Archosauria: Watch out how you use this taxon!

According to EvoWikiArchosauria (Cope 1869 emended by Gauthier 1984 “ruling reptiles”) sensu stricto, or sensu Gauthier, is the crown clade of Archosauromorpha and is defined as “the common ancestor of birds and crocodiles and all descendants thereof.

In older, traditional smaller reptile trees, pterosaurs are included in the Archosauria as they were once, and are still traditionally considered close to dinosaurs, despite the fact that the two share very few traits. No series of taxa within or just outside the Archosauria demonstrate a gradual accumulation of pterosaurian traits. Rather, that gradual accumulation of traits is found in a series of now extinct tritosaur lizards, once and traditionally mistakenly considered prolacertiformes or protorosaurs.

Figure 1. Segment of the large reptile tree showing the Euarchosauriformes. The Archosauria is highlighted at the bottom.

Figure 1. Segment of the large reptile tree showing the Euarchosauriformes. The Archosauria is highlighted at the bottom.

The large reptile tree (Fig. 1) demonstrates that the outgroup for the dinosaurs (including birds) is the crocodylomorpha. So birds and crocs share last common ancestor around Turfanosuchus and Decuriasuchus. So the Archosauria is now restricted to just the Crocodylomorpha and the Dinosauria and the smaller clades and taxa they include. Note the basal placement of rauisuchoids preceding the archosauria.

Because prior studies did not include so many basal taxa, they included many additional ‘by default’ mismatches nesting between crocs and dinos. Let’s have a look at them.

 A tree recovered from Gauthier 1986

Figure 2. A tree recovered from Gauthier 1986 (form Wiki) Pararchosauriformes are in green boxes. Pterosaurs are included within Ornithodira. Crocs and dinos here are greatly separated, so all basal forms back to a last common ancestor are included within the Archosauria.

Gauthier 1986
This very early smaller study included Proterochampsidae and Parasuchia, two suprageneric clades now known to nest outside the Euarchosauriformes when more taxa, like various Youngina and Choristodera, are included. It also employed suprageneric taxa instead of generic taxa (which always invites trouble), and certainly two few taxa to demonstrate a gradual accumulation of traits in derived forms. Gauthier employs the Ornithodira, which includes pterosaurs. Not sure how you would score such a taxon, with wings or without?

The Archosauria according to Sereno 1991 from Wiki.

Figure 3. The Archosauria according to Sereno 1991 from Wiki. Light red arrows shows that crocs and dinos are still far apart here.

Sereno 1991
Five years later, but still early in the world of PAUP, Sereno (1991) moves Euparkeria outside of the Archosauria. Crocs nest within Suchia here. Ornithodira is divided into three clades. Pterosauria is highlighted because it doesn’t belong here, but in lizards (not employed). As in Gauthier (1986) Proterochampsidae and Parasuchia are also not correctly nested within these Euarchosauriformes, but nest here by default.

Benton 2004 diagrams the Archosauria.

Figure 4. Benton 2004 diagrams the Archosauria but includes two lepidosauromorphs and separates the crocs into three widely divided clades.  Lagerpeton is more closely related to Proterochampsidae than dinos when Tropidosuchus is employed, which is not the case here. Clearly there needed to be more attention paid to basal crocodylomorphs that nest in three widely varied nodes here. Suprageneric taxa, like Crocodylomorpha, are probably the cause of the problem.

Benton 2004
Thirteen years later, and four years after Peters (2000), Benton (2004, Fig. 4) expanded on earlier studies, still employing suprageneric taxa, but moving towards employing more generic taxa. The topology was largely the same, though, as in prior studies (Figs. 2, 3). Yes, unbelievably, that’s  Hyperdapedon as a basal taxon.

Archosauria according to Brusatte 2010. Various clades found in the large reptile tree are identified by color boxes.

Figure 5. Archosauria according to Brusatte 2010. Various clades found in the large reptile tree are identified by color boxes. Yes, there appear to be problems here as compared to the large reptile tree results. 

Brusatte et al. 2010
Six years later, and a full ten years after Peters (2000), Brusatte et al. (2010) employed still more generic taxa, keeping Pterosauria and Phytosauria but dropping Proterochampsidae. Here Gracilisuchus and Erpetosuchus correctly nested with Crocodylomorpha, but Scleromochlus did not. Taxa found to nest as poposaurids in the large reptile tree are divided, unresolved and widely separated here. Note that no taxa are shown to be basal to the Archosauria (which is always a problem!) and the basal taxa in each branch (Scleromochlus, Pterosauria, Phytosauria (=Parasuchia) and Aetosauria do not resemble one another — but they should if they truly reflect and model actual evolutionary paths.

Only the large reptile tree provides the gradual accumulation of traits in all derived taxa from more primitive taxa. So when you talk about archosaurs, it would be a good idea to restrict your discussion to crocs and dinos, which by definition, make up this clade. Keep the poposaurs within the Dinosauria. The others are all outliers.

