Outdated paleontology textbooks

Following in the wake of the fading paleo textbook I grew up with,
Vertebrate Paleontology (Carroll 1988), comes more recent editions from Professor Michael Benton (3rd edition 2005; 4th edition 2014, Fig. 1).

Figure 1. Vertebrate Paleontology by M. Benton.

Figure 1. Vertebrate Paleontology by M. Benton.

Prior reviews:
“The book is a main textbook for vertebrate palaeontology and aimed at students and anyone with an interest in the evolution of vertebrates. It meets its five aims and is excellent value.” 
(Proceedings of the Open University Geological Society, 1 April 2015)

From the Amazon.com website:
“This new edition reflects the international scope of vertebrate palaeontology, with a special focus on exciting new finds from China. A key aim is to explain the science. Gone are the days of guesswork. Young researchers use impressive new numerical and imaging methods to explore the tree of life, macroevolution, global change, and functional morphology.

“The fourth edition is completely revised. The cladistic framework is strengthened, and new functional and developmental spreads are added. Study aids include: key questions, research to be done, and recommendations of further reading and web sites.

“The book is designed for palaeontology courses in biology and geology departments. It is also aimed at enthusiasts who want to experience the flavour of how the research is done. The book is strongly phylogenetic, and this makes it a source of current data on vertebrate evolution.”

A review from the perspective of the large reptile tree
Unfortunately this volume invalidates itself by taxon exclusion at many nodes. Readers are better served at ReptileEvolution.com where taxa are included and tested, not just reported on.

Dr. Benton has been caught excluding taxa
in the past (e.g. Hone and Benton 2007, 2009Yang et al. 2018) to support his own outdated and invalidated hypotheses (like Scleromochlus, the bipedal croc with tiny hands as a sister to Bergamodactylus, the basal pterosaur with giant hands). His textbook presents several falsehoods about pterosaurs (e.g. open ventral pelvis, all were quadrupedal, origin from archosaurs). The first dichotomy splitting the Reptilia into Lepidosauromorpha and Archosauromorpha is not presented, leading to many mix-ups in derived taxa. Lacking is a wide gamut specimen-based phylogenetic analysis, like the large reptile tree, a modern requirement for every textbook on this subject in the present cladistic era. Rather, a number of smaller, more focused previously published studies are presented without review or criticism.

Finally,
because the Benton volume is a physical book, it cannot keep up with the weekly and daily additions of online competitors, like www.ReptileEvolution.com is able to do. The Benton book, and all such textbooks, start to become outdated the moment the authors submit their final drafts to the publishers, weeks or months before their publication dates. It’s just the nature of publishing. It cannot be avoided due to this time lag.

Popular books make similar mistakes
Naish and Barrett 2016 wrote a dinosaur book, “Informed by the latest scientific research.” Sadly, no. This book is a journalistic compendium of prior studies, many of which were invalidated by taxon exclusion. As in most traditional studies, bipedal crocs are ignored in their cladograms dealing with the origin of dinos. These authors also considered tiny bipedal Scleromochlus ancestral to pterosaurs + Dinosauromorpha (p. 34), following Benton 1999. This hypothesis of relationships was invalidated by Peters 2000 who simply added taxa ignored by 4 prior authors, including Benton 1999. We can also be disappointed that these PhD authors bought into the bogus Yi qi styliform reconstruction as a bat-winged bird amalgam without either a critical analysis or a second thought of this one-of-a-kind mistake. The authors also supported the debunked origin of birds from theropods of descending size (pp. 184–185). Authors and editors should have checked for logic errors like the following from Naish and Barrett: “The fact that a microraptor specimen preserves a fish in its belly, indicates that they were also spending time on the ground.”

Just let that sink in if you don’t get it right away.

Parker 2015
reports on traditional mishandlings of the evolution of reptiles considered and criticized here at ReptileEvolution.com and PterosaurHeresies. As is typical in traditional paleontology, too often sister taxa in Parker 2015 do not document a gradual accumulation of derived traits. For instance the first dichotomy in the Parker topology splits Synapsids from Sauropsids. So no amphibian-like reptiles are recognized. The next dichotomy splits Eureptilia from Anapsida / Parareptilia. So pareiasaurs nest with mesosaurs. Parker considers the origin of ichthyosaurs and turtles, “uncertain.” A wide gamut cladogram testing all possibilities has no such problem Parker splits the invalid clade Sauria into Lepidosauromorpha and Archosauromorpha, then splits Sauropterygia and Lepidosauria, then lumps Pterosauria and Dinosauria together in the invalid clade Avemetatarsalia / Ornithodira. And with Avemetatarsalia we once again return to Benton 1999, which keeps surviving like a zombie.

