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705-805 Level|   Long Passage|   Science|                        
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 21 May 2022, 21:20
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8m41s and all correct. 4mins in Reading. Thanks for sharing this article!
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 24 Jun 2022, 20:33
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GMATNinja

So what the heck is up with Question #2?


csaluja
GMATNinjaTwo,

Hi GMATNinja, I was wondering could you please explain the difference between option B and E for Q2? I ended up picking option E but it was more of a lucky guess. Would greatly appreciate it if you could please shed some light on option B especially!
PAVANIJOSHI374
Hi,

I have a similar doubt.. For Q2, option B & option E are very similar.
How does one choose the right one?
Please help!!
Izzyjolly
I was down to B and D and ended up choosing B because I thought that the 2nd passage end in line 29.
How can we eliminate option B here? Please help.
manishk30
I also thought that the para 2 is ending at line 29 and chose the wrong option on that basis.

Indeed, the formatting for this particular passage makes it very tough for us to tell where one paragraph begins and the other ends. (Bunuel, any idea how to fix the formatting? You're the best technical wizard in the GMAT Club family. :))

Anyway, a closer look at the 2018 OG reveals that:

  • Paragraph 1 ends with the words, "development of the vertebrate skeleton."
  • Paragraph 2 ends with the words, "the earliest vertebrates were predators."
  • Paragraph 3 begins with the words, "The stiffening notochord."

Here's paragraph 2 (P2) in full:

Quote:
The vertebrate skeleton had traditionally been regarded as a defensive development, champions of this view postulating that it was only with the much later evolution of jaws that vertebrates became predators. The first vertebrates, which were soft-bodied, would have been easy prey for numerous invertebrate carnivores, especially if these early vertebrates were sedentary suspension feeders. Thus, traditionalists argued, these animals developed coverings of bony scales or plates, and teeth were secondary features, adapted from the protective bony scales. Indeed, external skeletons of this type are common among the well-known fossils of ostracoderms, jawless vertebrates that existed from approximately 500 to 400 million years ago. However, other paleontologists argued that many of the definitive characteristics of vertebrates, such as paired eyes and muscular and skeletal adaptations for active life, would not have evolved unless the first vertebrates were predatory. Teeth were more primitive than external armor according to this view, and the earliest vertebrates were predators.
This clarification might resolve a lot of doubts about the passage and question #2. But let's break it down to eliminate any lingering confusion.

Quote:
The second paragraph in the passage serves primarily to
OK, so why did the author write this paragraph?

P1 has already told us that the 1981 discovery -- of conodont remains along with conodont fossils -- has had important implications for hypotheses about the vertebrate skeleton.

In P2, the author then presents two opposing hypotheses about the vertebrate skeleton: The traditional view that it was a defensive development and an opposing view that the skeletal adaptations were part of a predatory evolution. The author offer some details for each side's hypothesis, but the point of the paragraph is to show us these two sides.

Let's see which answer choices line up with our understanding:

Quote:
A. outline the significance of the 1981 discovery of conodont remains to the debate concerning the development of the vertebrate skeleton
Nope! P2 doesn't outline the significance of this discovery in any way. The reason that the author writes P2 is to tell us about opposing hypotheses, not get further into the details of the 1981 discovery. Eliminate (A).

Quote:
B. contrast the traditional view of the development of the vertebrate skeleton with a view derived from the 1981 discovery of conodont remains
(B) is very tempting, but when you read closely, two thoughts should come to mind:

  • Is the author writing P2 to contrast two views?
  • Are the views being contrasted "the traditional view of development of the vertebrate skeleton" and "a view derived from the 1981 discovery"?

You could argue that yes, the author is contrasting two hypotheses. And one of those hypotheses is the traditional view of how and why the vertebrate skeleton developed. We are close to keeping this answer choice.

But when you refer back to the passage, was the second view (of early vertebrates as predators) "derived from the 1981 discovery"? Not quite. The second paragraph doesn't create a link between the view of predatory evolution and the 1981 discovery of conodont remains. The second paragraph doesn't even mention conodonts. That's why we eliminate (B) -- or at the very least, avoid falling in love with (B) right away.

Quote:
C. contrast the characteristics of the ostracoderms with the characteristics of earlier soft-bodied vertebrates
The author didn't write the second paragraph in order to contrast the characteristics of these two groups. Eliminate (C).

Quote:
D. explain the importance of the development of teeth among the earliest vertebrate predators
Choice (D) tempts us by identifying a thing that the author did in P2. But this choice doesn't tell us the reason why the author wrote P2. Because (D) is not answering the question we were asked, we can eliminate it without hesitation.

