The Completeness of the New Reptile and Pterosaur Family Trees

The news that the Chinese pterosaur, Guidraco, was most closely related to the South American Ludodactylus points to the worldwide distribution of the Ornithocheiridae, a clade of long-ranging pterosaurs. Probably not such a surprise for such wide-ranging albatross-like flyers. We also have North and South American anurognathids, Chinese Rhamphorhynchus, African dsungaripterids and South American ctenochasmatids, to name a few. We’re not coming up with anything outlandish anymore.

A Complete Pterosaur Tree
The Guidraco news points to the virtual completeness of the pterosaur family tree. Despite its unusual and exaggerated traits, Guidraco nested well within established clades. No presently known pterosaur is an outlier taxon. All are nested. I haven’t found an oddball in the bunch. Other than the terminal taxa (those that left no descendants), all pterosaurs fit somewhere between two others.

And Complete Reptile Tree
The same is true of dinosaurs and reptiles in general. Every taxon finds a sister. All enigmas are nested. The family trees are complete or virtually so.

Reason to Celebrate? Depends on Your Attitude.
One of the drivers of science is the search for answers and the revelation of mysteries. So what happens when virtually all of those mysteries are already solved? Does that take all the fun out? Have we already seen the Golden Age of enthusiasm and insight? Like a jigsaw puzzle that is almost done and missing just a few pieces, the present family trees indicate that future discoveries are likely to be more or less predictable ~ with new discoveries nesting between something we already are familiar with.

Works With Less Than Complete Specimens too.
The present trees are filled with skull only and skull-less taxa, as well as a few others of lesser quality. Even so, the data provides enough resolution to resolve long-standing mysteries and upset traditional paradigms (enabled by lack of testing better candidates).

The New Trees Work Like Clockwork, But That Doesn’t Take All the Fun Out.  Predictability is generally agreed to be a good trait in science, as in the Periodic Table of Elements. The new large tree provides that sort of predictability and complete resolution. The only frustration now is general adoption (hopefully by testing!!).

While others struggle with their own (let’s face it: botched) pterosaur and reptile trees, fraught with resolution problems and sisters that don’t look similar, I encourage workers to add more and more taxa to replicate the full resolution recovered in the trees presented in reptileevolution.com, because…

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.

Patterns in the Reduction of Pedal Digit 5 in Pterosaurs

Updated April 5, 2016 with a new image of Nemicolopterus.

That Very Weird Pedal Digit 5
Basal pterosaurs had an elongate pedal digit 5, emanating from a short metatarsal 5 and composed of two hyperflexed metatarsal-length phalanges tipped by an often overlooked ungual for a total of three phalanges.  Peters (2000) reported that pedal digit 5 impressed the hyperflexed dorsal surface of pedal 5.2/3 (= fused phalanges) into the matrix, as demonstrated by Rotodactylus tracks. Peters (2000) attributed matched Rotodactylus to a pterosaur outgroup sister, Cosesaurus. Peters (2011) attributed similar tracks with pedal digit 5 impressing far behind the other four digitigrade impressions to anurognathids and a specific Rhamphorhynchus.

Figure 1. Click to enlarge. Basal tritosaur, fenestrasaur and pterosaur feet with digit 5 bones color coded. Note the fusion of pedal 5.2 and 5.3 in pterosaurs. Find any single archosaur or set of archosaurs with a similar pedal digit 5 and you’ll have found the archosaur sister to pterosaurs. Good luck! Question for you: does the brevity of p5.3 in Cosesaurus and Longisquama mean it ultimately disappeared? Or did it fuse with p5.2? I think the latter, but the data is not quite there yet. 

Where Did It Come From?
Pterosaurs inherited that elongated toe 5 from their fenestrasaur and tritosaur ancestors, all of which (e.g. Tanystropheus) had an extra phalanx (Fig. 1). Pedal 5.2 fused to p5.3 in the most primitive known pterosaurs, so the ungual is p5.4, as in the basal lizards, Lacertulus and Huehuecuetzpalli (Fig. 1). In basal pterosaurs and Sharovipteryx, pedal 5.1 often extended to or beyond the distal end of metatarsal 4, but it does not do so in more primitive taxa. In several derived clades pedal digit 5 became reduced, sometimes to a vestige. We’ll look at those patterns of reduction today.

Huehuecuetzpalli
Distinct from Lacertulus, metatarsal 5 was shorter and pedal digit 5 was longer in Huehuecuetzpalli (Fig. 1). This set up the classic pattern seen in the most members of the Tritosauria (langobardisaurs, drepanosaurs, tanystropheids and fenestrasaurs). Exceptions and reductions follow.

Note: absolutely no archosaurs or archosauriformes have an elongated pedal digit 5. This trait alone should have been enough to steer workers away from the conventional and traditional “pterosaurs are archosaurs” hypothesis.

Figure 2. Macrocnemus. Note the reduction of pedal digit 5. The resemblance of this skull to that of Campylognathoides (Fig. 3) is both somewhat homologous and by convergence. Several transitional taxa differ more. 

Macrocnemus
The first instance of pedal digit 5 reduction occurred in Macrocnemus. The entire digit was shorter than metatarsal 4 and the phalanges of digit 5 were shorter distally.  A derived macrocnemid, Dinocephalosaurus, likewise had a small pedal digit 5, but it extended as far at the base of p4.2 as this reptile developed paddle-like, swimming feet. Find the missing Macrocnemus without this toe reduction and you’ll have the transitional taxon linking this genus closer to tanystropheids, langobardisaurs, drepanosaurs and fenestrasaurs.

Figure 3. Campylognathoides, the earliest pterosaur genus with a reduced pedal digit 5. All known specimens had a reduced pedal digit 5. 

Campylognathoides 
The first pterosaur with a stunted pedal digit 5 was Campylognathoides (Fig. 3). All known specimens had a stunted pedal digit 5 in which pedal 5.1 extended no further than half the length of metatarsal 4. Not sure why this is so. The current predecessor taxon, Eudimorphodon cromptonellus, did not have a reduced pedal digit 5, but overall E. cromptonellus was much smaller. Perhaps pedal digit 5 is the one body part that did not enlarge, phylogenetically, as the rest of the body grew larger.