As others have noted,
the present day is a ‘Golden Age’ in paleontology where discoveries are being posted weekly if not daily. Paper textbooks just cannot keep up with the latest hypotheses of relationships when compared to online studies and critiques that can pop up within hours of academic publication.

Benton would not have written editions 1 and 2
unless Carroll 1988 had become obsolete. Benton would not have written editions 3 and 4 if he didn’t think the earlier editions were failing to keep with our understanding of paleontology. Given the time it takes to produce, publish and distribute giant textbooks, It may be time for textbooks to go extinct and evolve into current online information.

References
Benton MJ 2005. Vertebrate Paleontology 3rd Edition PDF online Wiley-Blackwell 455 pp.
Benton MJ 2014. Vertebrate Paleontology 4th Edition Wiley-Blackwell 480 pp.
Carroll RL 1988. Vertebrate Paleontology and Evolution. WH Freeman and Co. New York.
Hone DWE and Benton MJ 2007. An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles. Journal of Systematic Palaeontology 5:465–469.
Hone DWE and Benton MJ 2008. 
Contrasting supertree and total evidence methods: the origin of the pterosaurs. Zitteliana B28:35–60.
Naish D and Barrett P 2016. Dinosaurs. How they lived and evolved. Smithsonian Press.  online here.
Parker S (general editor) 2015. Evolution. The whole story. Firefly Books 576 pp.
Peters D 2000. A redescription of four prolacertiform genera and implications for pterosaur phylogenesis. Rivista Italiana di Paleontologia e Stratigrafia 106: 293-336

 

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Teraterpeton: more post-crania

Pritchard and Sues 2019
bring us additional post-cranial data on Teraterpeton (Fig. 1, Sues 2003), the long-snouted sister to Trilophosaurus with an atypical antorbital fenestra and displaced naris.

Figure 1. Teraterpeton with new elements added. Toes are largely unknown, but added here based on proximal phalanges.

Figure 1. Teraterpeton with new elements added. Toes are largely unknown, but added here based on proximal phalanges. None of these elements come as a surprise, based on phylogenetic bracketing in the LRT. Note the lepidosaur-like hind limbs, because this IS a lepidosaur.

Teraterpeton hrynewichorum (Sues 2003, Pritchard and Sues 2019) Late Triassic, ~215 mya, was described as euryapsid (lacking a lateral temporal fenestra) and possibly related to the rhynchocephalian, Trilophosaurus on that basis. Here Teraterpeton is a sister to Trllophosaurus, but with a stretched out rostrum, an antorbital fenestra and fewer teeth, still characteristically narrower at the root line. Teraterpeton also nests between Sapheosaurus and Mesosuchus. at the junction between the primitive sphenodontids and the advanced rhynchosaurs (see the LRT), all within the Lepidosauria. The manual unguals are robust with disparate sizes. The large acetabulum was open posteriorly and taller than the rest of the ilium. The metatarsals overlapped considerably. The asymmetry of the metatarsals is typical of sprawling taxa, like lizards.

Figure 2. Cladogram from Pritchard and Sues 2019 showing the nesting of Teraterpeton with Trilophosaurus. The yellow taxa are lepidosauromorphs and the green taxa are archosauromorphs in the LRT. Taxon exclusion folds them together like a deck of cards.

Figure 2. Cladogram from Pritchard and Sues 2019 showing the nesting of Teraterpeton with Trilophosaurus. The yellow taxa are lepidosauromorphs and the green taxa are archosauromorphs in the LRT. Taxon exclusion folds them together like a deck of cards.

