Modular (Mosaic) Evolution according to Wikipedia

The following is a direct lift from the Wiki article on Modular Evolution with critical comments added in red.

Redirected to:
Mosaic evolution (or modular evolution) is the concept that evolutionary change takes place in some body parts or systems without simultaneous changes in other parts.[1] Another definition is the “evolution of characters at various rates both within and between species”.[2]408 Its place in evolutionary theory comes under long-term trends or macroevolution.[2]

By its very nature, the evidence for this idea comes mainly from palaeontology. It is not claimed that this pattern is universal, but there is now a wide range of examples from many different taxa. Some examples:

Unfortunately this narrow and hopeful view ignores the fact that paleontologists can identify an australopithecine from its skull and teethvertebrae and other body parts. So, no modular evolution here. 

And yet paleontologists can identify Archaeopteryx by the pelvis, skull, tail, etc, whether wings or feathers are present or not. The differences are present, even if subtle. So, no modular evolution here. 

  • Meadow voles during the last 500,000 years.[6]

This example is reported  at the population level. Nothing here strong enough to differentiate one species from another. 

Unfortunately, Darwinopterus was not the transitional taxon between the long tails and short tails when you add more taxa to your analysis. Darwinopterus was an evolutionary dead end with no Cretaceous descendants. Sure it had a long skull and long neck, like pterodactyloids. But anurognathids had a short tail like pterodactyloids and only Andres thinks they were transitional. So, no modular evolution here. Convergence, yes!

Evolution from tiny four-toed pre-horses to large one-toed modern horses indeed took place over many millions of years. Certain traits occurred simultaneously. Others waited until later. So, no modular evolution here. 

Not sure what the reporter has in mind here, but certainly there were several clades that demonstrate convergence. Mammal experts are famous for being able to identify their specimens from a few teeth alone. So while other parts were evolving, so were the teeth. So, no modular evolution here. 

If anyone can provide an example of modular evolution in vertebrates, please bring it to the attention of the Wikipedia author of this article. If modular evolution were indeed present, paleontologists would be confounded by one end of the body not matching the other. Phylogenetic analysis usually takes care of all such problems.

And convergence is out there ready to trip you up if you’re not careful.

The Antorbital Fenestra in Reptiles – x4

The antorbital fenestra is THE classic trait marking the traditional Archosauria (Archosauriformes). However, the large reptile study produced four clades with an antorbital fenestra. Here they are:

The antorbital fenestra in reptiles

Figure 1. The antorbital fenestra in four reptiles. Chroniosuchus represents the chroniosuchids. Cosesaurus represents the Fenestrasauria, which includes the pterosaurs. Parasuchus represents the Pararchosauriformes. Proterosuchus represents the Euarchosauriformes, which includes the dinosaurs, crocs and birds. Each antorbital fenestra appeared individually, unrelated to and by convergence with the others. Virtually all present studies do not recognize this.

There are several characters that most paleontologists consider originated only once. Among them is the antorbital fenestra, an extra hole in the skull between the naris and orbit. The present large analysis (Figure 2) recovered a single tree in which the antorbital fnenestra appered four times: 1) in the Chroniosuchia (basal lepidosauromorph); 2) in the Fenestrasauria (which also includes the Pterosauria — and the antorbital fenestra may also extend to Jesairosarus and the Drepanosauridae); 3) in the higher Pararchosauriformes (proterochampids, phytosaurs and chanaresuchids); and 4) the Euarchosauriformes (including crocodilians and birds and several prehistoric clades including dinosaurs).

antorbital fenestra

Figure 2. Click to enlarge. The four appearances of the antorbital fenestra in the Reptilia.

Antorbital fenestra means “the window anterior to the orbit [or eye socket]”. In certain taxa (euarchosauriforms and pararchosauriformes), the antorbital fenestra is deeper than the surface of the skull and lies in a bony depression called the antorbital fossa. Chroniosuchids and fenestrasaurs do not have this trait. Certain taxa have reduced the antorbital fenestra or have it entirely closed over.

The Function of the Antorbital Fenestra
Various hypotheses have been advanced regarding the function of the antorbital fenestra: 1) as a housing for a gland; 2) as a housing for pterygoideus musculature; 3) as a housing for an air-filled sac. Unfortunately most of the reptiles that ever had an antorbital fenestra are now extinct and in all living crocodilians the antorbital fenestra is closed over. However in birds the antorbital fossa houses a large air-filled diverticulum of the nasal cavity—the antorbital sinus. Thus the antorbital fenestra is associated with the nasal passage and likely housed an air-filled sac, thereby lightening the skull’s weight. Taxa that exhibit modifications of the nasal passage (adding a secondary palate, for instance) show reduction or loss of the antorbital fossa/fenestra. Rabbits, deer and certain extinct horses likewise have/had tiny antorbital fenestrae. Details and more references on the various hypotheses of origin and function can be found in Witmer (1987).

