What is Scleromochlus?

Scleromochlus taylori was a little reptilian biped from the Late Triassic of Scotland. The several fossils that are known are preserved as crushed impressions in sandstone. The long legs and slender arms of Scleromochlus immediately set it apart as something very special.

Scleromochlus, a basal crocodylomorph

Figure 1. Scleromochlus, a basal crocodylomorph. That's a sister taxon, Gracilisuchus in the upper right hand corner.

Early Assignments
Woodward (1909) first described Scleromochlus taylori as a dinosaur. Von Huene (1914) reassigned it to the Pseudosuchia. Padian (1984) considered it an Ornithodiran, allied to both pterosaurs and dinosaurs. Sereno (1991) considered it a sister to pterosaurs. Padian (1997) named the clade containing Scleromochlus and pterosaurs the Pterosauromorpha. Benton (1999) used 16 taxa to determine that Scleromochlus was basal to pterosaurs, Lagerpeton, Lagosuchus (Marasuchus) and the Dinosauria. Phytosaurs and Proterochampsa were outgroups. Bipedal crocs were not included.

With Pterosaurs? And Phytosaurs?
The absurdity of these nestings were discussed in an earlier 3-part blog. The linking of Scleromochlus with pterosaurs is also embarrassing. Scleromochlus had tiny fingers, a terminal naris, a deep antorbital fossa, too few cervicals, too deep chevrons and no pedal digit 5, among several other discrediting traits. Cosesaurus is a much better pterosaur sister. It was similar in size to Scleromochlus and had a pteroid, prepubis, extradermal membranes, a long fifth toe, a long fourth finger and other traits shared with pterosaurs. Terrestrisuchus is a much better sister to Scleromochlus (Figure 3).

Properly Nesting Scleromochlus
The present large study demonstrates that pterosaurs and Scleromochlus were not closely related. Even turtles nest closer to pterosaurs than Scleromochlus would. Here Scleromochlus nests within the base of the Crocodylomorpha close to Terrestrisuchus, Saltopus and Gracilisuchus. Surprisingly, no one but Peters (2002) has considered Scleromochlus a crocodylomorph (see Wiki links below) despite the obvious similarities (Figure 3).

Benton’s Biased Reconstruction
Benton (1997) reconstructed Scleromochlus with a posterior-leaning quadrate, as in pterosaurs, but there is no evidence for this. In doing so, Benton reconstructed the skull with a hyper-extended retroarticular process with a quadrate articulation nowhere near the articular bone. The Scleromochlus skull is much wider than tall and the many samples were crushed dorsoventrally, obliterating any data on the orientation of the quadrate. Given an alternate anterior leaning quadrate (Figure 1) the problem with the retroarticular process is removed.

 Scleromochlus according to Benton (1999).

Figure 2. Scleromochlus according to Benton (1999). Red arrows and captions indicate dissimilarities with pterosaurs.

Terrestrisuchus, Gracilisuchus and Saltopus as Sister Taxa
A comparison with Terrestrisuchus, Gracilisuchus and Saltopus is instructive. Each had been considered bipedal. Each had a small upright scapula, a reduced calcaneum and an elongated, appressed metatarsus. Gracilisuchus shared robust cervical ribs, a lumbar region, a short tail and a flat-topped ilium. The palate configuration was virtually identical. Saltopus had tiny fingers, more than two sacral vertebrae, a longer tibia than femur and an elongated hind limb. Benton and Walker (2011) apparently misinterpreted the ephemeral sacrals of Saltopus by deciding that only two were present and elongating each one twice as long as proximal dorsals and caudals, unlike the situation in its other sisters. Terrestrisuchus had a smaller skull and longer neck, but was otherwise virtually identical to Scleromochlus.

Basal Crocodylomorpha

Figure 3. Basal Crocodylomorpha, including Gracilisuchus, Saltopus, Scleromochlus and Terrestrisuchus

Scleromochlus taylori (Woodward 1907) Late Carnian, Late Triassic ~217 mya, 18 cm long, was derived from a sister to DecuriasuchusLewisuchus and Pseudhesperosuchus at the base of a clade that included the crocodylomorphs Gracilisuchus, Saltopus and  Terrestrisuchus. Read more about Scleromochlus here.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Bennett SC 1996. The phylogenetic position of the Pterosauria within the Archosauromorpha. Zoolological Journal of the Linnean Society 118: 261–308.
Benton MJ 1999. Scleromochlus taylori and the origin of the pterosaurs. Philosophical Transactions of the Royal Society London, Series B 354 1423-1446. Online pdf
Benton MJ and Clark JM 1988. Archosaur phylogeny and the relationships of the Crocodilia in MJ Benton (ed.), The Phylogeny and Classification of the Tetrapods 1: 295-338. Oxford, The Systematics Association.
Benton MJ and Walker AD 2011. Saltopus, a dinosauriform from the Upper Triassic of Scotland. Earth and Environmental Science Transactions of the Royal Society of Edinburgh: 101 (Special Issue 3-4):285-299. DOI:10.1017/S1755691011020081
Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.
Hone DWE and Benton MJ 2008. Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.
Huene FR 1910. Ein primitiver Dinosaurier aus der mittleren Trias von Elgin. Geol. Pal. Abh. n. s., 8:315-322.
Juul L 1994. The phylogeny of basal archosaurs. Palaeontographica africana 1994: 1-38.
Padian K. 1984. The Origin of Pterosaurs. Proceedings, Third Symposium on Mesozoic Terrestrial Ecosystems, Tubingen 1984. Online pdf
Parrish JM 1993. Phylogeny of the Crocodylotarsi, with reference to archosaurian and crurotarsan monophyly. Journal of Vertebrate Paleontology 13(3):287-308.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Hist Bio 15: 277–301.
Romer AS 1972. The Chañares (Argentina) Triassic reptile fauna. An early ornithosuchid pseudosuchian, Gracilisuchus stipanicicorum, gen. et sp. nov. Breviora 389:1-24.
Senter P 2003. Taxon Sampling Artifacts and the Phylogenetic Position of Aves. PhD dissertation. Northern Illinois University, 1-279.
Sereno PC 1991. Basal archosaurs: phylogenetic relationships and functional implications. Journal of Vertebrate Paleontology 11 (Supplement) Memoire 2: 1–53.
Woodward AS 1907. On a new dinosaurian reptile (Scleromochlus taylori, gen. et sp. nov.) from the Trias of Lossiemouth, Elgin. Quarterly Journal of the Geological Society 1907 63:140-144.

wiki/Gracilisuchus
wiki/Saltopus
wiki/Scleromochlus
wiki/Terrestrisuchus

What is Smok?

Holy Smok! Look at the Size of That Thing!
A recent paper on a new Late Triassic archosaur, Smok wawelski (Niedwiedzki, Sulej and Dzik 2011) left a few questions unanswered, including, “What is it?” More specifically, the abstract reported, “The skeleton (cranial and postcranial) possesses some features similar to those in theropod dinosaurs and others to those in large crocodile-line archosaurs (rauisuchians), rendering phylogenetic placement of S. wawelski difficult at this time.” With a skull length estimated at ~55 cm, and a total length estimated between five and six meters, Smok was described as the largest carnivorous archosaur in central Europe for its time: larger than any theropod dinosaur or rauisuchian of the Late Triassic/Early Jurassic. The fossils is incomplete, so some aspects can only be imagined. Even so, this specimen can be nested — if it is a given a large enough taxon inclusion set.

The skeleton of Smok

Figure 1. The skeleton of Smok compared to Postosuchus and other smaller archosaurs. Note the great similarity in the shape of the pelvis.

