You heard it here first: Chilesaurus is a basal ornithischian confirmed.

Figure 1. Chilesaurus and kin, including Damonosaurus and basal phytodinosauria.

Figure 1. Chilesaurus and kin, including Damonosaurus and basal phytodinosauria.

Figure 2. Look familiar? Here are the pelves of Jeholosaurus and Chilesaurus compared. As discussed earlier, this is how the ornithischian pelvis evolved from that of Eoraptor and basal saurorpodomorpha.

Figure 2. Look familiar? Here are the pelves of Jeholosaurus and Chilesaurus compared. As discussed earlier, this is how the ornithischian pelvis evolved from that of Eoraptor and basal saurorpodomorpha.

A new paper by Baron and Barrett 2017 confirms Chilesaurus (Fig. 1) as a basal member of the Ornithischia, not a bizarre theropod. As long time readers know, this was put online two years ago (other links below) in this blog.

Unfortunately, the authors don’t have an understanding of the interrelationships of phytodinosaurs, even though they report, For example, Chilesauruspossesses features that appear ‘classically’ theropod-like, sauropodomorph-like and ornithischian-like…” Nor did they mention the sister taxon, Jeholosaurus (Fig. 2).

Remember,
discovery only happens once.
More on this topic later.

This note went out this morning:
Thank you, Matthew,
for the confirmation on Chilesaurus.
In this case, it would have been appropriate to include me as a co-author since I put this online two years ago.

https://pterosaurheresies.wordpress.com/2015/04/28/chilesaurus-new-dinosaur-not-so-enigmatic-after-all/
http://www.reptileevolution.com/reptile-tree.htm
http://www.reptileevolution.com/chilesaurus.htm

References
Baron MG, Barrett PM 2017. A dinosaur missing-link? Chilesaurus and the early evolution of ornithischian dinosaurs. Biol. Lett. 13: 20170220. http://dx.doi.org/10.1098/rsbl.2017.0220 pdf online

Best regards,

What is Fruitafossor? A xenarthran close to Peltephilus.

This appears to be
yet another case of pertinent taxon exclusion. Today’s fossorial digger has several universally acknowledged xenarthran (edentate) traits. For reasons unknown it was not tested against another fossorial xenarthran, Peltephilus. Rather the authors compared their digger to an arboreal sloth, Bradypus, among several other taxa, including distinctly different anteaters and armadillos.

Figure 1. Scapula of Fruitafossor compared to several candidate sisters. Luo and Wible made things a bit more difficult by presenting left and right scapulae. Here they are all left scapulae for ready comparison. There is no doubt that the Fruitafossor scapula looks more like that of Ornithorhynchus.

ºªº Figure 1. Scapula of Fruitafossor compared to several candidate sisters. Luo and Wible made things a bit more difficult by presenting left and right scapulae. In frame 2 they are all left scapulae for ready comparison. There is no doubt that the Fruitafossor scapula was illustrated to look more like that of Ornithorhynchus. Unfortunately the photo data (Fig. 2) does not clearly support that shape. That shape is so important, it needed to be better documented.

Luo and Wible 2005
brought us a small, mostly articulated, rather crushed and incomplete Late Jurassic mammal with simple blunt teeth and digging forelimbs. Fruitafossor windscheffeli (Figs. 1–6) is best represented by a CT scan (Figs. 2–4) and original drawings (Figs. 5, 6) created by the Luo and Wible team.

Figure 2. Fruitafossor in situ from Digimorph.org and used with permission and here colorized to an uncertain extent.

Figure 2. Fruitafossor in situ from Digimorph.org and used with permission and here colorized to an uncertain extent. All those little white dots could be scattered osteoderms.

The original analysis
nested Fruitafossor between extremely tiny Hadrocodium + Shuotherium and Gobiconodon in a tree topology that does not resemble the topology of the large reptile tree (LRT, 1048 taxa). The authors noted Fruitafossor is “not a eutherian, let alone a xenarthran” despite noting Fruitafossor had tubular molars and xenarthran intervertebral articulations, traits otherwise found only in xenarthrans.

Figure 2. Same specimen from Digimorph.org and rotated to show the teeth better. See figure 3 for a closeup.