References:
Witmer LM 1987. The Nature of the Antorbital Fossa of Archosaurs: Shifting the Null Hypothesis. Fourth Symposium on Mesozoic Terrestrial Ecosystems, Short Papers Ed. by P.J. Currie and EH. Koster. online pdf

Wiki/Antorbital Fenestra

The Family Tree of the Pterosauria 8 – The Germanodactylus Clade

We just looked at the ramp up to Germanodactylus rhamphastinus. For a very long time we knew of only two Germanodactylus specimens, G. cristatus (the holotype) and G. rhamphastinus. Now we know of many more (Figure 1) not counting the many descendants. Some taxa within this clade have been assigned to other genera (Eosipterus, Elanodactylus). Others are known only by museum numbers (SMNK PAL 3830, MOZ 36325P). Still others are private specimens loaned to museums (SMNK PAL 6592, the BMM specimen). All this will require nomenclature revision at some time in the future.

Germanodactylus rhamphastinus
Germanodactylus rhamphastinus (Wagner 1851 B St AS I 745, No. 64 of Wellnhofer 1970) was the first of the raven-sized germanodactylids (Figure 1). No. 64 was derived from No. 23 and phylogenetically preceded Eosipterus and JME Moe 12. Distinct from No. 23, the skull of No. 64 was deeper anteriorly and crested posteriorly. The orbit was smaller with a V-shaped ventral margin. The teeth were larger and narrower. The jugal was narrower and deeper. The cervicals were longer and decreased in size cranially. The torso was reduced. The caudals were longer as a set, but most individual caudals remained short. The deltopectoral crest did not lean medially. The humerus was straight. The metacarpus was relatively longer. Fingers I-III were more robust and the unguals were larger. Manual 4.2 extended just to the elbow. The ischium was bifurcated. The prepubis was L-shaped. Pedal digit I was shorter. The unguals were smaller.

Following G. rhamphastinus the germanodactylids spread worldwide. Here they are presented in roughly phylogenetic order.

Germanodactylus and kin

Figure 1. Click to enlarge. Germanodactylus and kin.

Eosipterus
Eosipterus yangi (Ji and Ji 1997) GMV 2117 (not shown in Figure 1) was a headless specimen originally allied with Pterodactylus and Ctenochasma. Distinct from G. rhamphastinus, the humerus of Eosipeterus was shorter and slightly expanded distally. The deltopectoral crest was much larger. The metacarpus was shorter. Fingers 1-3 were smaller. Manual 4.2 extended beyond the elbow when the wing was folded. The ischium was expanded. Pedal unguals 2-4 were aligned transversely. The pedal digits were smaller.

Germanodactylus sp. JME/BSP specimen
The JME specimen of Germanodactylus (Rodriques, Kellner and Rauhut 2010) JME Moe12 (plate) BSP 1977 XIX 1 (counterplate). Distinct from G. rhamphastinus, the skull of JME Moe12 was much sharper with a relatively larger antorbital fenestra and orbit. No ossified crest jutted out from the cranium. The maxilla was slightly concave ventrally. The dentary was slightly convex dorsally to match it. The cervicals were more gracile. The torso was relatively longer. The caudals were reduced. The sternal complex, scapula and coracoid were all reduced. The forelimb was more gracile with smaller fingers. The metacarpus was shorter. Manual 4.1 was shorter than m4.2. The pubis and ischium were not sutured ventrally. The prepubis was shorter. The posterior process of the ilium was no longer than the posteriorly expanded ischium. The hindlimb was longer. The metatarsals and unguals were aligned transversely.

The family tree of Germanodactylus.

Figure 2. Click to enlarge. The family tree of Germanodactylus.

The BMM Germanodactylus
This privately held Late Jurassic pterosaur was on display at the Bürgermeister-Müller-Museum. In his blog Dr. David Hone mislabeled it a Pterodactylus and likewise an image of this specimen appears on the Wikipedia Pterodactylus page. Cladistic analysis (Figure 2) nests the BMM specimen in the middle of other Germanodactylus specimens. Overall it was nearly identical to MOZ 3625P (see below), but more robust. The foot of the BMM specimen is similar to that of  PAL 3830 with a large pedal 1.2 (the ungual) larger than p1.1. This pterosaur and MOZ 3625P (below) nest at the base of a split in the tree between the holotype Germanodactylus cristatus (and its crested tapejarid descendants) and the referred specimen SMNK 6592  (and its crested pteranodontid descendants).

MOZ 3625P
MOZ 3625P was originally considered an indeterminate pterodactyloid. Here it nests within the genus Germanodactylus. The MOZ 3625P skull is not known. Distinct from JME Moe12, the cervicals of MOZ 3625P were longer and more gracile. The humerus was more robust. The pubis and ischium were completely fused.

Germanodactylus cristatus
With the holotype for the genus, Germanodactylus cristatus B St 1892 IV 1 (Pterodactylus kochi Plieninger 1901, Germanodactylus cristatus Wiman 1925, No. 61 of Wellnhofer 1970) we move into another clade that continued the extremely sharp jawed morphology. The shoulder joint was shifted to the ventral torso, the so-callled “bottom-decker” wing placement. This clade included “Phobetor” in the Dsungaripteridae, Nemicolopterus in the Shenzhoupteridae and Tapejara in the Tapejaridae, to name just a few. No. 61 was also a sister to the long-legged super-clawed pterosaur, SMNK PAL 3830. Distinct from JME Moe 12, the skull of No. 61 was smaller overall and had an ossified rostral crest supporting a larger soft tissue crest. It had a cranial crest oriented posteriorly and posterior processes of the squamosal that formed “ears”. The premaxilla extended along the entire dorsal margin of the skull, including the cranial crest. The vomers were visible in lateral view. The premaxillary teeth were vestigial. The cervicals were longer. The caudals were more robust. The humerus was more robust with a longer deltopectoral crest. The metacarpus was longer. Fingers 1-3 were larger.

