A basal ornithocheirid from Lebanon

Several basal ornithocheirids are coming out of Lebanon. This one is more complete than most. It is the most basal form I know of with tiny feet. And it’s pretty small for an ornithocheirid.

Figure 1. a basal ornithocheirid, undescribed, from Lebanon.

Figure 1. A  basal ornithocheirid, undescribed, from Lebanon. Probably a full time flyer, but not very large. The skull is about 4 inches long.

More basal ornithocheirids include the JZMP embryo and Yixianopterusboth of which have more typically sized feet and wings. Earlier we looked at the common ancestors of cycnorhamphids and ornithocheirids, including the tiny pterosaur misnamed Pterodactylus? pulchellus.

Here’s a opportunity to discuss fossil interpretation.

Figure 1. Tracing the coracoid and scapula on the fossil. Note the scapula is way to short. The proximal knob, otherwise just a piece of bone here, is identified.

Figure 1. Tracing the coracoid and scapula on the fossil. Note the scapula is way to short unless extended as shown. The proximal knob of the scapula, the part that goes in the notarium, is identified here. Otherwise, it’s just a piece of bone. This is an instance of an educated guess, one that appears to make sense.

Sometimes fossils are less than complete. Sometimes bones go under other bones. Sometimes chunks of matrix that contain bones do not make it back to the lab. Here’s where best guesses come into play, as in figure 1. I’m pretty sure that small piece of bone over the coracoid is the proximal scapula. Let me know if you think you have a better idea or identification here.

New Farlow et al. (2014) Poposaurus foot paper

Farlow et al. (2014) has a new paper on the foot of the poposaurid, Poposaurus.

Figure 1. Revised skull reconstruction for the PEFO specimen. Here the anterior is considered a premaxilla. Those teeth are shaped like triangles, but they are very deeply rooted and exposed very little, which casts doubts on its hypercarnivory.

Figure 1. Poposaurus in lateral view. This dinosaur like reptile really is a dinosaur with a calcaneal heel.

From their abstract:
“The crocodile-line basal suchian Poposaurus gracilis had body proportions suggesting that it was an erect, bipedal form like many dinosaurs, prompting questions of whether its pedal proportions, and the shape of its footprint, would likewise “mimic” those of bipedal dinosaurs.

Bivariate and multivariate analyses of phalangeal and digital dimensions showed numerous instances of convergence in pedal morphology among disparate archosaurian clades.

Overall, the foot of Poposaurus is indeed more like that of bipedal dinosaurs than other archosaur groups, but is not exactly like the foot of any particular bipedal dinosaur clade.” 

Included is a comparison with other archosaur taxa, (Fig. 1). Note Terrestrisuchus has no calcaneal heel. It develops in the derived Protosuchus and also poposaurid dinosaurs, according to the large reptile tree.

Figure 1. Archosaur feet divided into traditional croc-line and bird-line clades

Figure 1. Archosaur feet divided into traditional croc-line and bird-line clades

These feet can be reordered according to the large reptile tree (Fig. 2). Though many taxa are missing that would fill in morphological gaps, the general trends are more clear here.

Figure 2. Same feet, reordered according to the large reptile tree. Only Terrestrisuchus and Protosuchus are croc-like archosaurs here. Poposaurs are basal dinosaurs.

Figure 2. Same feet, reordered according to the large reptile tree. Only Terrestrisuchus and Protosuchus are croc-like archosaurs here. Poposaurs are basal dinosaurs. Silesaurus converged with theropod dinos, as did Brachylophosaurus. Note the lack of a calcaneal heel on Terrestrisuchus, a basal croc and the development of one on Protosuchus. In similar fashion poposaurid dinosaurs developed a calcaneal heel. 

Farlow et al. noted several instances of convergence (homoplasy). Indeed homoplasy is present here, even in this small sample.

On a separate note, 
Farlow et al. was kind enough to publish a radiograph of an Alligator. I added PILs and they are quite precise in this living reptile.

Figure 3. Radiograph of Alligator foot with PILs (parallel interphalangeal lines) added. Hone and Bennett tried to argue against the presence of PILs but did not have the nerve to show a foot with more than three toes.

Figure 3. Radiograph of Alligator foot with PILs (parallel interphalangeal lines) added. Seems rather clear that such lines representing phalanges working in sets is indeed present here.

