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)

You heard it here first: no gender differences detected in pterosaur pelves

A new paper on wukongopterid crests
(Cheng et al. 2017) reports, “We also show that there is no significant variation in the anatomy of the pelvis of crested and crestless specimens. We further revisit the discussion regarding the function of cranial structures in pterosaurs and argue that they cannot be dismissed a priori as a valuable tool for species recognition.”

The subject of gender differences
in pterosaur pelves was examined here, here and here. While the subject of gender differences in pterosaur crests was examined here, here and here in previous posts going back several years (Fig. 1).

Female Pteranodon?

Figure 3. Pteranodon (left) and Nyctosaurus (right) pelves. KUVP 933 (I)  is closer to Nyctosaurus in morphology. It is not a female Pteranodon. It belongs to a big Nyctosaurus. Note the HUGE individual variation presented here among putative congeneric specimens.

Nice to see published work
rejecting the hypotheses by Bennett 1992 that linked crest size to pelvic canal size. Bennett did not realize the large opening pelvis was that of a large nyctosaurid (Fig. 1), as in all specimens of Nyctosaurus. Cheng et al. report, “there is no direct association of the skulls and pelves that could back this hypothesis (e.g., Kellner and Tomida 2000). Re-evaluation of several specimens attributed to Pteranodon has shown that in some cases there are sufficient morphological differences other than the shape and size of the cranial crest, supporting a larger taxonomic diversity within what can be called the Pteranodon-complex (Kellner 2010).” Here (Fig. 2) smaller more primitive Pteranodon specimens have smaller crests, just as smaller more primitive tapejarids do.

Figure 2. The Tanking-Davis specimen compared to other forms. Specimen w and specimen z appear to be the closest to the Tanking-David specimen. Specimen 'w' = Pteranodon sternbergi? USNM 12167 (undescribed). Specimen 'z' = Pteranodon longiceps? Dawndraco? UALVP 24238. Click to enlarge.

Figure 2. The Tanking-Davis specimen compared to other forms. Specimen w and specimen z appear to be the closest to the Tanking-David specimen. Specimen ‘w’ = Pteranodon sternbergi? USNM 12167 (undescribed). Specimen ‘z’ = Pteranodon longiceps? Dawndraco? UALVP 24238. Click to enlarge.

Then there is the Hamipterus association…

According to Cheng et al. “Hamipterus tianshanensis bears a  premaxillary crest that, in similar sized individuals, showed consistently two distinct morphotypes: one with larger and more robust crests, and the second with smaller and more delicate crests. These morphotypes were tentatively regarded as males and females, respectively (Wang et al. 2014a). This occurrence constitute, to our knowledge, the best argument favoring sexual dimorphism expressed by cranial crests.” Of course these could be different ages, alpha and beta individuals (= individual variation leading to rapid phylogenetic changes), tribes (familial clades), or male and female. Pterosaurs have been competing for mating privileges since before they had wings, in Cosesaurus, for instance.

And there is Caiuajara
where Cheng et al. report, “Caiuajara (admittedly very distantly related to the Wukongopteridae), there seems a continuum in the appearance and development of the cranial crest, present in this taxon at a very young ontogenetic stage (Manzig et al. 2014).”

Cheng et al. conclude: “the variation in shapes and sizes of cranial crests that are found in pterosaurs, associated with other morphological features, should not be understated as being a powerful tool for understanding their diversity.”

No images or reconstructions
were offered of the pelves under study (as provided in Fig. 3). Precise measurements in a series of tables were presented. No phylogenetic analysis was attempted by Cheng et al., but you can see the results of such a test here, at the large pterosaur tree where five specimens attributed to Darwinopterus and additional others attributed to other wukongopterids lump and separate without loss of resolution.

As reported earlier
I have not found two Rhamphorhynchus specimens that score the same, except for a juvenile of the largest species. That goes the same for Pterodactylus, Germanodactylus, Pteranodon (Fig. 2), Darwinopterus (Fig. 3) or any other genus represented by a large number of individual specimens. They all nest in phylogenetic order, lumped and split by a variety of traits. Note the HUGE individual variation presented here among putative congeneric specimens.

Figure 1. Click to enlarge. The five specimens of Darwinopterus to scale and in phylogenetic order preceded by six more primitive taxa. The ZMNH 8802 specimen is a female associated with an egg. The others genders shown are guesses by Lü et al. 2011a. Note the skull did not elongate, it actually shrank in the vertical dimension, probably reducing its weight. The female is crestless because it is the most primitive of the five known Darwinopterus specimens. The odds that the remaining four specimens are all males is relatively small.