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
Brusatte SL , Benton MJ , Desojo JB and Langer MC 2010. The higher-level phylogeny of Archosauria (Tetrapoda: Diapsida), Journal of Systematic Palaeontology, 8:1, 3-47.
Cope ED 1869.
Synopsis of the extinct Batrachia, Reptilia and Aves of North America. Transactions of the America Philosophical Society 14: 1–252.
Gauthier J1984. A cladistic analysis of the higher systematic categories of the Diapsida. [dissertation]. Available from University Microfilms International, Ann Arbor, #85-12825, vii + 564 pp.
Gauthier J 1986. Saurischian monophyly and the origin of birds. Memoirs of the California Academy of Sciences 8: 1-55.
Sereno PC 1991. Basal archosaurs: phylogenetic relationships and functional implications. J Vert Paleo 11 (Supp) Mem 2: 1–53.

Avesuchia and Avemetatarsalia: Avoid these taxa!

Earlier we looked at another widely used and accepted taxon, the Ornithodira (dinosaurs + pterosaurs and sometimes Scleromochlus), that turns out to be diphyletic according to the large reptile tree, or at least redundant with Amniota (= Reptilia) and therefore should be avoided. Today we’ll look at two taxa proposed by Benton (1999) in his study of Scleromochlus, in which he and I tilt the unseen quadrate different ways.

Avemetatarsalia 
Benton (1999) defined Avemetatarsalia as all “avesuchians/crown-group archosaurs” closer to Dinosauria than to Crocodylia. After review in the large reptile tree that definition is now redundant with Dinosauria since no taxon is closer to Dinosauria than Crocodylomorpha. Avemetatarsalia was meant to include Scleromochlus + pterosaurs + dinosauromorphs, but here that clade is paraphyletic (or redundant with Reptilia) because pterosaurs are on the new lepidosauromorph branch while dinosaurs and Scleromochlus are on the new archosauromorph branch These branches divided during the earliest Carboniferous at its very base. If pterosaurs were removed from this definition, the resulting inclusion set would be redundant with Archosauria (crocs + dinos).

Avesuchia 
Benton (1999) defined “Avesuchia/crown-group Archosauria” as the taxon comprising “Avemetatarsalia” and “Crurotarsi” (and sister taxa of “Crurotarsi” that are closer to Crocodylia than to Aves), and all their descendants. Because the definition included parasuchians, pterosaurs and Lagerpetonhere this creates a paraphyletic clade redundant with Reptilia for the same reasons listed above. If pterosaurs were removed from this definition, the resulting inclusion set would be redundant with Archosauriformes.

I realize this is heretical thinking, but it reflects recovered results after testing the hypothesis, which is what Science is all about. Wish others would test this hypothesis with equal rigor.

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
Benton MJ 1999. Scleromochlus taylori and the origin of dinosaurs and pterosaurs. Philosophical Transactions of the Royal Society of London B 354: 1423-1446.

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.

From Nesbitt and HONE 2010, a purported antorbital fossa in Dimorphodon. Note where it is. This strut support is a little thinner and therefore a little deeper than the rest of the ascending process. Dimorphodon depresses this area more than other pterosaurs.

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.

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.

Raeticodactylus skull. Nesbitt and Hone (2010) say the red areas represent the antorbital fossa.

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

Ornithodira: Avoid this taxon!

One core and basis of the Pterosaur Heresies blog is to demonstrate that, how and why pterosaurs have nothing in common with dinosaurs or their precursors, despite reams of traditional literature promoting that relationship. For example:

“Pterosaurs and dinosaurs have been grouped together for along time, and today, the prevalent view among vertebrate paleontologists is still that they do indeed form a natural group of animals.” — Nick Fraser (2006) in “Dawn of the Dinosaurs.”

If this false paradigm continues another two years that will complete a full three decades of belief in the official, “Ornithodira,” the clade THEY say includes both pterosaurs and dinosaurs. I say ‘belief’ because there’s absolutely no evidence for this relationship — as traditional paleontologists themselves have noted (see below).

“Pterosaurs appear suddenly in the fossil record and in full possession of all their highly derived characters…” — David Hone and Michael Benton (2007, 2008).

“As Figure 4.3 illustrates, paleontologists don’t really know where this group should sit within the diapsid family tree. The reason for this is simple — a complete lack of protopterosaurs that might link this group to other diapsids.” — David Unwin in The Pterosaurs from Deep Time.

Unfortunately, such statements give ammunition to Creationists, because it sounds like pterosaurs were “specially created” and nothing could be further from the truth. So this damages the good names of both Paleontology and Science and can only be repaired by professional paleontologists with PhDs. I’ve done and continue doing my part.

To put the final nail in the coffin
No paleontologist has been able to put forth even a short series of taxa that demonstrate a gradual accumulation of pterosaurian traits within the Archosauria or Archosauriformes.

We also talked about this and solved this problem in the first four PterosaurHeresies.com blogs here, here, here and here.

