Herbstosaurus – What is it?

Herbstosaurus pigmaeus CTES-PZ-1711 (late Jurassic) was originally described as a small dinosaur (Casamiquela 1975). All that is known of this specimen is a pelvis, limb and prepubis (ahhh, there’s a clue!). Ostrom (1978) more accurately identified Herbstosaurus as a pterosaur.

Figure 1. Herbstosaurus on the left compared to Coloborhynchus on the right. The sacrum is similar, but more swept back in Herbstosaurus. The femoral head is disssimilar.

Figure 1. Herbstosaurus on the left compared to the similarly-sized Coloborhynchus on the right to the same scale. The sacrum is similar, but the transverse processes are more swept back in Herbstosaurus. The anterior extent of the ilium and the femoral head/neck/shaft angle are disssimilar. Ornithocheirids are not known for a large prepubis. So, no match here.

But what kind?
Galton 1981 considered Herbstosaurus a member of the “Pterodactyloidea.”  Carroll 1988 narrowed that down to the Pterodactylidae. Wellnhofer 1991 suggested it was a more basal pterosaur, in view of the form of the pelvis. In Unwin 1996 considered it a basal member of the Dsungaripteroidea.

So, with so little consensus, what is Herbstosaurus?

Unfortunately,  
there is not enough here to run Herbstosaurus through phylogenetic analysis using the large pterosaur tree. So Let’s see where trait analysis leads us.

Ilial processes obliquely angled:
Most derived pterosaurs have this except basal pterosaurs up to MCSNB 8950.

Five+ swept back sacrals not coosified:
Most basal pterosaurs have five sacrals not coossified. This does not mean they are juveniles, unless the fossil record is seriously skewed. There are several clades of chiefly larger pterosaurs that coossify the sacrals. Other large forms don’t. Apparently only germanodactylids and their many descendants have swept back sacral transverse processes (Fig. 2) and basal forms, like Germanodactylus rhamphastinus and kin, do not coossify the sacrals.

Figure 2. Swept back sacrals and right angle femoral heads on Germanodactylus rhamphasitinus. Herbstosaurus was much larger overall.

Figure 2. Swept back sacrals and right angle femoral heads on Germanodactylus rhamphastinus. Herbstosaurus was much larger overall. Many bones here are difficult to gauge. The counterplate was also referenced.

Figure 3. The BMM Germanodactylus with an ilium, femur and prepubis shaped like Herbstosaurus, but much smaller.

Figure 3. The BMM Germanodactylus with an ilium, femur and prepubis shaped like Herbstosaurus, but overall the BMM specimen is much smaller.

Prepubis fan shape perhaps without perforation:
The fan shape appears in several clades The perforation is seen in most pterosaurs, but absent in an unassociated few. Germanodactylus often has a fan-shaped prepubis.

Femur with right angle head and neck, but head axis not aligned with neck axis.
This is a tough one. I wondered, is there some breakage that would, if repaired, align the femoral head axis with the femoral neck axis in Herbstosaurus? I’ve only seen drawings (Fig. 1). In most pterosaurs the axis of the head of the femur is very closely aligned with the axis of the neck of the femur. Not so in Herbstosaurus, hence the concern.

Size:
Substantial. No tiny pterosaurs.

Chronology:
Late Jurassic

Summary:
From the available evidence, Unwin 1996 was the most correct. Herbstosaurus is likely a large and primitive Germanodactylus-type pterosaur. Large taxa are already known from that clade. They are the elanodactylids (Fig. 4). Unfortunately what is known from the partial skeletons of those specimens does not overlap with the partial skeleton of Herbstosaurus. In any case, at present with these clues, this seems to be a “best match.”

Germanodactylus and kin

Figure 4. Click to enlarge. Germanodactylus and kin.

References
Casamiquela RM 1975. Herbstosaurus pigmaeus (Coeluria, Compsognathidae) n. gen. n. sp. del Jurásic medio del Neuquén (Patagonia septentrional). Uno de los más pequeños dinosaurios conocidos [Herbstosaurus pigmaeus (Coeluria, Compsognathidae) n. gen. n. sp. from the Middle Jurassic of Neuquén (northern Patagonia). One of the smallest known dinosaurs]. Actas del Primer Congreso Argentino de Paleontologia y Bioestratigrafia, Tucumán 2:87-103.
Galton PM 1981. A rhamphorhynchoid pterosaur from the Upper Jurassic of North America. Journal of Paleontology 55(5):1117-1122.
Ostrom JH 1978. “The osteology of Compsognathus longipes Wagner”, Zitteliana4: 73-118.
Unwin DM 2003. On the phylogeny and evolutionary history of pterosaurs. In E. Buffetaut, J.-M. Mazin (eds.), Evolution and Palaeobiology of Pterosaurs, Geological Society of London, Special Publications 217:139-190

Variation in Homo sapiens – reptile evolution continues

Similarities and differences in the face of humans
Each one of us has eyes, ears, a nose and forehead, but a variety of subtle differences in their shape and placement helps define and distinguish us as individuals. Even twins can be identified given enough familiarity with them. Our similarity binds us together. Our differences make us unique. Variation is very basic to evolution. Over time, enough variation produces new species and larger clades. 

