Cacops: Temnospondyl or Lepospondyl?

In order to understand
the interrelationships of reptiles, one needs to known where to begin and what came before the beginning. Earlier the large reptile tree (LRT) recovered the Viséan Silvanerpeton and the Late Carboniferous Gephyrostegus bohemicus at the base of the Amniota (= Reptilia) with origins in the early Viséan or earlier (340+mya).

Reptiles were derived from the clade Seymouriamorpha, 
close to Utegenia, which also nests at the base of the Lepospondyli, + Seymouria + Kotlassia. These, in turn, were derived from the reptilomorphs, Proterogyrinus and Eoherpeton.

Reptilomorphs, in turn, were derived from Temnospondyls,
at present, Eryops (unfortunately too few taxa to be more specific at present), and temnospondyls, in turn, were derived from basal tetrapods, like Pederpes.

Figure 1. Cacops and its sisters.

Figure 1. Cacops and its sisters in the LRT.

A recent objection
by Dr. David Marjanovic suggested that the basal tetrapod, Cacops, was not a lepospondyl, but actually a temnospondyl.

Figure 1. Sclerocephalus in situ and reconstructed. This taxon nests with Eryops among the temnospondyls.

Figure 1. Sclerocephalus in situ and reconstructed. To no surprise, this taxon nests with Eryops among the temnospondyls. Note the expanded ribs.

That’s worth checking out.
So I added taxa: Sclerocephalus and Broiliellus (Fig. 2). The former nested with Eryops as a temnospondyl. The latter nested with Cacops and the lepospondyls. The new taxa did not change the topology. So… either the present topology is correct, or I’ll need some taxon suggestions to make the shift happen.

Figure 1. Broiliellus skull. This taxon nests with Cacops among the lepospondyls, derived from a sister to the Seymouriamorph, Utegenia.

Figure 1. Broiliellus skull. This taxon nests with Cacops among the lepospondyls, derived from a sister to the Seymouriamorph, Utegenia. Note the ‘new’ bone between the lacrimal and jugal. That’s a surface appearance of the palatine!

 

The large reptile tree tells us
that reptiles and lepospondyls are all seymouriamorphs with Utegenia at the last base of the lepospondyls, but known only form late-surviving taxa at present. Lepospondyls continue to include Cacops and Broiliellus, along with extant amphibians and microsaurs, which mimic basal reptiles. Most of these taxa should be found someday in Romer’s Gap prior to the Viséan in the earliest Carboniferous or late Devonian.

Seymouriamorpha
Wikipedia reports, “[Seymouriamorpha] have long been considered reptiliomorphs, and most paleontologists may still accept this point of view, but some analyses suggest that seymouriamorphs are stem-tetrapods (not more closely related to Amniota than to Lissamphibia) aquatic larvae bearing external gills and grooves from the lateral line system have been found, making them unquestionably amphibians. The adults were terrestrial.

The LRT finds
seymouriamorphs basal to reptiles + lepospondyls. The latter includes lissamphibians (all extant amphibians , their last common ancestor and all of its descendants) and several other clades, including Microsauria, Nectridea, and several very elongate taxa.

Dissorophididae
Wikipedia reports, “It has been suggested that the Dissorophidae may be close to the ancestry of modern amphibians (Lissamphibia), as it is closely related to another family called Amphibamidae that is often considered ancestral to this group, although it could also be on the tetrapod stem. The large reptile tree also recovers this relationship. Cacops and Broiliellus are both considered dissorophids.

References
Lewis GE and Vaughn PP 1965. Early Permian vertebrates from the Cutler Formation of the Placerville area, Colorado, with a section on Footprints from the Cutler Formation by Donald Baird: U.S. Geol. Survey Prof. Paper 503-C, p. 1-50.
Moodie RL 1909. A contribution to a monograph of the extinct Amphibia of North America. New forms from the Carboniferous. Journal of Geology 17:38–82.
Reisz RR, Schoch RR and Anderson JS 2009. The armoured dissorophid Cacops from the Early Permian of Oklahoma and the exploitation of the terrestrial realm by amphibians. Naturwissenschaften (2009) 96:789–796. DOI 10.1007/s00114-009-0533-x
Williston SW 1910. Cacops, Desmospondylus: new genera of Permian vertebrates. Bull. Geol. Soc. Amer. XXI 249-284, pls. vi-xvii.
Williston SW 1911. Broiliellus, a new genus of amphibians from the Permian of Texas. The Journal of Geology 22(1):49-56.

wiki/Cacops
wiki/Platyhystrix
www/Broiliellus
wiki/Dissorophidae

Temnospondyl fingers: 1-4? or 2-5?

