The first Langobardisaurus: MCSNB 2883

The day before yesterday
we looked at the latest (fourth) specimen attributed to the genus Langobardisaurus (Renesto 1994, Late Triassic). Today let’s look at the first specimen. This is really my first serious look at it because the second and third specimens were so much easier to study, both with good skulls.

The holotype of Langobardisaurus
(Renesto 1994, MCSNB 2883) has never (to my knowledge) been reconstructed, as it is here (Fig. 1), and not with to scale comparisons to the other three specimens. Saller et al. 2013 considered all four to be conspecific. However, as I found out, and as in so many putative pterosaur genera and Archaeopteryx genera, no two are alike.

Figure 1. Four Langobardisaurus specimens compared to scale. Contra Saller et al. 2013, these four specimens do not appear to be conspecific.

Figure 1. Four Langobardisaurus specimens compared to scale. Contra Saller et al. 2013, these four specimens do not appear to be conspecific.

Larger than the others (if the scale bars are correct),
the holotype of Langobardisaurus appears to have a smaller skull, smaller fingers and longer hind limbs. Distinct from two of the specimens, the tail remains long and robust. Powerful caudofemoral muscles were attached the elongate and numerous caudal ribs (fused transverse processes). The gastralia were more numerous with less space between sets. Such gastralia help hold up the anterior skeleton when standing bipedally. This specimen (MCSNB 2883) appears to be, by convergence, like Sharovipteryx, an obligate biped.

Figure 2. Langobardisaurus holotype in situ MCSNB 2883.

Figure 2. Langobardisaurus holotype in situ MCSNB 2883. Inserts show pectoral girdle elements and pes (x2).

Almost a worst case scenario for a roadkill fossil
the pectoral + skull region of MCSNB 2883 (Fig. 3) provides an excellent opportunity to try out the Digital Graphic Segregation (DGS) method. In the original photo you can see what a mess it is and how Renesto has labeled some of the bones and teeth, but ignores others and never outlines any of the bones. Colors just make things easier to understand in cases like this and it ensures that you are studying every millimeter of this fossil. Even tiny bone corners that peek out from beneath the rubble can be color coded. The reconstruction (Fig. 1) confirms or refutes your identifications as they fit or do not fit the assembled puzzle of bones without resorting to the danger of freehand illustration.

Figure 3. The pectoral region of Langobardisaurus (MCSNB 2883) with DGS color overlays. Compare to Figure 4 for identification of pectoral elements. Anterior skull elements are also present here.

Figure 3. The pectoral region of Langobardisaurus (MCSNB 2883) with DGS color overlays. Compare to Figure 4 for identification of pectoral elements. Anterior skull elements are also present here. Premaxillae and sternum are both yellow. Scapulae are blue. Coracoids are violet. Clavicles are green. Interclavicle is tan. Ribs are red. The tiny metacarpals are still attached to the end of the ulna and radius (amber and green).

The coincidence of the interclavicle, clavicle and sternum
in Langonbardisaurus (Fig. 4) and other fenestrasaurs like Cosesaurus and Longisquama is the precursor structure to the pterosaur sternal complex, seen only in this clade within the entire Tetrapoda.

Figure 5. Langobardisaurus (MCSNB 2883) pectoral girdle in left lateral and ventral views.

Figure 4. Langobardisaurus (MCSNB 2883) pectoral girdle in left lateral and ventral views.

References
Muscio G 1997. Preliminary note on a specimen of Prolacertiformes (Reptilia) from the Norian (Late Triassic) of Preone (Udine, north-eastern Italy). Gortania – Atti del Museo Friulano di Storia Naturale 18:33-40
Renesto S 1994. A new prolacertiform reptile from the Late Triassic of Northern Italy. Rivista di Paleontologia e Stratigrafia 100(2): 285-306.
Renesto S and Dalla Vecchia FM 2000. The unusual dentition and feeding habits of the Prolacertiform reptile Langobardisaurus (Late Triassic, Northern Italy). Journal of Vertebrate Paleontology 20: 3. 622-627.
Renesto S, Dalla Vecchia FM and Peters D 2002. Morphological evidence for bipedalism in the Late Triassic Prolacertiform reptile Langobardisaurus. Senckembergiana Lethaea 82(1): 95-106.
Saller F, Renesto S, Dalla Vecchia FM 2013. First record of Langobardisaurus (Diapsida, Protorosauria) from the Norian (Late Triassic) of Austria, and a revision of the genus. Neues Jahrbuch für Geologie und Paläontologie. 268 (1): 89–95. doi:10.1127/0077-7749/2013/0319
Wild R 1980. Tanystropheus (Reptilia: Squamata) and its importance for stratigraphy. Mémoires de la Société Géologique de France, N.S. 139:201–206.

