What Is Prejanopterus?

The Pterosaur That Leaned a Little to the Left
Unlike any other known pterosaur, the toothy rostrum of Prejanopterus curvirostra (Fuentes Vidarte and Calvo 2010 ) curved to the left (in dorsal view). Here it is seen in ventral view curving to the right. This is not an artifact of compression over millions of years because several specimens share this odd trait.

Prejanopterus was the first genus of pterosaur from the Lower Cretaceous of Spain. The specimen is known from more than a dozen broken and scattered elements. The question left by the authors: what sort of “pterodactyloid” is it? They were not able to say. Fortunately the specimen and the paper provide just enough data to reveal a nesting.

Prejanopterus parts to scale.

Figure 1. Prejanopterus parts to scale.

Prejanopterus and Elanodactylus Nest as Sisters
The key to this nesting was the unusual shape of the pelvis. The posterior process of the ilium had an anterior process. The pubis was separate from and longer than the ischium. The acetabulum was relatively large.  Only the Elanodactylus described by Zhou (2009) preserves a similar pelvis. No skull is known for Elanodactylus… perhaps until now.

Fuentes Vidarte and Calvo (2010) followed Andres and Ji (2008) in considering  Elanodactylus a sister to Ctenochasma, but Elanodactylus nests here with Germanodactylus. The pointed, tooth-tipped jaws of Prejanopterus and the fused extensor tendon process* confirm a nesting with Germanodactylus.

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.

* Remember, this is a phylogenetic trait, not a sign of maturation. As lizards, pterosaurs grew by different rules than archosaurs.

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.
Fuentes Vidarte C and Calvo M 2010.
Un nuevo pterosaurio (Pterodactyloidea) en el Cretácico Inferior de La Rioja (España). Boletín Geológico y Minero, 121 (3): 311-328.  ISSN: 0366-0176
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.)

The Flat-Head Pterosaur

Part of a Private Collection Made Public
There is a tiny little anurognathid pterosaur in a private collection that Dr. S. Chris Bennett (2007) described as a small Anurognathus ammoni (Döderlain 1923). Here that specimen was found to nest next to Anurognathus, but it was neither conspecific nor congeneric with Anurognathus. It was distinct in morphology from flat head to tiny toe. It actually shares more characters with it phylogenetic predecessor,  Dendrorhynchoides (Ji and Ji 1998 ), including a very wide sternal complex and torso. While most pterosaurs had long pointed jaws and most anurognathid pterosaurs had a round, bubble-like skull, this particular anurognathid had the flattest, widest, most pancake-like skull of all. The eyeballs would have popped up above the skull outline, like a frog’s eyeballs. Figure 1 portrays both anurognathids to scale. The many differences are easy to see. Let’s run through them.

Figure 1. The flat-head pterosaur, a private specimen (on the left) attributed by Bennett (2007) to Anurognathus ammoni (on the right).

Figure 1. The flat-head pterosaur, a private specimen (on the left) attributed by Bennett (2007) to Anurognathus ammoni (on the right).

The Skull
The skull was described by Bennett (2007) as having an enormous orbit in the anterior half of the skull, little to no antorbital fenestra, and a broad set of parietals with widely spaced upper temporal fenestra among several other autapomorphies. (You can view those illusory interpretations here). No sister taxa have these traits. Nevertheless, this false and frankly, goofy to monstrous reconstruction has become widely accepted. Such a reconstruction replaces the large air-filled antorbital fenestra of all other pterosaurs with gel-filled eyeballs. Such a reconstruction moves the eyeballs into the anterior half of the skull, the opposite of all other pterosaurs. Bennett (2007) mistook the curved and dentally subdivided maxilla for a giant sclerotic ring preserved on edge, which no other crushed specimen of any tetrapod ever does. Bennett (2007) was unable to segregate the layers of bones so reconstructed a wide, flat parietal, the opposite of all other pterosaurs. Here DGS (digital graphic segregation) was able to delineate all the skull bones recovering identical left and right elements that resemble those of sister taxa and produce a reconstruction in line with sisters, rather than completely different as in the Bennett (2007) reconstruction (see both here).

At left the traditional Bennett (2007) interpretation. On the right, interpretation based on finding and tracing paired bones.

Figure 2. At left the traditional Bennett (2007) interpretation. On the right, interpretation based on finding and tracing paired bones.

The Post-Crania
The rest of the skeleton was much more typical of anurognathid pterosaurs. The cervical series was relatively longer than in Anurognathus. The torso was not as wide as in Dendrorhynchoides and the dorsal ribs were more gracile. The caudals were greatly reduced. The sternal complex was not quite as wide. The pteroid was smaller. Bennett (2007) determined that manual phalanx 4.4 was missing, but it is largely buried. The distal portion reappears at the pelvis and all sister taxa have four long wing phalanges. Pedal digit 2 is not the longest. The proximal pedal phalanges had more typical proportions than the short ones in Dendrorhynchoides.

The Flathead Anurognathid

Figure 3. The SMNS anurognathus as reconstructed in various views. Black circle is hypothetical egg.