If you’re going to have a good understanding
of reptile origins, you’re going to need a good topology of pre-reptiles (aka basal tetrapods). So today, tomorrow and the next day, we’ll cover temnospondyls and how they relate to their sisters and to reptiles.

According to Wikipedia
Temnospondyls have been known since the early 19th century, and were initially thought to be reptiles. They were described at various times as batrachiansstegocephalians, and labyrinthodonts, although these names are now rarely used. Animals now grouped in Temnospondyli were spread out among several amphibian groups until the early 20th century, when they were found to belong to a distinct taxon based on the structure of their vertebrae. Experts disagree over whether temnospondyls were ancestral to modern amphibians (frogssalamanders, and caecilians), or whether the whole group died out without leaving any descendants.” The large reptile tree (LRT) indicates that temnospondyls are now extinct and not related to lepospondyls (extant amphibians and their kin).

Figure 1. Manus of Sclerocephalus, a well-preserved temnospondyl with four fingers, here labeled 1-4 (traditional) and 2-5 (heretical). The carpus is not as fully ossified as in Eryops, figure 2.

Figure 1.Manus of Sclerocephalus, a well-preserved temnospondyl with four fingers, here labeled 1-4 (traditional) and 2-5 (heretical). The carpus is not as fully ossified as in Eryops, figure 2.

Pertinent to todays discussion
Wikipedia also reports, “most temnospondyls have small limbs with four toes on each front foot and five on each hind foot.” So, the question is: which finger (not toe) is missing from the temnospondyl manus? Traditionally temnospondyl fingers have been labeled 1-4, perhaps based on the hypothesis that the medial digit has two phalanges, as in pentadactyl taxa. That would mean digits 2 and 3 lose one phalanx and digit 4 loses two phalanges — IF you’re starting with a complete pentadactyl limb — but you’re not.

Figure 2. The manus of the temnnospondyl Eryops compared to those of the polydactyl, Acanthostega and the pentadactyl reptilomorphs, Seymouria and Proterogyrinus. Homologous digits and carpal element are colored the same. In Eryops the pollex or digit 1 is absent, leaving only a small bump on Centrale 1. Note distal carpal 3 is smaller than 2 and 4 in Eryops and Seymouria.  Digit 4 is the longest in Acanthostega and temnospondyls. On Eryops I have left the original finger identifications in Roman numerals.

Figure 2. The manus of the temnnospondyl Eryops compared to those of the polydactyl, Acanthostega and the pentadactyl reptilomorphs, Seymouria and Proterogyrinus. Homologous digits and carpal element are colored the same. In Eryops the pollex or digit 1 is absent, leaving only a small bump on Centrale 1. Note distal carpal 3 is smaller than 2 and 4 in Eryops and Seymouria. Digit 4 is the longest in Acanthostega and temnospondyls. On Eryops I have left the original finger identifications in Roman numerals.

After comparing sister taxa
(and they are few at present) the digits have been relabeled here: 2-5. That means digit 1 is absent in temnospondyls. Thus, digits 2-5 lose one or two phalanges.

In the old days
paleontologists added a hallux to museum mounts and illustrations of Eryops (Fig. 3). So they were thinking the same thing with regard to digit numbers. The correct identification of the fingers is key to scoring these traits correctly in phylogenetic analyses that involve temnospondyls.

Figure 3. Old illustration of Eryops with five fingers. Hallux (in yellow) should not be there.

Figure 3. Old illustration of Eryops with five fingers. Hallux (in yellow) should not be there. See figure 2.

 

References
wiki/Temnospondyli

Necrolestes: 125 year-old assessment beats recent analysis.

As usual
I had second hand (academic papers and figures) rather than firsthand access to the specimens. It doesn’t matter how good your players are if you don’t show up on the right field at the proper hour. Here you’ll see, once again, how excluding the actual sister to an enigma taxon is the major problem, solvable by second-hand phylogenetic analysis in a large gamut study, the large reptile tree (LRT) that minimizes the problem of taxon exclusion.

Figure 1. Necrolestes skull. Note the scale bar problems. DGS colors the bones here.

