New Attenborough “Rise of Animals” videos on YouTube

Figure 1. Frame from David Attenborough's "Rise of the Animals part 1 and part 2 on YouTube. Click to view part 1.

Figure 1. Frame from David Attenborough’s “Rise of Animals part 1 and part 2 on YouTube. Click to view part 1.

A new YouTube video by David Attenborough does a great job of chronicling the Rise of Animals in two parts. Highly recommended.

Lots of great fossils are shown, many from China where basal chordates, basal vertebrates, basal birds, and basal mammals have all been found. The animals were also excellently animated.

Messel primates are featured, along with megafauna from the White River formation. Unfortunately various reptile clades were ignored. Perhaps that was due to the lack of a generally accepted amniote tree based on generic taxa, as portrayed here, and to a general theme leading toward humans, rather than snakes and turtles.

You can’t beat David Attenborough’s narration, which brings equal parts of authority and delight at every discovery and clade node.

Figure 1. From the Beginning - The Story of Human Evolution was published by Little Brown in 1991 and is now available as a FREE online PDF from DavidPetersStudio.com

Figure 2. From the Beginning – The Story of Human Evolution was published by Little Brown in 1991 and is now available as a FREE online PDF from DavidPetersStudio.com. Click image to view and download.

Attenborough also strings together a gradually accumulating list of hominid traits, starting with basal chordates, echoing the pattern and theme of the 1991 book, From the Beginning, available free online as a PDF file here.

…and updated here at ReptileEvolution.com.

A few missed opportunities here. There is no reason to restrict basal birds like Microraptor to a a gliding mode when the bones indicate that flapping was practiced, both on the ground and in the air.

We’re not sure if basal reptiles had scales, since neither mammals (synapsids) nor birds (dinosaurs) have them. That derived dinos (but not birds), lizards, crocs and turtles all had/have scales appear to be separate convergent developments. If anyone has skin data for early archosauriformes (other than paired dorsal scutes), please let me know.

Contra Attenborough’s samples, the origin of the amniote egg does not include the development of a shell. Rather just an amniotic membrane is common to all amniotes and this story begins in the Viséan. Shells developed by convergence in both major branches of the Reptilia (=Amniota).

 

My, what big flippers you have!

Guizhouichthyosaurus tangae (Cao et Luo in Yin et al., 2000, Late Triassic) is an ichthyosaur with really big flippers derived from a sister to Phalarodon and basal to Shonisaurus popularis.

Figure 1. Guizhouichthyosaurus in situ in ventral aspect. This specimen has some of the biggest flippers among ichthyosaurs, rivaling those belonging to plesiosaurs, which makes one hypothesize a distinct mode of swimming.

Figure 1. Guizhouichthyosaurus in situ in ventral aspect. This specimen has some of the biggest flippers among ichthyosaurs, rivaling those belonging to plesiosaurs, which makes one hypothesize a distinct mode of swimming. The large number of ribs, though, along with the sinuous backbone, suggest that undulation was still used as well.

Known from several specimens, Guizhouichthyosaurus, had a long rostrum and sharp teeth (Fig. 2). When a sea creature has such large flippers the tendency is to imagine that it swam using those paddles/underwater wings. It probably had only a rudimentary tail fin, like Phalarodon or Mixosaurus.

Figure 2. Guizhouichthyosaurus tangae skull preserved in three dimensions.

Figure 2. Guizhouichthyosaurus tangae skull preserved in three dimensions. Tracing from Maisch et al. 2015.

Guizhouichthyosaurus provides clues to the ancestry of the big-fippered Shonisaurus, one of the giants among ichthyosaurs.

Figure 2. Ichthyosaur subset of the large reptile tree.

Figure 3. Ichthyosaur subset of the large reptile tree. 

Guizhouichthyosaurus is also related to the smaller-flippered and misnamed ‘Cymbospondylus’ buchseri (Sander 1989, Fig. 4), which looks a bit like a mosasaur. Now it needs a new generic name. Earlier we looked at other ichthyosaurs more recently misnamed by Sander et al. (2011).

Figure 4. 'Cymbodpondylus' buchseri did not have such large flippers, but did have a long narrow skull and robust elongate torso.

Figure 4. ‘Cymbodpondylus’ buchseri did not have such large flippers, but did have a long narrow skull and robust elongate torso.

I have previously overlooked and ignored most ichthyosaurs because I was more interested in their ancestry among Wumengosaurus, Thaisaurus and beyond to the mesosaurs. But they are a fascinating clade with some odd morphologies worth looking into.

