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/

Was the AMNH Tanytrachelos ‘with child’?

Tanytrachelos ahynis (Olsen 1979, holotype AMNH 7496; holotype Fig. 1) Latest Triassic, 200 mya, was derived from Macrocnemus and was a sister to Langobardisaurus and Tanystropheus. All are tritosaur lepidosaurs in the lineage of the terrestrial ancestors of pterosaurs, the Fenestrasauria… all ultimately derived from an earlier sister to late-surviving Huehuecuetzpalli and Tijubina.

Figure 1. AMNH 7496 holotype of Tanytrachelos with original tracing from Olsen 1979. DGS colors added.

Figure 1. AMNH 7496 holotype of Tanytrachelos with original tracing from Olsen 1979. DGS colors added.

The AMNH specimen
(Fig. 1) preserved in ventral exposure, appears to have two halves of a leathery eggshell and an ‘exploded’ embryo, best described as several dozen tiny bones that should not be there, unless, perhaps this was a gravid adult… or something else, like gastroliths, undigested prey… hard to tell. In any case, some of the pectoral bones also have new identities here.

Figure 5. Hypothetical Tanystropheus embryo compared to Dinocephalosaurus embryo.

Figure 2. Hypothetical Tanystropheus embryo compared to Dinocephalosaurus embryo. These are the sorts and sizes of bones one should look for in any maternal Tanytrachelos.

Figure 1. Tanytrachelos hopping to match Gwyneddichnium tracks (see figure 2).

Figure 3. Tanytrachelos hopping to match Gwyneddichnium tracks (see figure 2).

Distinct from Langobardisaurus,
Tanytrachelos has twelve cervicals, but none were gracile. The posterior cervical ribs had large heads that kept the rods far from each centrum. Heterotopic bones were present. These appear to be elongated chevrons, as in Tanystropheus. Rare hopping prints (Fig. 2) match the size and shape of Tanytrachelos pedes.

langobardisaurus-pectoral-girdle

Figure 4. The sternal complex of several other tritosaurs. Tanytrachelos is closer to Tanystropheus, not quite like any of these related taxa, but all are informative.

The elliptical sternum
of Tanytrachelos was wide, as in Langobardisaurus (Fig. 3), but the clavicle remained gracile, as in Huehuecuetzpalli (Fig. 3). The humerus was slightly bowed. Metacarpal I aligned with the others. Metatarsal III was the longest. Digit III was the longest as in Langobardisaurus tonelloi.


References
Olsen PE 1979. A new aquatic eosuchian from the Newark Supergroup Late Triassic-Early Jurassic) of North Carolina and Virginia. Postilla 176: 1-14.
Smith AC 2011. Description of Tanytrachelos ahynis and its implications for the phylogeny of Protorosauria. PhD dissertation. Virginia Polytechnic Institute and State University.

 

Spiekman and Scheyer 2019 discuss variation in Tanystropheus

In 2014 we looked at
the same subject, variation in Tanystropheus, from a graphic reconstruction framework (Figs. 1–3) tucked within a phylogenetic analysis.

Spiekman and Scheyer 2019 used a statistical and descriptive approach
to variation in Tanystropheus that, due to the limited nature of statistics, misses important aspects. Imagine all the work they put into their first hand observations and computations of every European specimen, but then somehow missing the big picture by not creating a single reconstruction from a crushed skull (as shown in figure 1).

And they completely missed out
on the fact  that Tanystropheus is a tritosaur lepidosaur, not an archosauromorph. That’s what the large reptile tree (LRT, 1622+ taxa)  is here for. Let others focus on the micro-details. Let the LRT handles the broader scope interrelationships, some of which have direct bearing on conclusions offered by Spiekman and Scheyer.

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 m.

The authors introduce their paper:
“Tanystropheus represents one of the most enigmatic tetrapod taxa of the Triassic due to its unique morphology and palaeobiology. Its most striking aspect is its extremely long neck, which consists of a relatively small number (13, see Rieppel et al., 2010) of bizarrely elongated cervical vertebrae with reduced neural spines. This type of cervical vertebrae is unique among tetrapods and easily recognizable.”

No. Tanystropheus is not enigmatic. It is instead very well known and understood in a phylogenetic context. The morphology is not unique. Rather it has several similar sisters and even a long list of convergent taxa with similar long cervicals.

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

Figure 2. Click to enlarge. Four large Tanystropheus specimens in situ and reconstructed. The man silhouette is 6 feet (1.8m) tall. Note the larger head on the largest specimen.

The authors state,
“Although it is unclear whether the two represent different species or distinct ontogenetic stages of the same species, a synonymy list and specimen list is provided for both morphotypes.” If only Spiekman and Schuyer had referenced the LRT or created their own wide gamut phylogenetic analysis, that lack of clarity would have been clarified. A cladogram is a powerful tool. Don’t write a paper without one.

Tanystropheus and kin going back to Huehuecuetzpalli.

Figure 3. Tanystropheus and kin going back to Huehuecuetzpalli. None of these taxa change during ontogeny. Rather they all develop isometrically.

