Freethought & Rationalism Archive

tgamble · 12-08-2002, 04:50 PM

Posted on another board:

Quote:

Karl, I'll even settle for something dead. Molly, my daughter, pointed out that cats and dogs might have a common ancestor. Let's see if we can get a good discussion going here and just stick to the facts.
Molly brought our terrier and our car over and showed me several common features (body shape, padded feet, short tail, carnivorous teeth, similar posture, etc.) Is there a reasonable common ancestor for these two groups? I'll even admit that all of the great cats (lions tigers, etc. ) and small cats (housecats, ocelots, etc.) might share a common ancestor. MIGHT. But how would you bridge the gap between even admittedly similar species like a cat and a dog?

Like I said, even a dead, fossilized beast should suffice.

In Christ

David

Sounds hopeful but I'm unable to find any information on what the common ancestor of dogs and cats would be. Any help would be useful.

Liquidrage · 12-08-2002, 05:13 PM

From what I can find, the common ancestor of both cats and dogs is said to be a Miacis. It was a weasellike creature of 50 MYA.
You can search for Miacis for more related information.

This link has a lot of good information.
<a href="http://www.idir.net/~wolf2dog/wayne2.htm" target="_blank">Molecular evolution of the dog family</a>

Quote:

The order Carnivora includes the cat, hyena, bear, weasel, seal, mongoose, civet and dog families (Fig. 2). All have ancient origins some 40-60 million years ago and thus their relationships can be studied by comparing the sequences at single-copy genes that have only a modest rate of sequence evolution

This link focuses on the wolf, but it states:
<a href="http://www.ualberta.ca/~jzgurski/evolution.html" target="_blank">Evolution of Wolves</a>

Quote:

Dogs, ungulates (hoofed mammals), cats, bears, weasels, raccoons, civets and hyenas all share a common ancestor. Thus, the wolf and the animals it preys upon (the ungulates) evolved from a common ancestor from which they both inherited their intelligence and their ability to run swiftly for long periods of time. This common ancestor lived about a hundred million years ago. Most mammalian orders then differentiated during the Paleocene epoch (65 to 55 million years ago) and can be recognized from Eocene (55 - 33 million year old) fossils

Undercurrent · 12-08-2002, 05:18 PM

from <a href="http://www.talkorigins.org/faqs/faq-transitional/part2a.html" target="_blank">talk origins</a>

Quote:

Cimolestes (late Cretaceous) -- This creodont (?) lost the last molar & then later enlarged the last upper premolar and first lower molar. (In modern carnivores, these two teeth are very enlarged to be the wickedly shearing carnassial teeth, the hallmark of carnivores.) Still unfused feet & unossified bulla. This genus is probably ancestral to two later lines of Eocene carnivores called "miacoids". Miacoids were relatively unspecialized meat-eaters that seem to have split into a "viverravid" line (with cat/civet/hyena traits) and a "miacid" line (with dog/bear/weasel traits). These two lines may possibly have arisen from these slightly different species of Cimolestes:

m.

Doubting Didymus · 12-08-2002, 05:18 PM

It used to be thought that Creodonts were ancestral to carnivoria (the group that includes dogs and cats, but also bears, seals etc).

This is one, from the early tertiary:

It's about the size of a mongoose, apparently.

Nowadays the creodonts are though to be an extinct branch that lived alongside the real carnivoria ancestors.

Jesse · 12-08-2002, 06:51 PM

The talkorigins <a href="http://www.talkorigins.org/faqs/faq-transitional.html" target="_blank">transitional fossil FAQ</a> talks about early members of the Order Carnivora (which includes both dogs and cats):

Quote:

Carnivores

* Creodonts -- early placental mammals with minor but interestingly carnivore-like changes in the molars and premolars. Had a carnivore- like shearing zone in the teeth, though the zone moved throughout life instead of staying in particular teeth. Also had a carnivore- like bony sheet in the brain dividing cerebrum & cerebellum, details of ankle. Closely related to & possibly ancestral to carnivores. The origin of the creodonts is unclear. They probably were derived from condylarths.
* Cimolestes (late Cretaceous) -- This creodont (?) lost the last molar & then later enlarged the last upper premolar and first lower molar. (In modern carnivores, these two teeth are very enlarged to be the wickedly shearing carnassial teeth, the hallmark of carnivores.) Still unfused feet & unossified bulla. This genus is probably ancestral to two later lines of Eocene carnivores called "miacoids". Miacoids were relatively unspecialized meat-eaters that seem to have split into a "viverravid" line (with cat/civet/hyena traits) and a "miacid" line (with dog/bear/weasel traits). These two lines may possibly have arisen from these slightly different species of Cimolestes:
* Cimolestes incisus & Cimolestes cerberoides (Cretaceous) -- These are two species that lost their third molar, and may have given rise to the viverravid line of miacoids (see Hunt & Tedford, in Szalay et al., 1993).
* Cimolestes sp. (Paleocene) -- A later, as yet unnamed species that has very miacid-like teeth.
* Simpsonictis tenuis (mid-Paleocene) -- A very early viverravid. The upper carnassial was large; the lower carnassial was of variable size in different individuals.
* Paroodectes, Vulpavus (early Eocene) -- Early miacids. Enlarged carnassials now specialized for shearing. Still had unfused foot bones, short limbs, plantigrade feet, unossified bulla.
GAP: few miacoid skulls are known from the rest of the Eocene -- a real pity because for early carnivore relationships, skulls (particularly the skull floor and ear capsule) are more useful than teeth. There are some later skulls from the early Oligocene, which are already distinguishable as canids, viverrids, mustelids, & felids (a dog-like face, a cat-like face, and so on). Luckily some new well-preserved miacoid fossils have just been found in the last few years (mentioned in Szalay et al., 1993). They are still being studied and will probably clarify exactly which miacoids gave rise to which carnivores. Meanwhile, analysis of teeth has revealed at least one ancestor:

* Viverravus sicarius (mid-Eocene) -- Hunt & Tedford (in Szalay et al., 1993) think this viverravid may be the ancestral aeluroid. It has teeth & skeletal traits similar to the first known Oligocene aeluroids (undifferentiated cat/civet/hyenas).
From the Oligocene onward, the main carnivore lineages continued to diverge.

After that, they discuss some examples of early fossils from the dog lineage and the cat lineage.

Some other pages which might be helpful:

<a href="http://www.primenet.com/~brendel/carniv.html" target="_blank">Order Carnivora</a>

<a href="http://animaldiversity.ummz.umich.edu/chordata/mammalia/carnivora.html" target="_blank">Another page on Order Carnivora</a>

<a href="http://www.ucmp.berkeley.edu/mammal/carnivora/carnivorafr.html" target="_blank">Carnivora: Fossil Record</a>

<a href="http://www.geocities.com/CapeCanaveral/Hall/1636/synapsida/mammalia/carnivora.html" target="_blank">Carnivora</a>

Also, <a href="http://www.marwell.org.uk/feature-fossa.htm" target="_blank">here</a> is an interesting page on an animal that may be intermediate between cats and civets, although the similarities to cats may just be convergent evolution:

Quote:

The fossa is one of Madagascar�s eight native carnivores. However, the fossa is unique in being the sole representative of its genus, Cryptoprocta, which puts it partway between the cats and civets. Although they have retractile claws and similar dentition to true cats, one theory is that they are descended from civet ancestors, but acquired feline characteristics through convergent evolution.

It does kind of look like an almost-cat though:

[ December 08, 2002: Message edited by: Jesse ]

RufusAtticus · 12-08-2002, 07:09 PM

Remember that all these fossils are not necessarily the common ancestor species between cats and dogs, but rather closely related and probably representative of the actual one.

Doubting Didymus · 12-08-2002, 07:21 PM

Quote:

Remember that all these fossils are not necessarily the common ancestor species between cats and dogs, but rather closely related and probably representative of the actual one.

Particularly in the case of my creodont, which was a separate branch.

You could go back to the common ancestor of all eutherians, and be fairly confident that you have a definite common ancestor of cats and dogs. But I suppose you could go back to the ancestral chordate and say the same thing.

Obviously, by his comments about 'even accepting a dead common ancestor' shows that this creationist will not understand the concept anyway.

lpetrich · 12-09-2002, 03:57 AM

If one wants to be precise, the ancestor desired is

Last Common Ancestor

or

Youngest Common Ancestor

And as mentioned hear, it's likely some miacid or miacid-like Eocene carnivore.

Doubting Didymus · 12-09-2002, 01:49 PM

Quote:

Originally posted by lpetrich:
If one wants to be precise, the ancestor desired is

Last Common Ancestor or Youngest Common Ancestor

Speaking of that, what we have been looking for is the last common ancestor of all carnivoria. Is there an even more recent ancestor at the cat/dog divergence?

lpetrich · 12-09-2002, 02:46 PM

Quote:

Originally posted by Doubting Didymus:

Speaking of that, what we have been looking for is the last common ancestor of all carnivoria. Is there an even more recent ancestor at the cat/dog divergence?

The Last Common Ancestor of dogs and cats is also the Last Common Ancestor of all living carnivorans. The split between doglike and catlike carnivores is the first split in the family tree of all known living ones. Here's <a href="http://www.nhm.ac.uk/palaeontology/a&ss/nm/role.pdf" target="_blank">a very detailed paper on the carnivore family tree</a>. It goes into a lot of detail, and it is rather technical, but if that interests you, please feel free to check it out.

That paper exclusively discusses evidence from wild carnivores, so if you wish to find where your favorite pets fit in, look for Canis lupus and Felis sylvestris in it.

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12-08-2002, 05:18 PM	#4
Doubting Didymus Veteran Member Join Date: Jul 2002 Location: East Coast. Australia. Posts: 5,455	It used to be thought that Creodonts were ancestral to carnivoria (the group that includes dogs and cats, but also bears, seals etc). This is one, from the early tertiary: It's about the size of a mongoose, apparently. Nowadays the creodonts are though to be an extinct branch that lived alongside the real carnivoria ancestors.

12-08-2002, 07:09 PM	#6
RufusAtticus Veteran Member Join Date: Nov 2001 Location: NCSU Posts: 5,853	Remember that all these fossils are not necessarily the common ancestor species between cats and dogs, but rather closely related and probably representative of the actual one.

12-09-2002, 03:57 AM	#8
lpetrich Contributor Join Date: Jul 2000 Location: Lebanon, OR, USA Posts: 16,829	If one wants to be precise, the ancestor desired is Last Common Ancestor or Youngest Common Ancestor And as mentioned hear, it's likely some miacid or miacid-like Eocene carnivore.

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