Why The Wide Face?
Obviously the wide flat skull gave the private specimen some sort of competitive advantage. Certainly the wider gape captured more tiny insects. The disc-like shape, like a flying saucer, may have been raised and lowered in the airstream to affect the flightpath and such a shape reduced aerodynamic drag while streamlined in the neutral position.

Think About the Size of the Egg!
With such a tiny pelvic opening, the egg of the private specimen would have been very tiny, on the order of 3-4 mm in diameter. The hatchling would have stood one-eighth as tall as the 6 cm adult or less than 8 mm in height (possibly taller if the egg was elongated).  Such a fly-sized pterosaur risked desiccation if it flew in dry air, so it may have scurried about in damp leaf litter snatching insects on the ground as a juvenile.

Click here for more information and images.

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 2007. A second specimen of the pterosaur Anurognathus ammoni. Paläontologische Zeitschrift 81(4):376-398.
Bennett SC 2008. Morphological evolution of the wing of pterosaurs: myology and function. Zitteliana B28: 127-141.
Döderlain L 1923Anurognathus ammoni, ein neuer Flugsaurier. Sitzungsberichte der Königlich Bayerischen Akademie der Wissenschaten, zu München, Mathematischen-physikalischen Klasse: 117-164.
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
Ji S-A and Ji Q 1998. A New Fossil Pterosaur (Rhamphorhynchoidea) from Liaoning. Jiangsu Geology 4: 199-206.
Peters D 2001. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15:277–301.
wiki/Anurognathus

Aurorazhdarcho – Unfortunately, Not Related to Azhdarcho.

A recent paper by Frey, Meyer and Tischlinger (2011) reported on a pterosaur that has been known for several years, but only now published and given a name, Aurorazhdarcho. The authors erected a new family, the Protazhdarchidae and attributed the specimen to the Azhdarchoidea. Here, along with Wellnhofer’s no. 13,  Eopteranodon and Eoazhdarcho, Auroazhdarcho nests at the base of Pteranodon + Nyctosaurus, far from any azhdarchids despite overall appearances. The details tell another story.

Convergence Again
Below we can see members of the Azhdarchidae (Fig. 1) and the Eopteranodon clade (Fig. 2) that includes Aurorazhdarcho. Keys to making this nesting were the distinct proportions of the manual and pedal elements. The prepubes were virtually fused at the midline in Auroazhdarcho, as in sister taxa.

The Azhdarchidae.

Figure 1. The Azhdarchidae. Click to enlarge. Note the resemblances to Auroazhdarcho, all by convergence.

Golden Flakes in UV
Apparently without a skull and cervicals, Aurorazhdarcho preserves a faint skull-like patch of golden flakes seen in ultraviolet light. In Figure 2, the abstract tracing above the reconstruction of Aurorazhdarcho was taken from this amorphous area. The gray skull and cervicals in Figure 2 are a best guess reconstruction. Apparent rows of no. 13-like teeth are barely visible, but let’s not put too much stock in those. I don’t know what to make of all the curved lines, including a highly curved mandible. Did the fossil soften up before burial? The rest of it did not. Did they get washed away before burial, leaving only drifting impressions? Good question. No answer. The rest of the fossil was swirled a bit.

Figure 2. Left to right, Eopteranodon, Wellnhofer's No. 13 and Aurorazhdarcho, sisters that nest far from the Azhdarchidae.

Figure 2. Left to right, Eopteranodon, Wellnhofer’s No. 13 and Aurorazhdarcho, sisters that nest far from the Azhdarchidae.

Missing Pedal Phalanges?
The authors did not make mention of the missing disc-like pedal phalanges (p3.2, p4.2, p4.3) typically found in pterosaurs of this grade, nor did they illustrate them. If the disc-like phalanges were fused to the larger phalanges, or had just disappeared (as in higher cynodonts), that would be news that was apparently overlooked.

The Skinniest Pterosaur?
Aurorazhdarcho may have had the skinniest legs of all pterosaurs (but see Rhaeticodactylus for more gracile wings).  Compared to its sisters (Fig. 2) Aurorazhdarcho was more gracile in the wings as well.

The Sternal Complex
The sternal complex is quite large and broad in Aurorazhdarcho and its sisters. Not so in Quetzalcoatlus and its azhdarchid sisters back to the Jurassic taxa where the non-azhdarchid sisters to the azhdarchidsHuanhepterus, no. 44, no. 42 and no. 57 have a large sternal complex.

Male or Female? Juvenile or Mature?
Frey, Meyer and Tischlinger (2011) reported, “The partial fusion of the glenoideal suture of the scapulocoracoid and the near complete co-ossification of the olecranon process with the basal wing finger phalanx suggests a late juvenile or subadult individual (cf. Bennett 1993; Frey and Martill 1998).”

Figure 3. The faintest impressions of a skull were found by the original authors and colorized here.

Figure 3. The faintest impressions of a skull were found by the original authors and colorized here. I think the tan element is a palatal element. Hard to say.

