# There are two mammals that lay eggs? **URL:** \ **Category:** Factual Questions\ **Created:** [March 30, 2008, 1:51am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233 "2008-03-30T01:51:34Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Ruby](https://avatars.discourse-cdn.com/v4/letter/r/13edae/32.png) [@Ruby](https://boards.straightdope.com/u/Ruby)\ **Post date:** [March 30, 2008, 1:51am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/1 "2008-03-30T01:51:34Z")
Just watching NatGeo and the narrator said the platypus was one of TWO mammals on earth thay lays eggs. Two? What’s the other one? ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [March 30, 2008, 1:54am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/2 "2008-03-30T01:54:39Z")
Echidna. ---
**Author:** ![DSYoungEsq](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)\ **Post date:** [March 30, 2008, 1:54am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/3 "2008-03-30T01:54:51Z")
[QUOTE=Ruby] Just watching NatGeo and the narrator said the platypus was one of TWO mammals on earth thay lays eggs. Two? What’s the other one? [/QUOTE] [Wikipedia is your friend.](http://en.wikipedia.org/wiki/Monotreme) ---
**Author:** ![blondebear](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blondebear/32/1022_2.png) [@blondebear](https://boards.straightdope.com/u/blondebear)\ **Post date:** [March 30, 2008, 1:55am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/4 "2008-03-30T01:55:22Z")
And cute little fellows they are! ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [March 30, 2008, 1:58am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/5 "2008-03-30T01:58:42Z")
Echidna facts: [ul][li]A young echidna is called a puggle.[/li]Male echidnas have four-headed penises.[/ul] ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [March 30, 2008, 2:06am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/6 "2008-03-30T02:06:42Z")
[QUOTE=Ruby] Just watching NatGeo and the narrator said the platypus was one of TWO mammals on earth thay lays eggs. [/QUOTE] The narrator was wrong. The platypus lays eggs, as do all five species of echidna. So there are in fact 6 mammals on Earth that lay eggs. The 5 echidna species belong to either 2 or 3 separate genera, so saying that there are only two mammals that lay eggs is like saying that there are only two mammals that can fly. ---
**Author:** ![Zsofia](https://avatars.discourse-cdn.com/v4/letter/z/7bcc69/32.png) [@Zsofia](https://boards.straightdope.com/u/Zsofia)\ **Post date:** [March 30, 2008, 2:12am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/7 "2008-03-30T02:12:38Z")
[QUOTE=Johnny L.A.] Echidna facts: [ul][li]A young echidna is called a puggle.[/li][li]Male echidnas have four-headed penises.[/ul][/li][/QUOTE] How does that work? The penis thing, I mean. Does the female echidna have a four-chambered, er, you know? ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [March 30, 2008, 2:15am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/8 "2008-03-30T02:15:44Z")
[QUOTE=Zsofia] How does that work? The penis thing, I mean. Does the female echidna have a four-chambered, er, you know? [/QUOTE] From [Wiki](http://en.wikipedia.org/wiki/Echidna): > [@](#): > > The echidnas have a four-headed penis, but only two of the heads are used during mating. The other two heads “shut down” and do not grow in size. The heads used are swapped each time the mammal has sex. I guess it’s sort of like a Gatling-penis. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [March 30, 2008, 2:18am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/9 "2008-03-30T02:18:44Z")
[QUOTE=Johnny L.A.] Gatling-penis. [/QUOTE] Band name! ---
**Author:** ![Ruby](https://avatars.discourse-cdn.com/v4/letter/r/13edae/32.png) [@Ruby](https://boards.straightdope.com/u/Ruby)\ **Post date:** [March 30, 2008, 2:44am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/10 "2008-03-30T02:44:51Z")
Thanks, you guys are good! ---
**Author:** ![jayjay](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jayjay/32/6765_2.png) [@jayjay](https://boards.straightdope.com/u/jayjay)\ **Post date:** [March 30, 2008, 2:49am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/11 "2008-03-30T02:49:11Z")
Okay, more on the 4-headed penis… There is a video on [this page](http://scienceblogs.com/neurophilosophy/2007/10/experimenting_with_a_fourheaded_penis.php) that shows it at about 14 seconds in. It freaking looks like a montremal version of the John Hirt messhall scene in _Alien_… ---
**Author:** ![Silver\_Tyger](https://avatars.discourse-cdn.com/v4/letter/s/fbc32d/32.png) [@Silver\_Tyger](https://boards.straightdope.com/u/Silver_Tyger)\ **Post date:** [March 30, 2008, 3:09am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/12 "2008-03-30T03:09:47Z")
I can deal with the platypus laying eggs. But the thing is _venomous_! That’s just screwed up. (And I’ve seen pictures of an echidna penis. It’s _weird_) ---
**Author:** ![blondebear](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/blondebear/32/1022_2.png) [@blondebear](https://boards.straightdope.com/u/blondebear)\ **Post date:** [March 30, 2008, 3:10am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/13 "2008-03-30T03:10:06Z")
[QUOTE=blondebear] And cute little fellows they are! [/QUOTE] Disclaimer: I was referring to the animal as a whole, not any particular individual piece-parts. ---