Figure 1. Necrolestes skull. Note the scale bar problems. DGS colors the bones here. The lacrimal and infraorbital are enlarged here, providing a large opening for large facial nerves. Note the larger lower incisors as compared to the drawing above.

Necrolestes patagonensis  (Ameghino 1891; early Miocene, 16mya; Fig. 1; YPM PU 15065, 15384, and 15699) has been argued about for over a hundred years. Originally (Ameghino 1891) it was described as the only known extinct placental “insectivore” from South America and allied to Chrysochloris (Fig. 2), the extant golden mole.

Well done Ameghino!

Unfortunately, as time went on…
Saban 1954 considered Necrolestes a palaeanodont (Ernanodon was previously considered one). Patterson 1958 considered it a borhyaenoid metatherian. Asher et al. 2007 looked at several candidates and could not make a firm conclusion. Ladevèze et al. 2008 supported metatherian affinities. Goin et al. 2008 also could not be specific with regard to a closest known sister taxon.

The latest paper on the subject
Rougier et al. 2012 reported, “earlier studies leaned toward placental affinities and more recent ones endorsed either therian or specifically metatherian relationships.” Ultimately they nested Necrolestes with Cronopio (Fig. 4) which they considered a non-therian mammal. That is correct. They considered an earlier Van Valen 1988 statement  inspired, “…the enigmatic Miocene genus Necrolestes, usually thought to be a marsupial, is [conceivably] a late surviving Gondwantherian pantothere.” That is incorrect.

Figure 2. Chrysochloris skull lateral view. Note the many similarities to Necrolestes, including a ventral naris, expanded bulla, and similar shapes for the other bones.

Figure 2. Chrysochloris skull lateral view. Note the many similarities to Necrolestes, including a ventral naris, dorsally expanded bulla, and similar shapes for the other bones. Note the orbit is very tiny in this burrowing taxon. I don’t see an infraorbital foramen. here, distinct from Necrolestes.

Asher et al. 2007 report,
“Characters that support [Necrolestes] status as a therian mammal include a coiled cochlear housing of the inner ear. Necrolestes shows similarities to eutherian mammals, such as small incisive foramina and possibly three molars. Consistent with its status as a metatherian is the presence of five upper incisors, transverse canal foramina, and a broad proximal fibula. However, we cannot confirm other characters claimed by previous researchers as evidence for affinity with marsupial or nonplacental mammals, such as the presence of an inflected mandibular angle and epipubic bones.”

Asher et al. report,
“The external digital flexor in Chrysochloris ossifies along nearly the entire forearm, from the humeral medial epicondyle to the carpus. Necrolestes shows a similarly elongate element stretching proximally from the carpus.”

Asher et al. report,
“The idea that [Necrolestes] is related to golden moles was favored in the first two publications describing its anatomy (Ameghino, 1891; Scott, 1905). We do not believe Patterson’s contention that the status of Necrolestes as a marsupial is ‘‘virtually assured’’. We admit that the list of possible taxonomic affiliations for this animal still remains long.”

Figure 1. The Golden Mole (Chrysocloris asiaticus) nests with the tree shrew and elephant shrew in the large reptile tree, not the common mole. Image copyright Digimorph.org and used with permission.

Figure 3. The Golden Mole (Chrysochloris asiaticus) nests with the tree shrew and elephant shrew in the large reptile tree, not the common mole. Image copyright Digimorph.org and used with permission.

 

 

The large reptile tree
(920 taxa) tested Necrolestes against a wide gamut of mammal candidates and nested it securely with the golden mole, Chrysochloris. To shift Necrolestes next to Cronopio adds 22 steps.

Distinct from sister taxa
Necrolestes had five upper incisors and four lowers. That is closer to the primitive numbers for mammals and two more than in Chrysochloris. The molars are also primitive in having fewer cusps, but that also happens in whales and armadillos… and golden moles… with their simplified zalambdodont teeth… so let’s focus on other traits. Dental traits are plastic and can lead analysis astray.

Rougier et al. report,
“the first upper and lower premolars are double rooted and the following five molariform elements are single rooted, a condition shared only with the recently described meridiolestidan mammal Cronopio.” Convergent dental traits might be leading these workers so far afield the neglected to add Chrysochloris to their analysis, which seems odd and dangerous based on the long list of shared traits and overall similarity, not by convergence.

Figure 4. Cronopio nests between Juramaia and Didelphis + Ukhaatherium in the LRT. Rogier et al. nest this taxon with Necrolestes, contra the LRT. This taxon has an anterior naris, not a ventral one.

