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Author Topic: Dinosaurs and other prehistoric creatures  (Read 196429 times)

Vertigo
Apr 04, 2014, 08:49:01 AM
Reply #975 on: Apr 04, 2014, 08:49:01 AM
Q
Ahh, goddamnit. I spent half the evening whipping up a family tree/timeline of my own.
Anyway, here it is...



(Full sized version here)

The timeline represents the presence of a family down to the certainty of an age (eg. Campanian, Maastrichtian), rather than an exact date. Some of these ages are longer than others, and a group didn't necessarily survive throughout the entire age, or spring into existence at the start of the age. For example, it seems Herrerasaurids disappeared very quickly into the Norian, but it's a long-arse age so they have a long-arse line.
Main reason I'm doing this is because date estimates can be inaccurate, but it's usually possible to tell which age/geological strata that a fossil comes from.

Dotted lines represent possible evidence of the family being around at the indicated date (teeth, a couple of misc bones, or a hard-to-place genus - the kind of evidence which may not be accurate).

Cross-hatched lines represent times during which we can infer the presence of a group of animals, based on their evolutionary relationships, but haven't found evidence to date. Examples include basal dinosaurs, allosaurs, thyreophorans and pachycephalosaurs.

Notes:
I've represented a number of theropod, sauropod and ornithischian groups as as a diagonal line - for each, there's an enormous cluster of short-lived families which formed a linear progression. For example, saurischians begat theropods, which begat neotheropods, which begat tetanurans, which begat coelurosaurs, which begat maniraptorans.
I haven't bothered with an exact timeline for them, because it's a complex subject, and they tend to be quickly replaced by their more specialised cousins.

The allosaur family is generally called "Carnosauria", but it's a confusing term and personally I don't use it.

Apologies for the messiness! It's my first try at a cladogram, and it's a bit tricky to make it work with a time reference.

« Last Edit: Apr 04, 2014, 08:58:53 AM by Vertigo »


Vertigo
Apr 04, 2014, 08:42:36 PM
Reply #977 on: Apr 04, 2014, 08:42:36 PM
Q
He fits into my tree comfortably (surprising behaviour for a sauropod). It's worth noting that true sauropods were rare throughout the Triassic, they only started widely replacing the prosauropods during the next period.

Also, in Europe, non-diplodocoid or macronarian sauropods survived a little longer than shown on the chart - sometime shortly before or after the end of the Jurassic.


DoomRulz
Apr 07, 2014, 02:58:45 AM
Reply #978 on: Apr 07, 2014, 02:58:45 AM
Q
According to that piece, the term prosauropod doesn't exist anymore. Personally, I prefer it to "sauropodomorphs", even though that one's been around since I was a wee lad.

Some random dino stuff for y'all:
http://www.sciencedaily.com/releases/2013/04/130408123502.htm
http://io9.com/another-fine-feathered-friend-from-the-cretaceous-1558700065
http://io9.com/ready-this-3d-model-reconstructs-a-110-million-year-old-1558469828


Vertigo
Apr 07, 2014, 11:03:44 PM
Reply #979 on: Apr 07, 2014, 11:03:44 PM
Q
Yup, 'prosauropod' is more of an informal term now. I prefer it too, and downright refuse to stop using it.

I've been waiting for ages for the new descriptions of Utahraptor, good to see a preview. Rectangular skull and downward-curving jaw remind me of Dromaeosaurus, short legs remind me of Achillobator.


DoomRulz
Apr 08, 2014, 02:37:44 AM
Reply #980 on: Apr 08, 2014, 02:37:44 AM
Q
Scott Hartman is a brilliant artist. I wish I could understand the process behind his work. It's as if the guy is in tune with skeletons just by looking at fragments.


judge death
Apr 08, 2014, 08:16:50 PM
Reply #981 on: Apr 08, 2014, 08:16:50 PM
Q
Vertigo: That species/animal tree is great, easy to understand and easy to use, is it okay if I download it? :) Shall try to learn it so I know it even if I sleep xD


Vertigo
Apr 09, 2014, 10:29:54 AM
Reply #982 on: Apr 09, 2014, 10:29:54 AM
Q
Yeah please do! Glad you find it so easy to read, it looks like a mess to me.  ;D

Just a few things I'd like to clarify about it though:

-Despite ornithischians only appearing later (and becoming common much later), they're probably a more basal offshoot than saurischians (theropods and sauropodomorphs). They lack the air sac breathing system of their cousins; some very advanced ornithischians seem to have developed a mammal-like diaphragm-based system instead.

