Evolution of the Dinosaurs YouTube video by Manabu Sakamoto PhD

One of Dr. Sakamoto’s major interests is
“How did major groups of animals radiate?” So we have similar interests. This slide show lecture apparently on ZOOM (or a similar format) is 56 minutes in duration and was streamed live March 12, 2021.

Sakamoto received his PhD from the U of Bristol in England,
which does not bode well. That’s where too many recent myths about pterosaurs and dinosaurs had their genesis.

In his slide labeled ‘Birds are dinosaurs’
Sakamoto includes an illustration of Microraptor (Fig. 1), which has wings and feathers, but is not a bird in the large reptile tree (LRT, 1817+ taxa), but a bird mimic arising from Ornitholestes  (Fig. 1). Sakamoto had so many birds to choose from, but chose a non-bird.

Figure 1. Changyuraptor to scale with Ornitholestes, Scriurumimus and Microraptor.

Figure 1. Changyuraptor to scale with Ornitholestes, Scriurumimus and Microraptor.

In his slide labeled ‘What makes a dinosaur?’
Sakamoto includes four illustrations and photos of four traits he reports are common to dinosaurs. That’s called a “Pulling a Larry Martin” because it is fraught with convergence in various non-dinosaurs. He should have used the “Last Common Ancestor (LCA) hypothesis.

In his slide labeled ‘Dinosauromorphs’
Sakamoto includes lagerpetids and notes reduced toes 1 and 5. That’s not true of sauropods, which have a huge toe 1. Lagerpetids are not related to dinosaurs when more taxa are added. Lagerpetids are proterochampsids convergent with dinosaurs. He lists Marasuchus among the dinosauromorphs. In the LRT it nests as a basal theropod even though the acetabulum is 90% not-perforated, as in ankylosaurs (see “Pulling a Larry Martin” above).

So far, not so good,
and we’re only 16 minutes into the video. So glad I did not waste time and money getting an education at the University of Bristol, like Dr. Sakamoto did. The professional academic Bristol program in dinosaurs is evidently behind the times.

In his slide labeled ‘A modern definition of Dinosauria’
Sakamoto correctly reports, dinosaurs are “members of the least inclusive clade containing Triceratops horridus and Passer domesticus (house sparrow),” but incorrectly includes ‘Dinosauromorphs’ as outgroup taxa between Crocodylomorpha and Dinosauria. In the LRT there are no taxa between Crocodylomorpha and Dinosauria.

In his slide labeled ‘major dinosaur groups’
Sakamoto reaches into the past to divide dinosaurs into Saurischia and Ornithischia. By contrast the LRT, with more taxa, divides dinosaurs into Theropoda and Phytodinosauria (Fig. 2) with a set of herrerasaurids preceding this split. So far Sakamoto is extending the reputation of U of Bristol for perpetuating myths.

Figure 2. Subset of the LRT focusing on the Phytodinosauria with Buriolestes at its base.

Figure 2. Subset of the LRT focusing on the Phytodinosauria with Buriolestes at its base.

In his slide labeled ‘…but there is only one true tree!’
Sakamoto presents his best estimate from data: an unresolved branching of Sauropodomorpha, Theropoda and Ornithischia. Based on what Sakamoto has presented thus far, the problem in Sakamoto’s presentation appears to be due to taxon exclusion. The LRT fully resolves the origin of dinosaurs by including more taxa. So why go to Bristol when you can learn with complete resolution online here?

In his slide ‘Dating dinosaur origins’
Sakamoto attempts to time the origin of dinosaurs, but without resolution or precise timing. In the LRT the dino-croc split occurred prior to the Ladinian (Late Middle Triassic) when the most primitive LCA of Dinosauria, PVL 4597 roamed South America.

 

Figure 4. The PVL 4597 specimen nests at the base of the Archosauria, not with Gracilisuchus.

Figure 3. The PVL 4597 specimen nests at the base of the Archosauria, not with Gracilisuchus.

In his slide ‘Early dinosaurs spread across the globe,
but started out just in the Southern hemisphere’ Sakamoto graphically considers Ladinian Lagerpeton and Asilisaurus ‘Basal Dinosauromorpha’, but verbally calls them early dinosaurs. Neither are dinosaurs in the LRT. Asilisaurus is a poposaur, the proximal outgroup for the Archosauria. Like many of his contermporaries, Sakamoto completely ignores the basal bipedal crocodylomorphs that the LRT nests as the proximal outgroup to the Dinosauria.

At this point we’re 30 minutes in
and very little Sakamoto has reported so far is verified by the LRT.

So we’re going to stop here.
The ratio of myth to fact is way too high. The ratio of missing taxa to included taxa is also way to high. Sakamoto now teaches at the U of Lincoln. If you are thinking of spending tuition money there, you have this preview to help you in your decision.

 

 

 

 

 

 

 

 

 

 

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