Bat Origins and DNA

Updated September 30, 2016 with the addition of taxa to the LRT and new data on Protictis.

Where DO Bats Nest? The Question Returns.
A renowned (unnamed) professor interested in the origin of bats questioned my morphological nesting of bats with Ptilocercus and Nandinia (among living taxa) and Palaechthon (among fossil taxa). The professor sent me a pdf of Meredith et al. (2011), the most recent DNA tree to lump and split living mammals, as his best hypothesis on bat origins.

Bats and their sisters

Figure 1. Bats and their sisters according to Meredith et al. 2011.

Mammal Diversification
Meredith et al. (2011) sought diversification patterns and times in mammals. They constructed a molecular supermatrix for mammalian families and analyzed these data with likelihood-based methods and relaxed molecular clocks. Their results came in traditionally, with Monotremata, Marsupialia and Placentalia at the base. The latter was divided into Xenartha + Afrotheria and all other placentals, which were divided into Laurasiatheria and Euarchontoglires.

DNA Results for Bats
Lots of bats were tested and they all lumped together in a single clade subdivided into three with fruit bats (Fig. 1 in orange) separating two microbat clades (in blue and green). Bats appeared as the unresolved sisters to Carnivora and Artiodactylia. Basal insectivores (not shown hre) nested as outgroup taxa to this super clade.

That’s an overly general nesting for bats that doesn’t provide much insight. On the other hand, I wasn’t surprised to see bats nesting so close to basal carnivores, like Nandinia and the vivverids, because the morphological results recovered the same relationship. I was surprised to bats nesting close to rhinos and camels.  :-) Pangolins are indeed close to bats, so we agree here (Fig. 2).

Figure 2. Bat origins cladogram. Here Onychonycteris and Pteropus represent bats.

Figure 2. Bat origins cladogram. Here Onychonycteris and Pteropus represent bats.

DNA Results for Flying Lemurs
The base of the Euarchontoglires (Meredith et al. 2011, not shown in Fig. 1) included tree shrews and demopterans. I wasn’t surprised to see rabbits nesting close to Tupaia, the common tree shrew, because the morphological results recovered the same relationship. I also wasn’t surprised to see Ptilocercus, the pen-tailed tree shrew, nesting close to the flying lemurs, because the morphological results recovered the same relationship. Note these taxa didn’t nest with bats in the DNA study, but they did all nest at or near their unresolved common base.

Figure 2. Known bat ancestors to scale. Click to enlarge.

Figure 2. Known bat ancestors to scale. Click to enlarge.

Morphological Results
The Meredith et al. (2011) results do not match the morphological evidence, which derives both bats and flying lemurs from a sister to Ptilocercus, a Paleocene pro primate and Chriacus, all close to basal carnivorans like NandiniaNandinia is a living carnivore that sometimes drops from trees and has an omniovorous diet. Chriacus was a long-legged tree-dwelling omnivore. Phylogenetic bracketing indicates that post-cranial characters were something like Chriacus and/or PtilocercusPtilocercus is a flying lemur ancestor, but shares with bats several characters including flat ribs, a high floating scapula, wide cervicals, a rotating carpus and metatarsal + phalanx ratio similarities.

The question is…
why don’t the DNA results more closely match the morphological results, and vice versa?

DNA results cannot include fossil taxa. With bats evolving prior to the Eocene (52 mya), fossil taxa are necessary in any study on bat evolution.

The DNA of modern tree shrews and bats, etc. is not the same as the DNA of Paleocene tree shrews and bats, etc.

The Meredith et al. (2011) evidence indicates that DNA results for large clades of mammals  cannot resolve large clades. DNA and amino acid results do not agree with one another in the case of large reptile clades and the same is true in large mammal clades. DNA and amino acids apparently become more useful the more closely taxa are related. The resolution is very high, for instance, in human DNA, which is why it can be used in criminal investigations.

On the Other Hand
In fossil evidence you can point to a long list or suite of homologous morphologies, from tooth cusps to phalanx ratios. DNA results cannot provides these details. Morphology will always trump DNA, especially when bats nest with camels in DNA studies. DNA can only be verified with morphological evidence. DNA results can guide our efforts but the bottom line is morphology. The Meredith et al. (2011) study was unable to provide a specific sister taxon to bats. The morphological study provided Chriacus. When closer sisters are discovered, they will be reported.

