New Triassic basal dimorphodontid: Caelestiventus

Britt, et al. 2018
bring us a new desert-dwelling Triassic pterosaur, Caelestiventus hanseni (Figs. 1, 2; BYU 20707, Museum of Paleontology at Brigham Young University) from western North America. They nest it with Dimorphodon (Fig. 1), from the English Jurassic, although Preondactylus (Fig. 3) is also similar, with a huge naris, and also from the Late Triassic. Caelestiventus is larger than most Triassic pterosaurs, with a wingspan of at least 1.5 meters. Coeval Raeticodactylus is similar in size and also fills in the lower orbit with a thin sheet of bone.

Britt, et al. also confirm the nesting
of ‘Dimorphodon’ weintraubi with anurognathids, something first published by Peters 2011 and reported here the same year.

Unfortunately
Britt and colleagues nest anurognathids as the sister taxa to Dorygnathus due to taxon exclusion. In the large pterosaur tree (LPT, 234 taxa) anurognathids nest with and arise from dimorphodontids. Among the many taxa missing from the Britt et al. tree is the IVPP giant embryo anurognathid, a completely preserved specimen, and Mesadactylus, another Jurassic transitional sister basal to anurognathids… also from North America.

Figure 1. Triasic Caelestiventus skull compared to Jurassic Dimorphodon. Readers, don’t do the easy thing and go to the Wellnhofer diagrams for your pterosaur skulls. Use real data.

It’s always wonderful to see a new pterosaur taxon.
Congratulations to all coauthors on this paper.

Figure 2. The skull of Bergamodactylus (MPUM 6009) the most primitive pterosaur in the LPT.  No antorbital fossa here and not tested by Britt et al.

The sculptor of the skull
(Fig. 1) put a ‘Roman nose’ on the restoration of Caelestiventus. That illustration will float around the paleo-universe forever. However, I take my cue from the Triassc age of the specimen and the downturned dentary, as in the Triassic basalmost pterosaur, Bergamodactylus (Fig. 2), which has an unexpanded naris, to create a more transitional naris (Fig. 1), and from Preondactylus (Fig. 3), a closer relative with a large, yet straight naris, rather than create a derived version with more of a curve than Dimorphodon had.

Figure 3. Preondactylus from the Late Triassic is basal to Dimorphodon in the LPT.

The staff or hired artist
charged with illustrating Caelestiventus in vivo (Fig. 4) made a few mistakes. These were generated, no doubt, by the many false paradigms floating around out there. Here they are shown and corrected. (Just found out the artist is Michael Skrepnick, Dinosaursinart.com)​

1. The manual claws should point down toward the palm, as in most tetrapods
2. Pedal digit 5 should be on the lateral side of a much larger foot and it should not be involved in the uropatagia.
3. The tail should be shorter if closer to Dimorphodon than to Preondactylus. Otherwise it might be that long.
4. The rostrum is straight inLate Triassic sister, Preondactylus, so  perhaps a straight angled rostrum is more appropriate here.
5. The wing membranes were stretched between elbow and wing tip, as all soft tissue pterosaur fossils demonstrate.
6. The cranium probably tipped down posteriorly, as all related taxa demonstrate (Figs. 1–3).

Figure 4. Pity the poor staff artist trying to get a pterosaur correct in today’s climate. Here the original and revised morphologies are presented. Digit 5 need to go to the outside of a large foot and the tail is short.

Perhaps hoping to support the invalid archosaur origin of pterosaurs hypothesis,
Britt et al report the margin of an antorbital fenestra bears a remnant of a fossa. We looked at a similar interpretation earlier when Nesbitt and Hone 2010 attempted to pull a Larry Martin with that single trait from Dimorphodon. Thankfully, Britt et al. did not attempt to use Euparkeria or any phytosaurs for outgroups. But, regrettably, they didn’t use Cosesaurus either (Fig. 5). Avoiding further controversy, they left the basalmost node generic: “Pterosauria”.

Addendum: checking the SuppMat .nex file,
I see they employed the tritiosaur lepidosaur, Macrocnemus, and two large archosauriforms, Postosuchus and Herrerrasaurus for outgroup taxa. That still does not get you very far based on the verified and validated taxa listed below. Neither Postosuchus nor Herrerasaurus are related to Macrocnemus and pterosaurs.

Figure 5. Basal pterosaurs and their outgroups in the LPT.

