Leif's point about collecting juveniles of all vertebrates is very well
taken. I have made an effort over the last several decades to obtain
carcasses of bird nestlings/fledglings, especially those taxa that are
endangered or difficult to obtain for the Zooarchaeology Lab (Peabody
Museum, Harvard) collections. Other equally important taxa to collect
are newborns or very young domesticated animals (pigs, calves, goats,
etc.) We have received requests to loan some of these otherwise
unattainable specimens to other researchers.
Tonya Largy, M.A., Preparator
Zooarchaeology Laboratory
Peabody Museum, Harvard University
11 Divinity Avenue
Cambridge, MA 02138
U.S.A.
Leif Jonsson wrote:
> Hello,
> once more some thoughts on the hippopotamus skull. From the good series of photos it is clear that it is a juvenile individual. The first permanent molar has erupted and come into occlusion but with hardly any wear. The second permanent molar is partly developed and deep inside its crypt. The decidous molars are all present. In the skull base the synchodrosis spheno-occipitalis has not occurred. The size of the skull indicates that it may be to small for a juvenile hippopotamus (Hippopotamus amphibius), but rather the size of a pygmy hippopotamus (Hexaprotodon liberiensis) of corresponding age. The length of the first upper molar seems to be around 30 mm. In a female hippopotamus in the collection of my museum that tooth is around 43 mm long (slightly shortened by wear distally). Thus pygmy hippopotamus must be the identity of your specimen.
> I guess there are very few juvenile specimens of pygmy hippopotamuses (and the larger hippopotamus) in osteological collections. This is a common condition in most museum collections of mammals. Juvenile individuals were occasionally collected, not regularily, so there is a lack of juveniles with decidous teeth in early wear. An exception is domestic mammals where there from early on was an interest in ageing methods.
> Measuring full-grown skull length and size of permanent teeth are convenient ways to estimate size of animals and to view variation in size geographically. So museum collections are full of skulls of adult specimens but few young. Many times I have had archaeological or other subfossil decidous teeth to identify and found that comparitive specimens were lacking. If the museum did not collect juvenile specimens to fill the gaps in the collection I did my own collections. Take a look in Hillson's excellent book on teeth (Cambridge Manuals in Archaeology) and you will find no decidous teeth except for domestic mammals and man. My guess is that is was too great a job to find decidous teeth of so many mammal families to include these in the volume. The lack of decidous mammal teeth in collections has made them less used by systematists even though decidous teeth have as good characters for phylogeny and taxonomy as permanent teeth.
> So, what I want to say is that we must be aware of the deficiencies present in many collections and try to encourage institutions to collect young animals (not just mammals, but all kinds of vertebrates and not just skulls but whole skeletons). Thank you Christopher Götz for sharing your photos of the hippo (with a scale) so that we can have an example of size and morphology of pygmy hippopotamus decidous teeth. (One of my students did a taphonomic study of dwarf hippopotamus from a Cyprus cave and we lacked modern decidous teeth)
>
> Leif Jonsson
> Gothenburg Museum of Natural History
>
>
|