The Protodinosauria and the Origin of the Dinosauria

Update on January 17, 2019 with a new Figure 2

The large reptile tree recovers the following taxa at the base of the Archosauria leading toward the Dinosauria (Fig. 1). This is an update of prior posts on dinosaur origins with PVL 4597 moving to the last common ancestor of all Archosauria.

  1. Turfanosuchus
  2. PVL 4597 (the Tucuman specimen attributed to Gracilisuchus)
  3. Pseudhesperosuchus, Carnufex and Junggarsuchus, all crocs.
  4. Herrerasaurus.

Not part of the dino lineage,
pterosaurs and Lagerpeton nest elsewhere. Marasuchus, which often nests outside the Dinosauria in other trees, nests with a few other odd theropods here.

Here crocs and dinos have a last common ancestor
(Fig. 1) close to PVL 4597 in the Middle Triassic. Both started small and bipedal. Crocs had a wider skull. Dinos had a narrower skull. The reduction of the calcaneal tuber occurred in parallel. The tuber redeveloped in extant crocs.

Figure 2. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.

Figure 2. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.

Figure 5. Family tree of the Archosauria and basal Dinosauria. Bootstrap scores are shown.

Figure 3. Family tree of the Archosauria and basal Dinosauria. Bootstrap scores are shown. This is an old subset of the LRT. See the LRT for updated version.

Prior to these taxa
are larger forms, including Decuriasuchus and the basal poposaur, Turfanosuchus. So once again, phylogenetic miniaturization is key to the origin of both crocs and dinos (together, the Archosauria).

Wikipedia reports,
Paleontologists think that Eoraptor (Fig. 2) resembles the common ancestor of all dinosaurs;[ if this is true, its traits suggest that the first dinosaurs were small, bipedal predators. The discovery of primitive, dinosaur-like ornithodirans such as Marasuchus and Lagerpeton in Argentinian Middle Triassic strata supports this view; analysis of recovered fossils suggests that these animals were indeed small, bipedal predators. Dinosaurs may have appeared as early as 243 million years ago, as evidenced by remains of the genus Nyasasaurus from that period, though known fossils of these animals are too fragmentary to tell if they are dinosaurs or very close dinosaurian relatives.”

Too bad they are so tentative at Wikipedia
when the LRT lays it out pretty clearly. The purported and popular clade, “Ornithodira,” is not supported by the LRT.

References
Benton MJ and Clark JM 1988. Archosaur phylogeny and the relationships of the Crocodilia in MJ Benton (ed.), The Phylogeny and Classification of the Tetrapods 1: 295-338. Oxford, The Systematics Association.
Bittencourt JS, Arcucci AB, Maricano CA and Langer MC 2014. Osteology of the Middle Triassic archosaur Lewisuchus admixtus Romer (Chañares Formation, Argentina) its inclusivity, and relationships amongst early dinosauromorphs. Journal of Systematic Palaeontology. Published online: 31 Mar 201. DOI:10.1080/14772019.2013.878758
Bonaparte JF 1982. Classification of the Thecodontia. Geobios Mem. Spec. 6, 99-112
Bonaparte JF 1969. Dos nuevos “faunas” de reptiles triásicos de Argentina. Gondwana Stratigraphy. Paris: UNESCO. pp. 283–306.
Clark JM, Sues H-D and Berman DS 2000. A new specimen of Hesperosuchus agilis from the Upper Triassic of New Mexico and the interrelationships of basal crocodylomorph archosaurs. Journal of Vertebrate Paleontology 20(4):683-704.
Clark JM et al. 2000. A new specimen of Hesperosuchus agilis from the Upper Triassic of New Mexico and the interrelationships of basal crocodylomorph archosaurs. Journal of Vertebrate Paleontology 20 (4): 683–704. doi:10.1671/0272-4634(2000)020[0683:ANSOHA]2.0.CO;2.
Clark JM, Xu X, Forster CA and Wang Y 2004. A Middle Jurassic ‘sphenosuchian’ from China and the origin of the crocodilian skull. Nature 430:1021-1024.
Juul L 1994. The phylogeny of basal archosaurs. Palaeontographica africana 1994: 1-38.
Lecuona A and Desojo, JB 2011. Hind limb osteology of Gracilisuchus stipanicicorum(Archosauria: Pseudosuchia). Earth and Environmental Science Transactions of the Royal Society of Edinburgh 102 (2): 105–128.
Nesbitt SJ. et al. 2010. Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira. Nature 464(7285):95-8
Parrish JM 1993. Phylogeny of the Crocodylotarsi, with reference to archosaurian and crurotarsan monophyly. Journal of Vertebrate Paleontology 13(3):287-308.
Reig, OA 1963. La presencia de dinosaurios saurisquios en los “Estratos de Ischigualasto” (Mesotriásico Superior) de las provincias de San Juan y La Rioja (República Argentina). Ameghiniana 3: 3-20.
Romer AS 1972. The Chañares (Argentina) Triassic reptile fauna. An early ornithosuchid pseudosuchian, Gracilisuchus stipanicicorum, gen. et sp. nov. Breviora 389:1-24.
Romer AS 1972. The Chañares (Argentina) Triassic reptile fauna; XIV, Lewisuchusadmixtus, gen. et sp. nov., a further thecodont from the Chañares beds. Breviora 390:1-13

wiki/Gracilisuchus
wiki/Lewisuchus
wiki/Pseudhesperosuchus
wiki/Trialestes

Ticinosuchus and the aetosaurs, redux

Except for
the skull of Ticinosuchus ferox (Krebs 1965; Middle Triassic, ~ 230 mya, ~3 m in length), I have been using the traditional Krebs reconstruction for the post-crania. Here (Fig.1 ) I finally present my own tracing and reconstruction of Ticinosuchus.