Figure 4. Cronopio nests between Juramaia and Didelphis + Ukhaatherium in the LRT. Rogier et al. nest this taxon with Necrolestes, contra the LRT. This taxon has an anterior naris, not a ventral one.

Rougier et al. gave us straw dogs
when they compared the basicrania of several sister candidates, but NOT that of Chrysochloris, to that of Necrolestes. Here I add a basicranium Rougier et al. chose to not show. Chrysochloris more closely matches the morphology of Necrolestes than any of the other three candidates. I don’t see Chrysochloris listed in the Supplemental Information for Rougier et al. which appears to test non-placental mammals only. So this is what I mean by another case of taxon exclusion. Ameghino (1891) got it right originally. Rougier Wible, Beck and Apesteguía 2012, for some reason, dropped the ball.

Figure 3. Necrolestes basicrania compared to three candidates by Rougier 2012. Here I add the basicranium for Chrysochloris for comparison and it's a better match.

Figure 3. Necrolestes basicrania compared to three candidates by Rougier 2012. Here I add the basicranium for Chrysochloris for comparison and it’s a better match. The blue element is the posterior mandible, which is not shown on the Rougier et al. drawings. Not how the lower (posterior) element curls over the basicranial element in only two candidates here. This is a placental trait. The LRT uses no petrosal traits, but image speaks for itself. Excluding the actual sister taxon was done for reasons unknown in this flawed study.

 

Deleting Chrysochloris from the LRT
nests Necrolestes with the remaining basal Glires, but resolution is lost. Not sure why, but Necrolestes has a history (see above) of being a confusing taxon when not nested with Chrysochloris.

Deleting all placentals from the LRT,
except Necrolestes, nests it between Didelphis and Asioryctes a node apart from Cronopio. So taxon exclusion doesn’t recover what Rougier et al. recovered.

Now that we have golden moles in Africa and South America
this is evidence that golden moles first appeared before those continents split apart 118 to 115 mya, long before the end of the Cretaceous. Video link here. Naish reports, “Golden moles and tenrecs appear to be close relatives, forming a clade usually termed Afrosoricida Stanhope et al., 1998 (though this is essentially synonymous with Tenrecoidea McDowell, 1958, see Asher (2001)“. That relationship is not supported by the LRT. Golden moles probably first appeared in the Early Jurassic, given that other Glires, multituberculates, split from rodents about the same time and are found as early as Middle Jurassic strata.

Rougier et al. tested earlier studies and found them flawed
Similarly, I tested Rougier et al. and found it flawed. Perhaps someday someone will likewise test this test and present additional insight into this former enigma taxon.

References
Ameghino F 1891. Nuevos restos de mamíferos fósiles descubiertos por Carlos Ameghino en el Eoceno inferior de la Patagonia austral. Especies nuevas, adiciones y correciones [New remains of fossil mammals discovered by Carlos Ameghino in the lower Eocene of southern Patagonia. New species, additions and corrections]. Rev Arg Hist Nat 1:289–328. Spanish.
Asher RJ, Horovitz I, Martin T and Sanchez-Villagra MR 2007. Neither a Rodent nor a Platypus: a Reexamination of Necrolestes patagonensis Ameghino. American Museum Novitates 3546:1-40.
Ladevèze S, Asher RJ, Sánchez-Villagra MR 2008. Petrosal anatomy in the fossil mammal Necrolestes: evidence for metatherian affinities and comparisons with the extant marsupial mole. J Anat 213(6):686–697.
Patterson B 1958. Affinities of the Patagonian fossil mammal Necrolestes. Breviora Mus Comp Zool 94:1–14.
Rougier GW, Wible JR,  Beck RMD and Apesteguía S 2012. The Miocene mammal Necrolestes demonstrates the survival of a Mesozoic nontherian lineage into the late Cenozoic of South America.
Saban R 1954. Phylogénie des insectivores [Phylogeny of the insectivores]. Bull Mus Natl d’Hist Nat. Ser 2 26:419–432. in French
Van Valen L 1988. Faunas of a southern world. Nature 333(6152):113.

Tetrapod Zoology on golden moles

Wrist supination/pronation in Megalancosaurus?

Megalancosaurus including the palate, the only palate ever figured for a drepanosaur.

Figure 8. Megalancosaurus including the palate, the only palate ever figured for a drepanosaur.