uninisubria/Langobardisaurus
wiki/Langobardisaurus

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A fourth Langobardisaurus: Saller et al. 2013

Not sure how I missed this five years ago,
knowing my fondness and fascination with the Tritosauria. I learned about the following paper while reading Franco Saller’s doctoral thesis on Macrocnemus and its allies. (More on this later).

Saller et al. 2013
describe a fourth Langobardisaurus (Late Triassic, Norian; Figs. 1-2; P10121), wrongly described as a protorosaurian reptile. Langobardisaurs are tritosaur lepidosaurs in the large reptile tree (LRT, 1326) which tests and includes more taxa.

Figure 1. Langobardisaurus #4, P10121, in situ with bones identified using the DGS method. Reconstruction in figure 2.

Figure 1. Langobardisaurus #4, P10121, in situ with bones identified using the DGS method. Reconstruction in figure 2. Note the sprawling lepidosaur femora. The pectoral girdle is shown in situ. Colors match reconstruction in figure 2.

Saller et al. report: “Reappraisal of all the specimens assigned to the genus Langobardisaurus reveals no significant differences between L. pandolfii and L. tonelloi, allowing to consider the latter as a junior synonym of the former.” I haven’t tested more than one Langobardisaurus in phylogenetic analysis…yet… but I will as I wonder about the validity of this Saller et al. conclusion, which does not appear to be validated given the variety present in these three reconstructions (Fig. 2).

Addendum December 4, 2018:
I just added three new Langobardisaurus specimens to the LRT. The P10121 specimen is basal, nesting between the small Macrocnemus BES SC111 specimen and Cosesaurus, but definitely in the lineage of derived langobardisaurs and having a few derived traits itself. The Langobardisaurus holotype MCSNB 2883 splits next. The MFSN 1921 specimen nests with the MCSNB 4860 specimen (Fig. 2). 

Figure 1. Four Langobardisaurus specimens compared to scale. Contra Saller et al. 2013, these four specimens do not appear to be conspecific.

Figure 2. Four Langobardisaurus specimens compared to scale. Contra Saller et al. 2013, these four specimens do not appear to be conspecific.

Historically,
Langobardisaurus was the first specimen in which tracing elements in a photo using a mouse on a computer monitor revealed more than was observed firsthand and published in the original paper. Specifically the overlooked skull and cervicals were traced hiding beneath the torso (Fig. 3).

Langobardisaurus pandolfi

Figure 3. Langobardisaurus pandolfi referred specimen, MCSNB 4860.

The Langobardisaurus pectoral girdle
is transitional between the walking morphology of HuehuecuetzpalliMacrocnemus and flapping morphology of Cosesaurus (Fig. 4), as we learned earlier here. The P10121 specimen exposes the wide sternum, strap-like scapulae, disc-like coracoids and cruciform interclavicle first seen in L. tonneloi (Figs. 4, 5).

Three pectoral girdles demonstrating the evolution of the elements from the plesiomorphic basal lizard, Huehuecuetzpalli through Langobardisaurus tonelloi to the basal fenestrasaur, Cosesaurus.

Figure 4. Three pectoral girdles demonstrating the evolution of the elements from the plesiomorphic basal lizard, Huehuecuetzpalli through Langobardisaurus tonelloi to the basal fenestrasaur, Cosesaurus.

