The vampire pterosaur has a new sister: Daohugoupterus

Cheng et al. (2014)
present a new small, late Jurassic pterosaur, Daohugoupterus. They were not quite sure what it was, assigning it to Pterosauria incerta sedis. The specimen is represented by an articulated skeleton lacking hind limbs, the anterior skull and two proximal wing phalanges (Fig. 1). Wing tip soft tissue was preserved. I believe the ulna and radius are just beneath the surface based on the positions of the humerus and carpus/metacarpus. The rest of the wing is likely twisted beneath these elements as the distal two wing phalanges frame the soft tissue.

Figure 1. Click to enlarge. Daohugoupterus in situ, colorized (left) and as originally traced (right). You'll note that DGS pulled out more details than firsthand tracing.

Figure 1. Click to enlarge. Daohugoupterus in situ, colorized (left) and as originally traced (right). You’ll note that DGS pulled out more details than firsthand tracing.

From their abstract:
“Daohugou is an important locality of the Jurassic Yanliao Biota, where
only two pterosaurs have been described so far (Jeholopterus and
Pterorhynchus). Here we report a new genus and species, Daohugoupterus
delicatus gen. et sp. nov. (IVPP V12537), from this region, consisting
of a partial skeleton with soft tissue. The skull is laterally
compressed, differing from Jeholopterus. The antorbital fenestra is
larger than in Pterorhynchus. The upper temporal fenestra is unusually
small. The short cervical vertebrae bearing cervical ribs indicate
that it is a non-pterodactyloid flying reptile. The sternal plate is
triangular, being much wider than long. The deltopectoral crest of
humerus is positioned proximally and does not extend further down the
shaft, a typical feature of basal pterosaurs. Daohugoupterus also
differs from the wukongopterids and scaphognathids from the Tiaojishan
Formation at Linglongta, regarded to be about the same age as the
Daohugou Bed. The new specimen increases the Jurassic
non-pterodactyloid pterosaur diversity of the Yanliao Biota and is the
smallest pterosaur from Daohugou area so far.”

DGS
Digital Graphic Segregation was used to pull details out of the skeleton. While the original paper described small upper temporal fenestra (that are indeed there) the figure did not show this detail. No skull bones were identified. The vertebrae were outlined without details. Color tracing and reconstruction (fig. 2) help bring this specimen ‘back to life.’ The length of the rostrum is unknown, but after phylogenetic analysis nesting with Jeholopterus, the rostrum was reconstructed like it’s sister taxon.

Reconstruction
A reconstruction of all available elements resulted in a sister to Jeholopterus, sharing many traits including the strong reduction of anterior cervical vertebrae, robust cervical vertebrae posteriorly, wide ribs creating a pancake-like torso, and a fragile skull with very large orbit (Fig. 2). Notably, Jeholopterus was a contemporary from the same Late Jurassic formation.

Figure 2. Click to enlarge. Daohugoupterus reconstructed.

Figure 2. Click to enlarge. Daohugoupterus reconstructed.

If you take a bone-by-bone survey
of the the DGS tracing vs. the original tracing (Fig. 1), you’ll find many differences. This is a difficult fossil and the accuracy of my tracings depending to a large part on testing each part within an evolving reconstruction (Fig. 3). Attempting reconstructions of roadkill pterosaurs is something conventional paleontologists are loathe to do, and they never ask me to help. Hence this blog.

Figure 1. Jeholopterus in lateral view. Note the extreme length of the dermal fibers, unmatched by other pterosaurs.

Figure 3. Jeholopterus in lateral view. Note the wide ribs.

In a side-by-side comparison (Fig. 4)
Jeholopterus and Daohugoupterus do share many traits and are roughly the same size. Daohugoupterus does not have the robust limbs and surgically curved claws that Jeholopterus has, but Daohugoupterus does have enormous eyes, probably for night vison. They share a wider than deep torso which enables them to cram their bellies, but still keep an aerodynamic disc-like shape (also see Sharovipteryx for something similar). They also share a very robust neck that gets very gracile close to the skull. I presume this gives both pterosaurs a wider range of motion at the skull/neck juncture. But why does most of the neck have to be stronger than the dorsal vertebrae?

Figure 3. Jeholopterus and Daohugoupterus in side-by-side comparison to scale. The wings were relatively short in Daohugoupterus and the pelvis was small. The skull was relatively narrower, but the torso was just as broad.

