Pterodactylus naris revisited

It can be difficult to see tiny details in certain skeletal materials. The pristine Pterodactylus skull may be an example of this with regards to the tiny naris in the rostrum. Here (Fig. 1) the rostrum is retouched, getting rid of the naris and smoothing out the rostral bone (mostly the maxilla). Every second the image will revert to the original. Perhaps this method will help some folks see the “imperfections” (the naris and anterior nasal) I’ve seen here. If the animation doesn’t change, double-click on it to create a new window, which will also enlarge the image.

Figure 1. Pterodactylus GIF animation. Click to enlarge and animate. Here one frame has been retouched to get rid of the naris and make the rostrum one continuous sheet of maxillary bone.

Figure 1. Pterodactylus GIF animation. Click to enlarge and animate. Here one frame has been retouched to get rid of the naris and make the rostrum one continuous sheet of maxillary bone.

 

Turtles are closer to archosaurs? Please confirm.

A new paper
claims turtles are closer to archosaurs based on miRNA molecules.

From the abstract:
“Understanding the phylogenetic position of crown turtles (Testudines) among amniotes has been a source of particular contention. Recentmorphological analyses suggest that turtles are sister to all other reptiles, whereas the vast majority of gene sequence analyses support turtles as being inside Diapsida, and usually as sister to crown Archosauria (birds and crocodilians). Previously, a study using miRNAs (miRNAs) placed turtles inside diapsids, but as sister to lepidosaurs (lizards and Sphenodon) rather than archosaurs. Here, we test this hypothesis with an expanded miRNA presence/absence dataset, and employ more rigorous criteria for miRNA annotation. Significantly, we find no support for a turtle + lepidosaur sister-relationship; instead, we recover strong support for turtles sharing a more recent common ancestor with archosaurs. We further test this result by analyzing a super-alignment of precursor miRNA sequences for every miRNA inferred to have been present in the most recent common ancestor of tetrapods. This analysis yields a topology that is fully congruent with our presence/absence analysis; our results are therefore in accordance with most gene sequence studies, providing strong, consilient molecular evidence from diverse independent datasets regarding the phylogenetic position of turtles.”

Turtles are diapsids?
Then take the next step: go find turtles among the diapsids. Show us the morphological sisters. Show us the turtle-like traits in one or more diapsids. If you can’t, then go back to the drawing board. And for that matter, which diapsids? There are two convergent diapsid lineages, because the entire Reptilia is diphyletic.

Turtles are closer to archosaurs?
Then take the next step: go find turtles among the archosaurs. Show us the morphological sisters. Show us the turtle-like traits in one or more archosaurs. If you can’t, then go back to the drawing board.

Something must be off withe the miRNA. 
The large reptile tree finds maximum parsimony with millerettids and pareiasaurs, and among them, an ignored taxon, Stephanospondylus. The Field et al. (2014) tree (Fig. 1) was unable to resolve turtles from chickens from alligators. That’s an embarrassing result that tells me there’s a red flag here. Perhaps the secondary losses that are noted in lepidosaurs and mammals also have story to tell. A stronger tree would have had fewer secondary losses. What that tells me is what turtles and archosaurs share may be plesiomorphic genes secondarily lost in lepidosaurs and mammals.

I know nothing about miRNA or cellular biochemistry. But I can read a chart. If I need a lesson here, please provide it. This can be a discussion, not a lecture.

Figure 1. From Field et al. Here the secondary losses )red triangles) appear to tell the tale.  With so many secondary losses among mammals and lepidosaurs, the three genes that link turles to archosaurs basally, and the others that link them within their nodes could be a secondarily lost in lepidosaurs and mammals. A stronger tree would have had fewer secondary losses.