The Nesting Solution
Phylogenetic problems like these are exactly what the large reptile tree was built to do. Dropping Smok’s characters into the established matrix nested Smok with Postosuchus and Batrachotomus at the top of the Rauisuchia. I flipped the jugal around so that the putative “postorbital” process became a preorbital process. It fit better that way.

The skull of Smok reconstructed.

Figure 2. The skull of Smok reconstructed.

Prior Nesting Problems Based on False Paradigms
Unfortunately, recent archosaur family trees recovered by Irmis et al. (2007), Brusatte et al. (2010) and Nesbitt (2011) have ignored several important taxa, have included unrelated taxa, and, as a result, have recovered trees in which many sister taxa do not resemble one another at all. Most of these studies included pterosaurs, which are not related. Likewise the tiny biped, Lagerpeton, nested at the base of the Dinosauria in the Nesbitt study, but in the large study it nested with Tropidosuchus on a distant and separate branch unrelated to dinosaurs. The Nesbitt (2011) tree was poorly resolved with 360 recovered trees (possible solutions). It nested phytosaurs as the immediate outgroups to the Archosauria. In contrast, the large reptile tree found phytosaurs were much more distantly related to archosaurs with a convergent development of the antorbital fenestra and fossa. The Nesbitt tree nested poposaurids with rauisuchians. The large reptile tree nested poposaurids within the Dinosauria while nesting rauisuchians as the outgroup clade to the Archosauria (birds + crocs and their common ancestor). All these problems with the recent Nesbitt (2011) and similar trees just made more problems Niedwiedzki, Sulej and Dzik (2011) trying to nest Smok using those trees. No wonder they threw up their hands in frustration! By contrast, there’s no problem when Smok gets nested in a fully resolved tree in which all sister taxa actually resemble one another. That tree is found here.

The Postosuchus Connection
Like Postosuchus, in Smok the femoral head is inturned, almost like that of primitive dinosaurs.  Niedwiedzki et al. (2011) reported the supratemporal fossa extends onto the frontal, a dinosaur character, but that is an error. That area is the anterior parietal (Figure 2 in red). They reported three or more sacral vertebrae, but basal dinosaurs do not have this character and Postosuchus does. The antitrochanter (a ridge behind the pelvic joint) on the ilium is unlike that of dinosaurs and may be a result, again, of Smok’s size and configuration. They reported characters “unexpected” for rauisuchians, including paroccipital processes that are located dorsal to the occipital condyle (as in Postosuchus), a postfrontal (as in Postosuchus but misidentified by Chatterjee (1985) as the prefrontal (and Chatterjee’s “lacrimal” in dorsal view is the prefrontal), spine tables on the dorsal vertebrae, and a closed acetabulum (“closed” in much the same way as in Postosuchus.

Summary
Smok turns out to be just a big Postosuchus with a relatively smaller skull with a relatively larger naris, similar to its phylogenetic predecessor, Batrachotomus.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Brusatte SL , Benton MJ , Desojo JB and Langer MC 2010. The higher-level phylogeny of Archosauria (Tetrapoda: Diapsida), Journal of Systematic Palaeontology, 8:1, 3-47.
Chatterjee S 1985. Postosuchus, a new Thecodontian reptile from the Triassic of Texas and the origin of Tyrannosaurs. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 309 (1139): 395–460. doi:10.1098/rstb.1985.0092.
Irmis RB, Nesbitt SJ, Padian K, Smith ND, Turner AH, Woody D and Downs A 2007. A Late Triassic dinosauromorph assemblage from New Mexico and the rise of dinosaurs. Science 317 (5836): 358–361. doi:10.1126/science.1143325. PMID 17641198.
Nesbitt SJ 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History 352: 292 pp.
Niedwiedzki G, Sulej T and Dzik J 2011. A large predatory archosaur from the Late Triassic of Poland. Acta Palaeontologica Polonica – in press. doi:10.4202/app.2010.0045. online pdf

wiki/Smok

The Origin of the Pterosaur Sternal Complex

It is a common and mistaken paradigm that pterosaurs appeared out of nowhere, seemingly unrelated to other prehistoric reptiles. Those who say this (and the list is long) also judiciously avoid any discussions of pterosaurs as lizards or fenestrasaurs. Their investments in the outmoded and unsupportable archosaur hypothesis have not provided answers — and never will. Here we will take a look at the development of the sternal complex of pterosaurs evolving from the most parsimonious sister taxa yet discovered (Peters 2000a, 2007).

The Pectoral Girdle in Huehuecuetzpalli
The story begins with Huehuecuetzpalli (Reynoso 1998), a basal tritosaurid lizard with a fairly typical pectoral girdle (Figure 1). A T-shaped interclavicle and sinuous tapered clavicles anteriorly framed the short scapula and fenestrated but otherwise discoidal coracoid. A broad sternum was located at the posterior tip of the interclavicle. The coracoid was free to rotate between the clavicles, interclavicle and sternum, increasing the range of motion of the humerus.

The Pectoral Girdle in Cosesaurus
Several changes to this pattern can be seen in the basal fenestrasaur and tritosaur, Cosesaurus (Figure 1). The interclavicle developed an anterior process. The sternum moved anteriorly, now dorsal to the transverse processes of the interclavicle. The clavicles were shorter, no wider than the sternum and aligned with the anterior rim of the sternum. The coracoids were relatively larger and considerably narrower as the anterior fenestrations expanded until just the quadrant-shaped posterior rim remained. The scapula was strap-shaped with a long posterior process extending over several more dorsal ribs. With the sternum leading edge now anterior to the interclavicle trailing edge, the coracoids had no room to move and their ventral stems became socketed and essentially immobile, resembling the configuration in birds and serving as a precursor to the configuration in pterosaurs.

 

Tritosaur pectoral girdles demonstrating the evolution and migration of the sternal elements to produce a sternal complex.

Figure 3. Tritosaur pectoral girdles demonstrating the evolution and migration of the sternal elements to produce a sternal complex. Figure 1. The evolution of the pterosaur pectoral girdle and sternal complex featuring Huehuecuetzpalli, Cosesaurus, Longisquama, and the basal pterosaur, MPUM 6009.

The Pectoral Girdle in Longisquama
In Longsiquama (Figure 1) the interclavicle, clavicles and sternum are closely integrated, as in pterosaurs. Distinct from all other tetrapods, the clavicles curved posteriorly, extending to the posterior rim of the crescent-shaped sternum, which they frame. The cruciform interclavicle extended ventrally to form a small keel. Taphonomically displaced to beneath the throat, the overlapping clavicles were mistaken by Jones et al. (2000) for a bird-like furcula (fused clavicles in birds).

The Pectoral Girdle in Pterosaurs
In basal pterosaurs (Figure 1) there were few changes from the Longisquama pattern. So the sternal complex (Wild 1994), like many other aspects of pterosaur morphology, had evolved before the advent of large pterosaurian wings (Peters 2002, contra Bennett 2008).

