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

Advertisements

One thought on “Bennett’s (2013), Revision of Pterodactylus – part 2

  1. Pingback: DinoAstur - » Ardeadactylus, nuevo nombre para Pterodactylus longicollum

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s