Quote:
E. present the two sides of the debate concerning the development of the vertebrate skeleton
Here we are! Choice (E) does seem similar to Choice (B), but it doesn't make the mistake of naming the wrong sides of this debate. Instead, (E) matches exactly what we know: The author wrote the paragraph in order to present two opposing hypotheses.

This answers the question directly, doesn't add any erroneous wrinkles, and doesn't get stuck on narrow details that miss the purpose of the paragraph. That's why (E) is distinct from (B) and (D). That's also why (E) is the best available choice.

I hope this explanation turned your "conodon'ts" into "can dos"! Please forgive my humor, it's an evolutionary defense mechanism against eye-burning GMAT passages. And I'm practicing my terrible "dad jokes" for when my daughter is old enough to understand them and roll her eyes at me...
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Dear GMATNinja,
I realize that you covered question 580 (According to the passage, the anatomical evidence provided by the preserved soft bodies of conodonts led scientists to conclude that) in detail. However, I just want to make sure that I am pulling the right support from the passage to justify the correct answer.  The support is: "The lack of any mineralized structures apart from the elements in the mouth indicates that conodonts were more primitive than the armored jawless fishes such as the ostracoderms". "Apart from elements in the mouth" refers to teeth, correct?

For question 581 (the second paragraph in the passage serves primarily to), can someone explain why Choice B is wrong in more detail?

Thank you!
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 28 Jun 2022, 13:12
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woohoo921

Dear GMATNinja,
I realize that you covered question 580 (According to the passage, the anatomical evidence provided by the preserved soft bodies of conodonts led scientists to conclude that) in detail. However, I just want to make sure that I am pulling the right support from the passage to justify the correct answer.  The support is: "The lack of any mineralized structures apart from the elements in the mouth indicates that conodonts were more primitive than the armored jawless fishes such as the ostracoderms". "Apart from elements in the mouth" refers to teeth, correct?

For question 581 (the second paragraph in the passage serves primarily to), can someone explain why Choice B is wrong in more detail?

Thank you!
Show more
Regarding your first question: yup, that's the right piece of the passage. And yes, "elements in the mouth" would mean teeth.

Regarding your second question: as we've mentioned in this passage breakdown, the second paragraph discusses two views from BEFORE the 1981 discovery. So, it's not correct to say that the second view was "derived from" the 1981 discovery. The view was already out there, and then the 1981 discovery provided additional support for that view.

I hope that helps!
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 13 Aug 2022, 04:40
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Hi experts, GMATNinja and others

P1 = Paragraph 1
P2 = Paragraph 2
P3 = Paragraph 3

I read all posts but only things I am still confused are that I cannot see any connection between P1 and P2 and between P1 and P3. Many posts tell that P2 doesn't link to P1 and those theories in P2 had existed before the discovery in 1981.

Could you pls show the hint or clue in the passage that which words or phrases that let us know P2 doesn't connect to P1 and P3 does connect to P3?
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 13 Aug 2022, 22:30
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Tanchat
Could you pls show the hint or clue in the passage that which words or phrases that let us know P2 doesn't connect to P1 and P3 does connect to P3?
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The paragraphs in GMAC's passages will not be unrelated. Without exception, GMAC chooses and edits RC passages so that their overall organization and interrelationships are clear.


First of all, this is a passage about science.
Remember how the scientific method works in general: You can't prove scientific theories/hypotheses, but you CAN disprove them (with discoveries/findings that contradict them).
This pair of basic observations has an immediate and profound consequence: ALL scientific progress consists entirely of DISPROVING / RULING OUT specific theories/hypotheses.

So, for instance, when you come to the part about "important implications for hypotheses" near the end of ¶1, you know for sure what those 'implications' are: One or more hypotheses will be ELIMINATED by the new findings. (Probably just one, because these passages are all very short by the usual standards of scholarly/academic/scientific articles.)

You can absolutely assume this, because that's how science HAS to work.



Quote:
Many posts tell that P2 doesn't link to P1
Show more

Well... they shouldn't say that, because that's just wrong. Paragraph 2 is very clearly and very closely connected to paragraph 1.

¶1 mentions that the 1981 findings had an effect on "hypotheses concerning the development of the vertebrate skeleton".
The entirety of ¶2 is dedicated to explaining two of these hypotheses—/1/ the 'traditional' hypothesis, and /2/ a newer hypothesis suggested by "other paleontologists"—in detail.

It's concerning that anyone could conclude that ¶1 and ¶2 are 'unrelated', because the connection is spelled out using repetition of exactly the same specific words only two or three lines apart!

• End of ¶1: "hypotheses concerning the development of the vertebrate skeleton"

• Beginning of ¶2: "The vertebrate skeleton had traditionally been regarded as a defensive development" ...okay, this is definitely one of the hypotheses just mentioned. This hypothesis is then explained in detail, followed by a newer, contrasting hypothesis.