Late addendum
Adding Caelestiventus to the LPT nests it basal to the Dimorphodon clade, not with Dimorphodon.

Figure 1. Maxilla, nasal and jugal of Caeletiventus, plus full mandible casts created by CT scans. Colors added here.

References
Britt BB, Dalla Vecchia FM, Chure DJ, Engelmann GF, Whiting MF, and Scheetz RD 2018. Caelestiventus hanseni gen. et sp. nov. extends the desert-dwelling pterosaur record back 65 million years. Nature Ecology & Evolution. doi:10.1038/s41559-018-0627-y.
Nesbitt SJ and Hone DWE 2010. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233
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

https://en.wikipedia.org/wiki/Caelestiventus

Dimorphodon revisited

The odd pterosaur, Dimorphodon
was one of the first taxa included in the large reptile tree (LRT, 1132 taxa). Here I revise earlier errors on the BMNH 41212 specimen (Fig. 1), including adding a short tail discovered a few days ago and also adding more dorsal vertebrae.

Figure 1. The three Dimorphodon specimens traced from the fossils.

Here is the in situ fossil with bones colorized (Fig. 2).

Figure 2. The BMNH 4121 fossil of Dimorphodon here colorized using DGS. Colors match the reconstruction, except for the skull.

Earlier the skull was reconstructed. Here it is again (Fig. 3). This was done to show the mandible did not have a fenestra, only a shifted surangular.

Figure 3. The skull of Dimorphodon macronyx. Above: in situ. Middle: Restored. Below: Palatal view. Not settled on the depth of the mandible. The long replaceable teeth suggest a deeper mandible is more appropriate.

References
Buckland W 1829. Proceedings of the Geological Society London, 1: 127
Owen R 1859. On a new genus (Dimorphodon) of pterodactyle, with remarks on the geological distribution of flying reptiles.” Rep. Br. Ass. Advmnt Sci., 28 (1858): 97–103.
Nesbitt SJ and Hone DWE 2010. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233
Padian K 1983. Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Museum, Postilla, 189: 1-44.
Sangster S 2001. Anatomy, functional morphology and systematics of Dimorphodon. Strata 11: 87-88

wiki/Dimorphodon

The other Dimorphodon skull (BMNH R 1035) unscrambled

We know of
several Dimorphodon (Buckland 1829, Owen 1859) Hittangian, Early Jurassic ~195 mya) specimens from Europe.

1. BMNH (NHUK PV) R1034a Mary Anning’s discovery and the holotype, a misarticulated skeleton lacking a skull and tail (Fig. 1)
2. BMNH (NHUK PV) R 1035 includes a skull, cervicals and wings (Figs. 1, 2)
3. BMNH 41212 is a nearly complete specimen lacking a tail (Fig. 1).
4. BMNH? a complete tail (Fig. 1)
5. Other BMNH specimens. presumably disarticulated bones
6. YPM 350, YPM 9182 and other Yale specimens, several disarticulated bones including a partial skull

Dimorphodon? weintraubi (IGM 3494, Clark et al. 1994, 1998; Early to Middle Jurassic, ~175 mya) nests several nodes away, with basal anurognathids. It lived 20 million years later in North America.

Figure 1. The three most complete Dimorphodon specimens, BMNH 41212, BMNH R1034, and BMNH R1035. BMNH (British Museum of Natural History) used to be NHUK (Natural History United Kingdom).

The BMNH R1035 specimen of Dimorphodon
has not been figured very often because the skull is somewhat scrambled  Here it is traced (Fig. 2) and reconstructed (Fig. 1). It is quite similar to that of the BMNH 41212 specimen, with only slight modifications.

Figure 2. Dimorphodon specimen BMNH (formerly NHUK) R1035 with elements traced and segregated to reduce the chaos. Here the complete wing was recovered along with cervicals and occipital elements. Click to enlarge.

The ‘scrambled’ 1035 material differs
from the 41212 material in several traits:

1. The naris is slightly larger relative to the antorbital fenestra
2. The sclera ring is smaller
3. The mandible is deeper
4. The metacarpus and wing are longer

When you look up Dimorphodon online
at Wikipedia the authors do not identify D. weintraubi as an anurognathid. And they follow Clark et al. in asserting that Dimorphodon had plantigrade pedes based on the metatarsalphalangeal butt joint. We looked at that problem earlier here and Peters (2000) also covered that topic, but essentially the metatarsophalangeal butt joint was immobile, but the cylindrical interphalangeal joints provided the required extension to create a digitigrade pes that matches digitigrade pterosaur and Rotodactylus ichnites in which the proximal phalanges are always elevated. It’s a common pattern: Sometimes it takes the paleo crowed a long time to accept certain facts.