It’s actually THIS EASY to solve the problem:
If you include several hundred representatives from the gamut of prehistoric reptiles in phylogenetic analysis, at least by default and at best by shared homologies, you will recover some taxa that will nest closer to pterosaurs than to other reptiles. So it’s the shame of paleontology that no one else has attempted this time-consuming, but otherwise relatively easy task by expanding the taxon list to include lepidosauromorphs, lizards, tritosaurs and fenestrasaurs. Actually it can be done with as few as a dozen key taxa if you’re pressed for time, as already shown in an academic publication (Peters 2000). The taxa it promotes continue to be ignored by all other workers* in one of the more interesting feuds/wars in the history of paleontology. I don’t care if you ignore the paper. Don’t ignore the taxa.

*Except Senter 2003, who bungled his observations and provided cartoons for figures. To be fair, I also made freshman mistakes tracing the same difficult taxa, but corrected them here, here and here.

History of the Ornithodira
In the earliest days of phylogenetic analysis, Gauthier & Padian (1985) placed pterosaurs within the clade Ornithosuchidae (Huene 1914) along with Lagosuchus (= Marasuchus (Sereno & Arcucci 1994)), and the Dinosauria.

A tree recovered from Gauthier 1986

Figure 2. A tree recovered from Gauthier 1986 (form Wiki) Pararchosauriformes are in green boxes. Pterosaurs are included within Ornithodira. Pink arrows point to crocs and dinos (which, sans pteros, make up the Archosauria in the large reptile tree.) 

Later, Gauthier (1986, Fig. 2) noted that the position of pterosaurs and Marasuchus with respect to dinosaurs was not resolved, but found the three formed a monophyletic group he called the Ornithodira. Sereno (1991) followed and expanded on this by including Scleromochlus.

While reviewing Sereno (1991), Kellner (1996) concluded that no particular character linked pterosaurs to the Archosauria (sensu stricto), but added that because of several shared derived characters with basal dinosauromorphs, the traditional hypothesis was the best supported at the time.

Peters (2000) added several taxa (Langobardisaurus, Cosesaurus, Sharovipteryx and Longisquama) that had been excluded in prior studies to three prior phylogenetic analyses and recovered trees in which these taxa nested closer to pterosaurs than any included archosaur. Refinements to the observed morphologies and expansion in the taxon list (both chronicled in PterosaurHeresies.com and ReptileEvolution.com) have further cemented these relationships.

Ornithodira Defined
Gauthier (1986) defined “Ornithodira” as all forms closer to birds than to crocodiles. Here, based on the topology recovered by the large reptile tree (with an unmatched gamut) this definition is redundant with an earlier one (Gauthier and Padian 1985) made for Ornithosuchia.

Sereno (1991) re-defined “Ornithodira” as the last common ancestor of the dinosaurs and the pterosaurs, and all its descendants.

Ornithodira Trashed
Here, based on a larger tree that separates the pterosaurs from the dinosaurs on separate branches that divided in the earliest Carboniferous, the definition of Ornithodira is redundant with Reptilia. This can be easily tested with far fewer taxa. Not sure why paleontologists have not done so. Tradition is cozy and comfortable, but no discoveries have ever been made in comfort.

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
Fraser N 2006. Dawn of the Dinosaurs: life in the Triassic. Indiana University Press, 310 pp.
Gauthier JA and Padian K 1985. Phylogenetic, functional, and aerodynamic analyses of the origin of birds and their flight. In M. K. Hecht, J. H. Ostrom, G. Viohl, and P. Wellnhofer (eds.), The Beginnings of Birds: Proceedings of the International Archaeopteryx Conference, Eichstätt 1984. Freunde des Jura-Museums Eichstätt, Eichstätt 185-197
Gauthier JA 1986. Saurischian monophyly and the origin of birds, In Padian K editor. The Origin of Birds and the Evolution of Flight, 1–55. Memoirs Calif Acad Sc 8.
Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.
Hone DWE and Benton MJ 2008. Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.
Kellner AWA 1996. Remarks on Brazilian dinosaurs. Memoirs of the Queensland Museum 39(3):611-626
Peters D 2000. A redescription of four prolacertiform genera and implications for pterosaur phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106: 293-336
Senter P 2004. 
Phylogeny of Drepanosauridae (Reptilia: Diapsida). J Syst Palaeo 2: 257–268.
Sereno PC 1991. Basal archosaurs: phylogenetic relationships and functional implications. J Vert Paleo 11 (Supp) Mem 2: 1–53.
Unwin, DM 2006. The Pterosaurs From Deep Time. Pi Press. 347 pp.

What is Faxinalipterus? (hint: not a pterosaur…)

Faxinalipterus minima (Bonaparte 2010) has been described from bits and pieces of a sparrow-sized archosaur. The holotype consists of short robust arm bones and much longer leg bones. A displaced maxilla with a large antorbital fenestra and narrow fossa is also referred to the specimen.