¶3 describes scientific results. These MUST be the 1981 findings—even though "1981" isn't repeated—because anything else would just be ridiculous. (If these findings WEREN'T the ones from 1981, then the reference to 1981 findings in ¶1 would be left totally stranded and unexplained, AND ¶3 would be suddenly jumping into a description of findings that don't relate to anything else in the passage. These passages are not atrociously horrible writing, so, nope.)
The paragraph ends by explaining how these findings support one of the two hypotheses in ¶2 but not the other one.
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 15 Aug 2022, 20:47
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Hi GMATNinja,

you mentioned in your explanation,
"But when you refer back to the passage, was the second view (of early vertebrates as predators) "derived from the 1981 discovery"? Not quite. The second paragraph doesn't create a link between the view of predatory evolution and the 1981 discovery of conodont remains. The second paragraph doesn't even mention conodonts. That's why we eliminate (B) -- or at the very least, avoid falling in love with (B) right away"

Between B & E i choose B for the very reason of being specific about the sides. Here is my logic:
side 1: traditional view
side 2: view derived from discovery (conodonts). The discovery of conodonts did give way to the theory that teeth came before scales (para 3) and that the initial vertebrates were predators i.e. the second theory that's been contrasted (this was also the question asked in Q1).

para 2 does a side1 vs side 2. Please help me understand.
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 01 Sep 2022, 12:33
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Question 2


StringArgs
Hi GMATNinja,

you mentioned in your explanation,
"But when you refer back to the passage, was the second view (of early vertebrates as predators) "derived from the 1981 discovery"? Not quite. The second paragraph doesn't create a link between the view of predatory evolution and the 1981 discovery of conodont remains. The second paragraph doesn't even mention conodonts. That's why we eliminate (B) -- or at the very least, avoid falling in love with (B) right away"

Between B & E i choose B for the very reason of being specific about the sides. Here is my logic:
side 1: traditional view
side 2: view derived from discovery (conodonts). The discovery of conodonts did give way to the theory that teeth came before scales (para 3) and that the initial vertebrates were predators i.e. the second theory that's been contrasted (this was also the question asked in Q1).

para 2 does a side1 vs side 2. Please help me understand.
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P2 presents two hypotheses:

  • First hypothesis: how vertebrate skeletons "had traditionally been" regarded,
  • Second hypothesis: the viewpoint argued by "other" paleontologists.

Because the first hypothesis describes how skeletons HAD BEEN regarded, we know that this viewpoint existed BEFORE the 1981 discovery. And because the second viewpoint is presented as a counterpoint to this first view, we know that these two positions existed at the same time as one another.

So, the overall timeline goes something like:

  • Paleontologists take up two different positions regarding the vertebrate skeleton.
  • Then, there's a discovery in 1981.
  • This discovery supports one position over the other position.

So, it's not correct to say that the second view was "derived from" the 1981 discovery. The view was already out there, and then the 1981 discovery provided additional support for that view.

(B) is out, and (E) is the correct answer to question 2.

I hope that helps!
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 03 Dec 2022, 00:31
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GMATNinja - can you tell me how should have approached this question in the exam? You agree this was a tough passage/question set - so how one could have smartly gone about this during an actual exam and strategically thought about it? Wanted to really hear your views. Please respond. Thanks a ton.

GMATNinja

A closer look at Question #3


Rebekah
Can someone explain the third question? I got it right, but I spent almost 3 mins on this one. I had difficulties in locating where should I refer to answer this question.

It can be inferred that on the basis of the 1981 discovery of conodont remains, paleontologists could draw which of the following conclusions?
A The earliest vertebrates were sedentary suspension feeders.
B Ostracoderms were not the earliest vertebrates.
C Defensive armor preceded jaws among vertebrates.
D Paired eyes and adaptations for activity are definitive characteristics of vertebrates.
E Conodonts were unlikely to have been predators.

I found the discovery in p1 and p3. p1 just states that the discovery changes the views scientists hold about the development of vertebrate animals. p3 seems talk about the discovery(in a vague and subtle way, there is no obvious link between the discovery talked about in p1)

Cheers!
Your approach to this question was sound! It's a legitimately tough question, and difficult to answer without a clear read on the passage structure and process of elimination.

Quote:
It can be inferred that on the basis of the 1981 discovery of conodont remains, paleontologists could draw which of the following conclusions?
The only place this discovery is explicitly mentioned is in P1, but (as you know) this isn't a situation where there's some immediate factoid that we see directly connected to the year 1981. Instead, we see this big-picture statement:

    "However, since the 1981 discovery of fossils preserving not just the phosphatic elements but also other remains of the tiny soft-bodied animals (also called conodonts) that bore them, scientists' reconstructions of the animals' anatomy have had important implications for hypotheses concerning the development of the vertebrate skeleton."