Poposaur footprints have not bee found yet. Farlow et al. (2014) reported, “With a digit III length of about 16 cm, Poposaurus gracilis may have been comparable to a small to midrange theropod in overall body size (somewhere between the makers of Anchisauripus sillimani and A. minusculus, in the terminology of Lull [1953]). The dinosaur-like pedal proportions of Poposaurus, and the similarity of its reconstructed footprint to those of some dinosauromorphs, suggest that some grallatorid forms could well have been made by Poposaurus and its close relatives. However, mistaking Poposaurus tracks for dinosaur (particularly theropod) tracks would be less likely to occur if digit I of Poposaurus routinely touched the ground. Furthermore, trackways made by Poposaurus would probably have a shorter stride/footprint length ratio than grallatorid trackways.”

Personal thought
Seems to me that on Poposaurus pedal digit one is going to impress creating a four-toed ichnite.

References
Farlow JO, Schachner ER, Sarrazin JC, Klein H and Currie PJ 2014. Pedal Proportions of Poposaurus gracilis: Convergence and Divergence in the Feet of Archosaurs. The Anatomical Record. DOI 10.1002/ar.22863

Which pterosaur does this foot belong to?

Figure 1. This appears to be a classic basal pterosaur foot, but what kind? Note the presence of the ungual on digit 5. That's exciting!

Figure 1. This appears to be a classic basal pterosaur foot, but what kind? Note the presence of the ungual on digit 5. That’s exciting! So is that extra phalanx.

Here (Fig. 1) is what appears to be a classic basal pterosaur foot. Long narrow metatarsals. Metatarsals 3 and 4 are the longest, as in Preondactylus and Austriadactylus (SC332466). Pedal 5.1 extends beyond metatarsal 4, as in Austriadactylus and Dimorphodon. Digit 4 is slightly longer than digit 3. Digit 5, though, appears to have an extra phalanx or two. That astragalus is oddly shaped, but everything else seems to be very pterosaurian…

Did you guess? Or did you know?
This is Tanystropheus, a close relative to the ancestors of pterosaurs. Langobardisaurus and Cosesaurus are closer to that common ancestor and to each other.  And they both have this kind of foot.

Homoplasy, not Convergence
Those similar foot characters are homoplastic, not the result of convergence and attests to the antiquity of this foot morphology in the lineage of pterosaurs. Now, if we can only get the powers that be to start including Tanystropheus, Langobardisaurus, Cosesaurus (and the rest of the Fenestrasauria) with pterosaur and archosaur studies, it would be no surprise to find out where pterosaurs actually do nest in the scheme of things.

Archosaurs, as you already know, have only a vestige or less of a fifth pedal digit. This is where you start looking for the ancestors of pterosaurs.

And if you’re an archosaur-lover ~ take your blinders off.

Pterodactylus grandipelvis – what is it?

Pterodactylus grandipelvis is known from two “grand pelves.” And they’ve been known for about 150 years. TM6927 is the holotype (von Meyer 1859/1860). BSP 1883 XVI is the referred specimen. Oddly, both are preserved exactly alike, as a sacrum, two ilia and prepubes. An ischium impression may be ephemerally present on the holotype.

Pterodactylus grandipelvis is a nomen dubium according to S. C. Bennett 2013.

Pterodactylus grandipelvis holotype.

Figure 1. Pterodactylus grandipelvis holotype.

Pterodactylus grandipelvis would have been one of the largest pterosaurs of the Late Jurassic Solnhofen Limestone. I looked around at reptileevolution.com and could find no better match for it than Cycnorhamphus (Fig 3). Notably the “Pterodactylus” grandipelvis was at least twice the size.

Pterodactylus grandipelvis referred specimen BSP 1883 XVI

Figure 2. Pterodactylus grandipelvis referred specimen BSP 1883 XVI

We know of larger cycnorhamphids, like Moganopterus from China. Giant animals are relatively less numerous in most ecosystems. Too bad we haven’t found more of this pterosaur in the last 150 years.

Figure 3. Cycnorhamphus to scale with enlarged pelvis (at left) and two pelves attributed to P. grandipelvis to scale.

Figure 3. Cycnorhamphus to scale with its enlarged pelvis (at left) and two pelves attributed to P. grandipelvis to scale. Note that P. grandipelvis is twice the size.

Any additional data on any of these taxa would be gratefully appreciated.

References
Bennett SC 2013. New information on body size and cranial display structures of Pterodactylus antiquus, with a revision of the genus.Palaeontologische Zeitschrift.
Meyer H 1859. Zur Fauna der Vorwelt. Vierte Abt : Reptilien aus dem lithographischen Schiefer des Jura in Deutschland und Frankreich, v. 1, p. 1-84.
Meyer H 1860. Zur Fauna der Vorwelt. Vierte Abt: Reptilien aus dem lithographischen Schiefer des Jura in Deutschland und Frankreich, v. 2, p. 85-144.