Figure 3. from Wikipedia, my sculpture of Dimorphodon now found in several museums. The curly-cue tail, anteriorly-planted fingers and plantigrade feet are all unnatural and not part of the original model.

And then, of course manual digit 5 and wing ungual
are both present in the 1035 specimen (Figs. 4, 5).

Figure 4. Wingtip ungual in the BMNH 1035 specimen of Dimorphodon.

Yes, they are difficult to see
unless you look for them and trace them. But think how long it took to find hind limbs in fossil whales, known for over 150 years prior to that discovery.

Figure 5. Manus of the BMNH 1053 specimen of Dimorphodon highlighting vestigial digit 5 in pink.

A while back
Nesbitt and Hone 2010 attempted to show that the 41212 specimen of Dimorphodon had a mandibular fenestra in a desperate and misguided attempt at providing archosaur traits to pterosaurs. That was bogus, as noted earlier. Those two didn’t want to take into account the slipped surangular on the specimen. In the 1035 specimen the surangular is in place and no mandibular fenestra is present.

References
Buckland W 1829. Proceedings of the Geological Society London, 1: 127
Clark J, Montellano M, Hopson J and Fastovsky D. 1994. In: Fraser, N. & H.-D Sues, Eds. 1994. In the Shadows of Dinosaurs. New York, Cambridge: 295-302.
Clark J, Hopson J, Hernandez R, Fastovsk D and Montellano M. 1998. Foot posture in a primitive pterosaur. Nature 391:886-889.
Nesbitt SJ and Hone DWE 2010. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233
Owen R 1859. On a new genus (Dimorphodon) of pterodactyle, with remarks on the geological distribution of flying reptiles.” Rep. Br. Ass. Advmnt Sci., 28 (1858): 97–103.
Nesbitt SJ and Hone DWE 2010. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233
Padian K 1983. Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Museum, Postilla, 189: 1-44.
Peters D 2000. Description and Interpretation of Interphalangeal Lines in Tetrapods. – Ichnos 7(1): 11-41.
Sangster S 2001. Anatomy, functional morphology and systematics of Dimorphodon. Strata 11: 87-88

wiki/Dimorphodon

 

Data denial you can listen to on a podcast

Dr. Mark Witton

Dr. Mark Witton is a paleontologist,
author and illustrator, but based on a Liz Martin interview podcast denies the existence of pterosaur ancestors. Like his friends, Dr. David Hone (another data denier), and Dr. Darren Naish, Dr. Witton believes pterosaurs “appeared fully formed in the fossil record. We don’t have the pterosaur Archaeopteryx.”

Sadly this purposefully ignores 
the published literature (Peters 2000 is now 15 years old) online phylogenetic analyses (now 4 years old) and YouTube videos (just a few weeks old) that all provide a long list of pterosaur ancestors that demonstrate a gradual accumulation of pterosaur traits. Why does Dr. Witton prefers to hide his head in the sand rather than examine, test and/or accept published studies? Could this be academic bigotry? (definition: intolerance toward those who hold different opinions from oneself)

Witton believes pterosaurs “are close relatives of dinosaurs.”

If so, then were are the common ancestors that show a gradual accumulation of character traits? Answer: You can’t find them because they are not there. Other taxa share more traits with pteros and dinos than either does with each other. This is the outmoded “Ornithodira” concept.

Witton says he did not expect
that the Jurassic pterosaur, Dimorphodon would be adept at walking on the ground (despite having digitigrade pedes and fully interned femoral heads). Again, published literature demonstrates just the opposite (Padian 1983). Glad to see that Dr. Witton is getting on board with a more terrestrial Dimorphodon.

Dr. Witton waxed on about Solnhofen juvenile and subadult pterosaurs,
agreeing with Bennett (1995) who lumped Rhamphorhynchus into one species by plotting long bone lengths on a graph. Witton thought different species should have a dramatic difference in wing shape. Not so. He didn’t mention foot shape and overall morphology, which varies quite widely and logically when phylogenetic analysis is employed (Fig. 2).