Figure 3. Click to enlarge. The five specimens of Darwinopterus to scale and in phylogenetic order preceded by six more primitive taxa. The ZMNH 8802 specimen is a female associated with an egg. The others genders shown are guesses by Lü et al. 2011a. Note the skull did not elongate, it actually shrank in the vertical dimension, probably reducing its weight. The female is crestless because it is the most primitive of the five known Darwinopterus specimens. The odds that the remaining four specimens are all males is relatively small.

References
Cheng X, Jiang S-X, Wang X-L and Kellner AWA 2017. Premaxillary crest variation within the Wukongopteridae (Reptilia, Pterosauria) and comments on cranial structures in pterosaurs. Anais da Academia Brasileira de Ciencias. http://dx.doi.org/10.1590/0001-3765201720160742

Live birth in ‘Dinocephalosaurus’? Maybe. Maybe not.

Yesterday Liu et al. 2017 reported on
a pregnant Dinocephalosaurus (Figs. 1-5). This is wonderful and exciting news. However, the embryo is NOT in the process of passing through the cloaca, as we’ve seen in ichthyosaurs. The embryo is much higher in the abdomen, still in the uterus. So the headline “Live birth in an archosauromorph reptile” is… at best… premature. Live birth is still a possibility. A critical examination of the data reveals a few more major and minor problems.

Dinocephalosaurus in resting, feeding and breathing modes.

Figure 1. The holotype (not the new specimen) of Dinocephalosaurus in resting, feeding and breathing modes. In breathing mode the throat sac would capture air that would not be inhaled until the neck was horizontal at the bottom of the shallow sea. Orbits on top of the skull support this hypothesis. Image from Peters 2005. The new specimen has a longer neck, a more robust tail, and a different pedal morphology.

Unfortunately
the authors nested Dinocephalosaurus within the Archosauromorpha (Fig. 2). That is incorrect. Dinocephalosaurus nests within the new Lepidosauromorpha in the large reptile tree (LRT, 952 taxa), which minimizes the taxon exclusion problem suffered by the much smaller taxon list in the Liu et al. 2017 tree.

Figure 6. Cladogram from Liu et al. 2017 with colors added based on results from the LRT. Taxon exclusion is a major problem here.

Figure 2. Cladogram from Liu et al. 2017 with colors added based on results from the LRT. Taxon exclusion is a major problem here. Note in the Liu et al. cladogram members of the Protorosauria are divided into three clades. In sympathy, members of the Tritosauria and Protorosauria do indeed converge with one another. More taxa clears up the problem shown here of cherry-picking taxa.

Dinocephalosaurus actually nests
within the lepidosaur clade, Tritosauria, a clade that also includes Tanystropheus, pterosaurs and several other taxa (Fig. 7) that had been mistaken for protorosaur relatives in the Liu et al and other prior studies.

As a lepidosaur, 
Dinocephalosaurus would have been able to retain embryos within the mother far longer that in extant archosauromorphs. And based on the extreme thinness of pterosaur eggshells (closest known relatives with embryos, Fig. 7), those leathery eggshells only develop just prior to egg laying. So live birth is only one of a spectrum of options for Dinocephalosaurus. As in pterosaurs, the eggs could have hatched shortly after the female laid them on the shoreline.

Dinocephalosaurus. Note the very narrow cranial portion of the skull and the very wide cheeks. That, by it self, opens the orbits dorsally. Sure there's some lateral exposure, but those eyes are looking up!

Figure 3. The holotyype of Dinocephalosaurus. Although extremely similar, the new specimen is different in several ways. See below.

Liu et al. report that live birth is unknown in the Archosauromorpha.
However, in the LRT mammals and enaliosaurs (sauropterygians + ichthyosaurs) are both archosauromorphs that experience live birth. Hyphalosaurus, a choristodere archosauromorph, had extremely thin eggshells and retained developing embryos inside the mother until laying those eggs.

Figure 5. Hypothetical Tanystropheus embryo compared to Dinocephalosaurus embryo.

Figure 4. Hypothetical Tanystropheus embryo compared to part of an embryo of the new specimen attributed to Dinocephalosaurus.

More about that embryo
What little is preserved of the Dinocephalosaurus embryo (Fig. 4) is curled up in its amniotic sac, as one would expect for any reptile embryo still in utero. For comparison, note the hypothetical Tanystropheus embryo alongside it. That long neck has to go somewhere and Dinocephalosaurus provides further evidence that juvenile tritosaurs were isometric duplicates of their adult parents. That long neck did not develop with maturity. Among other tritosaurs we see juveniles similar in proportion to adults in the basal form, Huehuecuetzpalliand all pterosaur embryos.

