Ozarcus enters the LRT as a basal stem bony fish (and a human ancestor)

Following the advent of transverse toothless jaws
in Silurian Loganiella and its extant sisters, Rhincodon (the whale shark) and Manta, the Large Reptile Tree (subset Fig. 1) splits taxa with newly acquired anteroposteriorly deeper jaws + marginal teeth in two during the first great dichotomy. At this point the LRT splits elasmobranchii (sharks + ratfish in blue Fig. 1) from stem bony fish like Ozarcus (Figs. 2, 3).

In phase two,
The clade of stem bony fish (that had no bone) quickly and ultimately evolved into genuine bony fish like Amia (the bowfin), at the top of the orange column (Fig. 1) and Trachinocephalus (the lizardfish), at the top of the yellow cladogram (Fig. 1).

Members of this clade and those that directly precede it
are step-wise ancestors to tetrapods, mammals and humans.

Figure x. Updated subset of the LRT, focusing on basal vertebrates = fish.

Figure 1. Updated subset of the LRT, focusing on basal vertebrates = fish.

The basalmost stem bony fish in the LRT
is now Ozarcus here (Figs. 2, 3) shown for the first time with bones colored with tetrapod homologs for scoring.  It had large eyes, a deep jawline and the tiniest marginal teeth. Such teeth were a new invention and this is how they started, not much bigger than dermal denticles. It was so close to sharks, it was originally described as “a Palaeozoic shark with osteichthyan-like branchial arches.”

With its giant eyes and short rostrum
Ozarcus also looked like a spiny shark (clade: Acanthodii), but Ozarcus nests in a different node (Fig. 1) and shows how jaws developed from anterior gill arches. Despite the Early Carboniferous appearance of Ozarcus in the fossil record, the genesis of this taxon goes back to the mid-Silurian based on phylogenetic bracketing.

Figure x. Skull of Ozarcus colored using DGS methods and tetrapod homologs. Note the tiny teeth inside the large tooth basin. The narrowness of the skull is partly due to crushing.

Figure 2. Skull of Ozarcus colored using DGS methods and tetrapod homologs. Note the tiny teeth inside the large tooth basin. The narrowness of the skull is partly due to crushing.

Ozarcus mapesae (Pradel et al. 2019; Early Carboniferous, 325 mya; AMNH FF20544) nests with Falcatus in the LRT, between Loganiella and Doliodus. The authors considered the palatoquadrate (pq) a single bone (Fig. 3) rather than the jugal, pterygoid, ectopterygoid, quadrate and lacrimal shown here (Fig. 2). The intertemporal anchors the hyomandibular here (eh) as in other vertebrates. The teeth are extremely tiny, much smaller than each tooth basin in the maxilla. The premaxilla is a tiny area between the ventrally opening incurrent nares. A ghosted prefrontal is shown framing the excurrent naris. The seemingly crushed narrowness of the skull was likely broader in life, especially around the gill basket.

FIgure 1. Ozarcus from Pradel et al. 2019 animated to show the mandible/gill elements opening and closing.

Figure 3.  Ozarcus from Pradel et al. 2019 animated to show the mandible/gill elements opening and closing.

Sister taxa, like Falcatus
(Fig. 4; another Early Carboniferous late survivor of an earlier Silurian radiation), helps us imagine what the post-crania of Ozarcus might look like. Falcatus also had a soft rostrum made of nasal bone precursors.

Figure 3. Falcatus skull. This taxon is close to Polyodon in the LRT.

Figure 4. Falcatus skull. This taxon is close to Polyodon in the LRT.

Lacking such a rostrum is Doliodus
(Fig. 5)  from the Early Devonian. Rather than a tall narrow skull, as in Ozarcus, Doliodus had a wider skull with odd, two-pronged teeth. Such teeth represent an early experiment as toothed jaws were a new thing.

A basal elasmobranch still living with us today,
Chimaera, also has a tall narrow skull, like that of Ozarcus. Chimaera gives us a  model for restoring what the post-crania of Ozarcus might have looked like.

Figure 1. Doliodus skull and pectoral region with lateral reconstruction at right. Note the narrow pectoral region relative to the wide spread occiput. Apparently this fish had a narrower body than head.

Figure 5. Doliodus skull and pectoral region with lateral reconstruction at right. Note the narrow pectoral region relative to the wide spread occiput. Apparently this fish had a narrower body than head.

Taxa in the LRT
document a gradual accumulation of derived traits. This is well illustrated with these related taxa, all of which look like one another, more so than any other included taxon. The tree topology has settled down now. New taxa drop in without upsetting the nesting of taxa already in the tree.


References
Pradel A, Maisey JG, Tafforeau P, Mapes RH and Mallant J 2014. A Palaeozoic shark with osteichthyan-like branchial arches. Nature 13185. doi:10.1038/nature13195e

wiki/Ozarcus

Goodbye Batoidea, another traditional clade invalidated by the LRT

According to Wikipedia,
“Batoideais a superorder of cartilaginous fishes commonly known as rays. They and their close relatives, the sharks, comprise the subclass Elasmobranchii. Rays are the largest group of cartilaginous fishes, with well over 600 species in 26 families. Rays are distinguished by their flattened bodies, enlarged pectoral fins that are fused to the head, and gill slits that are placed on their ventral surfaces.”

Figure 1. Spotted eagle ray skull shows the anterior portions of the pectoral fins jointed medially to create a digging snout.