Figure 3. Same specimen from Digimorph.org and rotated to show the teeth better. See figure 3 for a closeup. All those little white dots could be scattered osteoderms. Some of this flatness is due to crushing. Some of it is due to this being a wider than deep armored mammal.

Wider than deep
Yes, the Fruitafossor specimen is crushed, but what is shown here indicates a low, wide mammal just getting some armor in the Late Jurassic. And we all know why armor might have been helpful! And this may explain the lateral sprawl of the forelimbs and giant wide humerus, another atavism!

Figure 3. Closeup of figure 2 showing maxilla and dentary in occlusion.

Figure 4. Closeup of figure 2 showing maxilla and dentary in occlusion. If there is a convex ventral dentary it must be imagined because it is not preserved.

By contrast,
the LRT nested Fruitafossor with the horned, armored digging ‘armadillo’ more closely related to BradypusPeltephilus (Fig. 5).

Figure 4. The xenarthran, Peltephilus, compared to Fruitafossor, not to scale, but to similar jaw lengths. Note the drawing from Zhou and Wible does not exactly match what one can see in the photo (Fig. 3). This data needs to be clear and it is not.

Figure 5. The xenarthran, Peltephilus, compared to Fruitafossor, not to scale, but to similar jaw lengths. Note the drawing from Luo and Wible does not exactly match what one can see in the photo (Fig. 3). This data needs to be clear and it is not.

Luo and Wible compared
Fruitafossor to the arboreal and extant Bradypus, but not to the fossorial and extinct Peltephilius (Fig. 5). I would consider that a mistake or an oversight that here overturns their hypothesis of a relationship of Fruitafossor to basalmost mammals.

Figure 5. Several drawings from Zhou and Wible that one must trust for accuracy. The verification data is too fuzzy to validate.

Figure 6. Several drawings from Luo and Wible that one must trust for accuracy. The verification data is too fuzzy to validate. As in other xenarthrans, the ilia actually form a pair of horizontal plates on either side of the long fused and eroded sacrals. Four fingers is a trait shared with Peltephilus. Imagine that rib cage wider and not so deep.

Scattered osteoderms
(Fig. 3) were not mentioned in the text. That’s one more trait shared with the armored xenarthran, Peltephilus. This overlooked relationship of derived xenarthrans moves them into the Jurassic, an era they have never been in before in phylogenetic and chronological analyses. Here placental arboreal and fossorial mammals (prior to condylarths) shared time and space with dinosaurs during the Jurassic and Cretaceous, but have, so far, been underrepresented in the fossil record. That’s changing with re-examination of the data applied to a larger gamut taxon list.

Although the illustrated scapula
(Fig. 1) looks like that of an egg-laying mammal, I will wait for better data to validate that illustration. In the meantime, Fruitafossor has blunt, tubular molars and xenarthran vertebral articulations (among many other xenarthran traits) because it is a xenarthran, not an egg-layer with convergent traits.

References
Luo Z-X and Wible JR 2005. A late Jurassic digging mammal and early mammal diversification. Science 308:103–107.

Goodbye Scrotifera. Goodbye Euarchontaglires. Goodbye Scandentia. etc. etc.

Earlier the large reptile tree
found that several former clades, like Parareptilia, PterodactyloideaCetacea, Testudinata (Chelonia) Notoungulata, Pseudosuchia, Ornithodira and Pinnipedia were not monophyletic… and that list keeps growing.

The large reptile tree (LRT, 1044 taxa) does not replicate the following mammalian clades:

  1. Scandentia – tree shrews: yes, closely related, but at the bases of different clades.
  2. Euarchontaglires – rodents, rabbits, tree shrews, flying lemurs and primates,  (Fig. 1)
  3. Euarchonta – tree shrews, flying lemurs, primates and plesiadapiformes.
  4. Glires – rodents, rabbits
  5. Scrotifera – Eulipotyphla (see below), bats, pangolins, Carnivora, Euungulata (including whales)
  6. Eulipotyphla – hedgehogs, shrews, solenodons, moles (moles are Carnivora))
  7. Euungulata – perissodactyls, artiodactyls (including whales)
  8. Tenrecidae – tenrecs, some are closer to shrews, others closer to odontocetes
  9. Macroscelidea – elephant shrews, some are closer to tenrecs
  10. Primates – Plesiadapiformes and extant primates, including Daubentonia (the aye-aye. No giant anterior dentary teeth in valid primates.
  11. there are a few more I’m overlooking. I’ll add them as they come to me.
Figure 1. Glires and Euarchonta are two clades within the Mammalia in the LRT.

