Allkaruen koi was overlooked as a proto-Pterodaustro

A new pterosaur described by Codorniú et al. 2016
somehow escaped my notice until today. Allkaruen koi (Figs. 1,3,4) is the new genus. It was originally nested between basal (long-tailed) pterosaurs and the Darwinopterus clade + ‘Pterodactyloidea’ using an antiquated cladogram modified from Lü e al 2010, itself modified from Unwin 2003. We’re going to critically examine this paper, applying logic, creating reconstructions, calling on overlooked data and including more than a few previously excluded taxa.

Figure 1. Allkaruen elements as originally published. Some of the scale bars are different by 94% and 117%, resized to the same scale below in figure 3. Why couldn’t they all be drawn to the same scale, and in relation to one another? You’ll see how well that works in figure 3.

The holotype of Allkaruen koi includes:

1. MPEF-PV 3613 (Museo Paleontológico Egidio Feruglio)  braincase,
2. MPEF-PV 3609 mandible
3. MPEF-PV 3615 cervical vertebrae (Fig. 1)

The stratigraphic horizon
in which Allkaruen was found was labeled by Codorniú et al.: “latest Early-early Middle Jurassic.” Let’s just call it “Middle Jurassic.”

From the Codorniú et al. abstract
“Here we report on a new Jurassic pterosaur from Argentina, Allkaruen koi gen. et sp. nov., remains of which include a superbly preserved, uncrushed braincase that sheds light on the origins of the highly derived neuroanatomy of pterodactyloids and their close relatives. A mCT ray-generated virtual endocast shows that the new pterosaur exhibits a mosaic of plesiomorphic and derived traits of the inner ear and neuroanatomy that fills an important gap between those of non-monofenestratan breviquartossans (Rhamphorhynchidae) and derived pterodactyloids.”

The diagnosis:
“Small pterosaur diagnosed by the following unique combination of skull characters present in the holotype (autapomorphies marked with asterisk):

1. frontal with large pneumatic foramen on the postorbital process
2. dorsal occiput faces posterodorsally and occipital condyle faces posteroventrally
3. long, rod-like basipterygoid processes diverging at approximately 20–25 degrees.

The referred mandibular and vertebral materials also show a unique combination of characters that include:

1. a long lower jaw with a concave profile in lateral view
2. four-five large, septated, and well-separated anterior alveoli followed by a posterior alveolar groove*;
3. mid-cervical vertebrae elongate with low neural arch and blade-like neural spine; pneumatic foramina on lateral surface of the centrum and peduncle of the neural arch
4. reduced diapophyseal process lacking articular surface
5. absence of accessory zygapophyseal processes.”

Figure 2. Codornií cladoram nesting Allkaruen between basal pterosaurs and derived pterosaurs. Note that a dinosaur is the outgroup here. There are 59 taxa above. Note the close relationship of Dorygnathus and Allkaruen and Pterodaustro in this cladogram. It gets even closer in figure 6.

The Codorniú et al. phylogenetic analysis
Codorniú et al. added Allkaruen to the cladogram of Lü et al 2003 (the Darwinopterus study) based on Unwin 2003. They recovered Allkaruen basal to their ‘Monofenestrata‘, which was basal to their ‘Pterodactyloidea’. Both clades were found to be invalid in the large pterosaur tree.

Figure 3. Reconstruction of Allkaruen atop a more complete Pterodaustro to the same scale demonstrating a close match-up of elements that was somehow overlooked by the original authors. The amount of material missing between the mandibles and the cranium is unknown. See figure 4 for a closer look at the cranium. Note the tooth grooves and anterior alveoli in the top view of the dentary.

A reconstruction
missing from the original paper, but provided here (Fig. 3) provides an overlooked answer to the affinities of Allkaruen. This Middle Jurassic taxon closely matches Albian (latest Early Cretaceous) Pterodaustro, the only other South American pterosaur with a dorsally concave dentary (#1), an alveolar groove (#2), similar mid-cervical vertebrae (#3) and maybe traits #4 and #5, (hard to tell from the available data). The dorsal appearance of the cranium of Allkaruen also closely matches that of another ctenochasmatid, Gnathosaurus. Most to all Pterodaustro specimens are preserved in lateral view, so the dorsal appearance must be gained from closely related taxa. like Gnathosaurus, by phylogenetic bracketing.

Figure 4. Closeup of the cranium and brain scan of Allkaruen atop a ghosted to scale image of Pterodaustro to scale demonstrating a close affinity that was somehow overlooked originally with that short taxon list.