Figure 1. Spotted eagle ray skull shows the anterior portions of the pectoral fins conjoined  medially to create a digging snout.

Aeobatus narinari (Figs. 1–3 originally Raja narinari Euphrasén 1790; 5m in length, 3m wingspan) is the extant spotted eagle ray and the subject of today’s post.

The distinctive flat muscular snout
is created by the anterior processes of the pectoral fins conjoining anteriorly, as in other stingrays that also have detachable venom spines at the base of their tail.

Figure 2. Subset of the LRT focusing on basal vertebrates. Purple taxa are traditional rays, here shown to be convergent in their morphology.

Figure 2. Subset of the LRT focusing on basal vertebrates. Purple taxa are traditional rays, here shown to be convergent in their morphology.

Traditionally
Aeobatus was considered a ray that should have nested with the guitarfish, Rhinobatos and even closer to Manta, the manta ray. Everyone considered that clade, Batoidea, monophyletic prior to today’s post.

When you expand your taxon list, as in the large reptile tree (LRT, 1586 taxa; Fig. 2), Aeobatus nests with Squatina, the angel shark, not with Manta or Rhinobatos. That means the three tested rays are convergent.

So say goodbye
to the Myliobatiformes. Say goodbye to the Rajiformes. And say goodbye to the Batoidea. These clades are not monophyletic in the LRT, but evolved a ray-like appearance by convergence. This hypothesis of interrelationships was apparently overlooked by prior workers. Please let me know if otherwise and I will promote that citation. Meanwhile, following the scientific method, independent testing using a similar taxon list should take place to confirm or refute this hypothesis.

While free swimming (rather than bottom dwelling)
and capable of leaping clear of the water, the spotted eagle ray feeds on shelled invertebrates hiding beneath sea sands. Distinct from Squatina, the marginal jaws of Aetobatus are nearly toothless. The vomer and a medial plate between the dentaries include a series of flat plates acting as crushing palatal teeth distinct from other tested rays.

Figure 2. The spotted eagle ray, Aetobatus in vivo.

Figure 3. The spotted eagle ray, Aetobatus in vivo.

Compare Aetobatus to its LRT sister,
Squatina oculata
 (Bonaparte 1840; Figs. 4, 5), the extant smooth back angelshark. In this  basal fish some of the gill bones are transformed to jaws with teeth, as in typical sharks. In general morphology Squatina is little changed from the Early Silurian jawless thelodonts that preceded it.

Figure 5. Squatina skull. Note the gill bars framing the mouth. These are modified in Aetobatus into a digging snout.

Figure 4. Squatina skull. Note the gill bars framing the mouth. These are modified in Aetobatus into a digging snout.

Distinct from rays,
the gill slits appear anterior to the expanded anterior processes of the pectoral fins in Squatina (Fig. 6), demonstrating how the gill slits shift ventrally in rays. These same anterior processes form the rostrum in Aetobatus (Fig. 1).

Figure 6. Squatina in vivo, lateral view. The large pectoral and pelvic fins give Squatina a broad, ray-like appearance in dorsal view.

Figure 5. Squatina in vivo, lateral view. The large pectoral and pelvic fins give Squatina a broad, ray-like appearance in dorsal view.

I’m only guessing,
but based on the present results, long-nosed stingless skates are going to nest with Rhinobatos, the guitarfish. Stingray, including cow nose rays, will nest with Aetobatus. And Manta will continue to nest alone among rays, as no other is a plankton feeder with an anterior gaping mouth without teeth. It’s closest relative is Rhincodon, the whale shark, the most primitive gnathostome (vertebrate with jaws) in the LRT.

FIgure 7. Squatina in ventral view showing the anterior processes of the pectoral fin that develop into a rostrum in Aetobatus and shift the gill slits ventrally.

Figure 6. Squatina in ventral view showing the anterior processes of the pectoral fin that develop into a rostrum in Aetobatus and shift the gill slits ventrally.

We’ve seen convergence before
in pterodactyloid-grade pterosaurs, turtles, whales, and dozens of other taxa. Convergence can produce false positive results if you omit key taxa. So far the LRT has been able to sort it all out by including overlooked taxa and avoiding genomic data.

When I started
ReptileEvolution.com eight years ago, I thought many of these issues were resolved long ago. While discoveries like this keep me digging for more, academic workers should have resolved these issues decades ago. Traditions persist for a reason.


References
Euphrasén BA 1790. Raja (Narinari). Kongl. Vetenskaps Academiens Nya Handlingar, 11:217-219.

wiki/Spotted_eagle_ray

Cyrilavis colburnorum: another barbet, not a stem parrot

While researching fossil parrots,
in preparation for tomorrow’s post on a giant parrot, I found a paper by Ksepka, Clarke and Grande 2011 describing a Green River “stem parrot.” Cyrilavis colburnorum (early Eocene, Figs. 1–3), turns out to be a barbet, very similar to the extant Psilopogon (Fig. 4) and the coeval Septencoracias, all more closely related to toucans and hornbills, than to parrots (Fig. 5), as we learned here. Like the two tested barbets, the posterior maxilla extends lateral to and below the jawline and terminates without narrowing to a point or suturing to other bones. It just hangs out there (Fig. 4). And that’s just the first of many traits (I don’t want to pull a Larry Martin here, especially since he found the generic type).