References
Maisch M et al. 2015. Cranial osteology of Guizhouichthyosaurus tangae (Reptilia: Ichthyosauria) from the Upper Triassic of China. Journal of Vertebrate Paleontology 26(3): 588-597.
Yin G-Z, Zhou X, Cao Y, Yu Y and Lu Y 2000. A preliminary study on the early Late Triassic marine reptiles from Guanling, Guizhou, China. Geology-Geochemisty 28(3):1–23 (Chinese with English abstract).
Sander PM 1989. The large ichthyosaur Cymbospondylus buchseri sp. nov., from the Middle Triassic of Monte San Giorgio (Switzerland), with a survey of the genus in Europe. Journal of Vertebrate Paleontology 9(2): 163-173.
Sander PM, Chen X-C, Cheng L and Wang X-F 2011. Short-snouted toothless ichthyosaur from China suggests Late Triassic diversification of suction feeding ichthyosaurs. PlosOne DOI: 10.1371/journal.pone.0019480

Male and Female Stegosaurus?

Usually I leave dinosaurs to the dinosaur experts…
but this new paper seems to be appropriate fodder.

Figure 1. Click to enlarge. According to Saitta 2015, male and female Stegosaurus can be differentiated by their plates.

Figure 1. Click to enlarge. According to Saitta 2015, male and female Stegosaurus can be differentiated by their plates.

 

A recent PlosOne paper by Saitta (2015) claims Stegosaurus sexual dimorphism can be determined by plate shape (Fig. 1).

Unfortunately others disagree.
Drs. Kevin Padian and Ken Carpenter raised serious issues here.

And part of the problem,
perhaps a major part of the problem, is the lack of articulation in the specimens (Fig. 2).

Figure 2. An insitu plot of the Stegosaurus material. Deep blue colors indicate plates, provided by Saitta. Three pelves of different shapes and sizes are marked. Arrows point anteriorly. This is a jumble. And the plates are disarticulated.

Figure 2. An insitu plot of the Stegosaurus material. Deep blue colors indicate plates, provided by Saitta. Three pelves of different shapes and sizes are marked. Arrows point anteriorly. This is a jumble. And the plates are disarticulated.

A plot
of the in situ specimens (Fig. 2)  indicates that at least three individuals are shown in disarray here, (five were mentioned and likely the others are from other parts of the site). One is smaller than the others. How is it possible to match plates to pelves? And how do all the other bones fit herel? I would not want to attempt a reconstruction with this scattering of at least three individuals.

This is a hard hypothesis to substantiate. 
Not only do different stegosaurs have different shaped plates, but nearly every plate on every stegosaur is distinct, even in articulated specimens.

What I find most interesting…
How did Drs. Padian and Carpenter get their comments published online at ScienceMag.org on the same day the PlosOne paper came online? Only Carpenter is listed in the acknowledgments (for providing specimen photos). Both are listed in the references.  I assume they were not referees, but must have been granted access to the paper prior to publication.

And, why are their no comments in the COMMENTS section for this paper (at the time of this publication)? That’s the standard operating procedure for PlosOne papers.

References
Saitta ET 2015. Evidence for Sexual Dimorphism in the Plated Dinosaur Stegosaurus mjosi (Ornithischia, Stegosauria) from the Morrison Formation (Upper Jurassic) of Western USA. PLoS ONE 10(4): e0123503. doi:10.1371/journal.pone.0123503

Cymbospondylus – primitive or derived?

Cymbospondylus petrinus is a 20-30 foot (up to 8.33 m) long Middle Triassic ichthyosaur with a long, low toothy skull, short broad paddles and a long low, tail (Fig. 1).

Figure 1. Cymbospondylus skull and overall in lateral view.

Figure 1. Cymbospondylus skull and overall in lateral view.

The question is: 
Is Cymbospondylus primitive and derived from Chaohusaurus and Grippia (as per Motani 1999)? Or is Cymbodpondylus derived and derived from Mixosaurus (as per Maisch and Matzke (2000, 2003) and the large reptile tree)?

Cymbospondylus appears to be primitive.
It has the long snaky body of basal ichthyosaurs, like Utatsusaurus and Thaisaurus.

However, if Cymbospondylus nests between Grippia and Mixosaurus
it is a giant nesting between two relatively small to tiny ichthyosaurs.

Figure 2. Cymbospondlyus compared to sister taxa according to the large reptile tree to length (above) and to scale (below). Shown in gray is Shonisaurus popularis, which is compared to to Shonisaurus sikanniensis.

Figure 2. Cymbospondlyus compared to sister taxa according to the large reptile tree to length (above) and to scale (below). Shown in gray is Shonisaurus popularis, which is compared to to Shonisaurus sikanniensis.

Motani (1999)
nested Cymbospondylus at the base of the Ichthyosauria between Chaohusaurus + Grippia and Mixosauria (Mixosaurus and all higher ichthyosaurs (Merriamosauria).

Maisch and Matzke (2000, 2003)
nested Cymbospondylus a little higher, between Mixosauria and Merriamosauria.

