Masrasector: not a placental… a killer marsupial

Of course, by that I mean,
skunk-sized Masrasector nananubis (Fig. 1; Simons and Gingerich 1974; Borths and Seiffert 2017), like other hyaenodonts in the LRT (Fig. 2), is also a marsupial… a descendant of a sister to the quiet little, nocturnal Virginia opossum (Didelphis, Fig. 2), but closer to Borhyaena.

[Note: everyone agrees that hyaenodonts are NOT related to hyaenas.]

Taxon exclusion,
based on tradition, evidently keeps marsupials out of current phylogenetic analyses of hyaenodonts. Hopefully that will be corrected, or at least tested, in the future.

Hyaenodonts,
like Masrasector, are traditionally considered placental (eutherian) carnivorous creodonts. They have not one, but three carnassial teeth.

According to the LRT,
that was by convergence. Certain bats also have carnassial teeth. So it can happen.

By contrast
the large reptile tree (LRT, 1066) nests Masrasector and all other hyaenodonts as marsupial carnivores. Borths and Seiffert (2017) did not expand their taxon list to include marsupials and thus, taxon exclusion implanted a deadly flaw in their otherwise brilliant and technical paper.

Figure 3. Arctocyon is no longer an ungulate placental, but a carnivorous marsupial, close to Thylacinus.

Figure 2. Arctocyon is no longer an ungulate placental, but a carnivorous marsupial.

Borths and Seiffert note:
“Body mass in hyaenodonts is difficult to estimate because there are no living taxa analogous to these large-headed placental carnivores with multiple carnassials.”

“The most surprising part of this study was that Masrasector and its kin are part of a massive radiation of hyaenodonts that originated in Africa.” 

“Hyaenodonts have been a little neglected as a group.”

Wikipedia reports on the history of the Creodonta:
“Creodonta” was coined by Edward Drinker Cope in 1875. Cope included the oxyaenids and the viverravid Didymictis but omitted the hyaenodontids. In 1880. he expanded the term to include MiacidaeArctocyonidaeLeptictidae (now Pseudorhyncocyonidae), OxyaenidaeAmbloctonidae and Mesonychidae.[12] Cope originally placed creodonts within the Insectivora. In 1884, however, he regarded them as a basal group from which both carnivorans and insectivorans arose. Hyaenodontidae was not included among the creodonts until 1909. Over time, various groups were removed, and by 1969 it contained, as it does today, only the oxyaenids and the hyaenodontids.”

Figure 2. Masrasector nests with Borhyaena in the marsupial clade.

Figure 3. Masrasector nests with Borhyaena in the marsupial clade.

Earlier we looked at members at the base of this clade, like Amphicyon and Arctocyon (Fig. 2), giant closer descendants of Didelphis. Hyaenodonts and other creodonts are different from members of the Carnivora because they’re not placentals, something that has escaped the notice of paleontologists. Creodonts / hyaenodonts appear earlier in the fossil record because marsupials appear before placentals.

References
Borths MR, Seiffert ER 2017. Craniodental and humeral morphology of a new species of Masrasector (Teratodontinae, Hyaenodonta, Placentalia) from the late Eocene of Egypt and locomotor diversity in hyaenodonts. PLoS ONE 12(4): e0173527.
Simons EL, Gingerich PD 1974. New carnivorous mammals from the Oligocene of Egypt. Annals of the Geological Survey of Egypt. 1974; 4: 157–166.
Author interview online here.
Pasttime.org podcast interview here.

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Juehuaornis traced and reconstructed from lo-rez data

Figure 1. Juehuaornis in situ with tracing

Figure 1. Juehuaornis in situ with tracing

Juehuaornis zhangi (Wang et al. 2015) is a new ornithuromorph genus from the Early Cretaceous of western Liaoning, China.

Figure 2. Juehuaornis reconstructed. Note the scale bars. This is a tiny bird.

Figure 2. Juehuaornis reconstructed. Note the scale bars. This is a tiny bird.

From the abstract: Here we report on a new basal ornithuromorph bird, Juehuaornis zhangi gen et sp. nov.,based on a nearly complete and articulated subadult skeleton from the Lower Cretaceous Jiufotang Formation in Lingyuan of western Liaoning, China. It displays ornithomorph synapomorphies, such as a synsacrum composed of 12 sacral vertebrae, a short pygostyle , long and curved scapula, U-shaped furcula without a hypocleidum, coracoid with a developed procoracoid process and a concaved lateral margin,a keel extended along the full length of sternum, major and minor metacarpals fused proximally and distally, and proximal phalanx of digit II expanded caudally. The new specimen is distinguishable from other known ornithuromorphs by some unique features including a long rostrum for approximately 70% the total length of the skull, cranial end of upper jaw hooked, and cranial end of lower jaw straight. The new specimen provides new important morphological information regarding Ornithomorpha, and it represents a new ecotype of this group.

Figure 3. This is a very low rez image of the skull, the best I could wrangle from the original paper.