One of the weirdest of the weird
Megalancosaurus has been studied and published previously (see refs below). A recent addition (Castiello et al. 2016) adds fused clavicles, a saddle-shaped glenoid, a tight connection between the radius and ulna that hindered pronation/suppination (but see below) and hypothetical forelimb muscles to our knowledge of this basal lepidosauriform.

Unfortunately 
the authors only go as far as labeling this taxon a drepanosaur and a drepanosauromorph without further identifying the larger and even larger clades these taxa nest within.

News

  1. “unlike those of other drepanosauromorphs [the clavicles] are fused together and possess a small median process caudally directed so that the whole structure looks similar to the furcula of theropod dinosaurs, especially oviraptorids.”
  2. “The scapular blade reaches the modified, expanded neural spines of the third and fourth dorsal vertebra so that the pectoral girdle formed a solid ring, which would have been very rigid.”
  3. “the glenoid fossa has a saddle-shaped structure and lies on the coracoid”
  4. “paired sternal plates are fused to the coracoids forming a craniocaudally elongate coracosternal complex.”
  5. “the coracosternal complex was more vertically oriented than in previous reconstructions” but as figured for Drepanosaurus and Megalancosaurus (Fig. 1) at ReptileEvolution.com.
  6. Rather than a separate olecranon sesamoid (Figs. 1, 2) that Megalancosaurus and all of its sisters share, the authors report on, “the elongate olecranon process of the ulna.”
  7. Rather than recognizing a bone break in the ulna (Fig. 2), the authors report, “a small notch is present on the medial margin of the ulna distal to the articular surface for the humerus. This notch houses the medial corner of the proximal head of the radius, suggesting that in life, the two bones were firmly connected together at their proximal end, preventing pronation and supination of the forearm.” No other sister taxa or tetrapods have such an ulna notch. Note, the notch is not present in figure 2, but the sesamoid is pretty broken up. These bones are hollow, fragile and crushed. Be careful how you interpret them. Earlier we saw another misinterpretation of a drepanosaur forelimb.
  8. When the authors present a hypothetical forelimb myology they do not present a pertinent actual forelimb myology (Fig. 3) for comparison. Such a comparison helps assure the reader that the myology for Megalancosaurus has not been invented and follows actual patterns and sizes.
Megalacosaurus elbow

Figure x. The break and the broken pieces of the Megalancosaurus ulna are reidentified here. The sesamoid is prominent and crescent-shaped as in Drepanosaurus.

Crushed hollow bones
are sometimes difficult to interpret, as we’ve seen before.

Elbow sesamoid in another specimen of Megalancosaurus, MPUM 8437.

Figure 2. Elbow sesamoid in another specimen of Megalancosaurus, MPUM 8437.

The authors provided a hypothetical myology
which they phylogenetically bracketed by lepidosaurs and crocodilians (which means what??) based on prior pterosaur forelimb myology as imagined by Bennett (2003, 2008). Pterosaurs are unrelated to drepanosaurs. The Bennett pterosaur myology had problems because it located extensors and flexors anterior and posterior to the fore arm, rather than dorsal and ventral (palmar) as in Sphenodon (Fig. 3) the closest living taxon to drepanosaurs AND pterosaurs.

Sphenodon hand muscles

Figure 3 Sphenodon hand muscles. Click to enlarge. These were not referenced in the Castiello et al. study.

It would have been appropriate

  1. to show that the fingers of Megalancosaurus had more phalanges (Fig. 4), as seen in sister taxa and as I see them in Megalancosaurus itself.
  2. to show two versions of the manus, with spread metacarpals (as presented) and another with more closely appressed metacarpals, as in sister taxa, Hypuronector, Vallesaurus, and Drepanosaurus (Fig. 4).
  3. to take a closer look at that ulna notch, knowing that such a notch mechanically weakens the cylinder, is produced by broken bone, and is not repeated in other drepanosaurs.
  4. to take a closer look at that olecranon ‘process’ because sister taxa all have a large sesamoid.
  5. to phylogenetically nest drepanosaurs in order to provide the most accurate myology analogy possible.
The sister taxa of Drepanosaurus

Figure 4. Click to enlarge. The sister taxa of Drepanosaurus all had an olecranon sesamoid. Drepanosaurus simply had a larger one.

The above data
has been online for the past six years. Plenty of time to consider it. No need to cite it.