Summary
All these changes could never have taken place if Cosesaurus was restricted to a typical quadrupedal configuration. The forelimbs had to become elevated from the substrate in a bipedal configuration, as imagined (based on morphology) in its phylogenetic predecessors, Lacertulus (Carroll and Thompson 1982) and Huehuecuetzpalli — and as evidence by matching Cosesaurus pedes to Rotodactylus tracks (Peters 2000b) which were ocassionally bipedal. Cosesaurus had a pectoral complex essentially and mechanically identical to that of pterosaurs (and broadly similar to that of birds). So it seems likely that it was also flapping, probably in some sort of territorial or mating ritual, long before gliding and flying were possible in its descendant taxa, Sharovipteryx, Longisquama and pterosaurs.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References:
Bennett SC 2008. Morphological evolution of the forelimb of pterosaurs: myology and function. Pp. 127–141 in E. Buffetaut & D.W.E. Hone (eds.), Flugsaurier: pterosaur papers in honour of Peter Wellnhofer. Zitteliana, B28.
Carroll and Thompson 1982. A bipedal lizardlike reptile fro the Karroo. Journal of Palaeontology 56:1-10.
Elgin RA, Hone DWE and Frey E 2011. The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica doi: 10.4202/app.2009.0145 online pdf
Jones TD et al 2000. Nonavian Feathers in a Late Triassic Archosaur. Science 288 (5474): 2202–2205. doi:10.1126/science.288.5474.2202. PMID 10864867.
Peters D 2000a. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2000b. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277-301.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Reynoso V-H 1998. Huehuecuetzpalli mixtecus gen. et sp. nov: a basal squamate (Reptilia) from the Early Cretaceous of Tepexi de Rodríguez, Central México. Philosophical Transactions of the Royal Society, London B 353:477-500.
Sharov AG 1970. A peculiar reptile from the lower Triassic of Fergana. Paleontologiceskij Zurnal (1): 127–130.
Wild R 1993. A juvenile specimen of Eudimorphodon ranzii Zambelli (Reptilia, Pterosauria) from the upper Triassic (Norian) of Bergamo. Rivisita Museo Civico di Scienze Naturali “E. Caffi” Bergamo 16: 95-120.

The Boomerang-Head Amphibians: Diplocaulus and Diploceraspis

There is nothing really quite like the boomerang-head amphibian, Diplocaulus, except, obviously, the other boomerang-head amphibian, Diploceraspis. The question is:  Where do these two oddballs fit on the early tetrapod family tree?

Diplocaulus and Diploceraspis evolution

Figure 1. Click to enlarge. Diplocaulus and Diploceraspis evolution. The boomerang-head amphibians.

The Nectridea had been the traditional nesting clade, and diplocaulids share many nectridean traits. Their caudal vertebrae include fused hemal arches (or ventral extensions of the centra). The nectridean Urocordylus (Figure 1) had posterior skull extensions, but these were extensions of the squamosal, not the supratemporal and tabular, which remained tiny.

Many members of the Keraterpetontidae (within the Nectridea, yellow bar in Figure 2) had posterior supratemporal/tabular “horns” but this clade fused these two bones and the squamosal remained a large bone reaching the margin of the posterior skull. Moreover, these “horn heads” were all elongated forms  each with a very long tail.

The exception was Eoserpeton tenuicorne (Moodie 1916), which shared the trait of a supratemporal contacting the quadratojugal, blocking the squamosal from any contact with the posterior margin of the skull (Figure 2), as in Diplocaulus. Eoserpeton also had a wide flat body. There is reason to doubt the presence of transverse processes on the caudal vertebrae of Eoserpeton, because neither the predecessor, Tuditanus, nor the successor, Diplocaulus, had them. The tail was likely longer.

Here Diplocaulus nested with Tuditanus. This hornless microsaur appears to represent an ideal ancestor for Diplocaulus before “the madness” set in. These two are among the very few amphibians with a concave ventral margin of the maxilla. According to available evidence, the lateral expansion of the postparietals and tabulars did not even begin until well after the supratemporals had expanded laterally and they continued growing in Diploceraspis long after the supratemporal had achieved its maximum size in Diplocaulus.

In evolutionary terms, some sort of selective pressure developed posteriorly-oriented “horns” on several elongated keraterpetonids, making them look like little horned lizards (like Phrynosoma). In the wider flatter eoserpetonids other selective pressures expanded these horns laterally. In Diplocaulus and Diploceraspis, the “horns” developed laterally to outlandish proportions as these microsaurs grew to become very much larger.

The evolution of Diplocaulus, including Tuditanus and Eoserpeton.

Figure 2. The evolution of Diplocaulus, including Tuditanus and Eoserpeton.

Diplocaulus may be a nectridean, but just barely. It had more in common with the microsaur Tuditanus.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References:
Beerbower JR 1963. Morphology, paleoecology, and phylogeny of the Permo-Pennsylvania amphibian Diploceraspis. Bulletin of The Museum of Comparative Zoology 130: 31-108. online paper
Carroll RL and Baird D 1968. The Carboniferous amphibian Tuditanus (Eosauravus) and the distinction between microsaurs and reptiles. American Museum novitates 2337: 1-50.
Cope ED 1871. Observations on the extinct batrachian fauna of the Carboniferous
of Linton, Ohio. Proceedings of the American Philosophical Society, 12: 177.
Cope Ed 1882 Third contribution to the history of the Vertebrata of the Permian formation of Texas. Proceedings of the American Philosophical Society, Paleontological Bulletin 35:447-461.
Cruickshank ARI and Skews BW. 1980. The functional significance of nectridean tabular horns (Amphibia: Leponspondyli). Proceedings of the Royal Society B (London) 209: 513-527.online abstract
Moodie RL 1909.  A Contribution to the Monograph of the Extinct Amphibia of North America. New Forms from the Carboniferous. Journal of Geology 17:76.
Ruta M, Jeffery JE and Coates MI 2003. A supertree of early tetrapods. Proceedings of teh Royal Society, London B (2003) 270, 2507–2516 DOI 10.1098/rspb.2003.2524 online pdf
Vaughn PP 1962. 1962. The Paleozoic microsaurs as close relatives of reptiles, again. Amer. Midland Nat., vol. 67, pp. 79-84.

wiki/Diplocaulus
wiki/Tuditanus 


Longisquama and the Origin of Pterosaurs

Prequel: Longisquama Gets No Respect
(or the Lengths Scientists Will Go to Protect Pet Theories)

In their two-part paper on pterosaur origins Hone and Benton (2007, 2008) announced they would test whether pterosaurs nested more parsimoniously within the Archosauria (Bennett 1996) or the Prolacertiformes (Peters 2000). They used the technique of the supertree, gathering several trees together to come up with a larger, ostensibly more complete, tree. That permitted them to use the data of others without having to visit fossils. We’ll get back to their results (below), but first a short background study.

Bennett (1996) used suprageneric taxa, for the most part, and nested pterosaurs with Scleromochlus at the base of the Dinosauria + Lagosuchus (now Marasuchus). The Ornithosuchidae were basal to this clade. The Prolacertiformes were nested far toward the base of the tree. Earlier we discussed problems with these putative sisters here. Bennett (1996) did not consider CosesaurusSharovipteryx and Longisquama.

Fenestrasaurus

Figure 1. Click to enlarge. Fenestrasaurs including Cosesaurus, Sharovipteryx, Longisquama and pterosaurs

Peters (2000) tested the matrices of Bennett (1996) and two others (Jalil 1991 and Evans 1986) simply by adding Langobardisaurus and the fenestrasaurs, including CosesaurusSharovipteryx and Longisquama. Pterosaurs nested with these taxa, rather than any archosaur or archosauromorph, when given the opportunity. Peters (2000) erected the clade, the Fenestrasauria, because they shared the trait of an antorbital fenestra without a fossa, convergent with that of archosaurs.

The largest study to date on reptile interrelationships nested Longisquama and pterosaurs with lizards like Lacertulus, Meyasaurus and Huehuecuetzpalli, far from Prolacerta, archosauromorphs, Scleromochlus and archosaurs.