Figure 1. Aetosaurus, Stagonlepis and Ticinosuchus shown together to scale. Ticinosuchus is the basalmost taxon in this clade, unrecognized by other cladograms. Perhaps this is due to differences in skull reconstructions.

Figure 1. Aetosaurus, Stagonlepis and Ticinosuchus shown together to scale. Ticinosuchus is the basalmost taxon in this clade, unrecognized by other cladograms. Perhaps this is due to differences in skull reconstructions. Note the phylogenetic miniaturization at the origin with Aetosaurus.

The morphological differences
between the Krebs and present reconstructions are few. However the posture here (Fig. 1) is a little more sacrum high, based on the long robust hind limbs, as also seen in Stagonolepis (Fig.1). Earlier we looked at the sharp premaxilla in Ticinosuchus that was previously overlooked by all workers. It’s a key trait shared with aetosaurs (Fig. 2).

Figure 2. Aetosaur skulls compared to Ticinosuchus, the long-sought outgroup to this clade.

Figure 2. Aetosaur skulls compared to Ticinosuchus, the long-sought outgroup to this clade.

Historical Notes from Nesbitt 2011
“Krebs (1963, 1965) argued that Ticinosuchus and Rauisuchus were more closely related to crocodylians than to any other group—a view that was opposed by various workers (e.g., Hughes, 1963; Romer, 1966, 1972b; Bonaparte, 1982) who thought that rauisuchids were proterosuchians.”

“Bonaparte (1981, 1984), placed Rauisuchus, Fasolasuchus, Prestosuchus, Saurosuchus, Ticinosuchus and various other fragmentary forms into Rauisuchidae.”

Nesbit 2011
identified the angular premaxilla as a questionable lacrimal. No reconstruction was offered to support this arrangement. He nested Ticinosuchus in a polygamy with a wide range of taxa including Revuletosaurus + Aetosauria, Turfanosuchus, Gracilisuchus, Qianosuchus and Prestosuchus.

Revueltosaurus?
Nesbitt 2011 nested Revueltosaurus at the base of the aetosaurs. The large reptile tree nests Revueltosaurus with Tasmaniosaurus and Fugusuchus (Fig. 3), altogether a sister clade to the Erythrosuchia and not far from Euparkeria. Revueltosaurus has a round premaxilla.

Figure 1. Revueltosaurus compared to its big sister, Fugusuchus, a basal erythrosuchid.

Figure 3. Revueltosaurus compared to its big sister, Fugusuchus, a basal erythrosuchid.

 

References
Krebs B 1965. Ticinosuchus ferox nov. gen. nov. sp. Ein neuer Pseudosuchier aus der Trias des Monte San Giorgio. Schweizerische Palaontologische Abhandlungen 81:1-140.
Lautenschlager S and Desojo JB 2011. Reassessment of the Middle Triassic rauisuchian archosaurs Ticinosuchus ferox and Stagonosuchus nyassicus. Paläontologische Zeitschrift Online First DOI: 10.1007/s12542-011-0105-1
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.

wiki/Ticinosuchus

 

Convergent Evolution Among Reptiles – part 2

Yesterday we looked at part 1 of convergence among reptiles. Today we’ll add a few other examples from the large reptile tree.

Silesaurus and dinosaurs: Both developed a bipedal configuration without a calcaneal tuber. All other poposaurs have a tuber. In addition, ornithischian dinos shared a predentary with Silesaurus.

Legless lizards: snakes, legless skinks, legless geckos. It is widely known that these squamate taxa all lose their limbs independently. The origin of snakes  was last covered here with Tetrapodophis.

Finbacks: Spinosaurs, sphenacodonts, Lotosaurus, Arizonasaurus.These diverse taxa all have elongate dorsal spines creating a tall back fin.

Procolophonids and pareiasaurs: These unrelated taxa, Hypsognathus and Anthodon, both developed spiky laterally expanded cheek bones (quadratojugals).

Tetraceratops and basal therapsids: Both of these taxa had enlarged canines and many paleontologists consider Tetraceratops a basal therapsid. According to the large reptile tree, Tetraceratops is related to Tseajaia, which also has smaller canine teeth.

Trioceros and Triceratops: Both of these unrelated taxa developed three facial horns. Trioceros is a chameleon. Triceratops is a dinosaur.

Four clades of pterodactyloid-grade pterosaurs and two other demi-pterodactyloid pterosaurs: Various basal pterosaurs developed pterodactyloid-grade traits. Two dorygnathid taxa evolved into azhdarchids and ctenochasmatids. Two scaphognathid taxa evolved into cycnorhamphids + ornithocheirids and germanodactylids + pterodactyl ids. Wukongopterids developed some, but not all pterodactyloid-grade traits (they retain a long pedal digit 5 and long tail). Anurognathids do likewise (but they retain separate nares and a long pedal digit 5).

Azhdarchid pterosaurs and eopteranodontid pterosaurs: Both of these unrelated clades developed medium to large stork-like forms.