A taxon derived from a sister to the most derived Campylognathoides, CM 11424, Rhamphorhynchus intermedius (St/Ei 8209, No. 28 in the Wellnhofer 1975 catalog), had a longer pedal digit 5 that extended at least 3/4 of the length of metatarsal 4. So the reduction was reversed to become an elongation in Rhamphorhynchus. Pedal digit 5 varied in length in other Rhamphorhynchus specimens, with some extending no further than half the length of metatarsal 4 and others extending to the full length of metatarsal 4.

Figure 4. Two sister taxa bridging the basal/derived pterosaur divide. TM 10341 was much smaller than the SMNS 50164 specimen of Dorygnathus (enlarged to the right). Despite the short metacarpal and long pedal digit 5, the tiny dorygnathid was considered a Pterodactylus by Wellnhofer, who listed it as No. 1 in his 1970 catalog. Pedal digit 5 no smaller relative to metatarsal 4 in the tiny sister. 

Tiny Dorygnathids Leading Toward Azhdarchids
Typical Dorygnathus specimens, like SMNS 50164, had a very large pedal digit 5, with p5.2 bent, even so, in this taxon pedal 5.1 did not extend beyond metatarsal 4, but aligned with the line extending along mt3 and mt4. Despite the large size reduction in TM 10341 (No. 1 in the Wellnhofer 1970 catalog), pedal 5.1 extended just as far. In the larger taxon, Beipiaopterus, pedal 5.1 did not extend beyond half of metatarsal 4. It was similar in No. 44 and No. 42. Pedal 5.1 did not become smaller than half of metatarsal 4 until the base of the Azhdarchidae, represented by Jidapterus. Peters (2000a, 2011) found a correlation between the reduction of pedal digit 5 and plantigrady in these taxa.

Figure 5. The MB.R. 3530.1 specimen wrongly attributed to Pterodactylus (No. 40 in the Wellnhofer 1970 catalog).

Tiny Dorygnathids Leading Toward Ctenochasmatids
Similar in fashion to the above scenario, MB.R.3530.1 (No. 40 in the Wellnhofer 1970 catalog, Fig. 5) was smaller overall and had a shorter pedal digit 5 and it became progressively shorter in more derived ctenochasmatids like Ctenochasma. In these taxa pedal digit 5 is not typically found hyperflexed, but extends its full (even though abbreviated) length alongside metatarsal 4.

No Reduction in Cycnorhamphids + Ornithocheirds
Relative to metatarsal 4, pedal digit 5 does not become reduced in the monophyletic clade of cycnorhamphids + ornithocheirids. However, because metatarsal 4 becomes so short in derived ornithocheirids like Anhanguera, pedal digit 5 likewise becomes small — but not relatively small.

Figure 6. Pedal digit 5 in a basal Pterodactylus, AMNH 1945.

Pterodactylus
In all specimens for Pterodactylus pedal 5.1 extends no further than half of metatarsal 4 (Fig. 6).

Figure 7. The smallest of all adult pterosaurs, B St 1967 I 276 or No. 6 in the Wellnhofer (1970) catalog. At left is the foot plantigrade and with metatarsals slightly raised, which simplifies and aligns the PILs (parallel interphalangeal lines). The gray oval is a hypothetical egg based on the pelvic opening. The sternal complex is also shown separated from the lateral view reconstruction.

No. 6
The smallest of all known adult pterosaurs, B St 1967 I 276 (No. 6 in the Wellnhofer 1970 catalog, Fig. 7) extended pedal 5.1 no longer than 2/3 the length of metatarsal 4 but in larger taxa, like No. 12 and No. 23, pedal 5.1 extends to a point in line with metatarsals 3 and 4, still shorter than metatarsal 4. This pattern is also found in several other Germanodactylus specimens.

Figure 8. A larger view of Nemicolopterus. Pedal digit 5 is relatively reduced here.

Nemicolopterus to Tupuxuara
The tiny pterosaur Nemicolopterus (IVPP-V-14377, Fig. 8) had a pedal 5.1 no longer than half the length of metatarsal 4. The larger sister, Shenzhoupterus, had a longer metatarsus and a shorter pedal digit 5. This pattern continues in Huaxiapterus with a reduction to a nub in Tupuxuara.

Figure 9. Right pes, dorsal view of Pteranodon UALVP 24238. Note pedal digit 5 is a vestige on this plantigrade foot.

No. 13 to Pteranodon
Despite the large number of Nyctosaurus and Pteranodon specimens, few preserve toe bones (Fig. 9).  Fewer still preserve digit 5 toe bones. No digit 5 toe bones are known in Nyctosaurus. A basal Pteranodon FHSM VP 2183 preserves pedal 5.1 extending no further than 1/3 the length of metatarsal 4, which is rather elongate. In derived Pteranodon specimens pedal digit 5 becomes much shorter, but the foot remains digitigrade. In another clade with a vestige pedal digit 5, the foot becomes plantigrade, according to PILs analysis.

Problems
Pedal digit 5 is sometimes hard to find. Often it is found beneath the metatarsus.  Other times it may become disarticulated and ignored or unsought by preparators, who “know” that all “pterodactyloids” lose pedal digit 5 or have vestiges at best. As you can see above and in more detail at ReptileEvolution.com, the pattern of reduction and enlargement of pedal digit 5 in pterosaurs is a little more complicated than the conventional thinking suggests.

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
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
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
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.
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/Pterodactylus
wiki/Rhamphorhynchus

Pterosaur Cervicals: 8 or 9?

Bennett (2004) reported, “The cervical series of the specimen (the third known Scaphognathus, SMNS 59395) consists of 9 vertebrae if the first vertebrae that bears a large rib that articulates with the sternum is interpreted as the first dorsal vertebra.”  This was a break with tradition, in which pterosaurs were considered to have 8 cervicals.

Figure 1. Scaphognathus SMNHS 59395 with cervicals colored green and orange, dorsal colored purple and blue, sternum in red. Click for more info.

Vertebra number 9 always lies completely within the torso, despite not articulating with the sternum. Hence the traditional number of 8 makes more morphological sense. Vertebra number 9 also shares more traits in common with number 10 than number 8.

Bennett (2004) reported that “Pterodactylus had 7 cervicals and large [unspecified] pterodactyloids had 9 cervicals, the latter resulting from the cervicalization of the anterior two dorsal vertebrae.” Unfortunately, I can find no examples of either. Large or small, all pterosaur specimens in reptileevolution.com have 8 cervicals.