Evolution works in very basic ways.
Overall and in their various body parts, progeny can be distinct from their parents in these several ways (among others unlisted):

  1. larger or smaller
  2. wider or narrower
  3. longer or shorter
  4. more robust or more gracile
  5. more permeable or more durable (skin/scales/osteoderms)
  6. adding protrusions (from horns and hair to feathers to fins to feet and toes) or eliminating them
  7. migrating body parts (more anteriorly, more posteriorly, etc.)
  8. more juvenile or more adult
  9. faster maturation, or slower
  10. colors, shades, transparencies
  11. faster or slower speed capabilities
  12. nocturnal, diurnal
  13. urges to swim, urges to dig, urges to climb

Nearly all of the variation between taxa in the large reptile tree can be attributed to these variations overall or in certain body parts.

Two human males. One has deeper eyes, a protruding chin and less distance from the ear to the back of the head than the other.

Figure 1. Two human males. One has deeper eyes, a protruding chin and less distance from the ear to the back of the head than the other.

Here we’ll show some of the basic elements in the human face.

Chin size
In most humans the chin more or less protrudes. This trait separates us from other species within our genus, like Homo neanderthalensis, as well as archaic members of our own species. No other vertebrates have a chin. It is unique to our species. Lacking a prominent chin nowadays does not make anyone less human. That is just in our gene heritage.

Ear location
The anterior rim of the ear flap is found at the apex of the mandible, in keeping with the origin of the ear bones as former jaw bones. The location of this point can be near to the back of the skull or far (Fig. 1).

Eye location
The eyes can be large and close to the profile (Fig. 1) or deep set and further back from the profile. The further back location provides more shade for the eyeballs.

Wide vs. narrow face.

Figure 2. Wide vs. narrow face.

Face width
Here (Fig. 2) we see two faces scaled to match eyes, nostrils and mouths vertically. However, they do not share the same face width (horizontal bar below faces).

Vertical variation in two faces. What appears to be a low forehead is actually a high face and vice versa.

Figure 3. Vertical variation in two faces. What appears to be a low forehead is actually a high face and vice versa. A large forehead and small chin are childlike features retained in the adult, or not.

Face Height
In some people the face is set higher on the skull, reducing the forehead height and raising the location of the eyes, mouth and nose (Fig. 3). These subtle differences, can be the basis for major changes over eons of time.

Wider skulls in Reptiles
One of the major differences between basal crocs and basal dinosaurs is skull width, with crocs trending toward a wider skull posteriorly. The same can be said about the basal reptiles. The plant-eating lepidosauromorphs trend toward a wider skull, while the insect-eating archosaurmorphs do not. Dimorphodon had a tall skull. The flat-head anurognathid had a wide one.

The migration of the nostrils posteriorly on parasuchians is enhanced by the elongation of the premaxilla. Conversely, in the related champsosaurs, the nostril migrates back to the snout tip… all a matter of facial proportions (Fig. 3).

This is just a primer, a jumping off point. You can find many more examples of convergence for nearly every character trait you may wish to list.

Kaikaifilusaurus (Priosphenodon) and the origin of the Rhynchosaurs

This post was updated with a new figure 1 on March 8, 2014.

Kaikaifilusaurus calvoi (Simon and Kellner 2003, Cenomian, Cretaceous, Fig. 1) was considered a new and late surviving sphenodontoid (= rhynchocephalian) when originally described, and indeed it is.

Also known as Priosphenodon avelasi (Apesteguía and Novas 2003).

However, and going unrecognized, Kaikaifilusaurus is also the closest sister I’ve tested (Fig. 2) to the Rhynchosauria (HyperodapedonFig. 3). Thus Kaikaifilusaurus knits rhynchosaurs even closer to the Rhynchocephalia in the large reptile tree (Fig. 2).

Fig. 1. Kaikaifilursaurus from the Cenomian, Cretaceous, is the overlooked late surviving rhynchocephalian sister to the rhynchosaurs. Yes, the lateral temporal fenestra is secondarily infilled. Image from Apesteguía and Novas 2003.

Fig. 1. Kaikaifilursaurus from the Cenomian, Cretaceous, is the overlooked late surviving rhynchocephalian sister to the rhynchosaurs. Yes, the lateral temporal fenestra is secondarily infilled. Image from Apesteguía and Novas 2003.

Phylogenetic nesting of Kaikaifilusaurus with Hyperodapedon, a rhynchosaur.

Figure 2. Phylogenetic nesting of Kaikaifilusaurus with Hyperodapedon, a rhynchosaur.