Getting Back to Where We Began
Hone and Benton (2007) discredited the data of Peters (2000) and elected not to include any of it in their supertree. That left only one study that included pterosaurs, Bennett (1996), in their supertree analysis. Having eliminated the opposing candidate data and the opposing candidate taxa, the results were predetermined. The results of Hone and Benton (2008) reflected the results of Bennett (1996). Sadly, the results also nested members of the Choristodera far from the Choristodera and members of the Lepidosauromorpha far from the Lepidosauromorpha, so the study had its problems. Moreover, Hone and Benton (2008) falsely gave credit for the prolacertiform hypothesis to Bennett (1996), after properly giving it to Peters (2000) in their earlier (2007) paper. And now you know  the lengths scientists will go to protect their pet theories.

The Back Half of Longisquama
Ever since Sharov (1971) reported that only the front half of Longisquama was visible, scientists stopped looking for it. Ironically, one of the plumes illustrated by Sharov(1971), the one not radiating like the others, was a tibia and femur. The subdivided “feather shafts” reported by Jones et al. (2000) were actually displaced toes subdivided by phalanges. Here, using the technique of DGS (digital graphic segregation) the back half of Longisquama is, at last, revealed.

The complete fossil of Longisquama.

Figure 2. Click to enlarge. The complete fossil of Longisquama.

The back half of Longisquama was overlooked for so long because the elements lined up with and were camouflaged by the plumes. Apparently Longisquama’s stomach exploded, or was torn up. The front third of Longisquama is undisturbed, the tail is undisturbed, but the hips are turned backwards and the legs and feet are rotated up to the dorsal vertebrae.

Longisquama in lateral view

Figure 3. Longisquama in lateral view, dorsal view and closeup of the skull. Like Microraptor, Longisquama glided/flew with similarly-sized wings both fore and aft.

Distinct from Cosesaurus
The skull of Longsiquama had a more constricted snout, which enhanced binocular vision. The orbits were larger. The teeth had larger cusps. The naris was probably larger. With increased bipedalism and active flapping, Longiquama probably experimented with aerobic metabolism. The cervicals were shorter and the dorsal series was longer, especially so near the hips and between the ilia. The sacrum curved dorsally 90 degrees, which elevated the attenuated tail. These vertebral modifications made Longsiquama similar to a lemur, which also leaps from tree to tree. Such a long torso provided more room for plumes, gave the back great flexibility, and provided more room for egg production. The pectoral girdle was little changed from Cosesaurus. The clavicles curved around the sternal complex and the sternal keel was deeper. Fused together the interclavicle, clavicles and sternum form a sternal complex, as in pterosaurs. During taphonomy the sternal complex ofLongisquama drifted to beneath the cervicals, exactly where the clavicles are found in non-fenestrasaur tetrapods, including birds. This has led to confusion because the clavicles overlapped giving the appearance of a bird-like furcula. As in Cosesaurus, the pterosaur-like pectoral girdle and socketed coracoids enabled Longisquama to flap and generate thrust during leaps. The pelvis was greatly elongated anteriorly and posteriorly with a posterior ilium rising along with the dorsally curved sacrum of seven vertebrae. The pubis and ischium were much deeper, which provided a much larger pelvic aperture to pass a much larger egg. The distal femur was concave and the proximal tibia convex, as in Sharovipteryx. Both the femur and tibia/fibula were more robust. The foot was relatively large with digits of increasing length laterally. Pedal digit V had a curved proximal phalanx.

Longisquama is famous for, and was named for, its dorsal plumes. Another set of plumes arose from its skull and neck. Former caudal hairs (in Cosesaurus) formed a tail vane in Longisquama. As in Sharovipteryx and pterosaurs, Longsiquama had a uropatagium trailing each of its hind limbs. Like Cosesaurus, Sharovipteryx and pterosaurs membranes trailed the forelimbs, too. This documents the origin of the pterosaur wing and proves that it developed distally on a flapping wing (Peters 2002) rather than proximally as a gliding membrane (contra Elgin, Hone and Frey in press) and certainly without wing pronation, loss of digit V, loss of ungual 4 and migration of metacarpals I-III to the anterior face of metacarpal IV (contra Bennett 2008).

Longisquama was overloaded with secondary sexual characteristics. From plumes to flapping arms, Longisquama was all about creating an exciting presentation unrivaled until the present-day bird-of-paradise. Longisquama had everything Cosesaurus had, only wildly exaggerated. With increased bipedalism and active flapping, Longiquama probably experienced the genesis of aerobic metabolism.

Figure 4. Click to enlarge. The origin of the pterosaur wing and the migration of the pteroid and preaxial carpal. A. Sphenodon. B. Huehuecuetzpalli. C. Cosesaurus. D. Sharovipteryx. E. Longisquama. F-H. The Milan specimen MPUM 6009, a basal pterosaur.

The Origin of the Pterosaur Wing
The elongated and robust finger four of Longisquama was also overlooked by all prior workers. Reconstructed here the hand of Longsiquama remains the best transitional example between Cosesaurus and pterosaurs. It is likely that digit 4 did not flex with the other three fingers in Longisquama because the PILs (parallel interphalangeal lines) were not continuous through digit 4, which also supported a pterosaur-like wing membrane, preserved along with the other soft tissue, the plumes.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References:
Bennett SC 2008. Morphological evolution of the forelimb of pterosaurs: myology and function. Pp. 127–141 in E. Buffetaut & D.W.E. Hone (eds.), Flugsaurier: pterosaur papers in honour of Peter Wellnhofer. Zitteliana, B28.
Elgin RA, Hone DWE and Frey E 2011. The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica doi: 10.4202/app.2009.0145 online pdf
Jones TD et al 2000. Nonavian Feathers in a Late Triassic Archosaur. Science 288 (5474): 2202–2205. doi:10.1126/science.288.5474.2202. PMID 10864867.
Martin LD 2004. A basal archosaurian origin for birds. Acta Zoologica Sinica 50(6): 978-990.
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277-301.
Senter P 2003. Taxon Sampling Artifacts and the Phylogenetic Position of Aves. PhD dissertation. Northern Illinois University, DeKalb, IL, 1-279.
Senter P 2004. Phylogeny of Drepanosauridae (Reptilia: Diapsida) Journal of Systematic Palaeontology 2(3): 257-268.
Sharov AG 1970. A peculiar reptile from the lower Triassic of Fergana. Paleontologiceskij Zurnal (1): 127–130.

wiki/Longisquama

Where to Nest Mesosaurus?

Mesosaurus

Figure 1. Mesosaurus up to 1 meter in length, was long considered an anapsid, but the temporal fenestrae were secondarily infilled from a basal diapsid configuration, as in Claudiosaurus.


Mesosaurus is a Problem for Paleontologists
Here’s the paradigm: Despite its many derived traits, Mesosaurus has long been nested with various other basal reptiles. This long-snouted, needle-toothed, aquatic Permian reptile apparently had no temporal fenestrae, according to Modesto (2006, 2010) and others. Therefore Gauthier (1988) and Modesto (1999) nested Mesosauridae with other such taxa, members of the Captorhinidae and Millerttidae, two basal herbivores without an aquatic niche. Laurin and Reisz (1995) nested Mesosauridae between synapsids and turtles. Laurin and Reisz (2004) nested Mesosaurus with Acleistorhinus (Figure 2), another herbivore sister to Milleretta. None of these proposed taxa even vaguely resemble mesosaurs. None of these studies included Claudiosaurusichthyosaurs and thalattosaurs.

acleistorhinus-mesosaurus

Figure 2. Mesosaurus (left) and Acleistorhinus (right) were nested as sister taxa by Laurin and Reisz (2004) despite their many differences. Claudiosaurus and other enaliosaurs were not included in that study.