Pterodaustro is distinct from other ctenochasmatids
in that it has typical tetrapod vertically oriented mandibles, rather than flattened (wider than tall) mandibles typical of other ctenochasmatids (Fig. 7). In addition Pterodaustro has upwardly curved jaw tips, a trait documented in Allkaruen, in which we can see the transition from a toothy dentary to one with grooves to accommodate the hundreds of needle-like filter teeth found in Pterodaustro. Not sure why, but this similarity was overlooked by Codorniü et al. It’s doubly puzzling because Dr. Codorniú has published extensively on Pterodaustro. The only time Pterodaustro was mentioned by Codorniú et al. was when they wrote, “The cavities that invade the basicranium are also large, equivalent to those observed in pterodactyloids such as Pterodaustro.”

Figure 5. Chronological evolution of Pterodaustro via Allkaruen, Angustinaripterus (Early Jurassic) and Dorygnathus (late survivor in the Middle Jurassic).

The pterosaur phylogeny presented
by the large pterosaur tree (LPT, subset Fig. 5) provides a fast track evolution from derived dorygnathids, already demonstrating a wide radiation in the Early Jurassic, to ctenochasmatids like Allkaruen (Middle Jurassic) and Ctenochasma (Late Jurassic) that does not include the Darwinopterus clade as transitional taxa. In the LPT four clades evolved a complete set of pterodactyloid-grade traits. Two other clades, Anurognathidae and Wukongipteridae, independently evolved an incomplete set of pterodactyloid-grade traits. These led to invalid claims by Andres, Clark and Xu 2014 that anurognathids were basal to pterodactyloids and Unwin 2003 + Lü et al. 2010 that wukongopterids were basal to pterodactyloids. These claims were made with short, incomplete taxon inclusion lists that were shown to be lacking in pertinent taxa by the LPT.

Fig. 6. Subset of the argePT focusing on Dorygnathus clades that evolved to become ctenochasmatids and azhdarchids. This is what you get when don’t exclude taxa the way Codorniú did.

It’s no surprise that Allkaruen has transitional traits.
In the LPT it represents a transitional stage in the evolution of Pterodaustro from Angustinaripterus ancestors. Allkaruen nests with Pterodaustro in the LPT, but due to the headless D2514 ‘not Eosipterus‘ specimen adding Allkaruen creates a polytomy (Fig. 6). As earlier, no claim of ‘mosaic evolution‘ can be made by Codorniú et al. ‘Mosaic evolution’ has not been shown to exist in large gamut cladograms. Such claims by Codorniú et al. and others are the result of small cladograms grossly lacking in pertinent taxa.

Figure 7. A selection of valid Ctenochasma skulls together with the two interpretations of Sos 2179 (in gray below). Note the phylogenetic miniaturization following Angustinaripterus.

Professional bias among paleontologists
and a refusal to test competing hypotheses of relationships (Peters 2000, 2007) led to the phylogenetic disaster presented by Codorniú et al. 2016. No one will ever be convinced that pterosaurs arose from Euparkeria + Herrerasaurus. Workers who do so open themselves up to ridicule. We don’t want that. It makes us all look bad. Adding taxa should solve the phylogenetic problems found in Codorniú et al. The LRT and LPT offer suggestions, but workers must put forth the effort. In Peters 2000 Cosesaurus, Sharovipteryerx and Longisquama were documented to demonstrate closer relationships to pterosaurs than dinosaurs and archosaurs can offer.

Was Allkaruen transitional between basal pterosaurs and pterodactyloids?
No. There is no valid monophlietic clade of pterodactyloids. At present, the best we can say is: Middle Jurassic Allkaruen is (time wise) transitional between Early Jurassic Angustinaripterus and Early Cretaceous Pterodaustro (Fig. 5). Allkaruen is a ctenochasmatid, plain and simple. It points to an earlier radiation of ctenochasmatids than the Solnhofen Late Jurassic. The cranial elements of Allkaruen might someday be matched to post-cranial elements now represented by the lower Yixian D2514 specimen wrongly attributed (by Lü et al. 2006) to Eosipterus. Or not. A complete specimen (crania + post-crania) would settle this  issue.

I can’t be the first pterosaur worker to notice
the Allkaruen/Pterodaustro connection. If others preceded me, please let me know so I can congratulate and confirm them.