Figure 1. Glires and Euarchonta are two clades within the Mammalia in the LRT.

Let’s focus on Plesiadapiformes
Bloch et al. 2007 found plesiadapiforms (Plesiadapis, Carpolestes and kin) more closely related to primates than to any other group. They did not test against rodents and multituberculates. The LRT does not replicate these results, but finds plesiadapiforms more closely related to multituberculates and rodents when included.

According to Bloch & Boyer 2002
“Plesiadapiforms share some traits with living primates, including long fingers well designed for grasping, and other features of the skeleton that are related to arboreality.” That’s fine, but there are other taxa in the tree topology with long fingers, too.

Paromomyidae
Krause 1991 reports, “Paromomyids …have long been regarded by most workers as members of the Plesiadapiformes.” Again, the LRT does not support this, but nests Paromomyids, like Ignacius (Fig. 2), with rodents, like Mus and Paramys. Paromomyids have squared off and flat molars, but Paromomys does not.

Figure 2. The skull of Ignacius nests with other rodents, not plesiadapiformes.

Figure 2. The skull of Ignacius nests with other rodents, not plesiadapiformes. Ironically it is closer to the squirrel-like Paramys than to Paromomys.

Beard 1990 thought paromomyids,
as plesiadapiforms, where close to colugos or “flying lemurs”. The LRT (Fig. 1) does not support this relationship. Rather paromomyids, like Ignacius, were squirrel-like, able to scamper both in the trees and on the ground. Ignacius graybullianus (USNM 421608, Fig. 1) is a new taxon that nests as a basal rodent in the LRT.

Figure 3. Ignacius clarkforkensis known parts.

Figure 3. Ignacius clarkforkensis known parts.

Remmber, no primates 
have giant anterior dentary teeth. The aye-aye, Daubentonia, has such teeth, but the LRT finds it nests with Plesiadapis and multituberculates and rodents, not primates. Yes, plesiadapiformes and Ignacius had long limbs, big brains and binocular vision, but by convergence with primates.

References
Beard KC 1990. 
Gliding Behavior and palaeoecology of the alleged primate family Paromomyidae (Mammalia, Dermoptera). Nature 345, 340-341.
Bloch J, Silcox MT, et al. 2007.
New Paleocene skeletons and the relationship of plesiadapiforms to crown-clade primates.  Proceedings of the National Academy of Science 104, 1159-1164.
Kay RF, Thewissen JG and Yoder, AD 1992. Cranial anatomy of Ignacius graybullianus and the affinities of the Plesiadapiformes. American Journal of Physical Anthropology. 89 (4): 477–498. doi:10.1002/ajpa.1330890409.
Krause DW 1984. Mammal Evolution in the Paleocene: Beginning of an Era. In: Gingerich, P. D. & Badgley, C. E. (eds.): Mammals: notes for a short course. Univ. of Tennessee, Department of Geological Sciences.
Krause DW 1991. Were paromomyids gliders? Maybe, maybe not. Journal of human evolution 21:177-188.

Turtles with wings

Figure 1. Manus of Carettochelys, the pig-nosed turtle, resembles the wing of other tetrapods.

Figure 1. Manus of Carettochelys, Note the crest posterior to the shoulder joint.

Yes, underwater wings.
We’re talking today about the pig-nosed turtle, Carettochelys insculpta (Figs. 1-3), which became interesting when Brinkman, Rabi and Zhao 2017 nested it basal to soft-shell turtles. The large reptile tree (LRT, 1043 taxa, subset Fig. 3) does not replicate those results. Rather the LRT nests Carettochelys with Foxemys.