Dermopterans and Bats
Flying lemurs nested close to bats and bat babys have short fingers like those of flying lemurs. Problem is: Ptilocercus, which comes between the two, has no extradermal membranes or webbed fingers and its limbs are not elongated. I have no answers for that other than both bats and flying lemurs are about 60 million years old and likely had a common long-limbed ancestor with extradermal membranes in a sister to Ptilocercus. Or bats and flying lemurs both developed extradermal membranes by convergence. Or Ptilocercus lost its ancestral long limbs and membranes.

Can we trust results?
In science we don’t trust anything. Not DNA. Not morphology. Everything is tentative and provisional.

 

References
Meredith RW et al. 2011. Impacts of the Cretaceous Terrestrial Revolution and KPg Extinction on Mammal Diversification. Science 334:521-524.

Build Your Own Paper Elasmosaur, Thalassomedon!

Click to access 2 page Thalassomedon model pdf file

Click to download a two-page Thalassomedon paper model pdf file

Download the pdf. Print out on 8.5×11 “cover stock” paper.
Cut out the pieces. Fold them as instructed. Glue them together.
Tape piano wire along the neck if you don’t want it to curl and droop.
Hang on thread.

Enjoy!

From your friend at The Pterosaur Heresies.

Thanks for coming back.

Pampadromaeus, Bridging the Theropod – Phytodinosaur Transition

Pampadromaeus barberenai 
Pampadromaeus barberenai
 (Cabriera et al. 2011) is a new dinosaur from the Late Triassic of Brazil. It was originally described as a stem sauropodomorph known from a partial disarticulated skeleton and most of the skull bones. The authors reported, “Based on four phylogenetic analyses, the new dinosaur fits consistently on the sauropodomorph stem, but lacks several typical features of sauropodomorphs, showing dinosaur plesiomorphies together with some neotheropod traits.”

Pampadromaeus in left lateral view.

Figure 1. Pampadromaeus in left lateral view. The skeleton was disarticulated and semi-complete.

Pampadromaeus was small (slightly longer than a meter in length) biped with a generalized basal dinosaur morphology, not quite a theropod and not quite a phytodinosaur (sauropods + ornithisuchians + pseudornithisichians).

The skull of Pampadromaeus

Figure 2. The skull of Pampadromaeus as it was originally reconstructed. Upper left: The skull of Eoraptor for comparison. To the left, images of the premaxilla and maxilla restored. Note the length of the premaxillary teeth and their proximal exposure. The newly mated premaxilla does not descend so much as in the original reconstruction.

Generalized Morphologies Generally Make for Great Transitional Taxa
Cabriera et al. (2011) added Pampadromaeus to four prior studies and in each case Pampadromaeus nested as a sister to Sauropodomorpha or as a sister to Saturnalia + Sauropodomorpha. Only ten taxa were included in each test. In each study Silesaurus + Ornithischia were outgroup taxa.

I added just the skull elements to the large reptile study (Fig. 3) and found it nested between members of the Theropoda and the Phytodinosauria, basal to its basalmost member, Daemonosaurus. Daemonosaurus was not included in the Cabriera et al. (2011) study based on prior studies. This nesting agrees with the Cabriera et al. (2011) results, but the expansion of the taxon list (Fig. 3) sheds more light on the nesting of this new and phylogenetically important dinosaur.

 the nesting site of Pampadromaeus

Figure 3. A portion of the large reptile tree indicating the nesting site of Pampadromaeus. Click to see the entire tree.

This is an Important Genus
Pampadromaeus is a key taxon linking theropods to all other dinosaurs, the herbivorous Phytodinosauria via Daemonosaurus. The enlargement of the premaxillary teeth observed in Daemonosaurus has its genesis in Pampadromaeus. The torso was shorter than in Saturnalia. The ilium resembled that of Herrerasaurus and Sanjuansaurus. The dorsal spines were lower than in Herrerasaurus. More detailed comparison can be found in Cabriera et al. (2011).

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
Cabreira SF, Schultz CL, Bittencourt JS, Soares MB, Fortier DC, Silva LR and Langer MC 2011. New stem-sauropodomorph (Dinosauria, Saurischia) from the Triassic of Brazil. Naturwissenschaften (advance online publication) DOI: 10.1007/s00114-011-0858-0

Did Dimorphodon Have an External Mandibular Fenestra?