Everyone, including Codorniu et al., is looking for
that one transitional taxon, that ‘missing link’ between long-tailed pterosaurs and short-tailed pterosaurs. Andres, Clark and Xu 2014 failed when they mistook small parts of a skinny dorygnathid for a much smaller pterodactyloid. Lü et al. 2010 failed when they added Darwinopterus to a small gamut cladogram. Codorniú et al. failed when they promoted Allkaruen to that position. The authority to state that these PhDs failed comes from a large gamut cladogram, the LPT, that tests their short taxon lists with a much larger taxon list. The LPT documents four appearances of pterodactyloid-grade clades and so will competing studies when they expand their lists, create reconstructions and have a third party certify their scores are correct.

Ironically, no one’s looking for
that one transitional taxon, that ‘missing link’ between pre-volant pterosaur ancestors and basal pterosaurs. Do you wonder why that is? I can only suppose no one wants to confirm the published work of an amateur from 17 years ago (Peters 2000). There’s no reward in it for PhDs. No one wants to admit they were wrong and needlessly parochial for 17 years.

References
Andres, B, Clark J and Xu X 2014. The Earliest Pterodactyloid and the Origin of the Group. Current Biology. 24: 1011–6.
Codorniú L, Carabajal AP, Pol D, Unwin D and Rauhut OWM 2016. A Jurassic pterosaur from Patagonia. and the origin of the pterodactyloid neurocranium. PeerJ 4:e2311; DOI 10.7717/peerj.2311
Lü J-C, Gao C-L, Meng Q-J, Liu J-Y, Ji Q 2006. On the Systematic Position of Eosipterus yangi Ji et Ji, 1997 among Pterodactyloids. Acta Geologicia Sinica 80(5):643-646.
Lü J, Unwin D, Jin X, Liu Y, Ji Q 2010. Evidence for modular evolution in a long-tailed pterosaur with a pterodactyloid skull. Proceeding of the Royal Society B 273:383389.
Peters D 2000. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2007. The origin and radiation of the Pterosauria. Flugsaurier. The Wellnhofer Pterosaur Meeting, Munich 27.
Unwin DM 2003. On the phylogeny and evolutionary history of pterosaurs. In:Buffetaut E, Mazin J-M, eds. Evolution and Paleobiology of Pterosaurs, vol. 217. London: Geological Society, Special Publications, 139190.

wiki/Allkaruen

First African pterosaur trackway (manus only)

FIgure 1. From Masrour et al. 2017, manus only pterosaur tracks. They are BIG! Again I will note, only lepidosaurs can bend their lateral metacarpophalangeal joints within the palmar plane at right angles to the others, producing posteriorly oriented manual digit 3.

Masour et al. 2017
bring us new manus only Late Cretaceous azhdarchid tracks. They report, “The site contains only manus tracks, which can be explained as a result of erosion of pes prints.” They assume that the pterosaur fingers pressed deeper, carrying more weight on the forelimbs. Of course, this is a bogus explanation. No tetrapods do this. Pterosaurs put LESS weight on their tiny fragile fingers. They used their hands like skiers used ski poles.

FIgure 2. From Masrour et al. 2017, model of the trackmaker of the manus only tracks erroneously attributed to Bennett 1997, who drew Pterodactylus, not this generalized azhdarchid.

There is another explanation for manus only tracks
called floating and poling, but that hypothesis was dismissed by the authors.

Masrour et al. dismiss the possibility of floating
by referencing Hone and Henderston 2014 in which simulations of the buoyancy of poorly constructed pterosaurs made using computers indicate that these reptiles had no ability to float well in water. This hypothesis was dismantled earlier here. In addition, Hone’s track record is not good. Neither is Henderson’s, who does not seem to care about using accurate skeletal reconstructions.

More importantly,
if Hone and Henderson put forth an anti-floating hypothesis no one (and certainly no scientist) should simply believe in it. This is Science. Others, like Masrour et al., should TEST hypotheses for validity, as was done here. Instead Masrour et al. put forth a hypothesis in which pes tracks were selectively erased over time, which seems preposterous and unnatural. This sort of selective erasure has never been observed in Nature.

Figure 3. The azhdarchid pterosaur Quetzalcoatlus floating and poling producing manus only tracks. Remember the skull is as light as a paper sculpture.

Scientists fail
when they blindly follow bad hypotheses, just because they are published. Nodding journalists repeat what they read, whether right or wrong. Scientists test whenever they can.

Figure 4. Tapejara poling while floating, producing manus-only tracks, all to scale. Remember the skull is as light as a paper sculpture.

Don’t believe in Henderson cartoons
(Fig. 5). Test with accurate representatives of skeletons IFig. 4).

Figure 5. Computational models of two pterosaurs from Hone and Henderson 2013/2014. Note how both have trouble keeping their nose out of the water. Henderson’s models have shown their limitations in earlier papers.

When you don’t use cartoons for data
then you have a much better chance of figuring out how Nature did things.