Carettochelys insculpta (Ramsay 1886; 70 cm) is the extant pig-nosed turtle. Unlike any other species of freshwater turtle, the feet are flippers, like the marine sea turtle Chelonia. The carapace is not scaly, but leathery. It remains domed and the solid plastron is strongly connectedd to the carapace. Brinkman, Rabi and Zhao 2017 nested Carettochelysbasal to soft shell turtles, but the large reptile tree nests it with Foxemys. Like Trionyx, the nose extends slighly from the skull.

FIgure 1. Carettochelys, the pig-nose turtle, is a freshwater form with flippers, like marine turtles, by convergence.

FIgure 2. Carettochelys, the pig-nose turtle, is a freshwater form with flippers, like marine turtles, by convergence. The nose is tubular like soft shell turtles.

Not sure why
Brinkman, Rabi and Zhao 2017 nest Carettochelys with soft shell turtles, but I suspect it has to do with taxon exclusion (a limited gamut of tested taxa) and an improper traditional inclusion.

Figure 3. Carettochelys in 3 views from Digimorph.org and used with permission.

Figure 3. Carettochelys in 3 views from Digimorph.org and used with permission.

The skull of Carettochelys
includes large and extensive postorbital fenestrae. The jugal is quite tiny. The squamosal (blue) and quadratojugal (beige) are fused, as in sister taxa. The supratemporal (orange) has been traditionally mislabeled as a squamosal.

Figure 4. The skull of Carettochelys in 5 views. This skull shares some traits with Trionyx, but more with Foxemys.

Figure 4. The skull of Carettochelys in 5 views. This skull shares some traits with Trionyx, but more with Foxemys.

As an experiment
I deleted all taxa other than turtles (Fig. 5) and decided that Proganochelys would be the outgroup to match the analyses of other workers. Even so, soft shell turtles do not nest with Carettochelys. 

Figure 2. Subset of the LRT composed on only turtles and with Proganochelys as the outgroup.

Figure 5. Subset of the LRT composed on only turtles and with Proganochelys as the outgroup.

A subset of the LRT
(Fig. 6) shows the relationship of soft shell and hard (dome) shell turtles to pareiasaurs. Note: turtles are not monophyletic, unless you also include the pareiasaurs Bunostegos and Arganaceras, which I do here to document the clade of crown turtles. The LRT includes enough characters to separate soft shell turtles from others, despite a long list of similar traits. That should give one great confidence that the character list is sufficient at its present number.

FIgure 3. Subset of the LRT including turtles and their kin.

FIgure 6. Subset of the LRT including turtles and their kin. Pleurodires are side-neck turtles.

Marine turtles with flippers (underwater wings)
include Dermochelys, the extant leatherback turtle (Fig. 7), convergent with Carettochelys. The LRT includes enough traits to separate these two similar yet distinct taxa.

Figure 2. Dermochelys skeleton, ventral view. In vivo (upper left) and open mouth (lower right).

Figure 7. Dermochelys skeleton, ventral view. In vivo (upper left) and open mouth (lower right).

References
Brinkman D, Rabi M and Zhao L-J 2017. Lower Cretaceous fossils from China shed light on the ancestral body plan of crown soft-shell turtles (Trionychidae, Cryptodira). Nature Scientific Reports 7(6719).
Ramsay EP 1886. On a new genus and species of fresh water tortoise from the Fly River, New Guinea. Proceedings of the Linnaean Society of New South Wales (2) 1: 158-162.

wiki/Pig-nosed_turtle
http://digimorph.org/specimens/Carettochelys_insculpta/

Another DNA analysis fails to replicate LRT analysis

Earlier we talked about the failure of DNA studies to replicate or confirm morphological studies in phylogenetic analysis. A few days ago Shaffer et al. 2017 discussed turtle origins using DNA, trying to figure out when turtles diverged from archosaurs (birds + crocs) and when cryptodires diverged from pleurodires.

Figure 1. From Schaeffer et al. a graphic showing the divergence times for cryptodires and pleurodires according to their studies of molecules and morphology.

Figure 1. From Schaeffer et al. a graphic showing the divergence times for cryptodires and pleurodires according to their studies of molecules and morphology. Some titles were added for clarity. 