More to the point,
all tested tritosaurs known from juveniles and adults, from Huehuecuetzpalli (Fig. 3) to Zhejiangopterus, display isometric growth during ontogeny. That means any minor or major differences can be attributed to phylogeny, not ontogeny, in the Tanystropheus clade. The answer is that simple. No need for statistical analyses. A wide gamut phylogenetic analysis, like the LRT, solves so many problems decisively and with clarity.


References
Spiekman SNF and Scheyer TM 2019. A taxonomic revision of the genus Tanystropheus (Archosauromorpha, Tanystropheidae). Palaentologia Electronica 22.3.80 PDF

New tanystropheid paper promotes archosauromorph myth

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

Tanystropheus underwater among tall crinoids and small squids.

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

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

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

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

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

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

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

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

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

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

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

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

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

Tanystropheus and kin going back to Huehuecuetzpalli.

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

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


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

https://pterosaurheresies.wordpress.com/2015/09/26/relatively-giant-tanytrachelos-specimens/

Tanystropheus: aquatic? or terrestrial?

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.

Beard and Furrer 2017 conclude (or do they?)
that Tanystropheus (Figs. 1–3) was likely terrestrial.

From the abstract
“The Middle Triassic protorosaur Tanystropheus has been considered as both a terrestrial and aquatic taxon based on several lines of biomechanical and distributional evidence, but determining conclusively which habitat was most likely has remained problematic. The preservation of Tanystropheus was found to be more similar to Macrocnemus than Serpianosaurus implying carcasses of Tanystropheus originated in terrestrial or at least marginal and near-shore, shallow marine settings. That these were also the most probable habitats in life is supported by the relatively lower number of Tanystropheus (and also Macrocnemus) compared to Serpianosaurus.”

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.

Unfortunately,
Tanystropheus was not a protorosaur, nor a member of the Archosauromorpha. It was a tritosaur lepidosaur as taxon inclusion would have informed the authors.

Tanystropheus and kin going back to Huehuecuetzpalli.

Figure 2. Tanystropheus and kin going back to Huehuecuetzpalli.

Unfortunately,
the smaller Tanystropheus considered a juvenile by the authors was probably a different genus, based on a long list of distinct traits, including its distinct teeth. Moreover the authors did not realize that several large putative Tanystropheus specimens have distinct skull morphologies that are not congeneric (Fig. 2). But all that is beside the point…

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

Figure 3. Tanystropheus with skull reconstructions based on two specimens, exemplar i and exemplar m.

The authors report:
“An alternative aquatic lifestyle has also been suggested for Tanystropheus (Tschanz 1988). The main argument is the supposed inflexibility of the neck due to the elongated vertebrae and bundled cervical ribs that prevented all but a horizontal position (Tschanz 1988; Renesto 2005).”

Or any aquatic position,
including vertical (Fig. 1). The authors do cite the hooks from squid suckers found in the stomach region (Wild 1973; Fig. 1) and other prior hypotheses, then describe the taphonomy of the skeletons. The authors cite trackway data matched to Tanystropheus, (Fig. 3) ignoring the fact that even sea turtles leave trackways on beaches when they lay eggs.

Figure 3. Tanystropheus specimens matched to Synaptichnium tracks. The match is good in each case, except for one toe or the other.

Figure 3. Tanystropheus specimens matched to Synaptichnium tracks. The match is good in each case, except for one toe in each trackway. So, is this good enough? Or is this cause for dismissal?

Did the authors test the tracks?
No. But that is done here (Fig. 3). In each case there is a pretty good match—except for one toe in each case. The manus and pes have been scaled to match the tracks and thus are not matched to the scale bars which are for the tracks alone. Even so, the scale for the trackmakers’ extremities is a pretty good match! The case is not rock solid, but pretty good, that big and small tanystropheids made those Synaptichnium tracks.

Taphonomy 
The journey from the biosphere to the lithosphere was investigated. The terrestrial Ticinosuchus, a type of archosauriform, was discovered in these beds along with the aquatic Serpianosaurus, a type of pachypleurosaur, according to the authors (a basal thalattosaur in the large reptile tree). So was the tritosaur lepidosaur, Macrocnemus. The authors wondered if the taphonomy of Tanystropheus would be more similar to the terrestrial or the aquatic taxa. Wild (1973) listed and illustrated  over a dozen specimens of Tanstropheus in various stages of completeness and articulation. The water depth of fossil deposition was estimated between 30 and 130m with anoxic bottom conditions. So ALL the specimens were transported horizontally and vertically. Importantly, fragmentary skeletons of Tanystropheus were excluded from this study. From the remaining data the authors compiled articulation and completeness scores.

Why did they throw out competing data?
We’ve seen this before with Hone and Benton (2007, 2008). Given that they used only the more complete specimens (and who knows how many incomplete specimens were never collected), the authors report Tanystropheus specimens exhibited 0-58% articulation and 36–97% completeness. Larger specimens tended to be more complete. The authors also note that Serpianosaurus alone lacks obvious features that promoted buoyancy, like hollow cervicals in Tanystropheus. The authors cite Brand et al. 2003, who noted “lizard skin in water formed a limp but durable bag containing the bones” during water transport.

The authors conclude
“Tanystropheus langobardicus at least died in, but probably also lived in a terrestrial or near-shore marine setting.” The presence of squid hooks in the stomach “does not necessarily preclude a more-normal niche in shallow water.” 