Longisquama and Lemur: Both of these unrelated taxa (Fig. 1) had a small skull with large orbits on a short skull, a long dorsal series, an attenuated tail held aloft, shorter forelimbs and very long leaping hind limbs.

Figure 1. Longisquama (Triassic fenestrasaur) compared to a modern Lemur. Similar body shapes might imply similar locomotory patterns.

Figure 1. Longisquama (Triassic fenestrasaur) compared to a modern Lemur. Similar body shapes might imply similar locomotory patterns. Click to enlarge.

Cartorhynchus, ichthyosaurs, plesiosaurs, certain mosasaurs and sea turtles: Cartorhynchus had large, ichthyosaur-like/plesiosaur-like fore flippers, and small hind flippers, like living sea turtles, but is related to basal pachypleurosaurs, all of which had distinct fingers.

Multiple tooth rows: captorhinids and Azendohsaurus + Trilophosaurus + Rhynchosauria: Developed independently. these taxa had multiple tooth rows developed on the maxilla and palatine.

Hyper-elongate necks: tanystropheids (Fig. 2) and sauropods. Both of these independent clades are famous for their long necks.

Figure 1. Click to enlarge. Four large Tanystropheus specimens in situ and reconstructed. The man silhouette is 6 feet (1.8m) tall.

Figure 1. Click to enlarge. Four large Tanystropheus specimens in situ and reconstructed. The man silhouette is 6 feet (1.8m) tall.

Convergent Evolution Among Reptiles – part 1

Convergence in evolution/biology (aka homoplasy) is the independent evolution of similar features in species of different lineages.  Wiki examples include the evolution of flight in various tetrapods;  ichthyosaurs, dolphins and sharks

Here, as we shall see below,
are several reptile taxa converging with others. Unfortunately,
many of these honodairings are not recognized as examples of convergence among traditional paleontologists. Those scientists still lack their own large reptile tree to test relationships. The data deniers among them continue to avoid testing these touchy subjects despite  online publication several years ago.

  1. Tritosaurs and protorosaurs: Tritosaurs are a clade of lepidosaurs while protorosaurs are a clade basal to archosauriforms. Several tritosaurs, such as Tanystropheus, Macrocnemus, Cosesaurus, Langobardisaurus, Longisquama and pterosaurs have been (and still are in some circles) considered protorosaurs, like Protorosaurus and Prolacerta. The two clades do share a long list of traits developed in convergence, but the large reptile tree demonstrates their separation going back to basal amniotes. Tritosaurs have an ossified sternum and often an elongate p5.1 lacking in protorosaurs. Wiki reports, “Protorosaurs are distinguished by their long necks formed by elongated cervical vertebrae, which have ribs that extend backward to the vertebrae behind them. Protorosaurs also have a gap between the quadrate bones and the jugal bones in the back of the skull near the jaw joint, making their skulls resemble those of lizards. Whether or not protorosaurs represent a monophyletic group (i.e. a distinct evolutionary grouping within Archosauromorpha) is uncertain. Only recently has Protorosauria been defined in a phylogenetic sense as the most inclusive clade containing taxa such as ProtorosaurusMacrocnemus, and Tanystropheus.” Perhaps due to this convergence, protorosaurs in Wikipedia nest close to lepidosaurs and rhynchosaurs (see #2).
  2. Rhynchosaurs, trilophosaurs and protorosaurs: In like fashion, rhynchosaurs, like Mesosuchus, Rhynchosaurus and Hyperodapedon, have been traditionally allied with protorosaurus, but the large reptile tree demonstrates rhynchosaurs are derived from Rhynchocephalians (aka Sphenodotians) like Clevosaurus, with Trilophosaurus and Azendohsaurus related to the transitional taxa. Again, the last common ancestor was a basal amniote. At the rhynchocephalian/rhynchosaur transition neotony produced teeth with roots, rather than teeth fused to the jaws, as seen in basal rhynchocephalians.
  3. Caseasaurs and synapsids: Caseasaurs, like Cotylorhynchus have long been associated with basal synapsids, like Edaphosaurus. The large reptile tree nests caseasaurs with millerettids, like Australothyris and Acleistorhinus, both of which also have lateral temporal fenestra developed by convergence with synapsids.
  4. Turtles, armored placodonts and sinosaurosphargids: These three clades independently developed a carapace (shell) to cover the dorsal region of the postcrania. Turtles, like Meiolania, arose from pareiasaurs like Sclerosaurus. Armored placodonts like Placochelys and Henodus arose from Placodus. Sinosaurophargids, like Sinosaurosphargis, arose from unarmored Adelosaurus and Claudiosaurus.
  5. Champsosaurs, Parasuchians (phytosaurs) and Crocodiliformes (crocodilians): These three clades independently evolved a long low skull and a long slow body and tail. Parasuchians, like Parasuchus, had nostrils close to the eyes. Crocs, like Caiman, and champsosaurus, like Champsosaurus, had nostrils close to the tip of snout.
  6. Draco volans and prehistoric so-called rib gliders: Draco volans is a small lizard with enormous ribs able to open laterally for gliding. Similar, but different, is the clade of basal lepidosauriformes between Coelurosauravus and Xianglong that glide with enormous dermal extensions.
  7. More later.

And now a word from Carl Sagan (writing in the Demon Haunted World).
“Science has built-in error-correcting mechanisms—because science recognizes that scientists, like everybody else, are fallible, that we make mistakes, that we’re driven by the same prejudices as everybody else. There are no forbidden questions. Arguments from authority are worthless. Claims must be demonstrated. Ad hominem arguments—arguments about the personality of somebody who disagrees with you—are irrelevant; they can be sleazeballs and be right, and you can be a pillar of the community and be wrong.”

