Long and short-necked sloths of the Cambridge University Museum of Zoology
April 18, 2013
Back in 2010, SVPCA was held in Cambridge. (It was the year that I gave the “why giraffes have short necks” talk [abstract, slides].)
While we were there, I took a lot of photos in the excellent Cambridge University Museum of Zoology, which was just across the courtyard from the lecture theatre where the scientific sessions were held.
In light of the recent discussion here on how many cervical vertebrae giraffes have (spoiler: seven), I thought it would be good to air the sloth photos, since the two genera of sloths constitute 66% of all the mammals have that a cervical count other than seven. (The third is the manatee Trichechus, with six cervicals.)
Three-toed sloth, Bradypus tridactylus. This specimen has nine cervicals vertabrae, but apparently the count can vary between eight and ten in different individuals.
Three-toed sloth, Bradypus tridactylus, full skeleton.
Two-toed sloth, Choloepus didactylus. Six cervical vertebrae.
Two-toed sloth, Choloepus didactylus, full skeleton.
Sauropod Vertebra Picture of the Week 
April 18, 2013 at 11:55 am
” the two genera of sloths constitute 66% of all the mammals have that [ahem] a cervical count other than seven”
.. should be ” the two genera of sloths constitute 66% of all the >extant< mammals that have a cervical count other than seven", since there are extinct sloths and sirenians where the cervical count is also other than seven.
April 18, 2013 at 9:39 pm
Ah I was wondering about that.
Given the large number of extinct sloths I wondered if any of them had non-standard neck vertebrae numbers; or if only sloths living in an inverted position did.
What is the total range of vertebrae number in extinct sloths; do any of them have really extreme numbers of neck vertebrae?
And likewise how much do the numbers vary in extinct sirenians?
LeeB.
April 18, 2013 at 11:46 pm
(It was the year that I gave the “why giraffes have short necks” talk [abstract, slides].)
I believe you mean, [abstract, slides, preprint, paper].
April 19, 2013 at 6:47 am
Excellent point. At some stage I must do a post on the history of that paper. I think it would make a helpful case-study for people who are starting out.