Unfortunately, these are phylogenetic characters, as we learned earlier. As lizards, pterosaurs don’t follow archosaur bone growth patterns (Maisano 2004).

Frey, Meyer and Tischlinger (2011) also reported, “We suggest here that a ventrally open pelvis lacking a puboischiadic symphysis would be indicative for a female because of the wide pelvic apperture would serve as an egg passage (Unwin 2006). Those pterosauria with a tightly fused puboischiadic symphysis and a narrow pelvic aperture like NMB Sh 110 are likely to have been males.”

Unfortunately the ventrally open/closed pelvis is also a phylogenetic character. The symphysis is a trait shared with sisters. Fusion of the pubis and ischium occurs in Eopteranodon (Fig. 2).

Summary
Aurorazhdarcho was a Jurassic sister to Wellnhofer’s (1970) no. 13 and the Early Cretaceous sisters Eoazhdarcho and Eopteranodon. Jurassic sisters to the Azhdarchidae include Wellnhofer’s no. 42 and no. 44, just as skinny and crane-like.

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
Frey E, Meyer CA and Tischlinger H 2011. The oldest azhdarchoid pterosaur from the Late Jurassic Solnhofen Limestone (Early Tithonian) of Southern Germany. Swiss Journal of Geosciences, (advance online publication) doi:10.1007/s00015-011-0073-1

Maisano JA 2002. Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrate Paleontology 22:268-275.


Ctenochasma porocristatum Needs a Nose Job

Another Heretical Paradigm Buster
Ctenochasma porocristata [ammended to porocristatumSos 2179 (Buisonjé 1981, Fig. 1), Late Jurassic, ~150mya, ~26 cm skull length, was originally considered a species of Ctenochasma due to its many teeth and long flattened skull. However, those teeth were not elongated and laterally oriented, as in Ctenochasma. Unfortunately, there is no evidence in Figure 1 (click to enlarge it) for the elongated teeth that Buisonjé imagined (Fig 3, second from bottom). Contra Bennett (2007), the teeth weren’t all broken off, although a few were. This was no typical ctenochasmatid. The teeth were short, sharp and interlocking creating a seive.

The bump on top of the skull was considered a crest of sorts with “vertical striae in the flanks of the crest, placed at regular intervals of .12mm,” but other ctenochasmatids have a narrow comb-like crest (when present), not a thick bump.

Ctenochasma? porocristatum.

Figure 1. Ctenochasma? porocristatum. Click to enlarge.

The True Identity of “The Bump”
On closer examination, the “bump” turned out to be the missing anterior rostrum, broken off and displaced during taphonomy. Short sharp teeth (misinterpreted “regular striae”?) surround it. Graphically moved to the anterior it becomes a good fit (Fig. 2). Even if the anterior rostrum did not migrate during taphonomy to the mid rostrum, extending the lines of the larger piece anteriorly produces much the same reconstruction, distinct from all other known taxa.

Reconstructing Sos 2179.

Figure 2. Reconstructing Sos 2179.

If Not Ctenochasma, What is Sos 2179?
Phylogenetic analysis nested Sos 2179 with another long jawed oddball also mislabeled “Pterodactylus,” Sos 2428, the flightless pterosaur. Like Sos 2179, Sos 2428 had a very long, flat skull filled with fewer teeth. Sos 2428 was smaller overall with relatively smaller jaws filled with fewer teeth. So it was more primitive. Sos 2179 was larger, toothier and probably just as flightless. Sure would be nice to find the rest of it now. Other members of the clade that includes Sos 2179 and Sos 2428 feature several Pterodactylus lookalikes including n42, n44 and Huanhepterus. As a clade these were all  sisters to the azhdarchid branch.

A selection of valid Ctenochasma skulls

Figure 3. A selection of valid Ctenochasma skulls together with the two interpretations of Sos 2179 (in gray below).

Sos 2179 in Vivo
Given the extremely long flat snout filled with hundreds of short sharp interlocking teeth in Sos 2179, together with comparisons to its flightless, big-bellied sister Sos 2428, we can imagine Sos 2179 was an even larger flightless pterosaur. The big belly in Sos 2428 suggests herbivory, so, if similar, Sos 2179 probably sieved floating algae. A hasty getaway would have involved running with its impressive thighs and flapping its presumably small wings for added thrust.

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 2007. A review of the pterosaur Ctenochasma: taxonomy and ontogeny. Neues Jahrbuch für Geologie und Paläontologie – Abhandlungen, 245(1): 23-31.
Buisonjé de PH 1981.
 Ctenochasma porocristata nov. sp. from the Solnhofen Limestone, with some remarks on other Ctenochasmatidae. Proceedings of the Koninklijke Nederlandse Akademie van Wetenchappen, B, 84 (4): 411-436.

The Disappearance(s) of the Pterosaur Naris

A key distinction between basal pterosaurs and derived “pterodactyloid”-grade pterosaurs is the apparent disappearance of the naris. Typically the naris is said to be “confluent” with the antorbital fenestra. Unfortunately the steps or stages in this disappearance or confluence have never been documented. Here, in this heretical blog, we’ll attempt to remedy that by observation, phylogenetic analysis and comparison.

