a slender and fragile ascending process of the premaxilla (pretty much busted up in situ). Rather than wide and flat, this rostrum is more traditionally box-like with ventrally oriented teeth. The pterygoid is greatly reduced and so are the vomers. The nasals are preserved here only as posterior rims to the large nares. The brow ridges are gone here, so Exemplar q could look up without moving its head.

The appearance of those giant nares on these tiny skulls links to that hyper-elongate neck and within, a hyper-elongate trachea that needs to be flushed of CO2 and filled with O2 every so often.

So the skulls of the big taxa are different.
It might be worthwhile to see how the post-crania also differs. There’s a PhD project waiting for someone out there, probably in Europe, where the fossils are. Or wait a few weekends and I’ll probably get around to it.

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 2007. A juvenile Tanystropheus sp.(Protoro sauria: Tanystropheidae) from the Middle Triassic of Guizhou, China. Vertebrata PalAsiatica 45(1): 37-42.
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
Peyer B 1931. Tanystropheus longobardicus Bass sp. Die Triasfauna der Tessiner Kalkalpen. Abhandlungen Schweizerische Paläontologie Gesellschaft 50:5-110.
Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus (Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-16.

wiki/Tanystropheus

Tribelesodon/Tanystropheus: rough draft

Before the fossil named “Tribelesodon(Fig. 1) was identified as a small Tanystropheus with three-cusped teeth (Peyer 1931) it was considered a type of pterosaur with three-cusped teeth (Bassani 1886, Arthaber 1921, Von Nopcsa 1923). So it’s famous.

Figure 1. Tanystropheus (Tribelesodon specimen) from Wellnhofer 1991, part and counterpart and rough tracing.

Figure 1. Tanystropheus (Tribelesodon specimen) from Wellnhofer 1991, part, counterpart and very rough tracing.

The part and counterpart fossil (Fig. 1) of Tribelesodon was housed in Italy’s Museo di Storia Naturale di Milano before it was destroyed by Allied bombs during World War II. Thankfully, Wellnhofer (1991) provided small images of the fossil.

Figure 2. Rough comparisons of the Tribelesodon specimen assigned to Tanystropheus (Peyer 1931) compared to more complete specimens from Europe and China.

Figure 2. Rough comparisons of the Tribelesodon specimen assigned to Tanystropheus (Peyer 1931) compared to more complete specimens from Europe (MSNM BES SC 1018) and China (IVPP V 14472). The Tribelesodon specimen appears to have had a larger skull and more gracile postcrania, but otherwise closely comparable in size to the IVPP specimen.

Here, very roughly, I trace (Fig. 1) and uncoil the neck (Fig. 2) using DGS and compare it to more complete specimens from Europe and China. The Tribelesodon specimen appears to have had a larger skull and more gracile postcrania, but otherwise closely compares in size to the IVPP specimen. I’ll readily admit some bones may be misidentified and vaguely indicated, especially around the pelvis. The details, in this case, are not that important. Overall, it’s pretty obvious what we have here.

Earlier we looked at several of the largest specimens of Tanystropheus, the evolution of Tanystropheus and other topics related to this genus.

Thanks to Tracy Ford for providing me a scale bar on this specimen.

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 2007. A juvenile Tanystropheus sp.(Protoro sauria: Tanystropheidae) from the Middle Triassic of Guizhou, China. Vertebrata PalAsiatica 45(1): 37-42.
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
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 of 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.
Wellnhofer P 1991. The Illustrated Encyclopedia of Pterosaurs. Salamander Books Ltd., London. 192 pp.
Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus(Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-16.

wiki/Tanystropheus

Giant Tanystropheus to scale, and a tribute to Rupert Wild

Figure 1. Click to enlarge. Four large Tanystropheus specimens in situ and reconstructed. The man silhouette  is 6 feet (1.8m) tall.

Figure 1. Click to enlarge. Four large Tanystropheus specimens in situ and roughly reconstructed. The human silhouette is 6 feet (1.8m) tall. In situ images from Wild 1974. Note the presence and absence of epipubic bones along with the variation in skull size.