Unexpected centralia in the ichthyosaur, Chaohusaurus

A recent paper
by Montani et al. 2015 purported to indicate the presence of two centralia in the wrist of a juvenile basal ichthyosaur, Chaohusaurus (AGM CH-6628-22). It was not present in the adult. That, on its face of it is odd. The specimen, despite appearing to be undisturbed, lacked an ulna. That is also odd. Finally, no sister taxa have centralia. So the appearance here (Fig. 1) is triply odd.

Figure 1. Reinterpretation of Motani et al. 2015 showing how the purported radius could be a radius and ulna overlapping, the lateral centrale (lc) could be distal tarsals 3 and 4, and the medial centrale (mc) could be m4.2. Metacarpal "0" could be a part of the ulna. No sister taxa have centralia.

Figure 1. Reinterpretation of Motani et al. 2015 showing how the purported radius could be a radius and ulna overlapping, the lateral centrale (lc) could be distal tarsals 3 and 4, and the medial centrale (mc) could be m4.2. Metacarpal “0” could be a part of the ulna. No sister taxa have centralia. Click to enlarge.

Montani et al. report. 
“no amphibious sister taxa to ichthyopterygians have been discovered so far.”

Not so.
For the last four years the large reptile tree lists many sister taxa of increasing distance to the Ichthyopterygia, beginning with Wumengosaurus, basal mesosaurs and the several pachypleurosaurs that led to these taxa. The centralia is absent over several nodes prior to their appearance.

Centralia last appear
in Claudiosaurus, Adelosaurus, Sinosaurosphargis and Largocephalosaurus, but not thereafter. As the Enaliosauria becomes more aquatic, carpals are lost, beginning with the two centralia. Pachypleurosaurs do not have centralia. Neither do mesosaurs.

The (AGM CH-6628-22) specimen
of a juvenile Chaohusaurus that Motani et al. believe to have centralia (Fig. 1) has widely spaced and largely cartilaginous (poorly ossified) elements, some of which, like the ulnare and radiale are clearly disturbed from their in vivo placements. There is a long bone they label the lateral centrale and a short bone they label a medial centrale where such bones belong and this is the basis for their claim. There is even a medial metacarpal “0”, which anchors a sixth medial digit in the related Hupehsuchus, but is not known in Chaohusaurus, which is not a basal ichthyosaur.

We saw a similar reappearance
of digit “0” in Limusaurus, a theropod with embryonic hands retained into adulthood. Claudiosaurus, Adelosaurus and Sinosaurosphargis have a pisiform lateral to the ulnare, but it is similar in size and shape to the ulnare. More derived enaliosaurs lack a pisiform along with the centralia.

The problem is,
the lateral centrale in the above named enaliosaurs is not elongated (double wide), as it is purported to be in the juvenile Chaohusaurus, but rounded and similar in size and shape to the medial centrale.

A solution:
In my experience with missing bones alongside extra bones the answer might be to reinterpret the extra bones as the missing bones, only displaced. Perhaps the ulna is not missing from the juvenile Chaohusaurus, but instead is resting partly atop the radius (Fig. 1) as it appears to do so with that white line dividing the pair. If so the ulna can be restored, but the medial part is damaged. Here the purported metacarpal “0” might be part of the ulna. That’s a guess. The lateral centrale might be distal tarsals 3 and 4, as in the adult “D” specimen (Fig. 1), double wide. The purported distal tarsal 4 then is reinterpreted as distal tarsal 2 here. The medial centrale is reinterpreted as m4.2, which is also missing. The new restoration more closely matches adult specimens and sister taxa. It would also be nice if somehow we could determine that more radius was hidden beneath that portion of the displaced ulna.

This is parsimony and phylogenetic bracketing at its best.
If correct, this scenario just requires you to accept that a certain amount of displacement occurred during taphonomy, as in our old friend, Sordes, the pterosaur. I have not seen the specimen. So, if correct, this is another example of DGS, digital graphic segregation, and an example of pulling more data out of a photograph than was pulled out with the specimen in hand.

References:
Motani R et al. 2015. New evidence of centralia in Ichthyopterygia reiterating bias from paedomorphic characters on marine reptile phylogenetic reconstruction. Journal of Vertebrate Paleontology. 6 pp.

Back to Vancleavea

Several years ago we looked at Vancleavea campi (Figs. 1,2 ), a Triassic aquatic reptile described by Nesbitt, et al. 2008 as an archosauriform nesting with Erythrosuchus, Euparkeria, Turfanosuchus and Doswellia (according to Wikipedia, based on published work listed above). Unfortunately, Vancleavea shares few traits with these archosauriforms. It has no antorbital fenestra, no upper temporal fenestra and no mandibular fenestra.

Figure 1. Vancleavea surrounded by purported sister taxa as figured by Nesbitt and Wikipedia. None of these taxa share more traits with Vancleavea than does Helveticosaurus, a taxon ignored since it was proposed here.

Figure 1. Vancleavea surrounded by purported sister taxa as figured by Nesbitt and Wikipedia. None of these taxa share more traits with Vancleavea than does Helveticosaurus, a taxon ignored since it was proposed here.