Figure 2 Bennett 1975 determined that all these Rhamphorhynchus specimens were conspecific and that all differences could be attributed to ontogeny, otherwise known as growth to maturity and old age. Thus only the two largest specimens here were adults. Witton agrees that all these are conspecific. Do you agree with Witton? Decide for yourself. Click to enlarge.

Witton follows the Lü et al. (2009) analysis
that nested Darwinopterus as a transitional fossil combination of pterodactyloid skull and basal pterosaur post crania. Other analyses ( Wang et al 2009, Andres 2013, Peters online) do not support that hypothesis. Only Peters online (based on Peters 2007) includes a large selection of sparrow-sized Solnhofen pterosaurs, keys to the origin of all later clades. Along the same lines, Witton believes in Modular Evolution, which is falsified in phylogenetic analysis and apparently occurs only in their vision of Darwinopterus.

Witton reports that some azhdarchids had short necks.
Not sure which azhdarchids he is talking about. Evidently that is sneak preview on unpublished papers. The large pterosaur tree indicates that going back to the Late Jurassic, all azhdarchids and their ancestors had very long necks, even as hand-sized taxa (Fig. 3).

Figure 3. The Azhdarchidae. Click to enlarge. No short necks here, except way down toward the left. Not saying they could not evolve. Just saying I haven’t seen them yet. 

Witton reports there are small birds but no small pterosaurs
from the Upper Cretaceous — but no small dinosaurs either — so suggests there may be a preservational bias in the lack of small pterosaurs… but no such bias for small birds. Actually there are small bird fossils from the Late Cretaceous, and they ARE dinosaurs, and no small pterosaurs. Lacking tiny pteros in the Late Cretaceous spelled their doom. Only small and tiny pterosaurs survived the Latest Jurassic extinction event and only these were basal to later giants. So no darwinopterids had descendants in the Cretaceous. Because there were no tiny Late Cretaceous pterosaurs, none survived the Late Cretaceous extinction event.

Can we blame this on a bad mentor?
Dr. Witton has accumulated a great deal of pterosaur knowledge and expresses it wonderfully in his many paintings. Unfortunately, like Hone and Naish, he was ‘raised’ by wrong-minded mentors and continues his false beliefs (= he has not tested his or competing hypotheses in phylogenetic analyses) to this day. Earlier we looked at the many problems in Dr. Witton’s book on pterosaurs.

Dr. Don Prothero

Some insight into that sort of thinking…
it’s not that uncommon.
Dr. Don Prothero in a YouTube Video provides great insights into the Creationist mindset that finds strong parallels in the current thinking of Dr. Mark Witton, Dr. David Hone and Dr. Darren Naish.

Notes from the Prothero video

1. Humans are not rational machines
2. We all employ motivated (emotional, wants and needs) reasoning, not logical reasoning
3. We are all belief engines and we all create a world view or core belief
4. Because of that we don’t like to hear anything that does not fit our world view
5. AND we use reason to do what we want data to do, not what its telling us. We use ANY tricks to make the evidence of the world fit our beliefs, or twist it to fit, or deny it or ignore it. Michael Shermer, founder of the Skeptics Society and author of “The Believing Brain” writes, “We all support the world we already have.”

Bottom line:
Witton, Hone and Naish don’t like ReptileEvolution.com because it doesn’t support the paleo world they already have. Like Creationists they display the following traits raised by Prothero:

