Martensius enters the LRT between Milleretta and the Caseasauria

Figure 1. Ffrom Berman et al. 2020, skull of Martensius in two views, plus full scale.

Figure 1. Ffrom Berman et al. 2020, skull of Martensius in two views, plus full scale.

Martensius bromackerensis (Berman et al. 2020; Early Permian, 50cm; MNG 13814 adult holotype; MNG 14230 juvenile and smallest specimen; Figs. 1, 2) is the basalmost taxon in the caseasauria, derived from Milleretta (Fig. 4) in the large reptile tree (LRT, 1660+ specimens; subset Fig. 3). Four specimens of Martensius were found together, from a juvenile to an adult. A small skull is apparent here, a trait that continues in most caseasaurs. Uniquely the majority of the bottom of the naris is the maxilla.

Figure 2. The juvenile specimen of Martensius.

Figure 2. The juvenile specimen of Martensius.

Berman et al. did not test the outgroup taxon,
Milleretta, nor any casesaur kin, like Feeserpeton, Australothyris, Acleistorhinus, Eunotosaurus, nor any other lepidosauromorphs in their phylogenetic analysis. Instead they  followed tradtion by assuming casesaurs were synapsids. Testing invalidated that hypothesis of interrelationships several years ago.

Figure 3. Subset of the LRT with Martensius added to the base of the Caseasauria + another clade of similar lepidosaurs, all derived from Milleretta.

Figure 3. Subset of the LRT with Martensius added to the base of the Caseasauria + another clade of similar lepidosaurs, all derived from Milleretta.

The authors expressed some concern
about Eocasea, which they considered basal to the Caseasauria. It is, but only when several taxa are omitted (see Fig. 3 for that list). Add taxa and such concerns go away. Adding taxa minimizes taxon exclusion problems. Eocasea nests closer to Delorhynchus than to any caseasaur.

Figure 2. Milleretta, caseasaurs and kin. The LRT nests these taxa together apart from the Synapsida, with which they share a lateral temporal fenestra.

Figure 4. Milleretta, caseasaurs and kin. The LRT nests these taxa together apart from the Synapsida, with which they share a lateral temporal fenestra.

On a similar note,
earlier another group of paleontologists considered a taxon ‘a bird/dinosaur’ in amber when it was really a lepidosaur. The finger-pointing thereafter was pretty intense. I don’t expect the same sort of upwelling to attend this phylogenetic mistake because Berman et al. considered a taxon a synapsid when it was really a lepidosauromorph. This corner of the phylogenetic tree doesn’t touch as many emotional buttons and the big Kahuna has not yet reached a wider audience. Taxon exclusion remains the problem.


References
Berman DS, Maddin HC, Henrici AC Sumida SS, Scott D and Reisz R 2020. New primitive caseid (Synapsida, Caseasauria) from the Early Permian of Germany. Annals of the Carnegie Museum 86(1):43–75.

A slight adjustment to an OMNH Cotylorhynchus reconstruction

The AMNH specimen
of Cotylorhynchus is a spectacular sight to see (Fig. 1). It’s huge! And complete! It’s bigger than a Galápagos tortoise with a skull just as small.

Figure 1. Cotylorhynchus AMNH specimen. Note the angle of the ribs.

Figure 1. Cotylorhynchus AMNH specimen. Note the angle of the ribs. Is that a whip-lash tail? Compare to Datheosaurus (Fig. 4). Just look at those massive elbows!

Romer and Price 1940
pictured Cotylorhynchus with vertical dorsal ribs (Fig. 2 lateral view).

Cotylorhynchus romeri

Figure 2. Cotylorhynchus romeri

The Sam Noble Museum Oklahoma’s Museum of Natural History
in Norman, Oklahoma, USA, has a mount of Cotylorhynchus (Fig. 3) that follows the Romer and Price illustration with vertical ribs. Here, in this 2-frame GIF animation, I have angled them back to match the in situ specimen and most other quadrupedal tetrapods.

Figure 3. Cotylorhynchus mount in the Sam Noble Museum of Natural History with vertical ribs modified here to have diagonal ribs more typical of tetrapods and reflective of the in situ fossil.

Figure 3. Cotylorhynchus mount in the Sam Noble Museum of Natural History with vertical ribs modified here to have diagonal ribs more typical of tetrapods and reflective of the in situ fossil.