Figure 6. Two configurations for Rhamphorhynchus. Because the wings act like pontoons, the torso and skull can be rotated relative to the wings to adopt a variety of floating configurations. Also note the large webbed feet, preserved in the darkling specimen. The tail can be elevated at its base.

Thank you for your continuing interest.
After over 2000 blog posts the origin of bats continues to be the number one blog post visited week after week, with totals equalling the sum of the next five topics of interest. That’s where the curiosity of the public is right now.

References
Hone DWE, Henderson DM 2014. The posture of floating pterosaurs: Ecological implications for inhabiting marine and freshwater habitats. Palaeogeography, Palaeoclimatology, Palaeoecology 394:89–98.
Masrour M et al. (4 other authors) 2017. Anza palaeoichnological site. Late Cretaceous. Morocco. Part I. The first African pterosaur trackway (manus only). Journal of African Earth Sciences (in press) 1–10.

 

https://pterosaurheresies.wordpress.com/2013/12/06/pterosaurs-were-unlikely-floaters-hone-and-henderson-2013/

Why T-rex had tiny forelimbs

quaShort answer:
T-rex (Figs. 1, 2) forelimbs were former wings, not former grasping, predatory tools. Kiwi wings (Fig. 3), which have claw tips, are good analogs. Tyrannosaurus forelimbs were relatively smaller and likewise useless. Taxon exclusion is once again the reason why this has not been able to be documented before. 

What others say:
Science Daily – “The tiny arms on the otherwise mighty Tyrannosaurus rex are one of the biggest and most enduring mysteries in paleontology.”

Thoughco.com – “T. Rex males mainly used their arms and hands to grab onto females during mating (females still possessed these limbs, of course, presumably using them for the other purposes listed below).  T. Rex used its arms to lever itself off the ground if it happened to be knocked off its feet during battle,  T. Rex used its arms to clutch tightly onto squirming prey before it delivered a killer bite with its jaws. they were exactly as big as they needed to be. This fearsome dinosaur would quickly have gone extinct if it didn’t have any arms at all.”

Popularmechanics.com – “The simple truth is that scientists aren’t sure exactly why T. rex’s arms are so short, but there’s a number of possible explanations. Perhaps the most likely is that the dino’s arms just weren’t very useful.”

FieldMuseum.org – “One of the big mysteries about T. rex is its tiny forelimbs,” says Pete Makovicky, Associate Curator of Dinosaurs. “We don’t know how it used them. But there could be clues in the fossils. When a bone is used a lot, the wear and tear cause tiny fractures that heal over time. With the right tools, we can see microscopic changes in the bones caused by that healing process. You also see things like a wider bone marrow cavity. When we remove SUE’s arm, we’re going to take it to the Argonne National Laboratory to try to look for these characteristics that will tell us how much it was used.”

Chicago Tribune
story here. Great images of a rising T-rex cyber model here from Kent Stevens, U of Oregon. Another set of images here from TyrannosaurTuesday.blogspot.com.

The answer, as usual here, comes from phylogenetic analysis.
Distinct from prior tyrannosaur studies, the large reptile tree (LRT, 1040 taxa) recovers the feathered, winged theropod, Zhenyuanlong (Fig. 1). as the proximal ancestor to the tyrannosaur clade. Theropods with large feathered wings don’t use them to grasp prey or mates.

Figure 1. Distinct from prior studies, Ornitholestes, Tianyuraptor and Zhenyuanlong are close relatives of Tyrannosaurus rex in the large reptile tree. Here Zhenyuanlong preserves long feathers on its forelimbs.

No other studies
found large feather wings on tyrannosaur ancestors. And as long as they don’t, they’ll keep thinking T-rex forelimbs were primitive grasping organs.

Figure 2. Taxa in the Compsognathus/Tyrannosaurus clade, a subset of the large reptile tree to scale. Also included are Microraptor, Sinornithosaurus, Dilong and Zhenyuanlong.

The kiwi forelimb is a good T-rex forelimb analog
The kiwi (Fig. 2) has vestigial forelimbs that are essentially useless. Even so, they were relatively much large than T-rex forelimbs. Kiwis have no trouble getting up, mating or anything else tyrannosaurs are supposed to do with their forelimbs.

Figure 3. Kiwi skeleton GIF animation (2 frames) showing the vestigial and useless forelimb tipped with a claw, an analog to the vestigial forelimb of T-rex.