Figure 3. Jeholopterus and Daohugoupterus in side-by-side comparison to scale. The wings were relatively short in Daohugoupterus and the pelvis was small. The skull was relatively narrower, but the torso was just as broad.

On a side note
Experiment.com has accepted by submission and my first crowd-source funding project has started today. See details at:
https://experiment.com/projects/the-reptile-evolution-project

References
Cheng X, Wang X, Jiang S and Kellner AWA 2014. Short note on a non-pterodactyloid pterosaur from Upper Jurassic deposits of Inner Mongolia, China. Historical Biology (advance online publication) DOI:10.1080/08912963.2014.974038

 

Another odd rhynchocephalian: Ankylosphenodon

You don’t find very much
about Ankylosphenodon pachyostosus (Reynoso 2000) online, even though it is odd and known by a complete skeleton. It’s a basal rhynchocephalian, nesting between Gephyrosaurus and Marmoretta in the large reptile tree. The long torso and tail, along with those small limbs gives credence to the possibility that Marmoretta and Megachirella were similarly equipped (they are known from a skull and anterior torso only) at the base of the Pleurosauridae, which we looked at earlier here.

Figure 1. Ankylosphenodon pachyostosus. Click to enlarge. This long-bodied taxon nests at the base of the pleurosaurs, Marmoretta and Megachirella.

Figure 1. Ankylosphenodon pachyostosus. Click to enlarge. This long-bodied taxon nests at the base of the pleurosaurs, Marmoretta and Megachirella.

Middle Cretaceous, Mexico, considered an herbivore. Martinez et al. 2013) nested Ankylosphenodon between Sphenodon and Clevosaurus and Sphenotitan, but Marmoretta, Megachirella, and Gephyrosaurus were not included in their taxon list and neither were a host of derived rhynchocephalians. `

From Wikipedia (translated from Italian, I think).
“This animal had a body rather robust, with short legs positioned at the sides of the body and a skull from the remarkable features. These included a set of teeth unusual: there were, in fact, long teeth roots open, deeply “embedded” in the jaw and placed in the vicinity of the channel Meckel . Another feature dell’anchilosfenodonte was given by significant thickening of the ribs and vertebrae ( pachiostosi ), a feature that normally is found in aquatic vertebrates.”

References
Reynoso VH 1996. Early Cretaceous Lepidosaurs (Reptilia: Diapsid) from Central Mexico and the Phylogeny of Lepidosauromorphs. 369 pp. Unpublished PhD Thesis, McGill University, Montreal, Canada.
Reynoso VH 2000. An unusual aquatic sphenodontian (Reptilia: Diapsida) from the Tlayua Formation (Albian), central Mexico. Journal of Paleontology 74:133-148.

Mea culpa. Azendohsaurus is a sister to the protorosaur Pamelaria.

Adding taxa to the large reptile tree (now up to 425 taxa and still not updated because updates are under review at academic publications) exposes ‘strange bedfellows’ (oddballs that don’t really fit within a topology). And yes, like everyone else, I make mistakes. But I also fix mistakes whenever I find them.

Earlier I nested Azendohsaurus with Trilophosaurus. That was an error. Re-examination re-nested Azendohsaurus with the derived protorosaur Pamelaria (Fig. 1).

Figure 1. Pamelaria compared to the skull of Azendohsaurus. The description of the postcrania of Azendohsaurus by Nesbitt et al. matches that of Pamelaria.

Figure 1. Pamelaria compared to the skull of Azendohsaurus. The description of the postcrania of Azendohsaurus by Nesbitt et al. matches that of Pamelaria.

Azendohsaurus has often been considered ‘bizarre’. It has been hard to nest. Originally (Detuit 1972) it was considered a dinosaur. Only the skull has been published, but post-crania is known and was described in an abstract (see below).

Pamelaria is a little off the map for most paleontologists, so that may be why it was not previously considered as a sister. The benefit of having 425 taxa to nest with, Azendohsaurus is going to find a >most< parsimonious node.

Figure 1. The skull and palate of Azendohsaurus, a sister to Pamelaria.

Figure 1. The skull and palate of Azendohsaurus, a sister to Pamelaria.

I discovered this new nesting by removing all the previous sister taxa among the rhynchocephalians, then running PAUP to see where Azendohsaurus would nest if it didn’t nest with Trilophosaurus and kin. It’s a good experiment you can do with any taxon. It even works with turtles and pterosaurs.

I also found a probable error in an online skull reconstruction of Azendohsaurus. Notes have been passed to Flynn, Nesbitt and Parrish. We’ll see what happens.