SMNK PAL 3830 – The Crato “Azhdarchid”
SMNK PAL 3830 (the Crato “azhdarchid” Frey & Tischlinger 2000) was originally considered an azhdarchid, like Quetzalcoatlus, probably due to its great size. Here it nests as a sister to Germanodactylus cristatus. Distinct from and twice the size of No. 61, fingers 1-3 of PAL 3830 were relatively larger. Manual digit 3 was longer than half the metacarpus and as long as the entire foot. The metacarpus was much more robust than manual 4.1. The foot, while appearing quite lethal, was actually much smaller relatively, reduced to about a third of the tibia. A small patella was present. The penultimate pedal phalanges were the longest in each series suggesting an arboreal habitat when not flying. It’s hard to imagine such claws ever touching the ground.

Elanodactylus
At the base of the other branch of germanodactylids is another oversized germanodactylid, Elanodactylus. Elanodactylus is known chiefly from wing material. Atypical for pterosaurs, manual 4.2 was longer than m4.1. The metacarpals were shorter than in other germanodactylids.  The neck vertebrae were considered similar to those of azhdarchids, but then germanodactylid neck vertebrae have not been well described because often they were often preserved exposed ventrally. Andres and Ji (2008) nested Elanodactylus with ctenochasmatids, but shifting it there adds 9 to 12 steps to the tree.

Germanodactylus sp. SMNK 6592
A private Germanodactylus, SMNK 6592, is basal to Eopteranodon, Pteranodon and Nyctosaurus (including Muzquizopteryx). Overall larger and distinct from the BMM specimen (above), the anterior tooth was larger and elevated to the directly anterior orientation creating a sharper snout that was longer than the mandible, as in Pteranodon. The rostral margin was straight and terminated in a small posteriorly-oriented parietal crest. The antorbital fenestra was larger. The rostrum was deeper. The sternal complex was larger with sharper corners. The deltopectoral crest was displaced distally, away from the proximal articular surface. The distal humerus was expanded. The hindlimbs were longer and more gracile.

Descendant taxa will be covered in future blogs.

A Summary
The genus Germanodactylus began with tiny pterosaurs provided with longer and sharper jaws. At three phylogenetic nodes the jaws became extremely sharp following rotation of the anterior tooth to an anterior orientation on both the upper and lower jaws. The size of this genus varied minimally, but Elanodactylus and the SMNK PAL 3830 specimen were larger than normal exceptions (not counting the very large descendants). Several Germanodactylus specimens had short hard crests that probably supported extensions of soft tissue. The manual fingers and claws of some germanodactylids were quite large and trenchant.

 

References:
Andres B and Ji Q 2008. A new pterosaur from the Liaoning Province of China, the phylogeny of the Pterodactyloidea, and convergence in their cervical vertebrae. Palaeontology51: 453–469.
Ji S-A and Ji Q 1997.
Discovery of a new pterosaur in Western Liaoning, China. Acta Geologica Sinica 71(1): 1-6 [in Chinese].
Rodrigues T, Kellner AWA and Rauhut OWM 2010. A New Specimen of the Archaeopterodactyloid Germanodactylus R[h]amphastinus. Acta Geoscientica Sinica 31(Supp. 1): 57-58.
Zhou C 2009. New material of Elanodactylus prolatus Andres & Ji, 2008 (Pterosauria: Pterodactyloidea) from the Early Cretaceous Yixian Formation of western Liaoning, China.Neues Jahr. Geo. Paläo. Abh. (DOI: 10.1127/0077-7749/2009/0022.)

Daemonosaurus a Plant Eater?

Updated February 28, 2015, with a revised skull for Daemonosaurus and an updated cladogram.

A Bizarre New “Theropod” Dinosaur was Recently Reported
Daemonosaurus (Sues et al., 2011) was named for its very large and wickedly curved fangs, quite beyond those of sister taxa like Eoraptor (Sereno et al. 1993) and Tawa. The skull was also unique…for a meat eater. So unique, in fact, that it’s closest comparisons in the large reptile tree were to plant eaters with premaxillary fangs (see below). Unfortunately, these two, Heterodontosaurus and Jeholosaurus were not included in the original phylogenetic analysis. We’ve seen a priori exclusion ruin other nestings, as in Vancleavea.

We remedy that oversight here.

Figure 2 Daemonosaurus skull in 4 views. The new reconstruction is narrower than previously with a new descending pterygoid flange and very few other refinements. The jaw is shorter. The dentary fang(s) appear to slip into that pmx/mx notch as in Heterodontosaurus. A small comb-like dentary tip appears to be a precursor for the predentary found in ornithischians. If this is an artifact, please provide data. Gray areas are unknown.

Figure 2 Daemonosaurus skull in 4 views.

The Daemonosaurus Story.
Dinosaur precursors, among the rauisuchia and basal archosauria, were all meat eaters. Vjushkovia, Decuriasuchus and Trialestes are examples. Basal dinosaurs (theropods), like Herrerasaurus and Eoraptor (see below) continued to eat meat. In pre-dinosaurs, like Turfanosuchus, the premaxilla sent out a process posterior to the naris. This was reduced in theropods, including Herrerasaurus, which has a traditional error in that area described here (and see below, note similarity to Eoraptor). This postnarial process is enlarged in ornithischians, like Lesothosaurus and Heterodontosaurus, and in paraornithischians, such as Silesaurus. The process is also enlarged in Daemonosaurus. In Massospondylus the great enlargement of the naris appears to have reduced the postnarial process.