Cotylorhynhcus romeri (Stovall 1937) Kungurian, Middle Permian, ~265 mya, ~6 m in length, was the largest sister to Casea and Ennatosaurus. It was the largest land animal of its time.

Figure 2. Milleretta, caseasaurs and kin. The LRT nests these taxa together apart from the Synapsida, with which they share a lateral temporal fenestra.

Figure 4. Milleretta, caseasaurs and kin. The LRT nests these taxa together apart from the Synapsida, with which they share a lateral temporal fenestra. Note the angle of the ribs in the Milleretta reconstruction, similar to the suggestion for Cotylorhynchus. Casea and Ennatosaurus continue to have invalid vertical ribs in the above figure due to my laziness.

All prior and other current reports
nest Cotylorhynchus with the synapsid pelycosaurs, but here in the large reptile tree (LRT. 1315 taxa) the caseid clade nests more parsimoniously with Milleretta, Feeserpeton and Australothyris and other plant-eaters, many of which share a lateral temporal fenestra in the new Lepidosauromorpha, opposite to the coeval pelycosaurs nesting in the new Archosauromorpha.

We looked at this traditional mistake
based on taxon exclusion here back in 2011. Even so, synapsid workers continue to follow this outdated tradition without testing validated alternatives proposed here.

References
Romer AS and Price LI 1940. Review of the Pelycosauria. Geological Society of America Special Papers 28: 1-538.
Stovall JW 1937. Cotylorhynchus romeri, a new genus and species of pelycosaurian reptile from Oklahoma. Arnerican Journal of Science (5) 34: 308-313.
Stovall JW, Price LI and Romer AS 1966. The Postcranial Skeleton of the Giant Permian Pelycosaur Cotylorhynchus romeri. Bulletin of the Museum of Comparative Zoology 135 (1): 1-30. online pdf

wiki/Cotylorhynchus

Caseid diaphragms? Bogus, bogus, bogus…

Lambertz et al. 2016 imagine
a diving aquatic niche for caseids like Cotylorhyhnchus (Fig. 1), and in order to breathe upon surfacing, a mammal-like diaphragm must have been present.

One of the authors, Dr. Steven Perry, has been working on the origin of the diaphragm for many years. Perry et al. 2010 wrote: despite over 400 years of research into respiratory biology, the origin of this exclusively mammalian structure remains elusive.” (But see below)

According to Wikipedia: “Mammals have diaphragms, and other vertebrates such as amphibians and reptiles have diaphragm-like structures, but important details of the anatomy vary, such as the position of the lungs in the abdominal cavity.” 

And Tegu lizards are known to possess a proto-diaphragm, which separates the pulmonary cavity from the visceral cavity. While not actually capable of movement, it does allow for greater lung inflation, by taking the weight of the viscera off the lungs.”

And “Crocodilians have a muscular diaphragm that is analogous to the mammalian diaphragm. The difference is that the muscles for the crocodilian diaphragm pull the pubis (part of the pelvis, which is movable in crocodilians) back, which brings the liver down, thus freeing space for the lungs to expand.” 

And this important and pertinent note to pet lizard owners:
“If you turn them over and stroke their bellies, they zonk out… Cute?.. NO, Stop! Lizards do not have diaphragms to help them breath. Their ribs moving in and out actually cause their lungs to inflate and deflate. When a dragon is held upside down or on its back, its stomach pushes on its lungs making it difficult for it to breath and will eventually result in suffocation.” Other similar cautionary notes are compiled here.

Unfortunately, Lambertz et al. also revert to an old invalid tradition,
that caseids are basal synapsids. For over five years it has been known that caseids are not basal to synapsids. The large reptile tree nests caseids as sisters to Feeserpeton and Australothyris and all are derived from a sister to Milleretta within the Lepidosauromorpha, not the Archosauromorpha, in which the Synapsida nests. Thus if you want to know if caseids had a diaphragm, you need to look at living lizards, all of which lack a working diaphragm.

Cotylorhynchus romeri

Figure 1. Cotylorhynchus romeri. Extant lizards lack a diaphragm, so caseids also lacked a daphragm.

