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

Plotosaurus enters the LRT

Figure 1. Skull of Plotosaurus. Note the mislabeling of the right supratemporal as a squamosal.

Figure 1. Skull of Plotosaurus. Note the mislabeling of the right supratemporal as a squamosal. The posterior frontal processes are atypical for lizards.

Plotosaurus benisoni (originally Kolposaurus, preoccupied; Camp 1942, 1951; Late Cretaceous; 9m) is a large mosasaur (Lepidosauria, Squamata, Scleroglossa) with relatively small flippers and a large tail fin. It enters the LRT as a sister to Tylosaurus. The nasals, tiny in Tylosaurus, are absent in Plotosaurus.

Figure 2. Plotosaurus from Camp 1951 with hypothetical body outline.

Figure 2. Plotosaurus from Camp 1951 with hypothetical body outline.

References
Camp CL 1942. California Mosasaurs. Memoirs of the University of California 13:1-68.
Camp CL 1951. Plotosaurus, a new generic name for Kolposaurus Camp, preoccupied. Journal of Paleontology 25:822.

wiki/Plotosaurus

4 nostrils in Chamaeleo?

The skull of the smooth chameleon,
Chamaeleo laevigatus (Figs. 1, 2), has two extra holes in the anterodorsal plane of its rostrum (Fig. 1). Despite appearances, the holes visible in top view are not nostrils.

Figure 1. The chameleon Trioceros jacksonii colored using DGS. The sutures are difficult to see in the original skull, much easier in the colorized tracing.

Figure 1. The chameleons Chamaeleo and Trioceros. Note the lateral nostrils on both taxa. Chamaeleo has two more openings in dorsal view.  Not sure if Trioceros was the same. Note the giant pterygoids on Chamaeleo. The prefrontal and postfrontal are in contact. The premaxilla is tiny in ventral view.

The Chamaeleo rostrum
is angled at about 50º from the jawline. Given just the skull, you might think those openings in dorsal view are nostrils. With skin and scales on (Fig. 2), the nostrils are located on the lateral plane, as in other chameleons, like Trioceros (Fig. 1), surrounded by traditional circumnarial bones.

Figure 2. Chamaeleo laevigatus invivo. Red arrow points to external naris.

Figure 2. Chamaeleo laevigatus invivo. Red arrow points to external naris.

Diaz and Trainer 2015 published
some nice images of chameleon hands and feet, colorized here (Fig. 3) for additional clarity. The metacarpals and metatarsals are the bones that radiate. The phalanges are all vertical here.

Figure 3. The manus and pes skeleton of a chameleon from Diaz et al. 2016 with colors added and the second from left image relabels the fingers, correcting a typo.

Figure 3. The manus and pes skeleton of a chameleon from Diaz et al. 2015 with colors added and the second from left image relabels the fingers, correcting a typo. Manual 1 has only two phalanges. The metacarpals and metatarsals open horizontally in these images. Note the ankle elements are not co-ossified.

References
Diaz RE Jr. and Trainor PA 2015. Hand/foot splitting and the ‘re-evolution’ of mesopodial skeletal elements during the evolution and radiation of chameleons. BMC Evolutionary Biology201513:184.

wiki/Smooth_chameleon
digimorph.org/Chamaeleo_laevigatus/
Chamaeleo laevigatus GRAY, 1863″. The Reptile Database

Early Cretaceous stem chameleon/horned lizard

Unnamed stem chameleon (Daza et al. 2016; Early Cretaceous, 1.2cm in length; JZC Bu154; Fig. 1) is a tiny neonate preserved in amber. It also nests basal to horned lizards like Phrynosoma, in the large reptile tree (LRT, 1089 taxa). Note the long, straight hyoid forming the base of the shooting tongue. The split fingers and toes of extant chameleons had not yet developed in this taxon. Found in amber, this newborn lived in a coniferous forest.

Figure 1. The Early Cretaceous stem chameleon/horned lizard found amber. Snout to vent length is less than 11 mm. Much smaller than a human thumbnail.

Figure 1. The Early Cretaceous stem chameleon/horned lizard found amber. Snout to vent length is less than 11 mm. Much smaller than a human thumbnail. Insitu fossil from Daza et al. 2016,  colorized and reconstructed here. At a standard 72 dpi screen resolution, this specimen is shown 10x actual size.

This specimen further cements
the interrelationship of arboreal chameleons and their terrestrial sisters, the horned lizard we looked at earlier with Trioceros and Phyrnosoma in blue of this cladogram (Fig. 2) subset of the LRT.

Figure 3. Subset of the LRT focusing on the neonate stem chameleon/horned lizard.

Figure 2. Subset of the LRT focusing on the neonate stem chameleon/horned lizard.