Meat eaters have a long set of jaws. Daemonosaurus doesn’t.

The rostrum of Daemonosaurus is short and convex, as in Heterodontosaurus and Massospondylus (see below), not long and pointed, like a theropod. We could go on and on. Ask for the dataset.

Figure 1. Click to enlarge. Sisters to Daemonosaurus, including Leyesaurus and Jeholosaurus. The postfrontal (in light red) is not fused in most of these taxa (Heterodontosaurus is the exception), contra current dinosaur paradigms. Note the resemblance of Daemonosaurus to the basal sauropodomorph, Leyesaurus. The increase in tooth size in Daemonosaurus was not derived from theropods, but was a unique character trait, shared, more or less with its sister, Jeholosaurus and to a lesser extent in Heterodontosaurus.

Figure 2. Click to enlarge. Sisters to Daemonosaurus, including Leyesaurus and Jeholosaurus. The postfrontal (in light red) is not fused in most of these taxa (Heterodontosaurus is the exception), contra current dinosaur paradigms. Note the resemblance of Daemonosaurus to the basal sauropodomorph, Leyesaurus. The increase in tooth size in Daemonosaurus was not derived from theropods, but was a unique character trait, shared, more or less with its sister, Jeholosaurus and to a lesser extent in Heterodontosaurus.

Phylogenetic Analysis
The large tree of 238 (now 504) taxa nests Daemonosaurus at the base of the Ornithischia.

Figure 3. Portion of the large reptile tree focusing on dinosaurs and the nesting of Daemonosaurus

Figure 3. Portion of the large reptile tree focusing on dinosaurs and the nesting of Daemonosaurus

Daemonosaurus is the first dinosaur to link theropods with plant eaters.
It’s appearance in the Late Triassic appears to have been some sort of relic, because more derived plant-eaters were also present then.

I Have Never Seen the Original Fossil
So, once again, the use of DGS (Digital Graphic Segregation) AND a greatly enlarged dataset (see tree above) has enabled a more accurate nesting of a “bizarre” or “atypical” taxon than first-hand observation and a traditional small dataset, not yet validated by a larger set.

References:
Sereno PC, Forster CA, Rogers RR and Monetta AM 1993. Primitive dinosaur skeleton from Argentina and the early evolution of Dinosauria.
Sues H-D, Nesbitt SJ, Berman DS and Henrici AC 2011. A late-surviving basal theropod dinosaur from the latest Triassic of North America. Proceedings of the Royal Society Bpublished online 

Family Tree of the Pterosauria 6 – The Scaphognathia

In the earlier overview of the family tree of the Pterosauria, we looked at the basal split between the Dimorphodontia and the Eudimorphodontia. Within the latter, we just touched on the overlooked variety in Dorygnathus, which directly gave rise to two clades of “pterodactyloid”-grade clades: the azhdarchids and ctenochasmatids.

The Scaphognathia
A sister to Sordes and the Donau specimen of Dorygnathus branched off in a direction that would ultimately produce some small, unspectacular pterosaurs, some of the tiniest of all pterosaurs and two clades of the most spectacular crested pterosaurs. This is the Scaphognathia, named for the small, plain, unspectacular ScaphognathusPterorhynchus was at the base of the Scaphognathia.

Sordes, Pterorhynchus, Scaphognathus, Kunpengopterus and Darwinopterus.

Figure 2. Sordes, Pterorhynchus, Scaphognathus, Kunpengopterus and Darwinopterus.

Pterorhynchus – the Oddball
Pterorhynchus 
was like a big Dorygnathus with small teeth, a larger sternal complex and a much longer tail. Even though it nested between Sordes and ScaphognathusPterorhynchus had several derived traits not seen in either sister. The naris, for instance was reduced to a slit. Rather than having a single vane at the tip of its tail, Pterorhynchus had a series of vanes running down the length of its tail. Scaphognathus was more conservative, more like Sordes in overall morphology.

This is Where Darwinopterus Nests
Earlier analyses of mine nested the purported transitional taxon, Darwinopterus (Lü et al. 2009), with Elanodactylus between several Germanodactylus specimens, but new data from Pterorhynchus  and other pterosaurs changed things. Now Kunpengopterus (Wang et al. 2010) nests as a sister to Pterorhynchus at the base of the Darwinopterus/ Wukongopterus clade. The disappearance of the naris in Darwinopteruswas well underway in Pterorhynchus, which reduced the naris to a mere slit. The elongation of the skull (or rather the reduction of the orbit) also begins with PterorhynchusKunpengopterus did not have a larger skull, only a longer neck. Darwinopterus had a larger skull.

Scaphognathus – The Three Specimens
The holotype Scaphognathus  (Goldfuss 1830) GPIB 1304 (No. 109 of Wellnhofer 1975) gave rise to two smaller forms, both considered juveniles of Scaphognathus, even though they were morphologically distinct from the holotype and from each other.

The base of the Scaphognathia

Figure 3. Click to enlarge. The base of the Scaphognathia illustrating the size reduction that preceded the size increase in the transition from Scaphognathus to several later, larger "pterodactyloid"-grade clades.

