Talk:Dilophosaurus/GA2

GA Review

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Reviewer: Jens Lallensack (talk · contribs) 11:04, 3 February 2018 (UTC)

Will start reading soon! --Jens Lallensack (talk) 11:04, 3 February 2018 (UTC)

Starting with the description part …

The description part is mostly based on the old description of Welles. It would add to the article to synchronize it with a more recent description (e.g., Tykoski and Rowe, 2004). Some problems that appeared:

• The use of the term "pectoral vertebrae" is slightly problematic. According to the review of Tykoski and Rowe, 2004, p. 55: "Welles (1984) labeled the tenth cervical and first four dorsal vertebrae in Dilophosaurus as pectorals, recognized by the position of the parapophysis straddling the neurocentral suture. This convention has not been widely adopted, and we divide the theropod presacral series into only cervical and dorsal regions".

I changed the numbers according to your quote, does it look right? And added a citation to Tykoski/Rowe, though I don't have it... FunkMonk (talk) 15:13, 4 February 2018 (UTC)

• Also, it appears questionable to state that sacral vertebrae are "dorsal vertebrae between the hips", as dorsal vertebrae are defined to be presacrals.

I've cut out the parenthesis, the text makes it clear the sacrals run the length of the ilium, so that should indicate their position to the reader. FunkMonk (talk) 15:13, 4 February 2018 (UTC)

• Tykoski and Rowe (2004) question that there are only four sacrals in Dilophosaurus and Liliensternus, stating that this was based on "subadult or incomplete individuals".

I've cut the number out. FunkMonk (talk) 15:13, 4 February 2018 (UTC)

• The description lists many features with are typical for many basal theropods (e.g., shape of the atlas, posterior excavations of the cervical centra). It would be nice to know which of these are really characteristic, or even autapomorphic, for this genus.

Here again the age of the paper is probably a problem. Maybe I should add a sentence that sums up what actually distinguishes Dilophosaurus, as I recently added at the end of the description of Nemegtomaia? Though there seem to be at least two or three recent diagnoses, which are not entirely consistent, if I recall correctly... Or maybe it's better to just note which features are unique whenever they are mentioned, as in other articles, since Nemegtomatia doesn't have multiple sections in the description, and maybe isn't a good model for this much longer one. FunkMonk (talk) 14:06, 4 February 2018 (UTC)

I've now stressed when a feature is unique (which only appears to be a handful). FunkMonk (talk) 22:42, 6 February 2018 (UTC)

• According to Tykoski and Rowe: "In Dilophosaurus, serrations are on at least the second and third premaxillary teeth but absent on the fourth (Welles 1984)". This appears to be an interesting feature not occuring in related genera, and could be added.

Added. Welles describes the teeth in a pretty confusing way, I found. And his writing is generally a bit convoluted, so it was sometimes hard to consolidate different statements from different parts of the paper... FunkMonk (talk) 15:13, 4 February 2018 (UTC)

Other comments/questions:

• Hindwards and below, the premaxilla formed a wall for a gap between itself and the maxilla called the subnarial gap – I don't fully understand the formulation. What does "formed a wall" mean? How do the terms "gap" relate to the absence of teeth? It does not become clear what the difference between the "gap" and the "pit" actually is.

I find Welles a bit convoluted on this, but it seems the pit is within the gap. As for "wall", I think "border" could be a better way of saying it, but I wonder if that would be veering too far from the source? I'll quote Welles on this here (p. 144), maybe you can make more sense of it: "Posteroventraly it forms wall for the gap and pit between it and the maxilla (herein termed the subnarial gap and pit). The gap is formed by the failure of the premaxilla to meet the maxilla on the side of the face, by 23 mm, and the pit is a deep excavation inside the gap that is formed equally by the two bones. The pit lies entirely behind the premaxillary tooth row, and is walled medially by a downward plate from the posteromedial process, the ventral keel of the premaxilla". FunkMonk (talk) 15:13, 4 February 2018 (UTC)

I just had a look at the sources – I am quite sure that the "gap" only refers to the gap in the upper tooth row, the absence of teeth. "Pit" is referring to the indent which is formed by the anterior border of the maxilla and the ventral border of the lateral surface of the premaxilla; both borders form an acute angle. And "wall" means this medial sheet of bone of the premaxilla which, in lateral view, lies behind the pit. Are you sure with your wording also termed a "kink", "notch", or diastema? The gap is a diastema, yes, but "kink" and "notch" I think might be rather other terms for the nubnarial pit? --Jens Lallensack (talk) 22:00, 8 February 2018 (UTC)