From the Shaffer et al. abstract
“We used our genomic data to estimate the ages of living turtle clades including a mid-late Triassic origin for crown turtles and a mid-Carboniferous split of turtles from their sister group, Archosauria. By specifically excluding several of the earliest potential crown turtle fossils and limiting the age of fossil calibration points to the unambiguous crown lineage Caribemys oxfordiensis from the Late Jurassic (Oxfordian, 163.5–157.3 Ma) we corroborate a relatively ancient age for living turtles. We also provide novel age estimates for five of the ten testudine families containing more than a single species, as well as several intrafamilial clades. Most of the diversity of crown turtles appears to date to the Paleogene, well after the Cretaceous-Paleogene mass extinction 66 mya.
By contrast 
In the large reptile tree (LRT 1042 taxa) the divergence date between soft-shell turtles (like Odontochelys) and hard-shelled domed turtles (like Meiolania or perhaps Elginia) dates back probably to, but at least to the Late Permian with Elginia. Without valid outgroups, like Elginia and Sclerosaurus, there is no way Schaeffer et al. are going to get the base of their turtle tree right. And the dominoes fall from there.
The “mid-Carboniferous split” reported by Shaffer et al. between Archosauria and turtles is more or less supported by the LRT In that analysis the Viséan (Early Carboniferous) is when we have evidence that the Lepidosauromorpha (including turtle ancestors) and Archosauromorpha (including archosaur ancestors) had split apart from its last common ancestor, Gephyrostegus at the base of the Reptilia.
But let’s be clear,
turtles are in no way related to archosaurs, except at the very base of the Reptilia.
The journal title:
‘Molecular Phylogenetics and Evolution’
 (see below) is fast becoming an oxymoron and an invalidated science except when taxa are closely related to one another. Someone please mention this to the editors. Long phylogenetic distances constantly fail to produce DNA trees that match morphology trees, as everyone acknowledges, but no one else is ready to accept at present.

References
Shaffer HB, McCartney-Melstad E, Near TJ, Mount GG and Spinks PQ 2017. Phylogenomic analyses of 539 highly informative loci dates a fully resolved time tree for the major clades of living turtles (Testudines). Molecular Phylogenetics and Evolution 115: 7–15. doi: https://doi.org/10.1016/j.ympev.2017.07.006

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.

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.

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 Hyoposodus among tested taxa in the LRT

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 1. Palaeosinopa, complete and largely articulated. Body length about 50 cm. Tail adds 35 cm. From Rose and Koenigswald 2005.

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

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.

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.

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/

The joy of finding mistakes: fewer stem dinosaurs

Finding mistakes is what I hope to do every day
in my own work, as well as that of others. Each time that happens, the data set improves. Lumping and splitting improves. The hypothetical topology of the large reptile tree (LRT, 1036 taxa) gets closer to echoing the topology of Nature itself. Science is a process of winnowing through the data and finding earlier mistakes.

Figure 1. Revision to the LRT with a focus on the Archosauria. Here taxa with a long carpus all nest within the Crocodylomorpha, following traditional thinking. Dinosaur outgroups are reduced. PVL 4597 is still the basalmost archosaur.

Figure 1. Revision to the LRT with a focus on the Archosauria. Here taxa with a long carpus all nest within the Crocodylomorpha, following traditional thinking. Dinosaur outgroups are reduced. PVL 4597 is still the basalmost archosaur.

Today
I discovered some scoring errors among former ‘stem dinosaurs’ that turned them into basal crocodylomorphs. That’s a small shift and it involved turning some ‘absent’ scores in pedal digit 5 to ‘unknown’. It’s noteworthy that some related taxa have two tiny phalanges on pedal digit 5. A related taxon, Gracilisuchu, was illustrated by Romer (1972, Fig. 3) as a combination or chimaera of separate specimens, something I just today realized and rescored. One of those specimens is the so-called Tucuman specimen (PVL 4597, Fig 1), which nests apart from the Gracilisuchus holotype (Fig. 2) in the LRT.

Figure 1. The PVL 4597 specimen attributed to Gracilisuchus by Lecuona et al. 2017, but nesting at the base of the Dinosauria in the LRT.