Of course this is heresy
While a hundred years ago paleontologists associated rhynchosaurs with rhynchocephalians, all that changed after Benton (1983) when rhynchosaurs were thereafter associated with archosaurs and prolacertiforms, none of which they resembled so much. If anyone else is wondering about such strange bedfellow associations, join the club.

Sorry for the late post
I just became aware of Kaikaifilusaurus while hanging around the Geology Library at Washington University, here in St. Louis. The Simon and Kellner (2003) paper is already ten years old. The holotype MPCHv 4 consists of part of a mandible. Figure 1 portrays a later find, MPCA 300 from Apesteguía and Novas (2003).

Like a Rhynchosaur
Kaikaifilusaurus has elevated the orbit to the top of the skull. The toothless premaxilla descends sharply. The dentary anterior processes hold the premaxilla medially when the jaws are closed. The maxilla is ventrally convex. There’s more of course.

Unlike a Rhynchosaur
Kaikaifilusaurus lost the lateral temporal fenestra, which all other rhynchocephalians except Trilophosaurus, retained. The jugal expanded to fill that opening. Kaikaifilusaurus doesn’t have a wider than typical skull, nor do the nares open dorsoanteriorly.  I’d like to see images of the skull from other views to score more traits.

Chronology
Like our very own anachronistic Sphenodon, Kaikaifilusaurus was a late survivor in the Cretaceous from the early Triassic radiation that produced Hyperodapedon and the rhynchosaurs.

The origin of the Rhynchosauria featuring Kaikaifilusaurus.

Figure 3. The origin of the Rhynchosauria featuring Kaikaifilusaurus. Certainly sometime, someone will find a closer relative to rhynchosaurs, but at present this may be the best.

Funny that no online reference discusses the rhynchosaur connection of Kaikaifilusaurus, yet it seems rather obvious (Fig. 3). The previous morphological gap between Mesosuchus (Fig. 3) and Hyperodapedon in the large reptile tree was somewhat broad. I suppose it was only a matter of time (like ten years ago) for the transitional taxon to appear. It matters little that certain traits (like the loss of the lateral temporal fenestra) show that the ancestors of Kaikaifilusaurus evolved their own way for tens of millions of years after the Triassic.

A note to all detractors
All of the above is done without Photoshop, so no DGS here. I’ve simply expanded the gamut of the inclusion list to maximize the opportunity for a correct nesting of all 341 taxa and I used images form the literature. You can test these associations yourself by simply including these taxa and your own traits in any phylogenetic analysis.

Certainly sometime, someone will find a closer relative to rhynchosaurs, but at present this may be the best we have (unless there’s another paper I’m unaware of floating around now!) Don’t make me wait another ten years, if so.

Reference
Apesteguía S and Novas FE 2003. Large Cretaceous sphenodontian from Patagonia provides insight into lepidosaur evolution in Gondwana. Nature 425:609-612
Benton MJ 1983. 
The Triassic reptile Hyperodapedon from Elgin, functional morphology and relationships. Philosophical Transactions of the Royal Society of London, Series B, 302, 605-717.
Simon ME and Kellner AWA 2003. New sphenodontid (Lepidosauria, Rhynchocephalia, Eilenodontinae) from the Candeleros Formation, Cenomanian of Patagonia, Argentina. Boletim do Museu Nacional, Geologia, nova série 68:1-12. online here.

“There’s no crying in Baseball” and there’s no “Trust” in Science.

Tom Hanks, screaming, "There's no crying in baseball!" from the 1992 movie, "A League of Their Own."

Fig. 1. Tom Hanks (as manager Jimmy Foxx), screaming, “There’s no crying in baseball!” from the 1992 movie, “A League of Their Own.”

In A League of Their Own (1992),” Tom Hanks, played the legendary slugger/manager, Jimmy Foxx. Here (Fig. 1) Hanks yells at his ballplayer, “there’s no crying in baseball.” Famous scene. Oft repeated. See the scene here on YouTube.

On a similar note
A recent letter to PterosaurHeresies mentioned that the writer and, according to him, most of the paleontology community, couldn’t “trust” my drawings and interpretations.

I told him that’s how it should be.

This is Science.

There is no “trust” in Science.

He and others have the opportunity to and should (if they have the opportunity to) duplicate the observations or tests and see if those interpretations and results differ or are the same as published.

After all, that’s what I do everyday. I find out what I can trust, because I’ve duplicated it –and what I can’t trust, because I can’t duplicate it.

In Science there is only testing.
Everything in Science is measurable and repeatable. If it works for me, it should work for you and vice versa. There are no special circumstances. The supernatural does not enter in. If you don’t get my results, one of us (not always me) has done something wrong. Maybe the taxon inclusion list was not broad enough? Maybe a suture and a crack were misidentified.

The writer and others like him don’t like it when I test their suppositions and traditions and they tell me so. That’s good because they might be right every so often or even more often than not. And I need to know these things to improve the site.