The First Transition to the “Pterodactyloid” Grade
The smaller SMNS 59395 specimen of Scaphognathus was considered a juvenile by Bennett (2004) but it was morphologically distinct and a transitional taxon leading to the even smaller Ornithocephlaus BSPG 1971 I 17 (Soemmerring 1812-1817) Pterodactylus micronyx von Meyer 1856, No. 29 in the Wellnhofer (1970) catalog). Ornithocephalus was historically and mistakenly considered to be a “juvenile Pterodactylus,” but it was instead a close relative and a precursor taxon. If it was indeed a juvenile Pterodactylus, it would have looked more like the adult.

Preceding Germanodactylus
A series of smaller taxa, including Wellnhofer’s (1970) No. 9 and No. 6 (the smallest pterosaur known), led to a series of increasingly larger taxa, including Wellnhofer’s No. 12, No. 23 and No. 64 Germanodactylus.

Preceding Pterodactylus
Another series of tiny taxa, including Wellnhofer’s (1970) No. 9, No. 31 and Ninchengopterus led to No. 20 the most primitive Pterodactylus.

The Second Transition to the “Pterodactyloid” Grade
The other smaller Scaphognathus, the Maxberg specimen (no. 110 in the Wellnhofer 1975 catalog) phylogenetically preceded another series of tiny pterodactyloid-grade pterosaurs, including TM 13104, Gmu 10157 and Yixianopterus.

Preceding Ornithocheirids
Yixianopterus w
as a sister to the taxon that preceded ornithocheirids, like Haopterus, perhaps without a size shrinkage between them.

Preceding Cycnorhamphids
Yixianopterus was also a sister to the taxon that preceded cycnorhamphids via a size squeeze, with tiny BSp 1968 XV 132 and No. 30 phylogenetically preceding Cycnorhamphus and Feilongus.

No Single Transitional Taxon
Clearly there was no single “missing link,” and it was not Darwinopterus. Rather, four lineages all leading from Scaphognathus and two others leading from Dorygnathus provided all of the pterodactyloid-grade pterosaurs now known. These sequences also falsify Hone and Benton (2006) which claimed to support Cope’s Rule in the Pterosauria, but only after deleting the tiny pterosaurs.

Pterosaur family tree

Figure 4. Click to enlarge. The pterosaur family tree. The Scaphognathia are located at the top of the second (right) column.

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:
Bennett SC 2004. New information on the pterosaur Scaphognathus crassirostris and the pterosaurian cervical series. Journal of Vertebrate Paleontology, 24: 38A
Goldfuss GA 1830. Pterodactylus crassirostris. Isis von Oken, Jena pp. 552–553.
Hone and Benton 2006. Cope’s Rule in the Pterosauria, and differing perceptions of Cope’s Rule at different taxonomic levels. Journal of Evolutionary Biology 20(3): 1164–1170. doi: 10.1111/j.1420-9101.2006.01284.x
Lü J, Ji S, Yuan C, Gao Y, Sun Z and Ji Q 2006. New pterodactyloid pterosaur from the Lower Cretaceous Yixian Formation of Western Liaoning. In J. Lü, Y. Kobayashi, D. Huang, Y.-N. Lee (eds.), Papers from the 2005 Heyuan International Dinosaur Symposium. Geological Publishing House, Beijing 195-203.
Lü J, Unwin DM, Jin X, Liu Y and Ji Q 2009. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society London B  (DOI 10.1098/rspb.2009.1603.)
von Soemmering ST 1812. Über einen Ornithocephalus. – Denkschriften der Akademie der Wissenschaften München, Mathematischen-physikalischen Classe 3: 89-158.
von Soemmering ST 1817. Über einer Ornithocephalus brevirostris der Vorwelt. Denkschriften der Akademie der Wissenschaften München, Mathematischen-physikalischen Classe 6: 89-104.
Wagner JA 1851. Beschreibung einer neuen Art von Ornithocephalus nebst kritischer Vergleichung der in derk. Paläontologischen Sammlung zu München aufgestellten Arten aus dieser Gattung. Akademie der Wissenschaften Mathematischen-physikalischen Klasse6: 127–192 & pls 5–6.
Wang X, Kellner AWA, Jiang S-X, Cheng X, Meng Xi & Rodrigues T 2010. New long-tailed pterosaurs (Wukongopteridae) from western Liaoning, China. Anais da Academia Brasileira de Ciências 82 (4): 1045–1062.
Wellnhofer P 1970.
 Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.
Wellnhofer P 1975a.
 Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33.1975b. Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. 1975c. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149: 1-30.
Winkler TC 1870. Description d’un nouvel exemplaire de Pterodactylus micronyx du musee Teyler. Archives des Musee Teyler 3: 84-99.

 

The Family Tree of the Pterosauria 5 – Dorygnathus and its Spectacular Descendants

It would take a heretic to propose that Dorygnathus had anything to do with basal pterosaurs transitioning into “pterodactyloid”-grade pterosaurs. Yet, that’s exactly what this blog is all about.

The variety in Dorygnathus

Figure 1. Click to enlarge. The variety in specimens assigned to Dorygnathus. With other genera nesting within various specimens assigned to Dorygnathus, a renaming process will have to sort this out. Note the tiny pterosaurs at the end of each phylogenetic line.