-Although herrerasaurids are some of the earliest dinosaurs ever discovered (and the earliest fragmentary dinosaur remains - from the Anisian - are thought to be of herrerasaurid origin), other groups are not descended from them. Herreras must have become highly specialised extremely quickly after the evolution of the first dinosaurs, and are so unusual that it's often been argued whether they are in fact dinosaurs.

-There are a few controversial theories around the connection between dilophosaurids and ceratosaurs. It's been proposed that the ceratos may have evolved from dilos. It's also been proposed that dilos may not be so closely related to coelophysoids (then again, others have suggested that dilos are so similar to coelos that they shouldn't be classed as a separate group!).
I quite like the idea of an evolutionary line between coelos, dilos and ceratos, as it would mean the coelophysoid lineage lasted throughout the Mesozoic. This is not a majority opinion though.

-Coelurosaurs didn't evolve from allosaurs, I had a bit of trouble drawing that part of the graph. They both evolved from avetheropods, apparently around the same time.

-The maniraptoran lineage is a mess. We have very little evidence for what basal maniraptorans looked like, and it seems there are huge gaps in the fossil record. Therizinosaurs and oviraptorosaurs are descended from more basal creatures than paravians, yet we have no evidence of such animals existing for tens of millions of years before we start finding the earliest theris and ovis.
You'll find similar gaps throughout the tree. Some spans of time just have very few fossil beds associated with them - the early Triassic, Jurassic, Cretaceous and early Late Cretaceous are all particularly poor.

-There's a bit of blurring between dromaeosaurids and paravians/protobirds - some researchers consider Archaeopteryx a dromaeosaurid. I don't, but I do think it's close to their evolutionary root (which probably makes dromies secondarily flightless, like today's ostrich).

-With the sauropod line, brachiosaurids and titanosaurs are much closer-related than diplodocoids. However, all three evolved around the same time, and other sauropod groups disappeared quickly after. In my opinion this has something to do with a possible ice age during the late Jurassic.

-It's possible that marginocephalians (ceratopsians and pachycephalosaurs) may have evolved from heterodontosaurids. This is a highly minority view though, and based mainly on similar tooth shape. As crocodylians and spinosaurids prove, tooth similarity has a high likelihood of evolving independently.

« Last Edit: Apr 09, 2014, 01:19:27 PM by Vertigo »

DoomRulz
Apr 09, 2014, 11:25:48 AM
Reply #983 on: Apr 09, 2014, 11:25:48 AM
Q
Aren't titanosaurids a sub-group of the diplodocoid family? I'm pretty sure Diplodocus is related to Argentinosaurus and other giants.

« Last Edit: Apr 25, 2014, 11:39:26 AM by DoomRulz »

Vertigo
Apr 09, 2014, 12:46:57 PM
Reply #984 on: Apr 09, 2014, 12:46:57 PM
Q
That was the going theory at one point, but not anymore. The currently prevailing tree goes like this:

Eusauropoda (eg. Cetiosaurus, Mamenchisaurus)
|
Neosauropoda (classification group only, no basal members assigned)
|                         |
Diplodocoidea    Macronaria (eg. Camarasaurus)
                          |                      |
                       Brachiosaurids    Titanosaurs


DoomRulz
Apr 09, 2014, 01:16:24 PM
Reply #985 on: Apr 09, 2014, 01:16:24 PM
Q
Titanosauria is part of Macronaria? I want to be sure I'm reading that correctly.


Vertigo
Apr 09, 2014, 01:20:54 PM
Reply #986 on: Apr 09, 2014, 01:20:54 PM
Q
Yup.


DoomRulz
Apr 09, 2014, 01:29:19 PM
Reply #987 on: Apr 09, 2014, 01:29:19 PM
Q
What's the distinguishing feature separating Diplodocoidea from Macronaria?


Vertigo
Apr 09, 2014, 07:48:38 PM
Reply #988 on: Apr 09, 2014, 07:48:38 PM
Q
Macronarians have a more upright upper-body/neck posture, longer hands, bigger nostrils, more rounded heads, and in most species their tails don't tend to be so super-extended and whip-like.

They're all very closely related though, and you do see a few diplodocoid features appearing in titanosaurs.


Jegeren
Apr 25, 2014, 03:19:02 AM
Reply #989 on: Apr 25, 2014, 03:19:02 AM
Q
How can you not love dinosaurs? I have been a fan of them since my single digits and always will be. Since they were obviously extinct, hearing brand new things about them every year is always awesome. Hard to pin an exact favorite as there are so many great specimens that existed.


 

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