Updated July 6, 2015 with better data on BSp 1994 (Austriadraco). 

A Mandibular Fenestra in Pterosaurs?
Nesbitt and Hone (2010) and Nesbitt (2011) proposed an external mandibular fenestra for three and only three pterosaurs, recognizing that a mandibular fenestra is not found in other pterosaurs. These two workers nested pterosaurs with archosaurs to support their traditional view despite the fact that pterosaurs do not otherwise resemble any other archosaurs. To do this they excluded the heretical sisters of pterosaurs found in the large study. To be fair, Hone and Benton (2007, 2008) did include Cosesaurus in their analysis, but only a quarter of the characters were employed, despite the fact that Cosesaurus is complete and articulated.

Let’s take a closer look
at each pterosaur taxon used by Nesbitt and Hone (2010) in evidence for the mandibular fenestra.

The BMNH 4212 Specimen of Dimorphodon
According to Nesbitt and Hone (2010) and Nesbitt (2011) the mandible of the BMNH 4212 specimen of Dimorphodon has a mandibular fenestra. The matrix appears within a very large hole in the posterior mandible. The surangular is apparently missing because it is not identified in figure 1 (below) from Nesbitt and Hone (2010). The BMNH 4212 specimen also sports a very deep jugal, according to  Nesbitt and Hone (2010), a trait not found in any other pterosaur or any other Dimorphodon.

The purported deep jugal and mandibular fenestra in the BMNH specimen of Dimorphodon.

Figure 1. From Nesbitt and Hone (2010), the purported deep jugal and mandibular fenestra in the BMNH specimen of Dimorphodon. emf = external mandibular fenestra. im = impression of emf. j = jugal.

The Mary Anning Specimen
In counterpoint, the Mary Anning specimen (Fig. 2) preserves the surangular in place, covering the Nesbitt and Hone (2010) “fenestra” completely. The Anning Dimorphodon has no mandibular fenestra and no deep jugal flange.

The Mary Anning Dimorphodon skull.

Figure 2. The Mary Anning Dimorphodon skull R1034a. Note the mandible has no mandibular fenestra.

Sure It Looks Like a Mandibular Fenestra…
Figure 3 portrays the BMNH 4212 specimen of Dimorphodon after DGS (digital graphic segregation). Here every bone has been color coded to improve understanding. I have not seen the fossil first hand. I reconstructed the bones in accord with other sister taxa (Fig. 3 middle). The articular bone (in gray) might be missing and replaced here with a best guess shape. If present the articular bone may be present in the area outlined in gray posterior to the mandible.

The skull of Dimorphodon macronyx BMNH 41212.

Figure 3. The skull of Dimorphodon macronyx BMNH 41212. Above: in situ. Middle: Restored. Below: Palatal view.

Reconstruction Really Helps
Evidently Nesbitt and Hone (2010) and Nesbitt (2011) did not realize the surangular had drifted dorsally in BMNH 4212. What they considered the angular was actually a displaced pterygoid (or perhaps the articular since both have the same shape, see figure 4). Such mistakes are easy to make when tracing a specimen with little attention to detail (Fig. 1).

Figure 4. The mandibles of Eudimorphodon with mandible elements identified. Note the breakage of the left dentary and displacement of the left surangular to produce the illusion of a mandibular fenestra not duplicated in the right mandible. A rod-shaped element, likely a hyoid or pterygoid, produces the illusion of a dorsal rim to the right posterior mandible. 

Figure 4. The mandibles of Eudimorphodon with mandible elements identified. Note the breakage of the left dentary and displacement of the left surangular to produce the illusion of a mandibular fenestra not duplicated in the right mandible. A rod-shaped element, likely a hyoid or pterygoid, produces the illusion of a dorsal rim to the right posterior mandible. Drawings from Wild 1978.

Eudimorphodon ranzii Mandibles
The holotype of Eudimorphodon (Zambelli 1973) Upper Norian, Late Triassic, ~203 mya MCSNB 2888 provides both lateral and medial views of complete and largely articulated mandibles. Here the shapes of the posterior elements resemble those found in lizards with an articular bone extending anteriorly. There is an opening between the left dentary and surangular, but that is due to the downshifting of the surangular and the breakage of the dentary not duplicated on the right mandible. When properly reconstructed, no mandibular fenestra is present despite the fact that Eudimorphodon lived tens of millions of years earlier than Dimorphodon, closer to the origin of the Pterosauria. No genuine pterosaur precursor among the fenestrasaurs (Cosesaurus, Sharovipteryx and Longisquama) had a mandibular fenestra.

