Hello again,
thank you for this very detalied evaluation. Great! If the specimen is thus so rare, I could, if you and other colleagues are interested, post some more pictures, other views, close photographies, on the BoneCommons site. Or perhaps also photos in higher defintion? Would there be an interest for?
Best,
Chris
-------- Original-Nachricht --------
> Datum: Wed, 6 Apr 2011 13:08:39 +0100
> Von: Leif Jonsson <[log in to unmask]>
> An: [log in to unmask], "Christopher M. Götz" <[log in to unmask]>
> Betreff: Re: need help with a skull and another strange specimen\'s id
> 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
>
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