Figure 2. The skull of the SMNS 59395 specimen of Scaphognathus with bones color coded. Note there were 4 premaxillary teeth, as in most other pterosaurs and all sister taxa, not 2 as Bennett (2004) reported.

On a side note, Bennett (2004) reported there were only two teeth in the premaxilla of SMNS 59395. I found four (Fig. 2) as in most other pterosaurs and all known sisters. I saw the specimen before it was prepared. But I was able to “see” four teeth in photos. Here Bennett (2004) might have made a different determination if he had realized that two teeth would have been autapomorphic, but no phylogenetic analysis was performed.

Figure 4. Prepared and unprepared images of the SMNS 59395 specimen of Scaphognathus. Click to enlarge.

There’s a nice articulated wing ungual present in this undisturbed completely articulated specimen.

Finally, Bennett (2004) considered SMNS 59395 a “juvenile with unfused girdles, carpals, and tarsals.” No phylogenetic analysis was offered. Here, after phylogenetic analysis, the smaller SMNS specimen was found to be distinct in several traits from the larger No. 109 specimen, and derived taxa were smaller still. So SMNS 59395 was likely a precocious small adult, not a juvenile. A juvenile should have been virtually identical to the adult, only smaller, because that’s the pattern we see in embryos, the only pterosaurs for which we have an exact ontogenetic age – zero.

This data was gleaned from photos. Bennett (2004) had the specimen in hand. Some of these conclusions, like whether vert #9 was a cervical or a dorsal goes back to the choices we make as paleontologists. Phylogenetic analysis helps.

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 2004. New information on the pterosaur Scaphognathus crassirostris and the pterosaurian cervical series. Journal of Vertebrate Paleontology, 24(Suppl. to #3):38A.

Dr. Ellenberger and his Petite Cosesaurus – part 2: post-cranial

Yesterday we looked at Dr. Paul Ellenberger’s long-time interest in the tiny Mid-Triassic reptile, Cosesaurus aviceps, with a focus on the skull. He thought of his little Cosesaurus as an important transitional taxon, a bird precursor living several tens of millions of years earlier than Archaeopteryx.

Figure 1. Cosesaurus insitu, image rotated 180 degrees from the image presented yesterday to give the illusion of the specimen elevated above the matrix (the brain assumes the light comes from above). The original is actually depressed beneath the matrix surface, as shown earlier.

New observations and phylogenetic analysis nest Cosesaurus within the Tritosauria at the base of the Fenestrasauria (Peters 2000b) leading toward the Pterosauria. Derived from a sister to the basal lizard, Huehuecuetzpalli, Cosesaurus is the Archaeopteryx of the Pterosauria. Cosesaurus could run on two legs (Peters 2000a, Fig. 12, based on a perfect match to Rotodactylus tracks) and flap its fiber-trailed forelimbs (Peters 2009), but it could not fly. That would come several million years later.

Post-Crania
Having covered several cranial traits earlier, today we’ll look at the post-cranial traits observed by Ellenberger (1978, 1993, Fig. 1), many reinterpreted by Peters (2000, 2009, Fig. 12) both correctly and incorrectly and here corrected again.

Figure 1. From Ellenberger 1993. Overall view of Cosesaurus aviceps in standing, bird-like pose, with hind limbs oriented too parasagittal for the shape of the proximal femur. See Figure 12 (below) for a new interpretation.

The Cervicals, Dorsals and Sacrals
Ellenberger (1993) correctly interpreted the eight cervicals as individually longer than the dorsals and provided with elongated ribs (Fig. 1). The dorsals were procoelous and relatively short as a set. More than two sacrals were present. Unfortunately Ellenberger interpreted the largest sacral transverse process as an ischium (Fig. 7). There are no similarly-shaped ischia in candidate sisters. The actual sacral transverse processes were identified by Peters (2000, Fig. 9).

Figure 2. The tail of Cosesaurus as interpreted by Ellenberger (1993). One uropatagium is in blue. The jellyfish is in orange.

The Tail
The tail was attenuated after the first ten caudals, which were provided with elongated transverse processes (Fig. 2). Thus the caudofemoral muscles were still important femoral abductors. The distal centra were three times longer than their depth. The chevrons did not descend as in most reptiles, but remained parallel to the centra, as in Archaeopteryx (and ignored by Ellenberger, as in Sharovipteryx and pterosaurs). Ellenberger (1993) noted a valid break in the tail of Cosesaurus, in which the tail was rotated 90 degrees on either side of the break, but that break is not reflected in the extended soft imprint.

The Tail – Soft Tissues
The tail of the Cosesaurus fossil was surrounded by a broad matrix area that sloped gently downward  (Fig. 2). The area beyond the attenuated caudals was subdivided by a series of regularly spaced lines. Under his bird bias, Ellenberger (1993) considered such data an indication of elongated tail feathers (rectrices) with feather shafts. That would have preceded the development of theropod feathers by several tens of millions of years. Unfortunately, no Cosesaurus sister taxa have any sort of similar structure. If just the narrow, hair-like shafts are valid then the tail of Cosesaurus had keratinous hairs along its length. In certain pterosaurs these hairs at the tail tip coalesced to form a tail vane. This, of course, is an attempt to explain away the broader shape surrounding the tail. This could be the effect of water and granular matrix interacting with the tail hairs. Or this broad shape could be a valid structure because it appears to be continuous with the uropatagium coming off the left femur (Figs. 2, 11). Hard to figure.

Figure 3. The pectoral region of Cosesaurus as interpreted by Ellenberger (1993). Light blue = coracoids. Yellow = unossified sternum and ossified ventral keel rim. Purple = clavicles. Green = scapulae.

The Pectoral Girdle
Ellenberger (1993) identified the strap-like scapulae more or less correctly (Fig. 3), but not quite long enough (Fig. 5). Birds and pterosaurs both have a strap-like scapula. Ellenberger considered the broad oval ventral plate a pair of giant coracoids fused medially (Fig. 3). Peters (2000) mistakenly followed this interpretation, but recently reinterpreted the plate as an anteriorly migrated sternum (Fig. 5). The prominent quadrant-shaped stem Ellenberger identified as a sternal keel (Fig. 3) turned out to be a very pterosaur-like coracoid stem (Fig. 5). The problem was: there are no other known taxa that have a pectoral girdle close to the Ellenberger (1993) restoration/reconstruction. However, there are three other taxa with the current Peters restoration/reconstruction: Sharovipteryx, Longsiquama and pterosaurs. Cosesaurus demonstrated the genesis of the sternal complex and the stem-like coracoid.