A recent lecture
by Tyrannosaur Chronicles author Dr. David Hone, available here on YouTube, noted two traits common to all tyrannosaurs: fused nasals and D-shaped (in cross-section) premaxillary teeth. Zhenyuanlong does not have these traits. Thus the Hone traits have not been validated by the LRT. Instead those traits appear to have a wider distribution by convergence, like the arctometatarsals we looked at earlier.

Figure 6. Tyrannosaurus forelimb compared to Gorgosaurus. Note the larger coracoid in T-rex. It might have been resting on it.

Remember
we never want to put all our trust in just one or two traits (see above). Otherwise we’d be pulling a Larry Martin, famous for arguing phylogeny based on one or two traits alone. Instead we’re always looking for a suite of traits based on a character list of at least 150. The LRT has 228 multi-state characters and it continues to lump and separate all of its 1040 included taxa successfully, while documenting gradual accumulations of derived states.

In the present ancestry of tyrannosaurs other traits emerge.
Among the 228 traits, the LRT found several dozen shared by T-rex and Zhenyuanlong, including the elevated orbit, the hourglass-shaped quadratojugal, the pubic boot and a very short dorsal vertebral series. Noteworthy, all of these traits, other than the hourglass-shaped quadratojugal are also found elsewhere in the LRT by convergence. Don’t forget, we’re looking for the most parsimony in a suite of traits. Otherwise Pinnipedia and Cetacea would still be valid clades.

Essentially,
T-rex is just a giant, flightless Zhenyuanlong. No longer small enough to fly, the feathered flapping organs of T-rex became smaller due to lack of use. Blame it on the genes that those useless forelimbs keep appearing. We’ve also seen vestigial traits in pterosaurs (manual digit 5, ungual 4, pedal digit 5 in derived taxa), snake precursors (legs) and in baleen whales (tooth buds in embryos).

Postscript
Within 24 hours of this post T. Kaye alerted me to Giffin 1995 who wrote: “the data suggest that the brachial plexus, and therefore the cervical/dorsal vertebral transition, of the theropod dinosaurs studied was located considerably posterior to its presently accepted location, and that the forelimbs of the giant carnosaurs Tyrannosaurus rex and Carnotaurus sastrei were of biologically insignificant use.”

References

Giffin EB 1995. Postcranial paleoneurology of the Diapsida. Journal of Zoology 235(3):389-410.
Hwang SN, Norell MA, ji Q and Gao K-Q 2004. A large compsognathid from the Early Cretaceous Yixian Formation of China. Journal of Systematic Palaeontology 2(1):13-30.
Lü J and Brusatte SL 2015. A large, short-armed, winged dromaeosaurid (Dinosauria: Theropoda) from the Early Cretaceous of China and its implications for feather evolution. Scientific Reports 5, 11775; doi: 10.1038/srep11775.
Osborn HF 1905. Tyrannosaurus and other Cretaceous carnivorous dinosaurs. Bulletin of the AMNH (New York City: American Museum of Natural History) 21 (14): 259–265.

 

wiki/Tyrannosaurus
wiki/Zhenyuanlong

 

 

 

 

Seals are diphyletic. Goodbye Pinnipedia!

This split has been suspected or imagined for quite some time…
…but never documented with fossil taxa in phylogenetic analysis until today in the large reptile tree (LRT 1040 taxa; subset Fig. 1).

Figure 1. Subset of the LRT focusing on Carnivora and the diphyletic nesting of seals, derived from separate terrestrial ancestors. Moving one seal next to the others adds 14 steps.

Seals are diphyletic.
These marine Carnivora had two terrestrial origins. Phoca is an earless seal (family: Phocidae) derived from a sister to Paleaosinopa. On the other hand, Zalophus is an eared seal (family: Otariidae) derived from a sister to Hyopsodus and Miacis. Thus the clade Pinnipedia is no longer monophyletic. The last common ancestor of seals in the LRT is the extant common raccoon, Procyon.  Doubtless a similar form that lived closer to the Cretaceous was the actual last common ancestor. Both clades of seals (that’s what we’ll still call them forever) adapted to water in similar, but not identical ways (see below).

Figure 1. Phoca the phocid seal is most closely related to Palaeosinopa of all tested taxa.

Molecular evidence
According to Wikipedia: “While seals were historically thought to have descended from two ancestral lines, molecular evidence supports them as a monophyleticlineage (descended from one ancestral line). Pinnipeds belong to the order Carnivora and their closest living relatives are bears and musteloids (weasels, raccoons, skunks, and red pandas), having diverged about 50 million years ago.”  Of course, if the sister taxa that split seals are extinct (fossil taxa) as they are here, then molecular studies cannot service this issue or answer this question.