Figure 2. Ichthyosaur subset of the large reptile tree.

Figure 2. Ichthyosaur subset of the large reptile tree.

The large reptile tree (Fig. 2) nested Cymbspondylus petrinus between Mixosaurus and the toothless Guanlingsaurus liangae YGMR SPC V03017 + the possibly toothless giant Shonisaurus sikanniensis (apart from ‘Cymbospondylus’ buchseri, which here (Fig 2) nests with Shonisaurus popularis in a distinct clade). So we should expect several taxa transitional between Mixosaurus and these giants and near giants.

Despite their long, snaky look, Cymbospondylus and kin are not primitive, but may have reverted to that morphology as they grew to larger and larger size.

References
Leidy J 1868. Notice of some reptilian remains from Nevada: Proceedings of the American Philosophical Society 20:177-178.
Merriam JC 1908. Triassic ichthyosauria with special references to the American forms. Memoirs of the University of California 1: 1-196.
Yin G-Z, Zhou X, Cao Y, Yu Y and Luo Y 2000. A preliminary study on the earlyLate Triassic marine reptiles from Guanling, Guizhou, China. Geology-Geochemisty 28(3):1–23 (Chinese with English abstract).

Ichthyosaur skulls in phylogenetic order (so far…)

Figure 1. Ichthyosaur skulls in phylogenetic order (top to bottom). Those below the red line have not been ordered yet. Boxed specimens are not yet tested. Many illustrations from Maisch and Matzke 2000.

Figure 1. Ichthyosaur skulls in phylogenetic order (top to bottom). Those below the red line have not been ordered yet. All of those below the red line have a naris/lacrimal contact and many do not have a naris/maxilla contact. They are mostly Jurassic and Cretaceous taxa. Boxed specimens are not yet tested. Many illustrations from Maisch and Matzke 2000. Click to enlarge. Not to scale.

Ichthyosaur phylogeny has been examined by Motani (1999), Maisch and Matzke (2000) and Maisch (2010). The large reptile tree (Fig. 2) offers yet another solution and finally have the correct outgroup taxa included. All four of these studies are broadly similar, but do differ from each other in detail.

Figure 2. Ichthyosaur subset of the large reptile tree. This tree follows the broad topology of prior trees, but all trees differ in detail.

Figure 2. Ichthyosaur subset of the large reptile tree. This tree follows the broad topology of prior trees, but all trees differ in detail.

Note (Fig. 2) the two Shonisaurus specimens do not nest together. Neither do the two Cymbospondylus specimens. Earlier we talked about all the specimens attributed to Shastasaurus.

This is a continuing study.

References
Maisch MW 2010. Phylogeny, systematics, and origin of the Ichthyosauria – the state of the art. Palaeodiversity 3: 151-214.
Maisch MW and Matzke AT 2000. “The Ichthyosauria”. Stuttgarter Beiträge zur Naturkunde: Serie B 298: 159.
Motani R 1999. Phylogeny of the Ichthyopterygia. Journal of Vertebrate Paleontology 19(3):473-496.’

Shonisaurus popularis vs. ‘Shonisaurus’ sikanniensis

Earlier we looked at the mistaken renaming of ‘Shonisaurus sikanniensis’ by Sander et al. 2011 to Shasatasaurus sikanniensis. S. sikanniensis and Shastsaurus don’t nest together, and share relatively few traits, so they can’t be the same genus.

Nicholls and Manabe (2004) described Shonisaurus’ sikanniensis (Fig. 1) as a 21m monster, the largest known ichthyosaur.

Figure 7. The giant sixth putative Shastasaurus, S. sikanniensis.

Figure 7. The giant sixth putative Shastasaurus, S. sikanniensis.

Unfortunately
their scale bars (Fig. 1) don’t confirm that length, but suggest one closer to 18 meters. That includes the 1 meter of missing distal tail they presume.

Worse yet
‘Shonisaurus sikanniensis’ shares very few traits with Shonisaurus popularis (Camp 1976, 1080, Kosch 1990; Fig. 2), the holotype for the genus. S. popularis nests with Guizhouichthyosaurus. S. sikanniensis nests with Cymbospondylus and YGMR SPC V3107, a specimen formerly attributed to Shastasaurus linagae by Sander et al. 2011. Like   S. sikanniensis, the 3107 specimen has a skull twice as wide as tall and a large orbit.

Figure 2. Shonisaurus populars compared to 'Shonisaurus' sikanniensis to scale.  Note the distinct skull and pectoral girdle morphologies.

Figure 2. Shonisaurus populars compared to ‘Shonisaurus’ sikanniensis to scale. Note the distinct skull and pectoral girdle morphologies. Click to enlarge. The torso is not so deep in S. popular is when they are angled back, as shown in most skeletons.