1. Reduction of cognitive dissonance (= the state of having inconsistent thoughts, beliefs, or attitudes, especially as relating to behavioral decisions and attitude change) when presented with evidence that works against that belief, the new evidence cannot be accepted.
2. Tribalism = we learn our world from whoever we were raised by. And all three professors are friends of one another.
3. Deep innate psychological tendencies are genetic = there are some people who readily accept new ideas and there are some people who do not. Unfortunately, all three appear to have the same gene.
4. Confirmation bias (= the tendency to interpret new evidence as confirmation of one’s existing beliefs or theories.) Thus when Hone and Benton (2007, 2009) come out with the worst paper I have reviewed, Naish and Witton support it anyway.
5. Cherry picking (= remembering the hits, forgetting the misses). Hone, Witton and Naish like to pick on poor Longisquama, which was difficult, but not impossible to interpret and all three like to ignore the whole point of ReptileEvolution.com, the cladograms, both the large reptile tree and the large pterosaur tree. Note that no other pterosaur worker has produced competing interpretations of Longisquama of equal detail nor competing cladograms that include tiny pterosaurs. In this regard these pterosaur workers are exactly like Dr. Feduccia and the late Dr. Martin (who deny the theropod-bird link and never employ phylogenetic analysis) and also like extant Creationists, who likewise never employ phylogenetic analysis. Remember when Hone and Benton first deleted the taxa that Peters 2000 proposed, then deleted Peters 2000 from the competition? This was cherry picking at its best.
6. Qiuote mining (= in this case finding images and hypotheses that have been long ago trashed in order to undermine the site. These are essentially ad hominem (directed against a person rather than the position they are maintaining) attacks as they blackwash my methods (which they practice too) and the entire website while they could have gotten specific about one problem or another.
7. Missing the forest for the trees (= The big picture) is the large reptile tree cladogram. This is created by a huge mass of data and becomes strengthened with every additional taxon – all of which affect every other taxon. In such an analysis you can remove data, remove taxa, remove characters and nothing falls apart. The subsets are just as strong as the dataset itself. But Hone, Naish and Witton refuse to acknowledge that, preferring to continue their thinking that pterosaurs appeared suddenly in the fossil record, like on the fourth day of Creation. Phylogenetic analysis would solve their quandary, if only they would give it a chance.

Dr. Prothero asks: Why is science different?
Prothero answers his own question in this fashion:

1. Science (like ReptileEvolution.com) is always testing with falsification, prove things wrong, correcting mistakes. Presently I’ve made over 50,000 corrections in drawings and scores and look forward to many more. Getting it right is important.
2. Science (like ReptileEvolution.com) is always tentative, no claim to final truth. I am always looking for a competing hypothesis. Witton, Hone, Naish, Bennett and other referees are making sure my papers are not getting published. They don’t like it when their claims are disputed here at PterosaurHeresies.
3. Science (like ReptileEvolution.com) works! It provides answers that make sense, can be replicated, and can provide predictions.
4. In Science peer review cancels individual biases. Sadly the current pterosaur referees, Hone, Witton, Naish and others, are all from the same school of thought. Every day I hope to change that, to open them up to accept more valid hypotheses that work!
5. In Science, if you’re not pssing people off, you’re not doing it right. Well, I must be doing something right, because Witton and Naish are never praising my work. It would be great if we could argue about it. I guess we’re doing that here.

Prothero finished with a cartoon
of a professor who was showing his cognitive dissonance: “If P is false, I will be sad. I do not wish to to be sad. Therefore, P is true.”

This is human nature.
We all have it. We all get jealous, ambitious. disappointed. As scientists we have to get over our human nature and let testing and experimentation rise above human nature. We have to be like Galileo, not Aristotle.

References
Bennett SC 1995. A statistical study of Rhamphorhynchus from the Solnhofen limestone of Germany: year classes of a single large species. Journal of Paleontology 69, 569–580.
Lü J, Unwin DM, Jin X, Liu Y and Ji Q 2009. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society London B  (DOI 10.1098/rspb.2009.1603.)
Padian K 1983. Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Museum, Postilla, 189: 1-44.
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2007. The origin and radiation of the Pterosauria. Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27
Wang X, Kellner AWA, Jiang S, Meng X. 2009. An unusual long-tailed pterosaur with elongated neck from western Liaoning of China. Anais da Academia Brasileira de Ciências 81 (4): 793–812.

SVP 5 – Triassic pterosaur from Utah

Britt et al. (2105) found a Late Triassic pterosaur in Utah, described in the following SVP abstract.