Breathing in a box – Respiration in pterosaurs (Geist et al. 2013)

A new paper on pterosaur breathing has arrived.
Unfortunately, Geist et al. (2013) follow Claessens et al. (2009) in hoping that the prepubis was mobile in order to drive a thoracic lung pump. It’s not. (BTW, we looked at Claessens et al earlier here).

Geist et al. report, “we note that many of the large pterodactyloid taxa had relatively rigid trunks due to a high degree of fusion of the thoracic skeleton, a condition we describe as a synthorax… but also appear to have severely constrained ribcage movement for respiration.”

How is this shown?
Geist et al. report, “Although their morphology is variable, they [pterosaurs] always have a narrow, rod-like caudoproximal peduncle, but widen and flatten cranially. Their general appearance and orientation is often strikingly similar to that of the pubic bones of extant crocodilians.”

This is an error.
Prepubes are oriented ventrally with a non-moving butt joint, and only sometime slightly cranially. Thus they are not similar to extant crocodilians, which rotate their pubes uniquely.

Campylognathoides (CM 11424), the earliest pterosaur with a reduced pedal digit 5.

Figure 1. Campylognathoides (CM 11424). Note the prepubis, perpendicular to the spinal column and butt-joined to the pubis is immobile. Think of it like the booted pubis in T-rex, which was not used in reparation. Note the way Geist et al orient the prepubis is figure 2.

After just reporting that some pterosaurs fuse their prepubes medially, Geist et al. report, “The hinge-like [medial] articulation with the pubic bones indicates that the prepubic bones were highly mobile in the vertical plane, but were restricted in transverse movements.”

This is also bad reporting, based on bad drawings in the literature, (like Claessen 2009), not based on manipulating 3D prepubes on pubes, as I have done over several dozen taxa.

The prepubes act as immobile pubic extensions. And in that capacity they anchor adduction muscles to the femur, like the long booted pubis of T-rex. They have nothing to do with respiration. Nor were they co-oped for respiration from their original function.

Sure prepubes had large muscle scars. They were attached to large leg muscles!

The most mobile parts of the pterosaur thorax were the posterior dorsal ribs. They were slender and single-headed to retain their mobility. Lizards breathe with their ribs. Here’s a short video and another video for anyone who can’t picture when a lizard holds still, their rib cage keeps pumping. Holding still, btw, is the same as having a fused backbone, in terms of methodology.

Geist et al report, “Claessens et al. (2009) presented a detailed model for an avian-like mechanism of sternal excursion as the primary lung ventilation mechanism for both small and large pterosaurs—the “skeletal breathing pump” model.” In essence the sternal complex rotated on the coracoid joint with some movement from the scapulocoracoid. This pulled the ribs  and gastralia forward increasing thorax volume.”

Geist et al were critical of Claessens noting, “In pterosaurs the orientation of the rib articulations on the thoracic vertebrae are very unlike those of birds (Fig. 3), and likely would not have permitted the degree of fore-aft movement of the caudal ribs as proposed by Claessens et al. (2009).”

Geist et al continue, “Three dimensionally preserved specimens indicate that pterosaur ribs project more or less perpendicular to the long axis of the body (e.g., see Fig. 4A–E). A caudal inclination of these ribs similar to the orientation of those in extant birds cannot be confirmed here.”

That would be odd. Pterosaurs are now flying pancakes? No. Perhaps that’s just an odd choice of words because their illustrations don’t follow that morphology. Sharovipteryx was the flying pancake!

Geist et al. report, “the morphology of the synthorax of large pterosaurs is permissive of extracostal mechanisms that resembled the visceral pumps [diaphragms] found in mammals and crocodilians.” After considering turtle, mammal, bird and croc respiration, they never once mentioned lizards. Unfortunate.

Figure 1. Click to animate. Pterosaur breathing using a liver pump as envisioned by Geist et al. 2013.

Figure 2. Click to animate. Pterosaur breathing using a liver pump as envisioned by Geist et al. 2013. Unfortunately, the prepubis was immobilized due to a butt joint at the pubis, so this isn’t accurate.

Ultimately, Geist et al. report, “Accordingly, we propose a model for large pterosaurs in which a more or less crocodilian-like visceral displacement pump drove the inhalation phase of the respiratory cycle, and contraction of flank muscles acting on the gastralia and prepubic bones restored the viscera to their initial positions to drive exhalation (Fig. 9). In our model, sheets of diaphragmaticus-like skeletal muscle originated on the pubis, prepubic bones, and/or caudal-most gastralia and inserted on a transverse septum or the fascia of the liver.”