The Pritchard and Sues (P+S) Teraterpeton cladogram
(Fig. 2) shuffles lepidosauromorphs (yellow) and archosaurmorphs (green) together like a deck of cards. Unfortunately the authors were following old traditional cladograms that wrongly considered Diapsida monophyletic. The large reptile tree (LRT, 1395 taxa) separates lepidosauromorphs from archosauromorphs at the first reptile dichotomy, a factor not recognized by the authors. Taxon exclusion is a problem here.

Where do we agree?

  1. Coelurosauravus and kin nest with drepanosaurs.
  2. Teraterpeton is close to Trilophosaurus, Shringisaurus and Azendohsaurus
  3. Lepidosaurs, like Huehuecuetzpalli, nest close to Rhynchocephalians
  4. Tritosaurs, like Macrocnemus, nest with Tanystropheus

Where do we disagree?

  1. The glider Coelurosauravus should nest with the gliding kuehneosaurs, not close to the aquatic Claudiosaurus.
  2. but not with unrelated basal diapsids, like Petrolacosaurus and Orovenator, which nest in the Archosauromorpha.
  3. All the protorosaurs (Prolacerta, Pamelaria, Protorosaurus, Boreopricea, Ozimek, should nest together.

Without an understanding
of the basal Lepidosauromorpha/Archosauromorpha dichotomy following the basalmost amniote, Silvanerpeton in the Viséan, taxon exclusion blurs the differences between archosauromorph-like lepidosaurs and lepidosaur-like protorosaurs, convergent with one another.

Convergence is revealed by the LRT
not by the Pritchard and Sues cladogram that suffers from taxon exclusion. Add taxa to recover the basal split between the new Archosauromorpha and the new Lepidosauromorpha.

References
Pritchard AC and Sues H-D 2019. Postcranial remains of Teraterpeton hrynewichorum
(Reptilia: Archosauromorpha) and the mosaic evolution of the saurian postcranial skeleton. Journal of Systematic Palaeontology, DOI: 10.1080/14772019.2018.1551249
Sues H-D 2003. An unusual new archosauromorph reptile from the Upper Triassic Wolfville Formation of Nova Scotia. Canadian. Journal of Earth Science 40(4): 635-649.

 

Antarctanax: a late-surviving basal synapsid, not a dino ancestor

Peecock, Smith and Sidor 2019
bring us news of a Early Triassic amniote from the Transantarctic Mountains, Antarctanax shackletoni (Figs. 1, 2), “known from a partial postcranial skeleton including cervical and dorsal vertebrae, a humerus, and both pedes.” 

Figure 1. Antarctanax manus and pes in situ with original tracing and color added here.

Figure 1. Antarctanax manus and pes in situ with original tracing and color added here.

Unfortunately,
if the scale bars are correct, and they seem to be, the smaller ‘pes’, the one surrounded by cervicals, is really a manus (Figs. 1, 2). Furthermore, the small manus matches the small humerus and radius.

Figure 2. Antarctanax manus and pes compared to those of Cabarzia and Aerosaurus, two basal synapsids.

Figure 2. Antarctanax manus and pes compared to those of Cabarzia and Aerosaurus, two basal synapsids. As you can see, basal synapsids rather quickly evolved similarly sized hands and feet. 

The authors mislabeled
the robust, displaced metatarsal 5 as metatarsal 1, which lies beneath it (colored orange, Figs. 1, 2). Perhaps a reconstruction would have helped expose this error before submission.

The authors report,
“Our inclusion of A. shackletoni in phylogenetic analyses of early amniotes finds it as an archosauriform archosauromorph.” Their cladogram based on Ezcurra et al. 2014 nested Antarctanax in an unresolved polytomy with the basal archosauriforms, Proterosuchus, Erythrosuchus and Euparkeria. Their cladogram based on Ezcurra 2016 nested Antarctanax in an unresolved polytomy with other basal archosauriforms, FugusuchusSarmatosuchus. I am not aware of a manus or pes preserved for these two taxa. Of the above listed taxa, Proterosuchus (Fig. 3) comes closest, but has a hooked metatarsal 5 and metacarpal 3 is the longest, distinct from Antarctanax.

Synaptichnium

Figure 3. Synaptichnium compared to a slightly altered pes of Proterosuchus. Note a reduction of one phalanx in pedal digit 4 to match one less pad in the ichnite. The last two (or three phalanges) of pedal 4 are unknown in Proterosuchus.