‘Near shore marine’ = aquatic.
So the authors conclusion is no conclusion at all. Contra their headline, they did not ‘determine’ anything. It could have been on the beach, or in shallow water. Is the marine iguana (Amblyrhynchus cristatus) aquatic? or terrestrial? What would you say if you only found its skeleton? Or its footprints?

The good evidence continues to be
the stomach contents as the best evidence for life style (feeding niche) for the giant forms. Let the smaller ones feed in shallower waters. Let both give birth and warm up on land, like marine iguanas.

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.
Beard SR and Furrer 2017. Land or water: using taphonomic models to determine the lifestyle of the Triassic protorosaur Tanystropheus (Diapsida, Archosauromorpha). Palaeobiodiversity and Palaeoenvironments (advance online publication) DOI: https://doi.org/10.1007/s12549-017-0299-7
https://link.springer.com/article/10.1007/s12549-017-0299-7
Diedrich C 2008. Millions of reptile tracks—Early to Middle Triassic carbonate tidal flat migration bridges of Central Europe—reptile immigration into the Germanic Basin. Palaeogeography, Palaeoclimatology, Palaeoecology, 259, 410–423.
Haubold HA 1983. Archosaur evidence in the Buntsandstein (Lower Triassic). Acta Palaeontologica Polonica, 28, 123–132.
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.
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/Tanystropheus

Another long-necked embryo tritosaur: Li et al. in press

This appears to be
yet another Tanystropheus-like and Dinocephalosaurus-like taxon, yet not closely related to either. Earlier we looked at another similar embryo, still within its mother.

Li, Rieppel and Fraser in press (2017)
bring us a new curled up (as if in an egg, but without a shell) embryo from the Guanling Formation (Anisian), Yunnan province, China (Figs. 1, 2). The specimen is unnamed and not numbered. It appears to combine the large head and eyes of langobardisaurs with the short limbs and many cervical vertebrae of Dinocephalosaurus. Please remember, in this clade, juveniles do not have a short rostrum and large eyes unless their parents also had these traits.

Figure 1. The unnamed and not numbered Triassic embryo Li et al. assign to a new species close to Dinocephalosaurus.

Figure 1. The unnamed and not numbered Triassic embryo Li et al. assign to a new species close to Dinocephalosaurus. At 72 dpi monitor resolution, this image is 2.5x life size. Here bones are colorized, something Li et al. could have done, but avoided. I’m happy to report that the line drawing was traced by Li et al. on their own photo. The two are a perfect match.

Unfortunately
Li et al. have no idea what they’re dealing with phylogenetically. They relied on old invalidated hypotheses of relationships. They report the specimen:

  1.  is a marine protorosaur and an archosauromorph – actually it is a marine tritosaur lepidosaur. Taxon exclusion and traditional bias hampered the opinion of Li et al. They did not perform a phylogenetic analysis.
  2. is closely related to Dinocephalosaurus – actually it is more closely related to the much smaller, but longer-legged Pectodens (Figs. 4, 5). In the large reptile tree (LRT, 1036 taxa) 8 steps are added when the embryo is force-nested with Dinocephalosaurus. The embryo is distinct enough that the new specimen deserves a new genus.
  3. confirms viviparity – probably not (but see below). The specimen is confined within an elliptical shape (Fig. 1), as if bound by an eggshell or membrane, which was not preserved. Perhaps, as in pterosaurs and many other lepidosaurs, the embryo was held within the mother’s body until just before hatching, within the thinnest of egg shells and/or membranes.
  4. is too immature to describe it as a new taxon – not so. Tritosaur lepidosaurs (from Huehuecuetzpalli to Pterodaustro) develop isometrically. Thus, full-term embryos and hatchlings have adult proportions.
Figure 2. The specimen from figure 1 unrolled for clarity. This specimen most closely resembles the basal langobardisaur, Pectodens, not Dinocephalosaurus. Remember, tritosaurs develop isometrically. Embryos closely resemble adults. That's why three scale bars are included.

Figure 2. The specimen from figure 1 unrolled for clarity. This specimen most closely resembles the basal langobardisaur, Pectodens, not Dinocephalosaurus. Remember, tritosaurs develop isometrically. Embryos closely resemble adults. That’s why three scale bars are included. This specimen has feeble limbs but a strong swimming tail, distinct from that of Dinocephalosaurus.

Li et al. report
“In the fossil record only oviparity and viviparity can be distinguished, Ovoviviparity of different intermediate stages, which is often observed in modern squamates would then be referred to the category of viviparity, whatever the stages of maturity and nutritional patterns are.” Yes, they correctly report ovoviviparity in squamates, which are the closet living relatives of tritosaur lepidosaurs. That’s exactly what we have here.

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 3. 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.

Li et al. report,
“[The] skeleton is preserved tightly curled so as to produce an almost perfect circular outline, which is strongly indicative of an embryonic position constrained by an uncalcified egg membrane.”

Figure 2. Pectodens skull traced using DGS techniques and reassembled below.

Figure 4. Pectodens skull traced using DGS techniques and reassembled below. No sclerotic ring here. 