Or vice versa they might learn something they didn’t know before. They might see new possibilities that bust old paradigms.

The whole point of a flexible medium, like the Internet, is to get it right, provide updates and always be on the cutting edge. That’s why I make changes as new valid data comes in.

However, if you’re going to bitch,
at least have the decency of providing valid data and results that make sense and back up your statements. Discussing technique, past history or any other issues involving the author deftly avoids the real issue: the taxon in question. If you keep your focus on the reptile(s) you’ll have a better reception for your query or comment and you might even get your wish, a change in the website!

I appreciate those who provide valid alternatives as solutions, but, paraphrasing Jimmy Foxx, “There’s no crying in Science either.” If you know solutions, you need to provide them. If you know someone who has a solution that differs from mine, have that person get in touch to run that solution by. If you just want to cry about it, you’re not helping your cause, your Science or this blog.

And please, no excuses that,”it would take eons to go through all of my mistakes.” Pick one or two and we’ll start from there. Build credibility. Stay with the taxa. Keep your comments focused on the reptiles. Stop bitching about the technique or yours truly. In the end, we’re going to end up swapping photographs as evidence anyway, so telling me photographs are useless is likewise illogical. The Brits defeated the Nazis using photographic interpretation, as shown recently on a PBS special. So it’s a valid tool.

Now let’s go people. Keep those cards and letters coming in!

(but only with solutions attached)…

Pterosaur Sternal Complex: Focus on that oddball, Dorygnathus

Figure 1. A series of fenestrasaur and pterosaur sternal complexes scaled to a common humerus length in phylogenetic order.

Figure 1. A series of fenestrasaur and pterosaur sternal complexes scaled to a common humerus length in phylogenetic order.

When you have a robust phylogenetic tree, as we do for the pterosaurs, and you have a catalog of reconstructions, as we do here, many interesting things can happen.

Here (Fig. 1) we’ll take a look at the development of the sternal complex, the anchor for the large pectoral flying adductors in one clade of pterosaurs that happened to reduce the sternal complex for reasons unknown. The wings, in this case, were not reduced.

This (Fig.1) is close to an evolutionary sequence based on a cladogram, represented by specimens not on, but close to a direct lineage.

Earlier we looked at the migration of the sternum anteriorly above the interclavicle to meet the short, transverse clavicles in Cosesaurus and Langobardisaurus.

In Longisquama, a taxon more committed to flapping, the clavicles wrapped posteriorly around the sternum (what some (Jones et al. 2000, Martin 2004) have erroneously considered homologous to a bird wishbone, aka – fused clavicles). The interclavicle developed a deep keel. The humerus developed a deltopectoral crest and expanded distal condyles, like those of a pterosaur.

The most basal pterosaur MPUM 6009 was little different, but had a smaller keel and a deeper sternal portion.

Eudimorphodon ranzii had more robust elements, and a shape like a triangle added to a cardioid. In this lineage, the size and shape of the sternal elements make Eudimorphodon appear to be an outlier, trending more toward the large sternal complex clade of Campylognathoides + Rhamphorhynchus.

Eudimorphodon cromptonellus had a smaller sternum but retained a semicircular shape.

Eudimorphodon Bsp 1994 had a smaller sternum, triangular in shape, with anterior processes at the coracoid joint.

Sordes was similar without the anterior processes.

The sternal complex of the Donau specimen of Dorygnathus was tear-drop shaped, semi-circular posteriorly.

All other Dorygnathus specimens had a tiny sternal complex (yet individually distinct in shape), a character that readily distinguishes them from Rhamphorhynchus. This one, SMNS 50164 nests at the base of the following pterosaurs.

TM 10341 was a tiny dorygnathid, yet its sternal complex was relatively larger with lateral processes. Unrelated Scaphognathus had a very similar shape by convergence.

“Rhamphodactylus” expanded laterally and posteriorly, creating a circular outline.

Beipiaopterus had sharp anterior corners creating a shield shape.

Among later taxa in this clade, the flightless JME SoS 2428 had a relatively larger sternal complex than the flighted azhdarchids, like Quetzalcoatlus and Zhejiangopterus.

Tiny sternal complex for Dorygnathus
Padian (2008) reported that, “The sternum [sternal complex] in Campylognathoides (Wellnhofer 1974) is frequently preserved and is much larger than in Dorygnathus; however, the former genus has relatively longer wings and a smaller skull, which suggests functional differences that may be connected with sternal morphology. Additionally, Dorygnathus may have had a larger posterior sternal extent that was not calcified, but merely cartilaginous.”

This is what we call wishful thinking or following a paradigm.
I’ve done it. Padian did it. In all Dorygnathus specimens gastralia are few and appear only in the posterior region. So there is a large gap between ossified parts ventrally (Fig. 2), distinct from most other pterosaurs with a larger sternal complex. If the region was a cartilaginous extension it would have been odd and improbable, as the clavicle and interclavicle ossified portions were also tiny.