Liu et al. further report. “Despite the complexity of this transition, viviparity has evolved at least 115 times in extant squamates (lizards and snakes), in addition to a single time in the common ancestor of therian mammals. Moreover, viviparity is a common reproductive mode in extinct aquatic reptiles including eosauropterygians, ichthyosaurs, mosasauroids, some choristoderans and likely mesosaurs.” Since mosasauroids are extinct squamates that makes at least 116 times for lepidosaurs.    Some living squamates produce eggs that hatch shortly after they are expelled, a sort of transition from oviparity to viviparity. That’s where pterosaurs fall and perhaps Dinocephalosaurus.

More cladogram issues
The Liu et al. figure 1 cladogram shows a polytomy of most reptilian clades arising during the Permian. No such polytomy appears in the LRT in which Archosauromorpha diverged from the Lepidosauromorpha tens of millions of years earlier in the Viséan (Lower Carboniferous). Liu et al. mistakenly report that trilophosaurs, rhynchosaurs and pterosaurs are archosauromorph reptiles. They are lepidosauromorph reptiles in the LRT.

Figure 1. The new Dinocephalosaurus has traits the holotype does not, like a longer neck with more vertebrae, a robust tail with deep chevrons and a distinct foot morphology with an elongate pedal digit 4.

Figure 5. The new Dinocephalosaurus has traits the holotype does not have, like a longer neck with more vertebrae, a robust tail with deep chevrons and a distinct foot morphology with a more elongate pedal digit 4. The partial embryo is in magenta at left.

The new specimen looks like a Dinocephalosaurus, but is it one?
Distinct from the holotype, the new specimen has a deep robust tail with deep chevrons (Fig. 5). They all share a common ancestor in one of the highly variable Macrocnemus specimens (Fig. 7). The toes of the new specimen are more asymmetric. The neck probably has more vertebrae (several are lost, but note the longest ones are NOT at the base of the neck in the holotype). Unfortunately little more can be said with so much of the mother lacking at present. We’ve already seen a Chinese Tanystropheus similar to, but not identical to the European Tanystropheus. We can imagine even greater variation within the available gamut of the present sparse fossil evidence.

It really is too much
to expect identical specimens to come from distinct fossil bearing strata. So variation within Dinocephalosaurus is a possibility.

Next steps
The paleo-community needs to include more specimen-based taxa in their cladograms or the Liu et al. problem (not restricted to them!) is going to continue ad infinitum. I know that’s a lot of work. But it can be done (I’ve done it!) and it needs to be done. Just start with a large gamut analysis and keep adding taxa to it. That will make the current phylogenetic problems go away.

Final note
Images of tanystropheids and dinocephalosaurs swimming horizontally through open waters (Liu et al. 2017 their figure 3) may not be an accurate portrayals of their daily lives. Other options have been published (Fig. 1) or appear online (Fig. 8). Odd-looking tetrapods often have uncommon niches and atypical behaviors.

Tanystropheus underwater among tall crinoids and small squids.

Figure 8. Tanystropheus in a vertical strike elevating the neck and raising its blood pressure in order to keep circulation around its brain and another system to keep blood from pooling in its hind limb and tail.

References
Li C, Rieppel O and LaBarbera MC 2004. A Triassic aquatic protorosaur with an extremely long neck. Science 305:1931.
Liu, J. et al. 2017. Live birth in an archosauromorph reptile. Nature Communications 8, 14445 doi: 10.1038/ncomms14445
Peters D, Demes B and Krause DW 2005. Suction feeding in Triassic Protorosaur? Science, 308: 1112-1113.

 

Odd Gerrothorax nests with Greererpeton

Figure 1. Gerrothorax, lacks a supratemporal rim and has laterally extended ribs, similar to those in Greererpeton.

Figure 1. Gerrothorax, lacks a supratemporal rim and has laterally extended ribs, similar to those in Greererpeton. There is some variation and perhaps some confusion regarding the identity of the bones between the orbits. Here an alternate is shown that is similar to Greererpeton.

Gerrothorax pulcherrimus (Nilsson 1934, Jenkins et al. 2008; Late Triassic) was and is considered a plagiosaurine temnospondyl. Here it nests with Greererpeton with which it shares a lack of a supratemporal-tabular rim, the straight lateral ribs and other traits. The ‘interfrontal’ is here identified as fused frontals. The separated ‘frontals’ are here identified as prefrontals.

Jenkins et al. showed the skull raised like a toilet seat cover during feeding, rather than opening the mandible on this flattened bottom feeder.

Figure 1. Greererpeton reduced to a blueprint of body parts. Here there may be one extra phalanx on pedal digit 5 and one missing on pedal digit 2 compared to sister taxa. So an alternate is shown with that repair. The skulls at left are juveniles.

Figure 2. Greererpeton reduced to a blueprint of body parts. Here there may be one extra phalanx on pedal digit 5 and one missing on pedal digit 2 compared to sister taxa. So an alternate is shown with that repair. The skulls at left are juveniles. Images are from the PhD thesis of Step;hen Godfrey 1986.