The mandible of Eudimorphodon 1994 I51

Figure 5. The mandible of Eudimorphodon 1994 I51. Top: After DGS the various points of decay and displacement appear as white spots. The jaw tip is missing. Rod-like elements are in blue and green. Displaced plate-like elements in beige. The green coronoid has been displaced posteriorly. The surangular (dark brown) has been displaced. Note the angular of Eudimorphodon ranzii (Fig. 4) is not as deep as portrayed by Nesbitt and Hone (2010, bottom).

Eudimorphdon BSP 1994 I51
The second specimen reported by Nesbitt and Hone (2010) to have a mandibular fenestra is Eudimorphodon BSP 1994 I51, an incomplete and disarticulated mandible. Here (Fig. 5) the mandible has decayed somewhat with several fenestra apparent throughout. Sure the matrix appears at the appropriate part of the mandible in which a mandibular fenestra might appear, but It’s not a convincing example due to element shifting and decay. Parts of the inside of the mandible are exposed by the flaking off of bone. The reported angular is much too deep. The coronoid has drifted posteriorly. No other pterosaur has a dorsal bump on the posterior mandible and the coronoid is otherwise missing. That posterior bump is the coronoid.

Better data 
(Fig. 5b) arrived that may help decide whether or not that extra bone posterior to the coronoid was the metaphorical lid for the hole seen in the mandible of BSp 1994 — and whether or not the mandible is preserved in medial or lateral view. 

Figure 1. Austriadraco, BSp 1994 I51, a Triassic pterosaur mandible. Is it exposed in medial view or lateral view? Below the line is Eudimorphodon, which preserves mandibles in lateral and medial view. Which one is more similar to Austriadraco? You decide. Click to enlarge. Also note the tiny mandibular fenestra in the lateral view of Eudimorphodon not replicated on the medial view and apparently caused by a shift in the covering bone. Arrow points to apparent broken strip of bone that would otherwise have made the long light blue bone continuous.

Figure 1. Austriadraco, BSp 1994 I51, a Triassic pterosaur mandible. Is it exposed in medial view or lateral view? Below the line is Eudimorphodon, which preserves mandibles in lateral and medial view. Which one is more similar to Austriadraco? You decide. Click to enlarge. Also note the tiny mandibular fenestra in the lateral view of Eudimorphodon not replicated on the medial view and apparently caused by a shift in the covering bone. Arrow points to apparent broken strip of bone that would otherwise have made the long light blue bone continuous.

BMNH 43486
The third mandible is the BMNH 43486 specimen of Dimorphodon (Fig. 6). This mandible is more damaged than the others and so does not induce confidence that the external mandibular fenestra (emf) was real or just due to damage. The opening appears much further posteriorly than the dentary/surangular interface. If valid, one should wonder why other sister pterosaurs do not have even a small mandibular fenestra.

The BMNH 43486 specimen of Dimorphodon.

Figure 6. The BMNH 43486 specimen of Dimorphodon. Damage to the posterior portion of the mandible accounts for the apparent fenestra. What Nesbitt and Hone labeled the Meckelian groove (mg) may instead by the other mandibular rim.

It All Comes Down to Autapomorphies
If no other pterosaur sisters had a deep jugal and if no other pterosaur sisters had a mandibular fenestra, then maybe the two autapomorphies reported by Nesbitt and Hone (2010) are wrong. In BMNH 4211 re-identifying the bottom half of the “deep jugal” as the missing surangular solves the twin problems on the best example.

If anyone finds a valid external mandibular fenestra or deep jugal on any pterosaur specimen, please bring it to my attention. I’d like to see it.

As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.

Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.