Figure 2. The SMNS 51827 Dorygnathus with its long torso, really tiny sternal complex and open ventral area without gastralia. What's going on here with regard to diet and flying abilities?

Figure 2. The SMNS 51827 Dorygnathus with its long torso, really tiny sternal complex and open ventral area without gastralia. What’s going on here with regard to diet and flying abilities? On a secondary note, note the butt joint between the pubis and prepubis. This is not a rotating bone.

Let’s talk about that -really- tiny sternal complex in the SMNS 51827 specimen
All Dorygnathus have a tiny sternal complex, but the one in SMNS 51827 is the smallest (Fig. 2) I’ve seen. Generally, when one part shrinks, another expands. In this case as the chest region shrank, a more flexible belly region expanded. Why? Hard to say. But the solution is not convergent with Rhamphorhynchus, which shared long teeth, but had a large sternal complex and a short gastralia-filled stiff belly.

The manual claws of SMNS 51827 were large (Fig. 3), trenchant and preserved (Fig. 3) as if grasping an object with a circular cross section, like a tree trunk of appropriate diameter.

The SMNS specimen of Dorygnathus, largely complete and exposed ventrally. Note those hands, posed as if grappling a tree trunk of that diameter.

Figure 3. The SMNS specimen of Dorygnathus, largely complete and exposed ventrally. Note those hands, posed as if grappling a tree trunk of that diameter. Pertinent bones colorized using DGS. Surprise to one and all… DGS reveals that enough gastralia to fill the belly appear to be missing here! Just a few (in pink) show up here. Left side ribs in blue. Right side ribs in green. Sternal complex in purple and blue. See figure 2 for tracings without in situ fossil.

The loss of ventral ossification permitted the dorsal vertebrae to be more flexible. It also permitted the belly to be more expandable. Vertebrae #14 is longer than the others. It happens to be the vert that anchored the scapulae. The entire torso is relatively elongated in SMNS 51827 (Fig. 4).

Figure 3. The elongated torso, small sternal complex and long fingers distinguish this Dorygnathus specimen SMNS 51827.

Figure 4. The elongated torso, small sternal complex and long fingers distinguish this Dorygnathus specimen SMNS 51827. Were those rake-like teeth used for raking in vegetation? Good question. Maybe. Maybe not.

The last time we saw such a long torso, such a small sternal complex and such long fingers was in Longisquama (Fig. 4), the sister to the Pterosauria (they shared a recent common ancestor).

Figure 1. Longisquama on a tree trunk.

Figure 4. Longisquama on a tree trunk.

Actually the sternal complex is smaller in Dorygnathus, just large enough to anchor the coracoids. Perhaps we can imagine Dorygnathus had a similar lifestyle, leaping from tree trunk to tree trunk, weakly flapping and mostly gliding due to its smaller than typical pectoral anchors but normal-sized wings.

Figure 1. Archaeopteryx and several other basal birds. Here Archaeopteryx is a relative giant. This is an older illustration, predating all of the recent and now, not so recent, finds from China. The wings, sternum and tail are derived in the smaller birds. That's the smallest Archaeopteryx, the Eichstätt specimen.

Figure 1. Archaeopteryx and several other basal birds. Here Archaeopteryx is a relative giant. This is an older illustration, predating all of the recent and now, not so recent, finds from China. The wings, sternum and tail are derived in the smaller birds. That’s the smallest Archaeopteryx, the Eichstätt specimen.

An analogy may also be drawn with Archaeopteryx, a primitive bird that likewise had substantial wings, stem-like coracoids and large grappling claws, but very little sternum to anchor flight muscles.

In summary and one lifestyle struck off the “probable” list
Apparently, and distinct from most other pterosaurs, Dorygnathus was a long-waisted, large-clawed, weak flyer. Perfectly adapted to grappling tree trunks, it may have barely gained altitude as it weakly flapped, gliding from tree to tree. So, a lifestyle spent dipping for fish over the open sea seems less probable.

Figure 5. Pioneer herbivores in their clades, both with large procumbent teeth, not unlike Dorygnathus. Daemonosaurus is a dinosaur. Stenocybus is a basal therapsid leaning toward the galesaurid/dicynodont branch.

Figure 6. Pioneer herbivores in their own clades, both with large procumbent teeth, not unlike Dorygnathus. Daemonosaurus is a dinosaur. Stenocybus is a basal therapsid leaning toward the galesaurid/dicynodont branch.

If not a fish diet, then what?
I’m still wondering what the alternative diet would be, considering those teeth, that Middle Jurassic forest and that belly. According to Padian (2008) no stomach contents are known. With those raking teeth are we looking at a high-browsing herbivore? Angustinaripterus had even larger raking teeth, but no post-crania is known. Notably some reptile clades that adopted herbivory had basal forms that developed procumbent teeth, like Daemonosaurus (among the Dinosauria) and Stenocybus (among the basal Therapsida (Fig. 6) (galeasaurids and dicynodonts).