Tanystropheus (Fig. 1, Middle Triassic, Europe, von Meyer 1852) was discovered in the 19th century, but not fully realized for what it was until Peyer 1931. One early specimen, named Tribelesodon, was mistaken for a pterosaur (Basani 1886, Arthaber 1921, Von Nopcsa 1923). The long neck bones were mistakenly compared to wing bones. The foot, with its long p5.1 digit, were indeed very pterosaurian in general morphology. So the taxonomic mistake had some basis.

Lesson learned here:
respected scientists can make mistakes. And these mistakes can become traditions until falsified. A reconstruction might have helped.

Peyer’s contribution
New complete skeletons of Tanystropheus described by Peyer (1931) solved the basic problem by showing the hyper-elongate bones actually belonged between the skull and torso.

Wild’s contribution
In 1974 Rupert Wild reviewed all the available material (27 specimens) of T. langobardicus. A few are pictured above (Fig. 1). Before the advent of phylogenetic analysis, Wild had the insight to label them Reptilia > Lepidosauria > Squamata > Lacertilia > Tanysitrachelida > Tanystropheidae. This is largely confirmed by the present large reptile tree. (The term “Lacertilia” includes all lizards, but not snakes, so it is a paraphyletic taxon in the large reptile tree. The term “Tanysitrachelida” (Peyer 1931) is no longer in use. Tanystropheidae includes other long-necked reptiles, such as  Langobardisaurus, Pteromimus, Tanytrachelos and Amotosaurus, all very much smaller taxa.)

To his credit,
Wild (1978) also was among the first to promote the idea that pterosaurs were not archosaurs, but something else along the lines of an eosuchian, a term little used today. Back then an Eosuchian was commonly considered a basal diapsid, like Youngina, a genus then considered close to the ancestry of both lepidosaurs and archosaurs. Now, thanks to the large reptile tree, we know that lepidosaurs and archosaurs are not related, except at a very basal reptile level. We also know that diapsids are diphyletic, having two origins. Wild’s heretical break with tradition is to be applauded. At the time closer relatives to pterosaurs, like Langobardisaurus, Cosesaurus, Sharovipteryx and Longisquama were either unknown or just becoming known.

Others
(Carroll 1989, etc.) placed Tanystropheus outside the Archosauriformes along with rhynchosaurs, which makes absolutely no sense. Still others (Renesto 2005 following tradition) placed Tanystropheus within the Protorosauria, which makes more sense, but, unfortunately, this is by untested tradition only.

Phylogenetic testing using more taxa in the large reptile tree clarifies relationships. Tanystropheidae nest between Huehuecuetzpalli Macrocnemus and Cosesaurus within the Tritosauria, outside of the Squamata.

Despite what Wikipedia tells you, phylogenetic analysis recovers Dinocephalosaurus as a convergent form derived from Macrocnemus, not directly related to Tanystropheus despite   the roughly similar appearance and size.

Earlier we looked at several solutions to the niche and posture of Tanystropheus. Here you can see the ancestry and sisters of Tanystropheus.

Here (fig. 1) we can see that some large Tanystropheus specimens had a larger skull. Others had a smaller skull. Some had epipubic bones. Others did not. More precision in creating the reconstructions might someday reveal other differences not readily visible in these roadkill fossils.

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 2007. A juvenile Tanystropheus sp.(Protoro sauria: Tanystropheidae) from the Middle Triassic of Guizhou, China. Vertebrata PalAsiatica 45(1): 37-42.
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
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 of 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.
Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus(Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-16.
Wild R 1978. Die Flugsaurier (Reptilia, Pterosauria) aus der Oberen Trias von Cene bei Bergamo, Italien. Bolletino della Societa Paleontologica Italiana 17(2): 176–256.

wiki/Tanystropheus

Tanystropheidae in the sw usa – svp abstracts 2013

From the abstract
Pritchard et al. 2013 wrote: “Tanystropheids are a clade of long-necked archosauromorphs whose remains are largely restricted to marine deposits from the Triassic of Europe and Asia and almost entirely known from two-dimensionally crushed skeletons. Thus far, the occurrences of Tanytrachelos along the East Coast of the United States represent the westernmost confirmed record of tanystropheids, although unconfirmed isolated fragments have been referred tentatively to the group from localities in western North America.