**Author:** ![Ruby](https://avatars.discourse-cdn.com/v4/letter/r/13edae/32.png) [@Ruby](https://boards.straightdope.com/u/Ruby)\ **Post date:** [March 30, 2008, 3:13am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/14 "2008-03-30T03:13:09Z")
[QUOTE=jayjay] Okay, more on the 4-headed penis… There is a video on [this page](http://scienceblogs.com/neurophilosophy/2007/10/experimenting_with_a_fourheaded_penis.php) that shows it at about 14 seconds in. It freaking looks like a montremal version of the John Hirt messhall scene in _Alien_… [/QUOTE] I’m glad THAT thing didn’t find it’s way into MY evolutionary trail. :eek: ---
**Author:** ![MoodIndigo1](https://avatars.discourse-cdn.com/v4/letter/m/e8c25b/32.png) [@MoodIndigo1](https://boards.straightdope.com/u/MoodIndigo1)\ **Post date:** [March 30, 2008, 3:21am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/15 "2008-03-30T03:21:32Z")
Apologies. For some reason, only the first post came up on my monitor. Question already answered. ---
**Author:** ![Giles](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/giles/32/60_2.png) [@Giles](https://boards.straightdope.com/u/Giles)\ **Post date:** [March 30, 2008, 3:35am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/16 "2008-03-30T03:35:30Z")
[QUOTE=Silver Tyger Girl] I can deal with the platypus laying eggs. But the thing is _venomous_! That’s just screwed up. [/QUOTE] Both the platypus and the echidnas are venomous, but that doesn’t make them dangerous. As far as I know, they don’t have any way of delivering their venom to humans. And I will add that I’ve patted an echidna. Those spikes look sharp, but are actually blunt on the end. Another echidna that I saw in the wild, while driving on a back road in Tasmania, decided to try to hide from us by digging a hole in the road. It was a dirt road, but still – it would have been easier for it to escape fro us by just walking off to the side of the road and hiding in the bushes, since it didn’t manage to dig very far down! ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [March 30, 2008, 3:40am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/17 "2008-03-30T03:40:11Z")
[QUOTE=Giles] Both the platypus and the echidnas are venomous, but that doesn’t make them dangerous. As far as I know, they don’t have any way of delivering their venom to humans. … [/QUOTE] The platypus definitely can - the males have a poson spur on the hind leg. Reportedly, it’s nasty stuff. The wiki article claims: > [@](#): > > Although powerful enough to kill smaller animals,[2] the venom is not lethal to humans. However, it produces excruciating pain which may be intense enough to incapacitate the victim. Swelling rapidly develops around the entry wound and gradually spreads outwards. Information obtained from case studies shows that the pain develops into a long-lasting hyperalgesia that can persist for months but usually lasts from a few days to a few weeks.[3][4] A clinical report from 1992 showed that the severe pain was persistent and did not respond to morphine. There have been no reported human fatalities.[3] That’s consistent with what I’ve heard before. ---
**Author:** ![kitemaker\_chuck](https://avatars.discourse-cdn.com/v4/letter/k/a88e4f/32.png) [@kitemaker\_chuck](https://boards.straightdope.com/u/kitemaker_chuck)\ **Post date:** [March 30, 2008, 3:43am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/18 "2008-03-30T03:43:31Z")
Are there any other egg-laying mammals (besides the platypus and echidna) thought to have existed at any other times in Earth’s history? Is there any way for science to determine (from fossil eveidence) that a mammal was an egg-layer? ---
**Author:** ![jayjay](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jayjay/32/6765_2.png) [@jayjay](https://boards.straightdope.com/u/jayjay)\ **Post date:** [March 30, 2008, 3:53am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/19 "2008-03-30T03:53:49Z")
[QUOTE=kitemaker\_chuck] Are there any other egg-laying mammals (besides the platypus and echidna) thought to have existed at any other times in Earth’s history? Is there any way for science to determine (from fossil eveidence) that a mammal was an egg-layer? [/QUOTE] The [therapsids](http://en.wikipedia.org/wiki/Therapsid) layed eggs. Therapsids aren’t mammals, per se, but are direct mammalian ancestors who had a LOT of mammalian characteristics (fur, differentiated teeth, mammalian-type jaws) but still laid eggs. Also, the wikipedia article on [monotremes](http://en.wikipedia.org/wiki/Monotremes) has a listing of monotremes known only through fossils at the end of the article. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [March 30, 2008, 4:37am UTC](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233/20 "2008-03-30T04:37:30Z")
[QUOTE=Johnny L.A.] Echidna facts: [ul][li]A young echidna is called a puggle.[/li][li]Male echidnas have four-headed penises.[/ul][/li][/QUOTE] And what sort of penises do female echidnas have? [Next page](https://boards.straightdope.com/t/there-are-two-mammals-that-lay-eggs/443233.md?page=2)