Not yet tested in academic publications,
the thalattosaur, Helveticosaurus, shares more traits with Vancleavea than 569 other tested taxa in the large reptile tree.

Figure 2. Vancleavea with its sister, Helveticosaurus.

Figure 2. Vancleavea with its sister, Helveticosaurus.

This counter argument
was made more than 4 years ago. To date no one else has supported or refuted the argument. Nevertheless, in the last four years Vancleavea has appeared in several cladograms without Helveticosaurus. Unfortunately this demonstrates that paleontologists are really not interested in its correct nesting node, but would rather just add new taxa to existing flawed analyses and cladograms. Testing prior work is not their strong suite. Discovery is.

Vancleavea campi  (Nesbitt et al. 2009) Late Triassic,~210 mya, ~1.2 meters in length, was originally considered a very weird archosauriform close to DoswelliaTurfanosuchusChanaresuchus and Erythrosuchus, but that’s because the authors did not compare it to Helveticosaurus with which Vanclevea shares more traits. It turns out that Vanclevea was a not-so-weird thalattosaur and a prime example of what happens when the gamut of the inclusion set is decided prior to the analysis. Vancleavea was the last in its lineage. Unlike other thalattosauriforms, Vancleavea was armored with a variety of ossified scales covering the body.

There must be dozens
of Vancleavea-like thalattosaurs yet to be discovered, judging by the variation present between it and Helveticosaurus. Even so, after adding hundreds of taxa to the large reptile tree, these two still nest together.

Not the only time a taxon’s correct nesting ignored.
These taxa are also traditionally incorrectly nested based on the results of the large reptile tree.

  1. Turtles
  2. Pterosaurs
  3. Fenestrasauria and Tritosauria
  4. Snakes
  5. Caseasauria
  6. Mesosauria
  7. Poposauria
  8. Rhynchosauria
  9. Synapsida
  10. Chilesaurus and Daemonosaurus
  11. Gephyrostegus
  12. Procolophon
  13. Cartorhynchus
  14. Youngina and Youngoides
  15. Xianglong
  16. Tetraceratops
  17. Eudibamus
  18. Doswellia
  19. Revuletosaurus
  20. Scleromochlus
  21. Pseudhesperosuchus
  22. Marasuchus
  23. Lagerpeton
  24. Ticinosuchus
  25. and whatever else I’ve forgotten to list here

References
Nesbitt SJ, Stocker MR, Small BJ and Downs A 2009. The osteology and relationships of Vancleavea campi (Reptilia: Archosauriformes). Zoological Journal of the Linnean Society 157 (4): 814–864. doi:10.1111/j.1096-3642.2009.00530.x.
Parker WG and Barton B 2008. New information on the Upper Triassic archosauriform Vancleavea campi based on new material from the Chinle Formation of Arizona. Palaeontologia Electronica 11 (3): 20p.

wiki/Vancleavea

Putting some meat (and membranes) on Nyctosaurus

Figure 1. The UNSM specimen of Nyctosaurus, the only one for which we are sure it had only three wing phalanges.

Figure 1. The UNSM specimen of Nyctosaurus, the only one for which we are sure it had only three wing phalanges.

The UNSM 93000 specimen of Nyctosaurus (Figs. 1-3), in the University of Nebraska State Museum, would have been complete and articulated, except for a small channel of erosion that cut through the skull and limbs before discovery. Nevertheless the post-crania is intact (Fig. 2) and a little cutting and pasting more or less reproduces the in vivo look of the specimen in dorsal view (my what big arms you have!).

So here it is.
Every 5 seconds the scene will change with 3 scenes total (including the blend). The hind limbs are in the flight position, acting like horizontal elevators on an airplane and like little wings able to provide lift for the hind limbs. The fuselage fillet is shown. Otherwise the wing finger and its trailing membrane (brahiopatagium) is stretched only between the wing tip and elbow with no hind limb connection. That makes a short chord wing, just like a sailplane.

Figure 1. Nyctosaurus GIF movie showing in situ and in vivo versions of the post-crania. Membranes (uropatagia and fuselage fillet) and muscles added.

Figure 2. Nyctosaurus GIF movie showing in situ and in vivo versions of the post-crania. Membranes (uropatagia and fuselage fillet) and muscles added. Note the axis of the femoral head is aligned with the axis of the acetabulum. Nyctosaurus has hind legs like those of Sharovipteryx. Note: only the deltopectoral crest of the right humerus is preserved and it was flipped during taphonomy.

This specimen of Nyctosaurus is the only one that had but three wing phalanges. Evidently none were lost distally as m4.4 is often curved in pterosaurs as it is here (Fig 3). Rather m4.2 and m4.3 appear to have fused into one long bone. No Nyctosaurus shows a shortening of either of these two bones, so one did not disappear. A tiny ungual completes the wingtip, by the way.

Standing model of Nyctosaurus by David Peters

Figure 3. Standing model of Nyctosauru based on UNSM 93000. This one did not have a crest.

In figure 2
note the length and shape of the posterior dorsal ribs. They don’t curve much. Nyctosaurus might have had more of a pancake-like (rather than sausage-like) posterior body to match its wide chest, as seen elsewhere in Sharovipteryx, Eudimorphodon and Jeholopterus. In UNSM 93000 the sternum remains buried.

