QUOTE(KCalypso @ May 16 2007, 12:14 AM) [snapback]1676875[/snapback]
I was wondering how many different sets of fossils have been discovered for the rarer types of dinosaurs. Eg. are there some types of dinosuars which only one set of fossils have been found? If so how do we know if it was a whole species? Could it have just been one creature?
This may be only a partial answer to your question but, sometimes finding only a portion of a skeleton can give you enough morphological information to discriminate between species.
Here are a couple of recent examples, the first is of a new "species" of horned dinosaur, the second is a new "genus".
QUOTE
Drumheller… A new species of horned dinosaur, found between 1992 and 2002 in a fossil bed in the
Alberta badlands, has been named Centrosaurus brinkmani (sen-troh-SORE-us BRINK-mun-eye) in
honour of Dr. Donald Brinkman, Head of Research at the Royal Tyrrell Museum.
The dinosaur was named by Dr. Michael J. Ryan, Curator and Head of the Department of Vertebrate
Palaeontology for the Cleveland Museum of Natural History. Ryan identified the new dinosaur while
working for the Royal Tyrrell Museum.
The naming of the dinosaur commemorates Brinkman’s
support of vertebrate palaeontology in Alberta and the student guidance he has provided.
Remains of the dinosaur were discovered in bone beds in southern Alberta, the largest of which is in
Dinosaur Provincial Park, a UNESCO World Heritage Site. Centrosaurus brinkmani is one of the few
new dinosaurs to be named from Alberta in recent decades, and the first new dinosaur to be named
based on complete skeletal material from Dinosaur Provincial Park since the 1970s.
As described in the July volume of the Canadian Journal of Earth Sciences, this new species is from the
Late Cretaceous and belongs to the group of dinosaurs related to the well-known Triceratops. This new
species lived about 76 million years ago, 10 million years earlier than the Triceratops.
Horned (Ceratopsian) dinosaurs can be distinguished from one another by the frills that ornament their
skulls. Distinctive hooks and ‘spikelets’ on the frill of Centrosaurus brinkmani allowed scientists to
identify this dinosaur as a new species.
source:
http://www.tyrrellmuseum.com/press/Centrosaurus.pdfQUOTE
Albertaceratops nesmoi is a centrosaurine ceratopsid from the lower Oldman Formation (Upper Cretaceous) and is based on a single, almost complete skull collected from the Pinhorn Grazing Reserve of southern Alberta. It has a low, thick, elongate nasal ornamentation, long Triceratops-like brow horns, and a pair of wide-based, large, thickened curled processes originating from the caudolateral margin of the frill. The unfused, adult-sized nasal horncores of Albertaceratops (broken in the holotype) closely resemble the small, juvenile, unfused, nasal horncores of Pachyrhinosaurus but they are tenfold larger.
Referred material comes from equivalent beds in the Judith River Formation of northcentral Montana. A limited phylogenetic analysis of the Ceratopsidae places the new taxon as the basal member of the Centrosaurinae and indicates that robust, elongate postorbital horncores that form a synapomorphy of (Ceratopsidae + Zuniceratops) are also present in Centrosaurinae.
Source:
http://www.digitaldreammachine.com/sadrg/d...taceratops.htmlIn both these cases they are using skull material to classify the specimens, but in other dinosaurs the diagnostic features may exist elsewhere on the skeleton, so finding a partial vertebral column from one animal may not be enough to tell you what species it is, but it may point to a "family" or higher taxon.