Greererpeton burkemorani (Romer 1969, Smithson 1982, Godfrey 1989; Early Carboniferous, 320 mya; 1.5 m in length). Godfrey thought it nested closer to Proterogyrinus than to Ichthyostega. Here Greererpeton nests as an offshoot of the temnospondyls along with Gerrothorax (Fig. 1).

The skull was flattened with orbits on top of the skull. The lacrimal does not contact the naris. The torso included some 41 presacral vertebrae. The ribs were robust and extended laterally. The pectoral girdle was robust. The limbs were small.

No complete pedes are known for Greererpeton, according to Godfrey 1989, but that may have changed since then. So I wonder if digit two had 3 phalanges, as in sister taxa, not 2. And I wonder if digit five had 3 phalanges, as in sister taxa, not 4 (Fig. 2) as illustrated in Godfrey 1989. I have not seen manus or pes data for Gerrothorax. If you have it, please send it.

Juveniles are known with larger orbits not so dorsally oriented, but otherwise similar (Fig. 2), but note the squamosal divides the postorbital and supratemporal in the adult, making one wonder if the difference is indeed ontogenetic.

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.

References
Godfrey SJ 1986. The skeletal anatomy of Greererpeton burkemorani Romer 1969, an Upper Mississippian temnospondyl amphibian. PhD thesis, McGill University, Montreal.
Godfrey SJ 1989. The postcranial skeletal anatomy of the Carboniferous tetrapod Greererpeton burkemorani Romer, 1969. Philosophical Transactions of The Royal Society B Biological Sciences 323(1213):75-133.
Jenkins FA Jr, Shubin NH, Gates SM and Warren A 2008. Gerrothorax pulcherrimus from the Upper Triassic Fleming Fjord Formation of East Greenland and a reassessment of head lifting in temnospondyl feeding. Journal of Vertebrate Paleontology. 28 (4): 935–950.
Nilsson T 1934. Vorläufige mitteilung über einen Stegocephalenfund aus dem Rhät Schonens. Geologiska Föreningens I Stockholm Förehandlingar 56:428-442.
Romer AS 1969. A temnospondylus labyrinthodont from the Lower Carboniferousw. Kirtlandia 6:1-20.
Smithson TR 1982. The cranial morphology of Greererpeton burkemorani Romer (Amphibia: Temnospondyli). Zoological Journal of the Linnean Society 76(1):29-90.

wiki/Greererpeton
wiki/Gerrothorax

Basal tetrapod cladogram: Marjanovic and Laurin 2016, PeerJ

Recently I added
several basal tetrapod taxa to the large reptile tree (LRT, now 950 taxa) in order to better understand the origin of the clade Reptilia (= Amnlota). Along the way, the software recovered some contra-traditional nestings which revived typically cordial correspondences with Drs. David Marjanovic and Jason Pardo, both of whom have studied basal tetrapods extensively. I don’t have all of the latest literature and I appreciate that these researchers open doors I may not have seen.

Less recently
Marjanovic and Laurin (2016) reexamined a earlier report on lissamphibian origins by Ruta and Coates (2007). Marjanovic and Laurin (ML) report “thousands of suboptimal scores due to typographic and similar errors and to questionable coding decisions: logically linked (redundant) characters, others with only one described state, even characters for which most taxa were scored after presumed relatives. Even continuous characters were unordered, the effects of ontogeny were not sufficiently taken into account, and data published after 2001 were mostly excluded.”

Figure 1. Click to enlarge. Wait 10 seconds for animation to begin. Basal tetrapod tree form Marjanovic and Laurin 2016.

Figure 1. Basal tetrapod tree form Marjanovic and Laurin 2016. After 10 seconds those moving lines that appear on the right will make sense when you CLICK TO ENLARGE and see how they connect taxa on competing trees.

ML document and justify all changes
to the earlier matrix, then add 48 taxa to the original 102. They report,  “From the late19th century to now, the modern amphibians have been considered temnospondyls by some (refs omitted), lepospondyls by others and polyphyletic yet others, with Salientia being nested among the temnospondyls, Gymnophionomorpha among the lepospondyls, and Caudata either in the lepospondyls (all early works) or in the temnospondyls (works published in the 21st century).”

“The present work cannot pretend to solve the question of lissamphibian origins or any other of the controversies in the phylogeny of early limbed vertebrates (of which there are many, as we will discuss). It merely tries to test, and explain within the limitations of the dataset, to what degree the trees found by RC07 still follow from their matrix – the largest published one that has been applied to those questions – after a thorough effort to improve the accuracy of the scoring and reduce character redundancy has been carried out to the best of our current knowledge. However, we think this effort forms a necessary step towards solving any of those problems. Further progress may come from larger matrices…”

“Our matrix has only 276 characters, a strong decrease from the 339 of RC07. For the most part, this is due to our mergers of redundant characters and does not entail a loss of information.”