Figure 4. The pectoral girdle of Cosesaurus as restored by Ellenberger (1993). Light blue = coracoids. Yellow = unossified sternum with ossified keel. Purple = clavicles. Green = scapulae.

The Sternum
Ellenberger (1993) considered the sternum of Cosesaurus to be unossified (Figs. 3, 4), supporting that otherwise disconnected and ossified ventral keel. That was an invention created due to fulfill his bird-bias. What Ellenberger (1993) considered a giant ventral coracoid, is now identified as a sternum (Fig. 5) having migrated forward to a position it occupies in Longisquama and pterosaurs, up against the clavicle and the transverse processes of the interclavicle creating a sternal complex.

Figure 5. New interpretation of the pectoral elements of Cosesaurus. Light blue = coracoids. Yellow = unossified sternum. Purple = clavicles. Pink = clavicles. Green = scapulae. Red = interclavicle.

The Clavicles
Ellenberger (1993, Fig. 3) correctly traced the clavicles of Cosesaurus as transversely oriented and straight overlapping medially and rimming the anterior interclavicle and coincident sternum. Then he restored the clavicles (Fig. 4) as disconnected from the other elements and V-shaped like a deep wishbone-shaped furcula (fused clavicles) following the restored V-shaped of his coracoids. Jurassic birds, like Archaeopteryx, did not attain such a shape in the clavicle. In Cosesaurus, Longisquama and pterosaurs the clavicles indeed rim the anterior interclavicle/sternum complex as shown in situ (Fig. 5) and reconstructed (Fig. 12). They are coplanar with the sternum.

Scapulae
Ellenberger (1993) correctly identified the scapulae. Peters (2000a) did not. While attempting to follow the example of a sister, Macrocnemus, I considered the scapulae to be disarticulated ribs and other elements to be the disc-like scapulae. Sanz and Lopez-Martinez (1984) made the same mistake. The day I could finally “see” my error was a good day for enlightenment. I could almost hear the Moody Blues.

The Humerus
Ellenberger (1993) illustrated the humerus (Figs. 3, 4) as essentially straight, and it was, with a slightly expanded proximal and distal end.

Figure 6. The forelimb of Cosesaurus, a pigeon, Archaeopteryx and a Tern from Ellenberger (1993). Ellenberger flippled the hand in order to more closely match the digit lengths in birds. No such flipping is necessary in comparisons to pterosaurs. The two "cartilage" ovals identified by Ellenberger (1993) are homologs to the pteroid and pre-axial carpal in pterosaurs (Peters 2009). The general lack of carpal ossification is a trait shared with sister taxa.

The Radius and Ulna
The radius and ulna in Cosesaurus were straight, parallel and closely appressed to each other (Fig. 1), unlike birds, just like pterosaurs (Fig. 6). The forearm was becoming increasingly restricted in pronation and supination due to the straighter shapes of the radius and ulna. Ellenberger (1993) reported fibers emerging from the posterior ulna (Fig. 1). These are clear in his photos and I confirmed them when I visited the fossil (Peters 2009). Due to his bird bias, Ellenberger (1993) considered these to be feather precursors. Finding closer connections with pterosaurs in phylogenetic analysis (Peters 2000), Peters (2009) considered these to be aktinofibril precursors, the fibers that support the wing and uropatagium in pterosaurs and their kin.

The Hands
Ellenberger (1993) labeled the fingers correctly several times, but when restoring Cosesaurus he flipped the hands, making #2 the longest finger (Fig. 6). This created a more bird-like hand. Unflipped the hands of Cosesaurus resemble those of fenestrasaur and tritosaur sister taxa with shorter medial metacarpals and fingers, except digit 5, which is very short, on its way to becoming a vestige, as seen in Huehuecuetzpalli and the wings of Sharovipteryx, Longisquama and pterosaurs.

The Wrist
Ellenberger found two spots on the medial wrist that he ascribed to cartilage. Peters (2009) identified those as migrated centralia, now homologous with the pteroid and preaxial carpal. The other carpals were poorly ossified, as in the closest Cosesaurus sister taxa, including the basal lizard, Huehuecuetzpalli.

Figure 7. The insitu pelvis of Cosesaurus as interpreted by Ellenberger 1993. Green = Retroverted pubis with prepubic process. Yellow = ilium. Orange = Ischium.

The Pelvis
Attempting to find homologs for the retroverted pubis of birds, Ellenberger (1993) considered a displaced prepubis (Fig. 9) and a drifted gastralium to be the retroverted pubis of birds (Figs. 7-8). Never mind that the pubis of Archaeopteryx was not so retroverted or attenuated. Never mind that no other sisters had a similar pelvis. Ellenberger (1993) described elongated ilia, which is essentially correct (but perhaps over elongated). Ellenberger (1993) considered a displaced sacral transverse process to be an ischium, overlooking the actual coosified ischium + pubis (Fig. 9) and completely overlooking the pterosaur-like prepubis, probably because it was not expected in a bird ancestor. Once I recognized one prepubis in plain sight on the ilium, the other, tucked beneath the femur (Fig. 9), was easier. Unfortunately a manuscript describing these revelations and synapomorphies was rejected. Hence this website.

Figure 8. The pelvis of Cosesaurus as reconstructed by Ellenberger (1993). Green = Retroverted pubis with prepubic process. Yellow = ilium. Orange = Ischium.

Figure 9. The tiny pelvis and robust sacrum of Cosesaurus with most pelvic and sacral elements, including the prepubes, re-identified.

Figure 10. The pes of Cosesaurus according to Ellenberger (1993). Centrale in pink. Distal tarsal 4 in yellow. Ellenberger considered the pes fully webbed.

The Hind Limb
Ellenberger (1993) correctly interpreted the femur without any sort of head or neck, as in basal reptiles including lizards. Unfortunately he reconstructed the femur as a parasagittal element (Fig. 1), as in birds, rather than a sprawling one, as in the basal pterosaur, MPUM 6009.