Better Flyers Millions of Years Later
The several descendant clades of Dorygnathus all developed a larger sternal complex and larger flight muscles, as did the several descendant clades of Archaeopteryx. Even the flightless pterosaur, JM SoS 2428, had a large sternal complex!

Better Flyers Among Other Jurassic Pterosaurs
Similarly the clades that splintered off earlier (Dimorphodontia and Eudimorphdon ranziiCampylognathoides + Rhamphorhynchus) also all developed a much larger sternal complex. Maybe the Dorygnathus clade just got off to a slow start with regard to flying, slowed down a bit during their Dorygnathus phase, then really took off thereafter.

References
Jones TD et al 2000. Nonavian Feathers in a Late Triassic Archosaur. Science 288 (5474): 2202–2205. doi:10.1126/science.288.5474.2202. PMID 10864867.
Martin LD 2004. A basal archosaurian origin for birds. Acta Zoologica Sinica 50(6): 978-990.

Variation within Dorygnathus – part 2

Kevin Padian (2008) on Dorygnathus banthensis represents the latest traditional thinking on this genus and species. We’re expanding on that with multiple reconstructions and a phylogenetic analysis, both lacking previously. Yesterday was part 1.

Figure 1. Click to enlarge. Rhamphorhynchus and Dorygnathus compared. Here we see basal taxa and middle of the evolutionary sequence taxa. R has a larger sternum in all cases.

Figure 1. Click to enlarge. Rhamphorhynchus and Dorygnathus compared. Here we see basal taxa and middle of the evolutionary sequence taxa. R has a larger sternal complex, smaller antorbital fenestra, longer m4.1  and shorter neck in all cases. The other distinctions are less obvious.

Often confused with or mistakenly related to Rhamphorhynchus
Dorygnathus
 (Fig. 1) and Rhamphorhynchus both shared big procumbent teeth by convergence. Whereas Rhamphorhynchus is known from several sizes (falsely considered ontogenetic by those who have not performed a phylogenetic analysis on clade members), Dorygnathus is not well known for size differences (Fig. 2), but there are some small ones and large ones.

Sericipterus (Andres et al. 2010, Fig. 2) is larger than the others, but it is not considered congeneric. Andres et al. (2010) considered it closest to Harpactognathus and Angustinaripterus (Fig. 2), both pre-ctenochasmatid dorygnathids. Their tree found these three taxa and Cacibupteryx to be derived from a sister to Dorygnathus, which is duplicated in the large pterosaur tree, only with more intervening and related taxa.

Looking for “juveniles,” but didn’t find any
Curious, I wondered if the small “Hauff” specimen would nest with one of the other larger specimens and so be considered a possible juvenile. So I ran the analysis. Instead, the Hauff specimen nested at the base of the clade, derived from a sister to the equally small Sordes (Fig. 1). This is not unexpected, but follows size patterns seen in most, if not all, major pterosaur clades with smaller specimens at the bases of distinct clades and genera. This went unnoticed in Dorygnathus until now.

Figure 2. Click to enlarge. Reconstructions of several Dorygnathus and related taxa based on tracing bones. Here they appear to be several distinct species and certain other pterosaurs appear to be congeneric (depending if you're a lumper or splitter). This is confirmed by phylogenetic analysis. One branch of dorygnathids is basal to ctenochasmatids. Another is basal to azhdarchids. A third, more basal clade, not far from Sordes, is basal to scaphognathids and darwinopterids, represented here by Jianchangopterus. So Dorygnathia survived to the Maastrichtian.

Figure 2. Click to enlarge. Reconstructions of several Dorygnathus and related taxa based on tracing bones. Here they appear to be several distinct species and certain other pterosaurs appear to be congeneric (depending if you’re a lumper or splitter). This is confirmed by phylogenetic analysis. One branch of dorygnathids is basal to ctenochasmatids. Another is basal to azhdarchids. A third, more basal clade, not far from Sordes, is basal to scaphognathids and darwinopterids, represented here by Jianchangnathus. So Dorygnathia survived to the Maastrichtian. A small one, the Hauff specimen, is basal. There is also a clade leading to a large Sericepterus that did not lead to other clades. The variety here is comparable to the Rhamphorhynchus clade.

SMNS 558866 is also small (Fig. 1), but nests between two larger specimens. While sharing many traits with all other Dorygnathus specimens, it appears to have a unique morphology, so is not a juvenile of the R156 specimen or Cacibupteryx.

So no juveniles here!! (Same as in Rhamphorhynchus, they’re growing up in damp leaf litter far from ancient Geman seas). I would have liked to have discovered some juveniles here, but you have to let the data do the talking.