As discussed earlier, there were at least four origins of the “pterodactyloid”-grade, but there were five disappearances of the pterosaur naris. The fifth occurred in the Pterorhynchus/Darwinopterus clade which, otherwise, did not achieve the “pterodactyloid” grade postcranially. Here we’ll document the naris reduction three (Fig 1) by two (Fig 2).

Disappearance of the naris

Figure 1. Click to enlarge. The disappearance of the naris in scaphognathid pterosaurs.

 

Sordes > Pterorhynchus
Between Sordes and Pterorhynchus the naris was drastically reduced (Fig. 1) as the antorbital fenestra increased its length. The antorbital fenestra extended anteriorly beneath the naris for half of its length in both cases. It is difficult to determine if a naris was present or not in Kunpengopterus through Wukongopterus, sisters to Darwinopterus.

Scaphognathus > Germanodactylus and Pterodactylus
Between the n109 specimen of Scaphognathus and Germanodactylus rhamphastinus there appears to be a reduction and splitting of the naris into a primary naris (posteriorly) and a secondary naris (anteriorly). The nasal and jugal appear to extend to the anterior (secondary) naris.

Scaphognathus > Cycnorhamphus and Zhenyuanopterus
Between the n110 specimen of Scaphognathus and Cycnorhamphus and Zhenyuanopterus the pattern of narial reduction duplicates the previous pattern. Often in ornithocheirids the tiny anterior naris is completely eliminated by bone growth sealing the opening.

Disappearance of the naris in pterosaurs

Figure 2. Click to enlarge. The disappearance of the pterosaur naris in the Dorygnathus clade

 

Dorygnathus > Pterodaustro
In Dorygnathus through Pterodaustro the naris become slit-like, moves anteriorly and is reduced in “pterodactyloid” grade taxa.

Dorygnathus > Zhejiangopterus
In Dorygnathus through Zhejiangopterus the naris became smaller and moved anteriorly. Several holes appeared in derived skulls, but these could be artifacts and/or erosion.

Naris? Or Skull Erosion?
The difficulty in searching for the naris lies in trying to determine what is a tiny naris and what is a tiny gap or erosion of the bone. The nearby anterior processes of the nasal and jugal provide some guide, but the evidence is often equivocal. Comparisons to sister taxa are also helpful. In any case, I see no evidence for erosion of the maxillary process meeting the nasal that separated the naris from the antorbital fenestra. Thus there was no confluence.

The Reduction of the Naris in Birds
Several birds, like the diving gannett (Sula bassana), pelican (Pelicanus) and the sifting spoonbill (Ajaia ajaia), have reduced their naris to a slit or eliminated it entirely. Most other birds had a large naris separated from the antorbital fenestra. Others, such as the cassowary (Casuarius casuarius) had a large confluent naris and antorbital fenestra. These bird skulls can be seen here.

MacDonald (2009) reported, “The gannet has well-developed secondary external nares to compensate for the primary ones which are occluded. It is questionable if this occlusion is a direct consequence of the habit of high diving. Occlusion of the external nares apparently limits the function of the nasal glands as salt excreting organs.” According to Hieronyomous (2009) inspired air does not enter the naris in certain birds with sealed nares, rather air enters the throat directly.

The Reduction of the Naris in Pterosaurs
Rather than confluence, the naris in many pterosaurs simply became so small that it became difficult to segregate from bone destruction and crushing. If the reduction of the naris in pterosaurs followed (by convergence) the pattern in birds, it would appear that taxa that dipped or drove their beaks into water reduced the naris. That seems reasonable when looking at the gannett-like germanodactylids. However the initiation of naris reduction in four out of five clades occurred during phylogenetic size reductions at the bases of four “pterodactyloid”-grade clades. So tiny pterosaurs are the key to naris reduction. Subsequent longer-rostrum and overall larger taxa simply inherited a small naris from their smaller and shorter rostrum ancestors. Pterorhynchus is the exception. Its predeccessor, Sordes, was smaller and had a large naris.

Did Pterosaurs Breathe Through Their Nostrils?
If they had big nostrils, yes. Tiny nostrils, hmm, probably not. Along with a reduction in naris size and elongation of the jaws there is a general trend toward filling in the palate. That may have been more of structural innovation than a way to separate air from water and food, considering the reduced size of the naris in these pterosaurs.

Summary
Rather than confluence, the naris in derived pterosaurs was reduced five separate times by convergence. The narial reduction occurred during phylogenetic size reductions and was retained by their larger descendants.

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
MacDonald JD 2009. Secondary external nares of the gannet. Journal of Zoology online 20 Aug 2009. DOI: 10.1111/j.1469-7998.1960.tb05852.x

Hieronymous TL 2009. Comparative Anatomy and Physiology of Chemical Senses in Aquatic Birds in: Sensory Evolution on the Threshold – Adaptations in Secondarily Aquatic Vertebrates. Edited by Thewissen JGM and Nummela S. Berkeley: University of  California  Press.  2008. 351 pp., $75 (cloth). ISBN 978-0-520-252783.