References
Buckland W 1829. Proceedings of the Geological Society London, 1: 127
Owen R 1859. On a new genus (Dimorphodon) of pterodactyle, with remarks on the geological distribution of flying reptiles.” Rep. Br. Ass. Advmnt Sci., 28 (1858): 97–103.
Nesbitt SJ 2011.  The early evolution of archosaurs: relationships and the origin of major clades.  Bulletin of the American Museum of Natural History 352: 292 pp. online pdf
Nesbitt SJ and Hone DWE 2010. An external mandibular fenestra and other archosauriform character states in basal pterosaurs. Palaeodiversity 3: 225–233
Padian K 1983. Osteology and functional morphology of Dimorphodon macronyx (Buckland) (Pterosauria: Rhamphorhynchoidea) based on new material in the Yale Peabody Museum, Postilla, 189: 1-44.
Sangster S 2001. Anatomy, functional morphology and systematics of Dimorphodon. Strata 11: 87-88
Wild R 1978. Die Flugsaurier (Reptilia, Pterosauria) aus der Oberen Trias von Cene bei Bergamo, Italien. Bolletino della Societa Paleontologica Italiana 17(2): 176–256.
Zambelli R 1973. Eudimorphodon ranzii gen.nov., sp.nov. Uno Pterosauro Triassico. Rendiconti Instituto Lombardo Accademia, (rend. sc.) 107: 27-32.

wiki/Dimorphodon

What is Azendohsaurus?

Updated May 15, 2015 to reflect the new nesting of Azendohsaurus back with Trilphosaurus.

Azendohsaurus has bounced around the reptile family tree.
Azendohsaurus was originally described by Dutuit (1972) as an ornithischian dinosaur on the basis of two teeth and a dentary fragment. Gauffre (1993) found a bit more of the dentary and described Azendohsaurus as a prosauropod. Flynn et al. (2010) found a relatively complete skeleton in Madagascar, but only the skull has been published to date. Flynn et al. (2010) considered Azendohsaurus the “nearest archosauromorph outgroup to the archosauriformes (but then they also ascribe to the false nesting of Trilophosaurus and rhynchosaurs as sisters to Archosauriformes).

Figure 1. The skull and palate of Azendohsaurus, a sister to Trilophosaurus. 

Figure 1. The skull and palate of Azendohsaurus, a sister to Trilophosaurus.

Nesting Azendohsaurus on The Large Reptile Family Tree
Here, phylogenetic analysis nests Azendohsaurus with Trilophosaurus, a lepidosaur (Fig. 2).

Figure 2. DGS applied to the skull of Azendohsaurus. Note the new addition of a lateral naris, not previously noted.

Figure 2. DGS applied to the skull of Azendohsaurus. Note the new addition of a lateral naris, not previously noted. Compared to sister taxa, both the ascending processes of the premaxilla and maxilla are very tall. 

Teeth
In Trilophosaurus two rows of teeth are present but fused to form wide teeth with two roots. Azendohsaurus is similar with two rows of large teeth (on the maxilla and palatine) growing close to one another. Flynn et al. (2010) reported that the palatine was reversed from what is shown in figures 1 and 2, with a toothless anterior maxillary process.

Convergence with Sauropods
The elevation and reduction of the naris converges with that of sauropods and gives Azendohsaurus it’s sauropod-like look. Flynn et al. (2010) reported, “Azendohsaurus and numerous basal sauropodomorph dinosaur taxa share an array of convergently acquired features associated with herbivory, including tooth denticles, expanded tooth crowns, a downturned dentary and the articular located at the ventral margin of the mandible.”

Nesbitt et al. 2013. reported on the post-crania:
“Azendohsaurus madagaskarensis possessed an elongated neck, short tail, and stocky limbs. The manus and pes have unexpectedly short digits, terminating in large, recurved ungual phalanges. Together with the skull, knowledge of the postcranial skeleton elevates A. madagaskarensis to another highly apomorphic and bizarre Triassic archosauromorph.”

This description is both distinct and similar to Trilophosaurus.

References
Dutuit J-M 1972. Découverte d’un Dinosaure ornithischien dans le Trias supérieur de l’Atlas occidental marocain. Comptes Rendus de l’Académie des Sciences à Paris, Série D 275:2841-2844.
Flynn JJ, Nesbitt, SJ, Parrish JM, Ranivoharimanana L and Wyss AR 2010. A new species of Azendohsaurus (Diapsida: Archosauromorpha) from the Triassic Isalo Group of southwestern Madagascar: cranium and mandible”. Palaeontology 53 (3): 669–688. doi:10.1111/j.1475-4983.2010.00954.x
Gauffre, F-X 1993. The prosauropod dinosaur Azendohsaurus laaroussii from the upper Triassic of Morocco. Palaeontology 36(4):897-908. Gauffre pdf online
Nesbitt, S, Flynn J, Ranivohrimanina L, Pritchard A and Wyss A 2013. Relationships among the bizarre: the anatomy of Azendohsaurus madagaskarensis and its implications for resolving early archosauromroph phylogeny. Journal of Vertebrate Paleontology abstracts 2013.