To lump? Or to split?
The Dorygnathus clade suffers from the same nomenclature problem that other pterosaur clades suffer from. Several professionally named “Dorygnathus” are phylogenetically separated from one another by more recently named novel genera. No prior phylogenetic analysis including more than one Dorygnathus was ever attempted before. That’s the main problem. As you can see, there is variety within this clade that was previously overlooked.

There is no more and no less variation here in Dorygnathus than in the present Pteranodon, Pterodactylus, Germanodactylus, Rhamphorhynchus, Eudimorphodon and other wastebasket taxa. Someday a grand poobah will straighten this all out for us and have his authority respected. I don’t care if the lumpers win or the splitters win, but the tree has to be acknowledged agreed upon before we get down to naming genera again. It’s getting very confusing out there.

Tomorrow we’ll talk about Dorygnathus’ most embarrassing trait, that tiny sternal complex.

References
Andres B, Clark, JM and Xing X 2010. A new rhamphorhynchid pterosaur from the Upper Jurassic of Xinjiang, China, and the phylogenetic relationships of basal pterosaurs’, Journal of Vertebrate Paleontology, 30: 1, 163-187.
Padian K 2008. The early Jurassic pterosaur Dorygnathus banthensis (Theodori, 1830). Special papers in palaeontology 80: 64 pp.

Variation within Dorygnathus – part 1

Kevin Padian (2008) on Dorygnathus banthensis represents the latest traditional thinking on this genus and species. Unfortunately he did not reconstruct more than one specimen (Fig.1) and he did not employ phylogenetic analysis neither between specimens nor between other pterosaurs. Those shortcomings are rectified here. This post was inspired by the addition of three new Dorygnathus specimens to the cladogram (Fig. 2 in color).

Padian's (2008) version of Dorygnathus taking off. This is a freehand sketch, not a tracing of bones.

Figure 1. Padian’s (2008) version of Dorygnathus taking off. This is a freehand sketch, not a tracing of bones (as in Figs. 2, 3). Padian did not attempt to reconstruct more than one Dorygnathus to test the supposition that there are over 30 specimens of this one genus and species. Nor did he attempt a phylogenetic analysis. Reconstructions (Fig. 2) illuminate the subtle and not so subtle variations. Padian’s bipedal pterosaur appears to be in an attack mode. I’d like to see him draw Dorygnathus in a common pose of balance.

From the Padian abstract (abridged here):  
“Over 30 skeletons and dozens of isolated bones of the Liassic pterosaur Dorygnathus have been recovered from the Early Jurassic (Toarcian) of Baden–Württemberg and Lower Saxony in Germany, and from Nancy, France. All but one specimen have been assigned to the species D. banthensis. Dorygnathus is most closely related to Rhamphorhynchus and the Pterodactyloidea.”

Figure 2. Click to enlarge. Reconstructions of several Dorygnathus and related taxa based on tracing bones. Here they appear to be several distinct species and certain other pterosaurs appear to be congeneric (depending if you're a lumper or splitter). This is confirmed by phylogenetic analysis. One branch of dorygnathids is basal to ctenochasmatids. Another is basal to azhdarchids. A third, more basal clade, not far from Sordes, is basal to scaphognathids and darwinopterids, represented here by Jianchangopterus. So Dorygnathia survived to the Maastrichtian.

Figure 2. Click to enlarge. Reconstructions of several Dorygnathus and related taxa based on tracing bones. Here they appear to be several distinct species and certain other pterosaurs appear to be congeneric (depending if you’re a lumper or splitter). This is confirmed by phylogenetic analysis. One branch of dorygnathids is basal to ctenochasmatids. Another is basal to azhdarchids. A third, more basal clade, not far from Sordes, is basal to scaphognathids and darwinopterids, represented here by Jianchangnathus. So Dorygnathia descendants survived  into the Maastrichtian. A small one, the Hauff specimen, is basal. There is also a clade leading to a large Sericepterus that did not lead to other clades, but became extinct. The variety here is comparable to the Rhamphorhynchus clade.

Maybe not…
Reconstructions of several Dorygnathus specimens (Fig. 1) reveal an overlooked variety in this genus that does not become readily apparent until accurate tracings and reconstructions are made. These specimens do not appear to be conspecific, confirmed by phylogenetic analysis. Each has at least a few distinct traits. While most specimens were about the same size, each had a distinct morphology with longer and shorter skulls, different sized fingers, distinct sternal complex and pelvis shapes and distinct pedal proportions.

Descent and descendants
According to the large pterosaur tree, Dorygnathus descended from a sister to Sordes and Changchengopterus, both smaller specimens.

To Padian’s point: Dorygnathus is a key taxon at the base of two pterodactyloid-grade clades: ctenochasmatidae (which retained long teeth) and azhdarchidae (which did not). Dorygnathus is also a key taxon at the base of Jianchangnathus + Pterorynchus + Darwinopteridae and Scaphognathus (which is basal to all remaining pterodactyloid-grade pterosaurs) and these also had smaller teeth. Padian, unfortunately, did not see the specifics, but reported very broad generalizations regarding pterosaur relations.