Pterosaur Femur Time

Today we’ll take a look at the pterosaur femur, how it evolved and it’s range of motion in various pterosaurs.

Traditional Views of Basal Pterosaurs
Dr. Mark Witton reported, “… the orientation of the femoral head in basal pterosaurs means that the femur is projected forward, upward and laterally from the acetabulum, thereby causing the sprawling gait for the hindlimbs that acted in concert with the relatively short metacarpals to bring the bodies of these pterosaurs close to any surface they happened to be climbing over.”

Dr. Dave Hone reported, “On the ground the ‘rhamphorhynchoids’ were probably pretty poor. Their large rear membrane would have shackled their hindlegs together making walking difficult, and the shape of their hips and upper legs meant that could only really sprawl and not walk upright.” 

Let’s See What the Fossils Tell Us
Contra the above assertions, the fossils tell us just the opposite. Basal pterosaurs, like Austriadactylus and Eudimorphodon, had a right angle femoral head, as in dinosaurs (Figs. 1 and 2) by convergence. Derived pterosaurs, like Pteranodon and Anhanguera, had a much more obliquely angled femoral head (Fig. 3). The false notion of a “large rear membrane” that purportedly shackled the hind limbs mentioned by Dr. Hone (above) was dealt with earlier here.

Eudimorphodon ranzii femur in medial view

Figure 1. Eudimorphodon ranzii femur in medial view, the head is circular because it is pointed toward the Z axis, at right angles to the plane of the matrix and the rest of the femur.

Femur of Eudimorphodon cromptonellus

Figure 2. Femur of Eudimorphodon cromptonellus illustrating the right angle femoral head. This tiny specimen may be juvenile, hence the incomplete ossification at each end. When the axes of the femoral neck and laterally-oriented acetabulum lined up, an upright configuration was produced.

Pterosaur femur samples. A

Figure 3. Derived pterosaur femur samples. Above, Pteranodon. Below, Anhanguera. Note the oblique angle of the femoral head. When the axes of the femoral neck and laterally-oriented acetabulum lined up in these pterosaurs, a sprawling configuration was produced.

Range of Motion
The range of motion in a pterosaur femur has been of some interest (Padian 1983; Wellnhofer 1988, 1991), impacting the quadrupedal/bipedal debate, among other topics. The discovery of uncrushed pterosaurs has been helpful, but those can’t discount the fossil record of crushed pterosaurs. Preservation in various angles and exposures paints a complete picture confirmed by comparing several sisters.

Padian (1983) proposed that pterosaurs tucked their hind limbs into the body while flying. While possible in basal pterosaurs, and likely while resting, such a configuration would have proven difficult in Anhanguera and Pteranodon with their sprawling femora. Plus reducing the distance between the femur and tibia in flight would have made the uropatagia disappear at a time when they would have been most useful. A more recent hypothesis (Peters 2002) proposed a more widespread femur acting as a horizontal stabilizer, a second wing (Fig. 5), as in the pterosaur sister Sharovipteryx. After all, lizards like Draco take to the air with outspread limbs and pterosaurs were flying lizards.

The Example of Austriadactylus
Austriadactylus
 was another basal pterosaur with a right angle femoral head (Fig. 4). Seen in various views it becomes clear that an upright stance with knees slightly beyond the ankles would have been appropriate given the shapes of the various elements. Contra Witton’s assertions (see above), Austriadactylus was not forced to crouch close to any surface it happened to be climbing over.

Austriadactylus femur. Range of motion.

Figure 4. Austriadactylus femur. Range of motion. The foot was rotated posteriorly out of the airstream. The toes were likely webbed in all pterosaurs. When spread the webbed foot turned into a sail with lateral lift, helping to keep the knee extended even while facing the airstream.

Potential Problems with a Right Angle Femoral Head
While a derived sprawling femur would have had no problem assuming an outstretched flying configuration, I always wondered how a primitive right angle femur would handle it. Seemingly an inverted V-shape would have been all a basal pterosaur could muster. After closer examination (Fig. 4) that turned out to be true, but to less of an extent than I thought earlier. The femur could not rise to the horizontal, but it could come to within 20 degrees. The fact that the femoral head was more spherical in basal pterosaurs enabled this.

Lift from the Pelvis?
In Sharovipteryx and most pterosaurs the ilium does not rise much above the acetabulum. However in Longisquama and basal pterosaurs the anterior and posterior processes of the ilium rise as much as 45 degrees to the horizon or 90 degrees to each other (Fig. 4). Such a pelvis raises the torso and tail, which is ideal for bipedal leaping, as in Longisquama and living lemurs. Not so great though, to have an upright tail while flying. However, such an upright ilium also provides the leverage for the thigh muscles to lift (abduct) the hind limbs for flight. Later pterosaurs evidently did not need so much leverage with sprawling femora more aerodynamically shaped to provide their own lift in the airstream.

Arthurdactylus dorsal view.

Figure 5. Arthurdactylus in dorsal view while flying. Note the sprawling hind limbs acting like horizontal stabilizers.

More About Derived Pterosaurs
Dr. Hone also reported, “The pterodactyloids had no such problems, as can be seen by their extensive fossil record of footprints. They had split their rear membrane in two freeing the legs which were brought under the body to allow them to walk far more effectively than their predecessors.” Let’s put more data on these assertions. While true that the feet were brought under the body (as in ALL pterosaurs, see Fig. 4), the knees in Pteranodon were actually configured further laterally than in basal pterosaurs. No problem. As you can see by the illustration below (Fig. 6), based on a 3D reconstruction of a complete skeleton, no matter the sprawl of the knees, as long as the knees were bent at right angles and the knees were below the plane of the acetabulum the feet remained beneath the body. This is simple engineering and standard operating procedure for all pterosaurs.

Standing Pteranodon

Figure 6. Standing Pteranodon. Note the sprawling femora do not hinder the bipdal stance. And, yes, Pteranodon likely placed its hands on the ground while walking, but so far anterior they could provide no forward thrust, only support.

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 and Tomida Y 2000. Description of a New Species of Anhangueridae (Pterodactyloidea) with Comments on the Pterosaur Fauna from the Santana formation (Aptian-Albian), Northeastern Brazil. National Science Museum, Tokyo, Monographs, 17: 1-135.
Jenkins FA Jr, Shubin NH, Gatesy SM and Padian K 1999. A primitive pterosaur of Late Triassic age from Greenland. Journal of the Society of Vertebrate Paleontology 19(3): 56A.
Jenkins FA Jr, Shubin NH, Gatesy SM and Padian K 1999. A diminutive pterosaur (Pterosauria: Eudimorphodontidae) from the Greenlandic Triassic. Bulletin of the Museum of Comparative Zoology, Harvard University 155(9): 487-506.
Padian K 1983. A functional analysis of flying and walking in pterosaurs. Paleobiology 9:218.
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277-301.
Wellnhofer P 1988. Terrestrial locomotion in pterosaurs. Historical Biology 1: 3.
Wellnhofer P 1991. The Illustrated Encyclopedia of Pterosaurs. (Salamander Books, London).
Wild R 1978. Die Flugsaurier (Reptilia, Pterosauria) aus der Oberen Trias von Cene bei Bergamo, Italien. Bolletino della Societa Paleontologica Italiana 17(2): 176–256.

wiki/Eudimorphodon

Lucky Number 13.

Wellnhofer’s (1970) catalog of “pterodactyloid” Solnhofen pterosaurs included a putative Pterodactylus specimen B St 1878 VI 1 (Zittel 1882) to which he applied the number “13.” Earlier we discussed the hypothesis that the genus “Pterodactylus” was a taxonomic wastebasket, that included several taxa within the genus Pterodactylus and several that did not. One of the latter that stands alone is #13. In the present tree, it was derived from the SMNK 6592 specimen of Germanodactylus and was basal to Nyctosaurus, Pteranodon, Eopteranodon and Eoazhdarcho (Figure 2).

B St 1878 VI 1, #13

Figure 1. B St 1878 VI 1, #13 in the Wellnhofer (1970) catalog.

Not a Pterodactylus but a Reduced Germanodactylus
The single large tooth at the tips of the jaws, the (albeit tiny) posterior skull crest, the ventral keel of the mandible, the shapes of the pelvis and sternum, and the proportions of all ten digits are traits separating #13 from the genuine Pterodactylus clade. Moving #13 back to Pterodactylus adds 35 steps in the large pterosaur tree. The reduced size of #13 is a common, if not typical pattern preceding morphological change (contra Hone and Benton 2006). In this case the change produced Eopteranodon and Eoazhdarcho on one branch and Muzquizopteryx plus Nyctosaurus on the other. Note the hatchet-shaped deltopectoral crest (as in Nyctosaurus) on #13. The lack of scapulocoracoid fusion in #13 (a biproduct of phylogenetic size reduction) gave rise to a clade with a similar lack of fusion up to but not including the KJ nyctosaurs.

 No. 13 and its sisters

Figure 2. No. 13 and its sisters, Germanodactylus, Muzquizopteryx and Eopteranodon. Click to enlarge.

The Size Thing
Figure 2 shows #13 with its successors, Muzquizopteryx and Eopteranodon, to scale and two to three times its height. In like manner, the Germanodactylus successor, a basal Pteranodon, was three times its size. The hyper-elongated metacarpus of Nyctosaurus finds its origins in Muzquizopteryx and Eopteranodon. The same trait in Pteranodon owes its origin either to a sister to Eopteranodon or to an unknown transitional series derived from Germanodactylus following a convergent evolutionary pattern.

Successors were Toothless
The phylogenetic successors of both Germanodactylus and #13 were all toothless. How this came to be is not illustrated in the fossil record, but generally the teeth become more numerous and smaller prior to disappearance.