The tibia and fibula were both straight and closely appressed to one another with the fibula less than half the diameter of the tibia, as in birds and pterosaurs. The length of the tibia/fibula becomes longer than the femur in derived theropods in the bird lineage, and in Sharovipteryx and higher taxa, in the pterosaur lineage.

The Tarsus and Pes
Ellenberger (1993) correctly interpreted the pes of Cosesaurus with an astragalus, calcaneum, centrale and distal tarsal 4 as the four largest tarsal elements. He also found tiny distal tarsals 1-3. Such a tarsus is a synapomorphy Cosesaurus shared with Tanystropheus, Sharovipteryx and pterosaurs. In addition, all these taxa had a very short metatarsal 5 and a hyper-elongated phalanx 5.1, which Ellenberger (1993) correctly identified, but did not make the pterosaur connection and no bird or bird ancestor has such a toe. One would have to go back to Proterosuchus to find a bird ancestor with digit 4 longer than 3. And certain armored aetosaurs develop a longer fourth toe. This is the trait that first drew me toward this taxon as a possible sister to pterosaurs. No gracile archosaur or archosauriform had such a toe.

Uropatagia
Ellenberger photographed and noted soft tissues emanating from the left femur and tibia (Fig. 11). He considered these to be possible feather precursors. These impressions also greatly resembled the fiber-embedded uropatagia of sister taxa, Sharovipteryx and pterosaurs. Note the fibers anterior to the knee in figure 11. Cosesaurus was much decorated in such soft tissue, and this makes phylogenetic sense as a precursor to the party queen of the Triassic, Longisquama.

Figure 11. The uropatagium following the left hind limb of Cosesaurus, photographed by Ellenberger (1993).

In Summary
Despite intense study, Ellenberger (1993) invented some insightful and strange structures in Cosesaurus due to his strong bird-bias. These have been both credited and criticized. As a suite and from head to toe, Cosesaurus shares more traits with the tritosaurs, Huehuecuetzpalli through pterosaurs. The changes in the pectoral and pelvic region distinguish Cosesaurus from Macrocnemus and nest it with similarly endowed reptiles, including Sharovipteryx, Longsiquama and pterosaurs.

Figure 12. Current interpretation of Cosesaurus.

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
Ellenberger P and de Villalta JF 1974. Sur la presence d’un ancêtre probable des oiseaux dans le Muschelkalk supérieure de Catalogne (Espagne). Note preliminaire. Acta Geologica Hispanica 9, 162-168.
Ellenberger P 1978. L’Origine des Oiseaux. Historique et méthodes nouvelles. Les problémes des Archaeornithes. La venue au jour de Cosesaurus aviceps (Muschelkalk supérieur) in Aspects Modernes des Recherches sur l’Evolution. In Bons, J. (ed.) Compt Ren. Coll. Montpellier12-16 Sept. 1977. Vol. 1. Montpellier, Mém. Trav. Ecole Prat. Hautes Etudes, De l’Institut de Montpellier 4: 89-117.
Ellenberger P 1993. Cosesaurus aviceps . Vertébré aviforme du Trias Moyen de Catalogne. Étude descriptive et comparative. Mémoire Avec le concours de l’École Pratique des Hautes Etudes. Laboratorie de Paléontologie des Vertébrés. Univ. Sci. Tech. Languedoc, Montpellier (France). Pp. 1-664.
Ostrom JH 1969. Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Peabody Museum of Natural History Bulletin 30: 1–165.
Peabody FE 1948.  Reptile and amphibian trackways from the Lower Triassic Moenkopi formation of Arizona and Utah.  University of California Publications, Bulletin of the  Department of Geological Sciences 27: 295-468.
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330.
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification Ichnos 18(2):114-141.
Sanz JL and López-Martinez N 1984. The prolacertid lepidosaurian Cosesaurus aviceps Ellenberger & Villalta, a claimed ‘protoavian’ from the Middle Triassic of Spain. Géobios 17: 747-753.

Dr. Ellenberger and his Petite Cosesaurus – part 1: Cranial Traits

Dr. Paul Ellenberger (pronounced “El-len-ber-zhay”) spent a large part of his life attempting to link a tiny Mid-Triassic fossil reptile, Cosesaurus aviceps, to birds. He considered it a precursor to Archaeopteryx in the years just following the publication of Ostrom (1969) on Deinonychus. Ellenberger published two small papers (Ellenberger and de Villalta 1974, Ellenberger 1978) and a very large (664 pp.) unpublished tome (Ellenberger 1993) on this little reptile perpetually entwined with an amorphous jellyfish. No one has spent more time studying Cosesaurus than Ellenberger. No one has put more effort into describing it and photographing it from every angle in the most precise detail.

Figure 1. Cosesaurus aviceps at close to actual size. The blob next to it is a jelly fish. No actual bones are preserved. Cosesaurus is nothing but a deep impression faithfully preserving every aspect of its skeleton down to the finest soft tissue details. The tail is especially deep, which created the impression, when transferred to 2-D, of emanating feathers. Tomorrow the same image will be presented but flipped 180 degrees.

Even so…
Ellenberger (1993) got many things wrong. He had a mistaken preconception and that biased his observations. It can happen. I’ve seen it happen to the best paleontologists out there. Following tradition is easy, but it leads to problems. Testing tradition is good science. Distrusting the validity of autapomorphies is key. Phylogenetic analysis trumps all.

The Power of Pet Ideas
Ellenberger’s (1993) bird hypotheses were never taken seriously or supported by other writers in the literature. Nevertheless, Ellenberger created a body of data leading to an interest in the taxon that launched Cosesaurus in a new direction for me. It never occurred to Ellenberger to link Cosesaurus to Sharovipteryx, Longisquama and pterosaurs. I raised the subject with him after seeing Cosesaurus in Barcelona and while staying with Paul for a day or two at his home in Montpellier, France. Ellenberger didn’t like the idea (because it didn’t support his bird hypothesis), and he didn’t want to discuss it.

Giving Credit
Well, we’re going to explore Dr. Ellenberger’s view of this little predecessor taxon. The point of this report is to give credit where credit is due and to shine a light on any mistakes.