Despite appearances, Dorygnathus is not so much related to Rhamphorhynchus, but both developed long procumbent teeth by convergence and share a last common ancestor near basal Campylognathoides and Eudimorphodon.

From the Padian text:
“It appears that Dorygnathus is most closely related to Scaphognathus and Rhamphorhynchus, though without some of the synapomorphies that appear to ally the latter genus to the Pterodactyloidea (such as the lower, longer snout, the anterior displacement of the jaw joint to beneath the midpoint of the orbit, the more steeply inclined quadrate, the reduction of the lower temporal fenestra, the elongation of the first wing-phalanx, and the partial reduction of the fifth toe).”

So, Padian is going on appearances here, not analysis
[Actually many pterosaurs, including the SMNS 50164 specimen of Dorygnathus had a lower, longer snout along with the anterior displacement of the jaw joint. According to the large pterosaur tree Rhamphorhynchus inherited its long first wing phalanx from Campylognathoides and most pterodactyloid-grade pterosaurs and Dorygnathus do not share this trait. Likewise the partial reduction of the fifth toe in Rhamphorhynchus was inherited from Campylognathoides.] Dorygnathus retained an elongated pedal digit 5 with a bent p5.2.

From the Padian text:
“Dorygnathus appears to be one of the closest genera to Rhamphorhynchus and, hence, to the Pterodactyloidea (a conclusion independently reached by Unwin 2003a). They share a long mandibular symphysis that is toothless at its anterior end, large anterior teeth strongly inclined forward and outward, nares more reduced and located more posteriorly and higher on the skull, reduced antorbital opening, and jugal lacking a posterior process along the base of the skull.”

[Again, in this age of phylogenetic analysis, basing relationships on “appearance” is to be avoided.] Padian errors when he reports that all Pterodactyloidea has a long mandibular symphysis that is toothless anteriorly disregarding exceptions here, here and here. The nares are also reduced in the non pterodactyloids, Pterorhynchus and Darwinopterus. Pterodactyloids do not have a reduced antorbital opening. Some Dorygnathus and Rhamphorhynchus share this trait, but other Dorygnathus evolve a larger antorbital fenestra. Neither clades are 100% without a jugal posterior process.

From the Padian text:
Dorygnathus shares other features with Scaphognathus but most appear to be plesiomorphies for the lineage. I conclude that Dorygnathus is a member of the main stem of pterosaur evolution leading to the Pterodactyloidea, and is the closest representative of this main lineage in the Early Jurassic.Both Campylognathoides and Dimorphodon, the two other known Liassic genera, are too different and specialized to be as closely related to this main stem of pterosaur evolution; they are important side-branches with roots in the Late Triassic forms.”

[Giving credit where credit is due (even though the current large pterosaur tree topology specified by Peters 2007 predates this), Padian correctly connects Dorygnathus to pterodactyloids, but he has no idea which ones or through which specimens. He simply notes [correctly] that Dorygnathus is a better Liassic candidate than the other two Liassic candidates, Campylognathoides and Dimorphodon.]

It's better to trace bones accurately than to freehand reconstructions. Moreover, the quadrupedal pose Padian promotes has several errors (fingers not lateral, hands in front of shoulders, humerus over abducted).

Figure 3. It’s better to trace bones accurately than to freehand reconstructions. Moreover, the quadrupedal pose Padian promotes has several errors (fingers not lateral, hands in front of shoulders, humerus over abducted). Currently no pterosaur tracks match Dorygnathus feet. The huge manual claws argue against a quadrupedal configuration. Padian, once the champion of bipedal locomotion in pterosaurs, must not have had much evidence to stand on if he has fallen so far the other way.

From the Padian caption (Figure 3):
Dorygnathus banthensis; reconstruction of the skeleton in a hypothetical quadrupedal pose. In this position the left humerus has reached the limit of forward protraction and rotation; retraction of the limb would have been slight, with minimal force. The pace length of the hindlimbs would not have been so limited and would have been much greater than that of the forelimbs. This suggests that the forelimbs could have served as little more than supports for the front end of the body, if they were necesary at all. Note also the forward slope of the dorsal column in this position.”

[Actually, in Padian’s tipped over pose (Fig. 3) the forelimbs would have been essential for support. However, in the Peters pose (Fig. 3, color) the forelimbs could be elevated or implanted without changing the center of balance over the toes. The Padian skull is not an accurate representation of the Vienna specimen and his pedal digit 5 is way too small, the unfortunate results of ‘eyeballing’ it.]

More tomorrow and the next day when Dorygnathus gets really interesting

References
Padian K 2008. The early Jurassic pterosaur Dorygnathus banthensis (Theodori, 1830). Special papers in palaeontology 80: 64 pp.