Figure 6. Phyronosoma, the horned lizard of North America.

Figure 3. Phyronosoma, the horned lizard of North America.

Figure 2. Trioceros jacksonii overall. Size is 12 inches (30 cm) from tip to tip.

Figure 4. Trioceros jacksonii overall. Size is 12 inches (30 cm) from tip to tip.

References
Daza JD et al. 2016. Mid-Cretaceous amber fossils illuminate the past diversity of tropical lizards. Sci. Adv. 2016; 2 : e1501080 4 March 2016

A deeper extension for the Lepidosauria

By definition
the Lepidosauria includes Rhynchocelphalia (Sphenodon), Squamata (Iguana), their last common ancestor and all descendants. By this definition pterosaurs and kin are lepidosaurs because they nest between rhychocephalians and iguanids in a traditionally unrecognized clade the Tritosauria (Fig. 1).

Figure 1. Subset of the LRT focusing on the Lepidosauria. Now the drepanosaur clade lumps with the rhynchocephalians in the crown group. Extant lepidosaurs are in gray.

Figure 1. Subset of the LRT focusing on the Lepidosauria. Now the drepanosaur clade lumps with the rhynchocephalians in the crown group. Extant lepidosaurs are in gray.

While reviewing
the large reptile tree (LRT, 1087 taxa, subset Fig. 1) following the addition of Avicranium, the base of the Rhynchocephalia  shifted back to include Jesairosaurus, and the drepanosaursSaurosternon and Palaegama, which formerly nested as outgroup Lepidosauriformes now nest basal to the tritosaurs, pro-squamates and squamates within the Lepidosauria, based on the traditional definition.

With this change
the non-lepidosaur Lepidosauriformes are reduced to just the glider clade, Coletta, Paliguana, and Sophineta, taxa with a diapsid skull architecture. These remain stem lepidosaurs. The membership of the clade Lepidosauriformes do not change.

Remember,
despite their diapsid temporal morphology, these are not members of the clade Diapsida, which is restricted to Archosauromorph ‘diapsids’ only. Petrolacosaurus is a basal member of the monophyletic Diapsida. The clade name ‘Lepidosauriformes’ includes all lepidosauromorphs with upper and lateral temporal fenestrae. If you know any traditional paleontologists who still think lepidosaurs are related to archosaurs, please show them the LRT.

Once a definition for a clade is made
then the next step is to see which taxa fall under than definition… and then to see if that definition is a junior synonym for a previously published definition based on clade membership. Remember, traditional traits may not give you monophyly, but phylogenetic analysis always will.

And
yes, I do review all the scores in the LRT and announce updates when they are made.

 

Nycteroleter: which data is better?

Nycteroleter
(Efremov 1938; Middle Permian) was just added to the large reptile tree (LRT, 1035 taxa). The GIF movie shown here (Fig. 1) shows the data I had to work with. Note the differences.

Figure 1. Nycteroleter inept us and the two data sources used in scoring this taxon. The one with the smaller premaxilla in dorsal view nests with fewer autapomorphies in the LRT.

Figure 1. Nycteroleter inept us and the two data sources used in scoring this taxon. The one with the smaller premaxilla in dorsal view nests with fewer autapomorphies in the LRT.

This is not a case of ‘who do you trust?’
because we can figure out which is the more accurate skull by using the LRT.

I let the LRT choose which dataset
had fewer autapomorphies, since I had no direct access to fossils. Note the less accurate skull also mislabels the cranial corners as tabulars. They should be labeled supratemporals. Nycteroleter nests with Nyctiphruretus in the LRT.

If I’m wrong, 
I’ll make the changes if and when better data comes in.

References
Efremov JA 1938. Some new Permian reptiles of the U.S.S.R. Comptes Rendus (Doklady), 19: 771–776.

Shringasaurus: new rhynchocephalian lepidosaur with horns

Sengupta, Ezcurra and Bandyopadhyay 2017 bring us
a new, very large, horned rhynchocephalian lepidosaur, Shringasaurus (Fig. 1). Unfortunately, that’s not how the Sengupta team nested it (due to the sin of taxon exclusion, see below). Even so, there is consensus that the new taxon is closely related to the much smaller Azendohsaurus (Fig. 1).

Figure 1. Shringasaurus to scale with Azendohsaurus. Line art modified from Sengupta et al. Color added here. Note the anterior lappet of the maxilla over the premaxilla. The supratemporal  (dark green) remains.

Figure 1. Shringasaurus to scale with Azendohsaurus. Line art modified from Sengupta et al. Color added here. Note the anterior lappet of the maxilla over the premaxilla. The supratemporal  (dark green) remains.