Distinct from Pectodens the new genus embryo has:

  1. 24 cervicals
  2. 29 dorsals
  3. 2 sacrals
  4. and about 64 caudals
Figure 1. Pectodens reconstructed using the original tracings of the in situ fossil in Li et al. 2017.

Figure 5. Pectodens reconstructed using the original tracings of the in situ fossil in Li et al. 2017. The skull shown here is the original reconstruction. Compare it to figure 4.

Li et al overlooked:

  1. strap-like coracoids, strip-like clavicle and T-shaped interclavicle
  2. scattered manual elements
  3. pelvic girdle
  4. ectopterygoid, jugal, articular, angular, surangular

Li et al. report:
“The fewer cervical vertebrae (24 as opposed to 33 (based on an undescribed specimen kept in the IVPP)), and the presence of sclerotic plates are features inconsistent with Dinocephalosaurus.This embryo therefore documents the presence of at least one additional dinocephalosaur-like species swimming in the Middle Triassic of the Eastern Tethys Sea.

“Scleral ossicles have previously not been described in any protorosaur.”
– but they are common in tritosaur lepidosaurs, like pterosaurs.

Figure 6. Pectodens adult compared to today's embryo and its 8x larger adult counterpart after isometric scaling.

Figure 6. Pectodens adult compared to today’s embryo and its 8x larger adult counterpart after isometric scaling. Looks more like Pectodens than Dinocephalosaurus, doesn’t it? See taxon inclusion WORKS! Sclerotic rings were omitted here to show skull bones. The ring would have had a smaller diameter if if were surrounding a sphere, rather than crushed flat. 

A word to traditional paleontologists:
Don’t keep digging yourself deeper into invalidated hypotheses and paradigms. Use the LRT, at least for options.

Don’t give up on naming embryos
and adding them to phylogenetic analysis, especially if they are tritosaur lepidosaurs. Hatchlings nest with adults so you can used hatchlings in analysis.

Don’t avoid creating reconstructions.
That’s a great way to discover little splinters of bone, like clavicles and coracoids, that would have been otherwise overlooked.

The LRT is here for you.
BETTER to check this catalog prior to submission rather than have your work criticized for being unaware of the latest discoveries or overlooking pertinent taxa AFTER publication.

References
Li C, Rieppel O, Fraser N C, in press. Viviparity in a Triassic marine archosauromorph reptile. Vertebrata PalAsiatica, online here.

Pectodens: basal to tanystropheids and pterosaurs

It’s always good
to see another tritosaur. That’s the lineage that gave rise to a menagerie of taxa, including pterosaurs. That’s a heretical hypothesis of relationships recovered by the large reptile tree (LRT, 997 taxa).

Figure 1. Pectodens reconstructed using the original tracings of the in situ fossil in Li et al. 2017.

Figure 1. Pectodens reconstructed using the original tracings of the in situ fossil in Li et al. 2017.

Li et al. 2017 conclude:
“A new, small terrestrial tetrapod is described from the Middle Triassic of Yunnan, China. Pectodens zhenyuensis n. gen. n. sp. bears very characteristic elongate teeth forming a comb-like marginal dentition. The elongate cervicals of Pectodens zhenyuensis n. gen. n. sp. with low neural spines together with the morphology of the cervical ribs are features consistent with protorosaurs, such as Macrocnemus. However, the imperforate puboischiadic plate, simple rounded proximal tarsals, and a straight 5th metatarsal are primitive characteristics. Unlike tanystropheids, but in common with Protorosaurus (personal observation, N.C. Fraser, 2013), both lack a thyroid fenestra in the pelvis.”

Figure 2. Pectodens skull traced using DGS techniques and reassembled below.

Figure 2. Pectodens skull traced using DGS techniques and reassembled below. Here a quadratojugal process of the jugal is identified and other parts are assembled with greater accuracy than a freehand sketch (Fig. 1).

Pectodens zhenyuensis (Li et al. 2017; IVPP V18578; Anisian, Middle Triassic; 38cm in length) was originally considered a diapsid and a possible protorosaur. Here Pectodens nests between Macrocnemus and Langobardisaurus (Fig. 3). Originally the interclavicle, sternum and quadratojugal were overlooked.

Note the large orbit, the long metarsal 5 and the perforated pubis. The elongate caudal transverse processes anchor powerful leg muscles.

Occasionally within the Tritosauria
metatarsal 5 is not short, but elongate. It is always axially twisted. The pubis and ischium typically angle away from one another, but sometimes produce a thyroid fenestra. Tritosaurs have a sternum, like many other lepidosaurs do. Protorosaurs do not have a sternum.

Li et al. did not attempt a phylogenetic analysis.
Instead they made educated guesses as to the affinities of Pectodens, overlooking the variation present in related taxa revealed in a cladogram. Pulling a Larry Martin (highlighting or letting yourself get confused by one or two traits) is never a good idea. Better to let hundreds of traits determine the exact nesting of a taxon without bias. Let the taxa nest themselves. Let the convergent traits simply be convergent traits.

Earlier we looked at the pectoral girdle and sternum of Langobardisaurus, Huehuecuetzpalli and other tritosaurs. Pectodens fits right in.

The posterior maxillary teeth in Pectodens
are wider at their base presaging the grinding teeth found in Cosesaurus, basal pterosaurs and Langobardisaurus.