FIgure 1. Skeleton of Cyrilavis in situ. This is not a parrot, but a barbet from the Green River formation.

FIgure 1. Skeleton of Cyrilavis in situ. This is not a parrot, but a barbet from the Green River formation.

Originally the skull was crudely traced
with an outline that failed to identify several bones and misidentified others (Fig. 2). Here (Fig. 2) the bones are colored for identification and reconstruction using DGS.

The Ksepka team also failed to include
barbets in their phylogenetic analysis, only parrots and the outgroups passeriformes, falconidae, and mouse birds in order of increasing distance. They assumed their inclusion set incorrectly. So, once again, taxon exclusion messed up their results. It doesn’t matter if you view the subjects first hand or not, if you don’t include their closest sister taxa.

Figure 1. The so-called Green River parrot, Cyrilavis-colburnorum, is actually a barbet, closer to hornbills and toucans.

Figure 1. The so-called Green River parrot, Cyrilavis-colburnorum, is actually a barbet, closer to hornbills and toucans. The lacrimal here appears to be pterygoid+palatine for the top bone and a pterygoid + a triangular bone below the jaw. The actual lacrimal is inside the orbit.  DGS tracing tells us more than the original crude tracing and permits the reconstruction without free handing any bones.

Type specimen: FMNH PA 754, a skeleton (Figs. 1, 2). Referred specimen: (FMNH PA 722, a complete skull and cervicals (Fig. 3).

Figure 3. The referred skull of Cyrilavis, Here it appears that the frontals have collapsed and the lacrimal has popped out of the orbit.

Figure 3. The referred skull of Cyrilavis, Here it appears that the frontals have collapsed and the lacrimal has popped out of the orbit.

 

I have not tested
the type specimen for the genus, Cyrilavis olsoni (Feduccia and Martin 1976), but the mandible in ventral view is short, straight and sharply tipped, unlike that of parrots, but similar to barbets.

Figure 2. Skull of the extant barbet, Psilopogon. Note the posteriorly drooping maxilla and compare it to Septencoracias in figure 1.

Figure 4. Skull of the extant barbet, Psilopogon. Note the posteriorly drooping maxilla and compare it to Septencoracias in figure 1.

And lest we forget,
like parrots, barbets likewise have a zygodactyl (pedal digit 4 oriented posteriorly) pes (Fig. 5).

FIgure 5. Psilopogon, is a living barbet from SE Asia.

FIgure 5. Psilopogon, is a living barbet from SE Asia. Note the zygodactyl pes, convergent with parrots.

The authors discuss the clade, Halcyornithidae,
a clade within Pan-Psittaiformes. The authors report, “All character states potentially supporting halcyornithid monophyly are reconstructed as ambiguous synapomorphies due to the unresolved polytomy containing the five sampled taxa.” 

It would probably be interesting
to reconstruct and test other members of the Halcyornithidae to see if they also nest elsewhere in the LRT. We’ll save that for later.

Figure 4. Subset of the LRT focusing on birds sized by color.

Figure 5. Subset of the LRT focusing on birds sized by color. Parrots, like Ara, are not related to barbets, like Psilopogon.

 

References
Feduccia A and Martin LD 1976. The Eocene zygodactyl birds of North America (Aves: Piciformes). Smithsonian Contributions to Paleontology, 27:101–110.
Ksepka DK, Clarke JA, and Grande L 2011. Stem parrots (Aves, Halcyornithidae) from the Green River Formation and a combined phylogeny of Pan-Psittaciformes. Journal of Paleontology 85:835-854

 

New insights from the Early Cretaceous bird Changzuiornis

Figure1. Changzuiornis in situ, isolated from matrix, and repositioned to an invivo pose.

Figure1. Changzuiornis in situ, isolated from matrix, and repositioned to an invivo pose, each 5 seconds.

About a year and a half ago,
Huang et al. 2016 brought us a complete and articulated skeleton of a new ornithurine bird, Changzuiornis ahgmi (Fig. 1), from the Early Cretaceous very close to Yanornis. The rostrum is more elongate with a large naris and tiny teeth (Fig. 2).

Please note
the better detail DGS brings to understanding where the bones are in this crushed fossil. The original line drawing (Fig. 2 below) leaves almost everything up to the imagination.

Figure 2. Changzuiornis skull in situ showing what you can do with DGS vs. traditional tracing from the original paper.

Figure 2. Changzuiornis skull in situ showing what you can do with DGS vs. traditional tracing from the original paper.

The maxilla clearly makes up most of the rostrum
in Changzuiornis. And this came as a surprise to Huang et al., who report this is “a characteristic not present in the avian crown clade in which most of the rostrum and nearly the entire facial margin is made up by premaxilla.” (Fig. 3)

Figure 3. From Huang et al. showing in red the extent of the maxilla in their interpretations. This is not long enough according to present interpretations.

Figure 3. From Huang et al. showing in red the extent of the maxilla in their interpretations. This is not long enough according to present interpretations.

It’s actually much worse than they think.
Their interpretation (Fig. 3) of the avian crown clade rostrum is too short, at least for tested taxa like Changzuiornis and Yanornis. Huang et al. do not extend the anterior maxilla far enough anteriorly, ignoring the portion where it overlaps and laminates to the lateral premaxilla (Fig. 2). For comparison, here’s a new interpretation of Struthio, the ostrich with a larger maxilla (Fig. 4) similarly laminated to the lateral premaxilla.