This doesn't point us to something that happened in 1981. Instead, the significance of this line is why the author brings up this discovery: To call into question the existing hypotheses about why the vertebrate skeleton evolved.

OK, so let's think about this structurally. P1 tells us that the conodont discovery set up scientists (and us, the readers) to reconsider two hypotheses. P2 is all about presenting those hypotheses (which existed prior to the discovery and did not use conodonts as evidence), so we're not going to find the answer there.

But the purpose of P3 is to tell us that the hypothesis of aggressive evolution seems to be correct. And P3 delivers this statement based on the discovery of conodont remains:

    "The stiffening notochord...V-shaped muscle blocks...and posterior tail fins help to identify conodonts as among the most primitive of vertebrates. The lack of any mineralized structures...indicates that conodonts were more primitive than the armored jawless fishes such as the ostracoderms. It now appears that the hard parts that first evolved in the mouth of an animal improved its efficiency as a predator, and that aggression rather than protection was the driving force behind the origin of the vertebrate skeleton."

All right! The 1981 discovery triggered a new debate over the origin of the vertebrate AND placed conodonts as one of the earliest examples of vertebrate evolution being driven by aggression.

Let's start eliminating:
Quote:
A. The earliest vertebrates were sedentary suspension feeders.
Sedentary suspension feeders were mentioned in P2 as potential evidence for vertebrate evolution being defensive. It's a thing that was mentioned in the passage, but it's not a statement that we can infer on the basis of the 1981 discovery of conodont remains. Eliminate (A).

Quote:
B. Ostracoderms were not the earliest vertebrates.
This looks good! P3 specifically tells us that conodonts were vertebrates AND were more primitive than ostracoderms. This would imply that Ostracoderms were not the earliest vertebrates, because they were predated by conodonts. Let's keep choice (B) around and keep moving.

Quote:
C. Defensive armor preceded jaws among vertebrates.
Nope. Like choice (A), this is not a statement that we can infer on the basis of the 1981 discovery of conodont remains. It's a tempting choices, but we can eliminate (C) just like we eliminated (A).

Quote:
D. Paired eyes and adaptations for activity are definitive characteristics of vertebrates.
Like (A) and (C), this choice is tempting but it's not a fact that we can infer on the basis of the 1981 discovery. Eliminate (D).

Quote:
E. Conodonts were unlikely to have been predators.
Choice (E) is totally off the rails (off the spine?). The entire point of P3 is that conodonts were evolved to be predators. This is the opposite of what this choice says, so let's eliminate (E), too.

(B) is the only choice that directly answers the question and is backed up by our understanding of the 1981 discovery's importance.

I hope this helps clarify how to stay ahead of this question! Whether or not it increases your appreciation of conodonts is up to you. I do hear rumors that they taste like chicken... :tongue_opt2
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 20 Dec 2022, 10:57
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Question 3 (+ general RC thoughts)


kittle
GMATNinja - can you tell me how should have approached this question in the exam? You agree this was a tough passage/question set - so how one could have smartly gone about this during an actual exam and strategically thought about it? Wanted to really hear your views. Please respond. Thanks a ton.

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There are a couple of key things to keep in mind when approaching a tough question like this, and also GMAT RC in general.

First, when you're reading the passage as a whole, focus on structure. Why did the author include each paragraph? How does each paragraph connect to the other paragraphs? Answering these questions will help you see the skeleton of the passage, and know how the details fit together. For this question, knowing why the author included the 1981 discovery is key to making an inference about that discovery.

Second, be very careful with the exact language of the question. This question asks which conclusions can be inferred "on the basis of the 1981 discovery of conodont remains." That's a completely different question than something like, "which of the following can be inferred from the passage?" If you just react to the word "infer" without really seeing the rest of the question, then it's going to be impossible to answer this question accurately.

Third, know when to let go. There could be particular questions that are just too hard for you to complete within a reasonable amount of time. You pretty much always want to sink time into understanding the passage as a whole, carefully reading each question, and attempting to eliminate answer choices. If you're spinning your wheels on the answer choices, though, the best decision might be to guess and move on to the next question. Not a fun decision, but your time might be better spent elsewhere on the verbal section.

For much more on how to approach RC, check out this blob of videos.