Note the way the fingers and toes
bend anteriorly during use. That’s a lepidosaur trait. Pectodens would have had sprawingling hind limbs given its simple femoral head. Tracks matching such curved toes are known from the Middle Triassic.

Li et al. considered Pectodens to be the first terrestrial taxon
from the its locality. And that’s definitely a probability. However, given that Tanystropheus and others may have been underwater bipedal predators (squid parts were found in their torso), let’s leave open the possibility that Pectodens was maybe dipping its toe in the water.

Figure 1. Subset of the LRT focusing on Tritosauria. Pectodens nests here basal to the Characiopoda (Tanystropheids + Fenestrasauria including pterosaurs).

Figure 1. Subset of the LRT focusing on Tritosauria. Pectodens nests here basal to the Characiopoda (Tanystropheids + Fenestrasauria including pterosaurs).

Let’s not continue to nest tanystropheids
with protorosaurs. Sure they share several traits by convergence, but they are not related to one another as determined by a large gamut analysis, the LRT.

References
Li C, Fraser NC, Rieppel O, Zhao L-J and Wang L-T 2017. A new diapsid from the Middle Triassic of southern China. Journal of Paleontology.7 pp. doi: 10.1017/jpa.2017.12

 

Live birth in ‘Dinocephalosaurus’? Maybe. Maybe not.

Yesterday Liu et al. 2017 reported on
a pregnant Dinocephalosaurus (Figs. 1-5). This is wonderful and exciting news. However, the embryo is NOT in the process of passing through the cloaca, as we’ve seen in ichthyosaurs. The embryo is much higher in the abdomen, still in the uterus. So the headline “Live birth in an archosauromorph reptile” is… at best… premature. Live birth is still a possibility. A critical examination of the data reveals a few more major and minor problems.

Dinocephalosaurus in resting, feeding and breathing modes.

Figure 1. The holotype (not the new specimen) of Dinocephalosaurus in resting, feeding and breathing modes. In breathing mode the throat sac would capture air that would not be inhaled until the neck was horizontal at the bottom of the shallow sea. Orbits on top of the skull support this hypothesis. Image from Peters 2005. The new specimen has a longer neck, a more robust tail, and a different pedal morphology.

Unfortunately
the authors nested Dinocephalosaurus within the Archosauromorpha (Fig. 2). That is incorrect. Dinocephalosaurus nests within the new Lepidosauromorpha in the large reptile tree (LRT, 952 taxa), which minimizes the taxon exclusion problem suffered by the much smaller taxon list in the Liu et al. 2017 tree.

Figure 6. Cladogram from Liu et al. 2017 with colors added based on results from the LRT. Taxon exclusion is a major problem here.

Figure 2. Cladogram from Liu et al. 2017 with colors added based on results from the LRT. Taxon exclusion is a major problem here. Note in the Liu et al. cladogram members of the Protorosauria are divided into three clades. In sympathy, members of the Tritosauria and Protorosauria do indeed converge with one another. More taxa clears up the problem shown here of cherry-picking taxa.

Dinocephalosaurus actually nests
within the lepidosaur clade, Tritosauria, a clade that also includes Tanystropheus, pterosaurs and several other taxa (Fig. 7) that had been mistaken for protorosaur relatives in the Liu et al and other prior studies.

As a lepidosaur, 
Dinocephalosaurus would have been able to retain embryos within the mother far longer that in extant archosauromorphs. And based on the extreme thinness of pterosaur eggshells (closest known relatives with embryos, Fig. 7), those leathery eggshells only develop just prior to egg laying. So live birth is only one of a spectrum of options for Dinocephalosaurus. As in pterosaurs, the eggs could have hatched shortly after the female laid them on the shoreline.

Dinocephalosaurus. Note the very narrow cranial portion of the skull and the very wide cheeks. That, by it self, opens the orbits dorsally. Sure there's some lateral exposure, but those eyes are looking up!

Figure 3. The holotyype of Dinocephalosaurus. Although extremely similar, the new specimen is different in several ways. See below.

Liu et al. report that live birth is unknown in the Archosauromorpha.
However, in the LRT mammals and enaliosaurs (sauropterygians + ichthyosaurs) are both archosauromorphs that experience live birth. Hyphalosaurus, a choristodere archosauromorph, had extremely thin eggshells and retained developing embryos inside the mother until laying those eggs.

Figure 5. Hypothetical Tanystropheus embryo compared to Dinocephalosaurus embryo.

Figure 4. Hypothetical Tanystropheus embryo compared to part of an embryo of the new specimen attributed to Dinocephalosaurus.

More about that embryo
What little is preserved of the Dinocephalosaurus embryo (Fig. 4) is curled up in its amniotic sac, as one would expect for any reptile embryo still in utero. For comparison, note the hypothetical Tanystropheus embryo alongside it. That long neck has to go somewhere and Dinocephalosaurus provides further evidence that juvenile tritosaurs were isometric duplicates of their adult parents. That long neck did not develop with maturity. Among other tritosaurs we see juveniles similar in proportion to adults in the basal form, Huehuecuetzpalliand all pterosaur embryos.