If I’m wrong
I’ll gladly go through a spanking machine (a silly kid’s party game).

If that’s not enough, check out
Yanornis, Cariama, Phoenicopterus, Sagittarius, Llallawavis, Falco and Tyto for a similar anteriorly extended maxillae. All are now repaired from my earlier mistakes as I wrongly followed traditional interpretations.

Figure 3. Struthio skull with a long maxilla.

Figure 3. Struthio skull with a long maxilla.

Otherwise
Changzuiornis is a close sister to Yanornis, with a longer rostrum and some other minor differences apparently a wee bit closer to Gansus, Ichthyornis and Hesperornis. For instance, pedal digits 3 and 4 are similar in length.

Speaking of Hesperornis
It’s difficult to find photographic data on the the rostrum of Hesperornis and Parahesperornis. I failed to do so because authors from Marsh to Gingreich to Martin instead provided line drawings (Fig. 4), which purported to show a tiny maxilla beneath a naris with a premaxilla forming at least half of the ventral margin of the naris. Unfortunately, no sister taxa have such a morphology. Martin 1984 let loose a clue that Parahesperornis had an anteriorly extended maxilla with that line extending anterior to the naris. I provide that option here (Fig. 4 in green) and wish for actual fossil images to work on.

Figure 4. Parahesperornis and Hesperornis skulls with a small traditional maxilla and the a new large one as interpreted here.

Figure 4. Parahesperornis and Hesperornis skulls with a small traditional maxilla and the a new large one as interpreted here.

Ichthyornis and Gansus can’t help us.
Their skulls are too poorly known.

References
Huang J, Wang X, Hu Y-C, Liu J, Peteya JA and Clarke JA 2016. A new ornithurine from the Early Cretaceous of China sheds light on the evolution of early ecological and cranial diversity in birds. PeerJ.com
Martin L 1984. A new Hesperornithid and the relationships of the Mesozoic birds. Transactions of the Kansas Academy of Science 87:141-150.

 

wiki/Parahesperornis

Vesperopterylus (aka: Versperopterylus, Lü et al. 2017) did not have a reversed first toe

And this specimen PROVES again
that anurognathids DID NOT have giant eyeballs in the anterior skull.

Figure 1. Vesperopterylus in situ. There is nothing distinct about pedal digit 1.

Figure 1. Vesperopterylus in situ. There is nothing distinct about pedal digit 1.

Lü et al. 2017 bring us a new little wide-skull anurognathid
Vesperopterylus lamadongensis (Lü et al. 2017) is a complete skeleton of a wide-skull anurognathid. It was considered the first pterosaur with a reversed first toe based on the fact that in digit 1 the palmar surface of the ungual is oriented lateral while digis 2–4 the palmar surfaces of the unguals are medial. That is based on the slight transverse curve of the metatarsus (Peters 2000) and the crushing which always lays unguals on their side. In life the palmar surfaces were all ventral and digit 1 radiated anteriorly along with the others.

Figure 2. Vesperopterylus reconstructed using original drawings which were originally traced from the photo. Manual digit 4.4 is buried beneath other bones and reemerges to give its length. Pedal digit 1 turns laterally due to metacarpal arcing and taphonomic crushing. There is nothing reversed about it. 

Figure 2. Vesperopterylus reconstructed using original drawings which were originally traced from the photo. Manual digit 4.4 is buried beneath other bones and reemerges to give its length. Pedal digit 1 turns laterally due to metacarpal arcing and taphonomic crushing. There is nothing reversed about it.

Lü et al were unable to segregate the skull bones.
Those are segregated by color here using DGS (Digital Graphic Segregation). See below. Some soft tissue is preserved on the wing. Note: I did not see the fossil first hand, yet I was able to discern the skull bones that evidently baffled those who had this specimen under a binocular microscope. Perhaps they were looking for the giant sclerotic rings in the anterior skull that are not present. Little ones, yes. Big ones, no.

Figure 1. Vesperopterylus skull with bones identified by DGS (digital graphic segregation). Lü et al. were not able to discern these bones and so left the area blank in their tracing. Note the complete lack of a giant eyeball in the front of the skull. Radius and ulna were removed for clarity and to show a complete lack of giant eyeballs (sclerotic rings) in the anterior skull. 

Figure 1. Vesperopterylus skull with bones identified by DGS (digital graphic segregation). Lü et al. were not able to discern these bones and so left the area blank in their tracing. Note the complete lack of a giant eyeball in the front of the skull. Radius and ulna were removed for clarity and to show a complete lack of giant eyeballs (sclerotic rings) in the anterior skull.

This skull reconstruction
(Fig. 4) is typical of every other anurognathid, because guesswork has been minimized here. After doing this several times with other anurognathids, I knew what to look for and found it. No giant sclerotic rings were seen in this specimen.

Figure 4. Vesperopterylus skull reconstructed from color data traced in figure 3.

Figure 4. Vesperopterylus skull reconstructed from color data traced in figure 3. Due to the angled sides of the skull some foreshortening was employed  to match those angles. Original sizes are also shown.

With regard to perching
all basal pterosaurs could perch on branches of a wide variety of diameters by flexing digit 1–4 while extending digit 5, acting like a universal wrench (Peters 2000, FIg. 5). This ability has been overlooked by other workers for the last two decades,

Figure 1. The pterosaur Dorygnathus perching on a branch. Above the pes of Dorygnathus demonstrating the use of pedal digit 5 as a universal wrench (left), extending while the other four toes flexed around a branch of any diameter and (right) flexing with the other four toes. As in birds, perching requires bipedal balancing because the medially directed fingers have nothing to grasp.