Eichstattisaurus. Not a Gekkotan. A Snake Ancestor.

Eichstattisaurus and its sister, Ardeosaurus, were two small lizards found in Solnhofen limestones from the late Jurassic period, approximately 150 mya. Originally (Meyer 1860) and subsequently (Mateer 1982) these two were considered basal gekkotans, relatives of the living gecko, Gekko. Not much attention has been paid to either one. Both are typicall preserved complete and articulated, sometimes with some scalation and soft tissue preservation.

Eichstattisaurus and Ardeosaurus.

Figure 1. Eichstattisaurus and Ardeosaurus. Two Jurassic lizards in the lineage of snakes.

New Nesting
After entering the characters of both lizards, I was surprised to see that they nested not with Gekko, but with Adriosaurus, a hyper-elongated lizard with tiny limbs and a long neck, and Pachyrhachis, a basal snake with tiny hind limbs. This nesting, ancestral to snakes, has been largely overlooked by prior studies. I missed it too. The relationships is not obvious at first glance. I just finally got around to studying these two, fully expecting them to nest with Gekko.

Characters shared by members of this clade with Adriosaurus and Pachyrhachis include the orbit shape, the quadrate shape, supraoccipital fusion, converging temples, ectopterygoid shape, the absence of the retroarticular process, and the metatarsus configuration, among dozens of other traits that are shared with larger clades and by convergence with other reptilian clades.

The slender and elongated premaxillary ascending process was overlooked by Mateer (1982). If anyone has a palate view of either taxon, I’d like to see it.

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
Mateer NJ 1982. Osteology of the Jurassic Lizard Ardeosaurus brevipes (Meyer). Palaeontology 25(3):461-469. online pdf
Meyer H von 1860. Zur Fauna der Vorwelt. Reptilien aus dem lithographischen Schiefer des Jura in Deutschland mit Franchreich. Frankfurt-am-Main.

wiki/Ardeosaurus

What is Megachirella?

Updated November 21, 2014 with a new skull for Megachirella.

It’s a pleasure to report a proper nesting once in a while. Such is the case with Megachirella, named for its large hand. Megachirella (Fig. 1) was originally nested with Marmoretta (Fig. 2) and the large study confirms it.

Figure 1. Megachirella, a flat-headed rhynchocephalian close to Marmoretta and basal to pleurosaurs.

Figure 1. Megachirella, a flat-headed rhynchocephalian close to Marmoretta and basal to pleurosaurs.

Megachirella wachtleri (Renesto and Posenato 2003) KUH-1501, 2 cm skull length, Middle Triassic, ~240 mya, was a smallish lepidosauriform with a moderately elongated neck and a large flattened skull. The teeth were short and stout. The quadrate was highly curved and the eyes were large. The forelimbs were robust and the carpus was well-ossified. The unguals were sharp.

Taxonomic position
The authors reported, Despite being incomplete, the specimen shows enough characters to allow placement within Lepidosauriformes, close to the Middle Jurassic genus Marmoretta.” Yes, they nailed it! That was a great assessment. Distinct from Marmoretta, Megachirella had a bowed quadrate, a larger qj process on the jugal and a narrower nasal.

Behavior and Niche
The authors considered Megachirella not specialized for either arboreal or aquatic life, thus it would have been a generalized predator of insects and other invertebrates both on the ground and on branches.

Figure 2. Marmoretta, a basal rhynchocephalian in the lineage of pleurosaurs

Figure 2. Marmoretta, a basal rhynchocephalian in the lineage of pleurosaurs

Marmoretta
Marmoretta oxoniensis
 (Evans 1991) Middle/Late Jurassic, ~2.5 cm skull length, was orginally considered a a late-surviving sister of kuehneosaursdrepanosaurs  and lepidosaurs, which is true, but a little too generalized. Here (Fig. 3) Marmoretta and Megachirella were derived from a sister to Gephyrosaurus.  See the complete tree.