Liu et al. further report. “Despite the complexity of this transition, viviparity has evolved at least 115 times in extant squamates (lizards and snakes), in addition to a single time in the common ancestor of therian mammals. Moreover, viviparity is a common reproductive mode in extinct aquatic reptiles including eosauropterygians, ichthyosaurs, mosasauroids, some choristoderans and likely mesosaurs.” Since mosasauroids are extinct squamates that makes at least 116 times for lepidosaurs.    Some living squamates produce eggs that hatch shortly after they are expelled, a sort of transition from oviparity to viviparity. That’s where pterosaurs fall and perhaps Dinocephalosaurus.

More cladogram issues
The Liu et al. figure 1 cladogram shows a polytomy of most reptilian clades arising during the Permian. No such polytomy appears in the LRT in which Archosauromorpha diverged from the Lepidosauromorpha tens of millions of years earlier in the Viséan (Lower Carboniferous). Liu et al. mistakenly report that trilophosaurs, rhynchosaurs and pterosaurs are archosauromorph reptiles. They are lepidosauromorph reptiles in the LRT.

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 5. The new Dinocephalosaurus has traits the holotype does not have, like a longer neck with more vertebrae, a robust tail with deep chevrons and a distinct foot morphology with a more elongate pedal digit 4. The partial embryo is in magenta at left.

The new specimen looks like a Dinocephalosaurus, but is it one?
Distinct from the holotype, the new specimen has a deep robust tail with deep chevrons (Fig. 5). They all share a common ancestor in one of the highly variable Macrocnemus specimens (Fig. 7). The toes of the new specimen are more asymmetric. The neck probably has more vertebrae (several are lost, but note the longest ones are NOT at the base of the neck in the holotype). Unfortunately little more can be said with so much of the mother lacking at present. We’ve already seen a Chinese Tanystropheus similar to, but not identical to the European Tanystropheus. We can imagine even greater variation within the available gamut of the present sparse fossil evidence.

It really is too much
to expect identical specimens to come from distinct fossil bearing strata. So variation within Dinocephalosaurus is a possibility.

Next steps
The paleo-community needs to include more specimen-based taxa in their cladograms or the Liu et al. problem (not restricted to them!) is going to continue ad infinitum. I know that’s a lot of work. But it can be done (I’ve done it!) and it needs to be done. Just start with a large gamut analysis and keep adding taxa to it. That will make the current phylogenetic problems go away.

Final note
Images of tanystropheids and dinocephalosaurs swimming horizontally through open waters (Liu et al. 2017 their figure 3) may not be an accurate portrayals of their daily lives. Other options have been published (Fig. 1) or appear online (Fig. 8). Odd-looking tetrapods often have uncommon niches and atypical behaviors.

Tanystropheus underwater among tall crinoids and small squids.

Figure 8. 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.

References
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.

 

A Tanystropheus from China

Figure 1. Click to enlarge GIF animation. The Tanystropheus specimen from China, GMPUKU-P-1527: 1)  in situ; 2) as traced by Rieppel et al. 2010; and 3) with colorized DGS tracings. Note: Rieppel et al. overlooked the interclavicle, and mistook the interclavicle + scapula for an over sized coracoid. Rieppel's clavicle is a dorsal rib. The so-called heterotopic bones are merely larger, unfused chevrons.

Figure 1. Click to enlarge GIF animation. The Tanystropheus specimen from China, GMPKU-P-1527: 1)  in situ; 2) as traced by Rieppel et al. 2010; and 3) with colorized DGS tracings. Note: Rieppel et al. overlooked the interclavicle, and mistook the interclavicle + scapula for an over sized coracoid. Rieppel’s clavicle is a dorsal rib. Clavicles here are in red. The so-called heterotopic bones are merely larger, unfused chevrons. What are those blue triangles in the dorsal area? The distal opposite rib tips apparently. Let me know if there’s a better answer.

Rieppel et al. (2010)
described a new, large (trunk length 93.5 cm), Late Triassic Tanystropheus (GMPKU-P-1527, Fig. 1), the first from China. All priors had come from the Alps of Europe. This one lacks a skull plus three cervicals and the distal tail. Based on the short rib of what used to be considered dorsal 1, the authors report it is now cervical 13. That appears to be the case across all large and small specimens. The last cervical is the size and shape of a dorsal, but the associated rib is not a dorsal-type rib. Every prior worker missed that one. Rieppel et al bucked traditions and relabeled the old first dorsal. Good job guys!

New interpretations
of the clavicle, interclavicle, scapula and one coracoid are introduced above, a little different than the original interpretations.

How similar to the European specimens?
the authors report: “The new Peking University specimen (GMPKU-P-1527) is remarkably similar to the larger specimens of Tanystropheus longobardicus housed in the paleontological collections of Zurich University. If there is any difference, then it is in the extent of chevron bones in the tail and the lack of the slight swellings and associated flexure described here for the first time along the length of the longest cervical ribs in PIMUZ T 2189 (Exemplar Q, Fig. 3.

At first glance (in situ) the Chinese specimen is indeed similar to the European specimens.

Figure 2. The Tanystropheus from China partly reconstructed using DGS methods. No foreshortening of the gastralia and limbs are present here. The preserved ilium is not a broad plate here, as in European specimens. The terminal tail vertebrae is circular suggesting the rest of the tail was preserved in another layer.