Bipedal Langobardisaurus
Like aquatic Tanystropheus and flapping Cosesaurus, Langobardisaurus was often bipedal, using its long neck as a survival advantage. Like Cosesaurus, this specimen of Langobardisaurus has prepubes (Fig. 6), which add femoral muscle anchors to the pelvis.

Figure 5. Pectoral girdle of the fourth Langobardisaurus in situ. Blue-scapulae. Yellow-sternum. Tan-interclavicle. Violet-coracoid. Green-humerus.

Figure 5. Pectoral girdle of the fourth Langobardisaurus in situ. Blue-scapulae. Yellow-sternum. Tan-interclavicle. Violet-coracoid. Green-humerus.

Figure 6. Pelvic area in the fourth Langobardisaurus. Cyan-ischia. Deep green-pubes. Indigo-prepubes. Red-sacrals. Tan-ilia.

Figure 6. Pelvic area in the fourth Langobardisaurus. Cyan-ischia. Deep green-pubes. Indigo-prepubes. Red-sacrals. Tan-ilia. Also note the feathery soft tissue in orange and lime yellow. For those interested in the DGS method, this is how it works.

Figure 7. Fourth Langobardisaurus reconstruction.

Figure 7. Fourth Langobardisaurus P10121 reconstruction based on DGS tracings in figure 1.

References
Muscio G 1997. Preliminary note on a specimen of Prolacertiformes (Reptilia) from the Norian (Late Triassic) of Preone (Udine, north-eastern Italy). Gortania – Atti del Museo Friulano di Storia Naturale 18:33-40.
Renesto S 1994. A new prolacertiform reptile from the Late Triassic of Northern Italy. Rivista di Paleontologia e Stratigrafia 100(2): 285-306.
Renesto S and Dalla Vecchia FM 2000. The unusual dentition and feeding habits of the Prolacertiform reptile Langobardisaurus (Late Triassic, Northern Italy). Journal of Vertebrate Paleontology 20: 3. 622-627.
Renesto S and Dalla Vecchia FM 2007. A revision of Langobardisaurus rossii Bizzarini and Muscio, 1995 from the Late Triassic of Friuli (Italy)*. Rivista di Paleontologia e Stratigrafia 113(2): 191-201. online pdf
Renesto S, Dalla Vecchia FM and Peters D 2002. Morphological evidence for bipedalism in the Late Triassic Prolacertiform reptile Langobardisaurus. Senckembergiana Lethaea 82(1): 95-106.
Saller F, Renesto S and Dalla Vecchia FM 2013. First record of Langobardisaurus (Diapsida, Protorosauria) from the Norian (Late Triassic) of Austria, and a revision of the genus. Neues Jahrbuch für Geologie und Paläontologie 268(1):83–95.
Wild R 1980. Tanystropheus (Reptilia: Squamata) and its importance for stratigraphy. Mémoires de la Société Géologique de France, N.S. 139:201–206.

uninisubria/Langobardisaurus
wiki/Langobardisaurus
http://reptileevolution.com/langobardisaurus.htm

Pre-elasmosaurs out-competed tanystropheids as passive vertical predators

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

Figure 1. Albertonectes, Tanystropheus and Dinocephalosaurus to scale.

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

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

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

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

Convergent skull traits in vertical feeders:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Leaping lizards in the Late Triassic

Lockley 2006
documented paired, digitigrade, four-toed, accelerating, ‘swimming’ tracks (ichnogenus: Gwyneddichnium; Figs. 1, 2) in the Late Triassic. Tanytrachelos (Figs. 1, 2) was and is considered a good match, but hopping through thinly retreating surf seems to be a better solution. Tanytrachelos is a tritosaur lepidosaur, hence, a ‘leaping lizard’.

Figure 1. Gwyneddichnium tracks (note the acceleration). Along with a to scale Tanytrachelos and Tanytrachelos pes. Note digit 1 does not impress.

Figure 1. Gwyneddichnium tracks CU 159.10 (note the acceleration). Along with a to scale Tanytrachelos and Tanytrachelos pes. Note digit 1 does not impress. As in Cosesaurus, digit 1 impressed only rarely and then only as a point.