Figure 1. The pterosaur Dorygnathus perching on a branch. Above the pes of Dorygnathus demonstrating the use of pedal digit 5 as a universal wrench (left), extending while the other four toes flexed around a branch of any diameter and (right) flexing with the other four toes. As in birds, perching requires bipedal balancing because the medially directed fingers have nothing to grasp.

I have not yet added Vesperopterylus
with the holotype of Anurognathus in the large pterosaur tree.

References
Lü J-C et al. 2017. Short note on a new anurognathid pterosaur with evidence of perching behaviour from Jianchang of Liaoning Province, China. From: Hone, D. W. E., Witton MP and Martill DM(eds) New Perspectives on Pterosaur Palaeobiology.
Geological Society, London, Special Publications, 455, https://doi.org/10.1144/SP455.16
Peters D 2000. Description and Interpretation of Interphalangeal Lines in Tetrapods. 
Ichnos, 7: 11-41

 

Little red flags for a Saharastega reconstruction

Updated April 17, 2017 with a removal of the nonexistent dorsal tusk holes in Nigerpeton. Thanks DM!

Saharastega moradiensis (Sidor et al., 2005; Late Permian; Fig. 1) is a large, flat-headed, temnospondyl basal tetrapod. According to the original reconstruction (Fig. 1) it is the only temnospondyl in the large reptile tree (LRT, now 962 taxa) in which the jugal has no posterior process and the quadratojugal contacts the postorbital. Those autapomorphies raised red flags that started the present investigation.

Figure 1. Saharastega fossil skull, tracing of fossil skull, freehand reconstruction, all by Sidor et al., followed by color tracing that finds nares at the dorsal rostrum, concave dorsal rostrum and posterior jugal separating the quadratojugal from the postorbital overlooked by Sidor et al.

Figure 1. Saharastega fossil skull, tracing of fossil skull, freehand reconstruction, all by Sidor et al., followed by color tracing that finds nares at the concave dorsal rostrum and posterior jugal separating the quadratojugal from the postorbital

Taking the Saharastega freehand reconstruction at face value
Saharastega was scored and it nested with the coeval Nigerpeton (Fig. 2) which has dorsal nares and anterior fang holes along with a concave rostral profile. These are traits not shared by Saharastega according to the freehand reconstruction (Fig. 1).

Going back to the fossil
and colorizing the bones of Saharastega reveals a skull more like that of Nigerpeton than the freehand reconstruction indicates. Fang holes are not presesent, according to those who have seen the fossil (see below), so they are removed here. Both share dorsal nares and a concave rostral profile, together with a jugal that separates the quadratojugal from the postorbital. Note the placement of the internal nares relative to the external nares in Nigerpeton (Fig. 2). That pattern is more or less shared by Saharastega (Fig. 1).

Figure 2. Nigerpeton nests with its contemporary, Saharastega (figure 1) and has dorsal nares and a concave rostrum.

Figure 2. Nigerpeton nests with its contemporary, Saharastega (figure 1) and has dorsal nares and a concave rostrum.

The two taxa, Nigerpeton and Saharastega,
are not congeneric, but they do appear to share more traits than the authors originally indicated. The crack across the rostrum in Saharastega somewhat obliterated the nares. Otherwise they would have not been overlooked.

References
Sidor CA, O’Keefe FR, Damiani R, Steyer JS, Smith RMH, Larsson HCE, Sereno PC, Ide O and Maga A 2005. Permian tetrapods from the Sahara show climate-controlled endemism in Pangaea. Nature. 434 (7035): 886–889. doi:10.1038/nature03393. PMID 15829962.
Damiani R, Sidor CA, Steyer JS. Smith RMH, Larsson HCE, Maga A and Ide O 2006. The vertebrate fauna of the Upper Permian of Niger. V. The primitive temnospondyl Saharastega moradiensis. Journal of Vertebrate Paleontology. 26 (3): 559–572. doi:
wiki/Saharastega

Douzhanopterus: Not the pterosaur they think it is + overlooked wing membranes.

A new paper by Wang et al. 2017
describes a ‘transitional’ pterosaur (Figs. 1,4) that was purported to link long-tail basal pterosaurs to short-tail derived pterosaurs (Fig. 2).

Unforunately this pterosaur does not do that.
No one single pterosaur can do that (see below, Fig. 3). But the new pterosaur is a new genus with a set of unique traits that nests at the base of the Pterodactylus clade, the Pterodactylidae, not the base of the so-called ‘Pterodactyloidea.’

Figure 1. Douzhanopterus at top in situ compared to scale with related pterosaurs, including Jianchangopterus, Ningchengopterus and the Painten pterosaur, all at the base of the Pterodactylidae.

Figure 1. Douzhanopterus (Wang et al. 2017) at top in situ compared to scale with related pterosaurs, including Jianchangopterus, Ningchengopterus and the Painten pterosaur, all nesting at the base of the Pterodactylidae.