On a side note:
For those interested in some VERY bizarre Nyctosaurus reconstructions by artists like Jaime Headden, Mark Witton, Matt Martyniuk and others, click the following links:

  1. Nyctosaurus-sebulbai
  2. nyctosaurus.png
  3. nyctosaurus_skeleton_crested.jpg
  4. pterosaur_quad_launching_by_gaffamondo-d7ve3di.jpg
  5. alternative_diagram_for_quadrupedal_launch_by_gaffamondo-d7xagyk.jpg
  6. Witton_crested_nyctosaurs_March_2009.jpg

Note:
the tall thin crests are NOT the bizarre aspect of these illustrations and sculptures. The crests, in some specimens only, are real (Fig. 4).

On the quad launch issue (see illustrations from the list above),
remember that no pterosaur ever impresses metacarpal 4 (the big one) into the substrate. The tiny fingers are all that are ever impressed. Furthermore, as noted earlier, the quad launch hypothesis has many problems solved by simply taking off like a bird does.

Not immediately apparent,
some of the above images by other artists also appear to abbreviate the big metacarpal 4 for artistic purposes.

Figure 5. The derived Nyctosaurus, KJ2 in a floating configuration using its long forelimbs as pontoons.

Figure 4. The derived Nyctosaurus, KJ2 in a floating configuration using its long forelimbs as pontoons. With hollow wing bones, this pterosaur might have floated a little higher on the surface, but it’s hard to judge with the weight of that big crest and skull pressing down. It is also easier to draw the forelimbs in this fashion, rather than out laterally, yet still folded, which would have been quite stable with those metacarpal pontoons, probably floating diagonally to laterally on the surface.

References
Brown GW 1978. Preliminary report on an articulated specimen of Pteranodon (Nyctosaurusgracilis. Proceedings of the Nebraska Academy of Science 88: 39.
Brown GW 1986. Reassessment of Nyctosaurus: new wings for an old pterosaur. Proceedings of the Nebraska Academy of Science 96: 47.

wiki/Nyctosaurus

Preview of Flugsaurier 2015: Portsmouth

Fllugsaurier – Porstmouth 2015
is scheduled for August 25-29, 2015. Flugsaurier is a gathering of pterosaur experts eager to discuss their latest finds and hypotheses every two-three years. The last Flugsaurier occurred in Brazil 2013, with pictures here.

The fourth circular
just arrived and iincludes symposium and poster session titles and presenters. Some interesting talks are scheduled. My comments follow selected topic titles.

Chris Bennett and Paul Penkalski:
Waves of bone deposition on the rostrum of Pteranodon
Good news that someone else recognizes this. Laminated bone is present in all pterosaurs, promininent in Pteranodon and other large pterosaurs. The jugal and nasal both extend anteriorly more than traditionally thought. And that ‘layer’ at the tip of the rostrum (and mandible) in Pteranodon is a tooth. Of course, ontogenetic growth is also a likely suspect for those waves of bone deposition, but we’ll see what they say. I’d be interested to see how precise the interpretive drawings are.

Niels Bonde and Maria E. C. Leal:
Pneumatization in the earliest pterosaurs.
And hopefully they will discuss the same in the pre-pterosaur fenestrasaurs, Cosesaurus, Sharovipteryx and Longisquama!

Breithaupt, B.H., Matthews, N.A., Connely, M.V. and V.L. Meyers:
Pterosaur terrestrial locomotion, pterosaur tracks, and photogrammetric ichnology of Pteraichnus and other ichnotaxa
But will they discuss the pedal without manus tracks featured in the pterosaur heresies and in Peters (2011)? Witton’s comments on pterosaur ichnites are a bad omen for this.

Brooks B. Britt, F. M. Dalla Vecchia, D. Chure, G. F. Englemann, M. Chambers C. M., Thelin and R. D. Scheetz:
A new Triassic pterosaur from interdunal desert deposits of the Nugget Sandstone (NW Utah, USA
This is good news.

Xin Cheng, Shunxing Jiang, Xiaolin Wang and Alexander W. A. Kellner:
A new anurognathid pterosaur (Pterosauria, Anurognathidae) with complete skull and long tail from the Jurassic of China.
This is good news. Click here, here and here to see other anurognathids with a long tail.

David W. E. Hone, X. Xu, S. Jiang and J. R. Hutchinson:
The return of the holotype of Noripterus (Young, 1973) – implications for dsungaripterid taxonomy and a possible digitigrade pterosaur.
Digitigrade pterosaurs? Like I demonstrated in Peters (2000, 2011)? OMG!! Everyone has hated this (despite the evidence, for 15 years… and glad to see Noripterus is being retained.

Shunxing Jiang, Xiaolin Wang and Yingxia Ma:
A new archaeopterodactyloid pterosaur from the Jiufotang Formation in west Liaoning, China.
This is good news. Unfortunately the clade is not monophyletic because it contains ctenochasmatids. Click here for pterosaur cladogram.

Mark P. Witton:
Flight performance and lifestyle of Dimorphodon macronyx
With Witton’s interpretation of deep chord wing membranes and a single uropatagium stretched between the legs, this is going to be a head-scratcher lacking a basis in valid restoration… unless he has become a narrow chord dual uropatagia advocate, as shown here and going back to Peters (1995, 2002).

Alexander W. A. Kellner:
Triassic pterosaurs and ontogeny
Kellner (2015) has already followed reptileevolution.com in showing that all known Triassic taxa are not juveniles, but distinct genera, which Kellner named. Kellner did so without a phylogenetic analysis. In a separate email I challenged/asked Kellner to name all the nameless tiny pterosaurs of the Solnhofen, all of which nest separately in the large pterosaur tree, which you can see here.