Given that backstory Lambertz et al. report:
“The origin of the diaphragm remains a poorly understood yet crucial step in the evolution of terrestrial vertebrates, as this unique structure serves as the main respiratory motor for mammals. Here, we analyze the paleobiology and the respiratory apparatus of one of the oldest lineages of mammal-like reptiles: the Caseidae. [1] Combining quantitative bone histology and functional morphological and physiological modeling approaches, we deduce a scenario in which an auxiliary ventilatory structure was present in these early synapsids. Crucial to this hypothesis are indications that at least the phylogenetically advanced caseids might not have been primarily terrestrial but rather were bound to a predominantly aquatic life. Such a lifestyle would have resulted in severe constraints on their ventilatory system, which consequently would have had to cope with diving-related problems. [2] Our modeling of breathing parameters revealed that these caseids were capable of only limited costal breathing and, if aquatic, must have employed some auxiliary ventilatory mechanism to quickly meet their oxygen demand upon surfacing. [3] Given caseids’ phylogenetic position at the base of Synapsida [4] and under this aquatic scenario, it would be most parsimonious to assume that a homologue of the mammalian diaphragm had already evolved about 50 Ma earlier than previously assumed.” [5]

  1. Not valid for the last five years. Caseids are derived from millerettids and are related to non-synapsids with a convergent lateral temporal fenestra. Hence the confusion.
  2. No one imagines caseids as divers. Maybe shoulder deep in shallow streams.
  3. Diving turtles have no such problems upon surfacing.
  4. Wrong again. See above.
  5. This is a ‘just-so’ story built on taxon exclusion and a couple of big IFs. See below for a hypothesis built on phylogenetic bracketing and skeletal morphology.

So while we’re on the topic of diaphragms,
let’s take a look at another possibility in stem mammals. Since basalmost mammals, like the platypus, Ornithorhynchus, have a diaphragm we’re looking for the origin of this lung muscle in earlier taxa.

A likely place to look 
is at the transition from lateral undulation to limb rotation during locomotion. Only at that stage, where both lungs can inflate simultaneously during locomotion (see Carrier’s constraint), can the diaphragm develop.

Figure 2. Chiniquodon had erect hind limbs and sprawling forelimbs, the first stage in parasagittal locomotion, a requirement for the invention of the diaphragm.

Figure 2. Procynochus, Thrinaxoon, Chiniquodon transition to erect hind limbs while keeping sprawling forelimbs. This was the first stage in parasagittal locomotion, a requirement for the invention of the diaphragm and the most likely stage for its origin.

That transition began with the hind limbs on
derived cynodonts (Fig. 2) which slowly evolved parasagittally rotating hind limbs while retaining sprawling fore limbs. Monotreme mammals continue to retain sprawling forelimbs. Parasagittal forelimbs first appear with Juramaia and the later Therians.

Coincidentally (#1)
The lumbar ribs began to shrink in derived cynodons (Fig. 2) disappearing completely in basalmost mammals.

Coincidentally (#2)
The dorsal rib cage becomes pear-shaped in dorsal view (Fig. 3), with narrower ribs anteriorly and wider ribs posteriorly, near the developing diaphragm.

Coincidentaly (#3)
The dorsal vertebrae become differentiated into dorsal and lumbar vertebrae with neural spines angled posteriorly and anteriorly respectively and shorter and longer vertebral lengths respectively.

Coincidentally (#4)
Sternal ribs, sternebrae, a manubrium and xiphoid process all appear in basalmost mammals, likely signaling the completion of the evolution of the diaphragm.

Coincidentally (#5)
the vertebral column in vivo develop an arch in lateral view (Fig. 3) with a rise to the base of the rib cage followed by a lumbar decent to the sacrals.

Coincidentally (#6)
The external nares become anteriorly oriented, confluent and the premaxillary ascending process disappears, facilitating greater volumes and velocities with every breath.

Figure 1. Megazostrodon, an early mammal, along with Hadrocodium, a Jurassic tiny mammal.

Figure 3 Megazostrodon, an a Jurassic mammal, along with Hadrocodium, a Jurassic tiny mammal.

In summary
in the transition from Cynodontia to Mammalia many changes occurred in the rib cage. Such changes are the most likely skeletal markers for the origin of the soft tissue diaphragm. Such changes are not seen in caseids, which, in any case, are related to lizards not mammals.

