An adult Polycotylus latippinus, one of the giant, carnivorous, four-flippered reptiles known as plesiosaurs that lived during the Mesozoic Era, is shown giving birth in this publicity illustration released to Reuters August 12, 2011. A paper published in the journal Science Friday states that a fossil of the creature on display in Los Angeles with bones in its abdomen are evidence of a fetus, and that this species produced offspring through live birth. REUTERS/Stephanie Abramowicz/Natural History Museum of Los Angeles/Handout less
with pics of the fossil on the other side of the link.
pretty damn cool.
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Wasn't there also evidence of Icthysaurus giving birth?
This isn't unprecedented. Even sea snakes give birth, because the problems of marine lifeforms having to crawl up to beaches where they are vulnerable to lay eggs are obvious.
Shouldn't the head come out first? How does marine reptile birth work, anyway? Do sea snakes give birth head first?
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I think the Icthysaurus fossil had the same problem.
pregnant or post snack?
I think it's reasonably good evidence - as you said, it's not unprecedented.
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Since live birth probably evolved independently in plesiosaurs, separately from how it evolved in mammals, who knows? That's going to be practically impossible to figure out.
Whales are born tail first for the same reason, so the baby doesn't drown before it can finish being born.
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I see, interesting. Won't the flippers/fins/tail make it harder to pass through the birth canal? I guess that beats drowning. In humans, foot-first births are difficult.
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While the flippers might be a problem, the mother is pushing out the smallest end first. Unlike a human, who is pushing the Biggest End first.
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Pretty much anything air breathing that gives live birth in the sea will be born tail first. That seems to apply regardless of mammal or reptile.
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For some reason I want to say that the fins and flukes of newborn whales are soft, or at least not fully rigid, at birth and it takes a short span of time (minutes) after birth until they are stiff enough for them to be really useful. I can't seem to find any info on it though.
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Isn't it the nurse shark that gives birth to single live offspring, each constantly eats other eggs and newly hatched young after hatching internally? Might be a different shark, but either way this seems like a plausible means for the bigger sea monsters to have reproduced.
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Sea Skimmer wrote:Isn't it the nurse shark that gives birth to single live offspring, each constantly eats other eggs and newly hatched young after hatching internally? Might be a different shark, but either way this seems like a plausible means for the bigger sea monsters to have reproduced.
Most sharks are ovoviviparous. They are mostly nurtured by the yolk, but have been known to eat their siblings, yes. Though, that is not limited to nurse sharks and I would even go so far as to say that nurse shark pups are less likely to be sibling killers since they are bottom dwellers with a less pronounced mandibular arch and a relatively placid attitude.
He meant sand tiger sharks. The ones where scientists stuck endoscopes into their wombs and saw intrauterine cannibalism!
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Sea Skimmer wrote:Isn't it the nurse shark that gives birth to single live offspring, each constantly eats other eggs and newly hatched young after hatching internally? Might be a different shark, but either way this seems like a plausible means for the bigger sea monsters to have reproduced.
Most sharks are ovoviviparous. They are mostly nurtured by the yolk, but have been known to eat their siblings, yes. Though, that is not limited to nurse sharks and I would even go so far as to say that nurse shark pups are less likely to be sibling killers since they are bottom dwellers with a less pronounced mandibular arch and a relatively placid attitude.
There are a number of sharks that do this though. The eggs hatch in utero, and lacking a placenta with yolk supplies dwindling, the first few to hatch will sometimes eat the others. Lemon sharks, I know in addition to "sand tigers" or "grey nurse" sharks (same species, up to 5 m long fish eaters) do this.
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Sea Skimmer wrote:Isn't it the nurse shark that gives birth to single live offspring, each constantly eats other eggs and newly hatched young after hatching internally? Might be a different shark, but either way this seems like a plausible means for the bigger sea monsters to have reproduced.
Most sharks are ovoviviparous. They are mostly nurtured by the yolk, but have been known to eat their siblings, yes. Though, that is not limited to nurse sharks and I would even go so far as to say that nurse shark pups are less likely to be sibling killers since they are bottom dwellers with a less pronounced mandibular arch and a relatively placid attitude.
There are a number of sharks that do this though. The eggs hatch in utero, and lacking a placenta with yolk supplies dwindling, the first few to hatch will sometimes eat the others. Lemon sharks, I know in addition to "sand tigers" or "grey nurse" sharks (same species, up to 5 m long fish eaters) do this.
Ah, I am unfamiliar with "grey nurse" as a local name for what I would call sand tigers. I suspect a number of sharks do this. Hell, it isn't beyond a mother to turn right around and eat one of her pups.
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