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To clarify at first, I have very little knowledge in biology and paleontology so there might be very obvious things I overlook.

According to the evolution theory, there must be a graduate evolution process over millions of years such that the skull and the horns of the Triceratops gradually appear over time. However why there is no fossil record of such "intermediate" form between Triceratops and earlier dinosaurs? I mean there must be some intermediate dinosaurs that has a short skull that almost looks like a small mountain on the neck and very short horns. However based on my internet search I can't find any information that confirms existence of such intermediate dinosaurs.

I just want to know is there any such evidence of graduate evolution among paleontologists or the evolution of dinosaurs is still much based on speculation (without firm evidence)?

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    $\begingroup$ Note btw that it is a standard layman misrepresentation of evolutionary processes to think that evolution must necessarily be very slow. This is not necessarily true. $\endgroup$ – Remi.b Aug 23 '17 at 14:31
  • $\begingroup$ @Remi.b Are you referring to some kind of 'evolution in bursts'? I feel I heard about it, not sure where! $\endgroup$ – Harry Weasley Oct 22 '17 at 17:10
  • $\begingroup$ @HarryWeasley I started to answer your comment and realized it would deserve its own post. So, I opened a post asking your question (and directly answered it) here. $\endgroup$ – Remi.b Oct 22 '17 at 19:04
  • $\begingroup$ Very related: Where are the evolutionary “inbetweeners”?. $\endgroup$ – Remi.b Jun 29 '18 at 18:21
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Yes, there are many early examples of ceratopsians before Triceratops. The oldest clear member of the lineage is Liaoceratops: "the oldest ceratopsian ever found ... was about the size of a large dog. It had a blunt beak and a dainty neck frill. ... Liaoceratops was a puny forebear of the feisty Triceratops. Size, horns and spectacular frills came later in ceratopsian evolution." Here's a reconstruction:

enter image description here

Protoceratops is very well known, and is a pretty obvious intermediate between famous ceratopsians like Triceratops and early ones like Liaceratops:

enter image description here

This cladogram shows a number of steps in ceratopsian evolution (right side of the diagram):

enter image description here

Note the steps it describes: Starting with early forms that have a vaguely frill-like structure, we see added: Rostral bone with "horns" that are barely visible; Frill, with jugal "horns"; Enlarged frill and skull; Postorbital horns; Nasal horn.

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  • $\begingroup$ Thank you so much. This is exactly what I am looking for. $\endgroup$ – cr001 Aug 23 '17 at 21:03
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    $\begingroup$ A quick look a the sheer variety of ceratopsians is helpful. Even right at the top of the tree there is a lot of variation. 66.media.tumblr.com/35e87e230a6c1589aef6c474d90ed9c3/… $\endgroup$ – John Aug 15 at 18:52
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If you are looking to a more recent evolution of Triceratops you can follow the cladogram to the subfamily Chasmosaurinae and then to the tribe Triceratopsini. You'll find there Eotriceratops, which looks very much like a bigger Triceratops and might has been his direct ancestor, as it lived 68 MYA.

The rest of your question is more philosophical than informative and echos "the chicken and the egg" paradox, or "when exactly an animal evolves into a distinct species?"

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