Megachirella and her sisters.Megachirella and her sisters.

Figure 3. Megachirella and her sisters.

Distinct from Gephyrosaurus, the skull of Marmoretta was flatter overall with a larger orbit. The parietals were longer. The naris was larger and more dorsal. The prefrontal was narrower. The lacrimal was still visible. The jugal was reduced. The postorbitals approached the parietals posterior to the postfrontals.

A flat-headed rhynchocephalian, Marmoretta and Megachirella nest near the base, prior to the fusion of teeth together and to the jaws in many derived taxa.

Late breaking news (11/21/14): These two taxa were basal to the aquatic pleurosaurs.

References
Evans SE 1991. A new lizard−like reptile (Diapsida: Lepidosauromorpha) from the Middle Jurassic of Oxfordshire. Zoological Journal of the Linnean Society 103:391-412.
Renesto S and Posenato R 2003. A new lepidosauromorph reptile from the Middle Triassic of the Dolomites (northern Italy). Rivista Italiana di Paleontologia e Stratigrafia 109(3) 463-474. online pdf

wiki/Megachirella_wachtleri 

Pterosaur and Reptile Tree Revisions

Science is a process.
As I often say, “Test. Test. And test again.” One of the best ways to test a phylogenetic analysis is to add taxa. If the tree is good (states have been accurately entered, a sufficient gamut of taxa and characters are present), the new taxa will drop into their nesting sites without shifting sister taxa and the tree retains complete resolution. My biggest beef with other, prior smaller trees is their lack of an umbrella study on which to base their taxon inclusion choices. As a result, prior trees often do not include taxa that should be included and often they include taxa that should not be included.

The Pterosaur Tree
The present pterosaur tree is distinct from all prior studies because it is much larger overall and it recovers four separate origins of the “pterodactyloid”-grade, two from separate Dorygnathus species and two more from the smaller Scaphognathus species. There were five origins if you count the darwinopterids, which only achieved that grade above the shoulders.

Recent additions of Cuspicephalus (at the base of Germanodactylus cristatus (no. 61)) and Aurorazhdarcho and Prejanopterus (at the base of Nyctosaurus + Pteranodon) created a minor loss of resolution, whch inspired a review of the characters of sisters. I found a few errors which were corrected. The resulting tree recovers relationships that more closely resemble actual evolutionary directions. Basal Pteranodon are more closely related to the Karlsruhe specimen of Germanodactylus. Wellnhofer’s (1970) number 13 is more closely related to Muzquizopteryx + Nyctosaurus. Otherwise the completely resolved tree was unchanged.

I shortened the second wing phalanx of the BMM specimen of Germanodactylus because the tree showed in autapomorphy (unique trait). All sisters had a manual 4.2/m4.3 joint at the elbow when the wing was folded. The BMM specimen had a joint slightly beyond the elbow. Another look at the specimen revealed a break in m4.2, which artificially elongated that phalanx. Once corrected the autapomorphy disappeared and the m4.2/m4.3 joint returned to match the elbow, as in sisters.

The present pterosaur tree has 174 taxa, up from about 150 when first placed online.

The Reptile Tree
In the large reptile tree the recent addition of Megachirella at the base of the Lepidosauromorpha and Eusaurosphargis within the Thalattosauria recovered a loss of resolution that inspired second looks at sister taxa. Mistakes were present and those were corrected.

Macroleter now nests as a less derived sister to Lanthanosuchus. Pointy-snouted Endennasaurus now nests closer to pointy-snouted Xinpusaurus. Otherwise the tree is unchanged and now completely resolved. The tree has 268 taxa, up from 225 when reptileevolution.com first began nearly a year ago. The tree also remains unchanged when reduced to 60 cherry-picked taxa and remains diphyletic with just a few basal reptile taxa are included.

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.

No References

The Origin of the Dicynodonts

Updated Nov. 16, 2013
Dicynodonts were herbivorous therapsids that lost most of their teeth, save the canine fangs. They originated during the Middle Permian (265 mya) and continued at least until the Late Triassic (215 mya), but a specimen from Australia may extend that to the Early Cretaceous (105 mya). Fossils are found world wide.

Anomodonts (including dicynodonts) had a distinct front-back sliding movement of the mandible that affected the development of jaw muscles and the bones that anchored them.