I hope that helps a bit!
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 21 Dec 2023, 07:29
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How much time did it take for you to complete all 3 questions along with the reading of the passage?
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 28 Mar 2024, 07:04
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Got all of them incorrect, did not understand anything in the passage at all. This passage is way too challenging.­
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 09 Nov 2024, 16:30
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This passage crushed me when i first started GMAT. its been some time, so im giong to come back here and do a breakdown in first pass, under time, and see how i do.

para 1: conodonts once controversial, nat and func unknonw. new disc... not just the reamins of teeth, but the tiny soft animal iself? new hypothesis impac

para 2: def, later become pred with jaw, first vert, easy pray, trad argue ...? new term ostraderms, external skeleton,? first verts must be preds, some scientist? teeth primiative, verts were preds.
para3: traits that make it a vert, lack of mineralized struc, hard parts improved effieincy, aggression not protection for verts

According to the passage, the anatomical evidence provided by the preserved soft bodies of conodonts led scientists to conclude that

a. we know they are predators, but were they carniovres? keep
b. passage seems to directly state this? picked edit: its not talking about conodonts but rather gener verts
c. uhh the 3rd paragraph seems to support this as well. although suspension feeds doesnt really line with predator
d. last sentence of para 2 seems to directly state this too? pick?
e. this seems wrong since they didnt know the function or nature. so how could they have been right?

im going with D.
12 min!!

The second paragraph in the passage serves primarily to
a.no
b.?
c?
d? the last sentence seems to say this
e.doesnt seem like a debate? especially in the context of a new hypothesis. edit: i guess it is a debate?

guess d?

It can be inferred that on the basis of the 1981 discovery of conodont remains, paleontologists could draw which of the following conclusions?

a
b? line in para 3 says conodonts are among hte most primitive of verts. so....?
c.
d.
e. eliminate since the end says that they were predators,

not a clue? pick b



okay, so i got 2/3




it took me so long to get just the first question, how can i speed up?i got it right but i could not have got it in time.

i got 2 wrong, so im going to revise and try again before looking at the correct answer .

2. alright, i guess it does look like a debate, i picked E and that appears to be right.


incredibly hard passage.
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 19 Jun 2025, 02:11
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Hi GMATNinja,
Thank you for this breakdown. However, I am finding difficult to understand it and need help weighing B & D as choices.

B, i felt, has to do with dating fossils of conodonts & ostracoderms, which is probably possible independent of 1981 discoveries.
D, however, would rely on 1981 discoveries of "other remains" of tiny soft-bodied animals, which then leads to more accurate reconstructions.

shouldn't D objectively be correct over B? please help me see what I may be overlooking. Thanks!
GMATNinja

A closer look at Question #3


Rebekah
Can someone explain the third question? I got it right, but I spent almost 3 mins on this one. I had difficulties in locating where should I refer to answer this question.

It can be inferred that on the basis of the 1981 discovery of conodont remains, paleontologists could draw which of the following conclusions?
A The earliest vertebrates were sedentary suspension feeders.
B Ostracoderms were not the earliest vertebrates.
C Defensive armor preceded jaws among vertebrates.
D Paired eyes and adaptations for activity are definitive characteristics of vertebrates.
E Conodonts were unlikely to have been predators.

I found the discovery in p1 and p3. p1 just states that the discovery changes the views scientists hold about the development of vertebrate animals. p3 seems talk about the discovery(in a vague and subtle way, there is no obvious link between the discovery talked about in p1)

Cheers!
Your approach to this question was sound! It's a legitimately tough question, and difficult to answer without a clear read on the passage structure and process of elimination.

Quote:
It can be inferred that on the basis of the 1981 discovery of conodont remains, paleontologists could draw which of the following conclusions?
The only place this discovery is explicitly mentioned is in P1, but (as you know) this isn't a situation where there's some immediate factoid that we see directly connected to the year 1981. Instead, we see this big-picture statement:


"However, since the 1981 discovery of fossils preserving not just the phosphatic elements but also other remains of the tiny soft-bodied animals (also called conodonts) that bore them, scientists' reconstructions of the animals' anatomy have had important implications for hypotheses concerning the development of the vertebrate skeleton."

This doesn't point us to something that happened in 1981. Instead, the significance of this line is why the author brings up this discovery: To call into question the existing hypotheses about why the vertebrate skeleton evolved.

OK, so let's think about this structurally. P1 tells us that the conodont discovery set up scientists (and us, the readers) to reconsider two hypotheses. P2 is all about presenting those hypotheses (which existed prior to the discovery and did not use conodonts as evidence), so we're not going to find the answer there.

But the purpose of P3 is to tell us that the hypothesis of aggressive evolution seems to be correct. And P3 delivers this statement based on the discovery of conodont remains:


"The stiffening notochord...V-shaped muscle blocks...and posterior tail fins help to identify conodonts as among the most primitive of vertebrates. The lack of any mineralized structures...indicates that conodonts were more primitive than the armored jawless fishes such as the ostracoderms. It now appears that the hard parts that first evolved in the mouth of an animal improved its efficiency as a predator, and that aggression rather than protection was the driving force behind the origin of the vertebrate skeleton."