Not an Anapsid, but a Diapsid
A reconstruction of Mesosaurus (Figure 1) appears to retain at least a sliver of a lateral temporal fenestra. A reconstruction of the more primitive and typically ignored Stereosternum, another mesosaur, appears to retain a complete diapsid configuration. A reconstruction of yet another mesosaur, Wumengosaurus, retains a diapsid configuration, but with the loss of the lower temporal bar by reduction of the quadratojugal.

The Cleithrum
Mesosaurus had a tiny cleithrum, a sliver of bone dorsal to the clavicle on the leading edge of the scapula. It shares this trait with Petrolacosaurus and Claudiosaurus.

The Limbs
The structure of the  ankles made walking on land impossible, thus relatives should be looked for among aquatic taxa, not terrestrial herbivores, like Acleistorhinus

It Takes a Larger Study
A larger study of reptiles, and the largest one so far, nests Stereosternum within the basal aquatic diapsids, between Claudiosaurus, and Wumengosaurus, which was basal to ichthyosaurs and thalattosaurs. Other studies did not offer mesosaurs the opportunity to nest elsewhere. When you expand the inclusion list, as was done here, the opportunity for a correct nesting increases.

The Reptile Tree

Figure 2. The nesting of the mesosaur, Stereosternum, in the Reptile Family tree at the base of the aquatic clade, the Enaliosauria.

Below are skeletal images of the sisters of Mesosaurus in phylogenetic order. The similarities are obvious and follow a gradual evolutionary sequence. The reduction and closure of the temporal fenestrae are also found in sister taxa including Araeoscelis and Pachypleurosaurus (not shown here).

Figure 3. The sisters of Mesosaurus from the basal diapsid, Petrolacosaurus to the basal ichthyosaur, Utatsusaurus.

Figure 3. The sisters of Mesosaurus from the basal diapsid, Petrolacosaurus to the basal ichthyosaur, Utatsusaurus.

Check out the various taxon names in www.reptileevolution.com for more details. As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References:
Gervais P 1865. Du Mesosaurus tenuidens, reptile fossile de l’Afrique australe. Comptes Rendus de l’Académie de Sciences 60:950–955.
Laurin M and Reisz RR 1995. A reevaluation of early amniote phylogeny. Zoological Journal of the Linnean Society 113:165-223.
Modesto SP 1999.Observations on the structure of the Early Permian reptile.
Modesto SP 2006. The cranial skeleton of the Early Permian aquatic reptile Mesosaurus tenuidens: implications for relationships and palaeobiology. Zoological Journal of the Linnean Society 146 (3): 345–368. doi:10.1111/j.1096-3642.2006.00205.x.
Modesto SP 2010. The postcranial skeleton of the aquatic parareptile Mesosaurus tenuidensfrom the Gondwanan Permian. Journal of Vertebrate Paleontology 30 (5): 1378–1395. doi:10.1080/02724634.2010.501443.

wiki/Mesosaurus

The Family Tree of the Pterosauria 14 – Nyctosaurus

Earlier we looked at the base of the Protopteranodontia, a clade that originated with a private specimen incorrectly referred to Germanodactylus cristatus. The clade also included No. 13, Eopteranodon and Eoazhdarcho and the Pteranodontia (Nyctosaurus + Pteranodon).

Here we look at Muzquizopteryx and the variety within the genus Nyctosaurus.

Nyctosaurus clade

Figure 1. The clade of Nyctosaurus and kin. Click to enlarge.

Muzquizopteryx
At the base of the genus Nyctosaurus is the smallest, newest and most primitive member of the nyctosaur clade, Muzquizopteryx (Frey et al. 2006). Overall larger than and distinct from No. 13, the skull of Muzquizopteryx had a longer rostrum, a shorter antorbital fenestra. The crest was shorter. The orbit was smaller, the lateral temporal fenestra was larger. The cervicals were more robust and shorter with higher neural spines. The cristospine was longer, The scapula was no longer than the coracoid. The deltopectoral crest was expanded distally. The pteroid was right angled. Fingers 1-3 were larger.The ischium was narrower. The prepubis fenestra was expanded beyond the anterior rim creating an anterior and ventral process. The femur and tibia were shorter. The foot was larger with longer toes. Pedal digit 5 was a vestige. It is not know whether Muzquizopteryx had jaw rim teeth or not.

Nyctosaurus bonneri, the Fort Hays specimen
Nyctosaurus bonneri FHSM VP 2148 (Bonner 1964, Miller 1972) Coniacian, Late Cretaceous was Overall larger than and distinct from Muzquizopteryx, the skull of Nyctosaurus bonneri was downturned anterior to the antorbital fenestra. No crest was present. The postorbital process of the jugal was gracile. The mandible was nearly as deep as the skull. No jaw rim teeth were present. The cervicals were shorter and more robust. The sacrum was coosified. The sternal complex was shorter and wider. The scapula and coracoid were more robust. The deltopectoral crest was greatly enlarged. The metacarpus was elongated. Fingers 1-3 were vestiges, probably because they could not touch the ground. Compared to Eopteranodon, the wing was longer. The distal wing phalanges were relatively longer. The pelvis was relatively smaller. The hind limb and foot were relatively shorter. The increase in wing length and decrease in leg length means this Nyctosaurus probably spent more time flying. The short crest sometimes applied to this specimen is an artifact made of putty.

YPM 2501
Size-wise and according to Bennett (1991, 2001) YPM 2501 is a Pteranodon distal metacarpus and proximal portion of the manual 4.1 (the wing finger). The strange thing is, this specimen is larger than virtually all — if not all — known specimens of Pteranodon — AND — the extensor tendon process is not fused. This specimen is a problem for Bennett (1991, 2001) and most other current pterosaur workers because an unfused extensor tendon process, to them, means an immature specimen (following archosaur growth pattern traits). However, following lizard growth patterns and phylogenic patterns this is probably a Nyctosaurus, because Pteranodon fuse the ETP. Crestless nyctosaurs don’t. This specimen also had larger fingers than later, more derived taxa.

Nyctosaurus nanus
The smallest Nyctosaurus (about the size of Muzquizopteryx) is N. nanus, known only for a humerus and pectoral girdle.

Nyctosaurus gracilis, the Field museum (Chicago) specimen
Distinct from the N. bonneri, the skull of N. gracilis (Williston 1902a, b) FMNH 25026 had a slightly deeper rostral tip and a straighter dorsal margin without the posterior downturn, as in Muzquizopteryx. The mandible was probably thinner, but it is crushed dorsoventrally. The cervicals were slightly smaller. The sacrals were relatively larger. The gastralia were the fewest and thickest among all pterosaurs, forming ventral support to counteract the large moment arm the developed from the fulcrum at the dorsal/sacral interface. The sternal comnplex had a larger cristospine and sharper corners. The scapula was smaller than the coracoid. The deltopectoral crest of the humerus was strongly pinched. The pteroid was enlarged. Manual 4.1 was relatively longer. Manual 4.4 was shorter. The pelvis was larger and the pubis contacted the ventrally expanded ischium leaving a large circular obturator foramen between them. The hind limb and foot were larger, as in Muzquizopteryx.

Nyctosaurus sp. the Lincoln Nebraska state museum specimen 
Distinct from Nyctosaurus gracilis, the dorsals of the Nebraska specimen (Brown 1978, 1986) UNSM 93000, were relatively shorter. The scapula and coracoid were more robust. The deltopectoral crest of the humerus most closely resembled that of Muzquizopteryx. Fingers 1-3 were tiny vestiges. Manual 4.1 extended to mid ulna when folded. Manual 4.4 was probably fused to m4.3 or it was missing and m4.3 became curved. The pubis and ischium did not touch, as in more primitive nyctosaurs. It would have been impossible for the forelimb to develop thrust during terrestrial locomotion. It was likely elevated or used like a ski-pole.