The Triebold Pteranodon, one of the most complete ever found. The metacarpals are quite a bit longer here. So is the beak.

Figure 3. The Triebold Pteranodon. Note the orientation of the prepubes, ventrally, in line with the standing femora. The Geist orientation is based on Claessens et al. (2009) which was based on a mistake.

Of course, as they admit, there is no evidence for this. And I’ll add some serious evidence against it.

Some pterosaur pubes are much shorter than their ischia. What would this mean for a cranially directed prepubis? Take a look at Figure 1 and put it together for yourself. Unfortunately, Geist et al. looked at only those pelves that had a long pubis.

If pterosaurs had a avian-like or monitor-like air-sac system associated with their lungs, then the posterior ribs could have pumped air in and out of those sacs, driving air through the lungs. Very typical of lizards, not crocs or birds.

To their credit, Geist et al. touch on the fact that sternal ribs are rarely ossified, noting they were likely often cartilage-based.

References
Claessens LPAM, O’Connor PM, Unwin DM 2009. Respiratory Evolution Facilitated the Origin of Pterosaur Flight and Aerial Gigantism. PLoS ONE 4(2): e4497. doi:10.1371/journal.pone.000449
Geist NR, Hillenius WJ, Frey E, Jones TD and Elgin RA 2013. Breathing in a box: Constraints on lung ventilation in giant pterosaurs. The Anatomical Record. 013 Dec 10.

Looking at Rhamphorhynchus megadactylus

One of the larger, but not the largest, Rhamphorhynchus specimens is R. megadactylus (n52). It’s a classic roadkill fossil. Nearly all the parts are there, only difficult to segregate.

Figure 1. Rhamphorhynchus megadactylus in situ. Can you find the pelvis and prepubis here? How about both coracoids?

Figure 1. Rhamphorhynchus megadactylus in situ. Can you find the pelvis and prepubis here? How about both coracoids? The right femur is portrayed here in ghosted blue.

Some of the bones (skull, backbone, hind limb) are easy to identify. DGS (digital graphic segregation) helps a little in identifying the more difficult parts. As a reminder, a reconstruction and phylogenetic analysis are paramount to make sure you have identified all the parts correctly by fitting them together and that sister taxa share most traits.

Colorized bones in Rhamphorhynchus megadactylus.

Figure 2. Colorized bones in Rhamphorhynchus megadactylus.

Prior literature indicates that large specimens should have a fused scapulocoracoid. Here one remains fused after the taxonomic mixing, but the other does not.

Figure 3. Closeup of Rhamprhorhynchus megadactylus. Note the fused scapulocoracoid and the unfused one. Not sure yet what the bone below the upper humerus is. Perhaps the ventral portion of the humerus broken and shifted.

Figure 3. Closeup of Rhamprhorhynchus megadactylus. Note the fused scapulocoracoid and the unfused one. Not sure yet what the bone below the upper humerus is. Perhaps the ventral portion of the humerus broken and shifted.

Some other details are tiny and tricky. If you can, see if you can see the bones of manual digit 5 here (Fig. 4, one metacarpal and three phalanges, including the ungual).

Figure 4. Manual digit 5 is somewhere in this picture. Can you find it?

Figure 4. Manual digit 5 is somewhere in this picture. Can you find it?

Similarly, can you see the ungual (p5.3) at the tip of pedal digit 5 here (Fig. 5)?

Figure 5. Can you see the ungual of pedal digit 5 here in Rhamphorhynchus megadactylus, n52?

Figure 5. Can you see the ungual of pedal digit 5 here in Rhamphorhynchus megadactylus, n52? That’s metatarsal #4 sitting on top of digit 5.

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

Evolution at the base of Dorygnathus

The large pterosaur tree offers new insights into pterosaur evolution. Today we’ll look at the base of Dorygnathus (Middle Jurassic, Fig. 1), once thought an evolutionary oddity, but today is the key taxon at the base of all Cretaceous pterosaurs.

Figure 1. Evolution at the base of Dorygnathus. Top: the BSP 1994 specimen assigned (erroneously) to Eudimorphodon. Top middle: Sordes. Bottom middle: Dorygnathus. Bottom: Jianchangnathus, a basal dorygnathid at the base of Wukongopteridae and Scaphognathia.

Figure 1. Evolution at the base of Dorygnathus to scale. Top: the BSP 1994 specimen assigned (erroneously) to Eudimorphodon. Top middle: Sordes. Bottom middle: Dorygnathus. Bottom: Jianchangnathus, a basal dorygnathid at the base of Wukongopteridae and Scaphognathia.