Like Cosesaurus and other higher tritosaurs, 
Tanytrachelos was digitigrade and facultatively bipedal. Hopping through thinly retreating surf is more likely based on matching the body to the tracks. So we don’t have to imagine the front half floating or swimming underwater to make the hind feet simultaneously kick to make side-by-side tracks.

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

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

Running and arm flapping in Cosesaurus
led to flapping flight in pterosaurs (Fig. 3).

Figure 1. Cosesaurus flapping - fast. There should be a difference in the two speeds. If not, apologies. Also, there should be some bounce in the tail and neck, but that would involve more effort and physics.

Figure 3. Click to enlarge and animate. Cosesaurus flapping – fast. There should be a difference in the two speeds. If not, apologies. Also, there should be some bounce in the tail and neck, but that would involve more effort and physics.

Gwyneddichnium and Rotodactylus tracks
are from trackmakers (Fig. 4)in the same clade of Tritosauria.

Cosesaurus matched to Rotodactylus from Peters 2000.

Figuure 4. Cosesaurus matched to Rotodactylus from Peters 2000.

Another relative of Tanytrachelos, Langobardisaurus,
(Fig. 5) has been considered bipedal by prior authors (Renesto, et al. 2002).

Figure 4. Langobardisaurus bipedal.

Figure 5. Langobardisaurus bipedal.

References
Lockley M 2006. Observations on the ichnogenus Gwyneddichnium and Gwyneddichnium-like footprints and trackways from the Upper Triassic of the western United States. New Mexico Museum of Natural History and Science, Bulletin 37:170–175.
Peters D 2000. Description and Interpretation of Interphalangeal Lines in Tetrapods. Ichnos 7:11-41.
Renesto S, Dalla Vecchia FM and Peters D 2002. Morphological evidence for bipedalism in the Late Triassic Prolacertiform reptile Langobardisaurus. Senckembergiana Lethaea 82(1): 95-106.

 

Revisiting the pes of Pectodens

Earlier we looked at Pectodens, a long-necked tritosaur that nests at the base of the tanystropheids + langobardisaurs and the fenestrasaurs, which ultimately gave rise to pterosaurs.

Metacarpal 5 is the problem (Fig. 1).

Figure 1. The right pes of Pectodens in situ (left), sans the matrix (right), and rearranged to match sister taxa (center). The question is: is the rearrangement valid?

Figure 1. The right pes of Pectodens in situ (left), sans the matrix (right), and rearranged to match sister taxa (center). The question is: is the rearrangement valid?

 

Which bone is metacarpal 5?
Is it the long bone similar to metacarpal 4? That would make sense with most taxa, except Pectodens nests with other long-necked taxa, like Langobardisaurus and Tanystropheus. In those taxa metacarpal 5 is short and pedal 5.1 is metapodial (= very long).

Did taphonomy change things?
Or do we trust phylogenetic bracketing?

One more thing…
If the long bone is the metacarpal, then the phalangeal count matches sister taxa (4 phalanges). If the short bone is the metacarpal, then there is one extra phalanx. Did the preparator add a bone? Or did this taxon have an extra bone?

And take a look
at the width of the tibia + fibula. It’s the right width if the short bone is metacarpal 5. The width is not quite wide enough if the long bone is metacarpal 5.

Sometimes
you have to make a decision in paleontology. Sometimes you have to point your finger at a preparator’s mistake. Sometimes you make the mistake when you use your brain OR when you accept the data as presented.

What to do… what to do…

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

Figure 2. Pectodens reconstructed using the original tracings of the in situ fossil in Li et al. 2017.

Here’s what I wrote a while back
at ReptileEvolution.com:

Pectodens zhenyuensis (Li et al. 2017; IVPP V18578; Anisian, Middle Triassic; 38cm in length) was originally considered to be a diapsid and a possible protorosaur. Here Pectodens nests between Macrocnemus and Langobardisaurus. 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.

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

Figure 3. Pectodens skull traced using DGS techniques and reassembled.

With the short metacarpal 5
Pectodens cleanly nests with fewer autapomorphies at the base of the Langonbardisaurus/Tanystropheus clade.

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

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