Nyctosaurus sp. – two private crested specimens
Nyctosaurus sp. private specimens KJ1 and KJ2 (Bennett 2003) were derived from a sister to the Nebraska specimens of Nyctosaurus sp. and represent the last of their lineage with no known descendants. Distinct from the Nebraska specimen, the skull of KJ1 (below) had an enormous bifurcated frontal crest and a longer mandible than rostrum. The upper temporal fenestra was not visible in lateral view. The mandible was extremely sharp and ideal for skim or stab fishing. A notarium (fused dorsal vertebrae) was present. The coracoid was smaller and fused to the scapula. The humerus and deltopectoral crest were robust. The extensor tendon process was fused to the first wing phalanx. The pteroid was longer than in other nyctosaurs. Manual 4.1 was not much longer than the metacarpus. In KJ1 it was no longer than the metacarpus. The pelvis was deeper than shorter. The tibia was shorter. Overall KJ2 was slightly larger than KJ1. Contra Bennett (2003) not all Nyctosaurus had a crest. A crest does not mean these were male specimens.

Other “Big” Nyctosaurus specimens
As shown above (Figure 1), most Nyctosaurus were roughly the same size, but there is evidence of larger specimens. The largest was YPM 2501 (above). Bennett 1992 considered a pelvis, KUVP 993, in the size range of Pteranodon to be a female pelvis, but morphologically it belongs to a very large Nyctosaurus. Bennett (2000) also reported on a very large Nyctosaurus skeleton in an abstract. “…although incomplete, is the largest known specimen of Nyctosaurus with an estimated wingspan of 4.5 m.” Such a Nyctosaurus is shown in gray in figure 1, scaled up from the UNSM specimen.

In Summary
Unlike Pteranodon, the ancestry of Nyctosaurus included a very small taxon, No. 13, mislabeled Pterodactylus by Wellnhofer (1970). After that point all subsequent taxa, no matter how large (including YPM 2501) did not fuse the extensor tendon process or the scapula to the coracoid, until we come to the derived crested and privately held nyctosaurs, KJ1 and KJ2. They alone had a notarium, fused the scapula to the coracoid and fused the extensor tendon process to the first wing phalanx. Thus nyctosaurs, like all other pterosaurs, followed lepidosaur growth patterns as shown by phylogenetic analysis. Some nyctosaurus (and pterosaurs like ornithocheirids) grew to adults without fusion. Others fused certain bones.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References:
Bennett SC 1991. Morphology of the Late Cretaceous Pterosaur Pteranodon and Systematics of the Pterodactyloidea. [Volumes I & II]. Ph.D. thesis, University of Kansas, University Microfilms International/ProQuest.
Bennett SC 1992.
 
Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.
Bennett SC 2000. New information on the skeletons of Nyctosaurus. Journal of Vertebrate Paleontology 20 (Supplement to Number 3):29A.
Bennett SC 2001. The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon. Part I. General description of osteology. Palaeontographica, Abteilung A, 260: 1–112. Part II. Functional morphology. Palaeontographica, Abteilung A, 260: 113–153.
Bennett SC 2003. New crested specimens of the Late Cretaceous pterosaur Nyctosaurus.Paläontologische Zeitschrift 77: 61-75.
Bonner OW 1964. An osteological study of Nyctosaurus and Trinacromerum with a description of a new species of Nyctosaurus. Unpublished Masters Thesis, Fort Hays State University, 63 pages.
Brown GW 1978. Preliminary report on an articulated specimen of Pteranodon Nyctosaurus)gracilis. Proceedings of the Nebraska Academy of Science 88: 39.
Brown GW 1986. Reassessment of Nyctosaurus: new wings for an old pterosaur. Proceedings of the Nebraska Academy of Science 96: 47.
Frey E, Buchy M-C, Stinnesbeck W, González AG, and di Stefano A. 2006. Muzquizopteryx coahuilensis n.g., n. sp., a nyctosaurid pterosaur with soft tissue preservation from the Coniacian (Late Cretaceous) of northeast Mexico (Coahuila). Oryctos 6:19-39.
Miller HW 1972. 
The taxonomy of the Pteranodon species from Kansas. Transactions of the Kansas Academy of Science 74: 1–19.
Williston SW 1902a. On the skeleton of Nyctodactylus, with restoration. American Journal of Anatomy 1: 297–305.
Williston SW 1902b. On the skull of Nyctodactylus, an Upper Cretaceous pterodactyl. Journal of Geology 10: 520–531.

wiki/Nyctosaurus

The Family of the Pterosauria 11 – The Tapejaridae (1 of 2)

In our look at the descendants of Germanodactylus cristatus we earlier looked at the Dsungaripteridae and the Shenzhoupteridae. Today we take on the first half of the spectacular Tapejaridae.

The Tapejaridae
The discovery of the strange skull of Tapejara (Kellner 1989) opened to the door to this large-crested clade, often preserved with soft tissue crests that extended the bone shape. While resembling crested Pteranodon in several aspects, all the similarities were by convergence, although the two clades did share a common ancestor in a sister to Germanodactylus rhamphastinus.

The Tapejaridae

Figure 1. The Tapejaridae, including Sinopterus, Huaxiapterus, Tapejara, Tupandactylus, Tupuxuara and Thalassodromeus

Sinopterus
Sinopterus dongi IVPP V13363 (Wang and Zhou 2003) wingspan 1.2 m, 17 cm skull length, was linked to Tapejara upon its discovery. Derived from a sister to Germanodactylus cristatus and Nemicolopterus, the skull of Sinopterus had a convex dorsal profile created by an expanded antorbital fenestra. The lacrimal and nasal were greatly expanded. The jugal was deeper, but the orbit remained large. The mandible was deeper. The palate was relatively twice as wide. The sacrals were nearly one half of the torso, but the torso remained rather elongated. The sternal complex was pentagonal. The radius and ulna were elongated. Manual 3.1 was longer than m2.1. Manual 4.1 was longer than the metacarpus. Manual 4.2 extended past the elbow. Metatarsal 3 was the longest. The proximal pedal phalanges were elongated such that p1.1 was subequal to p2.1 and p3.1.

Huaxiapterus
Huaxiapterus jii GMN-03-11-001 (Lü and Yuan 2005) Aptian, Early Cretaceous, wingspan 9.4 m, 18.5 cm skull length, was considered a distinct taxon when first described, then relegated to a species of Sinopterus. Here Huaxiapterus is indeed a distinct taxon. The skull was shorter with a pronounced “bump” on the rostrum. The antorbital fenestra was taller. The jugal leaned posteriorly. The cranial crest was shorter. The upper temporal fenestra was smaller. The mandible was deeper and shorter. The cervicals were longer and more gracile. The dorsals were longer relative to the sacrals. The short ribs indicate the torso was not deep. The caudals were vestigial. The humerus and metacarpus were longer. Fingers 1-3 were more robust. Manual 3.1 was only slightly longer than m2.1. The pelvis was smaller. The prepubis was shorter. The pubis produces a posterior process. The fibula was a vestige. Metatarsal IV was the longest. Digits II-IV were aligned distally. The proximal phalanges were shorter.

The family tree of Germanodactylus.

Figure 2. Click to enlarge. The family tree of Germanodactylus.

Tapejara
Tapejara wellnhoferi (Kellner 1989) ~108 mya, Early Cretaceous was immediately recognized as something quite different when first discovered. Distinct from Huaxiapterus, the skull of Tapejara was shorter with a taller rostral crest. The mandible was deeper. The jugal did not lean as much. The cervicals were shorter. The sacrals were longer (judging by the pelvis). The humerus was more narrowly waisted. The rest of the wing was more gracile, including the fingers. The posterior process of the pubis was further expanded creating an obturator foramen between it and the broad ischium. The prepubis was angled anteriorly. The hind limbs were shorter. The fibula was barely present.