Figure 1. From Field et al. Here the secondary losses )red triangles) appear to tell the tale. With so many secondary losses among mammals and lepidosaurs, the three genes that link turles to archosaurs basally, and the others that link them within their nodes could be a secondarily lost in lepidosaurs and mammals. A stronger tree would have had fewer secondary losses. Most telling, perhaps, is the lack of resolution between alligators, chickens and turtles. To me, that’s a red flag.

Reference
Field DJ, Gauthier JA, King BL, Pisani D, Lyson TR, and Peterson KJ 2014. Toward consilience in reptile phylogeny: miRNAs support an archosaur, not lepidosaur, affinity for turtles. Evolution & Development (advance online publication)
DOI: 10.1111/ede.12081 http://onlinelibrary.wiley.com/doi/10.1111/ede.12081/abstract

free pdf:
http://danieljfield.com/Home/Publications.html

http://news.yale.edu/2014/05/05/study-finds-turtles-are-closer-kin-birds-crocodiles-lizards-snakes

A near perfect, pristine Pterodactylus skull

Figure 1. Pterodactylus skull, privates collection,  from "Weber 2013 Paleoeocology of pterosaurs 3 : Solnhofen". French Paleontological survey "Fossiles".

Figure 1. Pterodactylus skull, privates collection, from “Weber 2013 Paleoeocology of pterosaurs 3 : Solnhofen”. French Paleontological survey “Fossiles”. Bones colorized below, both images flipped left to right. Black dots indicated fenestra. Anterior slit is secondary naris, which originated in Scaphognathus. Note the jugal and nasal extend to it. The premaxilla appears to have only three teeth, but look more closely and the nubbin-like medial tooth is still visible. Here you can also see the medial sheet bone in the anterior antorbital fenestra. It is not a fossa.

Luckily this specimen was buried before being crushed, so the cracking one sees in other fossils are absent here. Not sure what the rest of the specimen looks like. This privately owned and expertly prepared Pterodactylus specimen can be considered “pristine” and it offers uncluttered insights into the small pterosaur skull, including the tiny nares, the medial sheet dividing the anterior antorbital fenestra, the laminated jugal and nasal, and the nubbin of a medial pmx tooth. Thanks to Frédéric Weber for providing the image.

Figure 2. Closeup of the rostrum of this private Pterodactylus specimen with bone laminations identified.

Figure 2. Closeup of the rostrum of this private Pterodactylus specimen with bone laminations identified. Without other specimens, like Scaphognathus, that show the secondary naris developing, there would be more reason to dismiss these minor shapes as taphonomic cracks and such.

We don’t look at such imagery in a vacuum. Rather we note that this sort of morphology shows up first in Scaphognathus (Fig. 3) and is retained, more or less, in its many pterosaurian descendants.

Figure 3. New reconstruction of Scaphognathus with the new foot and wing phalanges added.

Figure 3. New reconstruction of Scaphognathus with the new foot and wing phalanges added.

Reference:
Image from “Frédéric Weber 2013 Paleoeocology of pterosaurs 3 : Solnhofen”. French Paleontological survey “Fossiles.”

Did Effigia have a postfrontal?

Applying color to the dorsal skull of Effigia appears to show unfused postfrontals (Fig. 1), a trait seen in archosaurs that are not crocs and not dinos (in other words: virtually all archosaurs). Very few basal crocs, like Gracilisuchus, retain an unfused postfrontal. Nesbitt (2007) did not identify a postfrontal but did identify an asymmetrical posterior nasal suture, which may not have been accurate.

Figure 1. Dorsal view of Effigia skull from Nesbitt 2007. At left postfrontals are identified. Bits of the broken nasals are also in that cranial area.

Figure 1. Dorsal view of Effigia skull from Nesbitt 2007. At left postfrontals are identified. Bits of the broken nasals are also in that cranial area.

Earlier the poposaurs, including Effigia, shifted their position on the large reptile tree to nest with Turfanosuchus, a basal poposaur, which also has a postfrontal. A postfrontal has been reported on Lotosaurus (Parrish 1993), but I haven’t seen a good dorsal view of the skull. Poposaur skulls, and poposaur cranial regions are quite rare. This is one of the few examples.