Wiki writes, “The describers have assigned Faxinalipterus to the Pterosauria, based on its long hollow limbs and saddle-shaped upper joint of the relatively short and robust humerus, suitable to perform a wing stroke. They see it as perhaps the oldest pterosaur known, as it possibly predates European finds from the Norian. That the possible age difference cannot be large, they see as an indication of rapid evolution in early pterosaurs. Because the Caturrita Formation consists of terrestrial sandstones, that evolution would have had its origins in a terrestrial, not coastal, habitat. They also concluded Faxinalipterus is the most basal known pterosaur, basal features including a lack of fusion between tibia and fibula, a thin radius and a coracoid that has not fused to the scapula. However, Alexander Kellner has suggested Faxinalipterus might be not be a pterosaur but a basal member of the Pterosauromorpha instead or, if the lack of fusion between tibia and fibula is plesiomorphic, even a sister taxon of the Ornithodira.”

Faxinalipterus matched to Scleromochlus. The former is more primitive, like Gracilisuchus, in having shorter hind limbs and more robust fore limbs. The maxilla with fenestra and fossa, plus the teeth, are a good match.

Figure 1. Click to enlarge. Faxinalipterus matched to Scleromochlus. The former is more primitive, like Gracilisuchus, in having shorter hind limbs and more robust fore limbs. The maxilla with fenestra and fossa, plus the teeth, are a good match. Faxinalipterus was not phylogenetically analyzed, but I’m not sure what other Triassic taxon could be closer.

This is going to get some people excited, others not
The maxilla assigned to Faxinalipterus (and I don’t doubt the assignment) has a large squarish antorbital fenestra surrounded by a narrow fossa. No pterosaur has a fossa. Basal pterosaurs always have an angled maxillary ascending process. Basal pterosaurs also have a much more slender fibula. And there are several other mismatches despite the few bones representing the animal. The putative coracoid is more likely a pubis or ischium.

The best match I found (not via phylogenetic analysis) is with Scleromochlus (Fig. 1) a basal bipedal crocodylomorph. Virtually every aspect of Faxinalipterus seems to be a good match, including chronological age and overall size, other than relative limb length. Faxinalipterus is just more primitive in having shorter hind limbs and more robust front limbs. Check out the distal tibia and fibula. A close match to bipedal crocs. Nothing like pterosaurs.

So, for those who like to match Scleromochlus with pterosaurs in the Pterosauromorpha and the Ornithodira, you now have another taxon that doesn’t look like a pterosaur!

Since every discovery can be discovered only once
it’s only human nature that a paleontologist finding a partial skeleton would jump on the most exciting possibility, like “the most primitive known pterosaur.” Unfortunately you also have to play by the rules and compare the new specimen to every other taxon sharing a majority of its traits (even if incomplete) and you have to go with the recovered results.

On the other hand…
Faxinalipterus
 does offer insight into the origin of Scleromochlus and basal crocs, and by extension, basal archosaurs. I’d like to see thefolks toying with Lagerpeton (a convergent biped close to Tropidosuchus) drop it in favor of these two croc bipeds at the base of the archosaur family trees.

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
Bonaparte JF, Schultz CL and Soares MB 2010. Pterosauria from the Late Triassic of southern Brazil. In S. Bandyopadhyay (ed.), New Aspects of Mesozoic Biodiversity, Lecture Notes in Earth Sciences 132:63-71.

Wiki/Faxinalipterus

Bennett’s (2013) Revision of Pterodactylus – Part 3

Yesterday and the day before we looked at Bennett’s (2013) revision of the genus Pterodactylus. Today we’ll nest the new specimen described in Bennett (2013), BMMS 7 (Fig. 1), and examine its traits in Bennett’s view and contrast those using DGS (digital graphic segregation /Photoshop) and phylogenetic analysis employing several hundred traits. Bennett (2013) continues to avoid phylogenetic analysis in favor of a statistical chart of a dozen bone lengths as shown here.

BMMS 7 the new Pterodactylus

Figure 1. Click to enlarge. The new Pterodactylus, BMMS 7, described by Bennett (2013) compared to its tested sisters, P. antiquus and Ardeadactylus (formerly Pterodactylus longicollum), all to scale. BMMS 7 is shown as traced by Bennett (2013, grayscale), as traced using DGS and slightly reconstructed (both colorized). IF these were birds they would be distinct species and perhaps distinct genera, but they are pterosaurs and sister taxa until intervening specimens come forward. In P. longicollum the process within the NAOF appears to be displaced.

Eyeballing and Microscope vs. DGS
Bennett (2013) considered BMMS 7 conspecific with P. antiquus and the largest specimen in the species. He had access to the specimen and I did not. I used phylogenetic analysis and he did not. The large pterosaur family tree nested BMMS 7 between P. antiquus and P. longicollum (renamed Ardeadactylus by Bennett (2013), further reducing the phylogenetic distance between the two putative species! Bennett did not attempt to draw relationships, whether near or far, between P. (A.) longicollum and P. antiquus.

In addition to its transitional nesting, the size of BMMS 7 is intermediate between P. antiquus  and P. (A.) longicollum. Bennett (2013) reports “There are no visible sutures between skull bones” and he traced no sutures. Using Photoshop I found the missing sutures (Fig. 1) in their usual places. Bennett (2013) reports, “Thus, there is no evidence of immaturity,” overlooking evidence for a lizard origin for pterosaurs and Maisano (2002) who noted some lizards never fused certain bones while others continue growing long after bone fusion, as also demonstrated in pterosaur phylogenetic analysis. Most known pterosaurs, unless identical to larger relatives, are adults.