Hmmm, I'm pretty sure "subnarial gap" (according to Welles) is just the gap between the premaxilla and maxilla; in the 2000 Ceratosaurus paper, the gloss says "subnarial gap - gap between the premaxilla and the maxilla on the side of the face", and Welles 1984 has a similar gloss. Note that it doesn't mention the teeth. The gloss then says " subnarial pit - cavity inside the subnarial gap, extending into the premaxilla and the maxilla". So how I read it, these are two features, the first of which results in a gap in the tooth row, and the other is an extension within the subnarial gap, which seems to be visible on this image[1]. But I can see Tykoski/Rowe say "This relationship creates a subnarial gap, or diastema, in the upper tooth row", which may be why things are muddled. I'm inclined to go with Welles, who seems to have invented the term "subnarial gap", though later authors seem to have imprecisely used the term as a synonym for diastema. As for the alternate terms, Paul says "It is odd how extreme the kink between the premaxilla and maxilla is". On the other hand, Naish says "a prominent notch in the upper jaw's toothrow". Therefore I have now separated the "notch" and diastema explanations to only explain the gap in the toothrow, though this may be too much interpretation on my part. FunkMonk (talk) 12:39, 9 February 2018 (UTC)

All right, that makes sense. Thanks for the explanation! --Jens Lallensack (talk) 22:31, 9 February 2018 (UTC)

• The nasal process (backwards projection from the premaxilla) – "nasal process" does not necessarily refer to the premaxilla. Also, the premaxilla has two backwards projecting processes, one above the naris and one below. This could be a bit clearer.

Welles refers to the nasal process as singular in the section about the premaxilla (p. 144), so I wonder how to get around this? FunkMonk (talk) 15:13, 4 February 2018 (UTC)

What I meant is only a minor issue, as the reader may not know which of the two processes you are referring to. What about "The upper of the two backwards extending processes of the premaxilla was long and low, and formed most of the upper border of the elongated naris" or "The premaxilla had two posteriorly directed processes forming the anterior portion of the elongated naris; the upper process was long and low and also formed most of the upper border of the naris." or something similar? --Jens Lallensack (talk) 22:00, 8 February 2018 (UTC)

I took your first option, though as noted below, Welles refers to the upper process as the "nasal process", while Tykoski/Rowe refers to the lower one as the "premaxillary process", but not sure whether this is just due to overall different terminology, or different terms for each process. FunkMonk (talk) 12:39, 9 February 2018 (UTC)

Tykoski and Rowe actually refer to the lower process as the premaxillary process, so I guess each has its own name after all? FunkMonk (talk) 22:42, 6 February 2018 (UTC)

• Seen from below, the premaxilla had an oval area that contained alveoli (tooth sockets). – As the premaxilla usually containes teeth, better write "contained the alveoli". Maybe "The underside of the premaxilla containing the alveoli (tooth sockets) was oval"?

Took your wording. FunkMonk (talk) 15:13, 4 February 2018 (UTC)

• Would be nice to know how much the nasal and lacrimal are contributing to the crest, respectively. --Jens Lallensack (talk) 18:29, 3 February 2018 (UTC)

Since the only specimen preserving crests has never been described (apart from in a short diagnosis by Caranno and co. 2012, a full description is presumably in the works by Padian, who requested that Tykoski did not describe the crest in 2005), it is not possible to say yet where the sutures lie... Unless we dig up Stephan Pickering's obscure article[2]... FunkMonk (talk) 16:12, 4 February 2018 (UTC)

Thanks for reviewing! I guess the main problem here is that I seem to have overlooked the existence/significance of Tykoski and Rowe, 2004... Do you have it digitally? FunkMonk (talk) 14:06, 4 February 2018 (UTC)

It does seem Tykoski/Rowe 2004 was once quoted in the article[3], but not for any actual info, it was just placed after a citation for Tyskoski 2005, and a sentence about that paper... So it may have been removed when I started cleaning up citations, there was a lot of redundant stuff not attached to any unique info... FunkMonk (talk) 14:23, 4 February 2018 (UTC)

Tykoski and Rowe, and the other reviews of the book, are very valuable as sources as they put the old description into modern context. In my opinion it is always good to state something like "Uniquely for this genus …" or "as in the related …" or "as in other basal theropods …", as this is important information. I sent it to you per mail! --Jens Lallensack (talk) 16:56, 4 February 2018 (UTC)

Continuing now with the review (more comments later):

• Link to hypodigm does not lead to an article. --Jens Lallensack (talk) 16:56, 4 February 2018 (UTC)

Removed, and I think it's sufficiently explained in the parenthesis. FunkMonk (talk) 13:00, 6 February 2018 (UTC)

• The second paragraph in the section "Motion" is a bit hard to follow.

• They found that Dilophosaurus would have been able to hold its humerus almost parallel with its scapula, but not more horizontal than that. – I didn't read the paper, but is is possible to formulate it more clearly and readable for laypeople? Like "They found that Dilophosaurus would have been able to stretch its arm so that the humerus is almost in-line with the scapula, although the humerus couldn't be elevated beyond this point" or something similar?

The source says this: "In these taxa, the humerus can retract to a position nearly parallel with the scapula, but cannot protract further than a subvertical position". Maybe I've "translated" the last part wrong, what do you think? FunkMonk (talk) 13:00, 6 February 2018 (UTC)

Ah, this way around, got it. But I don't understand your wording "but not more horizontal than that"; when pulled backwards to a subparallel position with the scapula, it would already been more than horizontal? What about "Dilphosaurus would have been able to draw its humerus backwards until it was almost parallel with the scapula, but could not move it forwards to a more than vertical orientation" --Jens Lallensack (talk) 22:00, 8 February 2018 (UTC)

Took your wording, my reasoning was that "parallel with the scapula" was basically the same as "a subvertical position". FunkMonk (talk) 12:39, 9 February 2018 (UTC)

• It reads like the authors are contradicting themselves in the two studies cited. The elbow could approach full extension, but not achieve it completely, and not flex at a right angle. and the elbow would have been close to a right angle – how to make sense of this?