After all that work and all those changes and additions,
ML report their repaired tree “topology is identical to Ruta and Coates 2007.”

Unfortunately that tree is vastly different
from the one recovered in the LRT, which has far fewer taxa, but an equal or greater gamut. Let’s figure out why the topologies differ and are similar. I’ll start slow with the similarities and the metaphorical ‘low-hanging fruit.’ The difficult topics we will handle later. I took the last few weeks (far too little time) to better understand basal tetrapods having zero knowledge of most taxa before starting. I have not been able to cover all the taxa employed by the ML tree.

Similarities:

  1. Both trees include fish and fish-like tetrapods at the base
  2. Both trees include microsaurs, reptiles and extant amphibians as derived taxa
  3. Both trees agree on the inclusion set for microsaurs and holospondyls
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 2. Subset of the large reptile tree focusing on basal tetrapods, updated with Gerrothorax.

Differences:

Due to taxon exclusion,
the ML tree nests several reptiles as non-reptiles. These include:

  1. Sivanerpeton – basal reptile/amniote
  2. Gephyrostegus (bohemicus) –  basal reptile/amniote
  3. Bruktererpeton – Lepidosauromorpha
  4. Solenodonsaurus (+ Chroniosaurus, Chroniosuchus) – Archosauromorpha
  5. Tseajaia – Lepidosauromorpha
  6. Limnoscelis – Lepidosauromorpha
  7. Orobates – Lepidosauromorpha
  8. Diadectes – Lepidosauromorpha
  9. Westlothiana – Archosauromorpha

Where each taxon nests in the LRT follows each dash.

Due to taxon exclusion,
the ML tree nests several taxa as ‘Sauropsida’ a clade that no longer has utility based on the new basal reptile dichotomy Archosauromorpha and Lepidosauromorpha. These include:

  1. Captorhinus – Lepidosauromorpha
  2. Paleothyris/Protorothyris – two distinct Archosauromorpha
  3. Petrolacosaurus – Archosauromorpha

Chroniosuchia
ML report, “Chroniosaurus has a fully resolved position one node more crown ward than Gephyrostegidae, Bruktererpeton or Temnospondyli and one node more rootward than Solenodonsaurus.”  This is a similar nesting to the LRT except that all listed taxa other than Temnospondyli nest within the Reptilia. ML are missing several taxa that would have changed their tree topology (see the LRT for that list).

 

Microbrachis
I caught a little heat for not using the latest drawings of Microbrachis earlier. The new tracings (Fig. 3) come from Vallin and Laurin 2004. Note the tracings of the in situ specimen (color) do precisely match the freehand reconstruction they offered. All scoring changes further cemented prior LRT relationships.

Figure 3. Microbrachis images from Vallin and Laurin 2008. Color added here.

Figure 3. Microbrachis images from Vallin and Laurin 2004. Color added here.

More later.

References
Marjanovic D and Laurin M 2016. Reevaluation of the largest published morphological data matrix for phylogenetic analysis of Paleozoic limbed vertebrates. PeerJ. Not peer-reviewed. 356 pp.
Ruta M and Coates MI 2007
. Dates, nodes and character conflict: addressing the lissamphibian origin problem. Journal of Systematic Palaeontology 5-69-122.
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

wiki/Microbrachis

 

Estimating dino/croc divergence times: Turner et al. 2017

This might have been yet another case
of scientists TRUSTING authority (= the work of others) rather than TESTING competing phylogenetic analyses. In this case, however, two of the three authors in Turner, Pritchard and Matze 2017 relied on their own flawed (= serious taxon exclusion problems) phylogenetic analyses and for good measure they threw in a third flawed (= more taxon exclusion problems) analysis (Nesbitt 2011) that we examined and reexamined in an 11-part series.

In any case, since none of the trees
in the new Turner et al. study  stand up to scrutiny (= do not agree with one another, do not produce gradual accumulations of traits in derived taxa and depend on long ghost lineaages), everything Turner et al. (2017) did afterwards has no credibility and no utility. So sadly, the entire paper is a waste of their time. Metaphorically, they built their house on sand.

On the other hand,
when you start with a study that provides a gradual accumulation of derived traits in all derived taxa, and minimizes the effect of taxon exclusion, like the large reptile tree (LRT (949 taxa) then you’ve metaphorically built your house on solid ground. And it’s much simpler to pinpoint the dino/croc divergence time because you are provided with a last common ancestor for these sister clades: Gracilisuchus (Figs. 1, 2). Crocs and dinos are sister taxa. None of the studies used by Turner et al. (Pritchard et al. 2015, Nesbit 2011, Turner 2015) recovered that tested relationship.