Figure 3. It looks like the prefrontal/lacrimal in the color photo was inverted. By rotating these elements  180 degrees (in grey tones), the odd lacrimal becomes the ascending process of the maxilla, exactly matching the more complete one.

Figure 3. It looks like the prefrontal/lacrimal in the color photo was inverted. By rotating these elements 180 degrees (in grey tones), the odd lacrimal becomes the ascending process of the maxilla, exactly matching the more complete one. Like Aznedohsaurus, Pamelaria also has a major process at the dorsal quadrate. The naris is not visible in lateral view. As in Pamelaria, the naris was likely dorsal. 

The post-crania has not been published, but an abstract appeared in 2013.
Nesbitt et al. (2013) report, Azendohsaurus madagaskarensis possessed an elongated neck, short tail, and stocky limbs. The manus and pes have unexpectedly short digits, terminating in large, recurved ungual phalanges. Together with the skull, knowledge of the postcranial skeleton elevates A. madagaskarensis to another highly apomorphic and bizarre Triassic archosauromorph.”

That sounds a lot like Pamelaria (Fig. 1), doesn’t it? We’ll see when it gets published.

References
Dutuit J-M 1972. Découverte d’un Dinosaure ornithischien dans le Trias supérieur de l’Atlas occidental marocain. Comptes Rendus de l’Académie des Sciences à Paris, Série D 275:2841-2844.
Flynn JJ, Nesbitt, SJ, Parrish JM, Ranivoharimanana L and Wyss AR 2010. A new species of Azendohsaurus (Diapsida: Archosauromorpha) from the Triassic Isalo Group of southwestern Madagascar: cranium and mandible”. Palaeontology 53 (3): 669–688. doi:10.1111/j.1475-4983.2010.00954.x .
Nesbitt, S, Flynn J, Ranivohrimanina L, Pritchard A and Wyss A 2013. Relationships among the bizarre: the anatomy of Azendohsaurus madagaskarensis and its implications for resolving early archosauromroph phylogeny. Journal of Vertebrate Paleontology abstracts 2013.

wiki/Azendohsaurus

Kallimodon(?) reconstructed

Figure 1. Kallimodon from WikiCommons.

Figure 1. Kallimodon from WikiCommons.

I found this purported Kallimodon specimen on WikiCommons and traced it out. The museum number is not available. If anyone knows it, please let me know. I can’t say if it is Kallimodon or not. I don’t have access to images of the holotype (1887-VI-I), or if I do (there are several specimens on Google), not one is identified as the holotype.

Figure 2. Kallimodon in situ after adjusting levels and a tracing.

Figure 2. Kallimodon? in situ after adjusting levels and a tracing. Possible eggs are in light blue on the in situ specimen. This specimen is small, only about 20 percent larger than pictured here.

Whatever the provence of this specimen, DGS enables details to be brought out, despite or because of crushing. There is a palate labeled Kallimodon, but it obvious comes from another specimen. And I can’t be sure it is the holotype without seeing the label.

Figure 3. Kallimodon reconstructed. This taxon, whether it is Kallimodon or not, nests with Sphenodon, but has distinct proportions.

Figure 3. Kallimodon? reconstructed. This taxon, whether it is Kallimodon or not, nests with Sphenodon, but has distinct proportions, with a small skull, long torso and long legs.

Though distinct from all other rhynchocephalians, this specimen nests with Sphenodon, the living rhynchocephalian. There is also some confusion regarding the naming and numbering of this taxon:

Etymology
Homoesaurus pulchellus Zittell, 1887
Kallimodon pulchellus (Zittell, 1887) Frickhinger 1994
Locality: Kelheim, Bayern (Bavaria) State, Germany.
Horizon: Solnhofen.
Age: Tithonian Stage, Upper Malm Epoch, Late Jurassic.

References
Cocude-Michel, M 1963.  Les rhynchocéphales et les sauriens des calcaires lithographiques (Jurassique supérieur) d’Europe occidentale.  Nouv. Arch. Mus. Hist. Nat. Lyon 7 187 pp.
Frickhinger, K A 1994. Die Fossilien von . The Fossils of Solnhofen: Goldschneck-Verlag, 336pp.
Zittell KA 1887. Rhynchocephalia – Handbuch der Palaeontologie 3:583-800. München and Leipzig.

