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Re: Segregated vs age-mixed sauropod herds

There is a real quandry here, because on the one hand there are
theoretical arguments (actually watching out for the little ones; need to
move a lot) and observations (lack of tiny and giant sauropods found
together), but in opposition there are phylogenetic arguments (parental
care for at least several weeks is present in crocs and birds, and hence
in Archosauria ancestrally) and taphonomic arguments (sedimentary systems
are highly unlikely to simultaneous preserve large sauropod bones and tiny
baby ones in the same depositional settings; adult sauropods would make
tracks on substrates that baby sauropods - or you and I - could not; etc.)

And for a third hand, the Varricchio et al. argument exists that perhaps
parents stayed with offspring during the hatching season, but multi-clutch
family gatherings lacking the newborns and the adults wandered together
(suggested by Sinornithosaurus and Psittacosaurus finds).

Personally I think the claims of segregated sauropod herds have to be
tested for taphonomic size filtering.

The trackways in question do show subadults and adults together, but to my
knowledge no reports of 1-3 m long babies found with adults.

David Krentz wrote:
>  From what I've been reading, there seems to be a good amount of
> evidence for segregated sauropod herds, but not as much for mixed
> age.  If there were mixed age groups, would the youngsters have been
> cared for at birth until they were older as some accounts suggest?
> That seems silly to me, as the food requirements for sauropods would
> cause the herd to constantly keep moving, and all those little feet
> would surly slow the faster moving adults.  Or, would the lighter
> juveniles be able to keep up with the weightier adults?  I recall
> reading that there are sauropod trackways with juveniles in tow to
> support the mixed theory, but are there bone beds too?
>   I suppose that there were many different strategies that were
> employed by the many sauropod species, just like the many kinds of
> child rearing/abandoning behavior in crocs and turtles.

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Fax: 301-314-9661

Faculty Director, Earth, Life & Time Program, College Park Scholars
Faculty Director, Science & Global Change Program, College Park Scholars
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA