Inaccuracy? Or Asymmetry?

While gathering data for the TM 6920/21 (No. 38 in the Wellnhofer 1975 catalog), I restored the published tracings of the feet, both left and right,. The PIL patterns were nearly identical, but some of the phalanges did not match left to right. The differences were slight, but certainly present. The question is: does this represent asymmetry? Or inaccuracy? Or both?

The left and right feet of the no. 38 specimen of Rhamphorhynchus

Figure 1. The left and right feet of the no. 38 specimen of Rhamphorhynchus, TM 6920/21. Most of the metatarsals and phalanges were identical, but a few , here colored, were not. Does this represent Wellnhofer’s inaccuracy? Or asymmetry in Rhamphorhynchus? Someone with access to the specimen will have to determine this.

And, yes, this level of detail scrutiny is important.
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
Wellnhofer P 1975a-c. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33.Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149: 1-30.

wiki/Rhamphorhynchus

More on Yale’s Rhamphorhynchus

Rhamphorhynchus phyllurus,

Figure 1. Rhamphorhynchus phyllurus, courtesy of W. Gearty and D. Brinkman.

One of the best soft tissue preservations known for pterosaurs can be found at Yale University. The specimen YPM VP 001778 (no. 33 in the Wellnhofer 1975 catalog), is preserved dorsal side down with many elements buried, missing or covered by soft tissue. The tail vane is also quite well preserved. The bone around the naris is likely missing, artificially enlarging it. The foot phalangeal patterns are unique. This specimen is closest to the MTM V2008.33.1 specimen (among the dozen or so tested). I’ll get these nested specimens presented in the large pterosaur tree this weekend and do a comparison among several shortly.

Reconstruction of Rhamphorhynchus phyllurus.

Figure 2. Reconstruction of Rhamphorhynchus phyllurus. The great size of the sternal complex is noteworthy. The enlarged naris is likely an artifact. Pedal digit 4 is atypically longer than digit 3 and extends just as far. 

Soft Tissue
These wing membranes do not support a deep chord reconstruction. Note the upper membrane (as preserved) is directed at the wrist (likely due to twisting), then fades. Bottom line, close to the torso preservation is not good.

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.

Reference
Wellnhofer P 1975a-c. Teil I.
 Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33.Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149: 1-30.

wiki/Rhamphorhynchus

Is this a wing ungual? Rhamphorhynchus phyllurus

This could be a wing tip ungual on Rhamphorhynchus phyllurus

Figure 1. This could be a wing tip ungual on Rhamphorhynchus phyllurus, the famous soft tissue Rhamph in the Yale collection, YPM VP 001778. Unfortunately further picking at the matrix is prohibited. Thanks to William Gearty and Dan Brinkman at Yale for this photo. If anyone out there wants to send in similar pictures of wingtips in their collections, with and without unguals, please send them to info@reptileevolution.com

With its tip still buried, this possible intact wing ungual from Rhamphorhynchus phyllurus YPM VP 001778 remains an intriguing artifact that could solve an age old question. Unfortunately, further excavation of the last few grains of matrix over the possible tip have been prohibited. So, is this enough evidence for an ungual? Or is this something else?

Sans the ungual, this wing tip, like so many others, bears a trochlear joint. Obviously there’s no reason for a trochlear joint unless there’s just one more bone distal to it.

Sorry for the short post. It’s been a busy week.

The Largest Rhamphorhynchus Specimens

Conspecific?
Bennett (1975) determined that all Rhamphorhynchus specimens were conspecific with the various sizes and shapes representing the two genders and juveniles. More recently Prondvai et al (2012) followed this hypothesis in their bone histology study. Previously we looked at the smallest Rhamphs and determined that none resembled known larger specimens enough to consider them juveniles of same. Today we’ll look at the largest Rhamphs to determine if any of them might be considered conspecific.

The largest Rhamphorhynchus specimens

Figure 1. A sampling of the largest Rhamphorhynchus specimens to scale. If Bennett (1995) and Prondvai et al. (2012) are correct, then these specimens should look conspecific. But they don't. The smaller ones would be juveniles and n81 would be the only fully mature individual. That doesn't make sense. It doesn't take a detailed view to see they are as different from one another as various species or even genera of birds.

So, Which of These Are Juveniles?
Above (Fig. 1) are shown several of the largest Rhamphorhynchus specimens. If these are all conspecific then the individual variation extends throughout the skeleton to the pedal phalangeal ratios. Like Pteranodon, Pterodactylus and several other purported genera, this clade needs a complete revision, looking at and reconstructing individuals.

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 1995. A statistical study of Rhamphorhynchus from the southern limestone of Germany: year classes of a single large species. Journal of Vertebrate Paleontology 69: 569–580.
Prondvai E, Stein K, Ösi A, Sander MP 2012. Life History of Rhamphorhynchus Inferred from Bone Histology and the Diversity of Pterosaurian Growth Strategies. PlosOne. online pdf

Another “Wingless, Juvenile” Rhamphorhynchus

Rhamphorhynchus sp. (BSPG 1960 I 470a) was considered a juvenile without a head or wings. The specimen appears to be largely unprepared. Earlier we looked at another purportedly wingless Rhamphorhynchus (BML-37012, No. 85 in the Wellnhofer 1975 catalog), also from the Solnhofen formation, in which the wings were buried.

juvenile Rhamphorhynchus BSPG 1960 I 470a in situ

Figure 1. Click to enlarge. The purported juvenile Rhamphorhynchus BSPG 1960 I 470a in situ (above) and traced in black. Buried elements (skull, wings) traced in gray. This specimen demonstrates the value of using Digital Segregation to trace buried elements. Digging into the matrix using this map should reveal more bones.

As Before…
When a fossil specimen is discovered by splitting Solnhofen limestones, typically many bones remain invisible, hidden beneath a thin blanket of limestone at the separation layer. Preparators can usually create a precise outline of the specimen, even when the bones are rather deep, because preparators can see the general direction of the fossil (head on one end, tail on the other) and the exact location of other elements are often betrayed by a slight rise in the matrix. Like a blanket over a child in bed, the limestone tells you exactly where to dig.

Above, Rhamphorhynchus intermedius (n28 in the Wellnhofer 1975 catalog) was recovered as a sister to BSPG 1960 I 470, below.

Figure 2. Above, Rhamphorhynchus intermedius (n28 in the Wellnhofer 1975 catalog) was recovered as a sister to BSPG 1960 I 470, below. If your computer screen is set to 72 dpi these two specimens will be shown at full scale. Both are among the most primitive known species of Rhamphorhynchus. Unlike the BML specimen reconstructed earlier, the BSPG specimen had a relatively small skull, based on the size of the mandible.

Reconstruction and Phylogenetic Analysis
We can’t just trace ephemeral elements without testing them in a reconstruction and phylogenetic analysis. The reconstruction is shown in Figure 2 alongside its phylogenetic sister, Rhamphorhynchus intermedius. The relatively short neck and robust torso mark these as primitive for the genus. The pedal phalangeal patterns are also primitive. The very wide jaws of the BSPG specimen are similar to those found in a more derived sister, also tiny, the BMM specimen.

A better test would be for a preparator to dig into the matrix where I have mapped the buried elements.

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
Wellnhofer P 1975a. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. – Paleontographica A 148: 1-33.
1975b. Teil II. Systematische Beschreibung. – Paleontographica A 148: 132-186.
1975c. Teil III. Paläokolgie und Stammesgeschichte. – Palaeontographica 149: 1-30.
Wellnhofer P 1991. The Illustrated Encyclopedia of Pterosaurs. London, Salamander Books, Limited: 1-192.

Not Another Rhamphorhynchus Growth Series Without a Phylogenetic Analysis!

Prondvai et al. (2012) reported on the bone histology of five Rhamphorhynchus specimens of various sizes (Fig. 1). They concluded “The initial rapid growth phase early in Rhamphorhynchus ontogeny supports the non-volant nature of its hatchlings, and refutes the widely accepted ‘superprecocial hatchling’ hypothesis. We suggest the onset of powered flight, and not of reproduction as the cause of the transition from the fast growth phase to a prolonged slower growth phase.”

Regarding the bone histology of the specimens, Prondvai et al. (2012) reported, “The ontogenetic validity of the smallest size category of Bennett is clearly supported by the overall microstructure found in the bones of the three small specimens BSPG 1960 I 470a, BSPG 1877 X I, CM 11433.”

Earlier Bennett (1995) reported on a growth series with distinct stages for Rhamphorhynchus.

A list of Rhamphorhynchus specimens studied by Prondvai et al. (2012).

Figure 1. A list of Rhamphorhynchus specimens studied by Prondvai et al. (2012). They said this was an ontogenetic series, but the feet (Fig. 2) tell another tale. Note, some specimens were actually headless. One, the IPB specimen, is a single hind limb. In an apparent bid to completely ignore morphological distinctions, all these reconstructions are identical, simply scaled larger or smaller. The largest is 5x the size of the smallest. Pterosaur adults are typically 8x larger than hatchlings.

Not Ontogenetic, But Phylogenetic
Unfortunately and without realizing it, Prondvai et al. (2012) employed a phylogenetic series, not an ontogenetic one. None of their large and small specimens were virtually identical to one another.That’s a requirement for an ontogenetic series in which the taxa grew isometrically as demonstrated by all known pterosaur embryos and several juvenile pterosaurs including Tupuxura and Pteranodon. The allometric growth hypothesis is not supported by phylogenetic analysis or detailed anatomical studies (see Fig. 2). Like Bennett (2007) before them, Prondvai et al. (2012) did not perform a phylogenetic analysis to determine whether or not their study specimens were conspecific or not. Such an analysis is critical. The lack of such an analysis places doubts over the results.

Rhamphorhynchus feet

Figure 2. Click to enlarge. These are the feet of the five Rhamphorhynchus specimens employed as an ontogenetic series by Prondvai et al. (2012). As you can see, the various proportions are not close enough in morphology to possibly be an ontogenetic series. Some have longer metatarsals, others have distinct ratios among the phalanges. Instead, these represent samples from the small and large phylogenetic species within Rhamphorhynchus. PILs are continuous in most sets. Not to scale with one another.

The Feet Are Like Fingerprints
As we learned earlier, if the feet were identical to one another, or nearly so, they would be more closely related as in Pterodaustro, but here, in Rhamphorhynchus, they are not. The specimens were found in different areas at different times. They were not part of a single nesting colony. They were not an ontogenetic series. Prondvai et al. (2012) was evidently not aware that the traditional allometric growth hypothesis cannot be supported except by the power of tradition. So, unfortunately, the Prondvai et al. (2012) study ended up comparing different species, some small, precocious and fast-growing, others larger and slower growing, just like various birds of various sizes. Click here to see what other sister Rhamphorhynchus specimens looked like in lateral view in phylogenetic order. You’ll notice several other non-conspecific differences. Descriptions and comparative differences are included there.

Could The Small Ones Fly?
Regardless of their ontogeneic age, did the smallest Rhamphorhynchus specimens fly? Prondvai et al. (2012) say no. They said the small pterosaurs needed a certain “somatic maturity to get airborne.” The fact that the small rhamphs had immature bone tissue is not unexpected. They became sexually active at an earlier stage than their larger sisters, both preceding and succeeding them. They never got big. Their eggs would have been correspondingly small. They likely did not live as long, but produced more eggs earlier. Their wings were not shorter and their sternal complexes were not smaller. They present specimens were as able to fly as their larger sisters.

Rhamphorhynchus hatchlings (especially the hatchlings of small adults), however, were not able to fly (due to the threat of desiccation) until reaching the critical size of the smallest known adult pterosaur, B St 1967 I 276, Wellnhofer’s No. 6, as described earlier.

You can read Dr. Hone’s interview with Dr. Edina Prondvai 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 1995. A statistical study of Rhamphorhynchus from the southern limestone of Germany: year classes of a single large species. Journal of Vertebrate Paleontology 69: 569–580.
Prondvai E, Stein K, Ösi A, Sander MP 2012. Life History of Rhamphorhynchus Inferred from Bone Histology and the Diversity of Pterosaurian Growth Strategies. PlosOne. online pdf

A Pterosaur Without Limbs and Where to Find Them

BML-37012 (No. 85 in the Wellnhofer 1975 catalog) was considered to be a juvenile Rhamphorhynchus preserved largely without limbs (one femur listed). This small specimen (skull length: 2.8 cm) was also presented in Wellnhofer’s (1991) Encyclopedia of Pterosaurs. It appears to be unprepared.