Paleofile

 

Leptosaurus: another transitional taxon between Rhynchocephalia and Rhynchosauria

Leptosaurus, a very small rhynchoceplian basal to Sapheosaurus and Noteosuchus on one branch, Trilophosaurus, Azendohsaurus, Mesosuchus and rhynchosaurs on the other. Teeth are not fused to the jaws. Astragalus not fused to the calcaneum. Note the very tiny pectoral girdle. Preserved in ventrolateral view, the nares are not visible, so perhaps they were dorsal as in rhynchosaurs.

Leptosaurus, a very small rhynchoceplian basal to Sapheosaurus and Noteosuchus on one branch, Trilophosaurus, Mesosuchus and rhynchosaurs on the other. Teeth are not fused to the jaws. Astragalus not fused to the calcaneum. Note the very tiny pectoral girdle. Preserved in ventrolateral view, the nares are not visible, so perhaps they were dorsal as in rhynchosaurs.

Leptosaurus pulchellus (Fitzinger 1837, Zittel 1887, Renesto and Viohl 1997; aka: Kallimodon Cocude & Michel, 1963) SCHA 40 Late Jurassic, Tithonian Stage, Germany,
155.7 to 150.8 Ma.

Holotype: Leptosaurus neptunicus Fitzinger 1837.

Rhynchocephalians are generally not so small, but this one is, likely yet another case of miniaturization at the base or transition to a major clade. In this case the SCHA 40 specimen attributed to Leptosaurus (I haven’t seen the holotype) is basal to the much larger Sapheosaurus and Noteosuchus on one branch, Trilophosaurus, Mesosuchus. Priosphenodon and rhynchosaurs on the other.

The large reptile tree (still not updated) keeps adding transitional taxa without changing the tree topology. That’s a measure of its strength. And more taxa using the same number of characters keeps dropping that character/taxon ratio.

References
Renesto S and Viohl G 1997. A sphenodontid (Reptilia, Diapsida) from the late Kimmeridgian of Schamhaupten (Southern Franconian Alb, Bavaria, Germany). Archaeopteryx 15:27-46.

Megachirellla and Marmoretta are basal to Pleurosaurs

Earlier we looked at pleurosaurs (Fig. 1, elongate, aquatic rhynchocephalians). Pleurosaurus goldfussi (Meyer 1831) was discovered first. Paleopleurosaurus is a more primitive taxon with a distinct premaxillary tooth. Note the retraction of the nares, common to many aquatic reptiles.

The present blogpost updates their origins with phylogenetic analysis, adding these two taxa to the large reptile tree.

Dupret (2004) nested pleurosaurs (Fig. 1) with Sapheosaurus. Adding pleurosaurs to the large reptile tree (not updated yet) nested them with Marmoretta and Megachirella (Figs. 2-5), helping to remove the ‘enigma’ status from the latter. Dupret (2004) did not include these two taxa in analysis.

The pleurosaurs

Figure 1. The pleurosaurs, Pachypleurosaurus and Pleurosaurus, known rhynchocephalians, now nesting with Marmoretta and Megachirella.

Pleurosaurs are yet one more clade of “return to the water” reptiles, and probably the last one anyone thinks of. They’re just not often reported on. Wiki reports, Pleurosaurus fossils were discovered in the Solnhofen limestone formation of BavariaGermany and CanjuersFrance.” The limbs were reduced. The torso and tail were elongated. Pleurosaurs probably swam in an eel-like or snake-like undulating pattern.

But where did they come from?

Figure 2. Marmoretta, a basal rhynchocephalian in the lineage of pleurosaurs

Figure 2. Marmoretta, a basal rhynchocephalian in the lineage of pleurosaurs

Marmoretta oxoniensis (Evans 1991) Middle/Late Jurassic, ~2.5 cm skull length, orginally considered a sister of kuehneosaursdrepanosaurs and lepidosaurs. Here Marmoretta was derived from a sister to GephyrosaurusMarmoretta was a sister to Planocephalosaurus and Megachirella. 

Distinct from Gephyrosaurus, the skull of Marmoretta was flatter overall with a larger orbit. The parietals were longer. The naris was larger and more dorsal. The prefrontal was narrower. The lacrimal was still visible. The jugal was reduced.

A flat-headed rhynchocephalian, Marmoretta nests near the base of that clade, prior to the fusion of teeth together and to the jaws in many derived taxa, including pleurosaurs.

Figure 1. Megachirella, a flat-headed rhynchocephalian close to Marmoretta and basal to pleurosaurs.