This time it is not taxon exclusion, but bad timing.
When the manus and pes of Antarctanax are added to the large reptile tree (LRT, 1395 taxa), Antarctanax nests with basalmost synapsids, like Cabarzia (Figs. 2, 4) and Aerosaurus (Fig. 2). Aerosaurus was included in Ezcurra et al. 2014 and tested by Peecock, Smith and Sidor 2019. You’ll have to ask the authors why Antarctanax did not nest closer to Aerosaurus. Cabarzia trostheidei (Spindler, Werneberg and Schneider 2019, Fig. 3) could have influenced their thinking and scoring, but it was published only a few weeks ago, too late to include in their submission.

Figure 1. Cabarzia in situ and tracing distorted to fit the photo from Spindler, et al. 2019. Inserts show manus and pes with DGS colors and reconstructions. Scale bar = 5 cm.

Figure 4. Cabarzia in situ and tracing distorted to fit the photo from Spindler, et al. 2019. Inserts show manus and pes with DGS colors and reconstructions. Scale bar = 5 cm.

Peecock, Smith and Sidor did not provide a reconstruction
of Antarctanax, but online Discover magazine provided an in vivo painting and crowned it, “Dinosaur Relative Antarctanax.” According to the LRT, Antarctanax was a late-surviving (Early Triassic) basal member of our own lineage, the Synapsida, with a late Carboniferous genesis.

Therapsid synapsids were plentiful in Antarctica in the Early Triassic.
The headline should have focused on the unexpected presence of this sprawling, pre-pelycosaur, basal synapsid in the Mesozoic, surviving the Permian extinction event in this Antarctic refuge, alongside a closer relative of mammals, Thrinaxodon.

References
Ezcurra MD, Scheyer TM and Butler RJ 2014. The origin and early evolution of Sauria: reassessing the Permian saurian fossil record and the timing of the crocodile-lizard divergence. PLoS ONE 9:e89165.
Ezcurra MD 2016. The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. PeerJ 4:e1778.
Peecock BR, Smith RMH and Sidor C 2019. A novel archosauromorph from Antarctica and an updated review of a high-latitude vertebrate assemblage in the wake of the end-Permian mass extinction. Journal of Vertebrate Paleontology e1536664 (16 pages) DOI: 10.1080/02724634.2018.1536664
Spindler F, Werneberg R and Schneider JW 2019. A new mesenosaurine from the lower Permian of Germany and the postcrania of Mesenosaurus: implications for early amniote comparative osteology. PalZ Paläontologische Gesellschaf

What is Gracilisuchus? Add more taxa to find out.

We first and last looked at Gracilisuchus (Romer 1872)
a few years ago here and here. According to a recent paper by Lecuona et al. 2017, six specimens have been attributed to Gracilisuchus (Fig. 1). However, of three tested, only two are congeneric in the large reptile tree (LRT, 1394 taxa, subset Fig. 6), where all three Gracilisuchus specimens nest at or close to the base of the Archosauria (crocs + dinos only). However, that’s not how Lecuouna et al. see it (Figs. 3–5), based on Nesbitt 2011.

Figure 1. The ancestry of Scleromochlus going back to Lewisuchus, Saltoposuchus, Terrestrisuchus, SMNS 12591 and Gracilisuchus.

Figure 1. The ancestry of Scleromochlus going back to Lewisuchus, Saltoposuchus, Terrestrisuchus, SMNS 12591 and Gracilisuchus.

Key to the present discussion
is figuring out what is and is not an archosaur.

Definition
‘Archosauria’ is defined as crocs + birds, their last common ancestor and all descendants. The archosaur taxon list in Lecuona et al. (Fig. 3) is much broader than in the LRT (Fig. 6), where the clade Archosauria is restricted to just crocs + dinos. The last common ancestor of all known archosaurs in the LRT is one of the specimens Lecuona et al. assigned to Gracilisuchus, PVL 4597 (Fig. 2.