“A large sample of well-preserved, three-dimensional tanystropheid fossils from the Hayden Quarry in the Upper Triassic Chinle Formation of New Mexico provides new insight into the anatomy, phylogeny, and paleoecology of Tanystropheidae. A newly constructed phylogenetic analysis of 200 characters and 45 diapsids, early archosauromorphs, and archosauriforms recovers a novel topology for basal Archosauromorpha. Tanystropheidae forms the sister taxon of a clade including Trilophosaurus, Prolacerta, and Archosauriformes. The analysis also recovers a novel subclade of small tanystropheids including Langobardisaurus and Tanytrachelos. Numerous apomorphies, including dorsoventrally flattened cervical centra and a number of tarsal characters, indicate that the Hayden Quarry tanystropheid materials belong to this subclade. Protorosaurus is recovered as the earliest diverging archosauromorph, outside of Tanystropheidae, and Prolacerta nests as the sister taxon to Archosauriformes.

“These results support the hypothesis that a long necked “protorosaur” bauplan was ancestral for archosauromorphs. Tanystropheid apomorphies identified in this analysis were subsequently used to recognize additional Norian-aged fossils from other sites in New Mexico, Arizona, and Texas. Some of these fossils had previously been attributed to drepanosaurs. The estimated body size range of western tanystropheids based on comparison with Tanytrachelos (~0.3 meters–2.0 meters) indicates that the group was a taxonomically and ecologically diverse component of western North American ecosystems. The presence of tanystropheids throughout western North America, a region that was only seasonally wet during the Norian and Rhaetian suggests that tanystropheids could adapt to a far wider range of habitats than previous records indicate.”

First of all
It’s great to see that little tanystropheids made it to SW America, along with those desert drepanosaurids.

Tanystropheus and kin going back to Huehuecuetzpalli.

Figure 1. Tanystropheus and kin going back to Huehuecuetzpalli. Apparently only forms close to Langobardisaurus and Tanytrachelos were discovered at the Hayden Quarry.

Second of all
This presumption of an archosauromorph nesting of lepidosaurs has to stop! Pritchard et al. are beating a dead horse. A larger spectrum of reptiles reveals that tanystropheids, many with ossified sterna, by the way, are lepidosaurs. This can be tested simply by including taxa, nor excluding them.

Third of all
A small langobardisaurid – tanystropheid has already been discovered in the SW USA. It is called Pteromimus. And perhaps the cervicals of Protoavis, too.

Fourth of all
We know of large Rotodactylus tracks in the SW USA that could only have been made by large relatives of Cosesaurus, to wit: tanystropheids.

To their credit
Protorosaurus and Prolacerta do indeed belong at the base of the Archosauriforms. They have long necks by convergence with tanystropheids.

However
These results do indeed support the hypothesis that a long necked “protorosaur” bauplan was ancestral for archosauromorphs. But I hope they’re not excluding the real sister taxa, like Youngina and Thadeosaurus. And bizarre bauplans, like tanystropheids, are almost always terminal, not ancestral.

References
Pritchard A, Nesbitt S, Turner A, Irmis R Smith N 2013.
Morphology and systematics of the reptile clade Tanystropheidae: implications for Late Triassic biogeography and early archosauromorph evolution. Journal of Vertebrate Paleontology abstracts 2013.

Fuyuansaurus – a Baby Tanystropheid or a Mother?

A tiny new tanystropheid was recently described by Fraser et al. (2013). Complete and articulated, but unfortunately too big for its slab, despite its tiny size, the holotype fossil of  Fuyuansaurus lacks a tail and limbs, though undoubtedly limbs were present in vivo (phylogenetic bracketing).

Figure 1. Fuyuansaurus in situ and close to full scale. Unfortunately this tiny tanystropheid is too large for its tinier slab and so lacks legs and a tail.

Figure 1. Fuyuansaurus in situ and close to full scale. Unfortunately this tiny tanystropheid is too large for its even tinier slab and so legs and a tail extend off the slab. If your screen resolution is 72pdi, the upper image is full scale. The light blue structure is a possible egg and the red structure is a possible pubis more like that of sister taxa. There is a mass of soft tissue preservation from the torso covering the posterior nasals, too. The orange structure in the egg may be a displaced hemal arch (chevron).

It always helps when a reconstruction is made,
in this case to literally unwind the specimen.