From the abstract:
“The early evolution of archosauromorphs (bird- and crocodile-line archosaurs and stem-archosaurs) represents an important case of adaptive radiation that occurred in the aftermath of the Permo-Triassic mass extinction. Here we enrich the early archosauromorph record with the description of a moderately large (3–4 m in total length), herbivorous new allokotosaurian, Shringasaurus indicus, from the early Middle Triassic of India. The most striking feature of Shringasaurus indicus is the presence of a pair of large supraorbital horns that resemble those of some ceratopsid dinosaurs. The presence of horns in the new species is dimorphic and, as occurs in horned extant bovid mammals, these structures were probably sexually selected and used as weapons in intraspecific combats. The relatively large size and unusual anatomy of Shringasaurus indicus broadens the morphological diversity of Early–Middle Triassic tetrapods and complements the understanding of the evolutionary mechanisms involved in the early archosauromorph diversification.”

Allokotosauria
Shringasaurus was nested in the clade, Allokotosauria, According to Wikipedia, “Nesbitt et al. (2015) defined the group as a  containing Azendohsaurus madagaskarensis and Trilophosaurus buettneri and all taxa more closely related to them than to Tanystropheus longobardicus, Proterosuchus fergusi, Protorosaurus speneri or Rhynchosaurus articeps.” This definition was based on the invalidated hypothesis that rhynchosaurs and allokotosaurs were close to the base of the Archosauriformes as the addition of more taxa will demonstrate. Basically this clade equals Trilophosaurus, Azendohsaurus and now Shringasaurus. In the large reptile tree (LRT, 1049 taxa) this clade nests between Sapheosaurus + Notesuchus and Mesosuchus + Rhynchosauria all nesting within Sphenodontia (=  Rhynchocephalia), so they are all lepidosaurs. All you have to do is add pertinent taxa to make this happen in your own phylogenetic analysis.

Figure 2. Scene from the 1960 film, The Lost World, featuring a giant iguana with horns added presaging the appearance of Shringasaurus.

Figure 2. Scene from the 1960 film, The Lost World, featuring a giant iguana with horns added presaging the appearance of Shringasaurus.

Coincidentally the 1960 film,
The Lost World featured an iguana made up with horns similar to those of Shringasaurus.

References
Sengupta S, Ezcurra MD and Bandyopadhyay S 2017. A new horned and long-necked herbivorous stem-archosaur from the Middle Triassic of India. Nature, Scientific Reports 7: 8366 | DOI:10.1038/s41598-017-08658-8 online here.

No Wiki page yet.

Tulerpeton: transitional from Ichthyostega to Eucritta

This post was updated February 24, 2017, after new data on Tulerepton became available. And again on December 13, 2017. 

This latest nesting 
of the former basal tetrapod, Tulerpeton (Fig. 2), as a Devonian transitional taxon leading to the Amphibia, the Reptilia and the Seymouriamorpha in the large reptile tree (1134 taxa) was both anticipated (Fig. 1) and welcome.

As you may recall…
Middle Devonian tetrapod trackways (preceding and coeval with the basal bony fish Cheirolepis and the lobe fins Eusthenopteron and Osteolepis) seemed anachronistic when first announced. But it’s all coming together now. And this new nesting adds precious time for evolution to produce the variety of amphibian-like reptiles present in the Viséan, still awaiting consensus confirmation of their reptilian status.

Figure 1. The nesting of Tulerpeton in the Latest Devonian, at the base of the Lepidosauromorpha.

Figure 1. The nesting of Tulerpeton in the Latest Devonian, at the base of the Lepidosauromorpha. This taxon was added to this graphic that was published online in August 2016.

According to Wikipedia
Tulerpeton curtum
(Lebedev 1984, Fammenian, Latest Devonian, 365 mya; Fig. 1) is “one of the first true tetrapods to have arisen.” It was distinct from less derived Acanthostega and Ichthyostega by a strengthened limb structure. It was also half to an eighth the size of these basal tetrapods. A fragmented skull is known for Tulerpeton, but the only fragment I’ve seen is a vague round premaxilla on small reconstructions. Both the manus and pes have 6 digits, all provided with clawed unguals. (NOTE ADDED MARCH 6, 2017: The pes has only five digits after a fresh reconstruction)

FIgure 1. Tulerpeton compared to Eldeceeon.

FIgure 2. Tulerpeton compared to similarly-sized Eldeceeon. The loss of one digit in the manus and pes occurred between the Fammenian and Viséan.

Tulerpeton lived in shallow marine waters.
Little is known of this Eldeceeon-sized specimen, but the limbs and pectoral girdle are fairly well preserved. And these were enough to nest it between Ichthyostega and Eucritta among 1133 taxa in the LRT.