David M. Martill, Steven U. Vidovic and Helmut Tischlinger:
A new pterodactyloid pterosaur from the Santana Formation of north east Brazil<
This is good news.

Matthew A. McLain and Robert T. Bakker:
Pterosaurs from the uppermost Morrison Formation at Como Bluff, Wyoming: A possible dsungaripterid from the Jurassic-Cretaceous transition.
This is good news.

Steven U. Vidovic:
Characterizing pterosaurs: the quality of anatomical characters in cladistic analyses
Wish I could see this. But the real problem has been taxon exclusion of the tiny Solnhofen pterosaurs.

David M. Unwin and D. C. Deeming:
Growth rates and their constraints in pterosaurs.
Hopefully they will discuss isometry in ontogeny, not the traditional false allometry.

David M. Unwin:
Non-pterodactyloid monofenestratans – rewriting the evolutionary history of
pterosaurs.
Hopefully Unwin will have rewritten what he wrote in prior papers. If not this presentation will be bogus. Darwinopterus and kin (his basal monofenestratans) represent a dead end in pterosaur evolution as documented here and here.

Charlie A. Navarro, Tom Stubbs, Liz Martin-Silverstone and Emily Rayfield:
Evolution of pterosaur  feeding systems
Wish I could see this. Hopefully they will use a valid cladogram if they are going to discuss pterosaur evolution. One can be seen here.

Rodrigo V. Pêgas and Alexander W. A. Kellner:
Preliminary mandibular myological reconstruction of Thalassodromeus sethi (Pterodactyloidea: Tapejaridae)
Wish I could see this.

Matthew A. McLain, Brad Chase and Ryan Devlin:
Addition of footprints and thin sections to the online pterosaur database PteroTerra.
Wish I could see this. A database of pterosaur tracks has been published in Peters (2011).

Shunxing Jiang, Taissa Rodrigues, Xin Cheng, Yinxia Ma, Xiaolin Wang and Alexander W. A. Kellner:
Brief report of two new specimens of Istiodactylidae (Pterosauria, Pterodactyloidea) from the Cretaceous of China
This is good news.

Unfortunately, I am not attending Flugsaurier 2015
because the climate for my interpretations and hypotheses is still stormy despite showing my work online. On the flip side, I think some of the participants and conveners are still clinging to invalid ideas, as touched on above and otherwise sprinkled throughout this blog over the past four years. Things have to change first.

References
Kellner AWA 2015. Comments on Triassic pterosaurs with discussion about ontogeny and description of new taxa. Anais da Academia Brasileira de Ciências (2015) 87(2): (Annals of the Brazilian Academy of Sciences) Printed version ISSN 0001-3765 / Online version ISSN 1678-2690.
Peters, D. 1995. Wing shape in pterosaurs. Nature 374, 315-316.
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: 293-336.
Peters, D. 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. Historical Biology 15: 277-301.
Peters, D. 2007. The origin and radiation of the Pterosauria. Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27.
Peters, D. 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos 18(2):114-141.

A new jugal for Acleistorhinus

Earlier work by yours truly
on Acleistorhinus relied on drawings of the specimen (Fig. 3). Here (Fig. 1) a DGS tracing (colorizing skull bones) of photos from the original paper (Daly 1969) reveals a slightly new interpretation of the skull, and the jugal in particular.

Figure 1. Acleistorhinus skull with bones colorized (on left) along with reconstructions in dorsal and lateral view (on right). Note the distinct jugal restored here with two posterior processes arising from the postorbital process, as in Delorhynchus.

Figure 1. Acleistorhinus skull with bones colorized (on left) along with reconstructions in dorsal and lateral view (on right). Note the distinct jugal restored here with two posterior processes arising from the postorbital process, as in Delorhynchus. Click to enlarge. Note the holes in several skull bones. The middle posterior process of the jugal is broken in situ and overlying the lower posterior process. Essentially both Delorhynchus and Acleistorhinus had dual lateral temporal fenestrae.

Acleistorhinus pteroticus (Daly 1969) Early Permian, ~3.5 cm skull length was consiered by DeBraga (2001, 2003) and DeBraga Reisz (1996) to be a Parareptile related to Lanthanosuchus, which is a clear mismatch. Daly (1969) considered Acleistorhinus a procolophonid. Here, in the large reptile tree, Acleistorhinus is derived from a sister to the RC14 specimen of Milleretta, is a sister to Delorhynchus (below; Reisz, Macdougall  and Modesto 2014) and phylogenetically precedes the turtle-like (but not relatedEunotosaurus (Fig. 2).

Figure 2. Acleistorhinus compared to sister taxa, Delorhynchus and Eunotosaurus.

Figure 2. Acleistorhinus compared to sister taxa, Delorhynchus and Eunotosaurus.

The middle posterior process of the jugal in Acleistorhinus
is broken in situ and overlying the lower posterior process. Essentially both Delorhynchus and Acleistorhinus had dual lateral temporal fenestrae.

Since both Eunotosaurus and Milleretta 
had expanded ribs, it is likely that Acleistorhinus did so too. We do not know the post-crania at present.

Figure 3. The earlier attempt at reconstructing the skull of Acleistorhinus based on drawings in

Figure 3. The earlier attempt at reconstructing the skull of Acleistorhinus based on drawings in DeBraga and Reisz 1996. The interpretation of the temple region changes the most between this version and figure 1. No other taxa have such a temporal region, but the new interpretation resembles that of Delorhynchus. 