I have not read the Lambertz paper,
only the abstract, but with caseids unrelated to mammals, they are sadly barking up the wrong tree. Based on a false premise, that paper was a complete waste of time to produce. Build your papers on a solid phylogenetic foundation and everything will into place naturally.

References
Lambertz M, Shelton CD, Spindler F & Perry SF 2016. A caseian point for the evolution of a diaphragm homologue among the earliest synapsids. Annals of the New York Academy of Sciences (advance online publication) DOI: 10.1111/nyas.13264. http://onlinelibrary.wiley.com/doi/10.1111/nyas.13264/full
Merrell AJ and Kardon G 2013. Development of the diaphragm – a skeletal muscle essential for mammalian respiration. FEBS Journal 280(17): 4026-4035.
Perry SF, Similowski T, Klein W and Codd JR 2010. The evolutionary origin of the mammalian diaphragm. Repiratory Physiology & Nuerobiology 171(1):1-16.
Zimmer C. 2015. Behind Each Breath, an Underappreciated Muscle. The New York Times 04/07/2015.

Vaughnictis (Brocklehurst et al. 2016): a new last common ancestor of birds and bats

Recently Brocklehurst et al. 2016
renamed ‘Mycterosaurus’ smithae (Lewis and Vaughn 1965; early Permian, MCZ 2985). The new name is Vaughnictis smithae. The specimen was originally considered a varanopid close to the holotype of Mycterosaurus (Fig. 1). Now the Brocklehurst team nest the MCZ 2985 specimen between Eothyris and Oedaleops (Fig. 1) at the base of the Caseasauria, which they consider a clade at the base of the Synapsida.

Unfortunately, 
the large reptile tree nests Vaughnictis at the bases of two major clades: between Protorothyris and the Synapsida (represented here (Fig. 1) by Elliotsmithia) + the Prodiapsida (represented here by Mycterosaurus). The Caseasauria, as noted five years ago here, does not nest with the Synapsida when the taxon list is expanded, and the Prodiapsida (former varanopids) split from the Synapsida at their base when the taxon list is expanded.

Figure 2. Vaughnictis nests between Protorothyris and the Synapsida (Elliotsmithia) + Prodiapsida (Mycterosaurus) in the large reptile tree - not the Caseasauria (Eothyris + Oedaleops).

Figure 1. Vaughnictis nests between Protorothyris and the Synapsida (Elliotsmithia) + Prodiapsida (Mycterosaurus) in the large reptile tree – not the Caseasauria (Eothyris + Oedaleops). Despite the many similarities, the narrow skull with parallel sides, upturned mandible tip and longer rostrum are a few traits that split Vaughnictis from caseasaurs and lump it with prosynapsids.

Lewis and Vaughn got it right.
Vaughnictis is a sister to Mycterosaurus in the LRT. It is not a caseasaur.

Brocklehurst et al. got it right
in that Vaughnictis is distinct enough from Mycterosaurus to warrant its own genus.

Despite their phylogenetic distance
only 22 additional steps are needed when Vaughnictis is force shifted over to Eothyris. This is largely due to convergence. Both clades developed lateral temporal fenestrae in similar patterns, had large eyes and a short rostrum at this stage.

Figure 2. Vaughnictis skull in situ with color tracings. See figure 3 for reconstruction.

Figure 2. Vaughnictis skull in situ with color tracings. See figure 3 for reconstruction. The jaws shifted posteriorly during taphonomy The parietal and its opening are difficult to read.

The phylogenetic importance of Vaughnictis
was overlooked by Brocklehurst et al. It is the most primitive known specimen in the lineage of synapsids and diapsids to have a lateral temporal fenestra. That’s why it is the last common ancestor of bats and birds, an honor formerly earned by Protorothyris, but now superseded by a taxon with lateral temporal fenestrae.

Figure 1. Color tracings of bones moved to their in vivo positions and traced.

Figure 3. Color tracings of bones moved to their in vivo positions and traced. Note the anterior shifting of the jaws to their in vivo positions based on posterior dentary and jugal positions common to most if not all candidate sister taxa. 