References
Nesbitt SJ and Norell MA 2006. Extreme convergence in the body plans of an early suchian (Archosauria) and ornithomimid dinosaurs (Theropoda). Proceedings of the Royal Society B 273:1045–1048. online
Nesbitt S 2007. The anatomy of Effigia okeeffeae (Archosauria, Suchia), theropod-like convergence, and the distribution of related taxa. Bulletin of the American Museum of Natural History, 302: 84 pp. online pdf
Parrish JM 1993. Phylogeny of the Crocodylotarsi, with reference to archosaurian and crurotarsan monophyly. Journal of Vertebrate Paleontology 13:287–308
Zhang F-K 1975. A new thecodont Lotosaurus, from Middle Triassic of Hunan. Vertebrata PalAsiatica 13:144-147.

AMNH Effigia webpage
wiki/Effigia

Banguela: a new pterosaur by a first-time author

Congratulations to Jaime Headden, who, along with Hebert Campos, had their discovery of Banguela oberlii, a toothless dsungaripterid NMSG SAO 251093, published. It’s a big jaw tip, producing an estimated skull length of 2 feet (60cm). That’s a bit more than a 50cm Dsungaripterus skull. Missing here is the jaw tip, which we learned earlier is a single tooth.

Figure 1. Banguela from several angles. Note the lack of teeth on this dsungaripterid.

Figure 1. Banguela from several angles. Note the lack of teeth on this dsungaripterid.

 

The Brazilian nickname ‘Banguela’ is commonly given to toothless people (Fig. 2), even though most retain a few teeth.

Figure 2. The original meaning of "Banguela", or what you'll find if you don't add the word "pterosaur" to your Google search.

Figure 2. The original meaning of “Banguela”, or what you’ll find if you don’t add the word “pterosaur” to your Google search.

JH mentioned, “An interesting rule of biology says when animals lose a feature, it cannot be regained. This is called Dollo’s Law, and it tells us about why birds don’t regrow teeth.”

Dollo’s Law needs to be brought up more often, like when pterosaurs are supposed to grow gigantic wing (4th) fingers from the vestiges most archosaurs have. Better to look for those sorts of fingers where they actually are, in the Lepidosauria.

JH reported, “Banguela oberlii is here hypothesized to be a derived dsungaripterid, though in our phylogenetic analysis (Headden & Campos, 2014) the new taxon was placed basal to other dsungaripterids. Further analysis supports a deeper nesting, but this work was not prepared at the time of publication.”

The large pterosaur tree nested dsungaripterids between toothy basal germanodactylids and toothless shenzoupterids and tapejarids, which is probably why Banguela initially nested basal, closer to other toothless clades.We also learned that basal taxa in virtually all pterosaur clades were tiny. So it is a good bet that big Banguela was a terminal, rather than a basal, taxon. There was a trend toward tooth loss in this clade of germanodactylia. Not surprising, but still wonderful, to see a “toothless” dsungaripterid. Any X-rays of those jaws planned?

References
Headden JA and Campos HBN 2014. An unusual edentulous pterosaur from the Early Cretaceous Romualdo Formation of Brazil. Historical Biology [Published online ahead of print]: 1-13. doi: 10.1080/08912963.2014.904302

More info online here at J. Headden’s blogpost.

 

 

 

 

Models for the Rise of the Dinosaurs – new paper, old ideas

Benton, Forth and Langer (2014) present a summary of current consensus regarding the origin of dinosaurs (Fig. 1).

Figure 1. The rise of the Dinosauria by Benton et al. 2014.

Figure 1. The rise of the Dinosauria by Benton et al. 2014. This is your standard tree with pterosaurs thrown in and rapid radiation at the base of clades. Crurotarsi includes crocs (archosaurs), so that makes pterosaurs and silesaurs archosaurs here.