Douzhanopterus zhengi (Wang et al. 2017; STM 19–35A & B; Late Jurassic, Fig. 1) originally nested (Fig. 2) between the Wukongopterids (Wukongopterus, Darwinopterus, Kunpengopterus.) and the Painten pterosaur (Fig. 1) and the rest of the purported clade Pterodactyloidea, beginning with Pterodactylus antiquus. Unfortunately, this is an antiquated matrix based on Wang et al. 2009 modified from Andres et al. 2014 with additional taxa. Unfortunately it includes far too few additional taxa and it produces an illogical cladogram in which clade members recovered by the large pterosaur tree (LPT) become separated from one another.

Figure 2. Basal portion of a cladogram provided by Liu et al. but colorized here to show the division of clades recovered in the LPT.

Figure 2. Basal portion of a cladogram provided by Wang et al. but colorized here to show the division of clades recovered in the LPT. Note that dorygnathids are basal to all derived cyan taxa and Scaphognathids are basal to all derived amber taxa.

As readers of this blogpost know
there was not one origin to the ‘Pterodactyloidea” clade, there were four origins to the pterodactyloid grade: two out of two Dorygnathus specimens and two out of small Scaphognathus descendants (subset of the LPT, Fig. 3). Once again, taxon exclusion is the problem in Wang et al. 2017. Too few taxa were included and many key taxa were ignored.

Should we get excited about the length of the tail
or the retention of an elongate pedal digit 5? No. These are common traits widely known in sister taxa and too often overlooked by pterosaur workers.

I understand the difficulties here.
Wang et al. saw no skull (but see below!) and the rest of the small skeleton is rather plesiomorphic, except for those long shins (tibiae). Even so, plugging in traits to the LPT reveals that Douzhanopterus is indeed a unique genus.

Figure 3. Subset of the LPT focusing on Pterodactylus with Douzhanopterus at its base.

Figure 3. Subset of the LPT focusing on Pterodactylus with Douzhanopterus at its base. Many of these taxa were not included in the Wang et al. 2017 study, but not the proximity of the Painten pterosaur, similar to the Wang et al study.

Here Douzhanopterus nests
in the LPT as a larger sister to Jianchangopterus (Lü and Bo 2011; Middle Jurassic; Fig. 1) at the base of the Pterodactylidae. These are just those few taxa closest to the holotype Pterodactylus and includes the Painten pterosaur, as in the Wang et al. study. Here that pterosaur was likewise demoted from the base of the Pterodactyloidea to the base of the Pterodactylidae.

Figure 4. Douzhanopterus in situ, original drawing and color tracing showing the overlooked soft tissue membranes and skull. Click to enlarge.

Figure 4. Douzhanopterus in situ, original drawing and color tracing showing the overlooked soft tissue membranes and skull. Click to enlarge.

Wang et al. overlooked
the skull and soft tissue membranes (Fig. 4) that are readily seen in the published in situ photo image. Click here to enlarge the image. These shapes confirm earlier findings (Peters 2002) in which the wing membranes had a narrow chord + fuselage fillet and were stretched between the elbow and wingtip, not the knee or ankle and wingtip. The uropatagia were also had narrow chords and were separated from one another, not connected to the tail or to each other, contra traditional interpretations.

DGS
This is what Digital Graphic Segregation is good for. I have not seen the specimen firsthand yet I have been able to recover subtle data overlooked by firsthand observation. The headline for this specimen should have been about the wing membranes, not the erroneous phylogenetic placement.

References:
Andres B, Clark J and Xu X 2014. The earliest pterodactyloid and the origin of the group. Curr. Biol. 24, 1011–1016.
Lü J and Bo X 2011. A New Rhamphorhynchid Pterosaur (Pterosauria) from the Middle Jurassic Tiaojishan Formation of Western Liaoning, China. Acta Geologica Sinica 85(5): 977–983.
Peters D 2002.  A New Model for the Evolution of the Pterosaur Wing – with a twist.  Historical Biology 15: 277–301.
Wang X.Kellner AWA, Jiang S and  Meng X 2009. An unusual long-tailed pterosaur with elongated neck from western Liaoning of China. An. Acad. Bras. Cienc. 81, 793–812.
Wang et al. 2017. New evidence from China for the nature of the pterosaur evolutionary transition. Nature Scientific Reports 7, 42763; doi: 10.1038/srep42763

wiki/Jianchangopterus
wiki/Ningchengopterus
wiki/Douzhanopterus (not yet posted)

Eocaecilia and Brachydectes: old mistakes and new insights

Updated February 9, 13 and 17, 2017 with more taxa added to the LRT and revisions to the skull bone identification.

Further updated March 18, 2017 with new skull bone identities for Brachydectes

Earlier we looked at the long-bodied
basal tetrapod sisters, Eocaecilia (Fig. 1) and Brachydectes (Fig 2). Adding new closely related taxa, like Adelogyrinus (Fig. 3) to the large reptile tree (LRT, 945 taxa, Fig. 5) illuminates several prior mistakes in bone identification and moves the long-bodied Microbrachis (Fig. 4) to the base of the extant caecilian clade. Here are the corrected images.

Figure 1. Eocaecilia skull with original and new bone identifications based on comparisons to sister taxa listed here. Like Brachydectes, the jaw joint has moved forward, beneath the jugal now fused to the quadratojugal creating a long retroarticular process, otherwise rare in amphibians. Also rare is the fusion of the squamosal with the postorbital.

Figure 1. Eocaecilia skull with original and new bone identifications based on comparisons to sister taxa listed here. Like Brachydectes, the jaw joint has moved forward, beneath the jugal now fused to the quadratojugal creating a long retroarticular process, otherwise rare in amphibians. Also rare is the fusion of the squamosal with the postorbital.