Inappropriate taxon inclusion
Lecuona et al. mistakenly recover pterosaurs with archosaurs. That’s because Lecuona et al. do not include the tested, but ignored pterosaur sisters in the clade Fenestrasauria. Pterosaurs are lepidosaurs, as their elongate wing fingers (digit 4) tell us. All archosaurs have a relatively small finger 4 and Scleromochlus (Fig. 1), a putative pterosauromorph (according to Benton 1999, Lecuona et al. 2017, and many others), has tiny hands! So Scleromochlus is not the taxon you want to nest with pterosaurs (contra Benton 1999). Inappropriate taxon inclusion and omission makes current archosaur cladograms not only fictional, but verging on ridiculous. No one, it seems, is checking their results.

Figure 2. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.

Figure 2. The origin of dinosaurs to scale. Gray arrows show the direction of evolution. This image includes Decuriasuchus, Turfanosuchus, Gracilisuchus, Lewisuchus, Pseudhesperosuchus, Trialestes, Herrerasaurus, Tawa and Eoraptor.

The Lecuona et al. 2017 cladograms
(Figs, 3–5) suffer from taxon exclusion and inappropriate taxon inclusion.

Figure 3. This is Figure 19 from Lecuona et al. 2017. All taxa are archosaurs in the Lecuona et al. cladogram. Red taxa are not archosaurs in the LRT.

Figure 3. From Lecuona et al. 2017. Red taxa are not archosaurs in the LRT (subset figure 6).

The Lecuona et al cladogram of archosaurs
(Fig. 3) includes several taxa and clades that are not archosaurs in the LRT. Note how Lecuona et al. split pterosaurs from ornithosuchids at the base of the Archosauria. These two clades share very few traits, as everyone knows.

Figure 4. Figure 17 from Lecuona et al. 2017 with colors added to taxa that are not eu-archosauriforms in the LRT.

Figure 4. Figure 17 from Lecuona et al. 2017 listing archosauriformes from Nesbitt 2011. Colors added archosaurs (green(, pararchosauriforms (yellow), and non-archosauriformes (red).

It only gets worse for Lecuona et al.
(Fig. 4) when they add phytosaurs, nesting as the last common ancestors of pterosaurs, dinosaurs and ornithosuchids. In the LRT these four clades are not closely related to one another. One wonders how Nesbitt 2011 and Lecuona et al. 2017 were able to get their work published with such results.

Figure 5. Figure 18 from Lecuona et al. 2017 with colors and reconstructions added. Here the giant, derived CM 73373 specimen nests basal to Hesperosuchus and taxa leading to Crocodiliformes. The LRT (subset Fig. 6) does not recover this topology.

Figure 5. Figure 18 from Lecuona et al. 2017 with colors and reconstructions added. Here the giant, derived CM 73373 specimen nests basal to Hesperosuchus and taxa leading to Crocodiliformes. The LRT (subset Fig. 6) does not recover this topology and finds that bipedal locomotion developed convergently in these two taxa.

Above is the Lecuona et al. cladogram
(Fig. 5) that encouraged study of the CM 73372 specimen we looked at yesterday. In the Lecuona et al. cladogram CM 73372 and tiny Hesperosuchus are sisters. In the LRT (Fig. 6) the two are not related to one another despite their many convergent traits, including a bipedal stance and short fingers.

In the LRT
(Fig. 6) two specimens of Gracilisuchus nests with similarly sized and shaped, Saltopus and Scleromochlus. That clade was derived from similar Lewisuchus and these are sisters to the Junggarsuchus clade, which also includes bipedal Pseudhesperosuchus. Hesperosuchus nests in the middle of the Crocodylomorpha (Fig. 6), not at the base. We looked at taxon exclusion in the Crocodylomorpha recently here.

FIgure 1. Subset of the LRT focusing on the Crocodylomorpha, dorsal scutes, elongate proximal carpals, bipedality and clades.

FIgure 6. Subset of the LRT focusing on the Crocodylomorpha, dorsal scutes, elongate proximal carpals, bipedality and clades.

You’ll know a good cladogram
when enough candidate taxa are included that all sister taxa actually resemble one another, producing a gradual accumulation of derived traits. This is how evolution works, so this process should be accurately reflected in cladograms. If they don’t: add more taxa until they do.