All right! The 1981 discovery triggered a new debate over the origin of the vertebrate AND placed conodonts as one of the earliest examples of vertebrate evolution being driven by aggression.

Let's start eliminating:
Quote:
A. The earliest vertebrates were sedentary suspension feeders.
Sedentary suspension feeders were mentioned in P2 as potential evidence for vertebrate evolution being defensive. It's a thing that was mentioned in the passage, but it's not a statement that we can infer on the basis of the 1981 discovery of conodont remains. Eliminate (A).

Quote:
B. Ostracoderms were not the earliest vertebrates.
This looks good! P3 specifically tells us that conodonts were vertebrates AND were more primitive than ostracoderms. This would imply that Ostracoderms were not the earliest vertebrates, because they were predated by conodonts. Let's keep choice (B) around and keep moving.

Quote:
C. Defensive armor preceded jaws among vertebrates.
Nope. Like choice (A), this is not a statement that we can infer on the basis of the 1981 discovery of conodont remains. It's a tempting choices, but we can eliminate (C) just like we eliminated (A).

Quote:
D. Paired eyes and adaptations for activity are definitive characteristics of vertebrates.
Like (A) and (C), this choice is tempting but it's not a fact that we can infer on the basis of the 1981 discovery. Eliminate (D).

Quote:
E. Conodonts were unlikely to have been predators.
Choice (E) is totally off the rails (off the spine?). The entire point of P3 is that conodonts were evolved to be predators. This is the opposite of what this choice says, so let's eliminate (E), too.

(B) is the only choice that directly answers the question and is backed up by our understanding of the 1981 discovery's importance.

I hope this helps clarify how to stay ahead of this question! Whether or not it increases your appreciation of conodonts is up to you. I do hear rumors that they taste like chicken... :tongue_opt2
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 15 Jul 2025, 07:54
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Question 3


aditsatt
Hi url=[https://gmatclub.com:443/forum/memberlist.php?mode=viewprofile&un=GMATNinja]GMATNinja[/url],
Thank you for this breakdown. However, I am finding difficult to understand it and need help weighing B & D as choices.

B, i felt, has to do with dating fossils of conodonts & ostracoderms, which is probably possible independent of 1981 discoveries.
D, however, would rely on 1981 discoveries of "other remains" of tiny soft-bodied animals, which then leads to more accurate reconstructions.

shouldn't D objectively be correct over B? please help me see what I may be overlooking. Thanks!
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Here's a relevant chunk of the passage again:

Quote:
...other paleontologists argued that many of the definitive characteristics of vertebrates, such as paired eyes and muscular and skeletal adaptations for active life, would not have evolved unless the first vertebrates were predatory.
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We're told that there was a LACK of mineralized structures in conodonts apart from the elements in the mouth. This suggests that conodonts did NOT have "skeletal" adaptations for active life. Conodonts were among the "most primitive" of vertebrates, so it would make sense if those "definitive characteristics" were the results of later evolution of vertebrates.

Also, those characteristics would not be considered "definitive characteristics of vertebrates" unless they were observed in many species of vertebrates. So even if conodonts did have those features, we would expect those features to appear in other vertebrate species. So paleontologists would have been able to draw the conclusion described in (D) without the 1981 discoveries.

And that makes sense given the context. Remember, conodonts were controversial BEFORE the 1981 discovery. Some paleontologists argued that the first vertebrates were predatory, and some argued that they were not. Those paleontologists likely agreed on the list of definitive characteristics of vertebrates, even though they disagreed on the evolution of those characteristics. The nature of the controversy suggests that definitive characteristics of vertebrates were known (and generally agreed upon) before the 1981 discovery.

(B) is a much better answer. Before 1981, paleontologists knew about ostracoderms, jawless vertebrates that existed from approximately 500 to 400 million years ago. Many paleontologists assumed that these ostracoderms were among the earliest vertebrates, which developed coverings of bony scales or plates. But the 1981 discovery allowed paleontologists to conclude that conodonts were vertebrates too. And since the conodont fossils are older than the ostracoderm fossils, they could conclude that ostracoderms were not the earliest vertebrates.
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 29 Jul 2025, 11:33
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AbdurRakib
Conodonts, the spiky phosphatic remains (bones and teeth composed of calcium phosphate) of tiny marine animals that probably appeared about 520 million years ago, were once among the most controversial of fossils. Both the nature of the organism to which the remains belonged and the function of the remains were unknown. However, since the 1981 discovery of fossils preserving not just the phosphatic elements but also other remains of the tiny soft-bodied animals (also called conodonts) that bore them, scientists' reconstructions of the animals' anatomy have had important implications for hypotheses concerning the development of the vertebrate skeleton.