According to tradition Dorygnathus was nothing more than a toothy oddity. Other than Padian (2009) relatively little has been written about this genus lately. So little attention has been paid to Dorygnathus that a certain worker (see below) confused it with Rhamphorhynchus.

Several paleontologists have already adopted Darwinopterus (Lü et al. 2009) as the best candidate taxon to bridge the former gap between the basal pterosaurs and the derived “pterodactyloids.” However, a larger and completely resolved cladistic analysis doesn’t support that smaller, poorly resolved tree. Earlier we learned that Darwinopterus nested within Pterorhynchus, which was already reducing the naris and elongating the skull and neck.

A larger cladistic analysis (see below) demonstrates that tiny pterosaurs were the real transitional taxa preceding at least four “pterodacyloid”-grade clades. At the base of two of these transitions we find Scaphognathus. At the base of Scaphognathus and the other two transitions we find Dorygnathus and Sordes.

Now you know why Dorygnathus is so important.

Dorygnathus is the Key.
There is an overlooked variety in several specimens of Dorygnathus (see above) that was revealed after reconstruction and cladistic analysis. Unfortunately, no prior analyses attempted to include or reconstruct more than one specimen from Dorygnathus and so overlooked this variety and its phylogenetic significance.

Two  Basal Dorygnathus Specimens Are Outgroups to the First Split
The Donau specimen (private) nested as the most basal Dorygnathus. Sordes is the outgroup taxon. The neck, tail and torso were longer in Dorygnathus than in Sordes. The teeth were larger and more widely spaced on longer jaws.

Next in line and at the base of its own split is the extremely toothy (almost tusky) specimen, SMNS 51827, perhaps the classic Dorygnathus. Were those giant teeth useful? Or just for show? Fingers 1-3 were greatly enlarged, rivaling the entire foot in size. The entire wing was more robust, but the sternal complex remained small.

The Azhdarchid Lineage Arising from Certain Dorygnathus Specimens
Following the two basal taxa, Dorygnathus splits into two major branches. The first ultimately produced azhdarchids. The second produced ctenochasmatids.

Derived from the SMNS 51827 specimen, the SMNS 50164 specimen of Dorygnathus (Figure 1) had a longer rostrum and smaller teeth. It also had shorter wings and enormous fingers. This specimen is the last of the long, stiff-tailed types. The skull was ~13 cm in length.

Proto-azhdarchid lineage

Figure 2. Click to enlarge. The SMNS 50164 specimen of Dorygnathus and its proto-azhdarchid descendants.

The Transition to the “Pterodactyloid” Grade
An important size reduction marks the appearance of tiny TM 10341At less than 10 cm from snout to vent it was shorter than just the skull of its phylogenetic predecessor, SMNS 50164 (above). Looking like a miniature SMNS 50164, TM 10341 had smaller teeth, smaller fingers, a smaller tail and a larger prepubis and pelvis. Wellnhofer (1970) cataloged it as Pterodactylus spectabilisa juvenile pterodactyloid even though the metacarpus was not relatively larger. Rather the antebrachium (radius and ulna) were relatively much smaller. This tiny taxon gave rise to several long-necked, long legged pterosaurs with metacarpals longer than the antebrachium, beginning with Beipiaopterus and including Huanhepterusazhdarchids and the flightless pterosaur, SoS 2428.

The protoctenochasmatids arising from Dorygnathus

Figure 3. Click to enlarge. The protoctenochasmatids arising from certain specimens of Dorygnathus. Note the tiny taxa following Angustinaripterus.

The Ctenochasmatid Lineage Arising from other Dorygnathus Specimens
Getting back to the base of Dorygnathus, two new genera, Fenghuangopterus and Cacibuteryxnest between the SMNS 51827 specimen and the SMNS 55886 specimen of Dorygnathus. Either these two need to be renamed as species of Dorygnathus or certain Dorygnathus specimens need to be renamed as new genera.

The R156 specimen followed. Long, procumbent teeth may have reached an acme with this specimen.

Several skull only specimens followed, including D. purdoni, Harpactognathus and Augustinaripterus. Sericipterus, may also nest here according to Andres et al. (2010).

Another Transition to the “Pterodactyloid” Grade
A drastic size reduction occured next, with the St/Ei I specimen wrongly attributed to Pterodactylus micronyx  and the holotype of Pterodactylus micronyx, The Pester specimen, wrongly attributed to Pterodactylus. The former had a snout-vent length of 5 cm and had a relatively shorter rostrum.The relatively longer metacarpus and shorter tail marked this specimen as a “juvenile pterodactyloid,” but other traits nest it here, at the base of the Ctenochasmatidae. Larger ctenochamatids with a longer rostrum include Gnathosaurus, Ctenochasma and Pterodaustro, the last of this lineage. An evolutionary sequence of skulls is laid out here for ready reference.

Pterosaur family tree

Figure 4. Click to enlarge. Dorygnathus nests in the left column of the pterosaur family tree at the base of the Ctenochasmatidae and the Azhdarchidae.

The Scaphognathid Clade.
The sisters of Sordes and the Donau specimen of Dorygnathus also branched off in a third direction that included Pterorhynchus and Scaphognathus. We will look at those lines in the near future.

As documented here, there was no single “missing link,” and it was not Darwinopterus. Rather, convergent size reductions in four lineages all leading to Dorygnathus provided all of the pterodactyloid-grade pterosaurs now known.

