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The skinny on Apato versus Brontosaurus
The holotype of Apatosaurus ajax is very fragmentary, and is not really
diagnostic at the species or even genus level (have examined it at Yale).
Worse, nothing was articulated, and there were other specimens in the quarry,
the bones assigned to the holotype could belong to multiple individuals
(very possible) and even taxa (less likely but possible). It could therefore be
a chimeria that gives misleading taxonomic information. It's a very bad
The mounted Yale holotype of Brontosaurus excelsus is most of the skeleton
(the vertebrae are badly beat up, I suspect from incompetent excavation and
transport in the day before jacketing, and from chucking the naked bones
into straw filled wood boxes). It is an excellent holotype for a genus:-)
Also, A. ajax is from high in the Morrison, B. excelsus from the middle.
Probably 3 million years separating them. Assigning the latter to the same
genus as the former is correspondingly very dubious when the A. ajax type is so
poor. (Also mid Morrison A. or B. louisae is definitely the same genus but
probably not same species as B. or A. excelsus).
Riggs blew it at a time when the importance of high quality types etc was
not appreciated. He should have declared the A. ajax type inadequate and kept
Brontosaurus. Would have avoided the chronic name confusion, and kept the
popular name going.
I was thinking of doing so now. But that requires for the first time
actually describing the A. ajax type in proper detail to then sink it, and it
would be good to do the same for B. excelsus skeleton (should be done when it
dismantled during the hall redo).