Interestingly,
no teeth are found in adult Shonisaurus popularis, only juveniles. Both Shonisaurus have expanded rib tips. Both are giants. Both may be toothless as adults.

Figure 3. Two ichthyosaurs once considered Shastasaurus suction feeders. The 3107 specimen nests with S. sikanniensis and both taxa need a new genus name. The 3108 specimen is very primitive and nests with Mikadocephalus.

Figure 3. Two ichthyosaurs once considered Shastasaurus suction feeders. The 3107 specimen nests with S. sikanniensis and both taxa need a new genus name. The 3108 specimen is very primitive and nests with Mikadocephalus.

I’m not sure how
and why my trees differ in detail from previously published work, but during the course of this study I’ve found prior data that did not agree with one another. So, evidently the data can be interpreted more than one way. And too often, I’m stuck with using published tracings as data without a photo to confirm. On the other hand, we’re in close agreement on many taxa and sister taxa recovered by the large reptile tree do resemble one another and make sense with regards to evolutionary patterns. Putting the reconstructions together, side-by-side, continues to be an important way to uncover prior and current mistakes.

Figure 4. Cladogram with Shonisaurus popular is added. Bootstrap scores shown.

Figure 4. Cladogram with Shonisaurus popular added. Bootstrap scores shown. Note the two Shonisaurus specimens do not nest together, nor do they share many traits.

References
Camp CL 1976. Vorläufige Mitteilungüber grosse Ichthyosaurier aus der oberen Trias von Nevada. Österreichische Akademie der Wissenschaften, Mathematisch-Naturwissenschaftliche Klasse, Sitzungsberichte, Abteilung I 185:125-134.
Camp CL 1981. Child of the rocks – The story of the Berlin-Ichthyosaur State Park. Nevada Bureau of Mines and Geology, Special Publication 5, 36 pp.
Kosch, BF 1990. A revision of the skeletal reconstruction of Shonisaurus popularis (Reptilia: Ichthyosauria). Journal of Vertebrate Paleontology 10 (4): 512.
Nicholls EL, Manabe M 2004. Giant ichthyosaurs of the Triassic – a new species of Shonisaurus from the Pardonet Formation (Norian: Late Triassic) of British Columbia. Journal of Vertebrate Paleontology 24 (3): 838–849.
Sander PM, Chen X-C, Cheng L and Wang X-F 2011. Short-snouted toothless ichthyosaur from China suggests Late Triassic diversification of suction feeding ichthyosaurs. PlosOne DOI: 10.1371/journal.pone.0019480

Xinminosaurus, yet another basal ichthyopterygian

I had no idea
so many basal ichthyopterygians were out there. Oddly, their original authors suspected the same, but did not put forth cladograms to support their hunches. Plus, some were Middle Triassic in age, while more derived taxa are found in Early Triassic strata. Finally, the proximal outgroups for ichthyosaurs (Fig. 2) were not recognized.

Figure 1. Xinminosaurus in situ and with DGS reconstructed.

Figure 1. Xinminosaurus in situ and with DGS reconstructed.

Xinminosaurus catactes (Jiang et al. 2008, Middle Triassic, GMPKU-P-1071, 1.6m). is another basalmost ichthyopterygian known for over 7 years now. Distinct from its closest kin, the teeth of Xinminosaurus were large squarish blocks. The paddles were short and broad with just a few extra phalanges (3-5-5-5-2) on the manus.

Figure 2. Cladogram of ichthyosaurs and kin with five putative Shastasaurus specimens in pink.

Figure 2. Cladogram of ichthyosaurs and kin with Xinminosaurus nesting close to the base of the Ichthyopterygia or as a transitional taxon proximal to that clade. 

Xinminosaurus had smaller cervicals than in Thaisaurus. The humerus was shorter. The scapula was not as tall. The hind limbs were shorter, more paddle-like. All these traits are more ichthyosaurian. So these taxa (Fig. 2), together with Wumengosaurus, provide a gradual accumulation of ichthyosaurian traits.

The origin of ichthyosaurs
is not such a mystery when you employ 530 taxa, but this topology was recovered when only half the current number of taxa were known, when Stereosternum was the sister to the Ichthyopterygia. The rest have been added over the last four years.

Whenever basal ichthyosaurs are mentioned,
Cartorhynchus and Omphalosaurus are considered. The large reptile tree found Cartorhynchus nested close to the pachypleurosaur, Qianxisaurus. Omphalosaurus is known by too few bones to be included in the large reptile tree, but earlier, it was considered close to Sinosaurosphargis.

References
Jiang D, Motani R, Hao W, Schmitz L, Rieppel O, Sun, Sun Z 2008. New primitive ichthyosaurian (Reptilia, Diapsida) from the Middle Triassic of Panxian, Guizhou, southwestern China and its position in the Triassic biotic recovery. Progress in Natural Science 18 (10): 1315.