From the abstract: Dinosaurs arose in the early Triassic in the aftermath of the greatest mass extinction ever and became hugely successful in the Mesozoic. Their initial diversification is a classic example of a large-scale macroevolutionary change. Diversifications at such deep-time scales can now be dissected, modelled and tested. New fossils suggest that dinosaurs originated early in the Middle Triassic, during the recovery of life from the devastating Permo-Triassic mass extinction. Improvements in stratigraphic dating and a new suite of morphometric and comparative evolutionary numerical methods now allow a forensic dissection of one of the greatest turnovers in the history of life. Such studies mark a move from the narrative to the analytical in macroevolutionary research, and they allow us to begin to answer the proposal of George Gaylord Simpson, to explore adaptive radiations using numerical methods.

Unfortunately this study includes pterosaurs and lagerpetids (Fig. 1), both unrelated to the origin of dinosaurs in the large reptile tree (Fig. 2). Pterosaurs nest with lepidosaurs. Lagerpeton nests with proterochampsids in the large reptile tree.

Putting specimens in phylogenetic order and chronological order has been done for decades. Following the lineage of basal taxa here, the origin of dinosaurs should follow this lineage: Thadeosaurus > Boreopricia > Youngina BPI 3859 > Younginoides UC 1528 > Proterosuchus > Fugusuchus > Garjainia > Euparkeria > Osmolskina > Vjushkovia > Arizonasaurus > Decuriasuchus> Turfanosuchus > SMNS 12591PVL 4597 > Trialestes > Herrerasaurus. Many of the above are definite splinters off the main line, but remain closer than any other known taxa to that undiscovered closer sister. There are also several rises and falls in overall body size in this list, so Cope’s Rule is not in effect here.

Figure 1. Click to enlarge. Nyasasaurus bones placed on an enlargement of Turfanosuchus, a middle Triassic basal archosaur, not a dinosaur. Dinos and crocs all started out as tiny bipeds.

Figure 2. Click to enlarge. Nyasasaurus bones placed on an enlargement of Turfanosuchus, a middle Triassic basal archosaur, not a dinosaur. Dinos and crocs all started out as tiny bipeds derived from a sister to Turfanosuchus.

Protorosaurs are basal diapsids that give rise to younginids and archosauriforms. They are known from Late Permian (Protorosaurus) to Middle Triassic (Pamelaria) sediments. In the second wave of dinosaur ancestors, the erythrosuchids and rauisuchids, preside with basal taxa in the early and middle Triassic. In the third wave of dinosaur ancestors we find basal archosaurs, like Decuriasuchus, Lewisuchus and Turfanosuchus. The latter gave rise to basal crocs, basal dinos and poposaurs. In the large reptile tree no taxa appear between basal crocs and basal dinos, so the term “archosaur” is restricted to them alone.

Nyasasaurus, once touted at perhaps the most basal dinosaur/dinosauriform, is more likely a big poposaur derived from Turfanosuchus (Fig. 1), from what I can tell from the sparse remains and it’s age.

Figure 2. Basal dinosaurs extend to the Middle Triassic to the present day. The origins of the more primitive clades are shown by arrows.

Figure 3. Basal dinosaurs extend from the Middle Triassic to the present day. The earliest appearances of the more primitive clades are shown by arrows.

When you find so many archosauriforms in the Early Triassic, one wonders if the origin of this clade occurred in the Late Permian, then found refuge in one corner of the globe during the Permo-Triassic extinction event, then radiated thereafter, leaving fossils in fossiliferous areas where and when these taxa were once again widespread and discoverable.

References
Benton MJ, Forth J and Langer MC 2014. Models for the Rise of the Dinosaurs. Current Biology 24:R87-R95.