Figure 3. Zalophus, an otariid seal, is most closely related to Hyopsodus among tested taxa in the LRT

Earlier hypotheses
imagined otariids descended from bears and phocids descended from mustelids (weasels). Below are some of those earlier, mostly molecular studies and their intrinsic problems.

1. Arnason et al. 2006. Molecular study. Outgroups include bears, minks other Carnivora and no fossil taxa.
2. Flynn et al. 2005. Molecular study of the Carnivora. Outgroups include no fossil taxa.
3. Higdon et al. 2007. Molecular study of the Pinnipedia. Outgroups include bears and dogs and no fossil taxa.
4. Hunt and Barnes 1994. Skull base comparisons link seals to bears, not otters and ferrets.
5. Lento GM et al. 1995. Molecular study found pinnipeds derived from the bear/raccoon/panda radiation. Outgroups include no fossil taxa.
6. Sato JJ, et al. 2006. Molecular study allies pinnipeds with otters and ferrets. Outgroups include no fossil taxa.

Issues: Palaeosinopa
was considered a non-Eutherian placental mammal. Here it nests within Carnivora without a priori assumptions clouding the selection of the inclusion group.

Figure 4. Palaeosinopa, complete and largely articulated. Body length about 50 cm. Tail adds 35 cm. From Rose and Koenigswald 2005. This taxon nests with Phoca in the LRT.

Issues: Hyopsodus
was considered an odd-toed ungulate that was swift and lived in burrows. Here it nests within Carnivora without a priori assumptions clouding the selection of the inclusion group.

Figure 5. Hyopsodus as originally reconstructed (below) and as reconstructed here above in two views. This former condylarth now nests with dogs.

What about Enaliarctos?
Found in Late Oligocene strata, this earliest otariid (Fig. 6; Mitchell and Tedford 1973) nests between Zalophus and Hyopsodus in the LRT.

Figure 6. Enaliarctos nests between Zalophus and Hyopsodus in the LRT. The long bone around the knees is a baculum, or penis bone, found only in males.

What about Puijula?
Pujilia darwini (Rybczynski, Dawson and Tedford 2009; Late Oligocene 23 mya;1m in length) was originally considered an extinct species of seal based chiefly on skull and tooth traits. Here in the LRT it nests at the base of the clade that produced phocid seals, not otarid seals. It was derived from a sister to Mustela the river otter and lived in and near high Arctic lakes.

Figure 6. Pujilia was considered a basalmost pinniped, but here nests at the base on only the phocids, not the otarids.

Differences
According to Wikipedia: “Otariids use their front limbs primarily to propel themselves through the water, while phocids and walruses use their hind limbs. Otariids and walruses have hind limbs that can be pulled under the body and used as legs on land. By comparison, terrestrial locomotion by phocids is more cumbersome. Otariids have visible external ears, while phocids and walruses lack these.”

By the way,
moving one seal next to the other in the LRT adds 14 steps.

You might remember
the LRT for all of its faults (the list grows shorter every day) was able to similarly separate toothed whales (Odontoceti) from baleen whales (Mysticeti) and document they each had separate terrestrial ancestors, tenrecs and desmostylians respectively. Given the overall similarity of Otariids to Phocids, their separation in the LRT is another demonstration of the acuity and authority of large gamut phylogenetic analyses.

By the way, since this is science…
this is something anyone can do. Repeat the experiment if you have doubts, and let me know what you get. Apparently earlier workers were excluding pertinent outgroup taxa from their analyses, and this is something we’ve seen over and over again. That’s what set the stage for ReptileEvolution.com and this blog.

References
Arnason U, et al. (6 other authors) 2006. Pinniped phylogeny and a new hypothesis for their origin and dispersal. Molecular Phylogenetics and Evolution. 41 (2): 345–54.
Flynn JJ, Finarelli JA, Zehr S, Hsu J and Nedbal MA 2005. Molecular phylogeny of the Carnivora (Mammalia): Assessing the impact of increased sampling on resolving enigmatic relationships. Systematic Biology. 54 (2): 317–37.
Higdon JW, Bininda-Emonds OR, Beck RM and Ferguson SH 2007. Phylogeny and divergence of the pinnipeds (Carnivora: Mammalia) assessed using a multigene dataset. BMC Evolutionary Biology. 7: 216.
Hunt RM Jr and Barnes LG 1994. Basicranial evidence for ursid affinity of the oldest pinnipeds. Proceedings of the San Diego Society of Natural History. 29: 57–67.
Lento GM, Hickson RE, Chambers GK and Penny D 1995. Use of spectral analysis to test hypotheses on the origin of pinnipeds. Molecular Biology and Evolution. 12(1): 28–52.
Mitchell E and Tedford RH 1973. The enaliarctinae a new group of extinct aquatic carnivora and a consideration of the origin of the otariidae. Bulletin of the American Museum of Natural History 151:284 pp.
Orlov YA 1933. Semantor macrurus (ordo Pinnipedia, Fam. Semantoridae Fam. nova) aus den Neogen-Ablagerungen Westsibiriens. Trudy Paleontologicheskii Institut Akademiia Nauk SSSR 2, 249-253.
Rybczynski N, Dawson MR. and Tedford RH 2009. A semi-aquatic Arctic mammalian carnivore from the Miocene epoch and origin of Pinnipedia. Nature 458, 1021–1024.
Sato JJ, et al. (7 other authors) 2006. Evidence from nuclear DNA sequences sheds light on the phylogenetic relationships of Pinnipedia: Single origin with affinity to Musteloidea. Zoological Science. 23 (2): 125–46.