The first source says "the elbow can approach but not achieve full extension and right-angle flexion" and the second says "the resting orientation of the elbow is close to a right angle and the resting orientation of the wrist is such that the hand exhibits only slight ulnar deviation from the antebrachium". So I assume the confusion is because my wording seems to preclude the right angle flexion entirely, so I've reworded that. FunkMonk (talk) 13:00, 6 February 2018 (UTC)

• In 1984 Welles interpreted the fact that three individuals were found closely together, and the presence of criss-crossed trackways nearby, as indications that Dilophosaurus traveled in groups.[2] Gay agreed that they may have traveled in small groups, but noted that there was no direct evidence for this, and that flash floods could have picked up scattered material from different individuals and deposited them together. – It is slightly confusing that you first talk about evidence from tracks, and in the second sentence apparently about evidence from body fossils (it is not possible to wash together footprints). Did somebody suggest that Dilophosaurus traveled in groups based on body fossils? If yes, I would add it here. If not, there is no need to reject a claim that has not been made, so maybe just delete that last part of the sentence?

Welles used the closely associated fossils (see beginning of sentence) and tracks as evidence, but Gay rejected the body fossils as evidence, I've clarified that by saying "bones" instead of "fossils", better? FunkMonk (talk) 13:00, 6 February 2018 (UTC)

• No issues apparent in the remainder of the article, great stuff. --Jens Lallensack (talk) 20:53, 4 February 2018 (UTC)

Thanks, I've fixed some issues, but also left some questions where I'm unsure. I'll look for what I can add from the sources you sent me now. FunkMonk (talk) 13:00, 6 February 2018 (UTC)

Now it should be ready for check... FunkMonk (talk) 22:42, 6 February 2018 (UTC)

I answered the questions, rest looks good! One more thing: Weems did not suggest a quadrupedal locomotion for the Culpeper Quarry tracks; only 10 impressions were identified as manus impressions (with manual digits in an habitually hyperextended position, as speculated by Weems), and these were thought to have been made when the animal stopped; Weems stated that the trackmaker was fully bipedal. --Jens Lallensack (talk) 22:00, 8 February 2018 (UTC)

Fixed two issues above and added a question. As for Weems, are you sure? He specifically says "The manus prints associated with Kayentapus suggest that the manual digits normally were hyperextended during quadrupedal walking", "if the fingers of the manus were held in this position while walking in quadrupedal pose, Dilophosaurus would have made manus prints of only its metacarpal pads", and "this was not an unusual behavior for these dinosaurs while resting on their front feet. Rather, this was their normal method of quadrupedal progression.". FunkMonk (talk) 12:39, 9 February 2018 (UTC)

Thanks, looks very good now, I'm going to pass it quickly. As for the Culpeper quarry tracks, Weems 2006 writes on page 370: "Fewer than ten examples of manus prints were found associated with the thousands of pes prints of Kayentapus minor at this site. These were invariably associated with short segments within trackways where an animal either slowed (as indicated by abnormally short pace lengths) or came to a full stop and dropped onto all four feet." and "Within the twenty trackway segments documented on the lower level, only two stopping and/or slowing points with manus prints were found in trackway K-2 […] The sarcity of these prints indicates that the track maker of Kayentapus minor normally was a bipedal animal that dropped onto four feet only occasionally when it was progressing very slowly, standing still, or resting." So stating that the Culpeper trackmaker was quadrupedal is perhaps too much. --Jens Lallensack (talk) 22:31, 9 February 2018 (UTC)

And thanks back! I will send this to FAC now, bit I'm still a bit confused about the Weems issue. So he is not saying the trackway itself shows quadrupedal locomotion, but uses it to demonstrate that theropods could theoretically move quadrupedally in the way he describes? FunkMonk (talk) 22:47, 9 February 2018 (UTC)

I can only find this statement, Jens Lallensack, but it doesn't seem to rule out quadrupedal locomotion: "The scarcity of these prints indicates that the track maker of Kayentapus minor normally was a bipedal animal that dropped onto four feet only occasionally when it was progressing very slowly, standing still, or resting." To me, it seems that the tracks in question are the exception he mentions. FunkMonk (talk) 00:01, 15 February 2018 (UTC)

Sorry for taking ages to respond. You are right, I partly misread your sentence, it is basically correct as you are referring to a single trackway from a quarry. But still, I perhaps would have stated that Weems thinks it was only able to move quadrupedally when moving very slowly, and that this would be rather the exception. There are some other bits on the ichnology part that I miss – am I allowed to add a bit? --Jens Lallensack (talk) 06:02, 15 February 2018 (UTC)

Of course! FunkMonk (talk) 08:20, 15 February 2018 (UTC)