Figure 1. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Herrerasaurus, Tawa and Eoraptor.

Figure 1. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Herrerasaurus, Tawa and Eoraptor.

So when did dinos and crocs diverge?
Let’s look a the three most recent taxa both clades share in common in reverse chronological and phylogenetic order:

  1. Gracilisuchus = 230 mya.
  2. Turfanosuchus = 235 mya.
  3. Decuriasuchus = 240 mya.

So that narrows the divergence time pretty well…

And how did Turner et al. do?
They report,“The average ghost lineage for the group as sampled is 31 million years.” Their conclusion states no firm date or date range. Rather, their whole paper appears to be a long story on how they tested this that and the other without getting around to their headline topic. And without nailing down a last common ancestor or a croc/dino divergence time.

Figure 2. Basal crocs. Decuriasuchus and Gracilisuchus are found in both croc and dino lineages.

Figure 2. Basal crocs. Decuriasuchus and Gracilisuchus are found in both croc and dino lineages.

All the other taxa
and all the other testing performed by Turner et al. were for nought.

For more information
on any of the taxa employed by Turner et al, just look them up at ReptileEvolution.com.

References
Nesbitt SJ 2011. The early evolution of archosaurs: relationships and the origin of major clades. Bulletin of the American Museum of Natural History;352:1–292.
Pritchard AC, Turner AH, Nesbitt SJ, Irmis RB and Smith ND 2015. Late Triassic tanystropheids (Reptilia, Archosauromorpha) from Northern New Mexico (Petrified Forest Member, Chinle Formation) and the biogeography, functional morphology, and evolution of Tanystropheidae. Journal of Vertebrate Paleontology. ;e911186.
Turner AH 2015. A Review of Shamosuchus and Paralligator (Crocodyliformes, Neosuchia) from the Cretaceous of Asia. PLoS ONE. 2015;10(2):e0118116. doi: 10.1371/journal.pone.0118116. pmid:25714338
Turner AH, Pritchard AC and Matzke NJ 2017. Empirical and Bayesian approaches to fossil-only divergence times: A study across three reptile clades. PLoS ONE 12(2): e0169885. doi:10.1371/journal.pone.0169885

 

Introducing the Paratetrapoda with a new reconstruction of Pholidogaster

Updated June 17, 2021
with more taxa and scoring changes. Click here to see the update.

With questions arising
about the phylogenetic nesting of the fish-like paratetrapod Colosteus with Osteolepistoday several putative members of the Colosteidae were added to the large reptile tree (LRT, subset Fig. 1). According to Wikipedia, clade members should include Colosteus, Deltaherpeton, Greererpeton and Pholidogaster.

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.

As you can see
(Fig. 1) only one putative member of the Colosteida. Pholidogaster nests with Colosteus. Deltaherpeton nests with Eryops the temnospondyl. Greererpeton nests between temnospondyls and the Neotetrapoda with Ichthyostega at its base.

A new clade
The Paratetrapoda is here defined as Colosteus, Osteolepis, their last common ancestor and all of their descendants. Derived taxa developed tetrapod-like limbs by convergence. The Neotetrapoda is here defined as Ichthyostega, Homo, their last common ancestor and all their descendants. This is the clade that leads to all other tetrapods.

Figure 1. Greererpeton reduced to a blueprint of body parts. Here there may be one extra phalanx on pedal digit 5 and one missing on pedal digit 2 compared to sister taxa. So an alternate is shown with that repair. The skulls at left are juveniles.

Figure 2. Greererpeton reduced to a blueprint of body parts. Here there may be one extra phalanx on pedal digit 5 and one missing on pedal digit 2 compared to sister taxa. So an alternate is shown with that repair. The skulls at left are juveniles.

Greererpeton burkemorani 
(Romer 1969, Smithson 1982, Godfrey 1989; Early Carboniferous, 320 mya; 1.5 m in length). Godfrey thought it nested closer to Proterogyrinus than to Ichthyostega. Here Greererpeton nests between temnospondyls, like Sclerocephalus and Ichthyostega. The skull was flattened with orbits on top of the skull. The lacrimal contacted the naris. The torso included some 41 presacral vertebrae. The pectoral girdle was robust. The limbs were small. The powerful tail was the chief organ of locomotion.

Figure 3. Deltaherpeton skull with colors added.

Figure 3. Deltaherpeton skull with colors added.

Deltaherpeton hiemstrae 
(Bolt JR and Lombard RE 2010; Viséan, Early Carboniferous; Fig. 3) nests with Eryops among the temnospondyls and appears to have a fused nasal/frontal.