Figure 1. From Ellenberger 1993. Overall view of Cosesaurus aviceps in standing pose, lateral and dorsal views. Note the bird-like restoration, a little too erect with hands flipped to more closely match the hands of birds. Other problems in the pectoral and pelvic regions will be discussed in part 2 of this blog tomorrow.

Ellenberger’s Reconstruction of Cosesaurus
Ellenberger saw Cosesaurus as a bird precursor, therefore he saw it as a digitigrade narrow-gauge biped. These are all true. Matching footprints (Rotodactylus) are evidence (Peters 2000). Despite being a footprint expert, Ellenberger (1993) did not consider a match of Rotodactylus to Cosesaurus. He did not produce an illustration with a bent-back pedal digit 5, which would have completed the match (Fig. 5).

Figure 2. The brain of Cosesaurus and the binocular vision reported by Ellenberger (1993). Note the elongated antorbital fenestra above the maxilla and below the prefrontal/nasal. The naris is indicated by two short lines here, better viewed in figure 3 (lower of the two skulls).

The Brain of Cosesaurus
No one but Ellenberger (1993) bothered to document the cranial capacity of Cosesaurus. Ellenberger applied reverse geometry to re-inflate the crushed skull of Cosesaurus to determine its likely dimensions in 3-D. Of course, he hoped to show that the brain of Cosesaurus had enlarged to bird-like proportions. It had also enlarged to pterosaur-like proportions. This was no ordinary reptile.

Figure 3. The skull of Cosesaurus in two lighting conditions with the antorbital fenestra and dorsal/cranial fibers/frill visible in the upper photo. From Ellenberger (1993). Also note the premaxilla crest in front of the orbit.

The Antorbital Fenestra
Ellenberger (1993) reported an antorbital fenestra in Cosesaurus and his images (Fig. 3) confirm that. I also confirm that, having seen the fossil in Barcelona.

By contrast, Sanz and Lopez-Martinez (1984) said there was no antorbital fenestra and considered Cosesaurus a juvenile Macrocnemus (Fig. 4). They also missed dozens of other traits that distinguish Cosesaurus from Macrocnemus (Fig. 5). They illustrated Cosesaurus in an inaccurate cartoonish fashion virtually identical to a cartoon Macrocnemus without any distinguishing traits other than a shortened rostrum, not realizing that in this clade hatchlings are virtually identical to adults. Altogether the Sanz and Lopez-Martinez (1984) report can be considered dated, biased and bogus because they didn’t put the effort in that was needed to trump earlier data by Ellenberger.

The same can be said of the Senter (2003) dissertation that reported no antorbital fenestra, even though he illustrated one, again in cartoonish fashion. I don’t understand how scientists can be so blinded by paradigm and bias that they cannot report the presence of an antorbital fenestra in Cosesaurus (Fig. 3). Unfortunately others (Evans 1988, Hone and Benton 2008) used the bogus data in phylogenetic analysis, preferring those simplified drawings to the precision of Elleberger (1978, 1993) and Peters (2000) or their own examinations(!)

Figure 4. Cosesaurus illustrated as a juvenile Macrocnemus by Sanz and Lopez-Martinez (1984).

Binocular Vision
Ellenberger determined that the large eyes of Cosesaurus poised over the small rostrum probably delivered 50 degrees of overlapping vision. That seems reasonable and sets Cosesaurus apart from Macrocnemus.

The Teeth 
Ellenberger reported the upper and lower three posterior teeth in the jaws of Cosesaurus were different that the others: broader and less pointed. These were precursors to the multicusped teeth found in derived fenestrasaurs.

The Naris
Ellenberger reported a slit-like naris in Cosesaurus, displaced from the snout tip. Such a naris is also found in all descendants of a sister to Huehuecuetzpalli, including pterosaurs and tanystropheids.

The Jaw Tip
Ellenberger considered the extended jaw tips to be beak precursors. The skull was also longer than the tooth row in the more primitive lizard, Huehuecuetzpalli. In more derived fenestrasaurs teeth protruded from the anterior jaws.

Figure 5. Current interpretation of Cosesaurus. Click to enlarge. Post-crania will be presented tomorrow.

Jugal
Ellenberger (1993) correctly illustrated a jugal with a new quadratojugal process in Cosesaurus.

Occiput
Ellenberger (1993) reported the occiput leaned posteriorly, which would have been appropriate for a reptile standing erect on hind limbs, whether bird ancestor or pterosaur ancestor.

Palate
Ellenberger illustrated as much of the palate as was visible and it was essentially correct and similar to that of pterosaurs, as reported earlier.

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
Ellenberger P and de Villalta JF 1974. Sur la presence d’un ancêtre probable des oiseaux dans le Muschelkalk supérieure de Catalogne (Espagne). Note preliminaire. Acta Geologica Hispanica 9, 162-168.
Ellenberger P 1978. L’Origine des Oiseaux. Historique et méthodes nouvelles. Les problémes des Archaeornithes. La venue au jour de Cosesaurus aviceps (Muschelkalk supérieur) in Aspects Modernes des Recherches sur l’Evolution. In Bons, J. (ed.) Compt Ren. Coll. Montpellier12-16 Sept. 1977. Vol. 1. Montpellier, Mém. Trav. Ecole Prat. Hautes Etudes, De l’Institut de Montpellier 4: 89-117.
Ellenberger P 1993. Cosesaurus aviceps . Vertébré aviforme du Trias Moyen de Catalogne. Étude descriptive et comparative. Mémoire Avec le concours de l’École Pratique des Hautes Etudes. Laboratorie de Paléontologie des Vertébrés. Univ. Sci. Tech. Languedoc, Montpellier (France). Pp. 1-664.
Evans SE 1988. The early history and relationships of the Diapsida. Pp. 221–260 in: Benton, M. J. (ed.) The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, Birds. Syst Assoc Sp Vol No. 35A. Clarendon Press, Oxford.
Gauthier JA 1986. Saurischian monophyly and the origin of birds. Memoirs of the California Academy of Science 8: 1–55.
Ostrom JH 1969. Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Peabody Museum of Natural History Bulletin 30: 1–165.
Peabody FE 1948.  Reptile and amphibian trackways from the Lower Triassic Moenkopi formation of Arizona and Utah.  University of California Publications, Bulletin of the  Department of Geological Sciences 27: 295-468.
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods.  Ichnos 7:11-41.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29: 1327-1330
Sanz JL and López-Martinez N 1984. The prolacertid lepidosaurian Cosesaurus aviceps Ellenberger & Villalta, a claimed ‘protoavian’ from the Middle Triassic of Spain. Géobios 17: 747-753.