Sometimes a picture is worth a 1000 words. Here Sordes is derived from a sister to the BSP specimen, itself derived from the holotype Eudimorphodon, Dorygnathus is derived from a sister to Sordes. Jianchangnathus is derived from a sister to the basalmost Dorygnathus.

Other than the jianchangnathids, dorygnathus ultimately gave rise to ctenochasmatids and azhdarchids.

Jianchangnathids ultimately gave rise to wukongopteripterids and a more successful lineage, the scaphognathids, which ultimately gave rise to most other Cretaceous pterosaurs.

So, the generalized “plain brown sparrow” look of Sordes belies its genetic potential to create giant pterosaurs, crested pterosaurs and even flightless pterosaurs. And the large variation demonstrated by these four “sister” taxa indicates that there are many more taxa waiting to be discovered that will be transitional forms nesting between them.

The Edinburgh Rhamphorhynchus: biting its own tail!

The Edinburgh Rhamphorhynchus (Figs 1, 2, museum number unknown) is fairly complete, but my goodness, what a roadkill! Is it right side up? Or upside down? With the tail and head on the same side, and actually biting it’s own tail, this specimen offers nothing but confusion at first glance.

Figure 1. The Edinburgh specimen of Rhamphorhynchus, as if a Jurassic truck had just run over it.

Figure 1. Click to enlarge. The Edinburgh specimen of Rhamphorhynchus, as if a Jurassic truck had just run over it. This one is biting its own tail!

It’s rare to find wing membranes and a tail vane, but both are present here. Things are a little easier to see when the parts are colorized (Fig. 2).

Figure 2. Edinburgh Rhamphorhynchus parts colorized. In the right wing membrane note how the trailing edge of the wing membrane curves back to the knee (proximal tibia).

Figure 2. Click to enlarge. Edinburgh Rhamphorhynchus parts colorized. In the right wing membrane note how the trailing edge of the wing membrane curves back to the knee (proximal tibia).

Someday I’ll do a reconstruction when I find higher resolution. There’s likely more to this specimen that just cannot be seen without better data (higher resolution). Even so, note that the wing membrane appears to curve back toward the knee. Unfortunately this specimen will not solve any arguments with regard to deep chord (to the ankle) vs. narrow chord (to the elbow) wing membranes.

The specimen is not listed in the Wellnhofer (1975) catalog that lists 108 other Rhamphorhynchus specimens. Thus, I’ll guess that it is a newer specimen. It appears to be a R. muensteri species. Scale is unknown, but likely was mid-sized if so.

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

Tracing fossil photos goes mainstream in 2014

DGS is going mainstream
A new paper by Chiappe et al. 2014, forsakes time honored and inaccurate pencil tracings with a camera lucida (basically a prism) and goes straight to the camera, scanner and mouse in their portrayal of the new Hongshanornis specimen. This is a great example of DGS or digital graphic segregation.

Figure 1. From Chiappe et al. 2014 showing the fossil (at right) and the digital tracing (at left).

Figure 1. From Chiappe et al. 2014 showing the fossil (at right) and the digital tracing (at left). Here’s a professional paleontologist using a technique for which I was once and continue to be derided.

There is value in this technique, even when the bones are mere impressions, and the soft tissue is ephemeral, as they appear here. (Figs. 1, 2). The technique is especially helpful in two-dimensional crushed fossils, like Hongshanornis.

Figure 2. The two images of Hongshanornis superimposed to show the exactness this tracing technique produces, plus color, plus enlargements, etc. etc.

Figure 2. The two images of Hongshanornis superimposed to show the exactness this tracing technique produces, plus color, plus enlargements, etc. etc.

Many were the times
when I tried to match a published drawing with a published photo and found I had to warp or distort one or the other to make them match. A long lens from a distance at right angles to the plane of the specimen minimizes distortion and key-stoning (perspective problems). This photography technique combined with scanning such a photo and tracing it on screen with a mouse makes that problem go away.

The next step, of course, is to use the digital tracings to create a very accurate reconstruction.

References
Chiappe L, Bo Z, O’Connor J, Chunling G, Xuri W, Habib M, Marguan-Lobon J, Qingjin M and  Xiaodong C 2014. A new specimen of the Early Cretaceous birdHongshanornis longicresta: insights into the aerodynamics and diet of a basal ornithuromorphPeerJ. 2:e234; DOI 10.7717/peerj.234

wiki/Hongshanornis