Mistaken Identity
Not all long-tailed pterosaurs with big teeth belong to Dorygnathus. Dr. David Hone mistook a model Rhamphorhynchus for a Dorygnathus, but generally Dorygnathus had a more robust skeleton, a tiny triangular sternum, a shorter first phalanx of the wing finger (that did not reach the elbow), thicker teeth and a broader mandible, among other details.

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:
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. doi:10.1080/02724630903409220.
Bennett SC 2004. 
New information on the pterosaur Scaphognathus crassirostris and the pterosaurian cervical series. Journal of Vertebrate Paleontology, 24: 38A
Lü J, Unwin DM, Jin X, Liu Y and Ji Q 2009
.
Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society London B  (DOI 10.1098/rspb.2009.1603.)
Padian K 2009.
 The Early Jurassic Pterosaur Dorygnathus banthenis (Theodori, 1830) and The Early Jurassic Pterosaur Campylognathoides Strand, 1928, Special Papers in Paleontology 80, Blackwell ISBN 9781405192248
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.
Wellnhofer P 1975a. Teil I. Die Rhamphorhynchoidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Allgemeine Skelettmorphologie. Paleontographica A 148: 1-33.1975b. Teil II. Systematische Beschreibung. Paleontographica A 148: 132-186. 1975c. Teil III. Paläokolgie und Stammesgeschichte. Palaeontographica 149: 1-30.

Darwinopterus, NOT the Transitional Pterosaur

Google Darwinopterus and you’ll get entries like: “the remarkable transitional pterosaur,” “one hell of an intermediate,” “fills evolution gap.” The news has been out for awhile now. Darwinopterus (Figure 1) has been hailed as the long lost transitional taxon bridging the basal long-tailed pterosaurs and the later short-tailed pterosaurs.

Or was it?

Pterosaurs, the flying reptiles of the Mesozoic, have been known for over 200 years, but until recently no taxon has been put forth as the transitional “link” between the primitive short-handed, long-tailed forms and the more derived long-handed, short-tailed ones. Lü et al. (2009) claimed to fill that gap with an unusual pterosaur, Darwinopterus modularis, which appeared to combine traits from both groups.

The skull and neck were described as “typically pterodactyloid,” while the remainder of the skeleton was considered “identical to that of basal pterosaurs.” This specimen was used to support the hypothesis of “modular evolution” in which the transition from basal to derived pterosaurs was posited to proceed in two phases: (1) skull and neck followed by  (2) post-cervical axial column, limb girdles and limbs.

Darwinopterids

Figure 1. Click to enlarge. Some of the several Darwinopterus specimens now known.

Four big problems arose from the Lü et al. (2009) study: 
1.The cladistic results were not robust. There were no distinct sister taxa and there was a great loss of resolution at the Darwinopterus node. No sequence of basal taxa in the Lü et al. (2009) analysis documented a gradual accumulation of Darwinopterus characters. Instead, four proximal sister taxa nested in an unresolved clade and one of those included four sister taxa in an unresolved clade. Similarly, three derived clades without resolution nested as sisters. A fine mess! And not the way evolution works!

2. The gamut of included taxa was not sufficiently broad ( = inclusive) to recover a single tree result matching evolution’s own single tree. Instead 500,000+ trees were recovered! Such loss of resolution provides little to no recoverable data. Missing from the inclusion set were all the tiny pterosaurs (skulls smaller than 2 cm in length, Figure 3) because they were traditionally considered juveniles and thus unworthy of inclusion. Also missing were several specimens considered congeneric with others but were distinct in several regards.

3. Evolution does not otherwise proceed in modules. Most fossil vertebrates can be identified by just a skull, tooth, pes or pelvis, but “modular evolution” would play havoc with this, creating chimaeras with the head of one taxon on the torso of another, as imagined in Darwinopterus by Lü et al. (2009). There is another, more parsimonious, explanation (see below).

4. Lü et al. (2009) used more than one specimen to score Darwinopterus, Scaphognathus and other pterosaurs. In Darwinopterus, the YH skull was a third longer with a larger antorbital fenestra, smaller orbit and deeper skull. Such characters change scores. Lü et al. (2009) also incorrectly scored several taxa (details on request).

Here’s how to solve all four problems at once:
Increase the size of the cladistic study inclusion set (Figure 4).

I added Darwinopterus to a cladistic analysis of 170 taxa (152 pterosaurs + 18 outgroup taxa, Figure 4)). These were tested against 185 characters. That analysis employed three times the number of taxa employed by Lü et al. (2009) against fifty percent more characters. While the Lü et al. (2009) resulted in 500,000+ trees, my analysis recovered a single tree in which there was not one, but four “pterodactyloid”-grade clades (not including the darwinopterids/wukongopterids). Completely unexpected, but it makes sense when you look at the details in each of the lineages. This new family tree goes a long way to explaining many of the mysteries surrounding pterosaurs.

Darwinopterus and kin nesting between Sordes and Scaphognathus

Figure 2. Nesting between Sordes and Scaphognathus were Pterorhynchus, Kunpengopterus, Darwinopterus and Wukongopterus (not shown), taxa with a longer skull, a longer neck and a reduced to absent naris..