Tupandactylus
Tupandactylus imperator (Campos and Kellner 1997) ~110 mya, Late Aptian, Early Cretaceous is one of the most spectabular pterosaurs ever discovered. Distinct from Tapejara, the skull of Tupandactylus was longer with an even taller rostral crest and a longer cranial crest. Between them a soft tissue crest spanned these masts. The nasal, maxilla and even a process of the jugal expanded dorsally to laminate with and support the premaxillary crest. The premaxilla topped the frontal and parietal extending far posterior to the back of the skull to create an elongate bony crest that served as the base for a very large soft-tissue crest much larger in lateral area than the entire skull.

Next time we’ll finish up the Tapejaridae with its largest and most derived members, Tupuxuara and Thalassodromeus.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References:
Kellner AWA 1989. A new edentate pterosaur of the Lower Cretaceous from the Araripe Basin, northeast Brazil. Anais da Academia Brasileira de Ciências 61, 439-446.
Wang X and Zhou Z 2003. A new pterosaur (Pterodactyloidea, Tapejaridae) from the Early Cretaceous Jiufotang Formation of western Liaoning, China and its implications for biostratigraphy. Chinese Science Bulletin 48:16-23.
Li J, Lü J and Zhang B 2003. A new Lower Cretaceous sinopterid pterosaur from the Western Liaoning, China. Acta Palaeontologica Sinica 42(3):442-447.
Lu J, Jin X, Unwin DM, Zhao L, Azuma Y and Ji Q 2006. A new species of Huaxiapterus (Pterosauria: Pterodactyloidea) from the Lower Cretaceous of Western Liaoning, Cina with comments on the systematics of Tapejarid pterosaurs: Acta Geologica Sinica, v. 80, n. 3, p. 315-326.7. (H. corrollatus)
Lü J, Gao Y, Xing L, Li Z and Ji Q 2007. A new species of Huaxiapterus (Pterosauria: Tapejaridae) from the Early Cretaceous of Western Liaoning, China: Acta Geologica Sinica, vol.81, no.5, p.683-687. (H. benxiensis)
Lü J and Yuan C 2005. New Tapejarid Pterosaur from Western Liaoning, China. Acta Geologica Sinica 79 (4): 453-45 (H. jii)

wiki/Sinopterus
wiki/Huaxiapterus
wiki/Tapejara
wiki/Tupandactylus

The Family Tree of the Pterosauria 9 – The Dsungaripteridae

Earlier we looked at the rise of Germanodactylus and the clade of Germanodactylus. Today we take a look at the clade of Germanodactylus cristatus (the holotype) including the Dsungaripteridae. The Shenzhoupteridae and the Tapejaridae will follow.

The Dsungaripteridae

Germanodactylus and the Dsungaripteridae

Figure 1. Germanodactylus and the Dsungaripteridae

The relationship between Germanodactylus cristatus and Dsungaripterus was recognized immediately (Young 1964). Traditionally considered toothless and overlooked by all prior workers, the tips of both jaws are actually sharp teeth, a trait inherited from Germanodactylus. The posterior premaxillary teeth are absent. Unfortunately, there aren’t many dsungaripterids known. Several are from partial skulls.

Lonchognathosaurus  (Maisch, Matzke and Sun 2004) is the smallest of the dsungaripterids, known from only a portion of the rostrum.

“Phobetor”
Phobetor” (Yang 1973) was combined with Noripterus by Lü et al. (2009) and is known from a complete skull. Distinct from Germanodactylus cristatus (No. 61), the skull had a smaller and subdivided orbit and a raised cranial crest. The lacrimal produced a posterior process to meet the postorbital, which produced an anterior process to divide the orbit into upper and lower areas. The jawline was straighter. The quadrate angle was raised. The quadratojugal was larger. Teeth erupted only in the middle of the jaws. The mandible was straigther and more gracile.

Noripterus
Noripterus (Yang 1973) is known from postcranial material only. The humerus had a smaller deltopectoral crest that was not medially angled. The metacarpus was longer than the ulna. Fingers I-III were reduced and so were the unguals. Manual 4.2 extended beyond the elbow when the wing was folded. The hind limb was longer and more gracile. The foot was smaller with unguals aligned transversely. The metatarsus was relatively longer and the toes were shorter.

Dsungaripterus
Dsungaripterus (Young 1964) ~4 m wingspan, Early Cretaceous was derived from a sister to Noripterus. Together these dsungaripterids represent the last of their lineage. Distinct from Noripterus, the skull of Dsungaripterus was more robust with upturned jaw tips. Bone grew over the rear teeth during maturation. The suborbital region was further ossified. The mandible was more robust. The sternal complex was rectangular. Posteriorly two sternal ribs (or gastralia) were massive. The gastralia were few and robust. The wing was more gracile. The femur was more robust. The fibula was fused to the tibia.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References:
Bakhurina NN 1982. A pterodactyl from the lower Cretaceous of Mongolia. Paleontological Journal 1982(4): 104-109.
Lü J, Azuma Y, Dong Z, Barsbold R, Kobayashi Y and Lee Y-N 2009. New material of dsungaripterid pterosaurs (Pterosauria: Pterodactyloidea) from western Mongolia and its palaeoecological implications. Geological Magazine, 146(5): 690-700.
Maisch MW, Matzke AT and Sun G 2004. A new dsungaripteroid pterosaur from the Lower Cretaceous of the southern Junggar Basin, north-west China. Cretaceous Research 25: 625–634. doi:10.1016/j.cretres.2004.06.002.
Yang Z 1973. Reports of Paleontological Expedition to Sinkiang (II): Pterosaurian Fauna from Wuerho, Sinkiang (in Chinese). Memoirs of the Institute of Vertebrate Paleontology and Paleoanthropology Academia Sinica 11: 18–35.
Young CC 1964. On a new pterosaurian from Sinkiang, China. Vertebrata PalAsiatica 8: 221-256.

wiki/Dsungaripterus
wiki/Noripterus

The Family Tree of the Pterosauria 8 – The Germanodactylus Clade

We just looked at the ramp up to Germanodactylus rhamphastinus. For a very long time we knew of only two Germanodactylus specimens, G. cristatus (the holotype) and G. rhamphastinus. Now we know of many more (Figure 1) not counting the many descendants. Some taxa within this clade have been assigned to other genera (Eosipterus, Elanodactylus). Others are known only by museum numbers (SMNK PAL 3830, MOZ 36325P). Still others are private specimens loaned to museums (SMNK PAL 6592, the BMM specimen). All this will require nomenclature revision at some time in the future.

Germanodactylus rhamphastinus
Germanodactylus rhamphastinus (Wagner 1851 B St AS I 745, No. 64 of Wellnhofer 1970) was the first of the raven-sized germanodactylids (Figure 1). No. 64 was derived from No. 23 and phylogenetically preceded Eosipterus and JME Moe 12. Distinct from No. 23, the skull of No. 64 was deeper anteriorly and crested posteriorly. The orbit was smaller with a V-shaped ventral margin. The teeth were larger and narrower. The jugal was narrower and deeper. The cervicals were longer and decreased in size cranially. The torso was reduced. The caudals were longer as a set, but most individual caudals remained short. The deltopectoral crest did not lean medially. The humerus was straight. The metacarpus was relatively longer. Fingers I-III were more robust and the unguals were larger. Manual 4.2 extended just to the elbow. The ischium was bifurcated. The prepubis was L-shaped. Pedal digit I was shorter. The unguals were smaller.