Coates and Ruta 2001 report:
“The most taxon-inclusive crown hypothesis incorporates the hexadactylous Late Devonian genus Tulerpeton as a basal stem amniote, thereby pegging the lissamphibian amniote divergence to a minimum date of around 360 Ma.” So there were early rumors. Only taxon exclusion prevented prior workers from recovering the reptile relationship earlier, no doubt due to the six fingers and toes on this putative basal tetrapod.

The loss of the sixth digit
occurred more than once, just as the later loss of a fifth digit occurred more than once. We should look for taxa with six fingers at the base of the Reptilomorpha and Seymouriamorpha — unless Tulerpeton developed a sixth finger on its own.

Phylogenetic analysis
originally placed Tulerpeton near the base of reptilomorphs, like Proterogyrinus and Eoherpeton. Later workers nested it as a more basal member of the Tetrapoda, between Acanthostega and Greererpeton.

Here
those long, clawed fingers and toes, and the individual proportions of the metapodials and phalanges nested Tulerpeton between Ichthyostega and Eucritta in the LRT.

Major studies do not yet recognize the reptile status
of Gephyrostegus. Hopefully someone will add them and Eldeceeon to a future taxon list to confirm or refute the present findings.

References
Coates MI and Ruta M 2001 (2002). Fins to limbs: What the fossils say. Evolution & Development 4(5): 390–401.
Lebedev OA 1984. The first find of a Devonian tetrapod in USSR. Doklady Akad. Navk. SSSR. 278: 1407–1413.
Lebedev OA and Clack JA 1993. Upper Devonian tetrapods from Andreyeva, Tula Region, Russia. Paleontology36: 721-734.
Lebedev OA and Coates MI 1995. postcranial skeleton of the Devonian tetrapod Tulerpeton curtum Lebedev. Zoological Journal of the Linnean Society. 114 (3): 307–348.

wiki/Tulerpeton

Magnuviator, another basal scleroglossan.

A recent paper brings us
a Late Cretaceous “iguanomorph,” Magnuviator ovimonsensis (DeMar et al. 2017). It nested with Saichangurvel originally and here in the LRT, but both nest in the LRT with Acanthodactylus at the base of the Scleroglossa, not within the Iguania. The authors provided illustrations of the in situ fossils which I have restored to the in vivo configuration (Fig. 1) more or less.

Figure 1. Magnuviator ovimonsensis in situ from DeMar et al. 2017) and in vivo.

Figure 1. Magnuviator ovimonsensis in situ from DeMar et al. 2017) and in vivo.

DeMar et al.
added Magnuviator to the cladogram provided by Conrad 2008. Earlier we looked at the problems therein and in other earlier studies. As in the earlier Saichangurvel study, Magnuviator nests close enough to the clade Iguania that there are no intervening taxa.

References
DeMar Jr DG, Conrad JL, Head JJ, Varricchio DJ and Wilson GP 2017. A new Late Cretaceous iguanomorph from North America and the origin of New World
Pleurodonta (Squamata, Iguania). Proc. R. Soc. B 284: 20161902.

Lacerta: where is the upper temporal fenestra?

Lacerta viridis (Fig. 1) is a common extant lizard that has more skull bones than is typical for most tetrapods. It also loses the upper temporal fenestra found in other lizards, by posterior expansion of the postfrontal.

Figure 1. Lacerta viridis skull from Digimorph.org and used with permission. Here the enlargement of the postfrontal basically erases the former upper temporal fenestra. Several novel ossifications appear around the orbit and cheek.

Figure 1. Lacerta viridis skull from Digimorph.org and used with permission. Here the enlargement of the postfrontal basically erases the former upper temporal fenestra. Several novel ossifications appear around the orbit and cheek.

This Digimorph.org image
was colorized in an attempt at understanding the skull bones present here. The extant Lacerta nests with the larger extinct Eolacerta in the large reptile tree (918 taxa).

40 species are known of this genus.
Fossils are known from the Miocene (Čerňanský 2010). The tail can be shed to evade predators. This lizard is an omnivore. The curled quadrate frames an external tympanic membrane (eardrum). With the premaxillae fused, Lacerta has nine premaxillary teeth, with one in the center.

Not sure why this lizard developed extra skull bones.
It is found in bushy vegetation at woodland and field edges, and is not described as a burrower or a head basher.

Other diapsid-grade reptiles that nearly or completely lose the upper temporal fenestra include:

  1. Mesosaurus
  2. Chalcides
  3. Acanthodactylus
  4. Phyrnosoma
  5. Minmi

References
Čerňanský A 2010. Earliest world record of green lizards (Lacertilia, Lacertidae) from the Lower Miocene of Central Europe. Biologia 65(4): 737-741.
Linnaeus C 1758.
Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.

Lacerta viridis images online
wiki/Lacerta