Figure 3. Megachirella, a flat-headed rhynchocephalian close to Marmoretta and basal to pleurosaurs.

Megachirella wachtleri (Renesto and Posenato 2003, Renesto and Bernardi 2013) KUH-1501, 2 cm skull length, Middle Triassic, was a tiny lepidosauromorph with a moderately elongated neck and flattened skull. The teeth were short and stout. Megachirella was originally nested with Marmoretta and the large study confirms it, but it is also basal to the aquatic pleurosaurs.

Figure 4. Megachirella in situ with bones colorized. Some bones are represented by impressions of the lost bone.

Figure 4. Megachirella in situ with bones colorized using DGS techniques. Some bones are represented by impressions of the lost bone. The yellow premaxilla tooth is represented by a questionable impression/crack. The nasal may not be a bone, according to S. Renesto. Scale bar = 1 cm.

 

Shifting the pleurosaurs to Gephyrosaurus adds 13 steps. To Planocephalosaurus adds 23 steps. More steps are added with a shift to other rhynchocephalians.

Figure 5. Skull elements of Megachirellla traced in color (Fig. 4) then transferred to line art in three views.

Figure 5. Skull elements of Megachirellla traced in color (Fig. 4) then transferred to line art in three views. Reconstructions are important in such roadkill taxa. 

Megachirella is a Middle Triassic rhynchocephalian. That leaves plenty of time for a sister to evolve into a Late Jurassic pleurosaur. The retracted naris common to pleurosaurs is clear on both Marmoretta and Megachirella. All three had an open lateral temporal fenestra.

If you find any mistakes here, please let me know. Such specimens are at or a little beyond the edge of my experience.

References
Carroll RL 1985. A pleurosaur from the Lower Jurassic and the taxonomic position of the Sphenodontids.
Dupret V 2004. The pleurosaurs: anatomy and phylogeny. Revue de Paléobiologie, Geneve 9:61-80.
Evans SE 1991. A new lizard−like reptile (Diapsida: Lepidosauromorpha) from the Middle Jurassic of Oxfordshire. Zoological Journal of the Linnean Society 103:391-412.
Fraser NC and Sues H-D 1997. In the Shadows of the Dinosaurs: early Mesozoic tetrapods. Cambridge University Press, 445 pp. Online book.
Heckert AB 2004. Late Triassic microvertebrates from the lower Chinle Group (Otischalkian-Adamanian: Carnian), southwestern U.S.A. New Mexico Museum of Natural History and Science Bulletin 27:1-170.
Meyer H 1831. IV Neue Fossile Reptilien, aud der Ordnung der Saurier.
Renesto S and Posenato R 2003. A new lepidosauromorph reptile from the Middle Triassic of the Dolomites (northern Italy). Rivista Italiana di Paleontologia e Stratigrafia 109(3) 463-474.
Renesto S and Bernardi M 2013. Redescriptions and phylogenetic relationships of Megachirella wachtleri Renesto et Posenato, 2003 (Reptilia, Diapsida). Paläontologische Zeitschrift, DOI 10.1007/s12542-013-0194-0

Calanguban, another basalmost scleroglossan squamate

Calanguban alamoi (Simoes, Caldwell and Kellner 2014, Early Cretaceous) was originally considered the oldest scincomorph, but in the large reptile tree (not updated yet) it nests with Liushusaurus (Fig. 1) at the base of the Scleroglossa. Due to the large size of its skull and orbit, this was considered an immature specimen. But all sisters are likewise tiny with a large orbit and short rostrum. So what we appear to see hear is yet another case of miniaturization at the base of a major clade.

Earlier we looked at Euposaurus another basal squamate, but at the base of the Iguania.

Figure 1. Liushusaurus (above) and Calanguban (below) to scale. Both nest at the base of the Scleroglossa, which makes them sisters to the basalmost tested iguanid, Iguana.

Figure 1. Liushusaurus (above) and Calanguban (below) to scale. Both nest at the base of the Scleroglossa, which makes them sisters to the basalmost tested iguanid, Iguana. 

References
Evans SE and Wang Y 2010. A new lizard (Reptilia: Squamata) with exquisite preservation of soft tissue from the Lower Cretaceous of Inner Mongolia, China.
Simoes TR, Caldwell MW and Kellner AWA 2014. A new Early Cretaceous lizard species from Brazil, and the phylogenetic postion of the oldest known South American squamates. Journal of Systematic Palaeontology. http://dx.doi.org/10.1080/14772019.2014.947342

wiki/Liushusaurus