From the abstract:
“We previously reported on a wealth of tetrapods, including multiple individuals each of a coelophysoid, a drepanosauromorph, two sphenosuchian taxa, and two sphenodontian taxa. All are preserved along the shoreline of  a Late Triassic oasis in the Nugget Sandstone at the Saints & Sinner Quarry (SSQ). Recently, we discovered a non-pterodactyloid pterosaur at the quarry, represented by a partial uncrushed, associated/articulated skull imaged via micro CT. The premaxillaries are spoon-shaped rostrally; the maxilla is a simple bar with a needle-like nasal process, the suborbital jugal/quadratojugal blade is high; the nasal is a short, narrow rectangle; and the fused frontals are wide with a moderately high, tripartite sagittal crest. The lower jaws are complete, with a long, slender dentary terminating rostrally in a downward-bend with a ventral expansion, a short postdentary complex and a short retroarticular process. The quadrate-articular joint is well above the tooth row. At least three, widely spaced, conical teeth are in the premaxilla; maxillary teeth are mesiodistally long (3 widely-spaced mesially and 7 close together distally); and on the dentary there are two apicobasally high, widely-spaced mesial teeth and ~20 small, multicusped, low-crowned distal teeth. The frontals and lower jaws are extensively pneumatized. With a 170 mm-long lower jaw, this is two times larger than other Triassic pterosaurs and only the second indisputable Triassic pterosaur from the Western Hemisphere (the other is from Greenland). This is the only record of desert-dwelling nonpterodactyloids and it predates by >60 Ma all known desert pterosaurs. Whereas most pterosaurs are known from fine-grained marine or lacustrine environments, and other Triassic forms are smaller, the SSQ specimen shows that early pterosaurs were widely distributed, attained a large size, and lived in wide range of habitats, including inland deserts far (>800 km) from the sea. Finally, the SSQ pterosaur corroborates the Late Triassic age of the fauna based on drepanosaurs because pterosaurs with multicusped teeth are presently known only from the Upper Triassic.”

The description
sounds like an early dimorphodontid, but withe the deep jugal of Raeticodactylus. The size of the skull is similar to both. Unfortunately, too few clues to go on. I’ll wait for the paper… eagerly!

References
Britt BB, Chure D, Engelmann G and Dalla Vecchia F et al.  2015. A new, large, non-pterodactyloid pterosaur from a Late Triassic internal desert environment with the eolian nugget sandstone of Northeastern Utah, USA indicates early pterosaurs were ecologically diverse and geographically widespread. Journal of Vertebrate Paleontology abstracts.

 

 

On the origins of Dimorphodon and Eudimorphodon

At the base of the Pterosauria
there was one false evolutionary start that gave us Austriadactylus (the Austrian specimen) and Raeticodactylus. Thereafter the clades kicked into full gear with the basal dichotomy, dimorphodontids (which begat anurognathids) and eudimorphodontids (which begat everything else.)

Knowing that a picture tells the story here are the players (Fig. 1):

The origins of Dimorphodon and Eudimorphodon find a common ancestor close to Austriadactylus (the Italian specimen) and prior to that, the basal pterosaur, MPUM 6009. All are Late Triassic except Dimorphodon. The robust skull of eudimorphodontids suggests piscatory (fish eating) while the fragile skulls of dimorphodontids suggests insectivore. The enlarged naris was a legacy from the Italian specimen

The basic dichotomy of dimorphodontids and eudimorphodontids (Fig. 1) set the pace for the rest of pterosaur evolution. One emphasized the longer, leaner snout of a fish and tetrapod eater while the other had a taller, more fragile and ultimately wider rostrum (in anurognathids) of an insect eater.

You can see (Fig. 1) with such short fore limbs and long hind limbs, with toes under the center of balance at the shoulder glenoid (arm pit) that quadrupedal locomotion was something that would have to be invented in the future of these Triassic clades.

BTW
Yesterday’s note on Atopodentatus garnered about twice as many viewers. Let me know why all the interest because I don’t have a clue.

A closer look at the “antorbital fossa” in two pterosaurs, Raeticodactylus and Dimorphodon

Nesbitt and Hone (2010) broke with tradition to propose that certain pterosaurs had a mandibular fenestra. We discussed this mistake earlier. Now we are going to look at another one of their other futile grasps at the archosaur straw, a purported antorbital fossa in Dimorphodon (Figs. 1, 2) and Raeticodactylus (Fig. 3). An antorbital fossa is not found in ANY other pterosaur. And the two examples they propose don’t match each other in any way or fashion. So, ironically, Nesbitt and Hone (2010) were acting as heretics and I am here to hold the traditional line.

Figure 1. From Nesbitt and Hone 2010, a purported antorbital fossa in Dimorphodon. Note where it is compared to figure 3 (below). This triangular strut support is a little thinner and therefore a little deeper than the rest of the cylindrical ascending process. Dimorphodon depresses this area more than other pterosaurs, like Eudimorphodon.  This also may be due to crushing, similar to the crushing surrounding each tooth. Oops. Yeah, there it is…

Figure 2. The jugal of Dimorphodon adds depth to the tooth-bearing portion of the maxilla, adding to the impression of an antorbital fossa, a fact overlooked by Nesbitt and Hone (2010).