The new data
on Acleistorhinus did not change its placement in the large reptile tree. I did not have access to any of the specimens listed above. Even so, the new data further unites two taxa, Delorhynchus and Acleistorhinus, that had been earlier united by a suite of traits. Colorizing the bones greatly helps produce the reconstruction.

References
Daly E 1969. A new procolophonoid reptile from the Lower Permian of Oklahoma. Journal of Paleontology 43: 676-687.
DeBraga M 2001The postcranial anatomy of Procolophon (Parareptilia: Procolophonidae) and its implications for the origin of turtles. PhD thesis, University of Toronto.
DeBragra M 2003. The postcranial skeleton, phylogenetic position and probable lifestyle of the Early Triassic reptile Procolophon trigoniceps. Canadian Journal of Earth Sciences 40: 527-556.
DeBraga M and Reisz RR 1996. The Early Permian reptile Acleistorhinus pteroticus and its phylogenetic position. Journal of Vertebrate Paleontology 16(3): 384–395.
Reisz RR, Macdougall MJ and Modesto S 2014. A new species of the parareptile genus Delorhynchus, based on articulated skeletal remains from Richards Spur, Lower Permian of Oklahoma. Journal of Vertebrate Paleontology 34:1033–1043.

wiki/Acleistorhinus

Reconstruction from jumbled scraps: the squamate, Kuroyuriella

Figure 1. The skull of Kuroyuriella reconstructed from bone scraps (above), most of which are layered on top of one another. Not all elements are identified, but enough are to nest this taxon with Ophisaurus.

Figure 1. The skull of Kuroyuriella (represented by two specimens of different size) reconstructed from bone scraps (above), most of which are layered on top of one another. Not all elements are identified, but enough are known to score and nest this taxon with Ophisaurus.

When provided disarticulated scraps,
start with the easy bones, then fill in the gaps in the puzzle. Sometimes, as in Kuroyuriella mikikoi (Evans and Matsumoto 2015, Early Cretaceous), there are enough parts to more or less recreate the skull most similar (among tested taxa in the large reptile tree) to that of Ophisaurus and basal to Myrmecodaptria and CryptolacertaEvans and Matsumoto nested Kuroyuriella  between Huehuecuetzpalli and the suprageneric clade Rhynchocephalia, both well outside the Squamata.

From the online paper:
“Together, SBEI 1510 and SBEI 1608, as type and referred specimen, characterize Kuroyuriella mikikoi as a small lizard having paired frontals with deep subolfactory processes; a median parietal without a parietal foramen, with sculpture of low relief, and with lateral shelves that restricted the adductor muscle origins to the ventral surface; upper temporal fenestrae that were at least partially closed by expanded postorbitofrontals; an unsculptured maxilla with a strongly concave narial margin; a large flared prefrontal; and a slender, relatively small pterygoid. In the shallow lower jaw, the teeth are closely packed, cylindrical, and pleurodont with lingual replacement; a subdental ridge is present; the dentary bears a tapering coronoid process that braces the coronoid, and has a posterior extension with a curved free margin; the surangular, angular, and splenial are all present and the surangular is shallow; the adductor fossa is open but not expanded; and the articular surface is asymmetrical.

In order to explore the affinities of Kuroyuriella mikikoi, it was coded into the matrix of Gauthier et al. (2012), as extended by Longrich et al. (2012) (184 characters coded out of 622, 70.4% missing data),

The consistent placement of Kuroyuriella on the squamate stem is problematic and probably artifactual, but whether the weighted analysis is giving a more accurate placement is uncertain. Of the derived character states possessed by Kuroyuriella, 76 [1] (postorbital partly occludes upper temporal fenestra), 364 [1] (dentary coronoid process extends beyond level of coronoid apex), 367 [2] (coronoid process of dentary overlaps most of anterolateral surface of coronoid), and 369 [2] (dentary terminates well posterior to coronoid apex) provide some support for placement of Kuroyuriella on the stem of scincids, and 129 [1] (prefrontal extends to mid-orbit), 104 [1] (absence of parietal foramen) and 385 [1] (posterior mylohyoid foramen posterior to coronoid apex) would be consistent with that placement. However, given the considerable difference between the results using equal weighting and Implied Weighting, Kuroyuriella remains incertae sedis pending recovery of more complete material.”

Figure 2. Ophisaurus, the extant glass snake or legless lizard is close to Kuroyuriella in the large reptile tree.

Figure 2. Ophisaurus, the extant glass snake or legless lizard is close to Kuroyuriella in the large reptile tree.

Here
Ophisaurus (Fig. 2) and Kuroyuriella both nest will within the Squamata, not ouside. of it in the large reptile tree. Reconstruction of the skull helps to ‘see’ this lizard as it was. I can’t imagine how difficult it would be to do try to establish traits  with a jumble of disarticulated bones.

As you’ll see, I think the parietal foramen was present. The parietal may have had longer posterior processes, now broken off.

References
Evans SE and Matsumoto R 2015. An assemblage of lizards from the Early Cretaceous of Japan. Palaeontologia Electronica 18.2.36A: 1-36
palaeo-electronica.org/content/2015/1271-japanese-fossil-lizards
http://palaeo-electronica.org/content/2015/1271-japanese-fossil-lizards