Pronation/supination
Arboreal taxa in general and distant drepanosauromroph sisters (Palaegama and Jesairosaurus) are able to axially rotate the forearm by at least some degree. Like the human forearm, the radius and ulna in these taxa are separated by a long oval space that enables the radius to axially rotate on the ulna.

By contrast 
the radius and ulna of Hypuronector are appressed (Fig. 4), restricting pronation/ supination. Vallesaurus may have been similar, but taphonomic disarticulation makes it difficult to tell. The forearm was relatively shorter than the humerus. Drepanosaurus had a similar short forearm, but also had a giant elbow sesamoid that essentially extended the humerus, separated the proximal radius and ulna, as in birds, but shifted the radius to the sesamoid, deleting the parallelogram effect — AND likely reducing pronation and supination.

Unlike its sisters, but like humans,
the radius and ulna of Megalancosaurus were slender, elongate and separated by an interosseus space. I don’t see any reason to suggest that pronation and supination were restricted to 0º here, but not nearly to the extent found in humans (Homo), about 180º. The radius in Megalancosaurus still appears to articulate with the humerus and if re-inflated from its crushed state, might be a cylinder with a circular proximal articulation, enabling pronation and supination.

References
Bennett SC 2003. Morphological evolution of the pectoral girdle of pterosaurs: myology and function. In: Buffetaut E, Mazin J-M, editors. Evolution and palaeobiology of pterosaurs. Geol Soc Spec Publ. 217. London (UK): Geological Society of London. p. 191–215.
Bennett SC 2008. Morphological evolution of the forelimb of pterosaurs: myology and function. In: Buffetaut E, Hone DWE, editors. Flugsaurier: pterosaur papers in honour of Peter Wellnhofer. München: Zitteliana. B28. p. 127–141.
Calzavara M, Muscio G and Wild R 1980. Megalancosaurus preonensis n. gen. n. sp., a new reptile from the Norian of Friuli. Gortania 2: 59-64.
Castiello M, Renesto S and Bennett SC 2016. The role of the forelimb in prey capture in the Late Triassic reptile Megalancosaurus (Diapsida, Drepanosauromorpha). Historical Biology DOI: 10.1080/08912963.2015.1107552
Feduccia A and Wild R 1993. Birdlike characters in the Triassic archosaur Megalancosaurus. Natur Wissenschaften 80:564–566.
Geist NR and Feduccia A 2000. Gravity-defying Behaviors: Identifying Models for Protoaves. American Zoologist 4):664-675. online pdf
Renesto S 1994. Megalancosaurus, a possibly arboreal archosauromorph (Reptilia) from the Upper Triassic of Northern Italy. Journal of Vertebrate Paleontology 14(1):38-52.
Renesto S 2000. Bird-like head on a chameleon body: new specimens of the enigmatic diapsid reptile Megalancosaurus from the Late Triassic of Northern Italy. Rivista Italiana di Paleontologia e Stratigrafia 106: 157–179.

wiki/Megalancosaurus

Meiolania eggs confirm basal turtle status

Earlier the horned turtles, Meiolania and Niolamia, were nested in the large reptile tree (LRT) as basalmost hardshell turtles, closely related to the toothed horned stem turtle/pareiasaur, Elginia. This was heresy when introduced.

Now
newly discovered turtle eggs (Lawver and Jackson 2016) add evidence to the basal status of Meiolania.

From the Lawver and Jackson 2016 abstract:
“A fossil egg clutch from the Pleistocene of Lord Howe Island, Australia that we assign to Testudoolithus lordhowensis, oosp. nov. belongs to the stem turtle Meiolania platyceps.  Thin sections and scanning electron microscopy demonstrate that these eggs are composed of radiating acicular aragonite crystals. This mineral composition first evolved either before the split between Meiolaniformes and crown Testudines or prior to Proterochersis robusta, the earliest known stem turtle. Meiolania platyceps deposited its eggs inside an excavated hole nest. This nesting strategy likely evolved no later than the Early to Middle Jurassic.”

All known meiolanids
are from later, higher Late Cretaceous and Tertiary strata.

Figure 5. Meiolania, the most primitive of known turtles, has lateral forelimbs, like non turtles.

Figure 1. Meiolania, one of the most primitive of known hard-shell turtles, has lateral forelimbs, like non turtles. All extant turtles have anteriorly-directed humeri. It also had cranial horns, like the toothed pareiasaur/turtle? Elginia.