References
Benton MJ and Clark JM 1988. Archosaur phylogeny and the relationships of the Crocodilia in MJ Benton (ed.), The Phylogeny and Classification of the Tetrapods 1: 295-338. Oxford, The Systematics Association.
Brinkman D 1981. The origin of the crocodiloid tarsi and the interrelationships of thecodontian archosaurs. Breviora 464: 1–23.
Butler RJ, Sullivan C, Ezcurra MD, Liu J, Lecuona A and Sookias RB (2014. New clade of enigmatic early archosaurs yields insights into early pseudosuchian phylogeny and
the biogeography of the archosaur radiation. BMC Evolutionary Biology 14:1-16.
Juul L 1994. The phylogeny of basal archosaurs. Palaeontographica africana 1994: 1-38.
Lecuona A and Desojo, JB 2011. Hind limb osteology of Gracilisuchus stipanicicorum (Archosauria: Pseudosuchia). Earth and Environmental Science Transactions of the Royal Society of Edinburgh 102 (2): 105–128.
Lecuona A, Desojo JB and Pol D 2017. New information on the postcranial skeleton of
Gracilisuchus stipanicicorum (Archosauria: Suchia) and reappraisal of its phylogenetic position. Zoological Journal of the Linnean Society, 2017, XX, 1–40.
Parrish JM 1993. Phylogeny of the Crocodylotarsi, with reference to archosaurian and crurotarsan monophyly. Journal of Vertebrate Paleontology 13(3):287-308.
Romer AS 1972. The Chañares (Argentina) Triassic reptile fauna. An early ornithosuchid pseudosuchian, Gracilisuchus stipanicicorum, gen. et sp. nov. Breviora 389:1-24.

wiki/Gracilisuchus

CM 73372 reconstructed

So far as I know,
Carnegie Museum specimen CM 73372 (Fig. 1) does not yet have a name, nor has it been reconstructed. Weinbaum 2013 included this skull-less image in a Postosuchus study, which makes sense at first sight, given the size, proportions and age (Late Triassic) of both specimens. The large reptile tree (LRT, 1394 taxa) nests CM73372 close to Postosuchus, but closer to Teratosaurus and Smok. Since Teratosaurus is known from skull-only data at present, there is loss of resolution at that node.

Figure 1. CM73372 in situ and reconstructed using DGS methodology. At first glance it seems to be a biped with short fingers, like Postosuchus. In situ image from Weinbaum 2013.

Figure 1. CM73372 in situ and reconstructed using DGS methodology. At first glance it seems to be a biped with short fingers, like Postosuchus. In situ image from Weinbaum 2013.

This is an interesting taxon because
Lucuona et al. 2017 and others nest it basal to Crocodylomorpha. Weinbaum considered it a member of the Archosauria and the Paracrocodylomorpha, a clade the large reptile tree (LRT, 1394 taxa) does not recover.

According to Wikipedia
Loricata was an early name for an order that includes crocodilesalligators, and gharials, although the order is now referred to as Crocodylia. Nesbitt 2011 defined it as the most inclusive clade containing Crocodylus niloticus (the Nile crocodile), but not the extinct Poposaurus gracilisOrnithosuchus longidens, or Aetosaurus ferox. In the LRT, that clade is a junior synonym for Crocodylomorpha, since Poposaurus is a member of the proximal outgroup, the Poposauria. In traditional paleontology Loricata includes Rauisuchia and Crocodylomorpha. If so, then it also includes Poposauria and Dinosauria, but that was not the original intention of this definition.

Paracrocodylomorpha is another clade invalidated by the LRT because it includes Poposauria and Loricata. In the LRT Rauisuchia is the basal clade, followed roughly by Poposauria and Archosauria (crocs + dinos only).

You might recall,
the Nesbitt 2011 cladogram finds phytosaurs arising from a sister to the distinctly different Euparkeria. Taxon exclusion is the problem here. Nesbitt 2011 also finds Ornithosuchia (Ornithosuchus and kin) and Pterosauria forming the first dichotomy arising from a basal sister to Phytosauria. Again taxon exclusion is the problem here, yet widely accepted in the paleo community for reasons unknown (except, possibly ease of use and fear of change). We talked about other odd and topsy-turvy sister taxa recovered by Nesbitt 2011 earlier here, here and here, three blog posts in a nine-part series.

This addition of CM73372 to the LRT sets us up
for tomorrow’s discussion on basal archosaurs.