Vertebrates of the Jurassic Dauhugou Biota of northeastern China – Sullivan et al. 2014

A new paper by Sullivan, et al. (2014) reviewed the current knowledge of the vertebrates of the Jurassic Dauhugou Biota of northeastern China. That list included several lepidosaurs and pterosaurs. Unfortunately their review included several calls for “more testing” to determine phylogenetic relationships. We’ll review those here.

1. Indeterminate Squamate A (IVPP V14386, Figs. 1, 2) was considered a juvenile (total length >9cm) distinct from Dalinghosaurus, but the authors lamented that insufficient morphological information was present to justify the erection of a new taxon.

Figure 1. IVPP-V14386 in situ from Sullivan et al. 2014. Here the scales cover most of the bones.

Figure 1. IVPP-V14386 in situ from Sullivan et al. 2014. Click to enlarge. Here the scales cover most of the bones.

Not sure why Sullivan et al. decided there was insufficient morphological evidence here. I found every major bone but some mid-vertebrae (Fig. 2). It was like looking at an X-ray! This IVPP specimen does indeed nest with Dalinghosaurus and Homoeosaurus at the base of the Tritosauria, a third clade of lizards that Sullivan et al. evidently don’t care to consider. And that may be the source of their confusion because this specimen doesn’t nest within the Squamata. Distinct from Dalinghosaurus, the IVPP specimen has a wider skull (based on the exposed palate), a shorter ventral pelvis, no anterior scapulocoracoid fenestration and several other distinct traits.

Figure 2. IVPP-V14386 with major bones colorized and skull reconstructed.

Figure 2. Click to enlarge. IVPP-V14386 with major bones colorized. Skull and pelvis reconstructed.

2. Indeterminate Squamate B (IVPP V13747) (total length > 12cm) was considered a possible scleroglossan. The large reptile tree found it (the Daohugou lizard in the large reptile tree) also nested with basal tritosaurs.

3. Jeholopterus ningchengensis (IVPP V12705) was correctly considered an adult and referred to the Anurognathidae. Sullivan et al. reported this specimen, “may represent the smallest known adult pterosaur.” This is far from true, and reflects antiquated thinking regarding ontogeny and bone fusion, along with a refusal to consider tiny Solnhofen pterosaurs adults themselves.

The referred specimen (CAGS-IG-02-81) was considered a juvenile by Sullivan et al. because some long bones were half as long.  Unfortunately no reconstructions were attempted. If the workers had only taken this step they would have realized immediately that these two specimens are not even congeneric. Their skulls are nearly the same size. Their post-crania differ greatly. The more gracile one attacked insects. The more robust one attacked dinosaurs for their blood.

Figure 3. Click to enlarge. The Jeholopterus holotype (left) alongside the referred specimen (right). No doubt they were related, but were likely not conspecific.

Figure 3. Click to enlarge. The Jeholopterus holotype (left) alongside the referred specimen (right). No doubt they were related, but were likely not conspecific. The one on the right was an insect eater. The one on the left was specialized for drinking dinosaur blood. Skull sizes are the same. The post-crania was more robust on the left with a palate designed to transmit face-banging forces to the rear.

4. Dendrorhynchoides mutoudengensis (originally GLGMV 0002, but now JZMP-04-07-3, but this is also the Boreopterus specimen number) was listed, but Sullivan et al. placed doubt on the referral of this specimen to this Dendrorhynchoides. And for good reason! The referred specimen (Fig. 4) nests with the flathead pterosaur, SMNS 811928, both derived from the holotype of Dendrorhynchoides (Fig. 4). Note the tail is even longer on the holotype as we noted before.

The holotype of Dendrorhynchoides

Figure 4. Click to enlarge. (Left) The holotype of Dendrorhynchoides compared to (right) the referred specimen. The latter actually nests with the flat-head pterosaur and the two nest alongside Dendrorhynchoides, so, not far off. Sullivan et al. made a big deal about the long tail in the referred specimen, but the holotype has a longer tail and is more primitive. Lack of careful observation and a refusal to create reconstructions is a common problem among pterosaur workers.