Figure 3. This is a very low rez image of the skull, the best I could wrangle from the original paper. That’s a hand over the skull. See figure 1. Not sure about the described premaxilla tip described in the paper. Requested high-rez data will replace this if it comes.

In the large reptile tree,
Juehuaornis nests with other small Early Cretaceous tobirds between Longicrusavis and higher toothed birds like Changzuiornis and Yanornis.

References
Wang R-F, Wang Y and Hu Dong-yu 2015. Discovery of a new ornithuromorph genus, Juehuaornis gen. nov. from Lower Cretaceous of western Liaoning, China. Global Geology 34(1):

Eudimorphodon skull reconstructed

Figure 1. Eudimorphodon ranzii nests at the base of all non-dimorphodontid pterosaurs. Here bones are colorized using DGS and reconstructed below in several views. I can't identify all the bones here, just the easy ones. Red spot in orbit is the rotated pterygoid with teeth. Other pterosaurs don't have such teeth, but then other pterosaurs don't have such marginal teeth either. Line art from F. Dalla Vecchia.

Figure 1. Eudimorphodon ranzii nests at the base of all non-dimorphodontid pterosaurs. Here bones are colorized using DGS and reconstructed below in several views. I can’t identify all the bones here, just the easy ones. Red spot in orbit is the rotated pterygoid with teeth. Other pterosaurs don’t have such teeth, but then other pterosaurs don’t have such marginal teeth either. Line art from F. Dalla Vecchia.

This is Eudimorphodon (Late Triassic), the basalmost of all the non-dimorphodontid pterosaurs. The in situ skull is crushed (Fig. 1), so if you want to see what it looks like in three views you take the parts and put the model back together.

Figure 4. Lateral, dorsal and cross-sectional views of Eudimorphodon ranzii. Note the overlap of the posterior ribs over the hind limbs and the very wide torso. The cross section shows the 2nd dorsal ribs and the 23rd. Note the small ischium which could only produce small eggs. A little taller and wider than we thought before. The forelimbs are pretty short relative to the torso.

Figure 2. Lateral, dorsal and cross-sectional views of Eudimorphodon ranzii. Note the overlap of the posterior ribs over the hind limbs and the very wide torso. The cross section shows the 2nd dorsal ribs and the 23rd. Note the small ischium which could only produce small eggs. A little taller and wider than we thought before. The forelimbs are pretty short relative to the torso.

Eudimorphodon-pterygoid-teeth588.jpg

Close up of Eudimorphodon jugal and pterygoid (yellow) from an old photocopy from back in the day. 

We looked at
the post-cranium of Eudimorphodon earlier here. The torso is weirdly flattened, like that of Sharovipteryx, making the entire body a wing shape.

Figure 3. Sharovipteryx reconstructed. Note the flattened torso.

Figure 3. Sharovipteryx reconstructed. Note the flattened torso.

References
Wild R 1978. Die Flugsaurier (Reptilia, Pterosauria) aus der Oberen Trias von Cene bei Bergamo, Italien. Bolletino della Societa Paleontologica Italiana 17(2): 176–256.
Zambelli R 1973. Eudimorphodon ranzii gen.nov., sp.nov. Uno Pterosauro Triassico. Rendiconti Instituto Lombardo Accademia, (rend. sc.) 107: 27-32.

wiki/Eudimorphodon

 

You heard it here first: No two Archaeopteryx look the same.

The science section
of the online British news outlet, the Guardian, reported on the 12th (Haarlem) specimen of Archaeopteryx re-named Ostromia. You can read that story online here.

From the Guardian article:
“Of the Twelve Specimens Once Known as Archaeopteryx (SPOKA), only nine continue to carry that name. At the end of the day, we can’t all be winners. But even within that group of nine specimens, no two Archaeopteryx look the same. Rauhut and colleagues report that there is significant variation in the size, shape, spacing and orientation of the teeth, as well as differences in body size between the different specimens. This could be an ontogenetic pattern, with larger individuals representing adults with more developed dentition. Alternatively, as the Solnhofen Basin constituted a tropical island archipelago during the Late Jurassic, these differences in body size and dentition could be interpreted as island adaptations. Similarly to today’s Galápagos finches, different populations of Archaeopteryx may have adapted to different insular environments.”

We looked at
Solnhofen birds (Fig. 1) earlier here and Ostromia here. Since 2015 readers have known that no two Archaeopteryx specimens were identical and that phylogenetic analysis split them apart to nest at the base of each one of all the Cretaceous bird clades. And yes, we know of an embryo archaeopterygid, the Liaoning embryo most closely related to the London specimen.

Figure 3. Several Solnhofen birds, including Archaeopteryx, compared to Ostromia to scale.

Figure 3. Several Solnhofen birds, including Archaeopteryx, compared to Ostromia to scale.

It really is time to
run these birds through analysis and either affirm, modify or invalidate the results of the large reptile tree. And it should be done by someone with firsthand access to all the specimens. That would be a good test.