References
Lecuona A, Desojo JB and Pol D 2017. New information on the postcranial skeleton of Gracilisuchus stipanicicorum (Archosauria: Suchia) and reappraisal of its phylogenetic position. Zoological Journal of the Linnean Society, 2017, XX, 1–40.
Weinbaum J 2013. Postcranial skeleton of Postosuchus kirkpatricki (Archosauria:
Paracrocodylomorpha), from the Upper Triassic of the United States. Geological Society London Special Publications · August 2013.

wiki/Paracrocodylomorpha
wiki/Loricata

Hauffiosaurus: convergent with later plesiosaurs

Two misfit plesiosaurs nest together in the LRT
Earlier we looked at AnningsauraVincent and Benson (2012) reported, “In general morphology, NHMUK OR49202 does not resemble any known plesiosaurian taxon.”

Figure 2. The sisters of Anningsaura, Simosaurus and Pistosaurus.

Figure 1. The sisters of Anningsaura, Simosaurus and Pistosaurus. Until today, these provided the only clues as to the post-crania of Anningsaura, of which only the first eight cervicals are known.

Anningasaura 
(originally Plesiosaurus macrocephalus, Lydekker 1889; NHMUK OR49202) represents a completely ‘new’ branch of the plesiosauria in which the orbits virtually cannot be seen in dorsal view and the jugals bend down posteriorly to produce an angled temporal arch (Fig. 1). Moreover the premaxillae were thought to not contact the frontals and the nasals were absent. Benson et al. (2012) created a phylogenetic analysis that nested Anningsasaura at the base of the pliosaur/plesiosaur split with Bobosaurus as the outgroup.

Figure 1. Hauffiosaurus from Vincent 2011 with colors and reconstructions added.

Figure 2. Hauffiosaurus from Vincent 2011 with colors and reconstructions added.

Hauffiosaurus zanoni 
(O’Keefe 2001; Vincent 2011; Early Jurassic; 3.4m long; uncatalogued Hauff museum) is another plesiosaur that, according to Vincent 2011, “does not resemble any known plesiosaurian taxon.” This genus was considered a basal pliosauroid. Here (Fig. 3) the large reptile tree (LRT, 1392 taxa) nests between Anningsaura and Pistosaurus. Benson et al 2012 nested Hauffiosaurus one or two nodes apart from Anningsaura. No taxa in those nodes is currently in the LRT. So the LRT is a close match!

As you might imagine,
the characters in the LRT are not the same as those found in Benson et al. 2012, yet the tree topologies, so much as they can be compared, are nearly identical. This was done without first-hand access to the fossils. So, this methodology works.

Figure 3. Subset of the LRT. Here the clade Eosauropterygia nests Anningsaura with Hauffiosaurus.

Figure 3. Subset of the LRT. Here the clade Eosauropterygia nests Anningsaura with Hauffiosaurus. This nesting demonstrates an early convergence with later pliosaurids.

The skull of Hauffiosaurus is exposed in palatal view
(Fig. 4) and as such gives clear data on the often hidden palatal elements. Overlooked by Vincent 2011, the premaxilla extends to the internal naris, as in other taxa (Fig. 5), like Pliosaurus, also an overlooked connection.

Figure 3. Hauffiosaurus skull in palatal view from Vincent 2011, colors added. Overlooked by Vincent, the premaxilla (yellow) contacts the internal naris

Figure 4. Hauffiosaurus skull in palatal view from Vincent 2011, colors added. Overlooked by Vincent, the premaxilla (yellow) contacts the internal naris

DGS is able to document traits
overlooked by those with first-hand access to the fossils themselves (Figs. 4, 5).

Figure 4. Pliosaurus kevani palate, from Benson et al. 2013, also has an overlooked premaxilla-internal naris contact.

Figure 5. Pliosaurus kevani palate, from Benson et al. 2013, also has an overlooked premaxilla-internal naris contact. Red ellipses encircle the internal nares, probably too small for respiration.