BML-37012 (n45 in the Wellnhofer 1975 catalog) is a small and primitive Rhamphorhynchus

Figure 1. BML-37012 (n85 in the Wellnhofer 1975 catalog) is a small and primitive Rhamphorhynchus, phylogenetically close to the BMM specimen. Above: the in situ specimen, apparently without limbs. Below: A DGS tracing indicating where to dig for the limbs. Blanketing layers of Solnhofen limestone indicate where one will find more bone slightly beneath the surface. Determining where fossils may be just below the surface  by looking for bumps in the matrix is an age-old technique used by fossil preparators. Image from Wellnhofer 1991. Enlargements and overlays available by request. 

Solnhofen Preservation
When a fossil specimen is discovered by splitting Solnhofen limestones, typically many bones remain invisible, hidden beneath a thin blanket of limestone at the separation layer. Preparators can usually create a precise outline of the specimen, even when the bones are rather deep, because preparators can see the general direction of the fossil (head on one end, tail on the other) and the exact location of other elements are often betrayed by a slight rise in the matrix. Like a blanket over a child in bed, the limestone tells you exactly where to dig.

DGS Preview
The Digital Graphic Segregation (DGS) method permits an increase in contrast in the image of the matrix surrounding the fossil. This better indicates where the bumps and valleys are in the limestone blanketing the fossil. Doing so I was able to trace a complete and largely articulated forelimb disarticulated from the rest of the fossil and a complete hindlimb tucked close to the body. Another tibia and pedal digit 4 is twisted and tucked in behind the lumbar region of the fossil, visible without DGS. This particular tibia may be the previously identified femur. Pedal digit 4 was closely aligned with the deeper ilium and so was overlooked. While others dismiss and decry this method using Adobe Photoshop, it is exactly what preparators have been doing by eye for generations.

 

Figure 2. Reconstruction of Rhamphorhynchus specimen BML-37012 (n85 of Wellnhofer 1975).

Figure 2. Reconstruction of Rhamphorhynchus specimen BML-37012 (n85 of Wellnhofer 1975).

Reconstruction
A digital reconstruction of the fossil looks much like other similar Rhamphorhynchus specimens, like the BMM specimen and B St 1959 I 400 (n10 in the Wellnhofer 1975 catalog). Making such comparisons is one test that confirms the identification of the bones viewed through the blanketing limestone. It would also be a good test of the method if someone with the proper tools dug into the limestone to find the bones beneath the surface.

Description and Distinctions
The BML specimen has larger fingers 1-3 and very large eyes. So was it nocturnal? Did it compete with similarly built and sized anurognathids? Interesting questions that haven’t been brought up before under the false paradigm that such short-snouted rhamphs were simply juveniles of larger specimens. Smaller rhamphs have been dismissed as juveniles, but phylogenetic analysis does not match them to older adults. Rather it finds the small ones were related to each other. I know of no Rhamphorhynchus specimens that are identical to adults only smaller, as in Pterodaustro and PteranodonIf you know of any, please send the data.

Juvenile or Not?
As we learned earlier, hatchling pterosaurs, like juvenile tritosaur lizards in general, are virtual matches to adults. Phylogenetically smaller pterosaurs (those with larger ancestors) generally had a smaller rostrum and larger eyes because they developed in a shorter time in smaller eggs, thus retaining these more embryonic traits as hatchlings and adults. Later, as their descendants increased in utero development time, egg size increased and jaw length generally increased relative to overall size. This specimen, No. 85, matches sister taxa in morphology and is part of an uninterrupted size continuum and so it may be considered an adult. Hatchlings would have been one-eighth the size according to pelvic opening size.

References
Wellnhofer P 1975a. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. – Paleontographica A 148: 1-33.
1975b. Teil II. Systematische Beschreibung. – Paleontographica A 148: 132-186.
1975c. Teil III. Paläokolgie und Stammesgeschichte. – Palaeontographica 149: 1-30.
Wellnhofer P 1991. The Illustrated Encyclopedia of Pterosaurs. London, Salamander Books, Limited: 1-192.