wiki/Pinniped
wiki/Enaliarctos
wiki/Phoca
wiki/Zalophus
wiki/Hyopsodus
wiki/Palaeosinopa

/tetrapod-zoology/pinnipeds-descended-from-one-ancestral-line-not-two/

Figuring out the upside-down skull of Yanoconodon

Figure 1. Yanoconodon fossil in situ. See the skull in closeup in figure 2. The published tracing is distorted here to match the underlying photo.

Wikipedia reports, “Yanoconodon was a small mammal, barely 5 inches (13 centimetres) long. It had a sprawling posture, Yanoconodon was a Eutriconodont, a group composing most taxa once classified as “triconodonts” which lived during the time of the dinosaurs. These were a highly ecologically diverse group, including large sized taxa such as Repenomamus that were able to eat small dinosaurs, the arboreal Jeholodens, the aerial volaticotherines and the spined Spinolestes. Yanoconodon is inferred to be a generalized terrestrial mammal, capable of multiple forms of locomotion.

Figure 2. Yanoconodon is exposed in ventral view. Even so, if you employ DGS, even on a fuzzy photo, you can put together a reconstruction that shares several traits with Repenomamus.

Mammal-like reptiles?
Wikipedia also reports, “The Yanoconodon holotype is so well preserved that scientists were able to examine tiny bones of the middle ear. These are of particular interest because of their “transitional” state: Yanoconodon has fundamentally modern middle ear bones, but these are still attached to the jaw by an ossified Meckel’s cartilage. This is a feature retained from earlier stem mammals, and illustrates the transition from a basal tetrapod jaw and ear, to a mammalian one in which the middle ear bones are fully separate from the jaw. Despite this feature Yanoconodon is a true mammal. It is thought that the feature was retained during early embryo development,^[4] whereas it is lost in most other mammal groups. The intermediate anatomy of the middle ear of Yanocodon is said to be a “Rosetta Stone”^[5] of mammalian middle ear evolution.”

In the large reptile tree (LRT, 1037 taxa) Yanoconodon, Repenomamus, Jeholodens and Spinolestes are not mammals, but very close to the base of the Mammalia. Both clades share Pachygenelus as last common ancestor. So that means the ‘transitional state’ mentioned above is indeed outside the Mammalia. Other paleontologists consider this list of taxa to be mammals, but here the mammal-like traits they had were developed in parallel and not quite to mammal standards.

Figure 4. Repenomamus reconstructed using DGS methods. The manus and feet are loose figments at present. Despite its predatory nature, note the reduction in canines, a clade trait.

The skull of Yanoconodon
(Fig. 2) can be largely, but not completely, reconstructed based on the visible bones. The skull is low and wide and without the typical constriction anterior to the jugals. The anterior teeth are large and spike-like while the posterior teeth are molariform. Large teeth typically require deep roots and deep bones to house those roots. The mandibles are as long as the skull. The small orbits are far forward on the skull and the temporal fenestra are correspondingly large.

Figure 2. The origin and radiation of stem mammals and crown mammals. Compare the LRT tree (above) to a recent cladogram by Close et al. 2015.

With the new data on Yanocondon
several taxa within the LRT shifted places, but not far and still within the derived Cynodontia. Something about the Mammalia helped them survive several extinction events that the derived Tritylodontia (= Pseudomammalia) succumbed to. Pseudomammalia LOOK like mammals, but are not mammals. They continued to exist into the Early Cretaceous and some, like Repenomamus, were quite large.