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
Hone and Benton 2006. Cope’s Rule in the Pterosauria, and differing perceptions of Cope’s Rule at different taxonomic levels. Journal of Evolutionary Biology 20(3): 1164–1170. doi: 10.1111/j.1420-9101.2006.01284.x
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.
Zittel KA 1882.  Über Flugsaurier aus dem lithographischen Schiefer Bayerns. Palaeontographica 24: 47-81.

The Tritosauria – An Overlooked Third Clade of Lizards

Traditionally there have been just two lizard clades in the Squamata. The Iguania included Iguana, Draco, Phrynosoma and other similar lizards. The Scleroglossa included Tupinambis, Chalcides, Varanus, Heloderma and all the snakes and amphisbaenids. Squamate outgroups within the Lepidosauria included members of the Rhynchocephalia (such as Sphenodon) and the basal lepidosaur, Homoeosaurus, which probably appeared in the Permian, but is only known from the Late Jurassic.

Traditional Nesting
Wikipedia reports the following about the Squamata, “Squamates are a monophyletic  group that is a sister group to the tuatara. The squamates and tuatara together are a sister group to crocodiles and birds, the extant archosaurs.” This is the traditional concept, but testing this in a larger study finds that lizards and archosaurs are not closely related. Not by a long shot.

The Tritosauria, a new lizard clade that was previously overlooked.

Figure 1. Click to enlarge. The Tritosauria, a new lizard clade that was previously overlooked.

The New Heretical Tritosauria
The large study (Peters 2007) recovered a third clade of squamates just outside of the Squamata (Iguania + Scleroglossa), but inside the Lepidosauria (which includes Sphenodon and the other Rhynchocephalia). At the base of this third clade, called the Tritosauria (“third lizards”), are three very lizardy forms, none of which had fused proximal ankle bones, a trait shared by most squamates (at least those that have legs!). Lacertulus, Meyasaurus and Huehuecuetzpalli are known from crushed but articulated fossils. Lacertulus was considered a possible biped (Carroll and Thompson 1982) based on its long hind legs. It is likely that Huehuecuetzpalli (Reynoso 1998) was also a biped. All three were considered close to the base of the lepidosauria, not closely related to any living lizards.

The Tritosauria
A Clade of Misplaced and Enigmatic “Weird-Ohs”

Phylogenetically following Huehuecuetzpalli three distinct clades emerge within the Tritosauria. Some of these were formerly considered “prolacertiforms” (Peters 2000), but now we know that none are related to ProlacertaAll three subclades have some pretty weird members.

The Tanystropheidae
This clade was named by Dilkes (1998) to include “the most recent common ancestor of MacrocnemusTanystropheus and Langobardisaurus and all of its descendants.” Clade members include several long-necked taxa, some of which, like Dinocephalosaurus, preferred swimming to walking. Tanystropheus was the largest, attaining 4.5 meters in length.

The Jesairosauridae
This clade includes Jesairosaurus (Jalil 1991) and the drepanosaurs, from Hypuronector to Drepanosaurus.  This clade included several arboreal, hook-tailed taxa with short-toed feet that were able to grasp slender branches in their slow-motion quest for insects. All were rather small.

The Fenestrasauria
This clade was named by Peters (2000) to include “Cosesaurus, Preondactylus, their common ancestor and all of its descendants.” This clade started off with bipeds that flapped their arms, probably for display during mating rituals because some members, like Longisquama were exotically decorated with extradermal membranes and plumes. Powered gliding (as in Sharovipteryx) was followed by flapping flight in pterosaurs, the first flying vertebrates. Several pterosaurs secondarily developed a quadrupedal pace. Quetzalcoatlus was the largest tritosaur, attaining a wingspan of 10 meters.

Summary
Due to the wide gamut and large inclusion list of the present phylogenetic analysis, many former enigmas, mismatches and leftovers came together in a new clade of lepidosaurs that was previously overlooked. Together, the Tritosauria include some of the strangest and, at times largest, of all lizards. Hyper-elongated necks and hyper-elongated fingers, together with experiments in both a sedentary marine lifestyle (Dinocephalosaurus) and a homeothermic aerial lifestyle (Dimorphodon, for example) make this a truly dynamic and diverse clade. Some of these out-of-the-ordinary morphologies seem to have been kick-started by early experiments with bipedalism. While the arboreal niches of drepanosaurs and pterosaurs are relatively easy to identify, the long-necked tanystropheids may also have used bipedalism and a long neck to reach into tree boughs to snatch prey, creating their own arboreal niche.

Unfortunately, only pterosaurs and Huehuecuetzpalli survived the end of the Triassic and they did not survive the end of the Cretaceous. So tritosaurs are the only major clade of lizards that is extinct today.

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
Carroll and Thompson 1982. A bipedal lizardlike reptile fro the Karroo. Journal of Palaeontology 56:1-10.
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 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.

Tapejara Toes

New Postcranial Tapejara Material Reported
Tapejara was an Early Cretacous pterosaur known from several crested skulls, but post-cranial material has not been published. A recent paper on some post-cranial material and a mandible of Tapejara (Elgin and Campos 2011) included some “incomplete” pedal material. The study of pterosaur feet has been a specialty (Peters 2000, 2010, 2011), so recovering more data from this fossil was deemed important.