Bennett (2013) reported on BMMS 7, “the very slight concavity may result from lateral crushing of the skull, but does not approach that seen in specimens assigned to P. longicollum.” Well, let’s face the facts head-on: the slight concavity is real and intermediate between the condition in P. antiquus and P. longicollum. This type of observation, one that explains away readily observable data, is common among those who are trying to avoid the obvious: evolution, a word that does not appear in any form in Bennett (2013).

Bennett (2013) reported on BMMS 7, “the nasal process is not visible within [the antorbital fenestra], presumably because the matrix in the fenestra has not been excavated down to the midline of the skull.” I found the top and bottom of the nasal process, but the middle remains buried or broken (Fig. 1).

Bennett (2013) reported on BMMS 7, “There is no trace of a sclerotic ring.” I found three quarters of one, slightly displaced (Fig. 1). It wasn’t ossified and probably represents a very thin layer of matrix covering it or the impression of one lost on the missing counter-plate.

Bennett (2013) failed to report on the presence of a crushed proximal femur on BMMS 7, atop cervical 3 (Fig. 1).

Bennett (2013) reported on the presence of a low premaxillary crest on BMMS 7 and in the holotype of P. antiquus (both less than 1 mm in height), no taller than the anterior portion of the premaxilla. While the purported crest may be a real deal, it is also prudent to remember in all laterally crushed specimens all horizontal bones tend to rotate to the plane of the substrate.

Bennett (2013) reported BMMS 7 is not allied to P. longicollum because the latter  had a concave rostrum, had about 15 teeth per jaw side (rostrum = 18 or mandible = 12 not specified) and the posterior tooth is not below the narial antorbital fenestra (but see Fig. 1). Certainly P. longicollum is different in many respects, but analysis shows these two were sister taxa (given the present very large taxon list).

If P. antiquus and BMMS 7 were conspecific
They would like virtually identical, but might be sized differently. This is based on the observation that embryo pterosaurs are all virtually identical to adults and that verifiable juvenile pterosaurs, like Pterodaustro, Zhejiangopterus and Pteranodon, do not have the  short snout and large eyes Bennett (2006) imagines in juvenile pterosaurs. Moreover, in BMMS 7 the jugal beneath the orbit is deeper than the anterior jugal/maxilla beneath the antorbital fenestra. The jugal descends posteriorly in BMMS 7, more like P. longicollum than P. antiquus. The ventral maxilla beneath the zone just anterior to the NAOF in P. antiquus has virtually no teeth, but the largest teeth are present in that area in BMMS 7. The orbit was much larger than in P. antiquus due to a much longer postorbital process of the jugal. BMMS 7 has a much smaller retroarticular process. So, it has certain autapomorphies.

Earlier we looked at the problems involved when two specimens are a “close but no cigar” in that it could, at that level, represent individual variation or the first steps in evolution toward a new species. That’s just going to happen. But when three specimens are clearly distinct in size and morphology (Fig. 1) then decisions need to be made regarding their genus and species that fall in line with very large and tested phylogenetic analyses.

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.

Reference
Bennett SC 1991. Morphology of the Late Cretaceous Pterosaur Pteranodon and Systematics of the Pterodactyloidea. [Volumes I & II]. Ph.D. thesis, University of Kansas, University Microfilms International/ProQuest.
Bennett SC 1992. Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.
Bennett SC 1994. Taxonomy and systematics of the Late Cretaceous pterosaur Pteranodon (Pterosauria, Pterodactyloidea). Occassional Papers of the Natural History Museum University of Kansas 169: 1–70.
Bennett SC 2001. The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon. Part I. General description of osteology. Palaeontographica, Abteilung A, 260: 1–112. Part II. Functional morphology. Palaeontographica, Abteilung A, 260: 113–153
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.
Bennett  SC (2012) [2013] New information on body size and cranial display structures of Pterodactylus antiquus, with a revision of the genus. Paläontologische Zeitschrift (advance online publication) doi: 10.1007/s12542-012-0159-8
http://link.springer.com/article/10.1007/s12542-012-0159-8
Maisano JA 2002. Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrate Paleontology 22:268-275.
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

Bennett’s (2013), Revision of Pterodactylus – part 2

Yesterday we looked at part 1 of Bennett’s revision of Pterodactylus, laying out certain concepts that Bennett overlooks, like isometry during pterosaur ontogeny and the need for phylogenetic analysis considering hundreds of traits, rather than graphing a dozen bone lengths (which could just as easily show evolution rather than individual growth). Today we’ll take a look at some of the important ‘players’ in Bennett’s revision (Figs. 1-2).

Figure 1. Pterodactylus antiques and the holotypes of P. micronyx, P. kochi and a fourth pterosaur commonly misidentified as P. kochi.