Traditional Dicynodont Origins
Dr. Kenneth D. Angielczyk reported online* that dicynodonts descended from Cynodonts + Therocephalians and the following non-dicynodont anomodonts: Biseridens, Anomocephalus, Venjukovioidea, Patranomodon and Galeops, in order of increasing similarity to dicynodonts. Eodicynodon is considered the most basal dicynodont.

Problem?
It seems difficult to derive anomodonts from the hypercarnivorous therocephalians. Moreover, several basal taxa were not included in the Angielczyk tree.

(*Sorry this was unavailable when I composed this earlier. I’ll keep looking for it.) There’s also the Rubidge Sidor tree here.

Figure 1. Click to enlarge. Basal therapsids in phylogenetic order as shown by their skulls.

Figure 1. Click to enlarge. Basal therapsids in phylogenetic order as shown by their skulls.

Heretical Dicynodont Origins
The large phylogenetic analysis included a larger number of basal therapsids and recovered anomodonts (including dicynodonts) nesting separate from therocephalians and biarmosuchians, at the base of the therapsida. Here (Fig. 1) the basal dicynodont, Eodicynodon, descended from sisters to , Venjukovia, Otsheria, Microurania, IVPP V18120, Stenocybus and Ophiacodon in order of increasing distance. None of these were hyper-carnivores. The non-dicynodont anomodonts, Anomocephalus, Suminia, Venjukovia [now Ulemica], Galechirus and Patranomodon, also descended from a sister to Stenocybus (Fig. 1).

The New Dicynodont Ancestors and the Reappearance of Canine Fangs
While Archaeothyris, one of the oldest synapsids yet discovered, had moderate canine fangs. Ophiacodon had relatively smaller fangs and Nikkasaurus had no trace of fangs. In Microurania (Ivakhnenko 2003) small canine fangs reappeared. Non-dicynodont anomodonts, such as Anomocephalus and Suminia had no fangs. The tusks of Tiarajudens appear to be new structures, further back from the typical canine position. Similarly, the large canine teeth of dicynodonts appear after a reduction of the canines in ancestral taxa.

References
Ivakhnenko MF 2003. Eotherapsids from the East European Placket (Late Permian). Paleontological Journal, 37, Suppl. 4: S339-S464.
Kammerer CF and Angielczyk KD 2009. A proposed higher taxonomy of anomodont therapsids. Zootaxa 2018:1–24.

What is Cuspicephalus?

Cuspicephalus scarfi (MJML K1918, Martill and Etches 2011, prepublished online) is a new “monofenestratan pterosaur from the Kimmeridge Clay Formation (Upper Jurassic, Kimmeridgian) of Dorset, England.” While noting resemblances to Germanodactylus, those were dismissed by “the presence of teeth on the distal rostrum” (but see below). They reported, “The dentition and posterior skull morphology suggest affinities with Darwinopterus, but a close relationship cannot be proved.”

Tracing and reconstruction of Cuspicephalus

Figure1. Tracing and reconstruction of Cuspicephalus according to Martill and Etches (2011). Only a bare outline was recovered despite having first-hand access to the specimen.

Cuspicephalus scarfi

Figure 1. Cuspicephalus scarfi. Click to enlarge. Originally described without the mandible. Was it overlooked? Here more details was recovered using the DGS method. I had no access to the fossil itself. This appears to be the most gracile skull and mandible of any known germanodactylid or perhaps any known pterosaur.

Here, added to the large pterosaur study, Cuspicephalus nested within the genus Germanodactylus at the base of the division between the No. 61 specimen, G. cristatus on one branch, and Elanodactylus + Prejanopterus on the other. The expanded exoccipital/squamosal “ear” is a key trait found in sisters, plus the rostral and cranial crest are common in this clade. The supposition that no teeth appear on the distal rostrum of other Germanodactylus is false. The authors also overlooked a narrow mandible present on the fossil and discovered using DGS (digital graphic segregation). Cuspicephalus has the longest antorbital fenestra and the most gracile mandible of the germanodactylids. I would expect the post-crania to be likewise gracile.

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
Martill DM and Etches S 2011. A new monofenestratan pterosaur from the Kimmeridge Clay Formation (Upper Jurassic, Kimmeridgian) of Dorset, England”. Acta Palaeontologica Polonica in press. doi:10.4202/app.2011.0071.  online pdf

Wiki/Cuspicephalus