Evolution of the Pterosaur Palate – part 8: Tapejaridae and Pteranodontidae

Earlier we looked at basal pterosaur palates, dimorphodontoid palates, campylognathoid palates, pre-azhdarchid palates, pre-ctenochasmatids, pre-ornithocheirids, and pre-Pterodactylus + Germanodactylus. Here in part 8 we’ll look at the pterosaur palate from Germanodactylus to Tapejara and Pteranodon (Fig. 1), following the phylogenetic order recovered in the large pterosaur tree).

 

Figure 1. The palates of several Tapejaridae and Pteranodontidae, both evolving from Germananodactylus.

Phobetor/Noripterus
Distinct from Germanodactylus rhamphastinus the skull of Phobetor/Noripterus was much sharper anteriorly. The palate was broad the teeth were partly covered by palate bone.

Sinopterus
Distinct from Phobetor, the palate of Sinopterus had no teeth, other than the single tooth at the tip (also found in dsungaripterids, but not preserved in Phobetor). The pterygoid was long and gracile. The ectopalatine was smaller, gracile and both processes were directed toward the cheek. The basipterygoids were fused to form a single broad bone.

Tapejara
Distinct from Sinopterus, the palate of Tapejara had a post premaxilla depression (that is, deeper in ventral view). The pterygoids were shorter. The quadrates were larger.

The Karlsruhe specimen of Germanodactylus 
Distinct from Germanodactylus rhamphastinus the pterygoids were much longer in the Karlsruhe specimen. Both processes of the ectopalatine contacted the cheek. The rostrum teeth were merged to become one tooth.

Nyctosaurus
Distinct from the Karlsruhe specimen, Nyctosaurus had no teeth, more of a maxillary palate and a smaller pterygoid. In the FHSM the anterior pterygoid was expanded. In the FMNH specimen the anterior pterygoid was sharp.

Pteranodon
Distinct from Nyctosaurus, the palate of Pteranodon was larger overall and sharper. The pterygoid lateral process was much larger and the medial processes were smaller. Posteriorly the pterygoids completely filled the former space between the quadrates and the basipterygoids here fused to form a single narrow process. Both processes of the ectopalatine were fused medially, separated only near the cheek. The vomer was completely fused to the maxillary palate plates.

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.

Giant Bipedal Pterosaur Tracks from Korea

Kim et al. (2012) recently reported, “Trackways with large, pes-only tracks with lengths up to 39 cm, characterized by elongate, subtriangular outlines, impressions of four digits and a subangular heel, are attributed to plantigrade pterodactyloids and assigned to
Haenamichnus gainensis ichnosp. nov.”

Figure 1. Samples from the Lower Cretaceous, Gain, Korea trackway (left) along with original tracings of photos, new color tracings of photos with hypothetical digits added in red, then "best match" candidate trackmakers from the monophyletic Shenzhoupterus/Tapejarid clade. PILs (parallel interphalangeal lines), subequal metatarsals and a small pedal digit 5 indicate a plantigrade configuration was likely.

Kim et al. (2012) were unable to find any manus impressions of these large tracks which they attributed to pterosaurs (Fig. 1) . [Nice to get further vindication evidence, even if not attributed or referenced.] Other than reports by Peters (2000, 2011) these Korean tracks are the first bipedal pterosaur tracks described.)

Figure 2. The Gain pterosaur tracks (ovals in black) crossing sauropod dinosaur tracks (in gray) and theropod tracks (three-toed in black, O2).

Finding Candidate Trackmakers
Kim et al. (2012) did not attempt to determine a specific pterosaur trackmaker for the Gain trackways. Taking available data and matching it to pterosaur pedes published in Peters (2011) several suitable candidate trackmakers are here identified (Fig. 3), all from the same monophyletic clade and all with representatives from Asia. These include Shenzhoupterus, Sinopterus and Tupuxuara. The only catch is, the Korean tracks were ~4x larger than the skeletal specimens and distinct from the original Haenamichnus tracks (also from Korea) which were attributable to azhdarchids, which had relatively smaller feet and longer legs producing a longer relative stride. Now the fun (= educated guesswork) begins.

Figure 3. Estimating Gain pterosaur trackmakers from track sizes and matching taxa. The Gain trackmakers were plantigrade, which is a suitable configuration given the PILs (Fig. 1) in both.

So How Big Were These Korean Pterosaurs?
Pterosaurs with 39 cm long feet were probably taller than a 6 foot tall human (Fig. 3). The ichnites were distinct from those of azhdarchids, but close to those in the Shenzhoupterus/Tupuxuara clade. Such a jump in size probably indicates a distinct cranial morphology from known smaller sisters (Fig. 3). The relatively shorter strides of the Gain pterosaurs (shorter than in Haenimichnus) is likely due to their relatively shorter legs. These giant pterosaurs held their wings above the matrix while walking as demonstrated earlier in this animation of Pteranodon, an unrelated pterosaur with a similar build.

Figure 4. Pteranodon walking. Click to animate. Note the femur is drawn and moves in the parasagittal plane for ease of animation. When properly sprawled the butt would drop a wee bit. The feet may have been plantigrade. They are not well preserved.

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
Kim JY, Lockley MG, Kim KS, Seo SJ and Lim JD 2012. Enigmatic Giant Pterosaur Tracks and Associated Ichnofauna from the Cretaceous of Korea: Implication for the Bipedal Locomotion of Pterosaurs. Ichnos 19 (1-2): 50-65.DOI:10.1080/10420940.2011.625779 online
Peters D 2000a. Description and Interpretation of Interphalangeal Lines in Tetrapods. Ichnos, 7: 11-41
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

The Choices We Make as Paleontologists

A recent paper by Dr. Mark Witton (2012) re-reconstructed the skull of Istiodactylus latidens (Hooley 1912) based on the recovery of a central portion of the maxilla and mandible.

 

Figure 1. Istiodactylus skull bones (center). As reconstructed by yours truly (left) with restored areas in gray. As reconstructed by Witton (2012, right). Compare these to the skulls of Nurhachius, Istiodactylus sinensis and SMNK PAL 1136.