Figure 2. Colosteus holotype drawing of the fossil in situ from Hook 1983 compared to the closely related Osteolepis.

Figure 4. Colosteus holotype drawing of the fossil in situ from Hook 1983 compared to the closely related Osteolepis.

Colosteus scutellatus 
(Newberry 1856, Hook 1983; Westphalian, Late Carboniferous, 305 mya; 1m in length; AMNH 6916; Fig. 4) was originally considered a fish (Pygopterus) and renamed by Cope 1869. Here Colosteus nests with Osteolepis and Pholidogaster (Figs. 5, 6) as a paratetrapod convergent with traditional tetrapods. The skull was ovate, the vomers and dentaries had fangs, the fins had transformed to tiny four-fingered limbs. The lacrimal did not reach the external naris. The scales remained large and rhomboid-shaped. Pectoral girdle had not yet evolved an external scapula and coracoid.

Figure 1. Pholidogaster skulls compared to Colosteus and Osteolepis. Panchen reconstruction on left includes a premaxilla that is too wide. At right revised width to fit premaxilla tracing, pectoral girdle and in situ lacrimal and cheek bones.

Figure 5. Pholidogaster skulls compared to Colosteus and Osteolepis. Panchen reconstruction on left includes a premaxilla that is too wide. At right revised width to fit premaxilla tracing, pectoral girdle and in situ lacrimal and cheek bones.

Pholidogaster pisciformis
(Huxley 1862, Panchen 1975; Visean, Early Carboniferous, 340 mya; Figs. 5, 6) was originally considered a labyrindont and an anthracosaur, but here nests with Osteolepis and Colosteus (Fig. 5) among the Paratetrapoda, a clade that developed limbs independent of the Tetrapoda.

The new skull reconstruction (Fig. 5) is narrower than in Panchen 1975 to match the premaxilla and pectoral girdle. The premaxilla carried a lateral fang and the dentary had a corresponding slot for it.

Figure 5. Pholidogaster in situ and with post crania reconstructed based on the Osteolepis bauplan.

Figure 5. Pholidogaster in situ and with post crania reconstructed based on the Osteolepis bauplan. The long straight ribs are actually neural spines that are elevated here. Small bones, like those found in Osteolepis and Eusthenopteron are retained at the bases of unpreserved dorsal and anal fins. The interclavile extends below the jaw. It appears unlikely that this taxon had a neck.

The vertebral column included small bones that were basal to both dorsal fins and anal fin. The long straight unpaired bones once thought to be ribs are here identified as tall slender neural spines. The tail was little different from that found in Osteolepis, including the slight upturn, like a shark’s tail.

The interclavicle and clavicles extended beneath the mandibles. No scapula or coracoid was visible. Those were tiny elements medial to the coracoid and cleithrum. The fingers did not ossify. The pelvis is well ossified with an acetabulum dorsal to the pubis. The hind limb includes metatarsals and a few digits.

The ossified scales that covered the body in Osteolepis and Colosteus are not present here.

Pholdogaster has been known for over 150 years
and if it had only been reconstructed with the present precision I think its fish-like affinities would have been discovered earlier. It’s 150-year-old specific name ‘pisciformis’ points obviously to its fish-like affinities, which were recognized then, but have received less attention in recent studies. It appears unlikely that any paratetrapod had a movable neck.

Remember
we have tetrapods crawling on shore and leaving footprints in the Middle Devonian, millions of years before Acanthostega and Ichthyostega in the latest Devonian. These famous taxa now appear to be conservative relicts retaining fish-like traits, rather than liberal land pioneers inventing tetrapod-like traits.

References
Agassiz L 1843. Recherches Sur Les Poissons Fossiles. Tome I (livr. 18). Imprimerie de Petitpierre, Neuchatel xxxii-188.
Bolt JR and Lombard RE 2010.
 Deltaherpeton hiemstrae, a New Colosteid Tetrapod from the Mississippian of Iowa. Journal of Paleontology. 84 (6): 1135–1151.
Godfrey SJ 1989. The postcranial skeletal anatomy of the Carboniferous tetrapod Greererpeton burkemorani Romer, 1969. Philosophical Transactions of The Royal Society B Biological Sciences 323(1213):75-133.
Hook RW 1983. Colosteus scutellatus (Newberry), a primtiive temnospondyl amphibian from the Middle Pennsylvanian of Linton, Ohio. American Museum Novitates 2770; 1-41.
Huxley TH 1862. On new labyrinthodonts from the Edinburgh Coal-field. Quarterly Journal of the Geological Society London18:291-296.
Panchen AL 1975. A New Genus and Species of Anthracosaur Amphibian from the Lower Carboniferous of Scotland and the Status of Pholidogaster pisciformis Huxley. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 269(900):581-637.
Romer AS 1969. A temnospondylus labyrinthodont from the Lower Carboniferousw. Kirtlandia 6:1-20.
Smithson TR 1982. The cranial morphology of Greererpeton burkemorani Romer (Amphibia: Temnospondyli). Zoological Journal of the Linnean Society 76(1):29-90.

wiki/Greererpeton
wiki/Osteolepis
wiki/Colosteus
wiki/Pholidogaster

Did Acanthostega lose an intertemporal?