Dimorphodon has one of the largest and lightest skulls of any early Jurassic or Triassic pterosaur. The nasal, antorbital and orbital fenestra made up the vast majority of the skull separated by the thinnest struts of bone in the Pterosauria. Like any good engineer Dimorphodon supported its grid-like struts with small triangles of bone, like the one at the base of the slender ascending process of the maxilla. Paper thin, this triangular support at the base of the cylindrical ascending process was identified as an antorbital fossa by Nesbitt and Hone (2010). No other pterosaur depresses, or thins this area, which may be thinner due to crushing. Note the areas between the maxillary teeth, which exhibit similar crushing. Nesbitt and Hone (2010) also failed to note the presence of the laminated jugal (Fig. 2), which adds depth to the tooth-bearing portion of the maxilla.

Figure 2. Raeticodactylus skull. According to Nesbitt and Hone (2010) the red areas represent the antorbital fossa. Here these areas are interpreted as the transverse width of the  girder-like ascending process (stronger to support that rhino-like horn when it’s called into action), and otherwise typically buried in the matrix. At the top the transverse lacrimal is equally wide in the Z-axis. Note the ventral view of the skull (in blue, twisted during crushing) that confirms we’re seeing the ventral aspect of the maxilla/lacrimal portion of the antorbital fenestra. Also note this purported antorbital fossa is not the same as that seen in Dimorphodon (Fig. 1). No homology here.

Raeticodactylus was also promoted by Nesbitt and Hone (2010) as having an antorbital fossa, but there’s no basal triangular support for the maxillary ascending process here. So the two do not reflect homologous morphologies (which should have raised a red flag, except they were so hell-bent on providing “evidence” for an archosaur connection they ignored or overlooked this key fact). Instead what we’re seeing is the crushed transverse width of the girder-like ascending process of the maxilla and the ventral aspect of the lacrimal and skull roof. The skull had to be stronger than a typical pterosaur skull. After all it was doing something with that rhino-like horn and this reinforcement tells us it wasn’t just for display~!

Bottom line: No mandibular fenestra. No antorbital fossa. Pterosaurs are not archosaurs.

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
Buckland W 1829. Proceedings of the Geological Society London, 1: 127
Owen R 1859. On a new genus (Dimorphodon) of pterodactyle, with remarks on the geological distribution of flying reptiles.” Rep. Br. Ass. Advmnt Sci., 28 (1858): 97–103.
Nesbitt SJ 2011.  The early evolution of archosaurs: relationships and the origin of major clades.  Bulletin of the American Museum of Natural History 352: 292 pp. online pdf
Nesbitt SJ and Hone DWE 2010. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233
Padian K 1983. Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Museum, Postilla, 189: 1-44.
Sangster S 2001. Anatomy, functional morphology and systematics of Dimorphodon. Strata 11: 87-88

wiki/Dimorphodon

The carpus of Dimorphodon restored

Several Dimorphodon specimens are known. None of the presacral specimens have tails and vice versa. The BMNH 41212 (

R.1034)

specimen is the most complete, but in situ one carpus is beneath a foot and the other is buried in the matrix, likely beneath the skull where fingers appear in the naris.

So we look elsewhere for the carpus
The Mary Anning Dimorphodon skull , NHUK PV R 1035  (Fig. 1) is another roadkill, mixing posterior skull and hand elements together in a mishmash. An extremely precise drawing (Owen 1874) provides the details needed to reconstruct the carpus and hand of this specimen.

Figure 1. Click to enlarge. Rebuilding the carpus and hand of Dimorphodon based on the Mary Anning specimen, R 1034. Yes, thats digit 5, as expected, a vestige on the dorsal side of metacarpal 4.

To no one’s surprise, the carpus of Dimorphodon is just like that of any other basal pterosaur. Nothing big to report on here.