The Choices We Make
Witton (2012) chose to minimize the missing bones and so determined that Istiodactylus had a shorter skull than previously imagined and also relatively shorter and taller than the skull of other istiodactylids. I chose to add more missing material to more closely match the apparent margins and to match sister taxa, like SMNK PAL 136, Nurhachius and Istiodactylus sinensis. So, ironically in this case, I was the traditional guy and Witton (2012) was the heretic.

Witton (2012) also chose not to delineate the various skull sutures, even though they were visible. Witton (2012) deepened the posterior mandible. I did not. Again, it’s good to do comparative studies with sisters if doubts persist.

These are the choices all paleontologists make. Those that can be supported, all other things being equal, will usually win out.

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
Andres B and Ji Q 2006. A new species of Istiodactylus (Pterosauria, Pterodactyloidea) from the Lower Cretaceous of Liaoning, China. Journal of Vertebrate Paleontology, 26: 70-78.
Hooley RW 1913. On the skeleton of Ornithodesmus latidens. An ornithosaur from the Wealden shales of Atherfield (Isle of Wight)”, Quarterly Journal of the Geological Society, 69: 372-421
Howse SCB, Milner AR and Martill DM 2001. Pterosaurs. Pp. 324-335 in: Martill, D. M. and Naish, D., eds. Dinosaurs of the Isle of Wight, The Palaeontological Association
Witton MP 2012. New Insights into the Skull of Istiodactylus latidens (Ornithocheiroidea, Pterodactyloidea). PLoS ONE 7(3): e33170. doi:10.1371/journal.pone.0033170 

wiki/Istiodactylus

Addendum
Dr. Mark Witton commented on this blog today. His remarks are important and I thank him for them. He said many things, but, unfortunately, did not offer more detailed image evidence to back up his statements. Below, some images that may help explain my “choices.” I revised the rostrum of Istiodactylus because I no longer see sufficient evidence for fenestrae. I deepened the posterior mandible because Dr. Witton mentioned it was broken on its ventral rim, but I did not deepen it to the extent Dr. Witton did. I tried to keep in accord with Nurhachius and other sister taxa.

Figure x. Istiodactylus snout. Note the clear delineation of the premaxilla from the rest of the rostrum. This is more distinct than I have seen in many taxa. The rest of the rostrum appears to be splintered, but splintered nearly identically on both sides. Thus many of these breaks can be interpreted as sutures. In this way the jugal and nasal extends anterior to the antorbital fenestra, a configuration not recognized by other workers because they have not yet cared to note the details in the material and duplicated in all other sister taxa. Witton's (2012) skull reconstruction showed no sutures whatsoever, which is the typical and traditional way to present pterosaur skulls. In any case, it should important for paleontologists to delineate bone sutures when they can. I look forward to further changing my reconstruction if and when appropriate data comes in.

Figure y. The skull and mandibles of Nurhachius. Note the left mandible appears to artificially deepen the right mandible, which may be the reason why Witton (2012) deepened the posterior mandible of Istiodactylus. The two mandibles are color coded here. The anterior mandible is purple because it is preserved in dorsal view beyond the break. The posterior mandible is narrow, as reconstructed above in Istiodactylus. The ventral rim of the posterior mandible may be broken, but there can't be much more to it, if it is to match sister taxa.

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.

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.

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

Evolution of the Pterosaur Palate – part 7: Pterodactylus and Germanodactylus

Earlier we looked at basal pterosaur palates, dimorphodontoid palates, campylognathoid palates, pre-azhdarchid palates, pre-ctenochasmatids and pre-ornithocheirids. Here in part 7 we’ll look at the pterosaur palate from Scaphognathus to Pterodactylus longicollum (aka: Diopecephalus, Fig. 1) and to Germanodactylus rhamphastinus, following the phylogenetic order recovered in the large pterosaur tree). As previously mentioned, the pterosaur palate has been largely overlooked, unless it was specifically exposed.

Figure 1. Click to enlarge. Evolution of the pterosaur palate from Scaphognathus to Pterodactylus and Germanodactylus.

No. 31
Distinct from the Maxburg specimen of Scaphognathus (No. 110 in the Wellnhofer 1970 catalog), No. 31 was smaller overall with a sharper premaxilla. The medial two premaxillary teeth extend anteriorly. The teeth are smaller and more homodont. The lateral process of the ectopalatine was more robust. The pterygoids were straighter.

Ningchengopterus
Distinct from No. 31, the palate of Ningchengopterus was longer posteriorly with more gracile elements, especially the pterygoid.

Pterodactylus scolopacicps, specimen No. 21
Distinct from Ningchengopterus, the palate of the No. 21 specimen of Pterodactylus was longer still with a more robust vomer. The pterygoids were essentially straight and underlapping the ectopalatines.

Pterodactylus antiquus, specimen No. 4
Distinct from P. scolopaciceps, the palate of the No. 4 specimen of Pterodactylus had smaller teeth and a rounder premaxilla tip. The pterygoid (still hidden beneath a thin layer of limestone) was more robust.

Pterodactylus longicollum, specimen No. 58
Distinct from P. antiquus, the palate of the No. 58 specimen of Pterodactylus (Diopecephalus) had larger teeth, a broader set of vomers, a broader palate and the pterygoids extended over the maxilla (but these may be only the anterior processes of the ectopalatine). The lateral process of the ectopalatine was fenestrated.

No. 12
At the base of the Germanodactylia and derived from a sister to the Maxburg specimen of Scaphognathus (Fig. 1), is tiny No. 12. There is very little difference in the palate, except the medial pterygoid is bifurcated. The lateral process of the medially turned pterygoid became a new anterior process in the Maxburg specimen of Scaphognathus. In No. 12, that process is much longer, reflecting the increased length of the rostrum.

Germanodactylus rhamphastinus, specimen No. 64
Overall larger than and distinct from No. 12, the No. 64 specimen of Germanodactylus rhamphastinus has a larger maxilla palate area. The anterior medial process is longer, but the lateral process, if present, was not identified.

Trends
In this clade the trend was toward a larger contribution to the palate by the maxilla and layering of the pterygoid beneath the ectopalatine. In the Pterodactylus lineage the pterygoids were parallel to each other. In the Germanodactylus lineage the pterygoids formed a triangle.

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.