References
Benson RBJ, Evans M, Druckenmiller PS 2012. Lalueza-Fox, Carles. ed. ”High Diversity, Low Disparity and Small Body Size in Plesiosaurs (Reptilia, Sauropterygia) from the Triassic–Jurassic Boundary”. PLoS ONE 7 (3): e31838. doi:10.1371/journal.pone.0031838
Benson RBJ, et al. (6 co-authors) 2013. A giant pliosaurid skull from the Late Jurassic of England. PLoS ONE 8(5): e65989. doi:10.1371/journal.pone.0065989
Dalla Vecchia FM 2006. A new sauropterygian reptile with plesiosaurian affinity from the Late Triassic of Italy. Rivista Italiana di Paleontologia e Stratigrafia 112 (2): 207–225.
O’Keefe RF 2001. A cladistic analysis and taxonomic revision of the Plesiosauria (Reptilia: Sauropterygia). Acta Zoologica Fennica 213:1–63.
Vincent P 2011. A re-examination of Hauffiosaurus zanoni, a pliosauroid from the Toarcian (Early Jurassic) of Germany. Journal of Vertebrate Paleontology 31(2): 340–351.
Vincent P and Benson RBJ 2012. Anningasaura, a basal plesiosaurian (Reptilia, Plesiosauria) from the Lower Jurassic of Lyme Regis, United Kingdom, Journal of Vertebrate Paleontology, 32:5, 1049-1063.

wiki/Anningasaura
wiki/Hauffiosaurus

 

Surprising results in a taxon exclusion test

Sometimes competing cladograms don’t match up.
They employ their own taxon lists, their own character lists and their own scores. Bias is intrinsic and unavoidable in character lists, identifying traits and setting scores. Bias only enters taxon lists whenever pertinent taxa are intentionally or accidentally omitted.

Theoretically every _identical_ taxon list
should recover an identical cladogram, no matter the character list (presuming accurate scoring). Practically that doesn’t often happen.

Previously
we looked at various tests for taxon exclusion here, here and here based on intentionally cutting taxa from the large reptile tree (LRT, 1391 taxa).

Taxon exclusion is the only variable
in the following taxon exclusion tests (Fig. 1: 4 frames, 5 seconds each) because all include the same characters and the same scores:

  1. Subset of the LRT without deletion
  2. Same subset of the LRT with unused taxa deleted
  3. Smaller subset with Reptilia deleted
  4. Even smaller subset with Reptilia and Lepospondylia deleted
Figure 1. 4-frame GIF animation showing results for taxon exclusion. If you don't want to read the taxa, just watch the colored clades as they bounce around.

Figure 1. 4-frame GIF animation, 5 seconds each, showing results for taxon exclusion. If you don’t want to read the taxa, just watch the colored clades as they bounce around.

Differences arise
in these four tree topologies (Fig. 1), and that surprised me, at first.

Then I continued testing
and realized (as everyone knows already) every included taxon influences every other included taxon. The surprise is just how far that influence extends.

The software takes it on faith
that the first listed taxon is the basal taxon.

After that the software figures out
the most parsimonious order for the rest of the taxa.

These results show the effect of distant unseen taxa
upon the taxa shown in the ‘subset without deletion’ cladogram.

This is also a good test for weaknesses within any cladogram.
Strongly nested taxa appear not to shift.

So which cladogram is most correct?
The cladogram with the most included taxa recovers the most accurate cladogram. That one is 14 steps shorter than the same cladogram with all unseen taxa deleted.

Wherever weaknesses and topology shifting occurs
look for scoring errors. I’ve been finding them and fixing them for seven years. I’m going to keep looking for scores in basal tetrapods to either cement or correct the above tree topology. As always, the LRT is a work in progress.


Short notes after adding and reexamining more basal tetrapods:

  1. Viséan Silvanerpeton is now the last common ancestor of all reptiles, switching places with Gephyrostegus, which shares more traits with the more primitive Eucritta and Tulerpeton.
  2. Originally considered a chroniosuchian, Laosuchus now nests between Eryops and the CochleosaurusNigerpeton clade among basal tetrapods.
  3. The presumed cranial spines of Stegops are the obtuse squamosals crushed flat. A new reconstruction now nests Stegops with Tersomius.
  4. Long-limbed Kirktonecta now nests basal to short-limbed Sauropleura and snake-like Acherontiscus and their respective clades.
  5. Short-limbed Asaphestera now nests with similar Utaherpeton.

Adding taxa adds insight,
while doing so illuminates errors, many of which have now been corrected.