Following G. rhamphastinus the germanodactylids spread worldwide. Here they are presented in roughly phylogenetic order.

Germanodactylus and kin

Figure 1. Click to enlarge. Germanodactylus and kin.

Eosipterus
Eosipterus yangi (Ji and Ji 1997) GMV 2117 (not shown in Figure 1) was a headless specimen originally allied with Pterodactylus and Ctenochasma. Distinct from G. rhamphastinus, the humerus of Eosipeterus was shorter and slightly expanded distally. The deltopectoral crest was much larger. The metacarpus was shorter. Fingers 1-3 were smaller. Manual 4.2 extended beyond the elbow when the wing was folded. The ischium was expanded. Pedal unguals 2-4 were aligned transversely. The pedal digits were smaller.

Germanodactylus sp. JME/BSP specimen
The JME specimen of Germanodactylus (Rodriques, Kellner and Rauhut 2010) JME Moe12 (plate) BSP 1977 XIX 1 (counterplate). Distinct from G. rhamphastinus, the skull of JME Moe12 was much sharper with a relatively larger antorbital fenestra and orbit. No ossified crest jutted out from the cranium. The maxilla was slightly concave ventrally. The dentary was slightly convex dorsally to match it. The cervicals were more gracile. The torso was relatively longer. The caudals were reduced. The sternal complex, scapula and coracoid were all reduced. The forelimb was more gracile with smaller fingers. The metacarpus was shorter. Manual 4.1 was shorter than m4.2. The pubis and ischium were not sutured ventrally. The prepubis was shorter. The posterior process of the ilium was no longer than the posteriorly expanded ischium. The hindlimb was longer. The metatarsals and unguals were aligned transversely.

The family tree of Germanodactylus.

Figure 2. Click to enlarge. The family tree of Germanodactylus.

The BMM Germanodactylus
This privately held Late Jurassic pterosaur was on display at the Bürgermeister-Müller-Museum. In his blog Dr. David Hone mislabeled it a Pterodactylus and likewise an image of this specimen appears on the Wikipedia Pterodactylus page. Cladistic analysis (Figure 2) nests the BMM specimen in the middle of other Germanodactylus specimens. Overall it was nearly identical to MOZ 3625P (see below), but more robust. The foot of the BMM specimen is similar to that of  PAL 3830 with a large pedal 1.2 (the ungual) larger than p1.1. This pterosaur and MOZ 3625P (below) nest at the base of a split in the tree between the holotype Germanodactylus cristatus (and its crested tapejarid descendants) and the referred specimen SMNK 6592  (and its crested pteranodontid descendants).

MOZ 3625P
MOZ 3625P was originally considered an indeterminate pterodactyloid. Here it nests within the genus Germanodactylus. The MOZ 3625P skull is not known. Distinct from JME Moe12, the cervicals of MOZ 3625P were longer and more gracile. The humerus was more robust. The pubis and ischium were completely fused.

Germanodactylus cristatus
With the holotype for the genus, Germanodactylus cristatus B St 1892 IV 1 (Pterodactylus kochi Plieninger 1901, Germanodactylus cristatus Wiman 1925, No. 61 of Wellnhofer 1970) we move into another clade that continued the extremely sharp jawed morphology. The shoulder joint was shifted to the ventral torso, the so-callled “bottom-decker” wing placement. This clade included “Phobetor” in the Dsungaripteridae, Nemicolopterus in the Shenzhoupteridae and Tapejara in the Tapejaridae, to name just a few. No. 61 was also a sister to the long-legged super-clawed pterosaur, SMNK PAL 3830. Distinct from JME Moe 12, the skull of No. 61 was smaller overall and had an ossified rostral crest supporting a larger soft tissue crest. It had a cranial crest oriented posteriorly and posterior processes of the squamosal that formed “ears”. The premaxilla extended along the entire dorsal margin of the skull, including the cranial crest. The vomers were visible in lateral view. The premaxillary teeth were vestigial. The cervicals were longer. The caudals were more robust. The humerus was more robust with a longer deltopectoral crest. The metacarpus was longer. Fingers 1-3 were larger.

SMNK PAL 3830 – The Crato “Azhdarchid”
SMNK PAL 3830 (the Crato “azhdarchid” Frey & Tischlinger 2000) was originally considered an azhdarchid, like Quetzalcoatlus, probably due to its great size. Here it nests as a sister to Germanodactylus cristatus. Distinct from and twice the size of No. 61, fingers 1-3 of PAL 3830 were relatively larger. Manual digit 3 was longer than half the metacarpus and as long as the entire foot. The metacarpus was much more robust than manual 4.1. The foot, while appearing quite lethal, was actually much smaller relatively, reduced to about a third of the tibia. A small patella was present. The penultimate pedal phalanges were the longest in each series suggesting an arboreal habitat when not flying. It’s hard to imagine such claws ever touching the ground.

Elanodactylus
At the base of the other branch of germanodactylids is another oversized germanodactylid, Elanodactylus. Elanodactylus is known chiefly from wing material. Atypical for pterosaurs, manual 4.2 was longer than m4.1. The metacarpals were shorter than in other germanodactylids.  The neck vertebrae were considered similar to those of azhdarchids, but then germanodactylid neck vertebrae have not been well described because often they were often preserved exposed ventrally. Andres and Ji (2008) nested Elanodactylus with ctenochasmatids, but shifting it there adds 9 to 12 steps to the tree.

Germanodactylus sp. SMNK 6592
A private Germanodactylus, SMNK 6592, is basal to Eopteranodon, Pteranodon and Nyctosaurus (including Muzquizopteryx). Overall larger and distinct from the BMM specimen (above), the anterior tooth was larger and elevated to the directly anterior orientation creating a sharper snout that was longer than the mandible, as in Pteranodon. The rostral margin was straight and terminated in a small posteriorly-oriented parietal crest. The antorbital fenestra was larger. The rostrum was deeper. The sternal complex was larger with sharper corners. The deltopectoral crest was displaced distally, away from the proximal articular surface. The distal humerus was expanded. The hindlimbs were longer and more gracile.

Descendant taxa will be covered in future blogs.

A Summary
The genus Germanodactylus began with tiny pterosaurs provided with longer and sharper jaws. At three phylogenetic nodes the jaws became extremely sharp following rotation of the anterior tooth to an anterior orientation on both the upper and lower jaws. The size of this genus varied minimally, but Elanodactylus and the SMNK PAL 3830 specimen were larger than normal exceptions (not counting the very large descendants). Several Germanodactylus specimens had short hard crests that probably supported extensions of soft tissue. The manual fingers and claws of some germanodactylids were quite large and trenchant.

 

References:
Andres B and Ji Q 2008. A new pterosaur from the Liaoning Province of China, the phylogeny of the Pterodactyloidea, and convergence in their cervical vertebrae. Palaeontology51: 453–469.
Ji S-A and Ji Q 1997.
Discovery of a new pterosaur in Western Liaoning, China. Acta Geologica Sinica 71(1): 1-6 [in Chinese].
Rodrigues T, Kellner AWA and Rauhut OWM 2010. A New Specimen of the Archaeopterodactyloid Germanodactylus R[h]amphastinus. Acta Geoscientica Sinica 31(Supp. 1): 57-58.
Zhou C 2009. New material of Elanodactylus prolatus Andres & Ji, 2008 (Pterosauria: Pterodactyloidea) from the Early Cretaceous Yixian Formation of western Liaoning, China.Neues Jahr. Geo. Paläo. Abh. (DOI: 10.1127/0077-7749/2009/0022.)