Eocaecilia micropodia
(Jenkins and Walsh 1993; Early Jurassic ~190 mya, ~8 cm in length) was derived from a sister to Adelospondylus and phylogenetically preceded modern caecilians. Originally the supratemporal was tentatively labeled a tabular and the postorbital was originally labeled a squamosal. The lacrimal and maxilla are coosified as are the ectopterygoid and palatine. The squamosal and quadratojugal are absent.

Unlike Eocaecilia,
extant caecilians do not have limbs. The tail is short or absent. The eyes are reduced and the skin has annular rings. More skull bones fuse together. A pair of tentacles between the eye and nostril appear to be used for chemical sensations (smelling). Some caecilians grow to 1.5 m in length.

Figure 2. The skull of Brachydectes revised. Like Eocaecilia, the squamosal and quadratojugal are missing.

Figure 2. The skull of Brachydectes revised. Like Eocaecilia, the squamosal and quadratojugal are missing.

Brachydectes newberryi
(Wellstead 1991; Latest Carboniferous) Similar in body length to EocaeceliaBrachydectes (Carboniferous, 43 cm long) was a lysorophian amphibian with a very small skull and vestigial limbs. The skull has a large orbit. Like its current sister, Eocaecilia (Fig. 1), Brachydectes lacked a squamosall and quadratojugal. The mandible was shorter than the skull. Brachydectes had up to 99 presacral vertebrae. Earlier I made the mistake of thinking this was a burrowing animal with tiny eyes close to the lacrimal. As in unrelated baphetids, the orbit is much larger in Brachydectes than the eyeball, even when the eyeball is enlarged as shown above.

Figure 3. Adelogyrinus skull. This less derived taxa provides clues to the identification of the bones in the skulls of Eocaecili and Brachydectes.

Figure 3. Adelogyrinus skull. This less derived taxa provides clues to the identification of the bones in the skulls of Eocaecili and Brachydectes.

Adelogyrinus simorhynchus
(Watson 1929; Viséan, Early Carboniferous, 340 mya) had a shorter, fish-like snout and longer cranium. Note the loss of the otic notch and the posterior displacement of the tiny postorbital.

Dolichopareias disjectus 
(Watson 1929; 1889, 101, 17 Royal Scottish Museum) helps one understand the fusion patterns in Adelospondylus and Adelogyrinus (Fig. 3).

Figure 4. Microbrachis slightly revised with a new indented supratemporal here rotated to the lateral side of the skull above the squamosal and quadratojugal. Otherwise this image is from Carroll, who did not indent the supratemporal.

Figure 4. Microbrachis slightly revised with a new indented supratemporal here rotated to the lateral side of the skull above the squamosal and quadratojugal. Otherwise this image is from Carroll, who did not indent the supratemporal.

Figure 5. Microbrachis skull in several views. Note the freehand reconstruction offered by Vallin and Laurin 2008 (ghosted beneath) does not match the shapes traced from the in situ drawing also presented by them. This is the source of the supratemporal indent in figure 4.

Figure 5. Microbrachis skull in several views. Note the freehand reconstruction offered by Vallin and Laurin 2008 (ghosted beneath) does not match the shapes traced from the in situ drawing also presented by them. This is the source of the supratemporal indent in figure 4.

Microbrachis
(Fritsch 1875) Middle Pennsylvanian, Late Carboniferous ~300 mya, ~15 cm in length, is THE holotype microsaur, which makes all of its descendants microsaurs. So extant caecilians are microsaurs, another clade that is no longer extinct.

Figure 6. Subset of the large reptile tree focusing on basal tetrapods, updated with Gerrothorax.Figure 6. Subset of the large reptile tree focusing on basal tetrapods, updated with Gerrothorax.

Figure 6. Subset of the large reptile tree focusing on basal tetrapods, updated with Gerrothorax.

Thank you for your patience
to those awaiting replies to their comments. It took awhile to clean up this portion of the LRT with reference to better data and new sisters. I should be able to attend to those comments shortly.

References
Brough MC and Brough J 1967. Studies on early tetrapods. II.  Microbrachis, the type microsaur. Philosophical Transactions of the Royal Society of London 252B:107-165.
Carroll RL 1967. An Adelogyrinid Lepospondyl Amphibian from the Upper Carboniferous: Canadian Journal of Zoology 45(1):1-16.
Carroll RL and Gaskill P 1978. The order Microsauria. American Philosophical Society, Philadelphia, 211 pp.
Fritsch A 1875. Fauna der Gaskohle des Pilsener und Rakonitzer Beckens. Sitzungsberichte der königliche böhmischen Gesellschaft der Wissenschaften in Prag. Jahrgang 70–79.
Jenkins FA and Walsh M 1993. An Early Jurassic caecilian with limbs. Nature 365: 246–250.
Jenkins FA, Walsh DM and Carroll RL 2007. Anatomy of Eocaecilia micropodia, a limbed caecilian of the Early Jurassic. Bulletin of the Museum of Comparative Zoology 158(6): 285-366.
Vallin G and Laurin M 2004. Cranial morphology and affinities of Microbrachis, and a reappraisal of the phylogeny and lifestyle of the first amphibians. Journal of Vertebrate Paleontology: Vol. 24 (1): 56-72 online pdf
Watson DMS 1929. The Carboniferous Amphibia of Scotland. Palaeontologia Hungarica 1:223-252
Wellstead C F 1991
. Taxonomic revision of the Lysorophia, Permo-Carboniferous lepospondyl amphibians. Bulletin of the American Museum of Natural History 209: 1–90.

wiki/Adelospondylus
wiki/Adelogyrinus
wiki/Dolichopareias
wiki/Eocaecilia
wiki/Brachydectes
wiki/Microbrachis

Pederpes gets the DGS treatment

Updated March 15, 2017 with higher resolution data. 