5. Fenghuangopterus lii (CYGB-0037) was considered small, but with an unclear ontogenetic stage. It was originally considered a scaphognathine, but the large pterosaur tree nests it as a long-legged, basal dorygnathid, so not too far from Scaphognathus.

6. Jianchangopterus zhaoianus (YHK-0931) was originally considered small, but a subadult scaphognathine related to Sordes. By contrast, Sullivan et al. wrote “it represents a very young individual.” and it’s relation to other pterosaurs “requires testing.” I have done that testing and this small adult specimen nests between Ningchengopterus and the new Painten pterosaur, all at the base of the genus clade, Pterodactylus. Here  (Fig. 5) all three are compared to Sordes.

Figure x. When you compare the three specimens of Sordes to the three jianchangopterids the purported similarities to Sordes start to fade. Shifting Jianchangopterus to Sordes adds 40 steps.

Figure 5. When you compare the three specimens of Sordes to the three jianchangopterids the purported similarities to Sordes start to fade. Shifting Jianchangopterus to Sordes adds 40 steps.

7. Qinlongopterus guoi (D3080, D3081) was considered a young juvenile very similar to Rhamphorhynchus due to its small size, large orbit and short rostrum. The large pterosaur tree nests it within that genus, close to other small rhamphs. Hone et al. (2012) noted that “juveniles of different pterosaur taxa are harder to distinguish than adults.” That may be so because Hone et al. does not care to test these small pterosaurs in phylogenetic analysis. If they took this little step they would find that, like Zhejiangopterus, Pteranodon and pterosaur embryos, which are identical to adults and can be scored with adults in phylogenetic analysis. In similar fashion Hone deleted fenestrasaurs when he and Benton wrote two papers supporting the archosaur origin for pterosaurs (without providing a viable archosaur candidate with pterosaur traits).

8. Changchengopterus pani (CYGB-0036) was considered a young juvenile by Sullivan et al. but it nests with other small pterosaurs, like the BSP 1994 specimen of Eudimorphodon at the base of all higher single cusp tooth pterosaurs. The referred specimen is a wukongopterid, as Wang (2010) erroneously suggested for the holotype. Sullivan et al. considered the phylogenetic position of these two specimens uncertain. They considered the holotype “one of the smallest pterosaurs specimens known” and considered it a juvenile due to its unfused scapulocoracoid, not realizing that this trait is phylogenetic in distribution, not ontogenetic.

9. Darwinopterus, Wukongopterus, Kunpengopterus, Archaeoistiodactylus are here all lumped together because they all form a clade, the Wukongopteridae, that left no descendants, but developed a long pterodactyloid rostrum and neck by convergence. Unfortunatelly Sullivan et al. followed Lü et al. in supporting their analysis that placed Darwinopterus at a transitional node from long tail rhamphs to short tail pterodcs. Of course the lack of resolution at this node was massive, with no single genus preceding or succeeding Darwinopterus. Nor did Lü et al include the actual transitional taxa, the tiny pterosaurs, which they considered juveniles unworthy or potentially disruptive of analysis. A more inclusive analysis can be seen here. To the credit of Sullivan et al. followed Martill and Etches (2013) and the pterosaurheresies and reptile evolution to break with the original nesting of Archaeoistiodactylus with the ornithocheirid Istiodactylus to suggest (without phylogenetic analysis) that it nested with wukongopterids.

References
Martill DM and Etches S2013. A new monofenestratan pterosaur from the Kimmeridge Clay Formation (Upper Jurassic, Kimmeridgian) of Dorset, England. Acta Palaeontologica Polonica 58 (2): 285–294. doi:10.4202/app.2011.0071.
Sullivan C, Wang Y, Hone DEW, Wanga Y, Xu X and Zhang F 2014. The vertebrates of the Jurassic Daohugou Biota of northeastern China. Journal of Vertebrate Paleontology 34(2):243-280.