Figure 2. The Tanystropheus from China partly reconstructed using DGS methods. No foreshortening of the gastralia and limbs are present here. The preserved ilium is not a broad plate here, as in European specimens. That could be a taphonomic artifact or reality. The terminal tail vertebrae is circular suggesting the rest of the tail was preserved in another layer.

But not the same species
The China specimen is apparently more distinct from the European specimens than Rieppel et al. indicate., but then… they did not create any reconstructions. Sometimes comparisons are best seen directly with accurate reconstructions (Fig. 3). We’ve already seen that two very distinct skulls appear on the European specimens and both were distinct from the original Wild 1973 model based on a chimaera of specimens.

The China specimen
has larger girdles, larger vertebrae, more robust ribs and shorter toes (Fig. 4), among the more readily visible distinctions. The dorsal ilium appears to be much narrower, but it is obscured by an overlying femur. The interclavicle has a large, broad anterior process, making it cruciform, not T-shaped.

Figure 3. The large Tanystropheus specimens to scale. On the right the new China specimen has large girdles, larger vertebrae, more robust ribs and shorter toes, among the more visible distinctions. Click to enlarge. Above right is the new M. Witton reconstruction with erect limbs, an overly large scapula, an overly large ilium, lacking an interclavicle and other minor issues. 

Figure 3. The large Tanystropheus specimens to scale. On the right the new China specimen has large girdles, larger vertebrae, more robust ribs and shorter toes, among the more visible distinctions. Click to enlarge. Above right is the new M. Witton reconstruction with erect limbs, an overly large scapula, an overly large ilium, lacks an interclavicle and other minor issues. Otherwise it is very good looking.

Check those hands and feet!
Earlier we were able to separate Rhamphorhynchus specimens into clades using pedal traits alone. Here we’ll compare a European Tanystropheus with the Chinese one (Fig. 4). If they don’t match, they are not conspecific.

Figure 4. Above the Chinese Tanystropheus. Below a large European Tanystropheus. They are not conspecific.

Figure 4. Above the Chinese Tanystropheus. Below a large European Tanystropheus. They are not conspecific.This was overlooked by Rieppel et al. 2010. Reconstructions have value.

Mark Witton started this 
A recent blog post by Mark Witton introduced a new reconstruction of Tanystropheus (Fig. 3 top right). He wondered if the neck was too heavy to use on land while reminding readers that my work was “produced with techniques of questionable reliability”. Keep that phrase in mind.

  1. Witton labeled Tanystropheus as a protorosaur. Actually it’s a tritosaur lepidosaur as indicated by a four-year-old cladogram that now tests 602 taxa.
  2. On tradition alone, Witton includes drepanosaurs, Sharovipteryx, Tanytrachelos, Langobardisaurus and Dinocephalosaurus in the protorosaurs. All are indeed related to Tanystropheus, and are likewise tritosaur lepidosaurs.
  3. Witton reports, “I decided to try my hand at producing a new skeletal reconstruction based on the large, near complete Tanystropheus skeleton described in detail by Rieppel et al. (2010): PIMUZ T 2189.” Unfortunately the skeleton described by Rieppel et al. and traced by Witton is GMPKU-P-1527, the Chinese specimen (Figs. 1, 2). The 2189 specimen is European (Fig. 3), represented by a skull and neck only (Fig. 3). Witton’s technique was to trace a published photo. He makes no mention of visiting the specimen first hand. If you’ll remember, the technique of questionable reliability” mentioned above is my sin of tracing fossil from photographs. So Witton is doing exactly what I do. Is Witton aware of this possible hypocrisy?
  4. Witton reports, “I reconstructed missing parts using smaller Tanystropheus specimens (from Nosotti 2007) and Wild’s widely-used ‘adult’ skull reconstruction.” So he created a chimaera. That is almost never a good idea going as far back as to putting a Camarasaurus skull on a Brontosaurus body. It’s easy, but it’s wrong. “Widely used” doesn’t mean it is correct. As mentioned above, that skull is a chimaera, too.
  5. Witton’s reconstruction admits to cheating on the true sprawling pose for his geometrical analysis. That’s fine. I laid limb elements out straight,too, but not in a walking pose. That would be confusing to someone who didn’t know what the illustration was being used for.
  6. Adding to the confusion, Witton draws a medially directed femoral head which is not present in this lepidosaur.
  7. Witton’s Tanystropheus scapula is too large (see above). The pelvis is a chimaera and a shade too large. Otherwise it’s a beautiful reconstruction and part of that beauty comes from free handing certain elements. I won’t say Witton’s work as a whole is produced with techniques of questionable reliability.l like tracing, free handing and creating chimaeras… but I will say that free handing and creating chimaeras is not reliable. Tracing from photographs can be very reliable! Ad hominem blackwashing (see Witton’s comment) is never appropriate for colleagues. Everyone should realize that inappropriate habits, like creating chimaeras, never last forever. And everybody makes honest mistakes (like overlooking the interclavicle). Finally holding a grudge or never granting forgiveness for past errors is never good… Right guys? Okay. Let’s move on…
  8. Witton reports, “Our problem here is that finding a long-necked terrestrial carnivore to compare with Tanystropheus is challenging.” I realize that Witton is wondering if a large Tanystropheus could walk on land, but gut contents are marine organisms and fossils are found in marine sediments. So… what’s the point? And why were these factoids ignored? The big Tanystropheus doesn’t seem to be a terrestrial animal.
  9. Ironically, Witton compares the long neck of Tanystropheus to his favorite pterosaurs, the azhdarchids. And that’s a fair comparison. They are distantly related in the large reptile tree, but for Witton’s purposes shapes are more important.
  10. Witton’s technique for determining mass at every segment of a lateral view misses the greater mass in the wider dorsal and caudal areas visible only in dorsal view. There’s a fat rump there, but you can’t see it in lateral view.
  11. Little known pertinent fact: I once made a full scale model in wood of Tanystropheus and sold it to the AMNH. I had to add lead weights aft of the hind limbs to make it not tip over. All segments being equal, it was front heavy as a 3-D model, not just on paper.  In vivo the torso and tail would have been more dense, even with large lungs. And the air-filled cervical series and trachea would have been less dense.
  12. Check this out for a possible marine lifestyle that seems to fit the facts for Tanystropheus.