References
Elzanowski, A., 2002. Archaeopterygidae (Upper Jurassic of Germany) In: Chiappe LM, Witmer LM, eds. Mesozoic Birds. Above the Heads of Dinosaurs. Berkeley: University of California Press. 129-159.
Foth C, Rauhut OWM. 2017. Re-evaluation of the Haarlem Archaeopteryx and the radiation of maniraptoran theropod dinosaurs. BMC Evolutionary Biology 17:236

https://www.theguardian.com/science/2018/feb/21/the-new-specimen-forcing-a-radical-rethink-of-archaeopteryx

Redefining what makes a dinosaur

Ran across this online article (citation below)
summarized: “The once-lengthy list of “definitely a dinosaur” features had already been dwindling over the past few decades thanks to new discoveries of close dino relatives such as Teleocrater. With an April 2017 report of Teleocrater’s skull depression (SN Online: 4/17/17), yet another feature was knocked off the list.”

Evidently the only trait that is still on the list is a perforated acetabulum.

My résponse:
long time readers will recognize this answer:

The dear departed Dr. Larry Martin used to play this game. He’d say ‘tell me a character you think defines a clade and I’ll give you an exception.’ In dinosaur pelves, ankylosaurs are the exception that do not have a perforated acetabulum. The lesson: You can’t define a clade by a single or a dozen character traits. 

You can define a clade using a cladogram. A cladogram uses hundreds of traits to recover relationships including “the last common ancestors and all of its descendants.” On that basis Dinosauria include Herrerasaurus at the base and the first dichotomy splits Theropoda from Phytodinosauria. The proximal outgroup is the Crocodylomorpha, basal members of which were small and bipedal, like early dinosaurs. That means Archosauria includes only dinos and crocs. Teleocrater is in the lineage of stem Archosauria. Unfortunately, prior workers excluded many relevant taxa, which is why they did not recover these relationships. Cladogram, links and more data here: 
The last few items on the dinosaur list:
  1. Until Teleocrater came along, only dinosaurs were known to have a deep depression at the top of the skull, an attachment site for some jaw muscles probably related to bite strength.
  2.  Dinosaurs and some other dinosauromorphs such as Silesaurus opolensis have an enlarged crest on the upper arm bone where muscles attached
  3. Along with dinosaurs, dinosauromorphs S. opolensis and Asilisaurus kongwe may have had epipophyses, bony projections at the back of the neck vertebrae.
  4. An extra (fourth) muscle attachment site, called a trochanter, at the point on the femur that meets the hip is also found in dinosauromorph Marasuchus lilloensis.

Sources: S.J. Nesbitt et al/Nature 2017; S.L. Brusatte et al/Earth-Science Reviews 2010

Taxon exclusion. Phylogenetic analysis. Yada-yada. 

References
https://www.sciencenews.org/article/new-fossils-are-redefining-what-makes-dinosaur

Nesbitt et al. 2017 The earliest bird-line archosaurs and the assemblof the dinosaur body plan. Nature (Teleocrater paper).

When turtles lost their teeth

When animals lose something,
be it a tail, finger, limbs, eyes or teeth, usually a vestige is left behind.

When turtles lost their ancestral teeth,
they should have left empty alveoli along their jaw rims. And the place to look for empty alveoli in turtles is in the most primitive turtle in the large reptile tree, the late-surviving Niolamia (Fig. 1), one of the great horned meiolaniid turtles.

Figure 1. Palate of the basal turtle Niolamia with arrows pointing to pinprick alveoli lacking teeth.

Figure 1. Palate of the basal turtle Niolamia with arrows pointing to pinprick alveoli lacking teeth.

Tiny pinpricks
along the maxilla (Fig. 1) seem to show where tiny teeth once erupted in Niolamia.

Earlier we looked at similar alveoli in the jaw tips of a gray whale where desmostylian tusks once emerged.

Helpless and able newborn mammals

I’m going to crowd source this one,
but I think I covered all the bases here. In this subset of the large reptile tree (LRT, 1165 taxa) I’ve divided placental mammals born helpless (blue) from mammals born able to walk, swim and see (pink). I’ll need your help if there are any exceptions, like pangolins, that I missed one way or the other. Fossils are colorized based on phylogenetic bracketing.

Figure 1. Newborn mammals are born either helpless, like humans, or able to keep up with their mother, like horses. I think I located the split correctly here. Let me know I missed a few.

Figure 1. Newborn mammals are born either helpless, like humans, or able to keep up with their mother, like horses. I think I located the split correctly here. Let me know I missed a few. Fossil taxa are colored based on phylogenetic bracketing. 

Marine taxa need to be ready to go from the first minute.
Apparently so do the large plant-eaters ( including ant and copepod eaters), beginning with long-legged former tree shrew, Onychodectes.

Dens and nests
are associated with basal mammals, like us. Not so much with the derived herbivores (and anteaters) of the plains and forests. All of them get milk from their mothers before they start to dine on meat, plants, ants and copepods. Some of them have to keep up with here. Some of them have to keep up with her underwater.

BTW
there also seems to be a behavioral node at Maelestes in which succeeding taxa are all leaving the trees for good. Of course, that also happens exceptionally with the various mole and aquatic clades in more basal mammals.