The vertebrate skeleton had traditionally been regarded as a defensive development, champions of this view postulating that it was only with the much later evolution of jaws that vertebrates became predators. The first vertebrates, which were soft bodied, would have been easy prey for numerous invertebrate carnivores, especially if these early vertebrates were sedentary suspension feeders. Thus, traditionalists argued, these animals developed coverings of bony scales or plates, and teeth were secondary features, adapted from the protective bony scales. Indeed, external skeletons of this type are common among the well-known fossils of ostracoderm, jawless vertebrates that existed from approximately 500 to 400 million years ago. However, other paleontologists argued that many of the definitive characteristics of vertebrates, such as paired eyes and muscular and skeletal adaptations for active life, would not have evolved unless the first vertebrates were predatory. Teeth were more primitive than external armor according to this view, and the earliest vertebrates were predators.

The stiffening notochord along the back of the body, V-shaped muscle blocks along the sides, and posterior tail fins help to identify conodonts as among the most primitive of vertebrates. The lack of any mineralized structures apart from the elements in the mouth indicates that conodonts were more primitive than the armored jawless fishes such as the ostracoderms. It now appears that the hard parts that first evolved in the mouth of an animal improved its efficiency as a predator, and that aggression rather than protection was the driving force behind the origin of the vertebrate skeleton.

1. According to the passage, the anatomical evidence provided by the preserved soft bodies of conodonts led scientists to conclude that

A. conodonts had actually been invertebrate carnivores
B. conodonts' teeth were adapted from protective bony scales
C. conodonts were primitive vertebrate suspension feeders
D. primitive vertebrates with teeth appeared earlier than armored vertebrates
E. scientists' original observations concerning the phosphatic remains of conodonts were essentially correct



2. The second paragraph in the passage serves primarily to

A. outline the significance of the 1981 discovery of conodont remains to the debate concerning the development of the vertebrate skeleton
B. contrast the traditional view of the development of the vertebrate skeleton with a view derived from the 1981 discovery of conodont remains
C. contrast the characteristics of the ostracoderms with the characteristics of earlier soft-bodied vertebrates
D. explain the importance of the development of teeth among the earliest vertebrate predators
E. present the two sides of the debate concerning the development of the vertebrate skeleton



3. It can be inferred that on the basis of the 1981 discovery of conodont remains, paleontologists could draw which of the following conclusions?

A. The earliest vertebrates were sedentary suspension feeders.
B. Ostracoderms were not the earliest vertebrates.
C. Defensive armor preceded jaws among vertebrates.
D. Paired eyes and adaptations for activity are definitive characteristics of vertebrates.
E. Conodonts were unlikely to have been predators.


RC00073-01
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Essentially, this is what the passage says sans the terminology and details:

Para1: Fossil of Conodonts (bones and teeth) were controversial before 1981. After that, fossils of other parts were also found and have important implications for the hypotheses regarding how vertebrate skeleton evolved.

Para 2: Traditional view - vertebrate skeleton were a defensive development, not predatory. So teeth evolved later. e.g. Ostracoderm was a jawless vertebrate with external skeleton.

Other paleontologists' view - many characteristics of vertebrates, such as paired eyes would not have evolved unless the first vertebrates were predatory. Teeth came first (for predatory purposes) and external armor later.

Para 3: Conodonts were likely among the most primitive of vertebrates. (they came before armored jawless fishes such as the ostracoderms). It now appears that the hard parts that first evolved in the mouth of an animal improved its efficiency as a predator, and that aggression rather than protection was the driving force behind the origin of the vertebrate skeleton.


Question 1.


1. According to the passage, the anatomical evidence provided by the preserved soft bodies of conodonts led scientists to conclude that

A. conodonts had actually been invertebrate carnivores
B. conodonts' teeth were adapted from protective bony scales
C. conodonts were primitive vertebrate suspension feeders
D. primitive vertebrates with teeth appeared earlier than armored vertebrates
E. scientists' original observations concerning the phosphatic remains of conodonts were essentially correct

Look at the last paragraph.
It says that conodonts preceded ostracoderms and their new fossils suggest that the hard parts that first evolved in the mouth of an animal improved its efficiency as a predator, and that aggression rather than protection was the driving force behind the origin of the vertebrate skeleton. So teeth appeared before armor.

Answer (D)


Question 2.