References
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.
Witton blog post: here

The BES SC 111 specimen of Macrocnemus – DGS helps reconstruct it

Previously considered (Renesto S and Avanzini M 2002) a juvenile due to its size, the BES SC 111 specimen of Macrocnemus (Fig. 1) sheds light on the origin of such diverse lineages as the Tanystropheidae (Langobardisaurus, Fig. 2) and the Fenestrasauria (Cosesaurus through the Pterosauria, Fig. 2). It also nests at the base of other Macrocnemus specimens including the oddly bizarre, Dinocephalosaurus (Fig. 3).

Figure 1. Click to enlarge. Stages in the DGS tracing and reconstruction of the the Macrocnemus BES SC 111 skull. I did not realize the the palatal bones were so visible. There's a palatine and ectopterygoid over the nasal and frontal, for instance. So earlier mistakes were made that are corrected here. The right mandible is traced here only along its ventral rim.

Figure 1. Click to enlarge. Stages in the DGS tracing and reconstruction of the the Macrocnemus BES SC 111 skull. I did not realize the the palatal bones were so visible. There’s a palatine and ectopterygoid over the nasal and frontal, for instance. So earlier mistakes were made that are corrected here. The right mandible is traced here only along its ventral rim.

Derived from
an early Triassic sister to Huehuecuetzpalli and/or Jesairosaurus, the BES SC 111 specimen seems to have at least a depression in the dorsal maxilla that will ultimately become an antorbital fenestra in the Fenestrasauria. Note the resemblance of this skull to that of Cosesaurus and Langobardisaurus (Fig. 2). They all share a retracted naris, large orbit, bent quadrate, short postorbital region and relatively short teeth.

The reduction of pedal digit 5 in all known Macrocnemus specimens demonstrates the BES SC 111 nests at the base of the Macrocnemus lineage. An unknown sister without this reduction would be basal to Langobardisaurus and the Fenestrasauria.

Figure 2. Macrocnemus BES SC 111 compared to sister taxa, Langobardisaurus, Cosesaurus and the basal pterosaur, MPUM 6009. Preserved loose, the orientation of the ectopterygoids could go either way, with the narrow tip contacting the maxilla instead, as in Dinocephalosaurus (Fig. 3).

Figure 2. Macrocnemus BES SC 111 compared to sister taxa, Langobardisaurus, Cosesaurus and the basal pterosaur, MPUM 6009. 

Figure 3. Dinocephalosaurus to scale with the largest Macrocnemus specimen and the smaller ones from figure 2.

Figure 3. Dinocephalosaurus to scale with a large Macrocnemus specimen, T4822, and the smaller ones from figure 2.

The take-away from this is: large odd reptiles sometimes have their origin in not-so-large, not-so-odd reptiles like the BES SC 111 specimen. At the same time, small odd reptiles may have the same origin. Make sure you add the plain, old reptiles to your cladograms. That’s where the spectacular taxa have their origin.

References
Li C, Zhao L-J and Wang L-T 2007A new species of Macrocnemus (Reptilia: Protorosauria) from the Middle Triassic of southwestern China and its palaeogeographical implication. Science in China D, Earth Sciences 50(11)1601-1605.
Nopcsa F 1931. Macrocnemus nicht Macrochemus. Centralblatt fur Mineralogie. Geologic und Palaeontologie; Stuttgart. 1931 Abt B 655–656.
Peyer B 1937. Die Triasfauna der Tessiner Kalkalpen XII. Macrocnemus bassanii Nopcsa. Abhandlung der Schweizerische Palaontologische Geologischen Gesellschaft pp. 1-140.
Renesto S and Avanzini M 2002. Skin remains in a juvenile Macrocnemus bassanii Nopsca (Reptilia, Prolacertiformes) from the Middle Triassic of Northern Italy. Jahrbuch Geologie und Paläontologie, Abhandlung 224(1):31-48.
Romer AS 1970. Unorthodoxies in Reptilian Phylogeny. Evolution 25:103-112.

wiki/Macrocnemus