Figure 1. Click to enlarge. Pterodactylus antiquus and the holotypes of P. micronyx, P. kochi and a fourth pterosaur, P. scolopaciceps, commonly misidentified as P. kochi (it’s easy to see the differences here). This misidentification may be part of the problem.

Bennett synonymized P. antiquus and P. kochi (Fig. 1, n4 and n23 in the Wellnhofer 1970 catalog, Fig. 1). P. scolopaciceps, commonly misidentified as P. kochi (it’s easy to see the differences here). This misidentification may be part of the problem.

After Phylogenetic Analysis
Unfortunately the large pterosaur tree found the holotypes of P. antiquus and P. kochi were separated by at least nine taxa. That means that eight included pterosaurs are closer to either one than the holotypes of P. antiquus and P. kochi are to each other. The former is a derived Pterodactylus. The latter is a basal Germanodactylus. P. antiquus nests with other Pterodactylus specimens including P. scolopaciceps (n21). The holotype of P. kochi nests on a branch that gives rise to Germanodactylus and its descendants. The differences are also visibly obvious (Fig. 2).  So P. antiquus and P. kochi shared a common ancestor several nodes down in the tiny pterosaurs, Ornithocephalusn9n31 and SMNS 81775.

If Bennett was lumping P. scolopaciceps (fig. 1, n21 – commonly but erroneously referred to as P. kochi) with P. antiquus, then these two are separated by only one specimen, another uncataloged Pterodactylus (Fig. 1), the one with the little posterior soft crest, itself a distinct species. Even so, analysis and a casual observation shows n21 and n4 are not conspecific.

Figure 2. Click to enlarge. At right, Pterodactylus antiquus and a larger Pterodactylus, P. longicollum, once called Diopecephalus and now called Ardeadactylus. At left are P. micronyx now referred to Aurorazhdarcho.  The big Pterodactylus is definitely a new genus, but (other than the new specimen BMM 00007, see below) it is also the closest known sister taxon to the holotype of Pterodactylus, the first pterosaur officially named and describee. So, given that fact what do you call all the other smaller Pterodactylus that look more like P. antiquus, but nest further away (more primitively)? Aurorazhdarcho actually nests with Eopteranodon at the base of Nyctosaurus + Pteranodon, not with azhdarchoids. P. micronyx actually nests with other tiny cycnorhamphids. So they are not related, despite similarities in the too small inclusion set used by Bennett (2013).

Figure 2. Click to enlarge. At right, Pterodactylus antiquus and a larger Pterodactylus, P. longicollum, once called Diopecephalus and now called Ardeadactylus. At left are P. micronyx now referred to Aurorazhdarcho. The big Pterodactylus is definitely a new genus, but (other than the new specimen BMM 00007, see below) it is also the closest known sister taxon to the holotype of Pterodactylus, the first pterosaur officially named and describee. So, given that fact what do you call all the other smaller Pterodactylus that look more like P. antiquus, but nest further away (more primitively)? Aurorazhdarcho actually nests with Eopteranodon at the base of Nyctosaurus + Pteranodon, not with azhdarchoids. P. micronyx actually nests with other tiny cycnorhamphids. So they are not related, despite similarities in the too small inclusion set used by Bennett (2013).

Bennett (2013) renamed P. longicollum, after others (Meyer 1854, Seeley 1871) had applied the names Pterodactylus and Diopecephalus to the specimen. Bennett (2013) renamed the specimen Ardeadactylus.

This brings up a big question
that we looked at earlier: where to draw the generic and/or specific line? Following phylogenetic logic: If P. antiquus and P. longicollum are sister taxa, which they currently ARE in the largest known pterosaur tree, then if P. longicollum is not Pterodactylus (as Bennett 2013 proposed), then all the other more primitive  Pterodactylus can’t be Pterodactylus — because they are not as closely related to P. antiquus as P. antiquus and P. longicollum are to each other (given present knowledge and analysis). If those are “the rules” pterosaur experts will need new generic names for the less closely related taxa. However, if the morphological differences are great enough between P. antiquus and P. longicollum, which they are (!), then a new name is needed AND new generic names are needed for all the other Pterodactylus specimens. That’s a splitters solution. Personally I don’t like it either.

Anyone have another solution?
Just wish that Bennett (2013) had provided a phylogenetic analysis of all the specimens within Pterodactylus instead of (or along with) the interesting, but ultimately inconclusive bone length chart he provided (which just as easily demonstrates gradual evolution as individual growth).

Allometry, which Bennett likes, has not been demonstrated in pterosaurs, but isometric growth has been demonstrated over and over. And, of course, you don’t get big derived pterosaurs without evolving them from small primitive pterosaurs (which Bennett seems to have overlooked). So putting faith (and that’s all that it is) in allometry in pterosaurs is old school and no longer scientific (btw, don’t put your faith in my results, find out for yourself with your own testing!).

Putting your faith in the nesting of pterosaurs within the Archosauria is also old school, as adherents continue to cling to the hope that someday an archosaur will be found with an ossified sternum and elongated pedal digit 5, among dozens of other lizardy traits found in a series of pterosaur precursors and absent in archosaurs.