Figure 2. Click to enlarge. Reconstruction of Fuyuanasaurus. Fraser et al. identified a strange circular object as the pubis, but no sister taxa have a circular pubis. Here it is tentatively ID'd as an egg because a standard pubis is found  nearby.

Figure 2. Click to enlarge. Reconstruction of Fuyuanasaurus slightly smaller than full scale. Yes=, it’s that tiny. Fraser et al. identified a strange circular object as the pubis, but no sister taxa have a circular pubis. Here it is tentatively ID’d as an egg/embryo because a standard pubis is found nearby and another soft tissue mass is also preserved anteriorly. Oddly, cervical #8 is shorter than #7 or #9. Orange in the cheek area is not the coronoid, but a portion of the pterygoid. Purple on the upper jaw margin below the cheek is not the dentary but the surangular.

Phylogenetic analysis nests Fuyuansaurus between the small Tanystropheus with multi-cusped teeth and the large one with simple stabbers. So does that make this another Tanystropheus species? Or do we need to separate the two Tanys generically? Depends if you’re a lumper or splitter. Fraser et al. did not publish their analysis if one was made.

That strange circular “pubis”.
Fraser et al. identified a round structure with ridge-like process terminating in a hollow bone end as a pubis, but noted that it was unlike the pubis of Tanystropheus or Macrocnemus. No kidding… Autapomorphies like this often have a different reality, as we learned earlier. I wonder if the flat round object was an egg because I found a regular strut-like pubis nearby on the inner mandible and the narrow structure that penetrates the soft ellipse could have been a chevron or a lumbar rib. So the possible tiny juvenile could actually be a possible tiny mother. And that ridge along the rim of the egg could be an embryo vertebral series. Hard to tell with available materials, but an interesting thought nevertheless that could pan out with higher resolution.

References
Fraser NC, Rieppel O and Chun L 2013. A long-snouted protorosaur from the Middle Triassic of southern China, Journal of Vertebrate Paleontology, 33:(5):1120-1126.

Blood pressure in an elevated Tanystropheus

Yesterday we looked at the possibility of underwater leaping in Tanystropheus for snatching prey and, with a little momentum, for reaching the surface for a breath.

Just like a giraffe or an upright sauropod
Tanystropheus had to have had a specialized circulatory system and a large heart in order to raise its neck. And also like a giraffe, Tanystropheus probably another sort of system to keep blood from pooling in its legs and tail whenever the neck was raised. This post was inspired by a recent one on sauropods here at PHENOMENA, a science salon hosted by National Geographic Magazine.

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.

That vertical pipe of a neck would have elevated the head nearly eight feet (250 cm) above the heart in the largest Tanystropheus specimens. That’s longer than the neck height of a giraffe, but far shorter than that of a large sauropod. In giraffes the heart rate is high, up to 170 bpm. We can imagine Tanystropheus might have also had an elevated heart rate, especially for a large lizard. What does this mean? Well, phylogenetically Tanystropheus was surrounded by bipeds, some of them, the fenestrasaurs, were speedy. Some of them, the drepanosaurs, were slow.

The blood pressure of a giraffe is the highest of all animals, reaching about 300 over 200 mm Hg to pump blood up a neck seven feet long to reach its brain. The blood pressure of Tanystropheus might have been a little higher.

Perhaps related – or not
If Tanystropheus fed underwater, the trachea might have been valved in order to keep an air bubble in the lungs and restricting its rise up the windpipe whenever submerged under at least eight feet of water pressure. Likewise the blood vessels might have been similarly valved to keep blood in the “upper stories.”

Few animals are comparable to a Tanystropheus and fewer of them are alive today. All hypotheses about soft tissue can only be considered guesses.

Whatever the case… not bad for a lizard.

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
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 2007. A juvenile Tanystropheus sp.(Protoro sauria: Tanystropheidae) from the Middle Triassic of Guizhou, China. Vertebrata PalAsiatica 45(1): 37-42.
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
Peyer B 1931. Tanystropheus longobardicus Bass sp. Die Triasfauna der Tessiner Kalkalpen. Abhandlungen Schweizerische Paläontologie Gesellschaft 50:5-110.
Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus(Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-16.

wiki/Tanystropheus

Giraffe circulation pdf

Underwater Leaping in Tanystropheus

Added September 21, 2020:
Think about a bubble net, as in humpback whales, coming form the long, dead=air storage vessel that is that elongate trachea. That long neck rotating like an inverted cone to surround confused fish just above the jaws.