2. The second paragraph in the passage serves primarily to

A. outline the significance of the 1981 discovery of conodont remains to the debate concerning the development of the vertebrate skeleton
B. contrast the traditional view of the development of the vertebrate skeleton with a view derived from the 1981 discovery of conodont remains
C. contrast the characteristics of the ostracoderms with the characteristics of earlier soft-bodied vertebrates
D. explain the importance of the development of teeth among the earliest vertebrate predators
E. present the two sides of the debate concerning the development of the vertebrate skeleton

Paragraph 2 only talks about what the traditionalists thought and what other paleontologists' thought - it just gives the two sides of the debate.
Hence option (E) works.

Option (A): outline the significance of the 1981 discovery of conodont remains to the debate concerning the development of the vertebrate skeleton

The second paragraph does not even mention the 1981 discovery of conodont remains. It does not talk about its significance at all.

Option (B): contrast the traditional view of the development of the vertebrate skeleton with a view derived from the 1981 discovery of conodont remains

It does not contrast the traditional view with a view derived from the 1981 discovery of conodont remains. The 1981 discovery has no relevance in the second para. The author introduces it in the first para and then brings it into the picture in the 3rd para. In 2nd para, she just presents the two contrasting theories.

Answer (E)


Question 3.

3. It can be inferred that on the basis of the 1981 discovery of conodont remains, paleontologists could draw which of the following conclusions?

A. The earliest vertebrates were sedentary suspension feeders.
B. Ostracoderms were not the earliest vertebrates.
C. Defensive armor preceded jaws among vertebrates.
D. Paired eyes and adaptations for activity are definitive characteristics of vertebrates.
E. Conodonts were unlikely to have been predators.

Third paragraph: The stiffening notochord along the back of the body, V-shaped muscle blocks along the sides, and posterior tail fins help to identify conodonts as among the most primitive of vertebrates. The lack of any mineralized structures apart from the elements in the mouth indicates that conodonts were more primitive than the armored jawless fishes such as the ostracoderms.

Hence the 1981 discovery helped paleontologists conclude that Ostracoderms were not the earliest vertebrates.

Answer (B)
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 08 Oct 2025, 09:20
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This might be a silly question, but are traditionalists are NOT the scientists referred to in this question (or are they generally NOT referred to as scientists)? I was confused because para 1 was speaking about "scientists reconstructions..." made following 1981 discoveries, and then P2 goes on to talk about traditionalists and then OTHER paleontologists. So I thought the natural transition from P1 to P2 is to continue talking about the scientists (aka the traditionalist, potentially older scientists?). And the paleontologists are the newer scientists?
GMATNinja


This is a sneaky one... indeed, the traditionalists would agree with choice (B). But the anatomical evidence provided by the preserved soft bodies of conodonts cause scientists to question the traditional views:


So now we have to consider the new evidence, which is NOT phosphatic (i.e. not the bones and teeth). This new evidence includes paired eyes, muscular adaptations for active life, the stiffening notochord along the back of the body, V-shaped muscle blocks along the sides, and posterior tail fins. The evidence from these non-phosphatic remains suggests that conodonts actually came BEFORE the armored jawless fishes such as the ostracoderms.

In other words, in light of the new evidence, other paleontologists argued that "teeth were more primitive than external armor." This new theory contradicts that of the traditionalists and the statement in choice (B). Thus, (B) should be eliminated.
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Conodonts, the spiky phosphatic remains (bones and teeth composed of 14 Oct 2025, 08:10
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Question 1


soniasw16
This might be a silly question, but are traditionalists are NOT the scientists referred to in this question (or are they generally NOT referred to as scientists)? I was confused because para 1 was speaking about "scientists reconstructions..." made following 1981 discoveries, and then P2 goes on to talk about traditionalists and then OTHER paleontologists. So I thought the natural transition from P1 to P2 is to continue talking about the scientists (aka the traditionalist, potentially older scientists?). And the paleontologists are the newer scientists?
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The organization of the passage is indeed a bit confusing. The first paragraph refers to the 1981 discovery. Then in the second paragraph we get some details about how the vertebrate skeleton had traditionally been regarded (as a defensive development). As explained in this post, the verb tense is a hint that this traditional view is based on the evidence that existed BEFORE the 1981 discovery.

We're told in the first sentence that the remains "were once among the most controversial of fossils." This implies that not all scientists agreed with the traditional view, even before the 1981 discovery. The "other paleontologists" were the ones who argued against the traditionalists.

The passages implies that the fossils became much less controversial after the 1981 discovery, since that discovery provided strong evidence against the traditional view. That means that there were probably plenty of scientists who abandoned the traditional view.

Sure, there were likely some scientists who continued to believe in the traditional view in spite of the new evidence, but it sounds as though scientists were generally in agreement after the 1981 evidence. Question 1 is asking what the scientists generally agreed on in light of that new evidence.

I hope that helps!
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