Re: Good mother dinos

["Dan Lipkowitz" <lipkowit@midway.uchicago.edu>]

In message Fri, 4 Nov 1994 17:07:47 -0500,
  Tracy Monaghan <monaghan@cac.washington.edu>  writes:

>> >>> 1) How can you tell from fossilized bones whether any particular
>>   >>> species of dinosaur was a "good mother" or cared for its young?
>>
>>   >In the case of Maiasaura, there is evidence that when the young
>>   >hatched, their long bones weren't fully ossified, so the animals
>>    >couldn't support their own weight.  The obvious inference is that
>> food  >had to be brought to them until they outgrew that condition.
>>
>>   One complication of this bit was the presentation of Dave Unwin (U. of
>>    Bristol, UK) at the 1993 SVP.  He showed that, based on embryo-to-egg
>>  ratio  found in modern birds and reptiles, the Maiasaura "hatchlings"
>>  are actually  the proper size for a late-stage non-hatched embryo.  He
>>  did go on to point  out that this doesn't disprove parental care in the
>>  Dinosauria, but it does  take a way one previously important piece of
>> evidence.
>>
>
> I don't follow this last point.  Is the implication that the "hatchlings"
> were actually someone's snack-ling?  Or that Maiasaura may have only
> stuck around until the blessed moment, leaving the kids on their own
> after they hatched (hatch-key kids?)

If I recall correctly from one of Horner's lectures, another indication that the
Maiasaura cared for its young after hatching is the fact that eggshell
found in a hatched-out nest tends to be pulverized. In a nest from which
hatchlings immediately emerge and depart on their own, broken eggshell would
remain more-or-less intact; the extremely fragmented nature of the
discovered shells, therefore, suggests that hatchlings may have spent
considerable time lying and moving around atop their former
shells.

I know that there are other indications as well, but this one always struck
me as particularly interesting. I'll leave the others for other newsletter
members to answer, if they haven't already beaten me to this one... ;)

Dan Lipkowitz
lipkowit@midway.uchicago.edu