Earlier we looked at an underwater bipedal configuration for Tanystropheus. Such a pose would have solved all sorts of neck and balance problems. Here (Fig. 1) is a proposal for using the epipubic bones as caudofemoralis anchors to increase vertical thrust in that environment. Thrust would be used to snare prey or reach the surface for air.

Basically the illustration (Fig. 1) says it all.
Epipubic bones on the large Tanystropheus could have anchored more powerful caudofemoralis muscles to provide more thrust during vertical strikes and trips to the surface. Of course, momentum would have taken Tanystropheus further than shown here.

What were these bones?
Odd chevrons? That’s the best guess so far. Otherwise in close kin there were no large chevrons  and the caudal transverse processes did not extend more than ten caudals back. So, when large thrusters were needed, they grew in this giant in new ways, whichever way helped the most.

Tanystropheus in a vertical strike powered by the enlarged caudofemoralis anchored by the so-called epipubic bones.

Figure 1. Tanystropheus in a vertical strike powered by the enlarged caudofemoralis (in red) anchored by the so-called epipubic bones, which may instead by enlarged and modified chevrons or neomorphs. This push could have been followed by a vertical leap/drift, whether to head to the surface or snatch unwary prey.

Just another crazy thought…

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
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 2007. A juvenile Tanystropheus sp.(Protoro sauria: Tanystropheidae) from the Middle Triassic of Guizhou, China. Vertebrata PalAsiatica 45(1): 37-42.
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
Peyer B 1931. Tanystropheus longobardicus Bass sp. Die Triasfauna der Tessiner Kalkalpen. Abhandlungen Schweizerische Paläontologie Gesellschaft 50:5-110.
Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus(Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-16.

wiki/Tanystropheus

Hypothetical Tanystropheus Egg

Here’s how you paint yourself into a corner…
Huehuecuetzpalli and several pterosaur juveniles and embryos demonstrate that the tritosaurian lizards matured isometrically. In other words, just before hatching, tritosaurs had the proportions of adults. Among pterosaurs we’ve seen this in a juvenile Pteranodon, a juvenile Zhejiangopterus, a juvenile Tapejara, a juvenile Tupuxuara, the IVPP embryo, the JZMP embryo and Pterodaustro.

Now the question is…
If present in the giant, hyper-long-necked Tanystropheus, how in heck would you be able to fit that long neck inside an eggshell?

Juvenile?
Wild (1973) suggested that the smaller 4′ Tanystropheus with several tooth cusps was a juvenile of the 20′ giant with giant conical teeth, but at the time isometric growth had not been established for the Tritosauria. Now these two appear to be distinct species. Even if the smaller specimen is a juvenile, it still has an incredibly long neck, still difficult to fit inside an eggshell.

So, here we put the hypothesis to the test
(Prior to discovering Tanystropheus egg fossils, of course) let’s stuff Tanystropheus into an elliptical egg shape (Fig. 1).

A hypothetical Tanystropheus egg

Figure 1. A hypothetical Tanystropheus egg with an isometrically reduced adult reconfigured into an elliptical shape. No actual egg is known for Tanystropheus. Softer bones likely enabled the looser articulations here, particularly in the neck. Here the hyperelongated neck wraps around the body twice the long way. In the adult stiffening of the cervical ribs and the bony articulations of the cervicals would have prevented this sort of contortion. 

Other than a few very angled neck vertebrae, Tanystropheus fits okay. Are these angles too extreme? Did Tanystropheus embryos have shorter cervicals? We don’t know.

The Eggshell
As in pterosaurs the eggshell was likely an extremely thin leathery surface, more like a pillow case, not a hard ellipse, like a chicken egg. As in other tetrapod embryos, the bones and their articulations with each other were likely much softer and more flexible than in the adult, enabling this strange configuration, adopted only during the last few weeks prior to hatching as the embryo reached hatchling size.

