Dinosaurs eating meat are called carnivores: Grammar Questions I Couldn't Answer

(Grammar Questions I Couldn't Answer)

Recently I was looking at the test for Impact 4 Unit 6.  The test instructions were: “Write the sentences again with a reduced relative clause. Tick the sentence if it does not need to be changed.”  

One sentence was: “Dinosaurs that ate meat are called carnivores.”

According to the answer key for the test, this sentence could not be rewritten as a reduced relative clause, and the correct answer was to just leave the sentence as it was.

However, according to the information contained in the student's workbook, (which is where the Impact textbooks hide their grammar explanations), it says (p.62), "If a relative pronoun is followed directly by a verb, it cannot be left out.  Sometimes we can use the verb in the -ing form or past participle instead: The scientists who study / studying ..."

This grammar point was fresh in my mind because I had just recently been teaching the same grammar point from Reflect Listening & Speaking 5 which also taught that if the relative pronoun is being used as the subject, it could be reduced by omitting the relative pronoun and changing the verb to the -ing form.  Here are some examples from the Reflect Listening & Speaking 5 book:

"The number of people who used public baths increased." becomes "The number of people using public baths increased."

"Almost half the people who saw the online advertisement clicked it" becomes "Almost half the people seeing the online advertisement clicked it."

So, by those rules, it should be possible to reduce "Dinosaurs that ate meat are called carnivores" to "Dinosaurs eating meat are called carnivores".  Except... "Dinosaurs eating meat are called carnivores" just doesn't sound right.  I can't put my finger on it, but there's something about that sentence that just doesn't sound right.

I discussed this sentence with a colleague.  She agreed with me that "Dinosaurs eating meat are called carnivores" didn't sound natural, but we couldn't figure out why.  She suggested that maybe it was because "Dinosaurs that ate meat are called carnivores" was in the past tense, so that is why we couldn't reduce it to the -ing verb.  I pointed to the two examples from the Reflect book (that I've quoted above) to illustrate that past tense verbs can also be reduced to -ing form: "The number of people who used public baths increased." and "Almost half the people who saw the online advertisement clicked it."  

(Actually my colleague wasn't entirely sure that sentences like  "Almost half the people seeing the online advertisement clicked it" sounded entirely natural to her, even though I pointed out to her that the Reflect book gave this as a correct sentence.  So we had some slight disagreement on our native speaker intuition.)

In the end, we never did figure it out.

I posted the question on our group chat at work to see if anyone else had any ideas.  Some people had various suggestions, but we never did reach a consensus.  I'll duplicate that chat below.  (All names are replaced by "X___")

I posted:

Okay, is everybody ready to put their heads together for a grammar question?  X___ and I were looking at this sentence from the Pre-Advanced B unit 6 quiz.  The instructions are "Write the sentences again with a reduced relative clause. Tick the sentence if it does not need to be changed."  Number 12 is "Dinosaurs that ate meat are called carnivores".  According to the answer key, this sentence cannot be re-rewritten as a reduced relative clause.

But... according to the information in the students' workbook (p.62), it says, "If a relative pronoun is followed directly by a verb, it cannot be left out.  Sometimes we can use the verb in the -ing form or past participle instead: The scientists who study / studying ..."

So, can the sentence be re-written as "Dinosaurs eating meat are called carnivores."  X___ and I both agreed that it didn't sound right.  But why?  What rule is being broken?

Is it because it's in the past tense?  Maybe.  But, looking in or other textbooks, in the Reflect series--Reflect 5 Listening and Speaking, p. 62--they give several examples of reduced relative clauses in the past tense  (e.g. "The number of people who used public baths increased"... "the number of people using public baths increased")

So is  "Dinosaurs eating meat are called carnivores" actually wrong?

X___ posted:

Is it about defining and non defining? (Haven’t delved deep into thinking about this, but just based on these examples)

I replied:

I'd been thinking about defining non-defining, but I can't seem to find a consistent pattern.  "Dinosaurs that eat meat" is, I think, defining.  But if we change it to a non-defining example, like "Simon, who eats meat, teaches English", then we would get "Simon eating meat teaches English"--which to me at least still seems a bit off.

X___ posted:

You mentioned past tense, and for me that is a part of reason it feels wrong. In the other example referring to the past, you have 'increased' to place it in the past. However, in the dinos sentence it really sounds like dinos are still around eating meat. 

I replied:

I wonder... I'm looking at other examples now from the textbook.  Reflect 5 Listening and Speaking, p. 62 also has "Almost half the people who saw the online advertisement clicked it", which they say can be reduced to "Almost half the people seeing the online advertisement clicked it".  But in this case as well, we still have the word "clicked" to indicate that it's in the past.  So is that they key?  We need another past tense verb somewhere in the sentence to make it sound right?

What about if we put it into the present tense and say "animals eating meat are called carnivores".  Does that fix the problem, or does it still sound a little off?  I want to say that it still sounds a bit off to me.

...Also, what if we changed "are called" to "were called"--i.e. "Dinosaurs eating meat were called Carnivores".  Does that fix it?

X___ replied:

On the last sentence, I would say no, as we call them carnivores now. 

 

Animals eating meat are called carnivores sits better with me, but it isn't how I would ever say it myself....

X___ posted:

Yeah I think it felt weird because we know dinosaurs are extinct (or are they?) But still the animals eating meat feels a bit off too because I start to think , well when they are not eating what are they called. So maybe it's the defining aspect? 

...and there you have it.  In the end, no clear consensus was ever reached.

I pulled down a couple grammar reference books from my shelf (The Grammar Book: An ESL/EFL Teacher's Course by Marianne Celce-Murcia and Diane Larsen-Freeman and Practical English Usage by Michael Swan) and did a quick search through those books for the rules on reducing relative clauses.  I didn't find anything.  (Possibly it's in those books, and I just missed it.  I don't know.)  So I'm going to give up for now.  If anyone knows the rule, please let me know in the comments.