For Comparison, Let’s Look at Rhamphorhynchus
In the the genus Rhamphorhynchus there is another wide variety of sizes and morphologies all contained within one genus. Personally I don’t mind having small to large to giant (GIUA-M 4895) specimens within the genus Pterodactylus given the present situation in Rhamphs, Germanodactylus and Pteranodon which all exhibit similar size and morphology variation. Either fix it all, or leave it all. Don’t nibble on it by renaming one taxon at a time.

Growth and Fusion Confusion
Since Bennett doesn’t buy into the lizard origin he doesn’t buy into the Maisano (2002) observations regarding fusion in lizards (and, by extension, pterosaurs). That’s why he doesn’t understand that pterosaurs can continue to grow after fusion or they can never fuse certain parts ever, no matter how old individuals get! No, he’s stuck in the old school archosaur model in which fusion occurs only in adults. That’s why he can, with impunity (and unwarranted, untested support from other pterosaur workers), decide that certain small pterosaurs are juveniles that can morph into dissimilar adults. That’s probably why he judiciously avoids phylogenetic analysis.

Tomorrow, in part 3,  we’ll examine the new pterosaur described by Bennett (2013) as another Pterodactylus antiquus, BMMS 7.

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.

Reference
Bennett SC 1991. Morphology of the Late Cretaceous Pterosaur Pteranodon and Systematics of the Pterodactyloidea. [Volumes I & II]. Ph.D. thesis, University of Kansas, University Microfilms International/ProQuest.
Bennett SC 1992. Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.
Bennett SC 1994. Taxonomy and systematics of the Late Cretaceous pterosaur Pteranodon (Pterosauria, Pterodactyloidea). Occassional Papers of the Natural History Museum University of Kansas 169: 1–70.
Bennett SC 2001. The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon. Part I. General description of osteology. Palaeontographica, Abteilung A, 260: 1–112. Part II. Functional morphology. Palaeontographica, Abteilung A, 260: 113–153
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.
Bennett  SC 2012 [2013] New information on body size and cranial display structures of Pterodactylus antiquus, with a revision of the genus. Paläontologische Zeitschrift (advance online publication) doi: 10.1007/s12542-012-0159-8
http://link.springer.com/article/10.1007/s12542-012-0159-8
Maisano JA 2002. Terminal fusions of skeletal elements as indicators of maturity in squamates. Journal of Vertebrate Paleontology 22:268-275.
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

Bennett’s (2013) Revision of Pterodactylus – part 1

Chris Bennett’s pubs on pteros have been less than regular lately.
And what he has published on has been widely accepted, but largely off the mark (see below). So it is with tepid interest that we take a look at his latest paper (Bennett 2013), New information on body size and cranial display structures of Pterodactylus antiquus, with a revision of the genus.”

In short, Bennett is a lumper, to the extreme.
He lumped tiny pterosaurs, like n9 and n31 (in the Wellnhofer 1970 catalog) under Germanodactylus. He’s lumped Rhamphorynchus under one species as a growth series (Bennett 1995). He lumped nearly all Pteranodon together (other than P. sternbergi) Bennett 1991, 1992, 1994  2001).

Here Bennett (2013, Fig. 1) lumps several Pterodactylus together in a growth series based on the hypothesis of allometry (shape changes) during ontogeny, a concept with no evidence when one considers the morphology of pterosaur embryos. Virtually identical to adults, pterosaur embryos demonstrate isometric growth during ontogeny, a process that goes back to their basal lizard precursor Huehuecuetzpalli based on observations made by Reynoso (1998), and further demonstrated by the  growth series in the azhdarchid, Zhejiangopterus.

What Bennett fails to understand is the only way to arrive at large pterosaurs, like derived crested Pteranodon, is to evolve them from small pterosaurs (Fig. 2) like basal crestless Pteranodon and certain Germanodactylus. This he would discover through phylogenetic analysis and by creating reconstructions (Fig. 2). Even so his own bone length analysis (Fig. 1) points in that direction. This is also how you get large Pterodactylus specimens, like the old P. longicollum (now Ardeadactylus).

Even so, the concept of generic lumping is not necessarily a bad thing. We’ve been doing it for two hundred years with pterosaurs. But we have to figure out where to draw the lines (as discussed earlier) and the only way to do that is phylogenetically, which Bennett is loath to do. There’s no phylogenetic analysis in Bennett (2013), only a chart of skull and post-cranial bone lengths (Fig. 1) demonstrating ontogeny in Bennnett’s mind, evolution in mine (Fig. 2). Note Bennett’s chart does not indicate variation on foot bone morphology, which Peters (2011) found to be notable throughout the clade, even within the genus Pterodactylus (here, here and here for starters). Bennett’s chart includes 12 variables. A good phylogenetic analysis will include over a hundred and fifty before the returns start to flatten out.

Bennett (2013) is also loath to create scaled reconstructions (Fig. 2), which generally tell the tale at first glance better than bone lengths.