By Land or By Sea?
Earlier we looked at a new hypothesis for vertical feeding in Tanystropheus based on stomach contents, its long neck and the crinoid-filled environment of Triassic seas. Whether Tanystropheus laid its eggs on land or in water may be immaterial if they, like pterosaurs and many other lizards, retained eggs within the mother until just prior to hatching. In that case the egg shell was more like a placenta, essentially producing a live birth. In that case, let’s look for babies near the pelvic region in future fossils.

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
Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus(Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-16.

wiki/Tanystropheus

Flipping the Nasal on Tanystropheus

Dr. Stefania Nosotti (2007) published an excellent and well-illustrated report on several smaller Tanystropheus specimens. Unfortunately the skulls of the articulated specimens were preserved in ventrolateral view obscuring the dorsal view. Several other disarticulated specimens helped fill the gaps.

Tanystropheus exemplar a

Figure 1. Tanystropheus exemplar a skulls demonstrating different interpretations of the nasal bone. The original interpretation above. A revised interpretation below.

Original Reconstruction
Nosotti (2007, Fig. 1) reconstructed the nasals in Tanystropheus with a long common median border beginning at mid naris and expanding laterally beyond the naris. Unfortunately this configuration does not match that of sister taxa (most notably the large Tanystropheus) in which a long premaxilla ascending process separates the nares, extends far beyond them and the nasals laterally border the nares and decrease in width posteriorly. By merely flipping the nasal reconstructed by Nosotti (2007) and adding a slender ascending process  (a fragile bone prone to crushing and breakage) to the premaxilla, a match is made to sister taxa.

Tanystropheus exemplar a.

Figure 2. Tanystropheus exemplar "A" overall. Click for more info.

There’s also the Premaxilla
The premaxilla doesn’t rise along the lateral rim of the naris in sister taxa like exemplar “K” (fig. 3). The rising ascending process goes back to Huehuecuetzpalli.

These exercises demonstrate the need to compare specimens to sister taxa. If autapomorphies are found, then perhaps the autapomorphies need a second look, and perhaps a revised reconstruction more in line with sister taxa – if possible and valid.

Peters (2000) made similar mistakes in Cosesaurus in which I interpreted autapomorphic elements in the pectoral and pelvic girdles that had more synapomorphic distributions.

Figure 3. The skull of the large Tanystropheus, exemplar "K". Premaxilla and nasal highlighted.

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
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 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.

Tanystropheus Feet: Keys to Speciation

The Traditional View
Wild (1978) established the concept that the small, multi-cusp toothed specimens attributed to Tanystropheus were juveniles of the larger forms without multi-cusped teeth. This would involve morphological changes during ontogenetic growth.

The question is, why wasn’t phylogenetic evolution (speciation) offered as an alternative?

The Heretical View
Earlier I blogged that the differences were too many to support an ontogenetic growth series between the smaller Tanystropheus specimens and the larger ones. Today we’ll look at the feet and you can decide whether or not such changes can be attributed to ontogeny or are better explained as a phylogenetic change attributed to evolution. Of course the split would have occurred earlier and the two species would have been adapted to distinct niches based on size and tooth morphology.

Tanystropheus feet with morphological changes noted.

Figure 1. Tanystropheus feet with morphological changes noted. Click for more info.

As in Pterosaurs
Peters (2011) was able to speciate various specimens attributed to Pterodactylus, Pteranodon, Rhamphorhynchus, Germanodactylus and other pterosaurs by looking only at  the variation in the foot morphologies. The same process is present here. If these two Tanystropheus pedes represent younger and older variations of the same species, why do the distinct changes that appear in the jaws (distinct teeth, for instance) extend to the feet?

This is especially important in a clade that otherwise demonstrates isometric growth patterns. (They don’t change much as they mature, contra traditional studies.)

Perhaps a more parsimonious solution is to place the smaller specimen in the bushy lineage of the larger specimen. Different sizes = different diets = different teeth.

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
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 2007. A juvenile Tanystropheus sp.(Protoro sauria: Tanystropheidae) from the Middle Triassic of Guizhou, China. Vertebrata PalAsiatica 45(1): 37-42.
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
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 of Tanystropheus (Reptilia Protorosauria) from the Middle Triassic of Switzerland and the ecology of the genus. Rivista Italiana di Paleontologia e Stratigrafia vol. 111, no. 3, 377–394. online pdf
Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus (Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-16.

wiki/Tanystropheus