I wish that Brocklehurst et al. had 

  1. created a multi-view reconstruction
  2. showed candidate sisters side by side compared to Vaughnictis
  3. not excluded pertinent taxa (diapsids for the former varanopids and millerettids for the caseasaurs)
  4. used colors to identify bones, rather than lines, which helps when bones overlap. They did color the teeth (Fig. 4), but not all the teeth.
Figure 6. Teeth scanned by Brocklehurst fit to dorsal view of skull. Premaxillary and maxillary teeth were not published. Note the scale bar for the teeth appears to be off by a factor of 2.

Figure 4. Teeth scanned by Brocklehurst fit to dorsal view of skull. Premaxillary and maxillary teeth were not published. Note the scale bar for the teeth appears to be off by a factor of 2. Also note the premaxillary teeth appear to be jammed back from their in vivo position. 

The interesting thing about their cladogram
is that the Brocklehurst team nested Captorhinus, Limnoscelis and Tseajaia as outgroup taxa — which is correct for Caseasauria, but not for Synapsida. Protorothyris is also listed as the proximal outgroup to the Caseasauria (incorrect) + Synapsida (correct). It is clear they rely on tradition, rather than testing for their inclusion set.

In Vaughnictis, as opposed to Eothyris, note the 

  1. relatively narrow skull
  2. the rising mandible tip
  3. the lack of maxilla/orbit contact
  4. the shorter temporal length
  5. the lower rostrum

These traits ally Vaughnictis with Elliotsmithia to the exclusion of basal caseasaurs.

Brocklehurst et al. note:

  1. Vaughnictis lacks these mycterosaurine and varanopid traits (but it is not a member of either of these clades in the LRT) :
    a. slender femur
    b. linguo-labially compressed and strongly recurved teeth – I disagree, the teeth are indeed recurved
    c. lateral boss on the postorbital – I don’t see this on candidate taxa
  2. Vaughnictis has these caseasaur traits:
    a. coronoid teeth – plesiomorphic for synapsids, but they have been lost in derived caseids, ophiacodontids, varanopids and sphenacodontians. Most workers do not include these in their tracings of pertinent taxa, so are rarely noted.
    b. large supratemporal – actually they are long, as in synapsids, not large (and wide) as in caseasaurs
    c. large pineal foramen – unable to confirm, but Elliotsmithia and Mycterosaurus also have a large pineal foramen.

Teeth
Broklehurst et al. published synchrotron scans of the palatal, dentary and coronoid teeth (perhaps the scale bar should be 1 cm, not 5mm, Fig. 4), but did not publish scans of the maxillary teeth. All of the palatal teeth form shagreen fields, not single rows. That’s different than all candidate sister taxa, whether caseasaurid or protorothyrid. What they label as “vomerine teeth” may be premaxillary teeth based on the posterior displacement of the jaws. The dentary teeth are recurved and robust. Coronoid and parasphenoid teeth are present.

Figure 6. Subset of the large reptile tree showing the nesting of Vaughnictis at the base of the Synapsida and Prodiapsida.

Figure 5. Subset of the large reptile tree showing the nesting of Vaughnictis at the base of the Synapsida and Prodiapsida. Also note that the Synapsida is NOT the first clade to branch off from the base of the Amniota. Far from it.

This Brocklehurst team was led by
the venerable Robert Reisz, who has made dozens of great discoveries, but has resisted testing candidates suggested by the large reptile tree. And that sort of paleoxenophobia is unfortunate. Outsiders can make valuable contributions.

Finally, kudos and credit to the Brocklehurst team,
for finding the one best specimen closest to the advent of the Synapsida + Prodiapsida. It should be in every textbook from here on out.

References
Brocklehurst N, Reisz RR, Fernandez V and Fröbisch 2016. A Re-Description of ‘Mycterosaurus’ smithae, an Early Permian Eothyridid, and Its Impact on the Phylogeny of Pelycosaurian-Grade Synapsids. PLoS ONE 11(6):e0156810. doi:10.1371/journal.pone.0156810
Lewis GE, Vaughn PP 1965. Early Permian vertebrates from the Cutler Formation of the Placerville Area, Colorado. Geological Survey Professional Paper 500C: 1–50.
Reisz RR, Dilkes DW and Berman DS 1998. Anatomy and relationships of Elliotsmithia longiceps Broom, a small synapsid (Eupelycosauria: Varanopseidae) from the late Permian of South Africa. Journal of Vertebrate Paleontology 18(3):602-611.