At present,
soft-shell and hard-shell turtles have a dual origin from separate small Late Permian and Middle Triassic pareiasaur ancestors, Elginia and Sclerosaurus. Both were also horned. The traditional earliest known turtles, Proganochelys and Odontochelys are both known from later, Late Triassic, strata.

Not on topic, but worth watching on YouTube:
Here’s a video about the origin of oil in the Jurassic. It runs for 90 minutes and is fascinating throughout. The video reminds us what a recent Golden Age we currently live in based on a limited supply of petroleum products. The video concludes we have long passed the tipping point for climate change based on the flood of cheap energy. And the end of the oil age is something our children will see. Ironically, climate change in the ice-free Jurassic was one factor in the Earth producing the oil we now use.

References
Lawver DR and Jackson FD 2016. A fossil egg clutch from the stem turtle Meiolania platyceps: implications for the evolution of turtle reproductive biology. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1223685.

Forfexopterus: a Huanhepterus sister

Boy, it’s been a long time
since we’ve looked at a new pterosaur. Several months, perhaps… maybe longer…

Figure 1. Forfexopterus reconstructed. Note the metacarpals: 1>2>3, shared with Ardeadactylus. The rostrum tip is off the matrix.

Figure 1. Forfexopterus reconstructed. Note the metacarpals: 1>2>3, shared with Ardeadactylus. The rostrum tip is off the matrix. Note the difference between the actual fingers and the traced fingers by Jiang et al. The lack of precision in the Jiang et al. tracing, despite it being traced from a photograph, is a little disheartening.

Jiang et al. 2016
present a new disarticulated, but largely complete Early Cretaceous pterosaur, Forfexopterus jeholensis (Figs. 1–3). Jiang et al. consider their new find an ‘archaeopterodactyloid’ based on the ‘long metacarpus and reduced mt5’–but those are convergent traits in four pterodactyloid-grade clades. The large pterosaur tree (LPT) nests Forfexopterus near the base of the azhdarchid clade, which arises from the Dorygnathus clade, specifically nesting between Ardeadactylus and Huanhepterus + Mesadactylus (BYU specimen, not the anurognathid with the same name).

Figure 1. Forfexopterus original tracing, colors added.

Figure 2. Forfexopterus original tracing, colors added. See how simple colors ease the chaos of the roadkill fossil.

Unfortunately 
the Jiang et al. phylogenetic analysis suffers from taxon exclusion. They consider the Archaeopterodactyloidea to be composed of Germanodactylidae, Pterodactylus, Ardeadactylus. Gallodactylidae and Ctenochasmatidae. Those members are only monophyletic if the clade also includes Dorygnathus in the LPT, which was not the intention of the authors. It’s been awhile, but let us recall that the former clade “Pterodactyloidea” had four separate origins in the LPT, two from Dorygnathus (Ctenochasmatidae and Azhdarchidae) and the rest from Scaphognathus which was, in turn, also derived from Dorygnathus through several intervening transitional taxa.

Figure 2. Forfexopterus compared to sisters Huanhepterus and Ardeadactylus and the BYU specimen of Mesadactylus.

Figure 3. Forfexopterus compared to sisters Huanhepterus and Ardeadactylus and the BYU specimen of Mesadactylus.

Forfexopterus
has the slender proportions of Huanhepterus and Ardeadactylus. The rostrum was longer and lightened with several fenestra, one of which was likely a naris. Metacarpals 1–3 were longer medially, the opposite of basal pterosaurs. That trait lines up the joints in m1-3. Manual 4.2 is sub equal to m4.1, unique to this clade and atypical for pterosaurs in general.  Atypical for smaller members of this clade, but typical for larger members (like Jidapterus, but evidently not Huanhepterus (data comes from awkwardly produced original drawing)), the scapula was subequal to the coracoid and would have articulated with a notarium, which is not preserved, or is still largely buried (Fig. 2).

Shorthand suggestion (again)
There are two ways you can label a tetrapod phalanx:

  1. ph3d4 = phalanx 3, digit 4 (manus or pes? as shown in figure 2 above) or
  2. m4.3 = manual 4th digit, 3rd phalanx

Jiang et al. labeled their illustration using #1. You may find that method cumbersome and space consuming. I use and encourage others to use #2, the shorthand version.