Original illustration of the Taejara fossil

Figure 1. Original tracing of the Taejara fossil (SMNK PAL 3986) from Elgin and Campos (2011). Gray added to focus attention on the pedal elements. 

Original Tracing
Elgin and Campos (2011) traced the fossil (SMNK PAL 3986) and reported three metatarsals, four proximal phalanges, one distal phalanx and one ungual (Figure 1.)

DGS – Digital Graphic Segregation
One of the authors (Herbert Bruno Campos) was kind enough to send me a jpeg of the fossil upon which I was able to trace using the much maligned Photoshop and DGS (Digital Graphic Segregation) method. The DGS tracing revealed several additional elements, essentially all the remaining phalanges and unguals plus a fourth and fifth metatarsal (mt 3 and mt 5, Figure 2).

 

Color image of SMNK PAL 3986

Figure 2. Color image of SMNK PAL 3986 (Tapejara) with pedal elements colorized.

Reconstruction
Digitally shifting the colored elements into their original positions (Figure 3) recovers a pes with unguals 2-4 aligned. Discontinuous PILs can be drawn through digits 2-4 that intersect p1.1.

 

Tracing of the in situ Tapejara pedal elements

Figure 3. Tracing of the in situ Tapejara pedal elements and a reconstruction of the original foot with PILs (parallel interphalangeal lines) added.

Comparison to Other Pterosaurs
The new Tapejara foot reconstruction demonstrates many similarities with other sister taxa feet (Figure 4). These also had discontinuous PILs that intersected p1.1 and several aligned unguals 2-4. This lends confidence to the identification, tracing and reconstruction of the Tapejara elements.

Figure 4. Comparing the Tapejara reconstruction with sister taxa.

Figure 4. Comparing the Tapejara reconstruction with sister taxa.

Filling in the Gaps
Pterosaur feet are rarely studied and reconstructed, so this exercise added to our knowledge of this clade. The DGS method using a photograph provided more data than original observation. The reconstruction was tested by comparisons to sister taxa.

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
Elgin RA and Campos HBN 2011. A new specimen of the azhdarchoid pterosaur Tapejara wellnhoferi. Historical Biology (advance online publication) DOI:10.1080/08912963.2011.613467
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2010. In defence of parallel interphalangeal lines. Historical Biology iFirst article, 2010, 1–6 DOI: 10.1080/08912961003663500
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification
Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605

Longisquama Wings

Longisquama: Almost Too Fascinating. And a Lot of Work!
The general morphology of Longisquama has been difficult to ascertain. Sharov (1970), Senter (2003) and Martin (2000) provided simple tracings without much resolution. Peters (2000) added details, but was unable to actually “see” many details due to inexperience. There I said it. Okay, I’m better now than I was 12 years ago. I’ve got more under my belt.

A dozen years ago I was also under the existing paradigm that the posterior half of Longisquama was missing, as Sharov (1970) reported. No one ever suspected that Longisquama had the long hind legs of a biped and the wings of a pterosaur. Even when they are traced out (Figure 1), they are still difficult to see and were mistaken for displaced plumes by Sharov (1970).

New tracings of Longsiquama

Figure 1. Click to enlarge. New tracings of Longsiquama (B) soft tissues and (C) bones.

Persistence Pays Off!
A new tracing of Longisquama (Figure 1) reveals long hidden details including the tail, pelves, two hind limbs and two folded wings framed by elongated wing fingers (Figure 2). Workers who have seen this fossil claim they did not see this level of detail. That’s because the human eye, even aided by a binocular microscope, cannot segregate and aggregate all the chaos and layers of detail in this fossil. It takes a computer and DGS (digital graphic segregation) to tease out each bone one at a time. By digitally tracing the elements the details emerge and form a complete picture with matching left and right elements that confirm identification. This technique has been widely criticized, but the results speak for themselves.

Despite the “weirdness” of Longisquama, there are very few autapomorphies present. Instead, nearly every trait bridges the morphological gap between Cosesaurus and pterosaurs. It took persistence and the recognition of past errors to make these tracings come together. Follow these methods and the results should be identical.

The wings of Longisquama

Figure 2. Click to enlarge. The wings of Longisquama digitally segregated, including soft tissue. A. In situ. B. Both forelimbs. C. The right forelimb. D. The left forelimb. All elements match left to right.

The “proto-wings” of Longsiquama were midway in size and shape between the nonvolant forelimb of Cosesaurus and the fully-fledged wings of basal pterosaurs (Figure 3). Fingers 1-3 were quite a bit larger than those of either sister taxa. Metatarsal 4 was axially rotated so the finger four flexed in the plane of the wing, as in pterosaurs, rather than toward the palm, as in all other tetrapods. The large claws on the hands suggest an arboreal habitat.

Figure 1. 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.

Cosesaurus and Longisquama are the Archaeopteryx and Microraptor of pterosaurs, demonstrating the first steps in the origin of flight for the first volant vertebrate clade, the Pterosauria.

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