Darwinopterus nested as the sister to Wukongopterus (Wang et al. 2009). Both nested as sisters to Kunpengopterus (Wang et al. 2010) and Pterorhynchus (Czerkas and Ji 2002). This clade nested between Sordes and Scaphognathus (Figure 2.), far from any of the actual transitional pterosaurs (see below). Lü et al. (2009) included Pterorhynchus in their analysis, but they did not score 27 percent of the characters. Of the remaining 80 characters 19 were scored differently in Darwinopterus and Pterorhynchus. Of these 19, I found 10 scores to be valid. Two of these described the longer rostrum in Darwinopterus. Three described the absence of a distinct naris in Darwinopterus. Of the remaining 9 characters all were incorrectly scored. (Details on available on request.)

The Actual Transitional Taxa
There were four transitional lineages (see below and Figure 4) that produced four convergent clades of “pterodactyloid”-grade pterosaurs, none of which came close to including Darwinopterus. At the bases of the four pterodactyloid-grade clades were four separate series of tiny pterosaurs, smaller than their predecessors and smaller than their successors. Each sequence documented a gradual transition from basal to derived.  Two arose from distinct Dorygnathus specimens. Two arose from the small Scaphognathus specimens (Figure 3).

The descendants of Scaphognathus.

Figure 3. Click to enlarge. The descendants of Scaphognathus. Note the size reduction followed by a size increase.

The widely-held hypothesis that small, short-rostrum pterosaurs were juveniles of larger forms is falsified by this study. Those tiny pterosaurs had a short rostrum because their ancestors within Scaphognathus also had a short rostrum. Other tiny pterosaurs did not have a short rostrum. They were basal to other clades leading to the azhdarchids and to the ctenochasmatids. If the tiny pterosaurs were juveniles, they should have nested with their parents, as in Pterodaustro.

Remember: pterosaurs were derived from a clade of lizards that grew isometrically, not allometrically. Juveniles were close matches to adults. This is never more clear than when looking at pterosaur embryos here, here and here. Even the Darwinopterus embryo was the spitting image of its mom, with a long rostrum and tiny eyes.

Pterosaur family tree

Figure 4. Click to enlarge. The family tree of the Pterosauria.

Other pterosaurs also had tiny transitional taxa. Between Campylognathoides and Rhamphorhynchussize reduction is documented. Preceding Nyctosaurus and Pteranodon a small taxon appears.

The fact that pterosaurs reduced their size during morphological transitions indicates that size reduction was a survival technique producing new morphologies (and sizes!) to keep genetic lineages from going extinct. Eudimorphodontids, dimorphododontids, dorygnathids, campylognathids and rhamphorhynchids did not survive into the Cretaceous, but their reduced descendants did. Thereafter size increases created some of the most spectacular forms now known. The tiny scaphognathids and dorygnathids were their common ancestors. This new heretical hypothesis of pterosaur relations plays havoc with traditional hypotheses, including the one invoking Cope’s rule by Hone and Benton (2007).

So what was Darwinopterus, if not a transitional pterosaur?
Sadly, Darwinopterus and Wukongopterus produced no known descendants. They were derived pterorhynchids about the same size as others. In the context of their phylogenetic nesting, both Darwinopterus and Wukongopterus inherited their so-called “basal” traits from a sister to Pterorhynchus, which also had a rather short metacarpus, long tail, long pedal digit 5 and long tail. The elongation of the skull and reduction of the naris were well underway in Pterorhynchus. The elongation of the neck was relatively slight. These traits were convergent with those in “pterodactyloid”-grade pterosaurs. A sister taxon, Wukongopterus, did not have an elongated neck. Kunpengopterus had a longer neck, but not an elongated skull (see above).

As always, I encourage readers to see the 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:
Czerkas SA and Ji Q 2002. A new rhamphorhynchoid with a headcrest and complex integumentary structures. In: Czerkas SJ ed. Feathered Dinosaurs and the Origin of Flight. The Dinosaur Museum:Blanding, Utah, 15-41. ISBN 1-93207-501-1. 
Hone and Benton 2006. Cope’s Rule in the Pterosauria, and differing perceptions of Cope’s Rule at different taxonomic levels. Journal of Evolutionary Biology 20(3): 1164–1170. doi: 10.1111/j.1420-9101.2006.01284.x
Lü J, Unwin DM, Jin X, Liu Y and Ji Q 2009. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceedings of the Royal Society London B  (DOI 10.1098/rspb.2009.1603.)
Lü J, Unwin DM, Deeming DC, Jin X, Liu Y and Ji Q 2011a. An egg-adult association, gender, and reproduction in pterosaurs. Science, 331(6015): 321-324. doi:10.1126/science.1197323
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
Wang X, Kellner AWA, Jiang S and Meng X 2009. An unusual long-tailed pterosaur with elongated neck from western Liaoning of China. Anais da Academia Brasileira de Ciências 81 (4): 793–812.
Wang X, Kellner AWA, Jiang S-X, Cheng X, Meng Xi & Rodrigues T 2010. New long-tailed pterosaurs (Wukongopteridae) from western Liaoning, China. Anais da Academia Brasileira de Ciências 82 (4): 1045–1062.
Zhou C 2009. New material of Elanodactylus prolatus Andres & Ji, 2008 (Pterosauria: Pterodactyloidea) from the Early Cretaceous Yixian Formation of western Liaoning, China.Neues Jahr. Geo. Paläo. Abh. (DOI: 10.1127/0077-7749/2009/0022.)