When you check out the
Wikipedia page on Forfexopterus, the link to Archaeopterodactyloidea references three papers with Dr. Brian Andres as a co-author including his dissertation on
Sytematics of the Pterosauria. It’s great that PhD candidates tackle large projects. It’s hard work that makes them study their subject and prove their mettle. However, by definition, PhD candidates are not experts. They want to become experts by creating a dissertation, but they come to their projects naive, trusting the literature and beholding to their professors. These are all potential problems, as we talked about earlier.

In like manner, 
for my second paper (Peters 2000) I came to the project naive and trusting the literature. Judging from a vantage point, 17 years later, my observations were not those of an expert. Even so, I hit the mark with regard to pterosaur origins despite the many errors in that paper that have been corrected here and at ReptileEvolution.com. The nesting of pterosaurs apart from archosaurs and close to Macronemus, Tanystropheus, Langobardisaurus, Cosesaurus, Sharovipteryx and Longisquama has been validated and cemented by the large reptile tree (LRT). No other candidate taxa have ever been shown to be closer (= produce a gradual accumulation of derived traits). Attempts at correcting the observational errors in academic publications have been rejected by the referees who don’t want any more evidence published that pterosaurs are not dinosaur kin — or that tiny Solnhofen pteros are not babies.

Unfortunately
the Andres dissertation fails to produce a cladogram in which a gradual accumulation of traits can be traced in all derived taxa. For instance, anurognathids are basal to pterodactyloids in the Andres cladogram and the clade Archaepterodactyloidea was recovered. The Andres dissertation shortcoming can be attributed to taxon exclusion. By contrast, the LPT minimizes taxon exclusion by including many specimens ignored by Andres and other prior workers including multiple species within several genera and all those sparrow- and hummingbird-sized Solnhofen specimens. I know pterosaur workers are loathe to admit it, or recognize it, but those extra specimens are key to understanding pterosaur interrelations.

If you don’t look, you’ll never see.
If you don’t ask, you’ll never find out. Fellow pterosaur workers, don’t keep your blinders on. Expand your taxon lists to include a wider gamut of specimens.

This is Science.
When workers publish and referee allow manuscripts to be published they are judging the work fit for print. At that point they have stated their case. If the work stands up to rigorous scrutiny, then it will be cherished. If the work has flaws, then it’s up to fellow workers to expose those flaws for the good of Science.

References
Andres BBB 2010. Systematics of the Pterosauria. Dissertation. Yale University. p. 366.
Jiang S, Cheng X, Ma Y and Wang X 2016. A new archaeopterodactyloid pterosaur from the Jiufotang Formation of western Liaoning, China, with a comparison of sterna in Pterodactylomorpha. Journal of Vertebrate Palaeontology: e1212058.
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.

wiki/Forfexopterus
wiki/Archaeopterodactyloidea

Lacerta: where is the upper temporal fenestra?

Lacerta viridis (Fig. 1) is a common extant lizard that has more skull bones than is typical for most tetrapods. It also loses the upper temporal fenestra found in other lizards, by posterior expansion of the postfrontal.

Figure 1. Lacerta viridis skull from Digimorph.org and used with permission. Here the enlargement of the postfrontal basically erases the former upper temporal fenestra. Several novel ossifications appear around the orbit and cheek.

Figure 1. Lacerta viridis skull from Digimorph.org and used with permission. Here the enlargement of the postfrontal basically erases the former upper temporal fenestra. Several novel ossifications appear around the orbit and cheek.

This Digimorph.org image
was colorized in an attempt at understanding the skull bones present here. The extant Lacerta nests with the larger extinct Eolacerta in the large reptile tree (918 taxa).

40 species are known of this genus.
Fossils are known from the Miocene (Čerňanský 2010). The tail can be shed to evade predators. This lizard is an omnivore. The curled quadrate frames an external tympanic membrane (eardrum). With the premaxillae fused, Lacerta has nine premaxillary teeth, with one in the center.

Not sure why this lizard developed extra skull bones.
It is found in bushy vegetation at woodland and field edges, and is not described as a burrower or a head basher.

Other diapsid-grade reptiles that nearly or completely lose the upper temporal fenestra include:

  1. Mesosaurus
  2. Chalcides
  3. Acanthodactylus
  4. Phyrnosoma
  5. Minmi

References
Čerňanský A 2010. Earliest world record of green lizards (Lacertilia, Lacertidae) from the Lower Miocene of Central Europe. Biologia 65(4): 737-741.
Linnaeus C 1758.
Systema naturæ per regna tria naturæ, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. Tomus I. Editio decima, reformata.

Lacerta viridis images online
wiki/Lacerta