Unfortunately the check and cranium are not clearly visible here. Parts are broken and partially buried. In any case,there is no mandibular fenestra here, as earlier discussed,

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
Buckland W 1829. Proceedings of the Geological Society London, 1: 127
Owen R 1859. On a new genus (Dimorphodon) of pterodactyle, with remarks on the geological distribution of flying reptiles.” Rep. Br. Ass. Advmnt Sci., 28 (1858): 97–103.
Owen R 1874. Monograph of the fossil Reptilia of the Mesozoic Formations. Part I. Pterosauria. Palaeontographical Society of London, 27: 1-14
Nesbitt SJ and Hone DWE 2010. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233
Padian K 1983. Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Museum, Postilla, 189: 1-44.
Sangster S 2001. Anatomy, functional morphology and systematics of Dimorphodon. Strata 11: 87-88
wiki/Dimorphodon

Why Dimorphodon weintraubi is not a Dimorphodon

Figure 1. Click to enlarge. Dimorphodon weintraubi made the cover of Nature

Dr. Jim Clark et al. (1994, 1998) described in Nature an uncrushed partial skeleton, IGM 3494, of a medium-sized Early to Middle Jurassic pterosaur from Mexico and attributed it to the genus Dimorphodon, but reported it was a distinct species, D. weintraubi (Fig. 1). D. weintraubi was closer in size to D. macryonx than to any known anurognathid. It wasn’t until the discovery of the IVPP embryo that another anurognathid similar in size to D. weintraubi was known.

Figure 2. Dimorphodon macronyx and D. weintraubi, an anurognathid larger than its namesake, both to scale. No phylogenetic analysis was undertaken by Clark et al. (1994, 1998) perhaps because no anurognathids of this size were known at that time.

Figure 3. Basal pterosaurs, including Dimorphodon macryonx and Dimorphodon weintraubi, separated by several genera. Click to see entire pterosaur tree.

The Phylogenetic Question
The problem is, there are several other pterosaur genera between the two when both are included in a large phylogenetic analysis (Fig. 2) not considered by Clark et al. (1994, 1998).

The Visible Distinctions
D. weintraubi was overall more robust. The coracoid did not have an expanded ventral process. The humerus was straighter. Metacarpal 4 was relatively closer in width to the other three. Manual 4.1 was relatively longer, closer to the elbow when folded. Manual 4.4 was longer. The metatarsus was relatively longer. Pedal digit 4 was shorter than 3. Pedal 5.1 did not extend beyond metatarsal 4.

The Invisible Distinctions
Because D. weintraubi nests (Fig. 2) after the more complete IVPP embryo (which would have grown up to be larger than D. weintraubi assuming a standard 8x increase, Fig. 3), phylogenetic bracketing permits us to assume certain traits in D. weintraubi that were not preserved in the fossil. The skull was likely shorter and wider, more like that of sister anurognathids, including Dendrorhynchoides, and the tail was likely much shorter and more gracile than in the holotype of Dimorphodon.

Figure 4. Click to enlarge. The Anurognathidae to scale.

The Digitigrade Question
This uncrushed specimen helped Clark, et al. (1998) determine that the basal pterosaur pes was incapable of a digitigrade configuration because the flat metatarsophalangeal joints did not permit the sort of extension seen in birds, as Padian (1983) had promoted for Dimorphodon macryonx. This is true. However, sufficient elevation of the posterior pes was permitted by the sort of extension of the interphalangeal joints seen in bipedal lizards, including the tritosaur fenestrasaur lizard, Cosesaurus,  (Peters 2000). The ichnite Rotodactylus preserves just this sort of proximal phalangeal elevation. Clark et al. (1994) did not consider this possibility. They folded digit V OVER the foot, which is bizarre but preserved (probably by taphonomic accident) in the specimen.  Their interpretation of a horizontal backbone while quadrupedal gait produces a forelimb in which the hand plants and lifts anterior to the elbow and shoulder, which produces no thrust, only braking. Digitigrady in some pterosaurs, plantigrady in others with an elevated backbone was discussed 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
Casamiquela RM 1962. Sobre la pisada de un presunto sauria aberrante en el Liassico del Neuquen (Patagonia). Ameghiniana 2, 10:183-186.
Clark J, Montellano M, Hopson J and Fastovsky D. 1994. In: Fraser, N. & H.-D Sues, Eds. 1994. In the Shadows of Dinosaurs. New York, Cambridge: 295-302.
Clark J, Hopson J, Hernandez R, Fastovsk D and Montellano M. 1998. Foot posture in a primitive pterosaur. Nature 391:886-889.
Padian K 1983. Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Museum, Postilla, 189: 1-44.
Peters D 2000. Description and Interpretation of Interphalangeal Lines in Tetrapods. – Ichnos 7(1): 11-41.

wiki/Dimorphodon