Or was it overlooked?
(See Fig. 1, blinks organge/green above the orbit.)

Figure 1. Acanthostega skull from Porro et al. 2015 showing lack and presence of the intertemporal.

Figure 1. Acanthostega skull from Porro et al. 2015 showing lack and presence of the intertemporal above the postorbital and between the postfrontal and supratemporal — or else it is fused to the parietal.

Ancestral osteolepiformes
like Osteolepis have an intertemporal. So do many (but not all) basal tetrapods. Porro et al 2015 did not indicate one (Fig. 1), but I have added a green one where I think one would be, dorsal to the postorbitals and lateral to the parietals. It blinks on an off in that animation. It might have been overlooked because the whole skull roof has shifted forward. Typically the intertemporal is located somewhat behind the orbit (Fig. 2), where the supratemporal is in figure 1.

Ventastega, a closely related taxon,
(Fig. 2, green added) indicates the presence of an intertemporal. Earlier an intertemporal was located in Ichthyostega where one was overlooked before.

Figure 2. Ventastega from Ahlberg et al. 2008, showing their interpretation of an intertemporal (green).

Figure 2. Ventastega from Ahlberg et al. 2008, showing their interpretation of an intertemporal (green) above a missing postorbital.

Side note
Most Acanthostega relatives do not have such an elevated mandible tip. This hook-jaw morphology is similar to the spawning phase of the male sockeye salmon, which does not have such a hooked jaw in its ocean phase.

References
Ahlberg PE, Clack JA, Luksevics E, Bom H and Zupins I 2008. Ventastega curonica and the origin of tetrapod morphology. Nature 453: 1199-1204.
Clack JA 2006. The emergence of early tetrapods. Palaeogeography Palaeoclimatology Palaeoecology. 232: 167–189.
Clack JA 2009. The fin to limb transition: new data, interpretations, and hypotheses from paleontology and developmental biology. Annual Review of Earth and Planetary Sciences. 37: 163–179.
Coates MI 2014. The Devonian tetrapod Acanthostega gunnari Jarvik: Postcranial anatomy, basal tetrapod interrelationships and patterns of skeletal evolution. Earth and Environmental Science Transactions of the Royal Society of Edinburgh.
Coates MI and Clack JA 1990. Polydactly in the earliest known tetrapod limbs. Nature 347: 66-69.
Jarvik E 1952. On the fish-like tail in the ichtyhyostegid stegocephalians. Meddelelser om Grønland 114: 1–90.
Porro LB, Rayfield EJ and Clack JA 2015. Descriptive Anatomy and Three-Dimensional Reconstruction of the Skull of the Early Tetrapod Acanthostega gunnari Jarvik, 1952. PLoS ONE 10(3): e0118882. doi:10.1371/journal.pone.0118882

wiki/Acanthostega

Orbit size does not always equal eyeball size

Revised May 14, 2019
with new bone identifications in Andrias (Fig. 1).

Earlier we looked at the two-part orbit of Baphetes and Megalocephalus. I put forth a ‘shifting eyeball’ hypothesis, but I don’t buy into it, just to set things straight. I think the eyeball was in the dorsoposterior, more rounded portion. As we saw even earlier, basal tetrapods were evolving rostral loss of bone. So that sort of thing happened then.

Today we’ll talk about
an extreme case of tiny eyeball and enormous orbit.

Andrias davidianus (Blanchard 1871; 1.8m in length; extant) is a sister to Rana, the bullfrog and derived from a sister to Gerobatrachus. The jugal is absent. The orbit is much larger than the eyeball.

Figure 1. Revised skull of Andrias japonicas, the giant Chinese salamander. This was informed by recent studies of the mudpuppy, Necturus.

Figure 1. Revised skull of Andrias japonicas, the giant Chinese salamander. This was informed by recent studies of the mudpuppy, Necturus.

Images of the living
Andrias can be found here. You’ll be lucky if you do see the eyeball. It is very tiny. I probably overemphasized the size of the eyeball in figure 1.

References
Blanchard É 1871. Note sur une nouvelle Salamandre gigantesque (Sieboldia Davidiana Blanch.) de la Chine occidentale. Comptes Rendus Hebdomadaires des Séances de l’Académie des Sciences. Paris 73: 79.

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