Chart from Bennett 2013 of skull and post-cranial bone lengths

Figure 1. Chart from Bennett 2013 of skull and post-cranial bone lengths for putative Solnhofen Pterodactylus specimens identified in Wellnhofer 1970. A few are identified on the chart with callouts. Bennett says these are allometric growth charts. I say this is how you evolve a large Pterodactylus, since embryos demonstrate isometric growth (they are nearly identical to parents in proportion). TM 10341 is a tiny pterosaur related to Dorygnathus, for instance. BSP AS I 739 is the holotype of Pterodactylus. Ardeactylus (n58 of Wellnhofer 1970 and JME-SOS 2428, the flightless pterosaur, n57 are not shown here.

Bennett (2013) includes several putative Pterodactylus (like TM 10341) that nest elsewhere, as recovered by phylogenetic analysis and graphically shown here (Fig. 2).

Many of the specimens previously referred to the wastebasket taxon, Pterodactylus. Some belong. Some do not.

Figure 2. Click to enlarge. Many of the specimens previously referred to the wastebasket taxon, Pterodactylus. Some belong. Some do not. All to scale. Red boxes highlight taxa discussed here. TM10341 is in the upper left hand corner. It is derived from Dorygnathus and leads to azhdarchids.

We’ll continue this tomorrow, introducing the cast of characters in Bennett’s (2013) study (boxed in red, Fig. 2), plus the new one.

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. 

Reference
Bennett SC 1991. Morphology of the Late Cretaceous Pterosaur Pteranodon and Systematics of the Pterodactyloidea. [Volumes I & II]. Ph.D. thesis, University of Kansas, University Microfilms International/ProQuest.
Bennett SC 1992. Sexual dimorphism of Pteranodon and other pterosaurs, with comments on cranial crests. Journal of Vertebrate Paleontology 12: 422–434.
Bennett SC 1994. Taxonomy and systematics of the Late Cretaceous pterosaur Pteranodon (Pterosauria, Pterodactyloidea). Occassional Papers of the Natural History Museum University of Kansas 169: 1–70.
Bennett SC 2001. The osteology and functional morphology of the Late Cretaceous pterosaur Pteranodon. Part I. General description of osteology. Palaeontographica, Abteilung A, 260: 1–112. Part II. Functional morphology. Palaeontographica, Abteilung A, 260: 113–153
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.
Bennett  SC (2012) [2013] New information on body size and cranial display structures of Pterodactylus antiquus, with a revision of the genus. Paläontologische Zeitschrift (advance online publication) doi: 10.1007/s12542-012-0159-8
http://link.springer.com/article/10.1007/s12542-012-0159-8
Peters D 2011. A Catalog of Pterosaur Pedes for Trackmaker Identification. Ichnos 18(2):114-141. http://dx.doi.org/10.1080/10420940.2011.573605
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.

What is Aphelosaurus? Something new and something old.

Aphelosaurus lutevensis (Gervais 1859, Falconnet and Steyer 2007, Early Permian 290 mya) has been known for a long, long time and was described as an enigmatic reptile from the Lower Permian. It is represented by a headless, neckless, tail-less but otherwise completely articulated skeleton. Falconnet and Steyer (2007) considered it an araeoscelidian, but not quite one, and the large reptile tree bears this out. Aphelosaurus nests at their base. That makes it a basal diapsid. Those tiny medial fingers and toes are dead giveaways.

Falconnet and Steyer (2007) considered Aphelosaurus a probable biped and a possible arboreal type. Outgroups were likely both, but also this clade strangely led to marine types, as noted earlier. They did not recognize Eudibamus as an early diapsid. I sure would like to see that specimen up close.

Aphelosaurus and tracing.

Figure 1. Click to enlarge. Aphelosaurus and tracing. sacrals in blue. Image from Steyer 2012.

Here, overlooked by previous workers, the most interesting aspect of Aphelosaurus is a posteriorly elongate ilium, displaced from the sacrals here to align with several caudals. Don’t get your hopes up. No sisters had more than two sacrals. In this case, it’s a toss-up.

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
Falconnet J and Steyer J-S 2007. Revision, osteology and locomotion of Aphelosaurus, an enigmatic reptile from the Lower Permian of France. Journal of Morphology (abstract of the 8th International Congress of Vertebrate Morphology, Paris, July 2007): 38.
Gervais P 1859. Zoologie et paléontologie française – 2e édition. Bertrand, Paris, 544 pp.
Steyer S 2012. Earth before the dinosaurs. Indiana University Press, 182 pp. 

‘I’m a Dino’ cartoons on YouTube – Sordes and Pteranodon

I’m probably the last to know about this.

YouTube has a few “I’m a Dinosaur” cartoons. These two feature Sordes and Pteranodon talking to the camera and to each other. Click to play.

Click to play. I'm a Dinosaur cartoon - Sordes.

Click to play. I’m a Dinosaur cartoon – Sordes.

Cute and cheeky. Just two minutes long.

Click to play. I'm a dinosaur - Pteranodon.

Click to play. I’m a dinosaur – Pteranodon.