The first known basal tetrapod with a five-toed pes is
Pederpes finneyae (Clack 2002; Tournasian, early Carboniferous, 348mya; 1m in est. length) and it is known from a fairly complete articulated skeleton. In an attempt to reconstruct the skull I have colored elements (Fig. 1) and moved those tracings to a reconstruction in which some of the broken loose pieces have been replaced to their in vivo positions.

The lacrimal, maxilla and jugal
have broken parts that fit together like puzzle pieces. I did not realize the premaxilla was rotated, along with the lower jaw tip, such that in appeared in more dorsal view.

Figure 2. Pederpes skull elements returned to their in vivo positions. Skull roof is shown rotated to the picture plane, but in life would have been flat and seen edge-on. This is a revised reconstruction based on higher resolution data.

Figure 1. Pederpes skull elements returned to their in vivo positions. Skull roof is shown rotated to the picture plane, but in life would have been flat and seen edge-on. This is a revised reconstruction based on higher resolution data.

In the large reptile tree
Pederpes now nests with Whatcheeria.

References
Clack JA 2002. An early tetrapod from ‘Romer’s Gap’. Nature. 418 (6893): 72–76.

Dendrerpeton gets the DGS treatment

Figure 1. GIF movie of Dendrepeton fossil in situ showing original interpretation with intertemporal and contact of the prefrontal and postfrontal. Below: DGS tracing and new interpretation without the intertemporal and prefrontal/postfrontal contact.

Figure 1. GIF movie of Dendrepeton fossil in situ showing original interpretation with intertemporal and contact of the prefrontal and postfrontal. Below: DGS tracing and new interpretation without the intertemporal and prefrontal/postfrontal contact. Fossil images from Holmes et al. 1998.

Dendrerpeton acadianum (Owen 1853; Holmes, Carroll and Reisz 1998; Bashkirian, Carboniferous ~318 mya; ~10 cm in length; YPM VP 005895, BMNH R4158, RM 2.1121) was derived from a sister to Amphibamus and phylogenetically preceded Acheloma and Cacops in the large reptile tree (LRT).

Schoch and Miller 2014 considered this specimen conspecific with Dendrysekos helogenes (Steen 1934).

Figure 2. Dendrerpeton without raised orbits from Holmes et al. 1998.

Figure 2. Dendrerpeton without raised orbits from Holmes et al. 1998. These authors had firsthand access to the specimen, yet missed several details revealed by second hand access to published photos.

Overall larger than Amphibamus, 
the skull of Dendrerpeton was narrower, the rostrum longer, the nares more widely separated. The skull bones were highly sculptured.

Distinct from earlier interpretations
by Holmes, et al. 1998 (Figs. 1,2), the orbit of Dendrerpeton was raised above the skull roof, the prefrontal did not contact the postfrontal, the palatine was exposed laterally and the intertemporal was not present. These authors had firsthand access to the specimen, yet missed several details revealed by second hand access to published photos. DGS reveals where the puzzle pieces are simply by coloring them to segregate them, and trying the puzzle pieces until they fit.

At present these traits
nest Dendrerpeton close to Tersomius (Fig. 3) within the Lepospondyli.

Figure 3. Tersomius texensis, an amphibamid lepospondyl close to Dendrerpeton.

Figure 3. Tersomius texensis, an amphibamid lepospondyl close to Dendrerpeton. DGS colors have been applied over several bones.

References
Case EC 1910. New or little known reptiles and amphibians from thePermian (?) of Texas. Bulletin of the American Museum of Natural History 28, 163–181.
Holmes RB, Carroll RL and Reisz RR 1998. The first articulated skeleton of Dendrerpeton acadianum (Temnospondyli, Dendrerpetontidae) from the lower Pennsylvanian locality of Joggins, Nova Scotia, and a review of its relationships. Journal of Vertebrate Paleontology 18:64-79.
Maddin H, Fröbisch NB, Evans DC and Milner AR 2013. Reappraisal of the Early Permian amphibamid Tersomius texensis and some referred material. Comptes Rendus Palevol 12:447-461.
Moodie RL 1916. Journal of The coal measures Amphibia of North America. Carnegie Institution of Washington #238. 222 pp.
Owen R 1853. Notes on the above-described fossil remains. Quarterly Journal of the Geological Society of London 9:66-67
Schoch RR and Milner AR 2014. Temnospondyli I. Part 3A2 of Sues H-D, ed. Handbook of 6468 Paleoherpetology. Munich: Dr. Friedrich Pfeil.
Steen MC 1934. The amphibian fauna from the South Joggins, Nova Scotia. Proceedings of the Zoological Society of London 1934:465-504.
Wyman J 1857. On a batrachian reptile from the coal formation. Proceedings of the American Association for the Advancement of Science, 10th Meeting, 172-173.

wiki/Dendrerpeton
wiki/Tersomius