Figure 2. The PVL 4597 specimen attributed to Gracilisuchus by Lecuona et al. 2017, but nesting at the base of the Dinosauria in the LRT. That fibula flange turns out to be another important trait. 

The corrected results
resolve the long proximal carpal issue in crocodylomorphs very neatly. Now, as in traditional thinking, that trait is restricted to only the crocodylomorphs and it gives us a basalmost taxon with the trait, Junggarsuchus. You might think, and it would be reasonable to do so, that phylogenetic bracketing permitted the addition of a long carpus and long coracoids with more confidence to taxa that don’t preserve this, like Gracilisuchus and Saltopus. But another related basal crocodylomorph, Scleromochlus, has small round coracoids, evidently a reversal. The carpal length is not clearly documented in Scleromochlus (Fig. 4).

Gracilisuchus

Figure 3. A basal archosaur with a very similar nasal bone, Gracilisuchus. Note pedal digit 5 here. This is how Romer 1972 illustrated it. The actual data is shown in figure 2, the Tucuman specimen, PVL 4597. The coracoid is not known in the holotype. 

Despite the short round coracoids of Scleromochlu
and its apparently short carpals, enough traits remain to nest it as a basal crocodylomorph, following the rules of maximum parsimony.

Figure 1. Scleromochlus forequarters. The yellow area shows the hand enlarged in situ. The size of the Scleromochlus hand makes it the last possible sister to pterosaurs, famous for their very large hands.

Figure 4. Scleromochlus forequarters. The yellow area shows the hand enlarged in situ. Large carpals do not appear to be present and the coracoids are not elongated. 

On a more personal note
I found out my art and a short bio were included in a paleoart website:
http://paleoartistry.webs.com while looking for information on friend and paleoartist, Mark Hallett, (wikipage here) whose website is down and I worried about his health. No worries. Mark just let his website lapse.

The author of the paleoartistry page
had both kind words and controversy for me:
“After David Peters’ excellent paintings in Giants, and A Gallery of Dinosaurs and Other Early Reptiles, as well as his own calendar, it seemed he was on his way to becoming one of the most reliable paleoartists of the 1990s, if not of all time. However, very controversial theories on reconstructing pterosaurs led to some harsh critiques obscuring Peters’ artistic brilliance.” 

That’s okay.
“Very controversial” does not mean completely bonkers (or am I reading too little into this?). It just means it inspires a lot of chatter. Or… it could mean that the author of the post follows the invalidated observations of Elgin, Hone and Frey 2010, which are the traditional views (Unwin and Bakhurina 1994), still used in David Attenborough films. If so, that would be a shame. Science is usually black and white – is or isn’t, because you can observe and test (Fig. 5) and all tests, if done the same, should turn out the same.

And you don’t toss out data
that doesn’t agree with your preconception, like Elgin, Hone and Frey did. In reality, my “very controversial reconstructions” remain the only ones built with DGS, not freehand guesswork or crude cartoonish tracings (as in Elgin, Hone and Frey 2010). The membranes (brachiopatagia and uropatagia) were documented in precise detail in Peters 2002, 2009 and here online.

Click to animate. This is the Vienna specimen of Pterodactylus, which preserves twin uropatagia behind the knees.

Figure 5. Click to animate. This is the Vienna specimen of Pterodactylus, which preserves twin uropatagia behind the knees.

References
Elgin RA, Hone DWE and Frey E 2011. The extent of the pterosaur flight membrane. Acta Palaeontologica Polonica 56 (1), 2011: 99-111. doi: 10.4202/app.2009.0145
Peters D 2002. A New Model for the Evolution of the Pterosaur Wing – with a twist. – Historical Biology 15: 277–301.
Peters D 2009. A reinterpretation of pteroid articulation in pterosaurs. Journal of Vertebrate Paleontology 29:1327-1330.
Romer AS 1972. 
The Chañares (Argentina) Triassic reptile fauna. An early ornithosuchid pseudosuchian, Gracilisuchus stipanicicorum, gen. et sp. nov. Breviora 389:1-24.
Unwin DM and Bakhurina NN 1994. Sordes pilosus and the nature of the pterosaur flight apparatus. Nature 371: 62-64.

wiki/Gracilisuchus
paleoartistry.webs.com/1980s.htm