References
Close RA, Friedman M, Lloyd GT and Benson RBJ 2015. Evidence for a mid-Jurassic adaptive radiation in mammals. Current Biology. 25(16): 2137–2142. 
Luo Z, Chen P, Li G, and Chen M 2007. A new eutriconodont mammal and evolutionary development in early mammals. Nature 446:15. online Nature

wiki/Yanoconodon

Macrocnemus skull in DGS

This started with
a fuzzy photo of a  complete fossil Macrocnemus specimen, PMR T2472 (Fig 1).

Figure 1. GIF animation of PMR T2472, a large Macrocnemus in situ and reconstructed from a fuzzy photo.

Many specimens attributed to Macrocnemus
are known, each one a little different phylogenetically. Reports of a ‘juvenile’ Macrocnemus refer to the phylogenetically basalmost and smallest of the known specimens, the one closest to its outgroup taxon, the tritosaur lepidosaur, Huehuecuetzpalli.

It’s good to remind yourself
before reading the reference titles, that Macrocnemus and kin are not protorosaurs (= prolacertiforms), nor are they archosauriforms. Even I made the same mistake (Peters 2000b) in my more naive days before the LRT recovered Macrocnemus and kin as tritosaur lepidosaurs in Peters 2007.

From this rather ordinary taxon arises 
such diverse and exotic taxa as Dinocephalosaurus, Sharovipteryx, a variety of Tanystropheus, several Langobardisaurus, Longisquama and pterosaurs. Peters 2007 reported, “The basal lizard, Huehuecuetzpalli is the most primitive taxon in this newly revealed third squamate clade between Iguania and Scleroglossa. Two branches arise from it. Jesairosaurus is basal to the Drepanosauridae. Three distinct specimens of Macrocnemus give rise to the Tanystropheidae,the Langobardisaurinae and to the Fenestrasauria respectively.” Jesairosaurus and Drepanosauridae are now basal lepidosauriformes.

References
Li C, Zhao L-J and Wang L-T 2007. A new species of Macrocnemus (Reptilia: Protorosauria) from the Middle Triassic of southwestern China and its palaeogeographical implication. Science in China D, Earth Sciences 50(11)1601-1605.
Li C, Wu X-C, Zhao L-J, Nesbitt SJ, Stocker MR, Wang L-T 2016. A new armored archosauriform (Diapsida: Archosauromorpha) from the marine Middle Triassic of China, with implications for the diverse life styles of archosauriforms prior to the diversification of Archosauria. The Science of Nature 103: 95. doi:10.1007/s00114-016-1418-4
Nopcsa F 1931. Macrocnemus nicht Macrochemus. Centralblatt fur Mineralogie. Geologic und Palaeontologie; Stuttgart. 1931 Abt B 655–656.
Peters D 2000b. A Redescription of Four Prolacertiform Genera and Implications for Pterosaur Phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106 (3): 293–336.
Peters D 2007. The origin and radiation of the Pterosauria. In D. Hone ed. Flugsaurier. The Wellnhofer pterosaur meeting, 2007, Munich, Germany. p. 27.
Peyer B 1937. Die Triasfauna der Tessiner Kalkalpen XII. Macrocnemus bassanii Nopcsa. Abhandlung der Schweizerische Palaontologische Geologischen Gesellschaft pp. 1-140.
Renesto S and Avanzini M 2002. Skin remains in a juvenile Macrocnemus bassanii Nopsca (Reptilia, Prolacertiformes) from the Middle Triassic of Northern Italy. Jahrbuch Geologie und Paläontologie, Abhandlung 224(1):31-48.
Romer AS 1970. Unorthodoxies in Reptilian Phylogeny. Evolution 25:103-112.

wiki/Macrocnemus

 

Pterodactylus manual digit 5

Tiny, vestigial manual digit 5
sits on the top of the giant axially rotated metacarpal 4 of all pterosaurs. Here (Fig. 1) manual digit 5 is curled up on this Pterodactylus scolopaciceps specimen (BSP 1937 I 18), a pregnant pterosaur. Photoshop helps this digit ‘pop’ making it harder to overlook. A reconstruction unrolls it.

Figure 1. Manual digit 5 on top of the giant metatarsal 4 on Pterodactylus. It’s easy to overlook, until you look for it.

References
Broili F 1938. Beobachtungen an Pterodactylus. Sitz-Bayerischen Akademie der Wissenschaten, zu München, Mathematischen-naturalischenAbteilung: 139–154.
Wellnhofer P 1970. Die Pterodactyloidea (Pterosauria) der Oberjura-Plattenkalke Süddeutschlands. Abhandlungen der Bayerischen Akademie der Wissenschaften, N.F., Munich 141: 1-133.

wiki/Pterodactylus